WO2024065588A1 - 变换器及其控制方法 - Google Patents

变换器及其控制方法 Download PDF

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Publication number
WO2024065588A1
WO2024065588A1 PCT/CN2022/123041 CN2022123041W WO2024065588A1 WO 2024065588 A1 WO2024065588 A1 WO 2024065588A1 CN 2022123041 W CN2022123041 W CN 2022123041W WO 2024065588 A1 WO2024065588 A1 WO 2024065588A1
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Prior art keywords
converter
current
switch tube
peak value
switching
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PCT/CN2022/123041
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English (en)
French (fr)
Inventor
陈建
戴宝磊
汪波
康良云
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华为数字能源技术有限公司
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Priority to PCT/CN2022/123041 priority Critical patent/WO2024065588A1/zh
Publication of WO2024065588A1 publication Critical patent/WO2024065588A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only

Definitions

  • the present application relates to the technical field of power supply, and in particular to a converter and a control method thereof.
  • asymmetric half-bridge (AHB) converters usually use pulse width modulation (PWM), pulse frequency modulation (PFM), burst modulation (Burst-Mode) or a combination of the above three modes.
  • PWM mode is to fix the switching frequency of the converter and adjust the output voltage by controlling the excitation current, etc.
  • PFM mode adjusts the output voltage by changing the switching frequency
  • Burst-Mode adjusts the output voltage by controlling whether the converter performs switching actions.
  • the AHB converter mainly controls the working mode of the AHB converter based on the input voltage and load of the AHB converter. Specifically, when the load of the AHB converter is greater than or equal to the first load setting value corresponding to the input voltage of the AHB converter, the AHB converter operates in an asymmetric half-bridge flyback mode with a fixed switching frequency, wherein the higher the input voltage of the AHB converter, the greater the first load setting value; when the above load is less than the first load setting value and greater than the second load setting value, the AHB converter operates in a clamped asymmetric half-bridge flyback mode, and the switching frequency of the AHB converter decreases linearly as the load decreases; when the above load is less than the second load setting value, the AHB converter operates in an intermittent wave mode.
  • the mode switching point in the above control method is only related to the input voltage and the load, when the AHB converter needs to output a wide range, the mode switching point of the above control method for all output voltages is the same, which will lead to low efficiency of the AHB converter under some output voltages.
  • the present application provides a converter and a control method thereof, which can optimize the efficiency of the converter under a full range of output voltages.
  • the present application provides a converter, which includes a main switch tube, an auxiliary switch tube, a transformer and a controller.
  • the main switch tube and the auxiliary switch tube are connected in series between the input end and the reference ground of the converter, the input end of the transformer is respectively connected to the two ends of the auxiliary switch tube, and the output end of the transformer is connected to the output end of the converter.
  • the controller obtains the output voltage of the converter, and obtains the mode switching parameter based on the output voltage of the converter; the converter is controlled to switch between the first working mode and the second working mode according to the mode switching parameter, wherein the magnitude of the switching frequency of the converter in the first working mode is negatively correlated with the magnitude of the output current of the converter, and the switching frequency of the converter in the second working mode remains unchanged within one working cycle of the converter.
  • the converter Since the switching loss of the converter (such as the AHB converter) is often strongly correlated with the output voltage, the converter provided in the present application can adjust the mode switching parameters of its own switching between different working modes according to different output voltages, that is, the converter adjusts its own working mode according to different output voltages, or the converter adjusts its own working parameters from the first working mode to the second working mode to reduce the switching loss, so that the efficiency of the converter under the full range of output voltages can be optimized.
  • the converter adjusts its own working mode according to different output voltages, or the converter adjusts its own working parameters from the first working mode to the second working mode to reduce the switching loss, so that the efficiency of the converter under the full range of output voltages can be optimized.
  • the mode switching parameter is a first current threshold.
  • the controller compares the output current of the converter with the first switching current threshold, and controls the converter to switch between the first working mode and the second working mode according to the comparison result.
  • the converter provided in the present application can adjust the mode switching point (i.e., the first switching current threshold) at which it switches between different working modes according to different output voltages, that is, the converter adjusts its own working mode according to different output voltages to reduce switching losses, thereby optimizing the efficiency of the converter under the full range of output voltages.
  • the controller obtains the first voltage interval where the output voltage is located from multiple voltage intervals based on the output voltage, and obtains the first switching current threshold corresponding to the first voltage interval from multiple switching current thresholds corresponding to the voltage interval, wherein the multiple voltage intervals correspond to the multiple switching current thresholds one-to-one.
  • the higher the gear of the first voltage interval where the output voltage of the converter is located the larger the first switching current threshold corresponding to the first voltage interval, so that the switching frequency and operating frequency of the converter can be maintained in a relatively appropriate range, thereby avoiding the situation where the converter's switching frequency is too high, resulting in the converter's efficiency being too low, or avoiding the situation where the converter's switching frequency is too low, resulting in the converter's operating frequency entering audio noise.
  • the controller when the output current is less than or equal to the first switching current threshold and greater than the second switching current threshold, controls the main switch tube and the auxiliary switch tube to be turned on for the first number of times in one working cycle of the converter, so that the converter is in a high-frequency intermittent wave HBURST mode.
  • the controller also controls the main switch tube and the auxiliary switch tube to be turned on for the second number of times in one working cycle when the output current is less than or equal to the second switching current threshold, wherein the second number of times of turn-on is less than the first number of times of turn-on.
  • the converter when the converter is in the HBURST mode, the converter can adjust the number of times the switch tube is turned on in the above working cycle based on the change of the load (ie, the output current), ensure output on demand, avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and thus improving the efficiency of the converter.
  • the number of times the switch tube is turned on in the above working cycle is gradually reduced in the process of gradually becoming lighter (ie, the output current is gradually reduced), the output voltage ripple of the converter under light load conditions can also be reduced, and the applicability is strong.
  • the transformer includes an excitation inductor.
  • the controller controls the current peak value of the excitation inductor in one working cycle of the converter to be the first current peak value, so that the converter is in HBURST mode.
  • the controller also controls the current peak value of the excitation inductor in one working cycle to be the second current peak value when the output current is less than or equal to the second switching current threshold, wherein the second current peak value is less than the first current peak value.
  • the converter when the converter is in HBURST mode, the converter can adjust the current peak value of the excitation inductor in the above working cycle based on the change of the load, ensure on-demand output, avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and thus improving the efficiency of the converter.
  • the current peak value of the excitation inductor in the above working cycle is gradually reduced in the process of gradually becoming lighter, the output voltage ripple of the converter under light load conditions can also be reduced, and the applicability is strong.
  • the controller controls the main switch tube and the auxiliary switch tube to be turned on the third number of times in one working cycle of the converter, so that the converter is in HBURST mode.
  • the controller also controls the main switch tube and the auxiliary switch tube to be turned on the fourth number of times in one working cycle when the output current is less than or equal to the third switching current threshold, and after the first working cycle number of times in one working cycle is the third number of times, the controller controls the main switch tube and the auxiliary switch tube to be turned on the fifth number of times in one working cycle, so that the converter is in low-frequency intermittent wave LBURST mode, wherein the fourth number of times of turns on is less than or equal to the third number of times of turns on and greater than the fifth number of turns on.
  • the present embodiment optimizes the working mode of the converter under extremely light load conditions (i.e., the output current is less than or equal to the third switching current threshold), so that the converter is in the HBURST mode to further reduce the output energy, thereby not only reducing energy loss and switching tube loss to improve the efficiency of the converter, but also reducing the output voltage ripple of the converter under extremely light load conditions.
  • the transformer includes an excitation inductor.
  • the controller controls the current peak value of the excitation inductor in one working cycle of the converter to be the third current peak value, so that the converter is in HBURST mode.
  • the controller also controls the current peak value of the excitation inductor in one working cycle to be the fourth current peak value when the output current is less than or equal to the third switching current threshold, and after the first working cycle number of the current peak value in one working cycle is the third current peak value, controls the current peak value of the excitation inductor in one working cycle to be the fifth current peak value, so that the converter is in LBURST mode.
  • the fourth current peak value is less than or equal to the third current peak value and greater than the fifth current peak value.
  • this embodiment optimizes the working mode of the converter under extremely light load conditions, so that the converter is in LBURST mode, so that the output energy is further reduced, thereby not only reducing energy loss and switch tube loss to improve the efficiency of the converter, but also reducing the output voltage ripple of the converter under extremely light load conditions.
  • the controller controls the main switch tube and the auxiliary switch tube to be turned on a third number of times in a working cycle (i.e., a high-frequency intermittent cycle) of the converter, so that the converter is in the HBURST mode.
  • the controller also controls the main switch tube and the auxiliary switch tube to be turned on a fourth number of times in a working cycle after the main switch tube and the auxiliary switch tube are turned on a third number of times in a working cycle, if the operating frequency of the converter (i.e., the frequency of the high-frequency intermittent cycle) is within a preset frequency range, and after the first working cycle number of the fourth number of times of the turn-on times in a working cycle, the main switch tube and the auxiliary switch tube are controlled to be turned on a fifth number of times in a working cycle, wherein the fourth number of times of the turn-on times is less than or equal to the third number of times of the turn-on times and greater than the fifth number of times of the turn-on times.
  • the operating frequency of the converter i.e., the frequency of the high-frequency intermittent cycle
  • the main switch tube and the auxiliary switch tube are controlled to be turned on a third number of times in a working cycle. It can be understood that after the converter is in the HBURST mode, the present embodiment optimizes the working mode of the converter when the frequency of the high-frequency intermittent cycle is within the hearing range of the human ear, so that the converter is in the LBURST mode, thereby reducing energy loss and switch tube loss, thereby improving the efficiency of the converter. In addition, when the frequency of the high-frequency intermittent cycle is within the hearing range of the human ear, the converter is in the LBURST mode, which can effectively reduce the switching noise of the converter.
  • the transformer includes an excitation inductor.
  • the controller controls the current peak value of the excitation inductor in one working cycle of the converter to be the third current peak value, so that the converter is in HBURST mode.
  • the controller also controls the current peak value of the excitation inductor in one working cycle to be the fourth current peak value after the current peak value of the excitation inductor in one working cycle is the third current peak value, if the operating frequency of the converter is within a preset frequency range, and controls the current peak value of the excitation inductor in one working cycle to be the fifth current peak value after the first working cycle number of the current peak value in one working cycle is the fourth current peak value, wherein the fourth current peak value is greater than the fifth current peak value and less than or equal to the third current peak value. If the operating frequency of the converter is outside the preset frequency range, the current peak value of the excitation inductor in one working cycle is controlled to be the third current peak value.
  • the present embodiment optimizes the working mode of the converter when the frequency of the high-frequency intermittent cycle is within the hearing range of the human ear, so that the converter is in the LBURST mode, thereby reducing energy loss and switch tube loss, thereby improving the efficiency of the converter.
  • the converter is in the LBURST mode, which can effectively reduce the switching noise of the converter.
  • the controller controls the switching frequency of the converter to be the first switching frequency and the second switching frequency, wherein when the first output current is greater than the second output current, the first switching frequency is less than the second switching frequency.
  • the first operating mode includes a continuous resonance current flyback mode (continuous resonance mode, CRM), and the second operating mode includes an intermittent wave generation mode.
  • the controller controls the converter to operate in the CRM; or, when the output current is less than or equal to the first switching current threshold, the controller controls the converter to operate in the intermittent wave generation mode.
  • the mode switching parameter is the first operating parameter of the converter in the second operating mode.
  • the controller also obtains the switching frequency of the converter; when the switching frequency reaches the frequency threshold, the first operating parameter of the converter in the second operating mode is obtained according to the output voltage; based on the first operating parameter, the converter is controlled to switch from the first operating mode to the second operating mode, wherein the first operating parameter includes the number of times the main switch tube and the auxiliary switch tube are turned on in one operating cycle of the converter, or the current peak value of the excitation inductance in one operating cycle.
  • the converter provided in the present application can adjust its operating parameters from the first operating mode to the second operating mode according to different output voltages to reduce the switching frequency and switching loss of the converter, thereby optimizing the efficiency of the converter under the full range of output voltages.
  • the controller when the switching frequency reaches a frequency threshold, the controller obtains a first voltage interval where the output voltage is located from a plurality of voltage intervals; and obtains a first operating parameter corresponding to the first voltage interval from a plurality of operating parameters corresponding to the plurality of voltage intervals, wherein the plurality of voltage intervals correspond one-to-one to the plurality of operating parameters.
  • the multiple voltage intervals also include a second voltage interval, and when any value in the second voltage interval is less than any value in the first voltage interval, the second operating parameter corresponding to the second voltage interval is less than the first operating parameter.
  • the first voltage interval and the second voltage interval are respectively a high voltage interval and a medium voltage interval.
  • the HBURST mode entry point (i.e., the second operating parameter) of the converter when the output voltage is in the medium voltage interval of the present application is reduced compared to the HBURST mode entry point (i.e., the first operating parameter) of the converter when the output voltage is in the high voltage interval, therefore, compared to using the same HBURST mode entry point for different output voltages, the HBURST mode entry point of the present application when the output voltage is in the medium voltage interval is smaller, which can reduce the energy transmitted in each high-frequency intermittent cycle, thereby reducing the primary and secondary winding losses and the switch tube conduction losses, thereby improving the efficiency of the converter in the HBURST mode.
  • the first operating parameter includes the number of conduction times, and the number of conduction times is the first number of conduction times.
  • the controller controls the number of conduction times of the main switch tube and the auxiliary switch tube in a working cycle to be the first number of conduction times, so that the converter switches to the HBURST mode.
  • the number of conduction times of the main switch tube and the auxiliary switch tube in a working cycle is the first number of conduction times
  • the number of conduction times of the main switch tube and the auxiliary switch tube in a working cycle is controlled to be the second number of conduction times, wherein the second number of conduction times is less than the first number of conduction times
  • the output current of the converter is greater than the second switching current threshold and less than or equal to the first switching current threshold
  • the number of conduction times of the main switch tube and the auxiliary switch tube in a working cycle is controlled to be the first number of conduction times.
  • the converter can adjust the number of conduction times of the switch tube in a high-frequency intermittent cycle based on the change of the load, ensure output on demand, avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and thus improving the efficiency of the converter.
  • the number of times the switch tube is turned on in a high-frequency intermittent cycle gradually decreases. Therefore, the output voltage ripple of the converter under light load conditions can also be reduced, and the applicability is strong.
  • the first switching parameter includes a current peak value
  • the current peak value is a first current peak value.
  • the controller controls the current peak value of the excitation inductance in one working cycle to be the first current peak value, so that the converter switches to the HBURST mode.
  • the current peak value of the excitation inductance in one working cycle is the first current peak value
  • the current peak value of the excitation inductance in one working cycle is controlled to be the second current peak value, wherein the second current peak value is less than the first current peak value
  • the output current of the converter is greater than the second switching current threshold value and less than or equal to the first switching current threshold value
  • the current peak value of the excitation inductance in one working cycle is controlled to be the first current peak value.
  • the converter can adjust the current peak value of the excitation inductance in a high-frequency intermittent cycle based on the change of the load, ensure output on demand, avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and thus improving the efficiency of the converter.
  • the current peak value of the excitation inductance in a high-frequency intermittent cycle also gradually decreases. Therefore, the output voltage ripple of the converter under light load conditions can also be reduced, and the applicability is strong.
  • the first switching parameter includes a conduction number
  • the conduction number is a third conduction number.
  • the controller controls the conduction number of the main switch tube and the auxiliary switch tube in a working cycle to be the third conduction number, so that the converter switches to the HBURST mode.
  • the conduction number of the main switch tube and the auxiliary switch tube in a working cycle is controlled to be the fourth conduction number
  • the conduction number of the main switch tube and the auxiliary switch tube in a working cycle is controlled to be the fifth conduction number, so that the converter switches to the LBURST mode, wherein the fourth conduction number is less than or equal to the third conduction number and greater than the fifth conduction number; if the output current of the converter is greater than the third switching current threshold and less than or equal to the first switching current threshold, the conduction number of the main switch tube and the auxiliary switch tube in a working cycle is controlled to be the third conduction number.
  • the working mode of the converter under extremely light load i.e., the output current is less than or equal to the third switching current threshold
  • the working mode of the converter under extremely light load is further optimized in this implementation method, so that the converter is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter.
  • the output energy is further reduced. Therefore, this implementation method can further reduce the output voltage ripple of the converter under extremely light load conditions, and is more applicable.
  • the first switching parameter includes a current peak value
  • the current peak value is a third current peak value.
  • the controller controls the current peak value of the excitation inductance in one working cycle to be the third current peak value, so that the converter switches to the HBURST mode.
  • the current peak value of the excitation inductance in one working cycle is controlled to be the fourth current peak value
  • the current peak value of the excitation inductance in one working cycle is controlled to be the fifth current peak value, so that the converter switches to the LBURST mode, wherein the fourth current peak value is less than or equal to the third current peak value and greater than the fifth current peak value; if the output current of the converter is greater than the third switching current threshold value and less than or equal to the first switching current threshold value, the current peak value of the excitation inductance in one working cycle is controlled to be the third current peak value.
  • the working mode of the converter under extremely light load conditions is further optimized in this implementation method, so that the converter is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter. Furthermore, since the converter is in the LBURST mode under extremely light load conditions, the output energy is further reduced. Therefore, this embodiment can further reduce the output voltage ripple of the converter under extremely light load conditions, and has stronger applicability.
  • the first switching parameter includes a conduction number
  • the conduction number is a third conduction number.
  • the controller controls the conduction number of the main switch tube and the auxiliary switch tube in one working cycle to be the third conduction number, so that the converter switches to the HBURST mode.
  • the conduction number of the main switch tube and the auxiliary switch tube in one working cycle is controlled to be the fourth conduction number
  • the conduction number of the main switch tube and the auxiliary switch tube in one working cycle is controlled to be the fifth conduction number, so that the converter switches to the LBURST mode, wherein the fourth conduction number is less than or equal to the first conduction number and greater than the fifth conduction number; if the operating frequency of the converter is outside the preset frequency range, the conduction number of the main switch tube and the auxiliary switch tube in one working cycle is controlled to be the third conduction number.
  • the working mode of the converter when the frequency of the high-frequency intermittent cycle is within the hearing range of the human ear is further optimized in this implementation method, so that the converter is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter.
  • the converter is in the LBURST mode, which can effectively reduce the switching noise of the converter.
  • the first switching parameter includes a current peak value
  • the current peak value is a third current peak value.
  • the controller controls the current peak value of the excitation inductance in one working cycle to be the third current peak value, so that the converter switches to the HBURST mode.
  • the current peak value of the excitation inductance in one working cycle is controlled to be the fourth current peak value
  • the current peak value of the excitation inductance in one working cycle is controlled to be the fifth current peak value, so that the converter switches to the LBURST mode, wherein the fourth current peak value is greater than the fifth current peak value and less than or equal to the first current peak value; if the operating frequency of the converter is outside the preset frequency range, the current peak value of the excitation inductance in one working cycle is controlled to be the third current peak value.
  • the working mode of the converter when the frequency of the high-frequency intermittent cycle is within the hearing range of the human ear is further optimized in this implementation method, so that the converter is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter.
  • the converter is in the LBURST mode, which can effectively reduce the switching noise of the converter.
  • the first operating mode includes CRM
  • the second operating mode includes an intermittent wave mode
  • the duty cycle is determined by the number of times the main switch tube and the auxiliary switch tube are turned on in one duty cycle.
  • the duty cycle is determined by the current peak value of the excitation inductance in one duty cycle.
  • the transformer in combination with any one of the first aspect to the twenty-second possible implementation of the first aspect, in a twenty-third possible implementation, includes a primary winding, a secondary winding, an excitation inductor, a resonant inductor and a resonant capacitor, the input end of the transformer includes a first input end and a second input end, and the output end of the transformer includes a first output end and a second output end.
  • the primary winding is connected in parallel with the excitation inductor; one end of the resonant inductor is connected to the first input end of the transformer, the other end of the resonant inductor is connected to the input end of the converter or the same-name end of the primary winding, the opposite-name end of the primary winding is connected to the second input end of the transformer through the resonant capacitor, and the opposite-name end and the same-name end of the secondary winding are respectively connected to the first output end and the second output end of the transformer.
  • the converter further includes a voltage sampling circuit, which is connected in parallel to both ends of the resonant capacitor for collecting the voltage of the resonant capacitor.
  • the controller obtains the voltage of the resonant capacitor, and obtains the output voltage of the converter based on the turns ratio of the secondary winding to the primary winding and the voltage of the resonant capacitor. It can be understood that the converter can obtain the output voltage of the converter through the voltage of the resonant capacitor collected by the voltage sampling circuit, and the output voltage acquisition method is simple and easy to control.
  • the transformer further includes an auxiliary winding
  • the converter further includes a voltage sampling circuit, which is connected in parallel to both ends of the auxiliary winding for collecting the voltage of the auxiliary winding.
  • the controller obtains the voltage of the auxiliary winding, and obtains the output voltage of the converter based on the turns ratio of the secondary winding to the auxiliary winding and the voltage of the auxiliary winding. It can be understood that the converter can also obtain the output voltage of the converter through the voltage of the auxiliary winding collected by the voltage sampling circuit, and the output voltage acquisition method is diverse and flexible.
  • the present application provides a control method for a converter, the converter comprising a main switch tube, an auxiliary switch tube, a transformer and a controller.
  • the main switch tube and the auxiliary switch tube are connected in series between the input end of the converter and the reference ground, the input end of the transformer is respectively connected to the two ends of the auxiliary switch tube, and the output end of the transformer is connected to the output end of the converter.
  • the method includes: the converter obtains its own output voltage, and obtains a mode switching parameter based on the output voltage of the converter; the converter is controlled to switch between a first working mode and a second working mode according to the mode switching parameter, wherein the magnitude of the switching frequency of the converter in the first working mode is negatively correlated with the magnitude of the output current of the converter, and the switching frequency of the converter remains unchanged within one working cycle of the converter in the second working mode.
  • the mode switching parameter is a first switching current threshold.
  • the converter compares its own output current with the first switching current threshold, and controls the converter to switch between the first working mode and the second working mode according to the comparison result.
  • the converter obtains a first voltage interval in which the output voltage is located from multiple voltage intervals based on the output voltage, and obtains a first switching current threshold corresponding to the first voltage interval from multiple switching current thresholds corresponding to the voltage intervals, wherein the multiple voltage intervals correspond one-to-one to the multiple switching current thresholds.
  • a third possible implementation manner when the output current of the converter is less than or equal to the first switching current threshold and greater than the second switching current threshold, the main switch tube and the auxiliary switch tube are controlled to be turned on the first number of times in one working cycle of the converter, so that the converter is in the second working state. And when the output current is less than or equal to the second switching current threshold, the main switch tube and the auxiliary switch tube are controlled to be turned on the second number of times in one working cycle, wherein the second number of times of turns on is less than the first number of turns on.
  • the transformer includes an excitation inductor.
  • the current peak value of the excitation inductor in one working cycle of the converter is controlled to be the first current peak value, so that the converter is in the second working mode.
  • the current peak value of the excitation inductor in one working cycle is controlled to be the second current peak value, wherein the second current peak value is less than the first current peak value.
  • a fifth possible implementation manner when the output current of the converter is less than or equal to the first switching current threshold and greater than the third switching current threshold, the main switch tube and the auxiliary switch tube are controlled to be turned on the third number of times in one working cycle of the converter, so that the converter is in the second working mode.
  • the main switch tube and the auxiliary switch tube are controlled to be turned on the fourth number of times in one working cycle, and after the first working cycle number of times in which the turn-on times in one working cycle are the third number of times, the main switch tube and the auxiliary switch tube are controlled to be turned on the fifth number of times in one working cycle, so that the converter is in the LBURST mode, wherein the fourth number of times ...
  • the transformer includes an excitation inductor.
  • the current peak value of the excitation inductor in one working cycle of the converter is controlled to be the third current peak value.
  • the current peak value of the excitation inductor in one working cycle is controlled to be the fourth current peak value
  • the current peak value of the excitation inductor in one working cycle is controlled to be the fifth current peak value, wherein the fourth current peak value is less than or equal to the third current peak value and greater than the fifth current peak value.
  • a seventh possible implementation when the output current of the converter is less than or equal to the first switching current threshold, the main switch tube and the auxiliary switch tube are controlled to be turned on a third number of times in one working cycle of the converter.
  • the main switch tube and the auxiliary switch tube are turned on a third number of times in one working cycle
  • the main switch tube and the auxiliary switch tube are controlled to be turned on a fourth number of times in one working cycle
  • the main switch tube and the auxiliary switch tube are controlled to be turned on a fifth number of times in one working cycle, wherein the fourth number of turns on is less than or equal to the third number of turns on and greater than the fifth number of turns on. If the operating frequency of the converter is outside the preset frequency range, the main switch tube and the auxiliary switch tube are controlled to be turned on a third number of times in one working cycle.
  • the transformer includes an excitation inductor.
  • the current peak value of the excitation inductor in one working cycle of the converter is controlled to be a third current peak value.
  • the current peak value of the excitation inductor in one working cycle is controlled to be a fourth current peak value
  • the current peak value of the excitation inductor in one working cycle is controlled to be a fifth current peak value, wherein the fourth current peak value is greater than the fifth current peak value and less than or equal to the third current peak value. If the operating frequency of the converter is outside the preset frequency range, the current peak value of the excitation inductor in one working cycle is controlled to be the third current peak value.
  • the switching frequency of the converter when the output current of the converter is greater than the first switching current threshold, and when the output currents are the first output current and the second output current, respectively, the switching frequency of the converter is controlled to be the first switching frequency and the second switching frequency, wherein when the first output current is greater than the second output current, the first switching frequency is less than the second switching frequency.
  • the first operating mode includes CRM
  • the second operating mode includes an intermittent wave mode.
  • the converter When the output current of the converter is greater than the first switching current threshold, the converter is controlled to operate in CRM; or, when the output current is less than or equal to the first switching current threshold, the converter is controlled to operate in the intermittent wave mode.
  • the mode switching parameter is a first operating parameter of the converter in the second operating mode.
  • the converter further obtains a switching frequency of the converter; when the switching frequency reaches a frequency threshold, the first operating parameter of the converter in the second operating mode is obtained according to the output voltage; based on the first operating parameter, the converter is controlled to switch from the first operating mode to the second operating mode, wherein the first operating parameter includes the number of times the main switch tube and the auxiliary switch tube are turned on in one operating cycle of the converter, or the current peak value of the excitation inductance in one operating cycle.
  • a twelfth possible implementation manner when the switching frequency of the converter reaches a frequency threshold, obtains a first voltage interval where the output voltage is located from multiple voltage intervals; and obtains a first operating parameter corresponding to the first voltage interval from multiple operating parameters corresponding to the multiple voltage intervals, wherein the multiple voltage intervals correspond one-to-one to the multiple operating parameters.
  • the multiple voltage intervals also include a second voltage interval, and when any value in the second voltage interval is smaller than any value in the first voltage interval, the second operating parameter corresponding to the second voltage interval is smaller than the first operating parameter.
  • the first operating parameter includes the number of conduction times, and the number of conduction times is the first number of conduction times.
  • the converter controls the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle to be the first number of conduction times.
  • the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle is the first number of conduction times
  • the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle is controlled to be the second number of conduction times, wherein the second number of conduction times is less than the first number of conduction times
  • the output current of the converter is greater than the second switching current threshold and less than or equal to the first switching current threshold
  • the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle is controlled to be the first number of conduction times.
  • the first switching parameter includes a current peak value
  • the current peak value is a first current peak value.
  • the converter controls the current peak value of the excitation inductance in one working cycle to be the first current peak value.
  • the current peak value of the excitation inductance in one working cycle is the first current peak value
  • the current peak value of the excitation inductance in one working cycle is controlled to be the second current peak value, wherein the second current peak value is less than the first current peak value
  • the output current of the converter is greater than the second switching current threshold value and less than or equal to the first switching current threshold value
  • the current peak value of the excitation inductance in one working cycle is controlled to be the first current peak value.
  • the first switching parameter includes the number of conduction times, and the number of conduction times is the third number of conduction times.
  • the converter controls the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle to be the third number of conduction times.
  • the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle is controlled to be the fourth number of conduction times
  • the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle is controlled to be the fifth number of conduction times, wherein the fourth number of conduction times is less than or equal to the third number of conduction times and greater than the fifth number of conduction times; if the output current of the converter is greater than the third switching current threshold and less than or equal to the first switching current threshold, the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle is controlled to be the third number of conduction times.
  • the first switching parameter includes a current peak value
  • the current peak value is a third current peak value.
  • the converter controls the current peak value of the excitation inductance in one working cycle to be the third current peak value.
  • the current peak value of the excitation inductance in one working cycle is controlled to be the fourth current peak value
  • the current peak value of the excitation inductance in one working cycle is controlled to be the fifth current peak value, wherein the fourth current peak value is less than or equal to the third current peak value and greater than the fifth current peak value; if the output current of the converter is greater than the third switching current threshold value and less than or equal to the first switching current threshold value, the current peak value of the excitation inductance in one working cycle is controlled to be the third current peak value.
  • the first switching parameter includes the number of conduction times, and the number of conduction times is the third number of conduction times.
  • the converter controls the main switch tube and the auxiliary switch tube to be the third number of conduction times in one working cycle.
  • the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle are both the third number of conduction times
  • the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle are both the fourth number of conduction times
  • the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle are both the fifth number of conduction times, wherein the fourth number of conduction times is less than or equal to the first number of conduction times and greater than the fifth number of conduction times; if the operating frequency of the converter is outside the preset frequency range, the number of conduction times of the main switch tube and the auxiliary switch tube in one working cycle are both the third number of conduction times.
  • the first switching parameter includes a current peak value
  • the current peak value is a third current peak value.
  • the converter controls the current peak value of the excitation inductance in one working cycle to be the third current peak value.
  • the current peak value of the excitation inductance in one working cycle is controlled to be the fourth current peak value
  • the current peak value of the excitation inductance in one working cycle is controlled to be the fifth current peak value, wherein the fourth current peak value is greater than the fifth current peak value and less than or equal to the first current peak value; if the operating frequency of the converter is outside the preset frequency range, the current peak value of the excitation inductance in one working cycle is controlled to be the third current peak value.
  • the first operating mode includes CRM
  • the second operating mode includes an intermittent wave mode
  • the duty cycle is determined by the number of times the main switch tube and the auxiliary switch tube are turned on in one duty cycle.
  • the duty cycle is determined by the current peak value of the excitation inductance in one duty cycle.
  • the transformer in combination with any one of the second aspect to the twenty-second possible implementation of the second aspect, in a twenty-third possible implementation, includes a primary winding, a secondary winding, an excitation inductor, a resonant inductor and a resonant capacitor, the input end of the transformer includes a first input end and a second input end, and the output end of the transformer includes a first output end and a second output end.
  • the primary winding is connected in parallel with the excitation inductor; one end of the resonant inductor is connected to the first input end of the transformer, the other end of the resonant inductor is connected to the input end of the converter or the same-name end of the primary winding, the opposite-name end of the primary winding is connected to the second input end of the transformer through the resonant capacitor, and the opposite-name end and the same-name end of the secondary winding are respectively connected to the first output end and the second output end of the transformer.
  • the converter further includes a voltage sampling circuit, which is connected in parallel to both ends of the resonant capacitor and is used to collect the voltage of the resonant capacitor.
  • the controller obtains the voltage of the resonant capacitor and obtains the output voltage of the converter based on the turns ratio of the secondary winding to the primary winding and the voltage of the resonant capacitor.
  • the transformer further includes an auxiliary winding
  • the converter further includes a voltage sampling circuit, which is connected in parallel to both ends of the auxiliary winding for collecting the voltage of the auxiliary winding.
  • the controller obtains the voltage of the auxiliary winding, and obtains the output voltage of the converter based on the turns ratio of the secondary winding to the auxiliary winding and the voltage of the auxiliary winding.
  • the present application provides a terminal device, comprising a battery and a converter provided by any possible implementation of the first aspect to the second aspect, wherein the converter is used to charge the battery.
  • FIG1 is a schematic diagram of an application scenario of a converter provided by the present application.
  • FIG2a is a schematic diagram of a structure of a converter provided by the present application.
  • FIG2b is another schematic diagram of the structure of the converter provided by the present application.
  • FIG3a is another schematic diagram of the structure of the converter provided by the present application.
  • FIG3b is another schematic diagram of the structure of the converter provided by the present application.
  • FIG4 is a schematic diagram of three voltage intervals provided in the present application.
  • FIG5 is a schematic diagram of mode switching of a converter provided by the present application.
  • FIG6 is a control timing diagram of the converter provided by the present application in a high-frequency intermittent wave generation mode
  • FIG7 is a control timing diagram of the converter provided by the present application in a low-frequency intermittent wave generation mode
  • FIG8a is another schematic diagram of the structure of the converter provided by the present application.
  • FIG8b is another schematic diagram of the structure of the converter provided by the present application.
  • FIG9 is a schematic diagram of converter efficiency at different output voltages provided by the present application.
  • FIG10 is a flow chart of a control method for a converter provided by the present application.
  • FIG. 11 is a schematic diagram of the structure of the terminal device provided in the present application.
  • the converter provided in this application can be applied to the field of electronic equipment, industrial field (such as power adapter of laser), aerospace field (such as aerospace power supply) and other fields.
  • the converter provided in this application can be applied to power adapters, industrial power supplies, aerospace power supplies, etc. of electronic devices (such as smart phones, tablet computers, laptops, desktop computers, smart speakers, smart watches and wearable devices, etc.) to convert direct current into voltage and current suitable for electronic equipment, industrial equipment, aerospace equipment, etc.
  • the converter provided in this application is suitable for electronic equipment power supply scenarios, electric vehicle application scenarios or other application scenarios. The following is an example of an electronic equipment power supply scenario.
  • FIG. 1 is a schematic diagram of an application scenario of a converter provided by the present application.
  • the converter provided by the present application may be a power adapter as shown in FIG. 1 .
  • the input end of the power adapter is connected to the power grid through an AC/DC converter, and the output end is connected to the electronic equipment.
  • the AC/DC converter first rectifies and converts the AC voltage (such as 220V) provided by the power grid into a first DC voltage and outputs it to the input end of the power adapter.
  • the power adapter performs a DC conversion on the first DC voltage at the input end to obtain a second DC voltage, and outputs the second DC voltage to the electronic equipment, thereby realizing power supply to the electronic equipment.
  • the power adapter obtains its current output voltage and obtains a mode switching parameter based on the current output voltage.
  • the power adapter controls the converter to switch between the first working mode and the second working mode according to the mode switching parameter, wherein the magnitude of the switching frequency of the converter in the first working mode is negatively correlated with the magnitude of the output current of the converter, and the switching frequency of the converter in the second working mode remains unchanged within one working cycle of the converter.
  • the first working mode is CRM
  • the second working mode is an intermittent wave mode.
  • the power adapter provided by the present application can adjust the mode switching parameters of its own switching between different working modes according to different output voltages, that is, the power adapter adjusts its own working mode according to different output voltages, or the power adapter adjusts its own working parameters from the first working mode to the second working mode to reduce the switching loss, thereby optimizing the efficiency of the power adapter under the full range of output voltages.
  • the above is only an example of the application scenarios of the converter provided by the present application, not an exhaustive list, and the present application does not limit the application scenarios.
  • Figure 2a is a schematic diagram of the structure of the converter provided in the present application.
  • the converter 1 includes a main switch tube S1, an auxiliary switch tube S2, a transformer 11 and a controller 12.
  • one end of the main switch tube S1 is connected to the input terminal in1 of the converter 1
  • the other end of the main switch tube S1 is connected to the reference ground through the auxiliary switch tube S2.
  • the input terminals in21 and in22 of the transformer are respectively connected to the two ends of the auxiliary switch tube S2, and the output terminal out2 of the transformer is connected to the output terminal out1 of the converter 1.
  • the input terminal in1 of the converter 1 is connected to an AC power supply, and the output terminal out1 is connected to a DC load.
  • the converter 1 provided in the present application can be an AHB converter.
  • the positions of the main switch tube S1 and the auxiliary switch tube S2 can be swapped, as shown in Figure 2b.
  • one end of the auxiliary switch tube S2 is connected to the input end in1 of the converter 1, and the other end of the auxiliary switch tube S2 is connected to the reference ground through the main switch tube S1.
  • the controller 12 obtains the current output voltage of the converter 1, and obtains the mode switching parameter based on the current output voltage.
  • the controller 12 controls the converter 1 to switch between the first working mode and the second working mode according to the mode switching parameter, wherein the magnitude of the switching frequency of the converter 1 in the first working mode is negatively correlated with the magnitude of the output current of the converter 1, and the switching frequency of the converter 1 in the second working mode remains unchanged within one working cycle of the converter 1.
  • the first working mode is CRM
  • the second working mode is intermittent wave generation mode.
  • the converter 1 provided in the present application can adjust its mode switching parameters for switching between different operating modes according to different output voltages, that is, the converter 1 adjusts its own operating mode according to different output voltages, or the converter 1 adjusts its own operating parameters from the first operating mode to the second operating mode to reduce the switching loss, thereby optimizing the efficiency of the converter 1 under the full range of output voltages.
  • the controller 12 obtains the current output voltage of the converter 1, and obtains the first switching current threshold value based on the current output voltage.
  • the controller 12 obtains the current output current of the converter 1, and compares the current output current with the first switching current threshold value, thereby controlling the converter 1 to switch between the first working mode and the second working mode according to the comparison result.
  • the converter 1 provided in the present application can adjust the mode switching point (i.e., the switching current threshold) at which it switches between different working modes (i.e., the first working mode and the second working mode) according to different output voltages, that is, the converter 1 adjusts its own working mode according to different output voltages to reduce the switching loss, so that the efficiency of the converter 1 under the full range of output voltages can be optimized.
  • the mode switching point i.e., the switching current threshold
  • the transformer 11 includes an excitation inductor.
  • the controller 12 obtains the current switching frequency and the current output voltage of the converter 1, and obtains the first operating parameter of the converter 1 in the second operating mode according to the current output voltage when the current switching frequency reaches the frequency threshold, thereby controlling the converter 1 to switch from the first operating mode to the second operating mode based on the first operating parameter.
  • the first operating parameter includes the first conduction times of the main switch tube S1 and the auxiliary switch tube S2 in one working cycle of the converter 1, or the current peak value of the excitation inductor in one working cycle of the converter 1.
  • the converter 1 since the switching frequency and switching loss of the converter 1 are often strongly related to the output voltage, the converter 1 provided in the present application can adjust its operating parameters (i.e., the conduction times of the switch tube or the current peak value of the excitation inductor) when switching from the first operating mode to the second operating mode according to different output voltages, so as to reduce the switching frequency and switching loss of the converter 1, thereby optimizing the efficiency of the converter 1 under the full range of output voltages.
  • operating parameters i.e., the conduction times of the switch tube or the current peak value of the excitation inductor
  • converter 1 can reduce the switching loss of converter 1 by adjusting the mode switching point based on the current output voltage, or by adjusting the operating parameters of converter 1 to switch from the first operating mode to the second operating mode based on the current output voltage, thereby optimizing the efficiency of converter 1 under the full range of output voltages.
  • FIG3a is another schematic diagram of the structure of the converter provided by the present application.
  • the converter 1 includes a main switch tube S1, an auxiliary switch tube S2, a transformer 11, a controller 12 and a voltage sampling circuit 13.
  • the converter 1 also includes an input capacitor C in , an output capacitor C o , a rectifier diode D1, an input voltage sampling module 14 and an isolated secondary voltage sampling module 15.
  • the main switch tube S1 and the auxiliary switch tube S2 can be field-effect transistors (FET) made of silicon semiconductor materials (silicon, Si) or third-generation wide bandgap semiconductor materials such as silicon carbide (SiC) or gallium nitride (GaN).
  • FET field-effect transistors
  • This embodiment takes the metal oxide semiconductor field effect transistor (MOSFET) as an example to introduce the main switch tube S1 and the auxiliary switch tube S2.
  • An input capacitor C in is provided between the input terminal in1 of the converter 1 and the reference ground.
  • the input voltage sampling module 14 is provided with an input terminal and an output terminal, the input terminal of the input voltage sampling module 14 is connected to the positive electrode of the input capacitor C in , and the output terminal is connected to the controller 12, for collecting the input voltage of the converter 1, and outputting the input voltage to the controller 12, so as to perform input voltage protection and PWM volt-second balance control.
  • the drain of the main switch S1 is connected to the input terminal in1 of the converter 1 , the source of the main switch S1 is connected to the drain of the auxiliary switch S2 , the source of the auxiliary switch S2 is connected to the reference ground, and the gates of the main switch S1 and the auxiliary switch S2 are connected to the controller 12 .
  • the transformer 11 (i.e., the flyback transformer) includes a primary winding NP , a secondary winding NS , an iron core T1 , an excitation inductor Lm , a resonant inductor Lr (including the leakage inductor of the transformer 11 and the external inductor, which may also be all integrated in the transformer 11) and a resonant capacitor Cr .
  • the input terminal in2 of the transformer 11 includes a first input terminal in21 and a second input terminal in22, and the output terminal out2 of the transformer includes a first output terminal out21 and a second output terminal out22.
  • one end of the resonant inductor Lr is connected to the drain of the auxiliary switch tube S2 through the first input terminal in21 of the transformer 11, the other end of the resonant inductor Lr is connected to the same-name end of the primary winding NP , the opposite-name end of the primary winding NP is connected to one end of the resonant capacitor Cr , the other end of the resonant capacitor Cr is connected to the source of the auxiliary switch tube S2 through the second input terminal in22 of the transformer 11, and the excitation inductor Lm is connected in parallel with the primary winding NP .
  • the opposite-name end and the same-name end of the secondary winding NS are respectively connected to the first output end out21 and the second output end out22 of the transformer 11.
  • the primary winding NP and the secondary winding NS are both coupled to the iron core T1 .
  • the resonant inductor Lr can also be connected between the input end in1 of the converter 1 and the first input end in21 of the transformer 11.
  • the two input ends in21 and in22 of the transformer 11 can also be respectively connected to the two ends of the main switch tube S1.
  • the output terminal out1 of the converter 1 includes a first output terminal out11 and a second output terminal out12.
  • the first output terminal out21 of the transformer 11 is connected to the first output terminal out11 of the converter 1 through a rectifier diode D1, and the second output terminal out22 of the transformer 11 is connected to the second output terminal out12 of the converter 1 and a reference ground.
  • An output capacitor Co is also provided between the first output terminal out21 and the second output terminal out22 of the transformer 11.
  • the voltage sampling circuit 13 includes sampling resistors R1 and R2 , wherein one end of the sampling resistor R2 is connected to one end of the resonant capacitor C r , the other end of the sampling resistor R2 is connected to the other end of the resonant capacitor C r through the sampling resistor R1 , and the connection point between the sampling resistors R1 and R2 is connected to the controller 12.
  • the voltage sampling circuit 13 is used to collect the voltage of the resonant capacitor C r and output the voltage of the resonant capacitor C r to the controller 12.
  • the isolated secondary voltage sampling module 15 is a load sampling module.
  • the isolated secondary voltage sampling module 15 is provided with an input terminal and an output terminal. The input terminal is connected to the positive electrode of the output capacitor Co , and the output terminal is connected to the controller 12.
  • the isolated secondary voltage sampling module 15 includes a phototransistor Q1, a light-emitting diode D2 and a breakdown diode D3, wherein the phototransistor Q1 and the light-emitting diode D2 constitute an optocoupler, which converts the output voltage of the converter 1 into an optical signal through the light-emitting diode D2, and then the phototransistor Q1 converts the received optical signal into a current signal.
  • the isolated secondary voltage sampling module 15 is used to collect the output voltage isolation feedback signal and output the output voltage isolation feedback signal to the controller 12.
  • the output voltage isolation feedback signal is used to control the output voltage stability of the converter 1, and is also used to reflect the load information for subsequent mode switching.
  • the controller 12 obtains the current output voltage of the converter 1, and obtains the first switching current threshold based on the current output voltage.
  • the controller 12 obtains the current output current of the converter 1, and compares the current output current with the first switching current threshold, thereby controlling the converter 1 to switch between the first working mode and the second working mode according to the comparison result.
  • the controller 12 may be the controller 12 shown in FIG3b.
  • the controller 12 includes an input terminal VBULK, an input terminal FB, an input terminal VCR, an output terminal MDRV, an output terminal SDRV, a PWM control unit 121, and a curve control unit 122.
  • the input terminal VBULK and the input terminal FB are respectively connected to the output terminal of the input voltage sampling module 14 and the output terminal of the isolated secondary voltage sampling module 15, the input terminal VCR is connected to the connection point between the sampling resistors R1 and R2 , and the output terminal MDRV and the output terminal SDRV are respectively connected to the gate of the main switch tube S1 and the gate of the auxiliary switch tube S2.
  • the voltage sampling circuit 13 starts to collect the voltage VR2 of the sampling resistor R2 in real time, and outputs the voltage VR2 of the sampling resistor R2 to the input terminal VCR of the controller 12.
  • the voltage VR2 of the sampling resistor R2 can represent the voltage of the resonant capacitor Cr .
  • the isolated secondary voltage sampling module 15 collects the output voltage isolation feedback signal in real time through the optical coupler, and outputs the output voltage isolation feedback signal to the input terminal FB of the controller 12.
  • the curve control unit 122 obtains the current output current of the converter 1 based on the output voltage isolation feedback signal.
  • the curve control unit 122 determines the first voltage interval where the current output voltage Vo of the converter 1 is located from the preset multiple voltage intervals.
  • the preset multiple voltage intervals may be the three voltage intervals shown in FIG4 , namely the high voltage interval H, the medium voltage interval M and the low voltage interval L.
  • the curve control unit 122 determines that the output voltage Vo changes from the medium voltage interval M to the high voltage interval H, that is, determines that the first voltage interval is the high voltage interval H; when the output voltage gradually decreases with time, if the current output voltage Vo is greater than or equal to the voltage threshold Vo_hl , the curve control unit 122 determines that the first voltage interval is the high voltage interval H.
  • the curve control unit 122 determines that the first voltage interval is the medium voltage interval M; when the output voltage gradually decreases with time, if the current output voltage Vo is greater than or equal to the voltage threshold Vo_ml and less than the voltage threshold Vo_hl , the curve control unit 122 determines that the first voltage interval is the medium voltage interval M.
  • the curve control unit 122 determines that the first voltage interval is the medium voltage interval M; when the output voltage gradually decreases with time, if the current output voltage Vo is greater than or equal to the voltage threshold Vo_ll and less than the voltage threshold Vo_ml , the curve control unit 122 determines that the first voltage interval is the medium voltage interval M.
  • FIG5 is a schematic diagram of the mode switching of the converter provided by the present application.
  • the curve control unit 122 determines the first switching current threshold corresponding to the first voltage interval from the three switching current thresholds corresponding to the three voltage intervals, that is, from the switching current threshold I o1 corresponding to the high voltage interval H, the switching current threshold I o2 corresponding to the medium voltage interval M, and the switching current threshold I o3 corresponding to the low voltage interval L shown in FIG5 .
  • the curve control unit 122 determines that the first switching current threshold corresponding to the high voltage interval H is I o1 shown in FIG5 , and sends the first switching current threshold I o1 corresponding to the high voltage interval H to the PWM control unit 121.
  • the first switching current threshold I o1 corresponding to the high voltage interval H is a mode switching point at which the converter 1 switches between the CRM mode and the HBURST mode when the output voltage of the converter 1 is in the high voltage interval HIGH.
  • the first switching current threshold, the second switching current threshold, the third switching current threshold and the fourth switching current threshold are Io1 , Io2 , Io4 and Io3 respectively
  • the first conduction number, the second conduction number, the third conduction number, the fourth conduction number, the fifth conduction number and the sixth conduction number are N1, N2, N3, N4, N5 and N6 respectively
  • the first current peak value, the second current peak value, the third current peak value, the fourth current peak value, the fifth current peak value and the sixth current peak value are I Lm_R1 , I Lm_R2 , I Lm_R3 , I Lm_R4 , I Lm_R5 and I Lm_R6 respectively.
  • Io1 > Io2 > Io3 >0, Io1 > Io4 >0, Io2 and Io4 are not equal.
  • the PWM control unit 121 controls the switching frequency f SW of the converter 1 (i.e., the switching frequency of the main switch tube S1) to decrease as the output current I o increases, or controls the switching frequency f SW of the converter 1 to increase as the output current I o decreases, so that the converter 1 is in CRM.
  • the switching frequency f SW of the converter 1 decreases as the output current I o increases, and since the average current of the primary winding NP is proportional to the average current of the secondary winding NS , the current peak value I Lm(PEAK) of the excitation inductance L m also increases as the output current I o increases; similarly, when the converter 1 is in CRM mode, the switching frequency f SW of the converter 1 increases as the output current I o decreases, and the current peak value I Lm(PEAK) of the excitation inductance L m also decreases as the output current I o decreases.
  • the converter 1 When the current output current of the converter 1 is less than or equal to the first switching current threshold I o1 , the converter 1 is in the HBURST mode:
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one working cycle of the converter 1 (i.e., one high-frequency intermittent cycle T HBURST in the HBURST mode) to be the first conduction number N SW (such as 3), so that the converter 1 is in the HBURST mode.
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent cycle T HBURST to be the second conduction number N SW (such as 2), and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to have a sixth conduction number N SW in a high-frequency intermittent period T HBURST , and the converter 1 is still in the HBURST mode.
  • the specific implementation method of the PWM control unit 121 controlling the converter 1 to be in the HBURST mode is described in the subsequent embodiments, which will not be described in detail here.
  • the converter 1 can adjust the number of times N SW the switches (i.e., the main switch S1 and the auxiliary switch S2) are turned on in a high-frequency intermittent cycle T HBURST based on the change of the load (i.e., the output current I o ), so as to ensure output on demand and avoid the situation where the output is more than the load needs, thereby reducing energy loss and switch loss, and further improving the efficiency of the converter 1.
  • the number of times N SW the switches are turned on in a high-frequency intermittent cycle T HBURST also gradually decreases, so the output voltage ripple of the converter 1 under light load conditions can also be reduced, and the converter has strong applicability.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode by controlling the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the on-time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period T HBURST is the first current peak value I Lm_R1 , so that the converter 1 is in the HBURST mode.
  • the PWM control unit 121 controls the on-time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period T HBURST is the second current peak value I Lm_R2 , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period T HBURST is the sixth current peak value I Lm_R6 , and the converter 1 is still in the HBURST mode.
  • the specific implementation method of the PWM control unit 121 controlling the converter 1 to be in the HBURST mode is described in the subsequent embodiments, which will not be described in detail here.
  • the converter 1 can adjust the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent cycle T HBURST based on the change of the load, so as to ensure the output on demand and avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent cycle T HBURST also gradually decreases, so the output voltage ripple of the converter 1 under light load conditions can also be reduced, and the applicability is strong.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode by simultaneously controlling the number of conduction times of the main switch tube S1 and the auxiliary switch tube S2 within a high-frequency intermittent period THBURST , and the current peak value ILm(PEAK) of the excitation inductance Lm within a high-frequency intermittent period THBURST .
  • the PWM control unit 121 controls the number of conduction times NSW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period THBURST to be a first conduction number N1 (such as 3), and controls the conduction time of the main switch tube S1 so that the current peak value ILm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period THBURST is the first current peak value ILm_R1 , so that the converter 1 is in the HBURST mode.
  • N1 such as 3
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction times N2 (such as 2), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the second current peak value I Lm_R2 , and the converter 1 is still in the HBURST mode.
  • N2 such as 2
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the sixth conduction times N6 (such as 1), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the sixth current peak value I Lm_R6 , and the converter 1 is still in the HBURST mode.
  • N6 such as 1
  • the following takes the first conduction number being 3 and the first current peak being I Lm_R1 as an example to introduce a specific implementation method in which the controller 12 simultaneously controls the conduction number N SW and the current peak I Lm(PEAK) within a high-frequency intermittent period T HBURST so that the converter 1 is in the HBURST mode.
  • FIG6 is a control timing diagram of the converter provided by the present application in the HBURST mode.
  • the high-frequency intermittent period T HBURST starts, and the PWM control unit 121 outputs a high level to the gate G_S2 of the auxiliary switch tube S2 to turn on the auxiliary switch tube S2.
  • the main switch tube S1 is in the off state.
  • the PWM control unit 121 still outputs a high level to the gate G_S2 of the auxiliary switch tube S2, and the auxiliary switch tube S2 is still in the on state, so that the resonant capacitor Cr , the parasitic capacitor of the main switch tube S1, the parasitic capacitor of the auxiliary switch tube S2 and the resonant inductor Lr resonate, and the main switch tube S1 is soft-switched.
  • the main switch tube S1 is still in the off state.
  • the PWM control unit 121 stops outputting a high level to the gate G_S2 of the auxiliary switch tube S2, so that the auxiliary switch tube S2 is turned off.
  • both the main switch tube S1 and the auxiliary switch tube S2 are in the off state, and this time period is the dead time.
  • the PWM control unit 121 outputs a high level to the gate G_S1 of the main switch tube S1 to turn on the main switch tube S1, and the number of times the main switch tube S1 is turned on in a high-frequency intermittent period T HBURST is recorded as 1.
  • the current I Lm of the excitation inductor Lm begins to rise.
  • the PWM control unit 121 still outputs a high level to the gate G_S1 of the main switch tube S1, and the main switch tube S1 is still in the on state. Accordingly, during this time period, the current ILm of the excitation inductor Lm continues to rise.
  • the PWM control unit 121 stops outputting a high level to the gate G_S1 of the main switch tube S1 , so that the main switch tube S1 is turned off.
  • the main switch tube S1 and the auxiliary switch tube S2 are both in the off state, and this time period is the dead time.
  • the current I Lm of the excitation inductor Lm starts to decrease from the first current peak value I Lm_R1 .
  • the PWM control unit 121 outputs a high level to the gate G_S2 of the auxiliary switch tube S2 to turn on the auxiliary switch tube S2, and the number of times the auxiliary switch tube S2 is turned on in one high-frequency intermittent period T HBURST is recorded as 1. It should be noted that the number of times the auxiliary switch tube S2 is turned on to achieve soft switching of the main switch tube S1 at the beginning of the high-frequency intermittent period T HBURST is not recorded in the number of times the auxiliary switch tube S2 is turned on in one high-frequency intermittent period T HBURST .
  • the PWM control unit 121 still outputs a high level to the gate G_S2 of the auxiliary switch tube S2, so the auxiliary switch tube S2 is still in the on state and the main switch tube S1 is in the off state. Accordingly, during this period, the current ILm of the excitation inductor Lm is still decreasing.
  • the magnetizing inductance Lm reaches the volt-second balance, and the PWM control unit 121 stops outputting a high level to the gate G_S2 of the auxiliary switch tube S2, so that the auxiliary switch tube S2 is turned off.
  • both the main switch tube S1 and the auxiliary switch tube S2 are in the off state, and this time period is the dead time.
  • the PWM control unit 121 controls the main switch S1 and the auxiliary switch S2 to repeat the steps of the time period from t 2 to t 6 until the number of times the main switch S1 and the number of times the auxiliary switch S2 are turned on are both 3.
  • the PWM control unit 121 no longer outputs a high level to the gate G_S1 of the main switch tube S1 and the gate G_S2 of the auxiliary switch tube S2, so that the main switch tube S1 and the auxiliary switch tube S2 are both turned off.
  • both the main switch tube S1 and the auxiliary switch tube S2 are in the off state.
  • the high-frequency intermittent period T HBURST ends.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to perform periodic operation according to a high-frequency intermittent period T HBURST within time t0 - t8 .
  • the specific implementation of the converter 1 in the HBURST mode can refer to the description of the embodiment shown in FIG. 6 .
  • the converter 1 when the converter 1 is in the HBURST mode, the converter 1 can adjust the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST and the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent cycle T HBURST based on the change of the load, so as to ensure the output on demand and avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • PEAK current peak value
  • the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST and the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent cycle T HBURST are gradually reduced, which can further reduce the energy output. Therefore, the output voltage ripple of the converter 1 under light load conditions can also be further reduced, and the applicability is stronger.
  • the converter 1 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o1 , the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the current output current I o :
  • the controller 12 controls the number of conduction times NSW of the switch tube in a high-frequency intermittent period THBURST to be the first conduction number N1, and/or controls the current peak value Ilm (PEAK) of the excitation inductance Lm in a high-frequency intermittent period to be the first current peak value Ilm_R1 ;
  • the controller 12 controls the number of conduction times NSW of the switch tube in a high-frequency intermittent period THBURST to be the second conduction number N2, and/or controls the current peak value Ilm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period to be the second current peak value Ilm_R2 ;
  • the controller 12 controls the number of conduction times NSW of the switch tube in a high-frequency intermittent period THBURST to be the first conduction number N1, and/or controls the current peak value Ilm (PEAK) of the excitation inductance Lm in a high-frequency intermittent period to be the first current peak value Ilm_R1 ;
  • the controller 12 controls the
  • Lm(PEAK) is the third current peak value I Lm_R3 ; when the current output current I o is in the fourth current interval (0, I o4 ], the controller 12 controls the converter 1 to be in the LBURST mode based on the number of conduction times N SW of the switch tube in a high-frequency intermittent period T HBURST being the fourth conduction number N4, and/or the current peak value I Lm(PEAK) of the excitation inductor L m being the fourth current peak value I Lm_R4 ; when the current output current I o is in the fifth current interval (0, I o3 ], the controller 12 controls the number of conduction times N SW of the switch tube in a high-frequency intermittent period T HBURST to be the sixth conduction number N6, and/or controls the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period to be the sixth current peak value I Lm_R6 .
  • the PWM control unit 121 can select any current interval from the above overlapping multiple current intervals or a current interval that meets the actual working condition of the converter 1 as the target current interval, and when the current output current Io is located in the above overlapping current interval, control the converter 1 to execute the steps when the current output current Io is located in the target current interval. Based on this, it can be obtained that the control mode of the converter 1 in the HBURST mode or the LBURST mode is diverse and highly flexible. In addition, the size relationship between Io2 , Io4 and Io3 is diverse, so that the control mode of the converter 1 in the HBURST mode or the LBURST mode is more diverse and more flexible.
  • the converter 1 is described in the following by taking I o2 >I o3 >I o4 as an example to be in the HBURST mode or the LBURST mode.
  • Io2 > Io3 > Io4 since the size between Io1 , Io2 and Io3 is fixed, that is, Io1 > Io2 > Io3 , it can be obtained that the first current interval ( Io2 , Io1 ] overlaps with the third current interval ( Io4 , Io1 ] and the overlapping current interval is ( Io2 , Io1 ].
  • the controller 12 can select the first current interval ( Io2 , Io1 ] or the third current interval ( Io4 , Io1 ] as the target current interval under the overlapping current interval ( Io2, Io1].
  • This embodiment takes the first current interval (Io2 , Io1 ] as the target current interval under the overlapping current interval ( Io2 , Io1 ] as an example for introduction; the second current interval ( Io3 , Io2 ] overlaps with the third current interval ( Io4 , Io1 ] and the overlapping current interval is ( Io3 , Io2 ], the controller 12 may select the second current interval (I o3 , I o2 ] or the third current interval (I o4 , I o1 ] as the target current interval under the overlapping current interval (I o3 , I o2 ], and this embodiment is introduced by taking the second current interval (I o3 , I o2 ] as the target current interval under the overlapping current interval (
  • the PWM control unit 121 performs the above steps when the current output current I o is in the first current interval (I o2 , I o1 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the first conduction number N1 (such as 3), so that the converter 1 is in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the second switching current threshold I o2 and greater than the fourth switching current threshold I o3 , the PWM control unit 121 performs the above steps when the current output current I o is in the second current interval (I o3 , I o2 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the second conduction number N2 (such as 2), and the converter 1 is still in the HBURST mode.
  • the second conduction number N2 such as 2
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the fourth switching current threshold I o3 When the current output current I o is less than or equal to the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the third current interval (I o4 , I o1 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the third conduction number N3 (such as 1), and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the fourth current interval (0, I o4 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the fourth conduction number N4 (such as 1), and after the first working cycle number of the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is the fourth conduction number N4, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T
  • the number of conduction times N SW of HBURST is the fifth number of conduction times N5 (i.e., 0), that is, the PWM control unit 121 controls the main switch
  • the converter 1 when the current output current I o of the converter 1 is less than or equal to the third switching current threshold I o4 , the converter 1 is in the LBURST mode.
  • the number of the first working cycle is a positive integer, and illustratively, the number of the first working cycle is 3.
  • the working mode of the converter 1 under extremely light load i.e., the output current I o is less than or equal to the third switching current threshold I o4
  • the working mode of the converter 1 under extremely light load is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode or LBURST mode by controlling the current peak value I Lm(PEAK) of the excitation inductance Lm within a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o1 and greater than the second switching current threshold I o2 , the PWM control unit 121 performs the above steps when the current output current I o is in the first current interval (I o2 , I o1 ]), that is, by controlling the on-time of the main switch tube S1, the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R1 , so that the converter 1 is in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the second switching current threshold I o2 and greater than the fourth switching current threshold I o3 , the PWM control unit 121 performs the above steps when the current output current I o is in the second current interval (I o3 , I o2 ]), that is, by controlling the on-time of the main switch tube S1, the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the second current peak value I Lm_R2 , the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the fourth switching current threshold I o3 and greater than the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the third current interval (I o4 , I o1 ], that is, by controlling the on-time of the main switch tube S1, so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the third current peak value I Lm_R3 , and the converter 1 is still in the HBURST mode.
  • the third current interval I o4 , I o1
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the PWM control unit 121 can also simultaneously control the conduction times NSW of the main switch tube S1 and the auxiliary switch tube S2 within a high-frequency intermittent period THBURST , and the current peak value ILm(PEAK) of the excitation inductance Lm within a high-frequency intermittent period THBURST , so as to put the converter 1 in the HBURST mode or the LBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o1 and greater than the second switching current threshold I o2 , the PWM control unit 121 performs the above steps when the current output current I o is in the first current interval (I o2 , I o1 ]), that is, controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N1 (such as 3), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R1 , so that the converter 1 is in the HBURST mode.
  • the first current interval I o2 , I o1 ]
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the second switching current threshold I o2 and greater than the fourth switching current threshold I o3 , the PWM control unit 121 performs the above steps when the current output current I o is in the second current interval (I o3 , I o2 ]), that is, controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first current peak value I Lm_R1.
  • SW is the second conduction number N2 (such as 2), and the conduction time of the main switch tube S1 is controlled so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the second current peak value I Lm_R2 , and the converter 1 is still in the HBURST mode.
  • N2 such as 2
  • the PWM control unit 121 performs the above steps when the current output current I o is located in the third current interval (I o4 , I o1 ] , that is, the conduction number N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the third conduction number N3 (such as 1), and the conduction time of the main switch tube S1 is controlled so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the third current peak value I Lm_R3 , and the converter 1 is still in the HBURST mode.
  • the third current interval I o4 , I o1 ]
  • N3 such as 1
  • the conduction time of the main switch tube S1 is controlled so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the third current peak
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the fourth switching current threshold I o3 and greater than the third switching current threshold I o4, the PWM control unit 121 performs the above steps when the current output current I o is located in the third current interval (I o4 , I o1 ]), that is, the conduction number N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the third conduction number N3 (such as 1), and the conduction time of the main switch tube S1 is controlled so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the third current peak value I Lm_R3 , and the converter
  • the PWM control unit 121 When the output current I o is less than or equal to the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the
  • the following takes the first working cycle number and the fourth conduction number as 1, and the fourth current peak value I Lm_R3 as an example, and introduces a specific implementation method in which the controller 12 simultaneously controls the conduction number N SW and the current peak value I Lm(PEAK) within a high-frequency intermittent period T HBURST so that the converter 1 is in the LBURST mode.
  • FIG. 7 is a control timing diagram of the converter provided by the present application in the LBURST mode.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to turn on or off, so that the LBURST mode starts, that is, the converter 1 starts to work in the first high-frequency intermittent wave generation cycle THBURST , wherein, in a high-frequency intermittent wave generation cycle THBURST , the number of times the main switch tube S1 and the auxiliary switch tube S2 are turned on NSW is 1, and the current peak value I Lm (PEAK) of the excitation inductor Lm is I Lm_R3 .
  • the specific implementation method of the converter 1 working in a high-frequency intermittent wave generation cycle THBURST can refer to the description of the corresponding part of the embodiment shown in FIG. 6.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on or off, so that the converter 1 continuously operates for three high-frequency intermittent wave cycles T HBURST .
  • the converter 1 has been working for three high-frequency intermittent wave cycles THBURST , and the PWM control unit 121 no longer outputs a high level to the gate G_S1 of the main switch S1 and the gate G_S2 of the auxiliary switch S2, so that the main switch S1 and the auxiliary switch S2 are both turned off.
  • the PWM control unit 121 After time t 1 ′, the PWM control unit 121 no longer outputs a high level to the gate G_S1 of the main switch tube S1 and the gate G_S2 of the auxiliary switch tube S2 , so that both the main switch tube S1 and the auxiliary switch tube S2 are turned off.
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the converter 1 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o1 , the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the operating frequency of the converter 1 :
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to have a first conduction number N SW in a high-frequency intermittent period T HBURST (e.g., 3), so that the converter 1 is in the HBURST mode.
  • T HBURST a high-frequency intermittent period
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on the fourth turn-on number N SW N4 (such as 1) in a high-frequency intermittent period, and after the first working cycle number of times the turn-on number N SW of the main switch tube S1 and the auxiliary switch tube S2 is the fourth turn-on number N4 in a high-frequency intermittent period, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on the fifth turn-on number N5 (i.e.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state all the time.
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the fifth turn-on number N5 (i.e., 0) in a high-frequency intermittent period.
  • the conduction number N SW of HBURST is the first conduction number N1.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the first number of times N SW in a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period to be the second conduction times N2 (such as 2), and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the second number of times N SW in one high-frequency intermittent period T HBURST as N2.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the second number of times N SW in one high-frequency intermittent period T HBURST is N2.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to have a sixth conduction number N SW in a high-frequency intermittent period, and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the sixth number of times N SW in one high-frequency intermittent period T HBURST , which is N6.
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent period T HBURST is within the hearing range of the human ear is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode or LBURST mode by controlling the current peak value I Lm(PEAK) of the excitation inductance Lm within a high-frequency intermittent cycle.
  • the PWM control unit 121 controls the on-time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent cycle is the first current peak value I Lm_R1 , so that the converter 1 is in the HBURST mode.
  • the PWM control unit 121 controls the on-time of the main switch tube S1 so that the excitation inductance L m is
  • the current peak value I Lm (PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fourth current peak value I Lm_R4
  • the PWM control unit 121 controls the on-time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fifth current peak value I Lm_R5 (i.e., 0), that is, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off
  • the converter 1 when the frequency f HBURST of the high-frequency intermittent cycle T HBURST is within the human ear hearing range, the converter 1 is in the LBURST mode.
  • the PWM control unit 121 continues to control the on-time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the first current peak value I Lm_R1 .
  • the PWM control unit 121 continues to control the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period is the first current peak value I Lm_R1 .
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent cycle is the second current peak value I Lm_R2 , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 converter 1 When the frequency f HBURST of the high-frequency intermittent cycle T HBURST is When HBURST is within the hearing range of the human ear, the PWM control unit 121 converter 1 is in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the second current peak value I Lm_R2 .
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period is the second current peak value I Lm_R2 .
  • the PWM control unit 121 converter 1 When the frequency f HBURST of the high-frequency intermittent cycle T HBURST is When HBURST is within the hearing range of the human ear, the PWM control unit 121 converter 1 is in the LBURST mode.
  • the specific implementation method of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the sixth current peak value I Lm_R6 .
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent cycle T HBURST is within the human ear hearing range is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the PWM control unit 121 can also simultaneously control the conduction times NSW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle, and the current peak value ILm(PEAK) of the excitation inductance Lm in a high-frequency intermittent cycle, so as to put the converter 1 in the HBURST mode or the LBURST mode.
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N1 (such as 3), and controls the conduction time of the main switch tube S1 to make the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent period to be the first current peak value I Lm_R1 , so that the converter 1 is in the HBURST mode.
  • N1 such as 3
  • the PWM control unit 121 calculates the frequency f of the high-frequency intermittent period T HBURST when the number of conduction times N SW of the switch tube is the first conduction number N1 and the current peak value I Lm (PEAK) of the excitation inductor L m is the first current peak value I Lm_R1.
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period to be the fourth conduction times N4 (such as 1), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the fourth current peak value I Lm_R4 , and after the first working cycle number in which the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the fourth current peak value I Lm_R4 and the conduction times N SW of the switch tube is the fourth conduction times N SW of the switch tube is the fourth conduction times N SW of the switch tube is the fourth conduction times N SW of the switch tube is the fourth conduction times N SW of the switch tube is the fourth conduction times N SW of the switch tube is the fourth conduction times N SW of the switch tube is the fourth conduction times N SW of the switch tube is the fourth
  • SW are all the fifth conduction times N5 (i.e., 0), and the conduction time of the main switch tube S1 is controlled so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fifth current peak value I Lm_R5 (i.e., 0), that is, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state all the time.
  • the converter 1 is in the LBURST mode.
  • the PWM control unit 121 continues to control the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent cycle T HBURST to be the first conduction times N1, and continues to control the conduction time of the main switch tube S1 to make the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle be the first current peak value I Lm_R1 .
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction time N1, and continues to control the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period is the first current peak value I Lm_R1 .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle to be the second conduction number N2 (such as 2), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent cycle is the second current peak value I Lm_R2 , and the converter 1 is still in the HBURST mode.
  • N2 such as 2
  • the PWM control unit 121 calculates the frequency f HBURST of the high-frequency intermittent cycle T HBURST in which the number of conduction times N SW of the switch tube is the second conduction number N2 and the current peak value I Lm (PEAK) of the excitation inductor L m is the second current peak value I Lm_R2 .
  • the PWM control unit 121 and the converter 1 are in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second number of conduction times N2, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period is the second current peak value I Lm_R2 .
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N2, and continues to control the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period is the second current peak value I Lm_R2 .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle to be the sixth conduction number N6 (such as 1), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent cycle is the sixth current peak value I Lm_R6 , and the converter 1 is still in the HBURST mode.
  • N6 such as 1
  • the PWM control unit 121 and the converter 1 are in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the sixth conduction times N6, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the sixth current peak value I Lm_R6 .
  • the working mode of the converter 1 is further optimized when the frequency f HBURST of the high-frequency intermittent period T HBURST is within the human ear hearing range, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the frequency f HBURST of the high-frequency intermittent period T HBURST is within the human ear hearing range, the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the above embodiments are all based on the current interval where the current output voltage is in the high voltage interval H, and the converter 1 is controlled to be in the CRM mode or the intermittent wave mode according to the current interval where the current output current Io is located.
  • the following is a detailed introduction in combination with the change trend of the output current of the converter 1.
  • the converter 1 switches from the CRM mode to the HBURST mode; in order to further improve the efficiency of the converter 1 under extremely light load conditions, after the converter 1 is in the HBURST mode, when the output current of the converter 1 continues to drop to the third switching current threshold Io4 , the converter 1 switches from the HBURST mode to the LBURST mode.
  • the converter 1 switches from the LBURST mode to the HBURST mode; when the output current of the converter 1 continues to rise to the first switching current threshold Io1 , the converter 1 switches from the HBURST mode to the CRM mode.
  • the curve control unit 122 determines that the first switching current threshold corresponding to the medium voltage interval M is I o2 shown in FIG5 , and sends the first switching current threshold I o2 corresponding to the medium voltage interval M to the PWM control unit 121.
  • the first switching current threshold I o2 corresponding to the medium voltage interval M is a mode switching point at which the converter 1 switches between the CRM mode and the HBURST mode when the output voltage of the converter 1 is in the medium voltage interval M.
  • the first switching current threshold, the second switching current threshold and the third switching current threshold are Io2 , Io3 and Io4 respectively
  • the first conduction number, the second conduction number, the third conduction number, the fourth conduction number and the fifth conduction number are N2, N6, N3, N4 and N5 respectively.
  • the first current peak value, the second current peak value, the third current peak value, the fourth current peak value and the fifth current peak value are I Lm_R2 , I Lm_R6 , I Lm_R3 , I Lm_R4 and I Lm_R5 respectively.
  • Io2 > Io3 >0, Io2 > Io4 >0, Io3 and Io4 are not equal.
  • N2>N6, N3 ⁇ N4, N5 0, N2, N3, N4 and N6 are all positive integers.
  • I Lm_R2 >I Lm_R6 >0, I Lm_R3 ⁇ I Lm_R4 >0, I Lm_R5 0, and the values of I Lm_R2 , I Lm_R3 , I Lm_R4 and I Lm_R6 satisfy the conditions that the switching frequency f SW of the converter 1 is less than the maximum switching frequency f SW(MAX) and the frequency f HBURST of the high-frequency intermittent period T HBURST is outside the hearing range of the human ear.
  • the PWM control unit 121 controls the switching frequency f SW of the converter 1 to decrease as the output current I o increases, or controls the switching frequency f SW of the converter 1 to increase as the output current I o decreases, so that the converter 1 is in CRM.
  • the switching frequency f SW of the converter 1 is lower than the switching frequency f SW of the converter 1 when the output voltage is in the high voltage interval H.
  • the converter 1 When the current output current of the converter 1 is less than or equal to the first switching current threshold I o2 , the converter 1 is in the HBURST mode:
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N SW (such as 2), so that the converter 1 is in the HBURST mode.
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N SW N 6 (such as 1), and the converter 1 is still in the HBURST mode.
  • the converter 1 when the converter 1 is in the HBURST mode, the converter 1 can adjust the number of times the switch is turned on N SW in a high-frequency intermittent cycle T HBURST based on the change in load, to ensure output on demand and avoid outputting more than the load requires, thereby reducing energy loss and switch loss, and further improving the efficiency of the converter 1.
  • the number of times the switch is turned on N SW in a high-frequency intermittent cycle T HBURST also gradually decreases, and therefore, the output voltage ripple of the converter 1 under light load conditions can also be reduced, and the converter has strong applicability.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode by controlling the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the on-time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R2 , and the converter 1 is in the HBURST mode.
  • the specific implementation method of the PWM control unit 121 controlling the converter 1 to be in the HBURST mode can be found in the description of the subsequent embodiments, which will not be described in detail here.
  • the converter 1 can adjust the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent cycle T HBURST based on the change of the load, so as to ensure the output on demand and avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent cycle T HBURST also gradually decreases, so the output voltage ripple of the converter 1 under light load conditions can also be reduced, and the applicability is strong.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode by simultaneously controlling the conduction times of the main switch tube S1 and the auxiliary switch tube S2 within a high-frequency intermittent period THBURST , and the current peak value ILm(PEAK) of the excitation inductance Lm within a high-frequency intermittent period THBURST .
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction times N2 (such as 2), and controls the conduction time of the main switch tube S1 so that the first current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the current peak value I Lm_R2 , and the converter 1 is in the HBURST mode.
  • N2 such as 2
  • the converter 1 when the converter 1 is in the HBURST mode, the converter 1 can adjust the number of conduction times N SW of the switch tube in a high-frequency intermittent period T HBURST and the current peak value I Lm (PEAK) of the excitation inductor L m based on the change of the load, so as to ensure the output on demand and avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • PEAK current peak value
  • the number of conduction times N SW of the switch tube in a high-frequency intermittent period T HBURST and the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST are gradually reduced, which can further reduce the energy output. Therefore, the output voltage ripple of the converter 1 under light load conditions can also be further reduced, and the applicability is stronger.
  • the converter 1 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o2 , the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the current output current I o :
  • the controller 12 controls the number of conduction times NSW of the switch tube in a high-frequency intermittent period THBURST to be the first conduction number N2, and/or controls the current peak value I Lm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period to be the first current peak value I Lm_R2 ;
  • the controller 12 controls the converter 1 to be in the LBURST mode based on the number of conduction times NSW of the switch tube in a high-frequency intermittent period THBURST being the fourth conduction number N4, and/or the current peak value I Lm(PEAK) of the excitation inductance Lm being the fourth current peak value I Lm_R4 ;
  • the controller 12 controls the number of conduction times NSW of the switch tube in a high-frequency intermittent period THBURST to be the first conduction number N2, and/or controls the current peak value I Lm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period to be the first current peak value I Lm_R
  • the PWM control unit 121 can select any current interval from the above overlapping multiple current intervals or a current interval that meets the actual working condition of the converter 1 as the target current interval, and when the current output current Io is located in the above overlapping current interval, control the converter 1 to execute the steps when the current output current Io is located in the target current interval. Based on this, it can be obtained that the control mode of the converter 1 in the HBURST mode or the LBURST mode is diverse and highly flexible. In addition, the size relationship between Io3 and Io4 is diverse, so that the control mode of the converter 1 in the HBURST mode or the LBURST mode is more diverse and more flexible.
  • the converter 1 is described in the following by taking I o3 >I o4 as an example to be in the HBURST mode or the LBURST mode.
  • I o2 >I o4 since I o2 >I o3 and I o2 >I o4 , it can be obtained that the second current interval (I o3 ,I o2 ] overlaps with the sixth current interval (I o4 ,I o2 ] and the overlapping current interval is (I o3 ,I o2 ], and the controller 12 can select the second current interval (I o3 ,I o2 ] or the sixth current interval (I o4 ,I o2 ] as the target current interval under the overlapping current interval (I o3 ,I o2 ], and this embodiment is introduced by taking the second current interval (I o3 ,I o2 ] as the target current interval under the overlapping current interval (I o3 ,I o2 ], and this embodiment is introduced by taking
  • the PWM control unit 121 performs the above steps when the current output current I o is in the second current interval (I o3 , I o2 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the first conduction number N2 (such as 2), and the converter 1 is in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the second switching current threshold I o3 and greater than the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the sixth current interval (I o4 , I o2], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the third conduction number N3 (such as 1), and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the third switching current threshold I o3, the PWM control unit 121 performs the above steps when the current output current I o is in the sixth current interval (I o4, I o2 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the third conduction number N3 (such as 1), and the converter 1 is still in the HBURST mode.
  • the sixth current interval I o4, I o2
  • the PWM control unit 121 performs the above steps when the current output current I o is in the fourth current interval (0, I o4 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the fourth conduction number N4 (such as 1), and after the first working cycle number in which the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is the fourth conduction number N4, the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the fifth conduction number N5 (i.e.
  • the first working cycle number is a positive integer, and illustratively, the first working cycle number is 3.
  • the working mode of the converter 1 under extremely light load i.e., the output current I o is less than or equal to the third switching current threshold I o4
  • the working mode of the converter 1 under extremely light load is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode or LBURST mode by controlling the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o2 and greater than the second switching current threshold I o3 , the PWM control unit 121 performs the above steps when the current output current I o is in the second current interval (I o3 , I o2 ]), that is, by controlling the on-time of the main switch tube S1, the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R2 , and the converter 1 is in the HBURST mode.
  • the second current interval I o3 , I o2
  • the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R2 , and the converter 1 is in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the second switching current threshold I o3 and greater than the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the sixth current interval (I o4 , I o2 ]), that is, by controlling the on-time of the main switch tube S1, the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the third current peak value I Lm_R3 , the converter 1 is still in the HBURST mode.
  • the sixth current interval I o4 , I o2
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the PWM control unit 121 can also simultaneously control the conduction times NSW of the main switch tube S1 and the auxiliary switch tube S2 within a high-frequency intermittent period THBURST , and the current peak value ILm(PEAK) of the excitation inductance Lm within a high-frequency intermittent period THBURST , so as to put the converter 1 in the HBURST mode or the LBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o2 and greater than the second switching current threshold I o3 , the PWM control unit 121 performs the above steps when the current output current I o is in the second current interval (I o3 , I o2 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the first conduction number N2 (such as 2), and the conduction time of the main switch tube S1 is controlled so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R2 , and the converter 1 is in the HBURST mode.
  • the second current interval I o3 , I o2
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the second switching current threshold I o3 and greater than the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the sixth current interval (I o4 , I o2 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the first current peak value I Lm_R2.
  • SW is the third conduction number N3 (such as 1), and the conduction time of the main switch tube S1 is controlled so that the current peak value I Lm (PEAK) of the excitation inductance L m in one high-frequency intermittent period T HBURST is the third current peak value I Lm_R3 , and the converter 1 is still in the HBURST mode.
  • N3 such as 1
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the converter 1 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o2 , the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the operating frequency of the converter 1 :
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to have a first conduction number N SW in a high-frequency intermittent cycle, and the converter 1 is in the HBURST mode.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on the fourth turn-on number N SW in a high-frequency intermittent cycle (e.g., 1), and after the first working cycle number in which the main switch tube S1 and the auxiliary switch tube S2 are turned on the fourth turn-on number N SW in a high-frequency intermittent cycle, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on the fifth turn-on number N SW in a high-frequency intermittent cycle (i.e., 0), that is, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state.
  • a high-frequency intermittent cycle e.g. 1
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the fifth turn-on number N SW in a high-frequency intermittent cycle T
  • the conduction number N SW of HBURST is the first conduction number N2.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the first number of times N SW in a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the second number of times N SW in one high-frequency intermittent period T HBURST as N6.
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent period T HBURST is within the human ear hearing range is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode or LBURST mode by controlling the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent cycle.
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent cycle is the first current peak value I Lm_R2 , and the converter 1 is in the HBURST mode.
  • the PWM control unit 121 converter 1 When the frequency f HBURST of the high-frequency intermittent cycle T HBURST is When HBURST is within the hearing range of the human ear, the PWM control unit 121 converter 1 is in the LBURST mode.
  • the specific implementation method of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the first current peak value I Lm_R2 .
  • the PWM control unit 121 continues to control the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period is the first current peak value I Lm_R2 .
  • the PWM control unit 121 converter 1 When the frequency f HBURST of the high-frequency intermittent cycle T HBURST is When HBURST is within the hearing range of the human ear, the PWM control unit 121 converter 1 is in the LBURST mode.
  • the specific implementation method of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the second current peak value I Lm_R6 .
  • the working mode of the converter 1 is further optimized when the frequency f HBURST of the high-frequency intermittent cycle T HBURST is within the human ear hearing range, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the frequency f HBURST of the high-frequency intermittent cycle T HBURST is within the human ear hearing range, the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the PWM control unit 121 can also simultaneously control the conduction times NSW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle, and the current peak value I Lm(PEAK) of the excitation inductance Lm in a high-frequency intermittent cycle, so as to put the converter 1 in the HBURST mode or the LBURST mode.
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle to be the first conduction number N2 (such as 2), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent cycle is the first current peak value I Lm_R2 , and the converter 1 is in the HBURST mode.
  • N2 such as 2
  • the PWM control unit 121 and the converter 1 are in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N2, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period is the first current peak value I Lm_R2 .
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction time N2, and continues to control the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period is the first current peak value I Lm_R2 .
  • the PWM control unit 121 calculates the high-frequency intermittent cycle T HBURST when the number of conduction times N SW of the switch tube is the second conduction number N6 and the current peak value I Lm(PEAK) of the excitation inductor L m is the second current peak value I Lm_R6.
  • the PWM control unit 121 and the converter 1 are in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N6, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period is the second current peak value I Lm_R6 .
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent period T HBURST is within the human ear hearing range is further optimized, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the above embodiments are all based on the current interval where the current output voltage is in the medium voltage interval M, and the converter 1 is controlled to be in the CRM mode or the intermittent wave mode according to the current interval where the current output current Io is located.
  • the following is a detailed introduction in combination with the change trend of the output current of the converter 1.
  • the converter 1 switches from the CRM mode to the HBURST mode; in order to further improve the efficiency of the converter 1 under extremely light load conditions, after the converter 1 is in the HBURST mode, when the output current of the converter 1 continues to drop to the third switching current threshold Io4 , the converter 1 switches from the HBURST mode to the LBURST mode.
  • the converter 1 switches from the LBURST mode to the HBURST mode; when the output current of the converter 1 continues to rise to the first switching current threshold Io2 , the converter 1 switches from the HBURST mode to the CRM mode.
  • the curve control unit 122 determines that the first switching current threshold corresponding to the low voltage interval L is I o3 shown in FIG5 , and sends the first switching current threshold I o3 corresponding to the low voltage interval L to the PWM control unit 121.
  • the first switching current threshold I o3 corresponding to the low voltage interval L is a mode switching point at which the converter 1 switches between the CRM mode and the HBURST mode when the output voltage of the converter 1 is in the low voltage interval L.
  • the first switching current threshold and the third switching current threshold are I o3 and I o4 respectively
  • the third conduction number, the fourth conduction number and the fifth conduction number are N3, N4 and N5 respectively
  • the third current peak value, the fourth current peak value and the fifth current peak value are I Lm_R3 , I Lm_R4 and I Lm_R5 respectively.
  • I Lm_R3 ⁇ I Lm_R4 >0, I Lm_R5 0, and the values of I Lm_R3 and I Lm_R4 meet the conditions that the switching frequency f SW of the converter 1 is less than the maximum switching frequency f SW(MAX) and the frequency f HBURST of the high-frequency intermittent period T HBURST is outside the hearing range of the human ear.
  • the PWM control unit 121 controls the switching frequency f SW of the converter 1 to decrease as the output current I o increases, or controls the switching frequency f SW of the converter 1 to increase as the output current I o decreases, so that the converter 1 is in CRM.
  • the switching frequency f SW of the converter 1 is lower than the switching frequency f SW of the converter 1 when the output voltage is in the medium voltage interval M.
  • the converter 1 When the current output current of the converter 1 is less than or equal to the first switching current threshold I o3 , the converter 1 is in the HBURST mode:
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be a third conduction times N3 (such as 1), so that the converter 1 is in the HBURST mode.
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m within a high-frequency intermittent period T HBURST is a third current peak value I Lm_R3 , and the converter 1 is in the HBURST mode.
  • I Lm_R3 satisfies the conditions that the switching frequency f SW of the converter 1 is less than the maximum switching frequency f SW(MAX) and the frequency f HBURST of the high-frequency intermittent period T HBURST is outside the hearing range of the human ear.
  • the PWM control unit 121 controls the number of conduction times NSW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period THBURST to be a third conduction number N3 (such as 1), and controls the conduction time of the main switch tube S1 so that the current peak value ILm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period THBURST is a third current peak value ILm_R3 , and the converter 1 is in HBURST mode.
  • N3 such as 1
  • the converter 1 can be placed in the HBURST mode by adjusting the number of conduction times N SW of the switch tube within a high-frequency intermittent period T HBURST and/or the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent period T HBURST , with diverse control methods and high flexibility.
  • the converter 1 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o3 , the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the current output current I o :
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the third conduction number N3 (such as 1), and the converter 1 is in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the fourth current interval (0, I o4 ], that is, controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the fourth conduction number N4 (such as 1), and the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST is N SW.
  • the PWM control unit 121 controls the conduction number N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the fifth conduction number N5 (i.e., 0), that is, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state all the time.
  • the first working cycle number is a positive integer, and illustratively, the first working cycle number is 3.
  • the working mode of the converter 1 under extremely light load i.e., the output current I o is less than or equal to the switching current threshold I o4
  • the working mode of the converter 1 under extremely light load is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • this embodiment can not only reduce the output voltage ripple of the converter 1 under light load, but also further reduce the output voltage ripple of the converter 1 under extremely light load, and has stronger applicability.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode or LBURST mode by controlling the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent period T HBURST is the third current peak value I Lm_R3 , and the converter 1 is in the HBURST mode.
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the PWM control unit 121 can also simultaneously control the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 within a high-frequency intermittent period T HBURST , and the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent period T HBURST , so as to put the converter 1 in the HBURST mode or the LBURST mode.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to have a third conduction number N SW in a high-frequency intermittent period T HBURST , and controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R3 , and the converter 1 is in the HBURST mode.
  • PEAK current peak value
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the converter 1 When the current output current I o of the converter 1 is less than or equal to the first switching current threshold I o3 , the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the operating frequency of the converter 1 :
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on the fourth turn-on number N SW in a high-frequency intermittent cycle (e.g., 1), and after the first working cycle number of times the main switch tube S1 and the auxiliary switch tube S2 are turned on the fourth turn-on number N SW in a high-frequency intermittent cycle, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on the fifth turn-on number N SW in a high-frequency intermittent cycle (i.e., 0), that is, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state.
  • a high-frequency intermittent cycle e.g. 1
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the fifth turn-on number N SW in a high-frequency intermittent cycle T
  • the conduction number N SW of HBURST is the third conduction number N3.
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent period T HBURST is within the human ear hearing range is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the PWM control unit 121 can also put the converter 1 in HBURST mode or LBURST mode by controlling the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent cycle.
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent cycle is the third current peak value I Lm_R3 , and the converter 1 is in the HBURST mode.
  • the PWM control unit 121 converter 1 When the frequency f HBURST of the high-frequency intermittent cycle T HBURST is When HBURST is within the hearing range of the human ear, the PWM control unit 121 converter 1 is in the LBURST mode.
  • the specific implementation method of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the third current peak value I Lm_R3 .
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent cycle T HBURST is within the human ear hearing range is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the PWM control unit 121 can also simultaneously control the conduction times Nsw of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle, and the current peak value Ilm (PEAK) of the excitation inductance Lm in a high-frequency intermittent cycle, so as to put the converter 1 in the HBURST mode or the LBURST mode.
  • PEAK current peak value Ilm
  • the PWM control unit 121 calculates that the number of conduction times N SW of the switch tube is the third conduction number N3 and the current peak value I Lm(PEAK) of the excitation inductor L m is the third current peak value I Lm_R3 .
  • the frequency f HBURST of the high-frequency intermittent period T HBURST of Lm_R3 1/T HBURST , and it is determined whether the frequency f HBURST of the high-frequency intermittent period T HBURST is within the hearing range of the human ear.
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the third conduction number N3, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period is the third current peak value I Lm_R3 .
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent period T HBURST is within the human ear hearing range is further optimized, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the above embodiments are all based on the current interval where the current output voltage is in the low voltage interval L, and the converter 1 is controlled to be in the CRM mode or the intermittent wave mode according to the current interval where the current output current Io is located.
  • the following is a detailed introduction in combination with the change trend of the output current of the converter 1.
  • the converter 1 switches from the CRM mode to the HBURST mode; in order to further improve the efficiency of the converter 1 under extremely light load conditions, after the converter 1 is in the HBURST mode, when the output current of the converter 1 drops to the third switching current threshold Io4 , the converter 1 switches from the HBURST mode to the LBURST mode.
  • the converter 1 switches from the LBURST mode to the HBURST mode; when the output current of the converter 1 rises to the first switching current threshold Io3 , the converter 1 switches from the HBURST mode to the CRM mode.
  • the first switching current threshold I o2 corresponding to the medium voltage interval M is less than the first switching current threshold I o1 corresponding to the high voltage interval H and is greater than the first switching current threshold I o3 corresponding to the low voltage interval L.
  • the mode switching point when the output voltage is in the medium voltage interval M is less than the mode switching point when the output voltage is in the high voltage interval H, and is greater than the mode switching point when the output voltage is in the low voltage interval L.
  • the first conduction number N2 corresponding to the medium voltage interval M is less than the first conduction number N1 corresponding to the high voltage interval H and is greater than the third conduction number N3 corresponding to the low voltage interval L
  • the first current peak value I Lm_R2 corresponding to the medium voltage interval M is less than the first current peak value I Lm_R1 corresponding to the high voltage interval H and is greater than the third current peak value I Lm_R3 corresponding to the low voltage interval L.
  • the working parameters when entering the HBURST mode are also gradually reduced, wherein the working parameters are the conduction times of the switch tube within a high frequency gap cycle and/or the current peak value of the excitation inductance.
  • the working parameters when entering the HBURST mode are referred to as the HBURST mode entry point below.
  • the HBURST mode entry point when the output voltage is in the medium voltage interval M is less than the HBURST mode entry point when the output voltage is in the high voltage interval H, and is greater than the HBURST mode entry point when the output voltage is in the low voltage interval L.
  • the mode switching point and HBURST mode entry point of the converter 1 when the output voltage is in the medium voltage interval M are lower than when the output voltage is in the high voltage interval H, compared with the same mode switching point and HBURST mode entry point for different output voltages, the mode switching point of the present application when the output voltage is in the medium voltage interval M is lower and the HBURST mode entry point is smaller, which can reduce the energy transmitted in each high-frequency intermittent cycle, thereby reducing the primary and secondary winding losses and the switch tube conduction losses, thereby improving the efficiency of the converter 1 in the HBURST mode.
  • the energy transmitted in each high-frequency intermittent cycle can be further reduced, thereby further reducing the primary and secondary winding losses and the switch tube conduction losses, thereby further improving the efficiency of the converter 1 in the HBURST mode.
  • the HBURST mode frequency (the frequency of the high-frequency intermittent cycle) can be reduced to a lower level to reach the load point corresponding to the audible frequency point of the human ear, thereby optimizing the power supply ripple under extremely low loads.
  • the converter 1 can adjust the mode switching point and the HBURST mode entry point of the converter 1 according to different output voltages, thereby reducing the primary and secondary winding losses and the switch tube conduction losses, thereby optimizing the efficiency of the converter 1 under the full range of output voltages.
  • the converter 1 when the converter 1 is in the HBURST mode, it can also adjust the number of switch tube conduction times and/or the current peak of the excitation inductance in a high-frequency intermittent cycle according to load changes, thereby reducing the output voltage ripple under extremely light load conditions.
  • the controller 12 obtains the current switching frequency and the current output voltage of the converter 1, and when the current switching frequency reaches the frequency threshold, obtains the first operating parameter of the converter 1 in the second operating mode according to the current output voltage, thereby controlling the converter 1 to switch from the first operating mode to the second operating mode based on the first operating parameter.
  • the first operating parameter includes the number of times the main switch tube S1 and the auxiliary switch tube S2 are turned on in a high-frequency intermittent cycle, or the current peak value of the excitation inductance in a high-frequency intermittent cycle.
  • the curve control unit 122 calculates the current output voltage V o of the converter 1 based on the voltage VR2 of the sampling resistor R 2 collected by the voltage sampling circuit 13. At the same time, the curve control unit 122 obtains the current switching frequency f SW of the converter 1. When the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the curve control unit 122 determines the first voltage interval where the output voltage V o of the converter 1 is located from the three voltage intervals (i.e., the high voltage interval H, the medium voltage interval M, and the low voltage interval L ) shown in FIG4, thereby determining the first operating parameter corresponding to the first voltage interval from the three operating parameters corresponding to the three voltage intervals.
  • the three voltage intervals i.e., the high voltage interval H, the medium voltage interval M, and the low voltage interval L
  • the converter 1 is controlled to switch from the CRM mode to the HBURST mode.
  • the operating parameter corresponding to the medium voltage interval M is less than the operating parameter corresponding to the high voltage interval H and greater than the operating parameter corresponding to the low voltage interval L.
  • the HBURST mode entry point when the output voltage is in the medium voltage interval M is smaller than the HBURST mode entry point when the output voltage is in the high voltage interval H, and is larger than the HBURST mode entry point when the output voltage is in the low voltage interval L.
  • the curve control unit 122 determines that the first voltage interval where the output voltage V o of the converter 1 is located is the high voltage interval H from the three voltage intervals shown in Figure 4.
  • the first switching current threshold, the second switching current threshold, the third switching current threshold and the fourth switching current threshold are Io1 , Io2 , Io4 and Io3 respectively
  • the first conduction number, the second conduction number, the third conduction number, the fourth conduction number, the fifth conduction number and the sixth conduction number are N1, N2, N3, N4, N5 and N6 respectively
  • the first current peak value, the second current peak value, the third current peak value, the fourth current peak value, the fifth current peak value and the sixth current peak value are I Lm_R1 , I Lm_R2 , I Lm_R3 , I Lm_R4 , I Lm_R5 and I Lm_R6 respectively.
  • Io1 > Io2 > Io3 >0, Io1 > Io4 >0, Io2 and Io4 are not equal.
  • I Lm_R1 >I Lm_R2 >I Lm_R6 >0, I Lm_R3 ⁇ I Lm_R4 >0, I Lm_R5 0, the values of I Lm_R1 , I Lm_R2 , I Lm_R3 , I Lm_R4 and I Lm_R6 satisfy the conditions that the switching frequency f SW of converter 1 is less than the maximum switching frequency f SW(MAX) and the frequency f HBURST of the high-frequency intermittent period T HBURST is outside the hearing range of the human ear.
  • the curve control unit 122 determines that the operating parameters corresponding to the high voltage interval H are the first conduction number N1 of the switch tube within a high frequency intermittent period T HBURST shown in FIG. 5 and/or the first current peak value ILm_R1 of the excitation inductor Lm , and sends the operating parameters corresponding to the high voltage interval H to the PWM control unit 121.
  • the PWM control unit 121 controls the conduction number N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N1 (such as 3), so that the converter 1 switches from the CRM mode to the HBURST mode.
  • the PWM control unit 121 After the conduction number N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is the first conduction number N1, the PWM control unit 121 compares the current output current I o of the converter 1 with the second switching current threshold I o2 and the fourth switching current threshold I o3 . When the current output current I o is greater than the second switching current threshold I o2 and less than or equal to the first switching current threshold I o1 , the PWM control unit 121 continues to control the conduction number N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N1.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to have a second conduction number N SW in one high-frequency intermittent period T HBURST (e.g., 2).
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to have a sixth conduction number N SW in one high-frequency intermittent period T HBURST (e.g., 1).
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss and improving the efficiency of the converter 1.
  • the converter 1 can adjust the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST based on the change of the load, to ensure output on demand and avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and improving the efficiency of the converter 1.
  • the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST also gradually decreases, so the output voltage ripple of the converter 1 under light load conditions can also be reduced, and the applicability is strong.
  • the working parameter corresponding to the high-voltage interval H may also be a first current peak value I Lm_R1 of the excitation inductance L m within a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R1 , thereby switching the converter 1 from the CRM mode to the HBURST mode.
  • I Lm PEAK
  • the PWM control unit 121 After the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R1 , the PWM control unit 121 compares the current output current I o of the converter 1 with the second switching current threshold value I o2 and the fourth switching current threshold value I o3 . When the current output current I o is greater than the second switching current threshold value I o2 and less than or equal to the first switching current threshold value I o1 , the PWM control unit 121 continues to control the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST to be the first current peak value I Lm_R1 .
  • the PWM control unit 121 controls the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent period T HBURST to be the second current peak value I Lm_R2 .
  • the PWM control unit 121 controls the current peak value I Lm(PEAK) of the excitation inductance L m within a high-frequency intermittent period T HBURST to be the sixth current peak value I Lm_R6 .
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss and improving the efficiency of the converter 1.
  • the converter 1 can adjust the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent cycle T HBURST based on the change of the load, to ensure the output on demand and avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and improving the efficiency of the converter 1.
  • the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent cycle T HBURST also gradually decreases, so the output voltage ripple of the converter 1 under light load conditions can also be reduced, and the applicability is strong.
  • the operating parameters corresponding to the high voltage interval H may also be a first current peak value I Lm — R1 of the excitation inductor L m in one high frequency intermittent period T HBURST , and a first conduction number N1 of the switch tube in one high frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N1, and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R1 , so that the converter 1 switches from the CRM mode to the HBURST mode.
  • the PWM control unit 121 compares the current output current I o of the converter 1 with the second switching current threshold value I o2 and the fourth switching current threshold value I o3 .
  • the PWM control unit 121 When the current output current I o is greater than the second switching current threshold I o2 and less than or equal to the first switching current threshold I o1 , the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N1, and continues to control the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST to be the first current peak value I Lm_R1 .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N2, and controls the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST to be the second current peak value I Lm_R2 .
  • the PWM control unit 121 controls the conduction times NSW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period THBURST to be a sixth conduction times N6, and controls the current peak value ILm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period THBURST to be a sixth current peak value ILm_R6 .
  • the above embodiments are all based on the current interval in which the current output current I o is located, and the converter 1 is controlled to be in the HBURST mode.
  • the converter 1 reduces the operating parameters in the HBURST mode during the process of reducing the output current. For example, when the output current drops to the second switching current threshold I o2 , the converter 1 reduces the number of switch-on times and/or the current peak value of the excitation inductor within a high-frequency intermittent period T HBURST.
  • the converter 1 further reduces the number of switch-on times and/or the current peak value of the excitation inductor within a high-frequency intermittent period T HBURST .
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss and improving the efficiency of the converter 1.
  • the converter 1 can adjust the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST and the current peak value I Lm (PEAK) of the excitation inductor L m based on the change of the load, so as to ensure the output on demand and avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and improving the efficiency of the converter 1.
  • the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST and the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent cycle T HBURST are gradually reduced, which can further reduce the energy output. Therefore, the output voltage ripple of the converter 1 under light load conditions can be further reduced, and the applicability is stronger.
  • the converter 1 When the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to be in the HBURST mode, and after the converter 1 is in the HBURST mode, the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the current output current I o .
  • the specific implementation method may be a combination of the following two optional embodiments:
  • the operating parameters corresponding to the high voltage interval H include a first conduction number N1 of the switch tube in a high frequency intermittent period T HBURST , and/or a first current peak value I Lm_R1 of the excitation inductor L m ;
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on a first number of times N1 in a high-frequency intermittent period T HBURST , and/or controls the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST to be the first current peak value I Lm_R1 .
  • the PWM control unit 121 controls the conduction times of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the second conduction times N2, and/or controls the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period T HBURST to be the second current peak value I Lm_R2 ; if the output current I o of the converter 1 is less than or equal to the fourth switching current threshold I o3 , then the conduction
  • the current peak value I Lm(PEAK) of the excitation inductance L m of HBURST is the sixth current peak value I Lm_R6 ; if the output current Io of the converter is greater than the second switching current threshold Io2 and less than or equal to the first switching current threshold Io1 , then the main switch tube S1 and the auxiliary switch tube S2 are controlled to be turned on the first number of times N1 in a high-frequency intermittent period T HBURST , and/or the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is controlled to be the first current peak value I Lm_R1 .
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on a first number of times N1 in a high-frequency intermittent period T HBURST , and/or controls the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST to be a third current peak value I Lm_R1 .
  • the PWM control unit 121 controls the conduction times of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the fourth conduction times N4, and/or controls the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period T HBURST to be the fourth current peak value I Lm_R4 ; and after the conduction times of the switch tube in one high-frequency intermittent period T HBURST are the fourth conduction times N4, and/or the current peak value I Lm(PEAK) of the
  • the specific implementation steps of controlling the converter 1 to be in the HBURST mode or the LBURST mode according to the current output current Io are all obtained based on the combination of the steps corresponding to the following five current intervals.
  • the controller 12 controls the number of conduction times NSW of the switch tube in a high-frequency intermittent period THBURST to be the first conduction number N1, and/or controls the current peak value ILm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period to be the first current peak value ILm_R1 .
  • the controller 12 controls the number of conduction times NSW of the switch tube in a high-frequency intermittent period THBURST to be the second conduction number N2, and/or controls the current peak value ILm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period to be the second current peak value ILm_R2 .
  • the controller 12 controls the number of conduction times NSW of the switch tube in a high-frequency intermittent period THBURST to be the first conduction number N1, and/or controls the excitation inductance Lm
  • the current peak value I Lm (PEAK) of the switch tube in a high-frequency intermittent cycle is the third current peak value I Lm_R1 .
  • the controller 12 controls the converter 1 to be in the LBURST mode based on the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST being the fourth conduction number N4, and/or the current peak value I Lm(PEAK) of the excitation inductor L m being the fourth current peak value I Lm_R4 .
  • the controller 12 controls the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST to be the sixth conduction number N6, and/or controls the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent cycle to be the sixth current peak value I Lm_R6 .
  • the PWM control unit 121 can select any current interval from the above overlapping multiple current intervals or a current interval that meets the actual working condition of the converter 1 as the target current interval, and when the current output current Io is located in the above overlapping current interval, control the converter 1 to execute the steps when the current output current Io is located in the target current interval. Based on this, it can be obtained that the control mode of the converter 1 in the HBURST mode or the LBURST mode is diverse and highly flexible. In addition, the size relationship between Io4 , Io2 and Io3 is diverse, so that the control mode of the converter 1 in the HBURST mode or the LBURST mode is more diverse and more flexible.
  • the converter 1 is described in the following by taking I o2 >I o3 >I o4 as an example to be in the HBURST mode or the LBURST mode.
  • I o2 >I o3 >I o4 it can be obtained that the first current interval (I o2 ,I o1 ] overlaps with the third current interval (I o4 ,I o1 ] and the overlapping current interval is (I o2 ,I o1 ].
  • the controller 12 can select the first current interval (I o2 ,I o1 ] or the third current interval (I o4 ,I o1 ] as the target current interval under the overlapping current interval (I o2 ,I o1 ].
  • This embodiment is introduced by taking the first current interval (I o2 ,I o1 ] as the target current interval under the overlapping current interval (I o2 ,I o1 ] as an example; the second current interval (I o3 ,I o2 ] overlaps with the third current interval (I o4 ,I o1 ] and the overlapping current interval is (I o3 ,I o2 ]).
  • the controller 12 can select the second current interval (I o3 ,I o2 ] or the third current interval (I o4 ,I o1 ] as the overlapping current interval (I o3 , I o2 ], the present embodiment takes the second current interval (I o3 , I o2 ] as the target current interval under the overlapping current interval (I o3 , I o2 ] as an example for introduction; the fifth current interval (0, I o3 ] overlaps with the third current interval (I o4 , I o1 ] and the overlapping current interval is (I o4 , I o3 ], the controller 12 can select the fifth current interval (0, I o3 ] or the third current interval (I o4 , I o1 ] as the target current interval under the overlapping current interval (I o4 , I o3 ], the present embodiment takes the fifth current interval (0, I o3 ] as the target current interval under the overlapping current interval (I o4
  • the curve control unit 122 determines that the first voltage interval where the output voltage V o of the converter 1 is located is the high-voltage interval H from the three voltage intervals shown in FIG4 . Further, the curve control unit 122 determines that the operating parameters corresponding to the high-voltage interval H are the first conduction times N1 of the switch tube and/or the first current peak value I Lm_R1 of the excitation inductance L m within a high-frequency intermittent period T HBURST shown in FIG5 , and sends the operating parameters to the PWM control unit 121.
  • the PWM control unit 121 controls the conduction number N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N1 (such as 3), so that the converter 1 switches from the CRM mode to the HBURST mode.
  • the PWM control unit 121 After the conduction number N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is the first conduction number N1, the PWM control unit 121 compares the current output current I o of the converter 1 with the second switching current threshold I o2 , the third switching current threshold I o4 and the fourth switching current threshold I o3 . When the current output current Io is less than or equal to the first switching current threshold Io1 and greater than the second switching current threshold Io2 , the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to have the first conduction number NSW in a high-frequency intermittent period THBURST , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o is less than or equal to the second switching current threshold I o2 and greater than the fourth switching current threshold I o3 , the PWM control unit 121 performs the above steps when the current output current I o is in the second current interval (I o3 , I o2 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the second conduction number N SW N2 (such as 2), and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the fourth switching current threshold I o3 and greater than the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the fifth current interval (0, I o3 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the sixth conduction number N6 (such as 1), and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the third switching current threshold I o4, the PWM control unit 121 performs the above steps when the current output current I o is in the fifth current interval (0, I o3 ], that is, the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST is controlled to be the sixth conduction number N6 (such as 1), and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the fifth conduction number N5 (i.e.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state all the time.
  • the converter 1 is in the LBURST mode.
  • the first working cycle number is a positive integer, and exemplarily, the first working cycle number is 3.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss and improving the efficiency of the converter 1.
  • the working mode of the converter 1 under extremely light load (that is, the output current I o is less than or equal to the third switching current threshold I o4 ) is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing the energy loss and the switch tube loss, and further improving the efficiency of the converter 1.
  • the output energy is further reduced. Therefore, this embodiment can further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the working parameter corresponding to the high-voltage interval H may also be a first current peak value I Lm_R1 of the excitation inductance L m within a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R1 , so that the converter 1 switches from the CRM mode to the HBURST mode.
  • the PWM control unit 121 compares the current output current I o of the converter 1 with the second switching current threshold value I o2 , the third switching current threshold value I o4 and the fourth switching current threshold value I o3 .
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1 so that the current peak value ILm(PEAK) of the excitation inductor Lm within a high-frequency intermittent period THBURST is the first current peak value ILm_R1 , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o is less than or equal to the second switching current threshold I o2 and greater than the fourth switching current threshold I o3 , the PWM control unit 121 performs the above steps when the current output current I o is in the second current interval (I o3 , I o2 ], that is, controls the on-time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period T HBURST is the second current peak value I Lm_R2 , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the fourth switching current threshold I o3 and greater than the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the fifth current interval (0, I o3] , that is, controls the on-time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period T HBURST is the sixth current peak value I Lm_R6, and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the fourth switching current threshold I o3 and greater than the third switching current threshold I o4, the PWM control unit 121 performs the above steps when the current output current I o is in the fifth current interval (0, I o3], that is, controls the on-time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period T HBURST is the sixth current peak value I Lm_R6 , and the converter 1 is still in the HBURST mode.
  • the first working cycle number is a positive integer, and illustratively, the first working cycle number is 3.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss and improving the efficiency of the converter 1.
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the output energy is further reduced. Therefore, this embodiment can further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the operating parameters corresponding to the high voltage interval H may also be a first current peak value I Lm — R1 of the excitation inductor L m in one high frequency intermittent period T HBURST , and a first conduction number N1 of the switch tube in one high frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N1 (such as 3), and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST is the first current peak value I Lm_R1 , so that the converter 1 switches from the CRM mode to the HBURST mode.
  • N1 such as 3
  • the PWM control unit 121 compares the current output current I o of the converter 1 with the second switching current threshold value I o2 , the third switching current threshold value I o4 and the fourth switching current threshold value I o3 .
  • the PWM control unit 121 When the current output current Io is less than or equal to the first switching current threshold Io1 and greater than the second switching current threshold Io2 , the PWM control unit 121 continues to control the conduction times NSW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period THBURST to be the first conduction times N1, and continues to control the conduction duration of the main switch tube S1 so that the current peak value ILm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period THBURST is the first current peak value ILm_R1 , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o is less than or equal to the second switching current threshold I o2 and greater than the fourth switching current threshold I o3 , the PWM control unit 121 performs the above steps when the current output current I o is in the second current interval (I o3 , I o2 ], that is, controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N2 (such as 2), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the second current peak value I Lm_R2 , and the converter 1 is still in the HBURST mode.
  • the second current interval I o3 , I o2
  • N2 such as 2
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the fourth switching current threshold I o3 and greater than the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the fifth current interval (0, I o3 ], that is, controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second current peak value I Lm_R2.
  • SW is the sixth conduction number N6 (such as 1), and the conduction time of the main switch tube S1 is controlled so that the current peak value I Lm (PEAK) of the excitation inductance L m in one high-frequency intermittent cycle T HBURST is the sixth current peak value I Lm_R6 , and the converter 1 is still in the HBURST mode.
  • N6 the sixth conduction number N6 (such as 1)
  • the converter 1 when the current output current I o of the converter 1 is less than or equal to the third switching current threshold value I o4 , the converter 1 is in the LBURST mode.
  • the first working cycle number is a positive integer, and illustratively, the first working cycle number is 3.
  • the above embodiments all control the converter 1 to be in the HBURST mode or the LBURST mode based on the current interval in which the current output current I o is located.
  • the following is an example description in combination with the change trend of the output current of the converter 1.
  • the converter 1 reduces the working parameters in the HBURST mode during the process of reducing the output current.
  • the converter 1 when the output current drops to the switching current threshold I o2 , the converter 1 reduces the number of switch-on times and/or the current peak value of the excitation inductance within a high-frequency intermittent period T HBURST ; when the output current continues to drop to the switching current threshold I o3 , the converter 1 further reduces the number of switch-on times and/or the current peak value of the excitation inductance within a high-frequency intermittent period T HBURST .
  • converter 1 switches from HBURST mode to LBURST mode; correspondingly, when the output current of converter 1 rises to the switching current threshold I o4 , converter 1 switches from LBURST mode to HBURST mode.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss, and thus improving the efficiency of the converter 1.
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the output energy is further reduced. Therefore, this embodiment can further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the converter 1 When the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to be in the HBURST mode, and after the converter 1 is in the HBURST mode, the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the frequency f HBURST of the high-frequency intermittent period T HBURST .
  • the specific implementation method may be a combination of the following two optional embodiments:
  • the operating parameters corresponding to the high voltage interval H include a first conduction number N1 of the switch tube in a high frequency intermittent period T HBURST , and/or a first current peak value I Lm_R1 of the excitation inductor L m ;
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on a first number of times N1 in a high-frequency intermittent period T HBURST , and/or controls the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST to be the first current peak value I Lm_R1 .
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on a third number of times N3 in a high-frequency intermittent period T HBURST , and/or controls the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST to be a third current peak value I Lm_R3 .
  • the PWM control unit 121 controls the conduction times of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the fourth conduction times N4, and/or controls the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period T HBURST to be the fourth current peak value
  • the curve control unit 122 determines that the first voltage interval where the output voltage V o of the converter 1 is located is the high-voltage interval H from the three voltage intervals shown in FIG4 . Further, the curve control unit 122 determines that the operating parameter corresponding to the high-voltage interval H is the first conduction number N1 of the switch tube within a high-frequency intermittent period T HBURST shown in FIG5 .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first number of conduction times N1 (such as 3), so that the converter 1 switches from the CRM mode to the HBURST mode.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on at a fourth turn-on number N SW N4 (such as 1) in a high-frequency intermittent cycle, and after the first working cycle number of the main switch tube S1 and the auxiliary switch tube S2 being turned on at the fourth turn-on number N4 in a high-frequency intermittent cycle, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on at a fifth turn-on number N5 (i.e., 0) in a high-frequency intermittent cycle, that is, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned off all the time.
  • a fourth turn-on number N SW N4 such as 1
  • N5 i.e., 0
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on a first number of times N SW in one high-frequency intermittent period T HBURST .
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the first number of times N SW in a high-frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period to be the second conduction times N2 (such as 2), and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the second number of times N SW in one high-frequency intermittent period T HBURST as N2.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on a second number of times N SW in a high-frequency intermittent period T HBURST is N2.
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to have a sixth conduction number N SW in a high-frequency intermittent period, and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 controls the converter 1 to be in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to be turned on the sixth number of times N SW in one high-frequency intermittent period T HBURST , which is N6.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss, and thus improving the efficiency of the converter 1.
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent cycle T HBURST is within the human ear hearing range is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing the energy loss and the switch tube loss, and thus further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the working parameter corresponding to the high-voltage interval H may also be the first current peak value I Lm_R1 of the excitation inductance L m in a high-frequency intermittent cycle.
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high frequency intermittent cycle is the first current peak value I Lm_R1 , so that the converter 1 is in the HBURST mode.
  • the PWM control unit 121 controls the on-time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fourth current peak value I Lm_R4 , and after the first working cycle number of the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fourth current peak value I Lm_R4 , the PWM control unit 121 controls the on-time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fifth current peak value I Lm_R5 (i.e., 0), that is, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state all the time.
  • I Lm_R5 i.e., 0
  • the converter 1 when the frequency f HBURST of the high-frequency intermittent cycle T HBURST is within the hearing range of the human ear, the converter 1 is in the LBURST mode.
  • the PWM control unit 121 continues to control the on-time of the main switch S1 to make the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period the first current peak value I Lm_R1 .
  • the PWM control unit 121 continues to control the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period is the first current peak value I Lm_R1 .
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent cycle is the second current peak value I Lm_R2 , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 converter 1 When the frequency f HBURST of the high-frequency intermittent cycle T HBURST is When HBURST is within the hearing range of the human ear, the PWM control unit 121 converter 1 is in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the second current peak value I Lm_R2 .
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period is the second current peak value I Lm_R2 .
  • the PWM control unit 121 controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent cycle is the sixth current peak value I Lm_R6 , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 converter 1 When the frequency f HBURST of the high-frequency intermittent cycle T HBURST is When HBURST is within the hearing range of the human ear, the PWM control unit 121 converter 1 is in the LBURST mode.
  • the specific implementation method of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part in the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the conduction time of the main switch tube S1, so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the sixth current peak value I Lm_R6 .
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss and improving the efficiency of the converter 1.
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent cycle T HBURST is within the human ear hearing range is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing the energy loss and the switch tube loss, and further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the operating parameters corresponding to the high voltage interval H may also be a first current peak value I Lm — R1 of the excitation inductor L m in one high frequency intermittent period T HBURST , and a first conduction number N1 of the switch tube in one high frequency intermittent period T HBURST .
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be a first conduction times N1 (such as 3), and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period is the first current peak value I Lm_R1 , so that the converter 1 is in the HBURST mode.
  • N1 such as 3
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent cycle to be both the fourth conduction times N4 (such as 1), and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fourth current peak value I Lm_R4 , and after the first working cycle number in which the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fourth current peak value I Lm_R4 and the conduction times N SW of the switch tube is the fourth conduction times N4, the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent cycle to be both the fifth conduction times
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state all the time.
  • the converter 1 is in the LBURST mode.
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the first number of conduction times N1, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the first current peak value I Lm_R1 .
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction time N1, and continues to control the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period is the first current peak value I Lm_R1 .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle to be the second conduction number N2 (such as 2), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent cycle is the second current peak value I Lm_R2 , and the converter 1 is still in the HBURST mode.
  • N2 such as 2
  • the PWM control unit 121 calculates the frequency f HBURST of the high-frequency intermittent cycle T HBURST in which the number of conduction times N SW of the switch tube is the second conduction number N2 and the current peak value I Lm (PEAK) of the excitation inductor L m is the second current peak value I Lm_R2 .
  • the PWM control unit 121 and the converter 1 are in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N2, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period is the second current peak value I Lm_R2 .
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N2, and continues to control the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period is the second current peak value I Lm_R2 .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle to be the sixth conduction number N6 (such as 1), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent cycle is the sixth current peak value I Lm_R6 , and the converter 1 is still in the HBURST mode.
  • N6 such as 1
  • the PWM control unit 121 and the converter 1 are in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the sixth conduction times N6, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the sixth current peak value I Lm_R6 .
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss, and thus improving the efficiency of the converter 1.
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent period T HBURST is within the human ear hearing range is further optimized, so that the converter 1 is in the LBURST mode, thereby further reducing the energy loss and the switch tube loss, and thus further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the curve control unit 122 determines that the first voltage interval where the output voltage V o of the converter 1 is located is the medium voltage interval M from the three voltage intervals shown in Figure 4.
  • the first switching current threshold, the second switching current threshold and the third switching current threshold are I o2 , I o3 and I o4 respectively
  • the first conduction number, the second conduction number, the third conduction number, the fourth conduction number and the fifth conduction number are N2, N6, N3, N4 and N5 respectively
  • the first current peak value, the second current peak value, the third current peak value, the fourth current peak value and the fifth current peak value are I Lm_R2 , I Lm_R6 , I Lm_R3 , I Lm_R4 and I Lm_R5 respectively.
  • I o2 >I o3 >0, I o2 >I o4 >0, I o3 and I o4 are not equal.
  • N2 >N6, N3 ⁇ N4, N5 0, N2, N3, N4 and N6 are all positive integers.
  • I Lm_R2 >I Lm_R6 >0, I Lm_R3 ⁇ I Lm_R4 >0, I Lm_R5 0, the values of I Lm_R2 , I Lm_R3 , I Lm_R4 and I Lm_R6 satisfy the conditions that the switching frequency f SW of converter 1 is less than the maximum switching frequency f SW(MAX) and the frequency f HBURST of the high-frequency intermittent period T HBURST is outside the hearing range of the human ear.
  • the curve control unit 122 determines that the operating parameters corresponding to the medium voltage interval M are the first conduction number N2 of the switch tube within a high-frequency intermittent period T HBURST shown in FIG. 5 and/or the first current peak value I Lm — R2 of the excitation inductor L m , and sends the operating parameters to the PWM control unit 121 .
  • the following takes the working parameters corresponding to the medium voltage interval M as the first conduction number N2 of the switch tube in a high-frequency intermittent period T HBURST shown in FIG. 5 and the first current peak value I Lm_R2 of the excitation inductor L m as an example for introduction.
  • the PWM control unit 121 After receiving the working parameters corresponding to the medium voltage interval M, the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N2, and controls the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST to be the first current peak value I Lm_R2 .
  • the PWM control unit 121 compares the current output current I o of the converter 1 with the second switching current threshold value I o3 .
  • the PWM control unit 121 When the current output current I o is greater than the second switching current threshold I o3 and less than or equal to the first switching current threshold I o2 , the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction number N2, and continues to control the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST to be the first current peak value I Lm_R2 .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N6, and controls the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST to be the second current peak value I Lm_R6 .
  • the working parameter corresponding to the medium voltage interval M is the first conduction number N2 or the first current peak value I Lm_R2
  • the working principle of the converter 1 can refer to the description of this embodiment and will not be repeated here.
  • the above embodiments are all based on the current interval in which the current output current I o is located, and the converter 1 is controlled to be in the HBURST mode.
  • the following is an example introduction in combination with the change trend of the output current of the converter 1.
  • the converter 1 reduces the operating parameters in the HBURST mode during the process of reducing the output current. For example, when the output current drops to the second switching current threshold I o3 , the converter 1 reduces the number of conduction times of the switch tube within a high-frequency intermittent period T HBURST and/or the current peak value of the excitation inductance.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss and improving the efficiency of the converter 1.
  • the converter 1 can adjust the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST and the current peak value I Lm (PEAK) of the excitation inductor L m based on the change of the load, so as to ensure the output on demand and avoid the situation where the output is more than the load required, thereby reducing energy loss and switch tube loss, and improving the efficiency of the converter 1.
  • the number of conduction times N SW of the switch tube in a high-frequency intermittent cycle T HBURST and the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent cycle T HBURST are gradually reduced, which can further reduce the energy output. Therefore, the output voltage ripple of the converter 1 under light load conditions can be further reduced, and the applicability is stronger.
  • the converter 1 When the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to be in the HBURST mode, and after the converter 1 is in the HBURST mode, the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the current output current I o .
  • the specific implementation method may be a combination of the following two optional embodiments:
  • the working parameters corresponding to the medium voltage interval M include a first conduction number N2 of the switch tube in a high-frequency intermittent period T HBURST , and/or a first current peak value I Lm_R2 of the excitation inductor L m ;
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on a first number of times N2 in a high-frequency intermittent period T HBURST , and/or controls the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST to be the first current peak value I Lm_R2 .
  • the conduction times of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST are both the first conduction times N2, and/or the current peak value I Lm(PEAK) of the excitation inductor L m is the first current peak value I Lm_R2 , if the output current I o of the converter 1 is less than or equal to the second switching current threshold value I o3 , then the conduction times of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST are both the second conduction times N6, and/or the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period T HBURST is controlled to be the second current peak value I Lm_R6 ; if the output current I o of the converter is greater than the second switching current threshold value I o3 and less than or equal to the first switching current threshold value I o2 , then the conduction times of
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on a third number of times N2 in a high-frequency intermittent period T HBURST , and/or controls the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST to be a third current peak value I Lm_R2 .
  • the PWM control unit 121 controls the conduction times of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the fourth conduction times N4, and/or controls the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period T HBURST to be the fourth current peak value I Lm_R4 ; and after the conduction times of the switch tube in one high-frequency intermittent period T HBURST are the fourth conduction times N4, and/or the current peak value I Lm(PEAK) of the
  • the specific implementation steps of controlling the converter 1 to be in the HBURST mode or the LBURST mode according to the current output current Io are all obtained based on the combination of the steps corresponding to the following four current intervals.
  • the controller 12 controls the converter 1 to be in the LBURST mode based on the fact that the number of conduction times N SW of the switch tube in a high-frequency intermittent period T HBURST is the fourth conduction number N4, and/or the current peak value I Lm(PEAK) of the excitation inductor Lm is the fourth current peak value I Lm_R4 ;
  • the controller 12 controls the number of conduction times N SW of the switch tube in a high-frequency intermittent period T HBURST to be the second conduction number N6, and/or controls the current peak value I Lm(PEAK) of the excitation inductor Lm in a high-frequency intermittent period to be the second current peak value I Lm_R6 ; when the current output current Io is in the second current interval ( Io3 , Io2 ] or the sixth current interval ( Io4 , Io2
  • the PWM control unit 121 can select any current interval from the above overlapping multiple current intervals or a current interval that meets the actual working condition of the converter 1 as the target current interval, and when the current output current Io is located in the above overlapping current interval, control the converter 1 to execute the steps when the current output current Io is located in the target current interval. Based on this, it can be obtained that the control mode of the converter 1 in the HBURST mode or the LBURST mode is diverse and highly flexible. In addition, the size relationship between Io4 and Io3 is diverse, so that the control mode of the converter 1 in the HBURST mode or the LBURST mode is more diverse and more flexible.
  • the converter 1 is described in the following by taking I o3 >I o4 as an example to be in the HBURST mode or the LBURST mode.
  • I o3 >I o4 it can be obtained that the second current interval (I o4 ,I o2 ] overlaps with the sixth current interval (I o3 ,I o2 ] and the overlapping current interval is (I o3 ,I o2 ].
  • the controller 12 can select the second current interval (I o4 ,I o2 ] or the sixth current interval (I o4 ,I o2 ] as the target current interval under the overlapping current interval (I o3 ,I o2 ].
  • This embodiment is introduced by taking the second current interval (I o4 ,I o2 ] as the target current interval under the overlapping current interval (I o3 ,I o2 ] as an example; the fifth current interval (0,I o3 ] overlaps with the sixth current interval (I o4 ,I o2 ] and the overlapping current interval is (I o4 ,I o3 ].
  • the controller 12 can select the fifth current interval (0,I o3 ] or the sixth current interval (I o4 ,I o2 ] as the overlapping current interval (I o4 ,I o3 ], this embodiment takes the fifth current interval (0, I o3 ] as the target current interval under the overlapping current interval (I o4 , I o3 ] as an example for introduction; the fifth current interval (0, I o3 ] overlaps with the fourth current interval (0, I o4 ] and the overlapping current interval is (0, I o4 ], the controller 12 can select the fifth current interval (0, I o3 ] or the fourth current interval (0, I o4 ] as the target current interval under the overlapping current interval (0, I o4 ], and this embodiment takes the fourth current interval (0, I o4 ] as the target current interval under the overlapping current interval (0, I o4 ] as an example for introduction.
  • the curve control unit 122 determines that the first voltage interval where the output voltage V o of the converter 1 is located is the medium voltage interval M from the three voltage intervals shown in FIG4 . Further, the curve control unit 122 determines that the operating parameters corresponding to the medium voltage interval M are the first conduction times N2 of the switch tube within a high-frequency intermittent period T HBURST shown in FIG5 and/or the first current peak value I Lm_R2 of the excitation inductance L m , and sends the operating parameters to the PWM control unit 121.
  • the following takes the working parameters corresponding to the medium voltage interval M as the first conduction number N2 of the switch tube in a high-frequency intermittent period T HBURST shown in FIG. 5 and the first current peak value ILm_R2 of the excitation inductor Lm as an example for introduction.
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle T HBURST to be the first conduction number N2 (such as 2), and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent cycle T HBURST is the first current peak value I Lm_R2 , so that the converter 1 switches from the CRM mode to the HBURST mode.
  • N2 such as 2
  • the PWM control unit 121 compares the current output current I o of the converter 1 with the second switching current threshold value I o3 and the third switching current threshold value I o4 .
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to have a first conduction number NSW in a high-frequency intermittent period THBURST , and continues to control the conduction duration of the main switch tube S1 so that the current peak value ILm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period THBURST is the first current peak value ILm_R2 , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the second switching current threshold I o3 and greater than the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the fifth current interval (0, I o3 ], that is, controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N6 (such as 1), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST is the second current peak value I Lm_R6 , and the converter 1 is still in the HBURST mode.
  • the PWM control unit 121 When the current output current I o of the converter 1 is less than or equal to the third switching current threshold I o4 , the PWM control unit 121 performs the above steps when the current output current I o is in the fourth current interval (0, I o4 ], that is, controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second current peak value I Lm_R6.
  • the first working cycle number is a positive integer, and illustratively, the first working cycle number is 3.
  • the working parameter corresponding to the medium voltage interval M is the first conduction number N2 or the first current peak value I Lm_R2
  • the working principle of the converter 1 can refer to the description of this embodiment and will not be repeated here.
  • the above embodiments all control the converter 1 to be in the HBURST mode or the LBURST mode based on the current interval in which the current output current I o is located.
  • the following is an example description in combination with the change trend of the output current of the converter 1.
  • the converter 1 reduces the working parameters in the HBURST mode during the process of reducing the output current. For example, when the output current continues to decrease to the switching current threshold I o3 , the converter 1 reduces the number of conduction times of the switch tube and/or the current peak value of the excitation inductance within a high-frequency intermittent cycle T HBURST .
  • the converter 1 switches from the HBURST mode to the LBURST mode; correspondingly, when the output current of the converter 1 rises to the switching current threshold I o4 , the converter 1 switches from the LBURST mode to the HBURST mode.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss, and thus improving the efficiency of the converter 1.
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the output energy is further reduced. Therefore, this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the converter 1 When the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to be in the HBURST mode, and after the converter 1 is in the HBURST mode, the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the frequency f HBURST of the high-frequency intermittent period T HBURST .
  • the specific implementation method may be a combination of the following two optional embodiments:
  • the working parameters corresponding to the medium voltage interval M include a first conduction number N2 of the switch tube in a high-frequency intermittent period T HBURST , and/or a first current peak value I Lm_R2 of the excitation inductor L m ;
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on a first number of times N2 in a high-frequency intermittent period T HBURST , and/or controls the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST to be the first current peak value I Lm_R2 .
  • the PWM control unit 121 continues to control the conduction times of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the first conduction times N2, and/or, controls the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period T HBURST to be the first current peak value I Lm_R2 ; if the output current I o of the converter 1 is less than or equal to the second switching current threshold I o3 , then
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be turned on a third number of times N3 in a high-frequency intermittent period T HBURST , and/or controls the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST to be a third current peak value I Lm_R3 .
  • the PWM control unit 121 controls the conduction times of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the fourth conduction times N4, and/or controls the current peak value I Lm(PEAK) of the excitation inductor L m in one high-frequency intermittent period T HBURST to be the fourth current peak value
  • the curve control unit 122 determines that the first voltage interval where the output voltage V o of the converter 1 is located is the medium voltage interval M from the three voltage intervals shown in FIG4 . Further, the curve control unit 122 determines that the operating parameters corresponding to the medium voltage interval M are the first conduction times N2 of the switch tube within a high-frequency intermittent period T HBURST shown in FIG5 and/or the first current peak value I Lm_R2 of the excitation inductance L m , and sends the operating parameters to the PWM control unit 121.
  • the following takes the working parameters corresponding to the medium voltage interval M as the first conduction number N2 of the switch tube in a high-frequency intermittent period T HBURST shown in FIG. 5 and the first current peak value ILm_R2 of the excitation inductor Lm as an example for introduction.
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction times N2 (such as 2), and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period is the first current peak value I Lm_R2 , so that the converter 1 is in the HBURST mode.
  • N2 such as 2
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent cycle to be both the fourth conduction times N4 (such as 1), and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fourth current peak value I Lm_R4 , and after the first working cycle number in which the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fourth current peak value I Lm_R4 and the conduction times N SW of the switch tube is the fourth conduction times N4, the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent cycle to be both the fifth conduction times
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state all the time.
  • the converter 1 is in the LBURST mode.
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the first number of conduction times N2, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the first current peak value I Lm_R2 .
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the first conduction time N2, and continues to control the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent period is the first current peak value I Lm_R2 .
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle to be the second conduction number N6 (such as 1), and controls the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductor L m in a high-frequency intermittent cycle is the second current peak value I Lm_R6 , and the converter 1 is still in the HBURST mode.
  • N6 such as 1
  • the PWM control unit 121 and the converter 1 are in the LBURST mode.
  • the specific implementation of the PWM control unit 121 controlling the converter 1 to be in the LBURST mode can be found in the description of the corresponding part of the above embodiment, which will not be repeated here.
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the second conduction number N6, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period is the second current peak value I Lm_R6 .
  • the working parameter corresponding to the medium voltage interval M is the first conduction number N2 or the first current peak value I Lm_R2
  • the working principle of the converter 1 can refer to the description of this embodiment and will not be repeated here.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss, and thus improving the efficiency of the converter 1.
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent period T HBURST is within the human ear hearing range is further optimized, so that the converter 1 is in the LBURST mode, thereby further reducing the energy loss and the switch tube loss, and thus further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the curve control unit 122 determines that the first voltage interval where the output voltage V o of the converter 1 is located is the low voltage interval L from the three voltage intervals shown in Figure 4.
  • the first switching current threshold and the second switching current threshold are I o3 and I o4 respectively
  • the third conduction number, the fourth conduction number and the fifth conduction number are N3, N4 and N5 respectively
  • the third current peak value, the fourth current peak value and the fifth current peak value are I Lm_R3 , I Lm_R4 and I Lm_R5 respectively.
  • N3 ⁇ N4, N5 0, N3 and N4 are both positive integers.
  • I Lm_R3 ⁇ I Lm_R4 >0, I Lm_R5 0, and the values of I Lm_R3 and I Lm_R4 meet the conditions that the switching frequency f SW of the converter 1 is less than the maximum switching frequency f SW(MAX) and the frequency f HBURST of the high-frequency intermittent period T HBURST is outside the hearing range of the human ear.
  • the curve control unit 122 determines that the operating parameters corresponding to the low voltage interval L are the third conduction number N3 of the switch tube within a high frequency intermittent period T HBURST shown in FIG. 5 and/or the third current peak value I Lm — R3 of the excitation inductor L m , and sends the operating parameters to the PWM control unit 121 .
  • the following takes the working parameters corresponding to the low voltage interval L as the third conduction number N3 of the switch tube within a high-frequency intermittent period T HBURST (i.e., N6 as shown in Figure 5) and the third current peak value I Lm_R3 of the excitation inductor Lm (i.e., I Lm_R6 as shown in Figure 5) as an example for introduction.
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the third conduction times N3, and controls the current peak value I Lm(PEAK) of the excitation inductance L m in a high-frequency intermittent period T HBURST to be the third current peak value I Lm_R3 .
  • the working parameter corresponding to the low voltage interval L is the third conduction number N3 or the third current peak value I Lm_R3
  • the working principle of the converter 1 can refer to the description of this embodiment and will not be repeated here.
  • controlling the converter 1 to switch from the CRM mode to the HBURST mode can effectively reduce the switching frequency f SW of the converter 1 , thereby reducing switching losses and improving the efficiency of the converter 1 .
  • the converter 1 When the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to be in the HBURST mode. After the converter 1 is in the HBURST mode, the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the current output current I o :
  • the curve control unit 122 determines from the three voltage intervals shown in FIG4 that the first voltage interval in which the output voltage V o of the converter 1 is located is the low voltage interval L. Further, the curve control unit 122 determines that the operating parameters corresponding to the low voltage interval L are the third conduction times N3 (i.e., N6 shown in FIG5 ) of the switch tube within a high-frequency intermittent period T HBURST and/or the third current peak value I Lm_R3 (i.e., I Lm_R6 shown in FIG5 ) of the excitation inductance L m , and sends the operating parameters to the PWM control unit 121.
  • N3 i.e., N6 shown in FIG5
  • I Lm_R3 i.e., I Lm_R6 shown in FIG5
  • the following takes the working parameters corresponding to the low voltage interval L as the third conduction number N3 of the switch tube in one high-frequency intermittent period T HBURST and the third current peak value I Lm_R3 of the excitation inductor L m as an example for introduction.
  • the PWM control unit 121 controls the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent cycle T HBURST to be the third conduction number N3 (such as 1), and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductor L m in a high-frequency intermittent cycle T HBURST is the third current peak value I Lm_R3 , so that the converter 1 switches from the CRM mode to the HBURST mode.
  • N3 such as 1
  • the PWM control unit 121 compares the current output current I o of the converter 1 with the second switching current threshold value I o4 .
  • the PWM control unit 121 continues to control the main switch tube S1 and the auxiliary switch tube S2 to have a third conduction number NSW in a high-frequency intermittent period THBURST , and continues to control the conduction duration of the main switch tube S1 so that the current peak value ILm(PEAK) of the excitation inductance Lm in a high-frequency intermittent period THBURST is the third current peak value ILm_R3 , and the converter 1 is still in the HBURST mode.
  • the conduction time of the main switch tube S1 is controlled so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent cycle is the fifth current peak value I Lm_R5 (i.e. 0), that is, the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state.
  • the first working cycle number is a positive integer, and illustratively, the first working cycle number is 3.
  • the working parameter corresponding to the low voltage interval L is the third conduction number N3 or the third current peak value I Lm_R3
  • the working principle of the converter 1 can refer to the description of this embodiment and will not be repeated here.
  • the above embodiments all control the converter 1 to be in the HBURST mode or the LBURST mode based on the current interval in which the current output current I o is located.
  • the following is an example introduction in combination with the change trend of the output current of the converter 1.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss, and thus improving the efficiency of the converter 1.
  • the working mode of the converter 1 under extremely light load conditions is further optimized in this embodiment, so that the converter 1 is in the LBURST mode, thereby further reducing energy loss and switch tube loss, and further improving the efficiency of the converter 1.
  • the output energy is further reduced. Therefore, this embodiment can not only reduce the output voltage ripple of the converter 1 under light load conditions, but also further reduce the output voltage ripple of the converter 1 under extremely light load conditions, and has stronger applicability.
  • the converter 1 When the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to be in the HBURST mode. After the converter 1 is in the HBURST mode, the converter 1 is controlled to be in the HBURST mode or the LBURST mode according to the frequency f HBURST of the high-frequency intermittent period T HBURST :
  • the curve control unit 122 determines from the three voltage intervals shown in FIG4 that the first voltage interval in which the output voltage V o of the converter 1 is located is the low voltage interval L. Further, the curve control unit 122 determines that the operating parameters corresponding to the low voltage interval L are the third conduction times N3 (i.e., N6 shown in FIG5 ) of the switch tube within a high-frequency intermittent period T HBURST and/or the third current peak value I Lm_R3 (i.e., I Lm_R6 shown in FIG5 ) of the excitation inductance L m , and sends the operating parameters to the PWM control unit 121.
  • N3 i.e., N6 shown in FIG5
  • I Lm_R3 i.e., I Lm_R6 shown in FIG5
  • the following takes the working parameters corresponding to the low voltage interval L as the third conduction number N3 of the switch tube in one high-frequency intermittent period T HBURST and the third current peak value I Lm_R3 of the excitation inductor L m as an example for introduction.
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in a high-frequency intermittent period T HBURST to be the third conduction times N3 (such as 1), and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm (PEAK) of the excitation inductance L m in a high-frequency intermittent period is the third current peak value I Lm_R3 , so that the converter 1 is in the HBURST mode.
  • N3 such as 1
  • the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent cycle to be both the fourth conduction times N4 (such as 1), and controls the conduction duration of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fourth current peak value I Lm_R4 , and after the first working cycle number in which the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent cycle is the fourth current peak value I Lm_R4 and the conduction times N SW of the switch tube is the fourth conduction times N4, the PWM control unit 121 controls the conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent cycle to be both the fifth conduction times
  • the PWM control unit 121 controls the main switch tube S1 and the auxiliary switch tube S2 to be in the off state all the time.
  • the converter 1 is in the LBURST mode.
  • the PWM control unit 121 continues to control the number of conduction times N SW of the main switch tube S1 and the auxiliary switch tube S2 in one high-frequency intermittent period T HBURST to be the third number of conduction times N3, and continues to control the conduction time of the main switch tube S1 so that the current peak value I Lm(PEAK) of the excitation inductance L m in one high-frequency intermittent period is the third current peak value I Lm_R3 .
  • the working parameter corresponding to the medium voltage interval M is the third conduction number N3 or the third current peak value I Lm_R3
  • the working principle of the converter 1 can refer to the description of this embodiment and will not be repeated here.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 is controlled to switch from the CRM mode to the HBURST mode, which can effectively reduce the switching frequency f SW of the converter 1, thereby reducing the switching loss, and thus improving the efficiency of the converter 1.
  • the working mode of the converter 1 when the frequency f HBURST of the high-frequency intermittent period T HBURST is within the human ear hearing range is further optimized, so that the converter 1 is in the LBURST mode, thereby further reducing the energy loss and the switch tube loss, and thus further improving the efficiency of the converter 1.
  • the converter 1 is in the LBURST mode, which can effectively reduce the switching noise of the converter 1.
  • the converter 1 when the current switching frequency f SW reaches the frequency threshold f SW (MAX) , the converter 1 can adjust the HBURST mode entry point of the converter 1 according to different output voltages, thereby reducing the primary and secondary winding losses and the switch tube conduction losses, thereby optimizing the efficiency of the converter 1 under the full range of output voltages.
  • the converter 1 when the converter 1 is in the HBURST mode, it can also adjust the number of switch tube conduction times and/or the current peak of the excitation inductor in a high-frequency intermittent cycle according to load changes, thereby reducing the output voltage ripple under extremely light load conditions.
  • FIG8a is another structural schematic diagram of the converter provided by the present application.
  • the converter 1 includes a main switch tube S1, an auxiliary switch tube S2, a transformer 11, a controller 12 and a voltage sampling circuit 13.
  • the transformer 11 includes a primary winding NP , a secondary winding NS , an auxiliary winding NA , an iron core T1 , an iron core T2 , an excitation inductance Lm , a resonant inductance Lr and a resonant capacitor Cr , the primary winding NP and the secondary winding NS are both coupled to the iron core T1 , and the auxiliary winding NA and the secondary winding NS are both coupled to the iron core T2 .
  • the voltage sampling circuit 13 includes sampling resistors R3 and R4 , one end of the sampling resistor R3 is connected to the same-name end of the auxiliary winding NA , the other end of the sampling resistor R3 is connected to the opposite-name end of the auxiliary winding NA through the sampling resistor R4 , and the connection point between the sampling resistors R3 and R4 is connected to the controller 12.
  • the specific connection mode inside the transformer 11 and the specific connection mode of other parts in the converter 1 can refer to the description of the corresponding parts in the embodiment shown in FIG. 3 a , which will not be repeated here.
  • the controller 12 may be the controller 12 of FIG8b.
  • the controller 12 includes an input terminal VBULK, an input terminal FB, an input terminal AUX, an output terminal MDRV, an output terminal SDRV, a PWM control unit 121, and a curve control unit 122.
  • the input terminal AUX is connected to the connection point between the sampling resistors R3 and R4 .
  • the specific connection mode between other parts in the controller 12 and each part in the converter 1 refers to the description of the corresponding part in the embodiment shown in FIG3b, which will not be repeated here.
  • the voltage sampling circuit 13 starts to collect the voltage VR4 of the sampling resistor R4 in real time, and outputs the voltage VR4 of the sampling resistor R4 to the input terminal AUX of the controller 12.
  • the voltage VR4 of the sampling resistor R4 can represent the voltage of the auxiliary winding NA .
  • the curve control unit 122 controls the converter 1 to switch between the first working mode and the second working mode based on the current output voltage V0 and the current output current I0 , or based on the current output voltage V0 and the current switching frequency fSW .
  • the converter 1 can optimize the efficiency of the power adapter under the full range of output voltage by adjusting the mode switching point or the HBURST mode entry point based on the output voltage, and has high flexibility.
  • FIG. 9 is a schematic diagram of the efficiency of the converter under different output voltages provided by the present application.
  • the present application selects a converter 1 with an input voltage of 400V and an output voltage of 5-20V to illustrate the efficiency of the converter 1 at output voltages of 20V, 12V and 5V respectively.
  • the efficiency curve of the converter 1 provided by the present application i.e., the variable curve of the output voltage and output current in FIG. 9 being 20V and 7.5A respectively
  • the efficiency curve of the converter using the same mode cut-in point for different output voltages i.e., the fixed curve of the output voltage and output current in FIG. 9 being 20V and 7.5A respectively.
  • the efficiency of the converter 1 provided by the present application is the same as the efficiency of the converter using the same mode switching point. As the load increases, the efficiency of the converter 1 provided by the present application is significantly higher than the efficiency of the converter using the same mode switching point.
  • the efficiency curve of the converter 1 provided by the present application i.e., the variable curve with the output voltage and output current of 12V and 3A in FIG9
  • the efficiency curve of the converter with the same mode cut-in point for different output voltages i.e., the fixed curve with the output voltage and output current of 12V and 3A in FIG9 ).
  • the efficiency of the converter 1 provided by the present application is always significantly higher than the efficiency of the converter with the same mode switching point.
  • the efficiency curve of the converter 1 provided by the present application i.e., the variable curve with the output voltage and output current of 5V and 3A in FIG9
  • the efficiency curve with the same mode cut-in point for different output voltages i.e., the fixed curve with the output voltage and output current of 5V and 3A in FIG9 ).
  • the efficiency of the converter 1 provided by the present application is always significantly higher than the efficiency of the converter with the same mode switching point, and the efficiency of the converter 1 provided by the present application can reach more than 88.6%, even up to 91.7%. It can be seen that the output voltage of the converter 1 provided in the present application can significantly improve the efficiency of the converter 1 regardless of high voltage, medium voltage or low voltage, and the efficiency optimization effect of the converter 1 is most significant when the output voltage is low voltage.
  • FIG. 10 is a flow chart of a control method for a converter provided by the present application.
  • the control method for a converter provided by an embodiment of the present application is applicable to the controller 12 in the converter 1 shown in FIG. 3a to FIG. 8b .
  • the control method for a converter may include the following steps:
  • the mode switching parameter is a first current threshold.
  • the mode switching parameter is a first operating parameter of the converter in the second operating mode.
  • the controller in the converter obtains the output voltage and switching frequency of the converter, and obtains the first operating parameter according to the output voltage when the switching frequency reaches the frequency threshold.
  • the first operating parameter includes the number of times the main switch tube and the auxiliary switch tube are turned on in one working cycle of the converter, or the current peak value of the excitation inductance in one working cycle.
  • the switching frequency of the converter in the first working mode, is negatively correlated with the output current of the converter, and in the second working mode, the switching frequency of the converter remains unchanged within one working cycle of the converter.
  • a controller in the converter compares the output current of the converter with a first switching current threshold, and controls the converter to switch between the first operating mode and the second operating mode according to the comparison result.
  • the controller in the converter controls the converter to switch from the first operating mode to the second operating mode based on the first operating parameter.
  • the converter can optimize the efficiency of the converter under the full range of output voltages by adjusting the mode switching point of the converter 1 based on the output voltage, or by adjusting the operating parameters of the converter to switch from the first operating mode to the second operating mode based on the output voltage, with high flexibility.
  • FIG. 11 is a schematic diagram of a structure of a converter provided by the present application.
  • the terminal device includes a converter 1 and a battery 2.
  • the converter 1 is connected to the battery 2 for charging the battery 2.
  • the terminal device provided by the present application may be a smart phone, a tablet computer, a smart speaker, a wearable device, etc.
  • the converter 1 in the terminal device converts the first DC voltage input by the external DC power supply into a second DC voltage, and outputs the second DC voltage to the battery 2, thereby supplying power to the battery 2.
  • the converter 1 obtains its own current output voltage, and obtains a mode switching parameter based on the current output voltage.
  • the converter 1 controls the converter 1 to switch between the first working mode and the second working mode according to the mode switching parameter, wherein the switching frequency of the converter 1 in the first working mode is negatively correlated with the output current of the converter 1, and the switching frequency of the converter remains unchanged within one working cycle of the converter 1 in the second working mode.
  • converter 1 can optimize the efficiency of converter 1 under the full range of output voltages by adjusting the mode switching point of converter 1 based on the output voltage, or by adjusting the working parameters of converter 1 to switch from the first working mode to the second working mode based on the output voltage, thereby optimizing the working efficiency of the terminal device with high flexibility.

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Abstract

本申请提供了一种变换器及其控制方法，该变换器包括主开关管、辅开关管、变压器和控制器。在变换器工作后，控制器获得变换器的输出电压，并基于变换器的输出电压得到模式切换参数；根据模式切换参数控制变换器在第一工作模式与第二工作模式之间切换。采用本申请，可优化变换器在全范围输出电压下的效率。

Description

变换器及其控制方法 技术领域
本申请涉及电源技术领域，尤其涉及一种变换器及其控制方法。
背景技术
为满足不同负载下的效率要求，不对称半桥(Asymmetric Half Bridge，AHB)变换器通常采用脉冲宽度调制(Pulse Width Modulation，PWM)模式、脉冲频率调制(Pulse Frequency Modulation，PFM)模式、突发调制模式(Burst-Mode)或者上述三种模式相结合方案。其中，PWM模式是固定变换器的开关频率，通过控制励磁电流等实现对输出电压的调节；PFM模式是通过改变开关频率的方式实现对输出电压的调节；Burst-Mode是通过控制变换器是否执行开关动作实现对输出电压的调节。
目前，AHB变换器主要是基于AHB变换器的输入电压和负载控制AHB变换器的工作模式。具体的，当AHB变换器的负载大于或者等于AHB变换器的输入电压对应的第一负载设定值时，AHB变换器工作于固定开关频率的不对称半桥反激模式，其中，AHB变换器的输入电压越高，第一负载设定值越大；当上述负载小于第一负载设定值且大于第二负载设定值时，AHB变换器工作于钳位不对称半桥反激模式，且AHB变换器的开关频率随着负载减小而线性下降；当上述负载小于第二负载设定值时，AHB变换器工作于间歇发波模式。由于上述控制方式中，模式切换点仅与输入电压和负载有关，因此，在需要AHB变换器宽范围输出时，上述控制方式针对所有输出电压的模式切换点均相同，会导致部分输出电压下AHB变换器的效率低下。
发明内容
本申请提供了一种变换器及其控制方法，可优化变换器在全范围输出电压下的效率。
第一方面，本申请提供了一种变换器，该变换器包括主开关管、辅开关管、变压器和控制器。其中，主开关管和辅开关管串联在变换器的输入端和参考地之间，变压器的输入端分别连接至辅开关管的两端，变压器的输出端连接变换器的输出端。在变换器工作后，控制器获得变换器的输出电压，并基于变换器的输出电压得到模式切换参数；根据模式切换参数控制变换器在第一工作模式与第二工作模式之间切换，其中，第一工作模式下变换器的开关频率的大小与变换器的输出电流的大小负相关，第二工作模式下在变换器的一个工作周期内变换器的开关频率不变。由于变换器(如AHB变换器)的开关损耗常与输出电压强相关，本申请提供的变换器可以根据不同输出电压调整自身在不同工作模式之间切换的模式切换参数，也即变换器根据不同输出电压调整自身的工作模式，或者变换器调整自身从第一工作模式切换至第二工作模式下的工作参数，以减小开关损耗，因此可优化变换器在全范围输出电压下的效率。
结合第一方面，在第一种可能的实施方式中，模式切换参数为第一电流阈值。控制器比较变换器的输出电流与第一切换电流阈值的大小，并根据比较结果控制变换器在第一工作模式与第二工作模式之间切换。本申请提供的变换器可以根据不同输出电压调整自身在不同工作模式之间切换的模式切换点(即第一切换电流阈值)，也即变换器根据不同输出电 压调整自身的工作模式以减小开关损耗，因此可优化变换器在全范围输出电压下的效率。
结合第一方面第一种可能的实施方式，在第二种可能的实施方式中，控制器基于输出电压，从多个电压区间中得到输出电压所在的第一电压区间，并从电压区间对应的多个切换电流阈值中得到第一电压区间对应的第一切换电流阈值，其中，多个电压区间与多个切换电流阈值一一对应。具体来讲，变换器的输出电压所在第一电压区间的档位越高，则第一电压区间对应的第一切换电流阈值越大，从而可使变换器的开关频率和工作频率维持在相对合适区间，进而避免变换器的开关频率过高导致变换器的效率过低的情况，或者避免变换器的开关频率过低导致变换器的工作频率进入音频噪声的情况。
结合第一方面第一种可能的实施方式或者第二种可能的实施方式，在第三种可能的实施方式中，控制器在输出电流小于或者等于第一切换电流阈值且大于第二切换电流阈值时，控制主开关管和辅开关管在变换器的一个工作周期的导通次数均为第一导通次数，以使变换器处于高频间歇发波HBURST模式。控制器还在输出电流小于或者等于第二切换电流阈值时，控制主开关管和辅开关管在一个工作周期的导通次数均为第二导通次数，其中，第二导通次数小于第一导通次数。可以理解的，在变换器处于HBURST模式的情况下，变换器可以基于负载(即输出电流)的变化调整开关管在上述工作周期内的导通次数,保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器的效率。此外，由于在负载逐渐变轻(即输出电流逐渐变小)的过程中，开关管在上述工作周期内的导通次数也逐渐减小，因此，还可降低轻载情况下变换器的输出电压纹波，适用性强。
结合第一方面第一种可能的实施方式或者第二种可能的实施方式，在第四种可能的实施方式中，变压器包括励磁电感。控制器在输出电流小于或者等于第一切换电流阈值且大于第二切换电流阈值时，控制励磁电感在变换器的一个工作周期的电流峰值为第一电流峰值，以使变换器处于HBURST模式。控制器还在输出电流小于或者等于第二切换电流阈值时，控制励磁电感在一个工作周期的电流峰值为第二电流峰值，其中，第二电流峰值小于第一电流峰值。可以理解的，在变换器处于HBURST模式的情况下，变换器可以基于负载的变化调整励磁电感在上述工作周期内的电流峰值,保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器的效率。此外，由于在负载逐渐变轻的过程中，励磁电感在上述工作周期内的电流峰值也逐渐减小，因此，还可降低轻载情况下变换器的输出电压纹波，适用性强。
结合第一方面第一种可能的实施方式或者第二种可能的实施方式，在第五种可能的实施方式中，控制器在输出电流小于或者等于第一切换电流阈值且大于第三切换电流阈值时，控制主开关管和辅开关管在变换器的一个工作周期的导通次数均为第三导通次数，以使变换器处于HBURST模式。控制器还在输出电流小于或者等于第三切换电流阈值时，控制主开关管和辅开关管在一个工作周期的导通次数均为第四导通次数，并在经过一个工作周期内的导通次数为第三导通次数的第一工作周期次数后，控制主开关管和辅开关管在一个工作周期的导通次数均为第五导通次数，以使变换器处于低频间歇发波LBURST模式，其中，第四导通次数小于或者等于第三导通次数且大于第五导通次数。可以理解的，在变换器处于HBURST模式后，本实施方式对极轻载(即输出电流小于或者等于第三切换电流阈值)情况下变换器的工作模式进行了优化，使变换器处于HBURST模式，以使输出能量得到进一步减少，从而不仅可降低能源损耗和开关管损耗以提高变换器的效率，而且可以降低极轻载情况下变换器的输出电压纹波。
结合第一方面第一种可能的实施方式或者第二种可能的实施方式，在第六种可能的实施方式中，变压器包括励磁电感。控制器在输出电流小于或者等于第一切换电流阈值且大于第三切换电流阈值时，控制励磁电感在变换器的一个工作周期的电流峰值为第三电流峰值，以使变换器处于HBURST模式。控制器还在输出电流小于或者等于第三切换电流阈值时，控制励磁电感在一个工作周期的电流峰值为第四电流峰值，并在经过一个工作周期内的电流峰值为第三电流峰值的第一工作周期次数后，控制励磁电感在一个工作周期的电流峰值为第五电流峰值，以使变换器处于LBURST模式。其中，第四电流峰值小于或者等于第三电流峰值且大于第五电流峰值。可以理解的，在变换器处于HBURST模式后，本实施方式对极轻载情况下变换器的工作模式进行了优化，使变换器处于LBURST模式，以使输出能量得到进一步减少，从而不仅可降低能源损耗和开关管损耗以提高变换器的效率，而且可以降低极轻载情况下变换器的输出电压纹波。
结合第一方面第一种可能的实施方式或者第二种可能的实施方式，在第七种可能的实施方式中，控制器在输出电流小于或者等于第一切换电流阈值时，控制主开关管和辅开关管在变换器的一个工作周期(即高频间歇周期)的导通次数均为第三导通次数，以使变换器处于HBURST模式。控制器还在主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数后，若变换器的工作频率(即高频间歇周期的频率)位于预设频率范围内，则控制主开关管和辅开关管在一个工作周期的导通次数均为第四导通次数，并在经过一个工作周期内的导通次数为第四导通次数的第一工作周期次数后，控制主开关管和辅开关管在一个工作周期的导通次数均为第五导通次数，其中，第四导通次数小于或者等于第三导通次数且大于第五导通次数。若变换器的工作频率位于预设频率范围外，则控制主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数。可以理解的，在变换器处于HBURST模式后，本实施方式对高频间歇周期的频率处于人耳听觉范围内时变换器的工作模式进行了优化，使变换器处于LBURST模式，从而可降低能源损耗和开关管损耗，进而可提高变换器的效率。此外，在高频间歇周期的频率处于人耳听觉范围内时，变换器处于LBURST模式，可有效降低变换器的开关噪声。
结合第一方面第一种可能的实施方式或者第二种可能的实施方式，在第八种可能的实施方式中，变压器包括励磁电感。控制器在输出电流小于或者等于第一切换电流阈值时，控制励磁电感在变换器的一个工作周期的电流峰值为第三电流峰值，以使变换器处于HBURST模式。控制器还在励磁电感在一个工作周期的电流峰值为第三电流峰值后，若变换器的工作频率位于预设频率范围内，则控制励磁电感在一个工作周期的电流峰值为第四电流峰值，并在经过一个工作周期内的电流峰值为第四电流峰值的第一工作周期次数后，控制励磁电感在一个工作周期的电流峰值为第五电流峰值，其中，第四电流峰值大于第五电流峰值且小于或者等于第三电流峰值。若变换器的工作频率位于预设频率范围外，则控制励磁电感在一个工作周期的电流峰值为第三电流峰值。可以理解的，在变换器处于HBURST模式后，本实施方式对高频间歇周期的频率处于人耳听觉范围内时变换器的工作模式进行了优化，使变换器处于LBURST模式，从而可降低能源损耗和开关管损耗，进而可提高变换器的效率。此外，在高频间歇周期的频率处于人耳听觉范围内时，变换器处于LBURST模式，可有效降低变换器的开关噪声。
结合第一方面第一种可能的实施方式至第一方面第八种可能的实施方式中的任一种，在第九种可能的实施方式中，控制器在输出电流大于第一切换电流阈值时，在输出电流分别为第一输出电流和第二输出电流时，控制变换器的开关频率分别为第一开关频率和第 二开关频率，其中，第一输出电流大于第二输出电流时，第一开关频率小于第二开关频率。
结合第一方面第一种可能的实施方式至第一方面第九种可能的实施方式中的任一种，在第十种可能的实施方式中，第一工作模式包括连续谐振电流反激模式(continuous resonance mode，CRM)，第二工作模式包括间歇发波模式。控制器在输出电流大于第一切换电流阈值时，控制变换器工作在CRM；或者，在输出电流小于或者等于第一切换电流阈值时，控制变换器工作在间歇发波模式。
结合第一方面，在第十一种可能的实施方式中，模式切换参数为变换器处于第二工作模式下的第一工作参数。控制器还获得变换器的开关频率；在开关频率达到频率阈值时，根据输出电压得到变换器处于第二工作模式下的第一工作参数；基于第一工作参数控制变换器从第一工作模式切换至第二工作模式，其中，第一工作参数包括主开关管和辅开关管在变换器的一个工作周期的导通次数，或者励磁电感在一个工作周期的电流峰值。可以理解的，由于变换器的开关频率和开关损耗常与输出电压强相关，本申请提供的变换器可以根据不同输出电压调整自身从第一工作模式切换至第二工作模式下的工作参数，以减小变换器的开关频率和开关损耗，因此可优化变换器在全范围输出电压下的效率。
结合第一方面第十一种可能的实施方式，在第十二种可能的实施方式中，控制器在开关频率达到频率阈值时，从多个电压区间中得到输出电压所在的第一电压区间；从多个电压区间对应的多个工作参数中得到第一电压区间对应的第一工作参数，其中，多个电压区间与多个工作参数一一对应。
结合第一方面第十二种可能的实施方式，在第十三种可能的实施方式中，多个电压区间还包括第二电压区间，在第二电压区间中的任意值均小于第一电压区间中的任意值时，第二电压区间对应的第二工作参数小于第一工作参数。示例性的，第一电压区间和第二电压区间分别为高压区间和中压区间。由于本申请在输出电压位于中压区间时变换器的HBURST模式进入点(即第二工作参数)，相较于输出电压位于高压区间时变换器的HBURST模式进入点(即第一工作参数)均有降低，因此，相较于针对不同输出电压均采用相同的HBURST模式进入点而言，本申请在输出电压位于中压区间时的HBURST模式进入点更小，可降低每次高频间歇周期传输的能量，从而降低原副边绕组损耗和开关管导通损耗，进而提高变换器处于HBURST模式下的效率。
结合第一方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十四种可能的实施方式中，第一工作参数包括导通次数，导通次数为第一导通次数。控制器控制主开关管和辅开关管在一个工作周期的导通次数为第一导通次数，以使变换器切换至HBURST模式。并在主开关管和辅开关管在一个工作周期的导通次数为第一导通次数后，若变换器的输出电流小于或者等于第二切换电流阈值，则控制主开关管和辅开关管在一个工作周期的导通次数均为第二导通次数，其中，第二导通次数小于第一导通次数；若变换器的输出电流大于第二切换电流阈值且小于或者等于第一切换电流阈值，则控制主开关管和辅开关管在一个工作周期的导通次数均为第一导通次数。可以理解的，在变换器切换至HBURST模式后，变换器可以基于负载的变化调整开关管在一个高频间歇周期内的导通次数，保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器的效率。此外，由于在负载逐渐变轻的过程中，开关管在一个高频间歇周期内的导通次数也逐渐减小，因此，还可降低轻载情况下变换器的输出电压纹波，适用性强。
结合第一方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十五种可能的实施方式中，第一切换参数包括电流峰值，电流峰值为第一电流峰值。控制 器控制励磁电感在一个工作周期的电流峰值为第一电流峰值，以使变换器切换至HBURST模式。并在励磁电感在一个工作周期的电流峰值为第一电流峰值后，若变换器的输出电流小于或者等于第二切换电流阈值，则控制励磁电感在一个工作周期的电流峰值为第二电流峰值，其中，第二电流峰值小于第一电流峰值；若变换器的输出电流大于第二切换电流阈值且小于或者等于第一切换电流阈值，则控制励磁电感在一个工作周期的电流峰值为第一电流峰值。可以理解的，在变换器切换至HBURST模式后，变换器可以基于负载的变化调整励磁电感在一个高频间歇周期内的电流峰值,保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器的效率。此外，由于在负载逐渐变轻的过程中，励磁电感在一个高频间歇周期内的电流峰值也逐渐减小，因此，还可降低轻载情况下变换器的输出电压纹波，适用性强。
结合第一方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十六种可能的实施方式中，第一切换参数包括导通次数，导通次数为第三导通次数。控制器控制主开关管和辅开关管在一个工作周期的导通次数为第三导通次数，以使变换器切换至HBURST模式。并在主开关管和辅开关管在一个工作周期的导通次数为第三导通次数后，若变换器的输出电流小于或者等于第三切换电流阈值，则控制主开关管和辅开关管在一个工作周期的导通次数为第四导通次数，并在经过一个工作周期内的导通次数为第四导通次数的第一工作周期次数后，控制主开关管和辅开关管在一个工作周期的导通次数均为第五导通次数，以使变换器切换至LBURST模式，其中，第四导通次数小于或者等于第三导通次数且大于第五导通次数；若变换器的输出电流大于第三切换电流阈值且小于或者等于第一切换电流阈值，则控制主开关管和辅开关管在一个工作周期的导通次数为第三导通次数。可以理解的，在变换器切换至HBURST模式后，相比基于负载调整开关管在一个高频间歇周期的导通次数以使变换器始终处于HBURST模式的实施方式而言，本实施方式中对极轻载(即输出电流小于或者等于第三切换电流阈值)情况下变换器的工作模式进行了进一步优化，使变换器处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器的效率。此外，由于极轻载情况下，变换器处于LBURST模式，使得输出能量得到进一步减少，因此，本实施方式还可进一步降低极轻载情况下变换器的输出电压纹波，适用性更强。
结合第一方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十七种可能的实施方式中，第一切换参数包括电流峰值，电流峰值为第三电流峰值。控制器控制励磁电感在一个工作周期的电流峰值为第三电流峰值，以使变换器切换至HBURST模式。并在励磁电感在一个工作周期的电流峰值为第三电流峰后，若变换器的输出电流小于或者等于第三切换电流阈值，则控制励磁电感在一个工作周期的电流峰值为第四电流峰值；并在经过第一工作周期内的电流峰值为第四电流峰值的第一工作周期次数后，控制励磁电感在一个工作周期的电流峰值为第五电流峰值，以使变换器切换至LBURST模式，其中，第四电流峰值小于或者等于第三电流峰值且大于第五电流峰值；若变换器的输出电流大于第三切换电流阈值且小于或者等于第一切换电流阈值，则控制励磁电感在一个工作周期的电流峰值为第三电流峰值。可以理解的，在变换器切换至HBURST模式后，相比基于负载调整励磁电感在一个高频间歇周期内的电流峰值以使变换器始终处于HBURST模式的实施方式而言，本实施方式中对极轻载情况下变换器的工作模式进行了进一步优化，使变换器处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器的效率。再者，由于极轻载情况下，变换器处于LBURST模式，使得输出能量得到进一步减少， 因此，本实施例还可进一步降低极轻载情况下变换器的输出电压纹波，适用性更强。
结合第一方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十八种可能的实施方式中，第一切换参数包括导通次数，导通次数为第三导通次数。控制器控制主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数，以使变换器切换至HBURST模式。并在主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数后，若变换器的工作频率位于预设频率范围内，则控制主开关管和辅开关管在一个工作周期的导通次数均为第四导通次数；并在经过一个工作周期内的导通次数为第四导通次数的第一工作周期次数后，控制主开关管和辅开关管在一个工作周期的导通次数均为第五导通次数，以使变换器切换至LBURST模式，其中，第四导通次数小于或者等于第一导通次数且大于第五导通次数；若变换器的工作频率位于预设频率范围外，则控制主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数。可以理解的，在变换器切换至HBURST模式后，相比基于负载调整开关管在一个高频间歇周期的导通次数以使变换器始终处于HBURST模式的实施方式而言，本实施方式中对高频间歇周期的频率处于人耳听觉范围内时变换器的工作模式进行了进一步优化，使变换器处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器的效率。再者，在高频间歇周期的频率处于人耳听觉范围内时，变换器处于LBURST模式，可有效降低变换器的开关噪声。
结合第一方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十九种可能的实施方式中，第一切换参数包括电流峰值，电流峰值为第三电流峰值。控制器控制励磁电感在一个工作周期的电流峰值为第三电流峰值，以使变换器切换至HBURST模式。并在励磁电感在一个工作周期的电流峰值为第三电流峰值后，若变换器的工作频率位于预设频率范围内，则控制励磁电感在一个工作周期的电流峰值为第四电流峰值，并在经过一个工作周期内的电流峰值为第四电流峰值的第一工作周期次数后，控制励磁电感在一个工作周期的电流峰值为第五电流峰值，以使变换器切换至LBURST模式，其中，第四电流峰值大于第五电流峰值且小于或者等于第一电流峰值；若变换器的工作频率位于预设频率范围外，则控制励磁电感在一个工作周期的电流峰值为第三电流峰值。可以理解的，在变换器切换至HBURST模式后，相比基于负载调整励磁电感在一个高频间歇周期内的电流峰值以使变换器始终处于HBURST模式的实施方式而言，本实施方式中对高频间歇周期的频率处于人耳听觉范围内时变换器的工作模式进行了进一步优化，使变换器处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器的效率。此外，在高频间歇周期的频率处于人耳听觉范围内时，变换器处于LBURST模式，可有效降低变换器的开关噪声。
结合第一方面第十一种可能的实施方式至第十九种可能的实施方式中的任一种，在第二十种可能的实施方式中，第一工作模式包括CRM，第二工作模式包括间歇发波模式。
结合第一方面第三种可能的实施方式、第五种可能的实施方式、第七种可能的实施方式、第十四种可能的实施方式、第十六种可能的实施方式或者第十八种可能的实施方式，在第二十一种可能的实施方式中，工作周期由主开关管和辅开关管在一个工作周期的导通次数确定。
结合第一方面第四种可能的实施方式、第六种可能的实施方式、第八种可能的实施方式、第十五种可能的实施方式、第十七种可能的实施方式或者第十九种可能的实施方式，在第二十二种可能的实施方式中，工作周期由励磁电感在一个工作周期的电流峰值确定。
结合第一方面至第一方面第二十二种可能的实施方式中的任一种，在第二十三种可能的实施方式中，变压器包括原边绕组、副边绕组、励磁电感、谐振电感和谐振电容，变压器的输入端包括第一输入端和第二输入端，变压器的输出端包括第一输出端和第二输出端。其中，原边绕组与励磁电感并联；谐振电感的一端连接至变压器的第一输入端，谐振电感的另一端连接变换器的输入端或者原边绕组的同名端，原边绕组的异名端通过谐振电容连接变压器的第二输入端，副边绕组的异名端和同名端分别连接变压器的第一输出端和第二输出端。
结合第一方面第二十三种可能的实施方式，在第二十四种可能的实施方式中，变换器还包括电压采样电路，电压采样电路并联至谐振电容的两端，用于采集谐振电容的电压。控制器获得谐振电容的电压，并基于副边绕组与原边绕组的匝数比和谐振电容的电压，得到变换器的输出电压。可以理解的，变换器可以通过电压采样电路采集到的谐振电容的电压得到变换器的输出电压，输出电压获取方式简单，便于控制。
结合第一方面第二十三种可能的实施方式，在第二十五种可能的实施方式中，变压器还包括辅助绕组，变换器还包括电压采样电路，电压采样电路并联至辅助绕组的两端，用于采集辅助绕组的电压。控制器获得辅助绕组的电压，并基于副边绕组与辅助绕组的匝数比和辅助绕组的电压，得到变换器的输出电压。可以理解的，变换器还可以通过电压采样电路采集到的辅助绕组的电压得到变换器的输出电压，输出电压获取方式多样，灵活性高。
第二方面，本申请提供了一种变换器的控制方法，该变换器包括主开关管、辅开关管、变压器和控制器。其中，主开关管和辅开关管串联在变换器的输入端和参考地之间，变压器的输入端分别连接至辅开关管的两端，变压器的输出端连接变换器的输出端。该方法包括：变换器获得自身的输出电压，并基于变换器的输出电压得到模式切换参数；根据模式切换参数控制变换器在第一工作模式与第二工作模式之间切换，其中，第一工作模式下变换器的开关频率的大小与变换器的输出电流的大小负相关，第二工作模式下在变换器的一个工作周期内变换器的开关频率不变。
结合第二方面，在第一种可能的实施方式中，模式切换参数为第一切换电流阈值。变换器比较自身的输出电流与第一切换电流阈值的大小，并根据比较结果控制变换器在第一工作模式与第二工作模式之间切换。
结合第二方面第一种可能的实施方式，在第二种可能的实施方式中，变换器基于输出电压，从多个电压区间中得到输出电压所在的第一电压区间，并从电压区间对应的多个切换电流阈值中得到第一电压区间对应的第一切换电流阈值，其中，多个电压区间与多个切换电流阈值一一对应。
结合第二方面第一种可能的实施方式或者第二种可能的实施方式，在第三种可能的实施方式中，变换器在输出电流小于或者等于第一切换电流阈值且大于第二切换电流阈值时，控制主开关管和辅开关管在变换器的一个工作周期的导通次数均为第一导通次数，以使变换器处于第二工作状态。并在输出电流小于或者等于第二切换电流阈值时，控制主开关管和辅开关管在一个工作周期的导通次数均为第二导通次数，其中，第二导通次数小于第一导通次数。
结合第二方面第一种可能的实施方式或者第二种可能的实施方式，在第四种可能的实施方式中，变压器包括励磁电感。变换器在输出电流小于或者等于第一切换电流阈值且大于第二切换电流阈值时，控制励磁电感在变换器的一个工作周期的电流峰值为第一电流峰值，以使变换器处于第二工作模式。并在输出电流小于或者等于第二切换电流阈值时，控制励磁电感在一个工作周期的电流峰值为第二电流峰值，其中，第二电流峰值小于第一电流峰值。
结合第二方面第一种可能的实施方式或者第二种可能的实施方式，在第五种可能的实施方式中，变换器在输出电流小于或者等于第一切换电流阈值且大于第三切换电流阈值时，控制主开关管和辅开关管在变换器的一个工作周期的导通次数均为第三导通次数，以使变换器处于第二工作模式。并在输出电流小于或者等于第三切换电流阈值时，控制主开关管和辅开关管在一个工作周期的导通次数均为第四导通次数，并在经过一个工作周期内的导通次数为第三导通次数的第一工作周期次数后，控制主开关管和辅开关管在一个工作周期的导通次数均为第五导通次数，以使变换器处于LBURST模式，其中，第四导通次数小于或者等于第三导通次数且大于第五导通次数。
结合第二方面第一种可能的实施方式或者第二种可能的实施方式，在第六种可能的实施方式中，变压器包括励磁电感。变换器在输出电流小于或者等于第一切换电流阈值且大于第三切换电流阈值时，控制励磁电感在变换器的一个工作周期的电流峰值为第三电流峰值。并在输出电流小于或者等于第三切换电流阈值时，控制励磁电感在一个工作周期的电流峰值为第四电流峰值，并在经过一个工作周期内的电流峰值为第三电流峰值的第一工作周期次数后，控制励磁电感在一个工作周期的电流峰值为第五电流峰值，其中，第四电流峰值小于或者等于第三电流峰值且大于第五电流峰值。
结合第二方面第一种可能的实施方式或者第二种可能的实施方式，在第七种可能的实施方式中，变换器在输出电流小于或者等于第一切换电流阈值时，控制主开关管和辅开关管在变换器的一个工作周期的导通次数均为第三导通次数。并在主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数后，若变换器的工作频率位于预设频率范围内，则控制主开关管和辅开关管在一个工作周期的导通次数均为第四导通次数，并在经过一个工作周期内的导通次数为第四导通次数的第一工作周期次数后，控制主开关管和辅开关管在一个工作周期的导通次数均为第五导通次数，其中，第四导通次数小于或者等于第三导通次数且大于第五导通次数。若变换器的工作频率位于预设频率范围外，则控制主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数。
结合第二方面第一种可能的实施方式或者第二种可能的实施方式，在第八种可能的实施方式中，变压器包括励磁电感。变换器在输出电流小于或者等于第一切换电流阈值时，控制励磁电感在变换器的一个工作周期的电流峰值为第三电流峰值。并在励磁电感在一个工作周期的电流峰值为第三电流峰值后，若变换器的工作频率位于预设频率范围内，则控制励磁电感在一个工作周期的电流峰值为第四电流峰值，并在经过一个工作周期内的电流峰值为第四电流峰值的第一工作周期次数后，控制励磁电感在一个工作周期的电流峰值为第五电流峰值，其中，第四电流峰值大于第五电流峰值且小于或者等于第三电流峰值。若变换器的工作频率位于预设频率范围外，则控制励磁电感在一个工作周期的电流峰值为第三电流峰值。
结合第二方面第一种可能的实施方式至第二方面第八种可能的实施方式中的任一种，在第九种可能的实施方式中，变换器在输出电流大于第一切换电流阈值时，在输出电流分别为第一输出电流和第二输出电流时，控制变换器的开关频率分别为第一开关频率和第二开关频率，其中，第一输出电流大于第二输出电流时，第一开关频率小于第二开关频率。
结合第二方面第一种可能的实施方式至第二方面第九种可能的实施方式中的任一种，在第十种可能的实施方式中，第一工作模式包括CRM，第二工作模式包括间歇发波模式。变换器在输出电流大于第一切换电流阈值时，控制变换器工作在CRM；或者，在输出电流小于或者等于第一切换电流阈值时，控制变换器工作在间歇发波模式。
结合第二方面，在第十一种可能的实施方式中，模式切换参数为变换器处于第二工作模式下的第一工作参数。变换器还获得变换器的开关频率；在开关频率达到频率阈值时，根据输出电压得到变换器处于第二工作模式下的第一工作参数；基于第一工作参数控制变换器从第一工作模式切换至第二工作模式，其中，第一工作参数包括主开关管和辅开关管在变换器的一个工作周期的导通次数，或者励磁电感在一个工作周期的电流峰值。
结合第二方面第十一种可能的实施方式，在第十二种可能的实施方式中，变换器在开关频率达到频率阈值时，从多个电压区间中得到输出电压所在的第一电压区间；从多个电压区间对应的多个工作参数中得到第一电压区间对应的第一工作参数，其中，多个电压区间与多个工作参数一一对应。
结合第二方面第十二种可能的实施方式，在第十三种可能的实施方式中，多个电压区间还包括第二电压区间，在第二电压区间中的任意值均小于第一电压区间中的任意值时，第二电压区间对应的第二工作参数小于第一工作参数。
结合第二方面第十一种可能的实施方式至第二方面第十三种可能的实施方式中的任一种，在第十四种可能的实施方式中，第一工作参数包括导通次数，导通次数为第一导通次数。变换器控制主开关管和辅开关管在一个工作周期的导通次数为第一导通次数。并在主开关管和辅开关管在一个工作周期的导通次数为第一导通次数后，若变换器的输出电流小于或者等于第二切换电流阈值，则控制主开关管和辅开关管在一个工作周期的导通次数均为第二导通次数，其中，第二导通次数小于第一导通次数；若变换器的输出电流大于第二切换电流阈值且小于或者等于第一切换电流阈值，则控制主开关管和辅开关管在一个工作周期的导通次数均为第一导通次数。
结合第二方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十五种可能的实施方式中，第一切换参数包括电流峰值，电流峰值为第一电流峰值。变换器控制励磁电感在一个工作周期的电流峰值为第一电流峰值。并在励磁电感在一个工作周期的电流峰值为第一电流峰值后，若变换器的输出电流小于或者等于第二切换电流阈值，则控制励磁电感在一个工作周期的电流峰值为第二电流峰值，其中，第二电流峰值小于第一电流峰值；若变换器的输出电流大于第二切换电流阈值且小于或者等于第一切换电流阈值，则控制励磁电感在一个工作周期的电流峰值为第一电流峰值。
结合第二方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十六种可能的实施方式中，第一切换参数包括导通次数，导通次数为第三导通次数。变换器控制主开关管和辅开关管在一个工作周期的导通次数为第三导通次数。并在主开关管和辅开关管在一个工作周期的导通次数为第三导通次数后，若变换器的输出电流小于或者等于第三切换电流阈值，则控制主开关管和辅开关管在一个工作周期的导通次数为第四导通次数；并在经过一个工作周期内的导通次数为第四导通次数的第一工作周期次数后，控制主开关管和辅开关管在一个工作周期的导通次数均为第五导通次数，其中，第四导通次数小于或者等于第三导通次数且大于第五导通次数；若变换器的输出电流大于第三切换电流阈值且小于或者等于第一切换电流阈值，则控制主开关管和辅开关管在一个工作周期的导通次数为第三导通次数。
结合第二方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十七种可能的实施方式中，第一切换参数包括电流峰值，电流峰值为第三电流峰值。变换器控制励磁电感在一个工作周期的电流峰值为第三电流峰值。并在励磁电感在一个工作周期的电流峰值为第三电流峰后，若变换器的输出电流小于或者等于第三切换电流阈值，则控制 励磁电感在一个工作周期的电流峰值为第四电流峰值；并在经过第一工作周期内的电流峰值为第四电流峰值的第一工作周期次数后，控制励磁电感在一个工作周期的电流峰值为第五电流峰值，其中，第四电流峰值小于或者等于第三电流峰值且大于第五电流峰值；若变换器的输出电流大于第三切换电流阈值且小于或者等于第一切换电流阈值，则控制励磁电感在一个工作周期的电流峰值为第三电流峰值。
结合第二方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十八种可能的实施方式中，第一切换参数包括导通次数，导通次数为第三导通次数。变换器控制主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数。并在主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数后，若变换器的工作频率位于预设频率范围内，则控制主开关管和辅开关管在一个工作周期的导通次数均为第四导通次数；并在经过一个工作周期内的导通次数为第四导通次数的第一工作周期次数后，控制主开关管和辅开关管在一个工作周期的导通次数均为第五导通次数，其中，第四导通次数小于或者等于第一导通次数且大于第五导通次数；若变换器的工作频率位于预设频率范围外，则控制主开关管和辅开关管在一个工作周期的导通次数均为第三导通次数。
结合第二方面第十一种可能的实施方式至第十三种可能的实施方式中的任一种，在第十九种可能的实施方式中，第一切换参数包括电流峰值，电流峰值为第三电流峰值。变换器控制励磁电感在一个工作周期的电流峰值为第三电流峰值。并在励磁电感在一个工作周期的电流峰值为第三电流峰值后，若变换器的工作频率位于预设频率范围内，则控制励磁电感在一个工作周期的电流峰值为第四电流峰值；并在经过一个工作周期内的电流峰值为第四电流峰值的第一工作周期次数后，控制励磁电感在一个工作周期的电流峰值为第五电流峰值，其中，第四电流峰值大于第五电流峰值且小于或者等于第一电流峰值；若变换器的工作频率位于预设频率范围外，则控制励磁电感在一个工作周期的电流峰值为第三电流峰值。
结合第二方面第十一种可能的实施方式至第十九种可能的实施方式中的任一种，在第二十种可能的实施方式中，第一工作模式包括CRM，第二工作模式包括间歇发波模式。
结合第二方面第三种可能的实施方式、第五种可能的实施方式、第七种可能的实施方式、第十四种可能的实施方式、第十六种可能的实施方式或者第十八种可能的实施方式，在第二十一种可能的实施方式中，工作周期由主开关管和辅开关管在一个工作周期的导通次数确定。
结合第二方面第四种可能的实施方式、第六种可能的实施方式、第八种可能的实施方式、第十五种可能的实施方式、第十七种可能的实施方式或者第十九种可能的实施方式，在第二十二种可能的实施方式中，工作周期由励磁电感在一个工作周期的电流峰值确定。
结合第二方面至第二方面第二十二种可能的实施方式中的任一种，在第二十三种可能的实施方式中，变压器包括原边绕组、副边绕组、励磁电感、谐振电感和谐振电容，变压器的输入端包括第一输入端和第二输入端，变压器的输出端包括第一输出端和第二输出端。其中，原边绕组与励磁电感并联；谐振电感的一端连接至变压器的第一输入端，谐振电感的另一端连接变换器的输入端或者原边绕组的同名端，原边绕组的异名端通过谐振电容连接变压器的第二输入端，副边绕组的异名端和同名端分别连接变压器的第一输出端和第二输出端。
结合第二方面第二十三种可能的实施方式，在第二十四种可能的实施方式中，变换器还包括电压采样电路，电压采样电路并联至谐振电容的两端，用于采集谐振电容的电压。控制器获得谐振电容的电压，并基于副边绕组与原边绕组的匝数比和谐振电容的电压，得到 变换器的输出电压。
结合第二方面第二十三种可能的实施方式，在第二十五种可能的实施方式中，变压器还包括辅助绕组，变换器还包括电压采样电路，电压采样电路并联至辅助绕组的两端，用于采集辅助绕组的电压。控制器获得辅助绕组的电压，并基于副边绕组与辅助绕组的匝数比和辅助绕组的电压，得到变换器的输出电压。
第三方面，本申请提供了一种终端设备，该终端设备包括电池和第一方面至第一方面任一种可能的实施方式所提供的变换器，其中，变换器用于向电池充电。
应理解的是，本申请上述多个方面的实现和有益效果可互相参考。
附图说明
图1是本申请提供的变换器的应用场景示意图；
图2a是本申请提供的变换器的一结构示意图；
图2b是本申请提供的变换器的另一结构示意图；
图3a是本申请提供的变换器的另一结构示意图；
图3b是本申请提供的变换器的另一结构示意图；
图4是本申请提供的三个电压区间的示意图；
图5是本申请提供的变换器的模式切换示意图；
图6是本申请提供的变换器处于高频间歇发波模式下的控制时序图；
图7是本申请提供的变换器处于低频间歇发波模式下的控制时序图；
图8a是本申请提供的变换器的另一结构示意图；
图8b是本申请提供的变换器的另一结构示意图；
图9是本申请提供的不同输出电压下变换器的效率示意图；
图10是本申请提供的变换器的控制方法的一流程示意图；
图11是本申请提供的终端设备的一结构示意图。
具体实施方式
本申请提供的变换器可适用于可应用于电子设备领域、工业领域(如激光器的电源适配器)、航天领域(如航天电源)以及其它领域。具体来讲，本申请提供的变换器可适用于电子设备(如智能手机、平板电脑、笔记本电脑、台式计算机、智能音箱、智能手表以及可穿戴设备等)的电源适配器、工业电源、航天电源等，以将直流电直流变换成电子设备、工业设备、航天设备等适用的电压和电流，本申请提供的变换器适用于电子设备供电场景、电动汽车应用场景或者其他应用场景。下面以电子设备供电场景为例进行说明。
参见图1，图1是本申请提供的变换器的应用场景示意图。如图1所示，在电子设备供电场景下，本申请提供的变换器可以为图1所示的电源适配器。该电源适配器的输入端通过交流AC/直流DC变换器连接电网，输出端连接电子设备。在需要对电子设备进行供电时，AC/DC变换器先将电网提供的交流电压(如220V)整流变换为第一直流电压并输出至电源适配器的输入端。电源适配器将输入端的第一直流电压进行直流变换得到第二直流电压，并向电子设备输出第二直流电压，从而实现对电子设备的供电。与此同时，电源适配器在向电子设备供电的过程中，电源适配器获取自身的当前输出电压，并基于该当前输出电压得到模式切换参数。电源适配器根据模式切换参数控制变换器在第一工 作模式与第二工作模式之间切换，其中，第一工作模式下变换器的开关频率的大小与变换器的输出电流的大小负相关，第二工作模式下在变换器的一个工作周期内变换器的开关频率不变。示例性的，第一工作模式为CRM，第二工作模式为间歇发波模式。
由于电源适配器的开关损耗常与输出电压强相关，本申请提供的电源适配器可以根据不同输出电压调整自身在不同工作模式之间切换的模式切换参数，也即电源适配器根据不同输出电压调整自身的工作模式，或者电源适配器调整自身从第一工作模式切换至第二工作模式下的工作参数，以减小开关损耗，因此可优化电源适配器在全范围输出电压下的效率。上述只是对本申请提供的变换器的应用场景进行示例，而非穷举，本申请不对应用场景进行限制。
下面结合图2a至图9对本申请提供的变换器的工作原理进行示例说明。
参见图2a，图2a是本申请提供的变换器的一结构示意图。如图2a所示，变换器1包括主开关管S1、辅开关管S2、变压器11和控制器12。其中，主开关管S1的一端连接变换器1的输入端in1，主开关管S1的另一端通过辅开关管S2连接参考地。变压器的输入端in21和in22分别连接至辅开关管S2的两端，变压器的输出端out2连接变换器1的输出端out1。变换器1的输入端in1连接交流电源，输出端out1连接直流负载。示例性的，本申请提供的变换器1可以为AHB变换器。
可选的，主开关管S1与辅开关管S2之间的位置还可以调换，具体请参见图2b。如图2b所示，辅开关管S2的一端连接变换器1的输入端in1，辅开关管S2的另一端通过主开关管S1连接参考地。
在一可选实施方式中，在变换器1开始工作后，控制器12获取变换器1的当前输出电压，并基于当前输出电压获得模式切换参数。控制器12根据模式切换参数控制变换器1在第一工作模式与第二工作模式之间切换，其中，第一工作模式下变换器1的开关频率的大小与变换器1的输出电流的大小负相关，第二工作模式下在变换器1的一个工作周期内变换器1的开关频率不变。示例性的，第一工作模式为CRM，第二工作模式为间歇发波模式。
在本申请实施例中，由于变换器1的开关损耗常与输出电压强相关，本申请提供的变换器1可以根据不同输出电压调整自身在不同工作模式之间切换的模式切换参数，也即变换器1根据不同输出电压调整自身的工作模式，或者变换器1调整自身从第一工作模式切换至第二工作模式下的工作参数，以减小开关损耗，因此可优化变换器1在全范围输出电压下的效率。
再参见图2a，在一可选实施方式中，在变换器1开始工作后，控制器12获取变换器1的当前输出电压，并基于当前输出电压获得第一切换电流阈值。控制器12获取变换器1的当前输出电流，并比较当前输出电流与第一切换电流阈值之间的大小，从而根据比较结果控制变换器1在第一工作模式与第二工作模式之间切换。可以理解的，由于变换器1的开关损耗常与输出电压强相关，本申请提供的变换器1可以根据不同输出电压调整自身在不同工作模式(即第一工作模式与第二工作模式)之间切换的模式切换点(即切换电流阈值)，也即变换器1根据不同输出电压调整自身的工作模式以减小开关损耗，因此可优化变换器1在全范围输出电压下的效率。
在另一可选实施方式中，变压器11包括励磁电感。在变换器1开始工作后，控制器12获取变换器1的当前开关频率和当前输出电压，并在当前开关频率达到频率阈值的情况下，根据当前输出电压得到变换器1处于第二工作模式下的第一工作参数，从而基于 第一工作参数控制变换器1从第一工作模式切换至第二工作模式。其中，第一工作参数包括主开关管S1和辅开关管S2在变换器1的一个工作周期内的第一导通次数，或者励磁电感在变换器1的一个工作周期内的电流峰值。可以理解的，由于变换器1的开关频率和开关损耗常与输出电压强相关，本申请提供的变换器1可以根据不同输出电压调整自身从第一工作模式切换至第二工作模式下的工作参数(即开关管的导通次数或者励磁电感的电流峰值)，以减小变换器1的开关频率和开关损耗，因此可优化变换器1在全范围输出电压下的效率。
在本申请实施例中，变换器1可基于当前输出电压调整模式切换点的方式，或者基于当前输出电压调整变换器1从第一工作模式切换至第二工作模式下的工作参数的方式，减小变换器1的开关损耗，从而优化变换器1在全范围输出电压下的效率。
参见图3a，图3a是本申请提供的变换器的另一结构示意图。如图3a所示，变换器1包括主开关管S1、辅开关管S2、变压器11、控制器12和电压采样电路13。可选的，变换器1还包括输入电容C in、输出电容C o、整流二极管D1、输入电压采样模块14和隔离副边电压采样模块15。
这里，主开关管S1和辅开关管S2可以是采用硅半导体材料(silicon，Si)或者第三代宽禁带半导体材料的碳化硅(silicon carbide，SiC)或者氮化镓(gallium nitride，GaN)等材料制成的场效应晶体管(field-effect transistor，FET)。本实施例以金属氧化物半导体场效应晶体管(Metal Oxide Semiconductor Field Effect Transistor，MOSFET)为例对主开关管S1和辅开关管S2进行介绍。
变换器1的输入端in1与参考地之间设置有输入电容C in。输入电压采样模块14设置有一个输入端和一个输出端，输入电压采样模块14的输入端连接输入电容C in的正极，输出端连接控制器12，用于采集变换器1的输入电压，并将输入电压输出给控制器12，以进行输入电压保护、PWM伏秒平衡控制。
主开关管S1的漏极连接变换器1的输入端in1，主开关管S1的源极连接辅开关管S2的漏极，辅开关管S2的源极连接参考地。主开关管S1的栅极和辅开关管S2的栅极连接控制器12。
变压器11(即反激变压器)包括原边绕组N P、副边绕组N S、铁芯T 1、励磁电感L m、谐振电感L r(包括变压器11的漏感和外加的电感，也可以全部集成在变压器11里面)和谐振电容C r，变压器11的输入端in2包括第一输入端in21和第二输入端in22，变压器的输出端out2包括第一输出端out21和第二输出端out22。其中，谐振电感L r的一端通过变压器11的第一输入端in21连接辅开关管S2的漏极，谐振电感L r的另一端连接原边绕组N P的同名端，原边绕组N P的异名端连接谐振电容C r的一端，谐振电容C r的另一端通过变压器11的第二输入端in22连接辅开关管S2的源极，励磁电感L m与原边绕组N P并联。副边绕组N S的异名端和同名端分别连接变压器11的第一输出端out21和第二输出端out22。原边绕组N P和副边绕组N S均耦合至铁芯T 1上。可选的，谐振电感L r还可以连接至变换器1的输入端in1和变压器11的第一输入端in21之间。可选的，变压器11的两个输入端in21和in22还可分别连接至主开关管S1的两端。
变换器1的输出端out1包括第一输出端out11和第二输出端out12。变压器11的第一输出端out21通过整流二极管D1连接变换器1的第一输出端out11，变压器11的第二输出端out22连接变换器1的第二输出端out12和参考地。变压器11的第一输出端out21和第二输出端out22之间还设置有输出电容C o。
电压采样电路13包括采样电阻R 1和R 2，其中，采样电阻R 2的一端连接谐振电容C r的一端，采样电阻R 2的另一端通过采样电阻R 1连接谐振电容C r的另一端，采样电阻R 1和R 2之间的连接点连接控制器12。电压采样电路13用于采集谐振电容C r的电压，并将谐振电容C r的电压输出给控制器12。
隔离副边电压采样模块15为负载采样模块，隔离副边电压采样模块15设有一个输入端和一个输出端，该输入端连接输出电容C o的正极，输出端连接控制器12。隔离副边电压采样模块15包括光敏三极管Q1、发光二极管D2和击穿二极管D3，其中，光敏三极管Q1和发光二极管D2构成光耦，该光耦通过发光二极管D2将变换器1的输出电压转换为光信号，进而光敏三极管Q1将接收到的光信号转换为电流信号。隔离副边电压采样模块15用于采集输出电压隔离反馈信号，并将输出电压隔离反馈信号输出给控制器12。该输出电压隔离反馈信号用于控制变换器1的输出电压稳定，同时也用于反映负载信息，以用于后续模式切换。
在一可选实施方式中，在变换器1工作后，控制器12获取变换器1的当前输出电压，并基于当前输出电压获得第一切换电流阈值。控制器12获取变换器1的当前输出电流，并比较当前输出电流与第一切换电流阈值之间的大小，从而根据比较结果控制变换器1在第一工作模式与第二工作模式之间切换。
具体的，控制器12可以为图3b所示的控制器12。如图3b所示，控制器12包括输入端VBULK、输入端FB、输入端VCR、输出端MDRV、输出端SDRV、PWM控制单元121和曲线控制单元122。其中，输入端VBULK和输入端FB分别连接输入电压采样模块14的输出端和隔离副边电压采样模块15的输出端，输入端VCR连接至采样电阻R 1和R 2之间的连接点上，输出端MDRV和输出端SDRV分别连接至主开关管S1的栅极和辅开关管S2的栅极。
在变换器1开始工作后，电压采样电路13开始实时采集采样电阻R 2的电压V R2，并将采样电阻R 2的电压V R2输出至控制器12的输入端VCR。其中，采样电阻R 2的电压V R2可以表征谐振电容C r的电压。控制器12中的曲线控制单元122基于采样电阻R 2的电压V R2计算得到谐振电容C r的电压V Cr＝V R2*(R 1+R 2)/R 2，进而计算得到变换器1的当前输出电压V o＝V Cr*P 1，其中，P 1为副边绕组N S与原边绕组N P之间的匝数比。
与此同时，在变换器1开始工作后，隔离副边电压采样模块15通过光耦实时采集输出电压隔离反馈信号，并将输出电压隔离反馈信号输出至控制器12的输入端FB。曲线控制单元122基于输出电压隔离反馈信号得到变换器1的当前输出电流。
曲线控制单元122从预设的多个电压区间中确定出变换器1的当前输出电压V o所在的第一电压区间。其中，预设的多个电压区间可以为图4所示的三个电压区间，即高压区间H、中压区间M和低压区间L。
具体的，以高压区间H为例，在输出电压随着时间逐渐增大的情况下，若当前输出电压V o大于或者等于电压阈值V o_hh，则曲线控制单元122确定输出电压V o从中压区间M变为高压区间H，也即确定第一电压区间为高压区间H；在输出电压随着时间逐渐减小的情况下，若当前输出电压V o大于或者等于电压阈值V o_hl，则曲线控制单元122确定第一电压区间为高压区间H。以中压区间M为例，在输出电压随着时间逐渐增大的情况下，若当前输出电压V o大于或者等于电压阈值V o_mh且小于电压阈值V o_hh，则曲线控制单元122确定第一电压区间为中压区间M；在输出电压随着时间逐渐减小的情况下，若当前输出电压V o大于或者等于电压阈值V o_ml且小于电压阈值V o_hl，则曲线控制单元122确定第一 电压区间为中压区间M。以低压区间L为例，在输出电压随着时间逐渐增大的情况下，若当前输出电压V o大于或者等于电压阈值V o_lh且小于电压阈值V o_mh，则曲线控制单元122确定第一电压区间为中压区间M；在输出电压随着时间逐渐减小的情况下，若当前输出电压V o大于或者等于电压阈值V o_ll且小于电压阈值V o_ml，则曲线控制单元122确定第一电压区间为中压区间M。
为了便于介绍，请参见图5，图5是本申请提供的变换器的模式切换示意图。之后，曲线控制单元122从与三个电压区间一一对应的三个切换电流阈值中，也即从图5所示的高压区间H对应的切换电流阈值I o1、中压区间M对应的切换电流阈值I o2和低压区间L对应的切换电流阈值I o3中，确定出上述第一电压区间对应的第一切换电流阈值。
在一可选实施例中，在上述第一电压区间为高压区间H的情况下，曲线控制单元122确定高压区间H对应的第一切换电流阈值为图5所示的I o1，并将高压区间H对应第一切换电流阈值I o1发送至PWM控制单元121。其中，高压区间H对应的第一切换电流阈值I o1为在变换器1的输出电压位于高压区间HIGH的情况下，变换器1在CRM与HBURST模式之间切换的模式切换点。
首先需要说明的是，在第一电压区间为高压区间H的情况下，第一切换电流阈值、第二切换电流阈值、第三切换电流阈值和第四切换电流阈值分别为I o1、I o2、I o4和I o3，第一导通次数、第二导通次数、第三导通次数、第四导通次数、第五导通次数和第六导通次数分别为N1、N2、N3、N4、N5和N6，第一电流峰值、第二电流峰值、第三电流峰值、第四电流峰值、第五电流峰值和第六电流峰值分别为I Lm_R1、I Lm_R2、I Lm_R3、I Lm_R4、I Lm_R5和I Lm_R6。其中，I o1＞I o2＞I o3＞0，I o1＞I o4＞0，I o2与I o4不等。N1＞N2＞N6，N3≥N4，N5＝0，N1、N2、N3、N4和N6均为正整数。I Lm_R1＞I Lm_R2＞I Lm_R6＞0，I Lm_R3≥I Lm_R4＞0，I Lm_R5＝0，I Lm_R1、I Lm_R2、I Lm_R3、I Lm_R4和I Lm_R6的取值满足变换器1的开关频率f SW小于开关频率最大值f SW(MAX)以及变换器1的工作频率(即高频间歇周期T HBURST的频率f HBURST＝1/T HBURST)处于人耳听觉范围外的条件即可。为了方便介绍，本实施例以N6＝N3，I Lm_R6＝I Lm_R3为例进行介绍。
如图5所示，在变换器1的当前输出电流I o大于第一切换电流阈值I o1的情况下，PWM控制单元121控制变换器1的开关频率f SW(即主开关管S1的开关频率)随着输出电流I o的增大而减小，或者控制变换器1的开关频率f SW随着输出电流I o的减小而增大，以使变换器1处于CRM。其中，在变换器1处于CRM模式下，变换器1的开关频率f SW随着输出电流I o的增大而减小，由于原边绕组N P的平均电流正比于副边绕组N S的平均电流，因此，励磁电感L m的电流峰值I Lm(PEAK)也随着输出电流I o的增大而增大；同理，在变换器1处于CRM模式下，变换器1的开关频率f SW随着输出电流I o的减小而增大，励磁电感L m的电流峰值I Lm(PEAK)也随着输出电流I o的减小而减小。
在变换器1的当前输出电流小于或者等于第一切换电流阈值I o1的情况下，变换器1处于HBURST模式：
具体的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在变换器1的一个工作周期(即HBURST模式下的一个高频间歇周期T HBURST)的导通次数N SW为第一导通次数N1(如3)，以使变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2(如2)，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者 等于第四切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6(如1)，变换器1仍处于HBURST模式。这里，PWM控制单元121控制变换器1处于HBURST模式的具体实现方式请参见后续实施例的描述，此处不再展开说明。
可以理解的，在变换器1处于HBURST模式的情况下，变换器1可以基于负载(即输出电流I o)的变化调整开关管(即主开关管S1和辅开关管S2)在一个高频间歇周期T HBURST内的导通次数N SW,保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。此外，由于在负载逐渐变轻(即输出电流I o逐渐变小)的过程中，开关管在一个高频间歇周期T HBURST内的导通次数N SW也逐渐减小，因此，还可降低轻载情况下变换器1的输出电压纹波，适用性强。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，PWM控制单元121还可以通过控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，PWM控制单元121控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3的情况下，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6,变换器1仍处于HBURST模式。这里，PWM控制单元121控制变换器1处于HBURST模式的具体实现方式请参见后续实施例的描述，此处不再展开说明。
可以理解的，在变换器1处于HBURST模式的情况下，变换器1可以基于负载的变化调整励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK),保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。此外，由于在负载逐渐变轻的过程中，励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)也逐渐减小，因此，还可降低轻载情况下变换器1的输出电压纹波，适用性强。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，PWM控制单元121还可以通过同时控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST内的导通次数，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2(如2)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK) 为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6(如1)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6，变换器1仍处于HBURST模式。
为了便于理解，下面以第一导通次数为3，第一电流峰值为I Lm_R1为例，对控制器12同时控制一个高频间歇周期T HBURST内的导通次数N SW和电流峰值I Lm(PEAK)，使得变换器1处于HBURST模式的具体实现方式进行介绍。
参见图6，图6是本申请提供的变换器处于HBURST模式下的控制时序图。如图6所示，在t 0时刻，高频间歇周期T HBURST开始，PWM控制单元121向辅开关管S2的栅极G_S2输出高电平，以使辅开关管S2导通，此时，主开关管S1处于关断状态。
在t 0-t 1时刻内，PWM控制单元121仍向辅开关管S2的栅极G_S2输出高电平，则辅开关管S2仍处于导通状态，从而使谐振电容C r、主开关管S1的寄生电容、辅开关管S2的寄生电容与谐振电感L r发生谐振，实现主开关管S1软开关。在该时间段内，主开关管S1仍处于关断状态。
在t 1时刻，PWM控制单元121停止向辅开关管S2的栅极G_S2输出高电平，以使辅开关管S2关断。
在t 1-t 2时刻内，主开关管S1和辅开关管S2均处于关断状态，该时间段为死区时间。
在t 2时刻，PWM控制单元121向主开关管S1的栅极G_S1输出高电平，以使主开关管S1导通，并将主开关管S1在一个高频间歇周期T HBURST的导通次数记为1。相应的，在t 2时刻，励磁电感L m的电流I Lm开始上升。
在t 2-t 3时刻内，PWM控制单元121仍向主开关管S1的栅极G_S1输出高电平，则主开关管S1仍处于导通状态。相应的，在该时间段内，励磁电感L m的电流I Lm持续上升。
在t 3时刻，励磁电感L m的电流I Lm达到第一电流峰值I Lm_R1，则PWM控制单元121停止向主开关管S1的栅极G_S1输出高电平，以使主开关管S1关断。
在t 3-t 4时刻内，主开关管S1和辅开关管S2均处于关断状态，该时间段为死区时间。在该时间段内，励磁电感L m的电流I Lm从第一电流峰值I Lm_R1开始下降。
在t 4时刻，PWM控制单元121向辅开关管S2的栅极G_S2输出高电平，以使辅开关管S2导通，并将辅开关管S2在一个高频间歇周期T HBURST的导通次数记为1。需要说明的是，高频间歇周期T HBURST开始时辅开关管S2用于实现主开关管S1软开关的导通次数并不被记录在辅开关管S2在一个高频间歇周期T HBURST的导通次数内。
在t 4-t 5时刻内，PWM控制单元121仍向辅开关管S2的栅极G_S2输出高电平，则辅开关管S2仍处于导通状态，主开关管S1处于关断状态。相应的，在该时间段内，励磁电感L m的电流I Lm仍在下降。
在t 5时刻，励磁电感L m达到伏秒平衡，则PWM控制单元121停止向辅开关管S2的栅极G_S2输出高电平，以使辅开关管S2关断。
在t 5-t 6时刻内，主开关管S1和辅开关管S2均处于关断状态，该时间段为死区时间。
在t 6-t 7时刻内，PWM控制单元121控制主开关管S1和辅开关管S2重复t 2-t 6时刻所在时间段的步骤，直至主开关管S1的导通次数和辅开关管S2的导通次数均为3。
在t 7时刻，主开关管S1的导通次数和辅开关管S2的导通次数均为3，则PWM控制单元121不再向主开关管S1的栅极G_S1和辅开关管S2的栅极G_S2输出高电平，以使 主开关管S1和辅开关管S2均关断。
在t 7-t 8时刻内，即在T SLEEP时间段内，主开关管S1和辅开关管S2均处于关断状态。
在t 8时刻，高频间歇周期T HBURST结束。
在t 8时刻后，PWM控制单元121控制主开关管S1和辅开关管S2，按照t 0-t 8时刻内的一个高频间歇周期T HBURST进行周期工作。
在本申请中，变换器1处于HBURST模式的具体实现方式均可参照图6所示实施例的描述。
可以理解的，在变换器1处于HBURST模式的情况下，变换器1可以基于负载的变化，调整开关管在一个高频间歇周期T HBURST内的导通次数N SW以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK),保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。此外，由于在负载逐渐变轻的过程中，开关管在一个高频间歇周期T HBURST内的导通次数N SW和励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)均逐渐减小，可进一步减小能量输出，因此，还可进一步降低轻载情况下变换器1的输出电压纹波，适用性更强。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式：
需要说明的是，变换器1根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式的具体实现步骤，均是基于以下五个电流区间所对应的步骤的组合所得到的。
在当前输出电流I o位于第一电流区间(I o2,I o1]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，和/或，控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1；在当前输出电流I o位于第二电流区间(I o3,I o2]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2，和/或，控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2；在当前输出电流I o位于第三电流区间(I o4,I o1]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3，和/或控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3；在当前输出电流I o位于第四电流区间(0,I o4]时，控制器12基于一个高频间歇周期T HBURST内的开关管的导通次数N SW为第四导通次数N4，和/或励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，控制变换器1处于LBURST模式；在当前输出电流I o位于第五电流区间(0,I o3]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6，和/或控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6。
显然，上述五个电流区间中均在多个电流区间重叠的情况，在上述五个电流区间之间出现一个由多个电流区间重叠所产生的重叠电流区间的情况时，PWM控制单元121可以从上述重叠的多个电流区间中选取任一电流区间或者满足变换器1的实际工况的一个电流区间作为目标电流区间，并在当前输出电流I o位于上述重叠电流区间内时，控制变换器1执行当前输出电流I o位于目标电流区间时的步骤。基于此，可以得到变换器1处于HBURST模式或者LBURST模式的控制方式多样，灵活性高。此外，I o2、I o4与I o3三者之间的大小关系多样，从而使变换器1处于HBURST模式或者LBURST模式的控制方式更加多样，灵活性更高。
为了便于介绍，下面以I o2＞I o3＞I o4为例，对变换器1处于HBURST模式或者LBURST模式进行说明。在I o2＞I o3＞I o4的情况下，由于I o1、I o2和I o3之间的大小固定，即I o1＞I o2 ＞I o3，因此可以得到第一电流区间(I o2,I o1]与第三电流区间(I o4,I o1]发生重叠且该重叠电流区间为(I o2,I o1]，控制器12可以选择第一电流区间(I o2,I o1]或者第三电流区间(I o4,I o1]作为重叠电流区间(I o2,I o1]下的目标电流区间，本实施例以第一电流区间(I o2,I o1]为重叠电流区间(I o2,I o1]下的目标电流区间为例进行介绍；第二电流区间(I o3,I o2]与第三电流区间(I o4,I o1]发生重叠且该重叠电流区间为(I o3,I o2]，控制器12可以选择第二电流区间(I o3,I o2]或者第三电流区间(I o4,I o1]作为重叠电流区间(I o3,I o2]下的目标电流区间，本实施例以第二电流区间(I o3,I o2]为重叠电流区间(I o3,I o2]下的目标电流区间为例进行介绍；第五电流区间(0,I o3]与第三电流区间(I o4,I o1]发生重叠且该重叠电流区间为(I o4,I o3]，控制器12可以选择第五电流区间(0,I o3]或者第三电流区间(I o4,I o1]作为重叠电流区间(I o4,I o3]下的目标电流区间，本实施例以第三电流区间(I o4,I o1]为重叠电流区间(I o4,I o3]下的目标电流区间为例进行介绍；第五电流区间(0,I o3]与第四电流区间(0,I o4]发生重叠且该重叠电流区间为(0,I o4]，控制器12可以选择第五电流区间(0,I o3]或者第四电流区间(0,I o4]作为重叠电流区间(0,I o4]下的目标电流区间，本实施例以第四电流区间(0,I o4]为重叠电流区间(0,I o4]下的目标电流区间为例进行介绍。
具体的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，PWM控制单元121执行当前输出电流I o位于第一电流区间(I o2,I o1]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，以使变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，PWM控制单元121执行当前输出电流I o位于第二电流区间(I o3,I o2]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2(如2)，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第三电流区间(I o4,I o1]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第四导通次数N4(如1)，并在经过一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数N SW均为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。其中，第一工作周期次数为正整数，示例性的，第一工作周期次数为3。
可以理解的，在当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，相比基于负载调整开关管在一个高频间歇周期T HBURST的导通次数N SW以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载(即输出电流I o小于或者等于第三切换电流阈值I o4)情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极 轻载情况下变换器1的输出电压纹波，适用性更强。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，PWM控制单元121还可以通过控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，PWM控制单元121执行当前输出电流I o位于第一电流区间(I o2,I o1]时的上述步骤，即通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，PWM控制单元121执行当前输出电流I o位于第二电流区间(I o3,I o2]时的上述步骤，即通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第三电流区间(I o4,I o1]时的上述步骤，即通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R3)，并在经过一个高频间歇周期T HBURST内的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。
可以理解的，在当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，相比基于负载调整励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，PWM控制单元121还可以通过同时控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST内的导通次数N SW，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，PWM控制单元121执行当前输出电流I o位于第一电流区间(I o2,I o1]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1处于HBURST 模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，PWM控制单元121执行当前输出电流I o位于第二电流区间(I o3,I o2]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2(如2)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第三电流区间(I o4,I o1]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST内的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R3)，并在经过一个高频间歇周期T HBURST内的开关管的导通次数为第四导通次数N4且励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，也即在经过第一工作周期次数个开关管的导通次数为第四导通次数N4且励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的高频间歇周期T HBURST后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。
为了便于理解，下面以第一工作周期次数和第四导通次数均为1，第四电流峰值为I Lm_R3为例，对控制器12同时控制一个高频间歇周期T HBURST内的导通次数N SW和电流峰值I Lm(PEAK)，使得变换器1处于LBURST模式的具体实现方式进行介绍。
参见图7，图7是本申请提供的变换器处于LBURST模式下的控制时序图。如图7所示，在t 0’时刻，PWM控制单元121控制主开关管S1和辅开关管S2导通或者关断，使得LBURST模式开始，也即，使得变换器1开始工作在第1个高频间歇发波周期T HBURST，其中，在一个高频间歇发波周期T HBURST内，主开关管S1和辅开关管S2的导通次数N SW为1，以及励磁电感L m的电流峰值I Lm(PEAK)为I Lm_R3。这里，变换器1工作在一个高频间歇发波周期T HBURST的具体实现方式请参见图6所示实施例对应部分的描述。
在t 0’-t 1’时刻内，PWM控制单元121控制主开关管S1和辅开关管S2导通或者关断，使得变换器1连续工作3个高频间歇发波周期T HBURST。
在t 1’时刻，变换器1已连续工作3个高频间歇发波周期T HBURST，则PWM控制单元121不再向主开关管S1的栅极G_S1和辅开关管S2的栅极G_S2输出高电平，以使主开关管S1和辅开关管S2均关断。
在t 1’时刻后，PWM控制单元121仍不再向主开关管S1的栅极G_S1和辅开关管S2的栅极G_S2输出高电平，以使主开关管S1和辅开关管S2均关断。
在本申请中，变换器1处于LBURST模式的具体实现方式均可参照图7所示实施例的 描述。
需要说明的是，当I o2、I o3和I o4三者之间的大小关系为除I o2＞I o3＞I o4之外的其他大小关系时，变换器1处于HBURST模式或者LBURST模式的具体实现方式请参见I o2＞I o3＞I o4时对应实施例的描述，此处不再赘述。
可以理解的，在当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，相比基于负载同时调整一个高频间歇周期内开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，根据变换器1的工作频率，控制变换器1处于HBURST模式或者LBURST模式：
具体的，请再参见图5，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，即当前输出电流I o位于第一电流区间(I o2,I o1]时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，以使变换器1处于HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1后，PWM控制单元121计算得到开关管(即主开关管S1和辅开关管S2的简称)的导通次数N SW为第一导通次数N1的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第四导通次数N4(如1)，并在经过一个高频间歇周期内主开关管S1和辅开关管S2的导通次数N SW均为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第五导通次数N5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。话句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1。
假设开关管的导通次数N SW为第一导通次数N1的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1。并在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，即当前输出电流I o位于第二电流区间(I o3,I o2]时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第二导通次数N2(如2)，变换器1仍处于HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2后，PWM控制单元121计算得到开关管的导通次数N SW为第二导通次数N2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位 于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2。
假设开关管的导通次数N SW为第二导通次数N2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2。并在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3的情况下，即当前输出电流I o位于第五电流区间(0,I o3]时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第六导通次数N6(如1)，变换器1仍处于HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6后，PWM控制单元121计算得到开关管的导通次数N SW为第六导通次数N6的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6。
可以理解的，在当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，相比基于负载调整开关管在一个高频间歇周期的导通次数N SW以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，PWM控制单元121还可以通过控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o位于第一电流区间(I o2,I o1]的情况下，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1处于HBURST模式。并在励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，PWM控制单元121计算得到励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，并在经过一个高频间歇周期内的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)， 也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。
假设励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。并在变换器1的当前输出电流I o位于第二电流区间(I o3,I o2]的情况下，PWM控制单元121控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。并在励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2后，PWM控制单元121计算得到励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。
假设励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。并在变换器1的当前输出电流I o位于第五电流区间(0,I o3]的情况下，PWM控制单元121控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6＝I Lm_R3，变换器1仍处于HBURST模式。并在励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6后，PWM控制单元121计算得到励磁电感L m的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6。
可以理解的，在当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下，相比基于负载调整励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o1的情况下， PWM控制单元121还可以通过同时控制主开关管S1和辅开关管S2在一个高频间歇周期内的导通次数N SW，以及励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o位于第一电流区间(I o2,I o1]的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，PWM控制单元121计算得到开关管的导通次数N SW为第一导通次数N1且励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，并在经过一个高频间歇周期内的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4且开关管的导通次数N SW为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。
假设开关管的导通次数N SW为第一导通次数N1且励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。并在变换器1的当前输出电流I o位于第二电流区间(I o3,I o2]的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第二导通次数N2(如2)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2后，PWM控制单元121计算得到开关管的导通次数N SW为第二导通次数N2且励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉 范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。
假设开关管的导通次数N SW为第二导通次数N2且励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。并在变换器1的当前输出电流I o位于第五电流区间(0,I o3]的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第六导通次数N6(如1)，并控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6，变换器1仍处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6后，PWM控制单元121计算得到开关管的导通次数N SW为第六导通次数N6且励磁电感L m的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6。
可以理解的，在当前输出电流I o小于或者等于高压区间H对应的切换电流阈值I o1的情况下，相比基于负载同时调整一个高频间歇周期内开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
需要说明的是，上述实施例均是在当前输出电压位于高压区间H的情况下，根据当前输出电流I o所在的电流区间，控制变换器1处于CRM模式或者间歇发波模式。下面结合变换器1的输出电流的变化趋势进行详细介绍。在变换器1的输出电流下降至第一切换电流阈值I o1时，变换器1从CRM模式切换至HBURST模式；为了进一步提高极轻载情况变换器1的效率，在变换器1处于HBURST模式后，在变换器1的输出电流继续下降至第三切换电流阈值I o4时，变换器1从HBURST模式切换至LBURST模式对应的。对应的，在变换器1的输出电流上升至第三切换电流阈值I o4时，变换器1从LBURST模式切换至HBURST模式；在变换器1的输出电流继续上升至第一切换电流阈值I o1时，变换器1从HBURST模式切换至CRM模式。
在另一可选实施例中，在上述第一电压区间为中压区间M的情况下，曲线控制单元122确定中压区间M对应的第一切换电流阈值为图5所示的I o2，并将中压区间M对应的 第一切换电流阈值I o2发送至PWM控制单元121。其中，中压区间M对应的第一切换电流阈值I o2为在变换器1的输出电压位于中压区间M的情况下，变换器1在CRM模式与HBURST模式之间切换的模式切换点。
首先需要说明的是，在第一电压区间为中压区间M的情况下，第一切换电流阈值、第二切换电流阈值和第三切换电流阈值分别为I o2、I o3和I o4，第一导通次数、第二导通次数、第三导通次数、第四导通次数和第五导通次数分别为N2、N6、N3、N4和N5。第一电流峰值、第二电流峰值、第三电流峰值、第四电流峰值和第五电流峰值分别为I Lm_R2、I Lm_R6、I Lm_R3、I Lm_R4和I Lm_R5。其中，I o2＞I o3＞0，I o2＞I o4＞0，I o3与I o4不等。N2＞N6，N3≥N4，N5＝0，N2、N3、N4和N6均为正整数。I Lm_R2＞I Lm_R6＞0，I Lm_R3≥I Lm_R4＞0，I Lm_R5＝0，I Lm_R2、I Lm_R3、I Lm_R4和I Lm_R6的取值满足变换器1的开关频率f SW小于开关频率最大值f SW(MAX)以及高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围外的条件即可。为了方便介绍，本实施例以N6＝N3，I Lm_R6＝I Lm_R3为例进行介绍。
如图5所示，在变换器1的当前输出电流I o大于第一切换电流阈值I o2的情况下，PWM控制单元121控制变换器1的开关频率f SW随着输出电流I o的增大而减小，或者控制变换器1的开关频率f SW随着输出电流I o的减小而增大，以使变换器1处于CRM。此外，在变换器1处于CRM模式的情况下，在同一输出电流值下，输出电压位于中压区间M时变换器1的开关频率f SW小于输出电压位于高压区间H时变换器1的开关频率f SW。
在变换器1的当前输出电流小于或者等于第一切换电流阈值I o2的情况下，变换器1处于HBURST模式：
具体的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2且大于第二切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2(如2)，以使变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6(如1)，变换器1仍处于HBURST模式。
可以理解的，在变换器1处于HBURST模式的情况下，变换器1可以基于负载的变化调整开关管在一个高频间歇周期T HBURST内的导通次数N SW,保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。此外，由于在负载逐渐变轻的过程中，开关管在一个高频间歇周期T HBURST内的导通次数N SW也逐渐减小，因此，还可降低轻载情况下变换器1的输出电压纹波，适用性强。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2的情况下，PWM控制单元121还可以通过控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2且大于第二切换电流阈值I o3的情况下，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2，变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o3的情况下，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6＝I Lm_R3，变换器1仍处于HBURST模式。这里，PWM控制单元121控制变换器1处于HBURST模式的具体实现方式请参见后续实施例的描述，此处不再展开说明。
可以理解的，在变换器1处于HBURST模式的情况下，变换器1可以基于负载的变化调整励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK),保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。此外，由于在负载逐渐变轻的过程中，励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)也逐渐减小，因此，还可降低轻载情况下变换器1的输出电压纹波，适用性强。
可选的，在变换器1的当前输出电流I o小于或者等于切换电流阈值I o2的情况下，PWM控制单元121还可以通过同时控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST内的导通次数，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2且大于第二切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2(如2)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的第一电流峰值I Lm(PEAK)为电流峰值I Lm_R2，变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6＝N3(如1)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的第二电流峰值I Lm(PEAK)为电流峰值I Lm_R6＝I Lm_R3，变换器1仍处于HBURST模式。
可以理解的，在变换器1处于HBURST模式的情况下，变换器1可以基于负载的变化，调整一个高频间歇周期T HBURST内开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。此外，由于在负载逐渐变轻的过程中，开关管在一个高频间歇周期T HBURST内的导通次数N SW和励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)均逐渐减小，可进一步减小能量输出，因此，还可进一步降低轻载情况下变换器1的输出电压纹波，适用性更强。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2的情况下，根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式：
需要说明的是，变换器1根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式的具体实现步骤，均是基于以下四个电流区间所对应的步骤的组合所得到的。
在当前输出电流I o位于第二电流区间(I o3,I o2]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，和/或，控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2；在当前输出电流I o位于第四电流区间(0,I o4]时，控制器12基于一个高频间歇周期T HBURST内的开关管的导通次数N SW为第四导通次数N4，和/或励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，控制变换器1处于LBURST模式；在当前输出电流I o位于第五电流区间(0,I o3]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6，和/或控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6；在当前输出电流I o位于第六电流区间(I o4,I o2]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3，和/或控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3。
显然，上述四个电流区间中均在多个电流区间重叠的情况，在上述四个电流区间之 间出现一个由多个电流区间重叠所产生的重叠电流区间的情况时，PWM控制单元121可以从上述重叠的多个电流区间中选取任一电流区间或者满足变换器1的实际工况的一个电流区间作为目标电流区间，并在当前输出电流I o位于上述重叠电流区间内时，控制变换器1执行当前输出电流I o位于目标电流区间时的步骤。基于此，可以得到变换器1处于HBURST模式或者LBURST模式的控制方式多样，灵活性高。此外，I o3与I o4之间的大小关系多样，从而使变换器1处于HBURST模式或者LBURST模式的控制方式更加多样，灵活性更高。
为了便于介绍，下面以I o3＞I o4为例，对变换器1处于HBURST模式或者LBURST模式进行说明。在I o2＞I o4的情况下，由于I o2＞I o3，I o2＞I o4，因此可以得到第二电流区间(I o3,I o2]与第六电流区间(I o4,I o2]发生重叠且该重叠电流区间为(I o3,I o2]，控制器12可以选择第二电流区间(I o3,I o2]或者第六电流区间(I o4,I o2]作为重叠电流区间(I o3,I o2]下的目标电流区间，本实施例以第二电流区间(I o3,I o2]为重叠电流区间(I o3,I o2]下的目标电流区间为例进行介绍；第五电流区间(0,I o3]与第六电流区间(I o4,I o2]发生重叠且该重叠电流区间为(I o4,I o3]，控制器12可以选择第五电流区间(0,I o3]或者第六电流区间(I o4,I o2]作为重叠电流区间(I o4,I o3]下的目标电流区间，本实施例以第六电流区间(I o4,I o2]为重叠电流区间(I o4,I o3]下的目标电流区间为例进行介绍；第五电流区间(0,I o3]与第四电流区间(0,I o4]发生重叠且该重叠电流区间为(0,I o4]，控制器12可以选择第五电流区间(0,I o3]或者第四电流区间(0,I o4]作为重叠电流区间(0,I o4]下的目标电流区间，本实施例以第四电流区间(0,I o4]为重叠电流区间(0,I o4]下的目标电流区间为例进行介绍。
具体的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2且大于第二切换电流阈值I o3的情况下，PWM控制单元121执行当前输出电流I o位于第二电流区间(I o3,I o2]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2(如2)，变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第六电流区间(I o4,I o2]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第四导通次数N4(如1)，并在经过一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数N SW均为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。其中，第一工作周期次数为正整数，示例性的，第一工作周期次数为3。
可以理解的，在当前输出电流I o小于或者等于中压区间M对应的第一切换电流阈值I o2的情况下，相比基于负载调整开关管在一个高频间歇周期T HBURST的导通次数N SW以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载(即输出电流I o小于或者等于第三切换电流阈值I o4)情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换 器1的效率。此外，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2的情况下，PWM控制单元121还可以通过控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2且大于第二切换电流阈值I o3的情况下，PWM控制单元121执行当前输出电流I o位于第二电流区间(I o3,I o2]时的上述步骤，即通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2，变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第六电流区间(I o4,I o2]时的上述步骤，即通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R3)，并在经过一个高频间歇周期T HBURST内的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。
可以理解的，在当前输出电流I o小于或者等于中压区间M对应的第一切换电流阈值I o2的情况下，相比基于负载调整励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2的情况下，PWM控制单元121还可以通过同时控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST内的导通次数N SW，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2且大于第二切换电流阈值I o3的情况下，PWM控制单元121执行当前输出电流I o位于第二电流区间(I o3,I o2]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2(如2)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2，变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o3且大于第三切换电 流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第六电流区间(I o4,I o2]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST内的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R3)，并在经过一个高频间歇周期T HBURST内的开关管的导通次数为第四导通次数N4且励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，也即在经过第一工作周期次数个开关管的导通次数为第四导通次数N4且励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的高频间歇周期T HBURST后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。
需要说明的是，当I o4＞I o3时，变换器1处于HBURST模式或者LBURST模式的具体实现方式请参见I o3＞I o4时对应实施例的描述，此处不再赘述。
可以理解的，在当前输出电流I o小于或者等于中压区间M对应的第一切换电流阈值I o2的情况下，相比基于负载同时调整一个高频间歇周期内开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2的情况下，根据变换器1的工作频率，控制变换器1处于HBURST模式或者LBURST模式：
具体的，请再参见图5，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2且大于第二切换电流阈值I o3的情况下，即当前输出电流I o位于第二电流区间(I o3,I o2]时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第一导通次数N2(如2)，变换器1处于HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2后，PWM控制单元121计算得到开关管的导通次数N SW为第一导通次数N2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第四导通次数N4(如1)，并在经过一个高频间歇周期内主开关管S1和辅开关管S2的导通次数N SW均为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个 高频间歇周期的导通次数N SW均为第五导通次数N5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。话句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2。
假设开关管的导通次数N SW为第一导通次数N2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2。并在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o3的情况下，即当前输出电流I o位于第五电流区间(0,I o3]时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第二导通次数N6＝N3(如1)，变换器1仍处于HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6后，PWM控制单元121计算得到开关管的导通次数N SW为第二导通次数N6的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6。
可以理解的，在当前输出电流I o小于或者等于中压区间M对应的第一切换电流阈值I o2的情况下，相比基于负载调整开关管在一个高频间歇周期的导通次数N SW以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2的情况下，PWM控制单元121还可以通过控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o位于第二电流区间(I o3,I o2]的情况下，PWM控制单元121控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2，变换器1处于HBURST模式。并在励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2后，PWM控制单元121计算得到励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。
假设励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。并在变换器1的当前输出电流I o位于第五电流区间(0,I o3]的情况下，PWM控制单元121控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6＝I Lm_R3，变换器1仍处于HBURST模式。并在励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6后，PWM控制单元121计算得到励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6。
可以理解的，在当前输出电流I o小于或者等于中压区间M对应的第一切换电流阈值I o2的情况下，相比基于负载调整励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o2的情况下，PWM控制单元121还可以通过同时控制主开关管S1和辅开关管S2在一个高频间歇周期内的导通次数N SW，以及励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o位于第二电流区间(I o3,I o2]的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第一导通次数N2(如2)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2，变换器1处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2后，PWM控制单元121计算得到开关管的导通次数N SW为第一导通次数N2且励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。
假设开关管的导通次数N SW为第一导通次数N2且励磁电感L m的电流峰值I Lm(PEAK)为第 一电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。并在变换器1的当前输出电流I o位于第五电流区间(0,I o3]的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第二导通次数N6＝N3(如1)，并控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6＝I Lm_R3，变换器1仍处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6后，PWM控制单元121计算得到开关管的导通次数N SW为第二导通次数N6且励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6。
可以理解的，在当前输出电流I o小于或者等于中压区间M对应的第一切换电流阈值I o2的情况下，相比基于负载同时调整一个高频间歇周期内开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
需要说明的是，上述实施例均是在当前输出电压位于中压区间M的情况下，根据当前输出电流I o所在的电流区间，控制变换器1处于CRM模式或者间歇发波模式。下面结合变换器1的输出电流的变化趋势进行详细介绍。在变换器1的输出电流下降至第一切换电流阈值I o2时，变换器1从CRM模式切换至HBURST模式；为了进一步提高极轻载情况变换器1的效率，在变换器1处于HBURST模式后，在变换器1的输出电流继续下降至第三切换电流阈值I o4时，变换器1从HBURST模式切换至LBURST模式。对应的，在变换器1的输出电流上升至第三切换电流阈值I o4时，变换器1从LBURST模式切换至HBURST模式；在变换器1的输出电流继续上升至第一切换电流阈值I o2时，变换器1从HBURST模式切换至CRM模式。
在又一可选实施例中，在上述第一电压区间为低压区间L的情况下，曲线控制单元122确定低压区间L对应的第一切换电流阈值为图5所示的I o3，并将低压区间L对应的第一切换电流阈值I o3发送至PWM控制单元121。其中，低压区间L对应的第一切换电流阈值I o3为在变换器1的输出电压位于低压区间L的情况下，变换器1在CRM模式与HBURST模式之间切换的模式切换点。
首先需要说明的是，在第一电压区间为低压区间L的情况下，第一切换电流阈值和第三切换电流阈值分别为I o3和I o4，第三导通次数、第四导通次数和第五导通次数分别为N3、N4和N5，第三电流峰值、第四电流峰值和第五电流峰值分别为I Lm_R3、I Lm_R4和I Lm_R5。其中，I o3＞I o4＞0。N3≥N4，N5＝0，N3和N4均为正整数。I Lm_R3≥I Lm_R4＞0，I Lm_R5＝0，I Lm_R3和I Lm_R4的取值满足变换器1的开关频率f SW小于开关频率最大值f SW(MAX)以及高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围外的条件即可。
如图5所示，在变换器1的当前输出电流I o大于第一切换电流阈值I o3的情况下，PWM控制单元121控制变换器1的开关频率f SW随着输出电流I o的增大而减小，或者控制变换器1的开关频率f SW随着输出电流I o的减小而增大，以使变换器1处于CRM。此外，在变换器1处于CRM模式的情况下，在同一输出电流值下，输出电压位于低压区间L时变换器1的开关频率f SW小于输出电压位于中压区间M时变换器1的开关频率f SW。
在变换器1的当前输出电流小于或者等于第一切换电流阈值I o3的情况下，变换器1处于HBURST模式：
具体的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，以使变换器1处于HBURST模式。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，变换器1处于HBURST模式。其中，I Lm_R3满足变换器1的开关频率f SW小于开关频率最大值f SW(MAX)以及高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围外的条件。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，以及控制主开关管S1的导通时长使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，变换器1处于HBURST模式。
可以理解的，变换器1可以基于通过调整开关管在一个高频间歇周期T HBURST内的导通次数N SW和/或励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK),使变换器1处于HBURST模式，控制方式多样，灵活性高。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式：
具体的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，即当前输出电流I o位于第七电流区间(I o4,I o3]时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第四导通次数N4(如1)，并在经过一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数N SW均为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，也即PWM控制单元121控制主开关管S1和辅开关 管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。其中，第一工作周期次数为正整数，示例性的，第一工作周期次数为3。
可以理解的，在当前输出电流I o小于或者等于低压区间L对应的第一切换电流阈值I o3的情况下，相比基于负载调整开关管在一个高频间歇周期T HBURST的导通次数N SW以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载(即输出电流I o小于或者等于切换电流阈值I o4)情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，PWM控制单元121还可以通过控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R3)，并在经过一个高频间歇周期T HBURST内的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。
可以理解的，在当前输出电流I o小于或者等于低压区间L对应的第一切换电流阈值I o3的情况下，相比基于负载调整励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，PWM控制单元121还可以通过同时控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST内的导通次数N SW，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，以及控制主开关管S1的导通时长 使得励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R3，变换器1处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST内的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R3)，并在经过一个高频间歇周期T HBURST内的开关管的导通次数为第四导通次数N4且励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，也即在经过第一工作周期次数个开关管的导通次数为第四导通次数N4且励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的高频间歇周期T HBURST后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。
可以理解的，在当前输出电流I o小于或者等于低压区间L对应的第一切换电流阈值I o3的情况下，相比基于负载同时调整一个高频间歇周期内开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，根据变换器1的工作频率，控制变换器1处于HBURST模式或者LBURST模式：
具体的，请再参见图5，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，即当前输出电流I o位于第五电流区间(0,I o3]时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第三导通次数N3(如N3＝N4＝1)，变换器1处于HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3后，PWM控制单元121计算得到开关管的导通次数N SW为第三导通次数N3的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第四导通次数N4(如1)，并在经过一个高频间歇周期内主开关管S1和辅开关管S2的导通次数N SW均为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第五导通次数N5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。话句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3。
可以理解的，在当前输出电流I o小于或者等于低压区间L对应的第一切换电流阈值I o3的情况下，相比基于负载调整开关管在一个高频间歇周期的导通次数N SW以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，PWM控制单元121还可以通过控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o位于第五电流区间(0,I o3]的情况下，PWM控制单元121控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，变换器1处于HBURST模式。并在励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3后，PWM控制单元121计算得到励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3。
可以理解的，在当前输出电流I o小于或者等于低压区间L对应的第一切换电流阈值I o3的情况下，相比基于负载调整励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
可选的，在变换器1的当前输出电流I o小于或者等于第一切换电流阈值I o3的情况下，PWM控制单元121还可以通过同时控制主开关管S1和辅开关管S2在一个高频间歇周期内的导通次数N SW，以及励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)，使变换器1处于HBURST模式或者LBURST模式。
在变换器1的当前输出电流I o位于第五电流区间(0,I o3]的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第三导通次数N3(如N3＝N4＝1)，并控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3(如I Lm_R3＝I Lm_R4)，变换器1处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3后，PWM控制单元121计算得到开关管的导通次数N SW为第三导通次数N3且励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范 围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3。
可以理解的，在当前输出电流I o小于或者等于低压区间L对应的第一切换电流阈值I o3的情况下，相比基于负载同时调整一个高频间歇周期内开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。此外，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
需要说明的是，上述实施例均是在当前输出电压位于低压区间L的情况下，根据当前输出电流I o所在的电流区间，控制变换器1处于CRM模式或者间歇发波模式。下面结合变换器1的输出电流的变化趋势进行详细介绍。在变换器1的输出电流下降至第一切换电流阈值I o3时，变换器1从CRM模式切换至HBURST模式；为了进一步提高极轻载情况变换器1的效率，在变换器1处于HBURST模式后，在变换器1的输出电流下降至第三切换电流阈值I o4时，变换器1从HBURST模式切换至LBURST模式。对应的，在变换器1的输出电流上升至第三切换电流阈值I o4时，变换器1从LBURST模式切换至HBURST模式；在变换器1的输出电流上升至第一切换电流阈值I o3时，变换器1从HBURST模式切换至CRM模式。
综上可知，中压区间M对应的第一切换电流阈值I o2小于高压区间H对应的第一切换电流阈值I o1且大于低压区间L对应的第一切换电流阈值I o3。话句话说，在变换器1在CRM模式与HBURST模式之间切换时，输出电压位于中压区间M时的模式切换点小于输出电压位于高压区间H时的模式切换点，且大于输出电压位于低压区间L时的模式切换点。
中压区间M对应的第一导通次数N2小于高压区间H对应的第一导通次数N1且大于低压区间L对应的第三导通次数N3，中压区间M对应的第一电流峰值I Lm_R2小于高压区间H对应的第一电流峰值I Lm_R1且大于低压区间L对应的第三电流峰值I Lm_R3。话句话说，在变换器1从CRM模式进入HBURST模式时，随着输出电压所在电压区间的档位逐渐变低，进入HBURST模式时的工作参数也逐渐降低，其中，工作参数为一个高频间隙周期内的开关管的导通次数和/或励磁电感的电流峰值。为了方便描述，以下将将入HBURST模式时的工作参数简称成HBURST模式进入点。输出电压位于中压区间M时的HBURST模式进入点小于输出电压位于高压区间H时的HBURST模式进入点，且大于输出电压位于低压区间L时的HBURST模式进入点。
由于本申请在输出电压位于中压区间M时变换器1的模式切换点和HBURST模式进入点，相较于输出电压位于高压区间H时均有降低，因此，相较于针对不同输出电压均采用相同的模式切换点和HBURST模式进入点而言，本申请在输出电压位于中压区间M时的模式切换点更低、HBURST模式进入点更小，可降低每次高频间歇周期传输的能量，从而降低原副边绕组损耗和开关管导通损耗，进而提高变换器1处于HBURST模式下的效率。由于输出电压位于低压区间L时的变换器1的模式切换点和HBURST模式进入点，相较于 输出电压位于中压区间M时均更低，因此可进一步降低每次高频间歇周期传输的能量，从而进一步降低原副边绕组损耗和开关管导通损耗，进而进一步提高变换器1处于HBURST模式下的效率。此外，由于输出电压位于低压区间L时每次高频间歇周期传输的能量得到了进一步降低，因此，可将HBURST模式频率(高频间歇周期的频率)到达人耳可听频率点对应的负载点降至更低，优化了极低负载下的电源纹波。
在本实施方式中，变换器1可以根据不同输出电压调整变换器1的模式切换点和HBURST模式进入点，从而降低原副边绕组损耗与开关管导通损耗，进而可优化变换器1在全范围输出电压下的效率。此外，变换器1还可以在处于HBURST模式时，根据负载变化调整一个高频间歇周期内开关管的导通次数和/或励磁电感的电流峰值，可降低极轻载情况下输出电压的纹波。
在另一可选实施方式中，在变换器1开始工作后，控制器12获取变换器1的当前开关频率和当前输出电压，并在当前开关频率达到频率阈值的情况下，根据当前输出电压得到变换器1处于第二工作模式下的第一工作参数，从而基于第一工作参数控制变换器1从第一工作模式切换至第二工作模式。其中，第一工作参数包括主开关管S1和辅开关管S2在一个高频间歇周期内的导通次数，或者励磁电感在一个高频间歇周期内的电流峰值。
具体的，在变换器1开始工作后，曲线控制单元122基于电压采样电路13采集到的采样电阻R 2的电压V R2，计算得到变换器1的当前输出电压V o，与此同时，曲线控制单元122获取变换器1的当前开关频率f SW。并在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图4所示的三个电压区间(即高压区间H、中压区间M和低压区间L)中，确定出变换器1的输出电压V o所在的第一电压区间，从而从与三个电压区间一一对应的三个工作参数中确定出第一电压区间对应的第一工作参数。并基于第一工作参数控制变换器1从CRM模式切换至HBURST模式。其中，中压区间M对应的工作参数小于高压区间H对应的工作参数且大于低压区间L对应的工作参数。具体来讲，输出电压位于中压区间M时的HBURST模式进入点小于输出电压位于高压区间H时的HBURST模式进入点，且大于输出电压位于低压区间L时的HBURST模式进入点。
在一可选实施例中，请再参见图5，在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图4所示的三个电压区间中，确定出变换器1的输出电压V o所在的第一电压区间为高压区间H。
首先需要说明的是，在第一电压区间为高压区间H的情况下，第一切换电流阈值、第二切换电流阈值、第三切换电流阈值和第四切换电流阈值分别为I o1、I o2、I o4和I o3，第一导通次数、第二导通次数、第三导通次数、第四导通次数、第五导通次数和第六导通次数分别为N1、N2、N3、N4、N5和N6，第一电流峰值、第二电流峰值、第三电流峰值、第四电流峰值、第五电流峰值和第六电流峰值分别为I Lm_R1、I Lm_R2、I Lm_R3、I Lm_R4、I Lm_R5和I Lm_R6。其中，I o1＞I o2＞I o3＞0，I o1＞I o4＞0，I o2与I o4不等。N1＞N2＞N6，N3≥N4，N5＝0，N1、N2、N3、N4和N6均为正整数。I Lm_R1＞I Lm_R2＞I Lm_R6＞0，I Lm_R3≥I Lm_R4＞0，I Lm_R5＝0，I Lm_R1、I Lm_R2、I Lm_R3、I Lm_R4和I Lm_R6的取值满足变换器1的开关频率f SW小于开关频率最大值f SW(MAX)以及高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围外的条件即可。
进而，曲线控制单元122确定出高压区间H对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第一导通次数N1和/或励磁电感L m的第一电流峰值I Lm_R1，并 将高压区间H对应的工作参数发送至PWM控制单元121。
具体的，以高压区间H对应的工作参数为主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的第一导通次数N1为例，PWM控制单元121在接收到该工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，以使变换器1从CRM模式切换至HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1后，PWM控制单元121比较变换器1的当前输出电流I o与第二切换电流阈值I o2、第四切换电流阈值I o3之间的大小。在当前输出电流I o大于第二切换电流阈值I o2且小于等于第一切换电流阈值I o1时，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1。在当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2(如2)。在当前输出电流I o小于或者等于第四切换电流阈值I o3时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6(如1)。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，变换器1可以基于负载的变化调整开关管在一个高频间歇周期T HBURST内的导通次数N SW,保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。再者，由于在负载逐渐变轻的过程中，开关管在一个高频间歇周期T HBURST内的导通次数N SW也逐渐减小，因此，还可降低轻载情况下变换器1的输出电压纹波，适用性强。
可选的，高压区间H对应的工作参数还可以为励磁电感L m在一个高频间歇周期T HBURST内的第一电流峰值I Lm_R1。
PWM控制单元121在接收到高压区间H对应的工作参数后，控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，从而使得变换器1从CRM模式切换至HBURST模式。并在励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，PWM控制单元121比较变换器1的当前输出电流I o与第二切换电流阈值I o2、第四切换电流阈值I o3之间的大小。在当前输出电流I o大于第二切换电流阈值I o2且小于或者等于第一切换电流阈值I o1时，PWM控制单元121继续控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。在当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3时，PWM控制单元121控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。在当前输出电流I o小于或者等于第四切换电流阈值I o3时，PWM控制单元121控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，变换器1可以基于负载的变化调整励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK),保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。再者，由于在负载逐渐变轻的过程中，励磁电感L m在一个高频间歇周期T HBURST内的电 流峰值I Lm(PEAK)也逐渐减小，因此，还可降低轻载情况下变换器1的输出电压纹波，适用性强。
可选的，高压区间H对应的工作参数还可以为励磁电感L m在一个高频间歇周期T HBURST内的第一电流峰值I Lm_R1，以及开关管在一个高频间歇周期T HBURST的第一导通次数N1。
PWM控制单元121在接收到高压区间H对应的工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，从而使得变换器1从CRM模式切换至HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，PWM控制单元121比较变换器1的当前输出电流I o与第二切换电流阈值I o2、第四切换电流阈值I o3之间的大小。在当前输出电流I o大于第二切换电流阈值I o2且小于或者等于第一切换电流阈值I o1时，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，并继续控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。在当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2，并控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。在当前输出电流I o小于或者等于第四切换电流阈值I o3时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6，并控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6。
需要说明的是，在变换器1从CRM模式切换至HBURST模式后，上述实施例均是基于当前输出电流I o所在的电流区间，控制变换器1处于HBURST模式。下面结合变换器1的输出电流的变化趋势进行示例介绍。在变换器1从CRM模式切换至HBURST模式后，变换器1在输出电流降低的过程中降低HBURST模式下的工作参数，如在输出电流下降至第二切换电流阈值I o2时，变换器1降低一个高频间歇周期T HBURST内的开关管的导通次数和/或励磁电感的电流峰值。在输出电流继续下降至第四切换电流阈值I o3时，变换器1进一步降低一个高频间歇周期T HBURST内的开关管的导通次数和/或励磁电感的电流峰值。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，变换器1可以基于负载的变化，调整一个高频间歇周期T HBURST内开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。再者，由于在负载逐渐变轻的过程中，开关管在一个高频间歇周期T HBURST内的导通次数N SW和励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)均逐渐减小，可进一步减小能量输出，因此，还可进一步降低轻载情况下变换器1的输出电压纹波，适用性更强。
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，控制变换器1处于HBURST模式，并在变换器1处于HBURST模式后，根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式的具体实现方式可以是以下两个可选实施例的组合：
在一可选实施例中，高压区间H对应的工作参数包括一个高频间歇周期T HBURST内开关管 的第一导通次数N1，和/或，励磁电感L m的第一电流峰值I Lm_R1；
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N1，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。并在一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数均为第一导通次数N1，和/或，励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，若变换器1的输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3时，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第二导通次数N2，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2；若变换器1的输出电流I o小于或者等于第四切换电流阈值I o3时，则控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第六导通次数N6，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6；若变换器的输出电流I o大于第二切换电流阈值I o2且小于等于第一切换电流阈值I o1，则控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N1，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。
在另一可选实施例中，高压区间H对应的工作参数包括一个高频间歇周期T HBURST内开关管的第三导通次数N3＝N1，和/或，励磁电感L m的第三电流峰值I Lm_R3＝I Lm_R1；
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N1，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R1。并在一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数均为第一导通次数N1，和/或，励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R1后，若变换器的输出电流I o小于或者等于第三切换电流阈值I o4，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第四导通次数N4，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4；并在经过一个高频间歇周期T HBURST内的开关管的导通次数为第四导通次数N4，和/或，一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第五导通次数N5，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5；若变换器的输出电流I o小于或者等于第一切换电流阈值I o1且大于第三切换电流阈值I o4，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N1，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R1。
具体来讲，在变换器1切换至HBURST模式后，根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式的具体实现步骤，均是基于以下五个电流区间所对应的步骤的组合所得到的。
在当前输出电流I o位于第一电流区间(I o2,I o1]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，和/或，控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。在当前输出电流I o位于第二电流区间(I o3,I o2]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2，和/或，控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。在当前输出电流I o位于第三电流区间(I o4,I o1]时，控制器12控制开关管在一 个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，和/或，控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R1。在当前输出电流I o位于第四电流区间(0,I o4]时，控制器12基于一个高频间歇周期T HBURST内的开关管的导通次数N SW为第四导通次数N4，和/或励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，控制变换器1处于LBURST模式。在当前输出电流I o位于第五电流区间(﹣0,I o3]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6，和/或控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6。
显然，上述五个电流区间中均在多个电流区间重叠的情况，在上述五个电流区间之间出现一个由多个电流区间重叠所产生的重叠电流区间的情况时，PWM控制单元121可以从上述重叠的多个电流区间中选取任一电流区间或者满足变换器1的实际工况的一个电流区间作为目标电流区间，并在当前输出电流I o位于上述重叠电流区间内时，控制变换器1执行当前输出电流I o位于目标电流区间时的步骤。基于此，可以得到变换器1处于HBURST模式或者LBURST模式的控制方式多样，灵活性高。此外，I o4、I o2和I o3三者之间的大小关系多样，从而使变换器1处于HBURST模式或者LBURST模式的控制方式更加多样，灵活性更高。
为了便于介绍，下面以I o2＞I o3＞I o4为例，对变换器1处于HBURST模式或者LBURST模式进行说明。在I o2＞I o3＞I o4的情况下，可以得到第一电流区间(I o2,I o1]与第三电流区间(I o4,I o1]发生重叠且该重叠电流区间为(I o2,I o1]，控制器12可以选择第一电流区间(I o2,I o1]或者第三电流区间(I o4,I o1]作为重叠电流区间(I o2,I o1]下的目标电流区间，本实施例以第一电流区间(I o2,I o1]为重叠电流区间(I o2,I o1]下的目标电流区间为例进行介绍；第二电流区间(I o3,I o2]与第三电流区间(I o4,I o1]发生重叠且该重叠电流区间为(I o3,I o2]，控制器12可以选择第二电流区间(I o3,I o2]或者第三电流区间(I o4,I o1]作为重叠电流区间(I o3,I o2]下的目标电流区间，本实施例以第二电流区间(I o3,I o2]为重叠电流区间(I o3,I o2]下的目标电流区间为例进行介绍；第五电流区间(0,I o3]与第三电流区间(I o4,I o1]发生重叠且该重叠电流区间为(I o4,I o3]，控制器12可以选择第五电流区间(0,I o3]或者第三电流区间(I o4,I o1]作为重叠电流区间(I o4,I o3]下的目标电流区间，本实施例以第五电流区间(0,I o3]为重叠电流区间(I o4,I o3]下的目标电流区间为例进行介绍；第五电流区间(0,I o3]与第四电流区间(0,I o4]发生重叠且该重叠电流区间为(0,I o4]，控制器12可以选择第五电流区间(0,I o3]或者第四电流区间(0,I o4]作为重叠电流区间(0,I o4]下的目标电流区间，本实施例以第四电流区间(0,I o4]为重叠电流区间(0,I o4]下的目标电流区间为例进行介绍。
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图4所示的三个电压区间中，确定出变换器1的输出电压V o所在的第一电压区间为高压区间H。进而，曲线控制单元122确定出高压区间H对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第一导通次数N1和/或励磁电感L m的第一电流峰值I Lm_R1，并将该工作参数发送至PWM控制单元121。
具体的，以高压区间H对应的工作参数为一个高频间歇周期T HBURST内的开关管的第一导通次数N1为例，PWM控制单元121在接收到该工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，以使变换器1从CRM模式切换至HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1后，PWM控制单元121比较变换器1的当前输出电流I o与第二切换电流阈值I o2、第三切换电流阈值I o4和第四切换电流阈值I o3之间的 大小。在当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，变换器1仍处于HBURST模式。在当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，PWM控制单元121执行当前输出电流I o位于第二电流区间(I o3,I o2]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2(如2)，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第五电流区间(0,I o3]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6(如1)，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第四导通次数N4(如1)，并在经过一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数N SW均为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。其中，第一工作周期次数为正整数，示例性的，第一工作周期次数为3。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载调整开关管在一个高频间歇周期T HBURST的导通次数N SW以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载(即输出电流I o小于或者等于第三切换电流阈值I o4)情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
可选的，高压区间H对应的工作参数还可以为励磁电感L m在一个高频间歇周期T HBURST内的第一电流峰值I Lm_R1。
PWM控制单元121在接收到高压区间H对应的工作参数后，控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1从CRM模式切换至HBURST模式。并在励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，PWM控制单元121比较变换器1的当前输出电流I o与第二切换电流阈值I o2、第三切换电流阈值I o4和第四切换电流阈值I o3之间的大小。在当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，变换器1仍处于HBURST模式。在当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，PWM控制单元121执行当前输出电流I o位于第二电流区间(I o3,I o2]时的上述步骤，即控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期 T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第五电流区间(0,I o3]时的上述步骤，即控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R6)，并在经过一个高频间歇周期T HBURST内的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。其中，第一工作周期次数为正整数，示例性的，第一工作周期次数为3。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载调整励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
可选的，高压区间H对应的工作参数还可以为励磁电感L m在一个高频间歇周期T HBURST内的第一电流峰值I Lm_R1，以及开关管在一个高频间歇周期T HBURST的第一导通次数N1。
PWM控制单元121在接收到高压区间H对应的工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1从CRM模式切换至HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，PWM控制单元121比较变换器1的当前输出电流I o与第二切换电流阈值I o2、第三切换电流阈值I o4和第四切换电流阈值I o3之间的大小。在当前输出电流I o小于或者等于第一切换电流阈值I o1且大于第二切换电流阈值I o2的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，变换器1仍处于HBURST模式。在当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，PWM控制单元121执行当前输出电流I o位于第二电流区间(I o3,I o2]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2(如2)，并控制主开关管S1的导通时长以使励磁电感L m 在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第五电流区间(0,I o3]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R6)，并在经过一个高频间歇周期T HBURST内的开关管的导通次数N SW为第四导通次数N4且励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。其中，第一工作周期次数为正整数，示例性的，第一工作周期次数为3。
需要说明的是，在变换器1从CRM模式切换至HBURST模式后，上述实施例均是基于当前输出电流I o所在的电流区间，控制变换器1处于HBURST模式或者LBURST模式。下面结合变换器1的输出电流的变化趋势进行示例介绍。在变换器1从CRM模式切换至HBURST模式后，变换器1在输出电流降低的过程中降低HBURST模式下的工作参数，如在输出电流下降至切换电流阈值I o2时，变换器1降低一个高频间歇周期T HBURST内的开关管的导通次数和/或励磁电感的电流峰值；在输出电流继续下降至切换电流阈值I o3时，变换器1进一步降低一个高频间歇周期T HBURST内的开关管的导通次数和/或励磁电感的电流峰值。之后，在变换器1的输出电流继续下降至切换电流阈值I o4时，变换器1从HBURST模式切换至LBURST模式；对应的，在变换器1的输出电流上升至切换电流阈值I o4时，变换器1从LBURST模式切换至HBURST模式。
此外，当I o4、I o2和I o3三者之间的大小关系为除I o2＞I o3＞I o4之外的其他大小关系时，在不对称变换器1处于HBURST模式后，变换器1基于输出电流I o处于HBURST模式或者LBURST模式的具体实现方式请参见本实施例中I o2＞I o3＞I o4时的对应描述，此处不再赘述。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载同时调整一个高频间歇周期内的开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例还可进一步降低极轻载情况下变 换器1的输出电压纹波，适用性更强。
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，控制变换器1处于HBURST模式，并在变换器1处于HBURST模式后，根据高频间歇周期T HBURST的频率f HBURST控制变换器1处于HBURST模式或者LBURST模式的具体实现方式可以是以下两个可选实施例的组合：
在一可选实施例中，高压区间H对应的工作参数包括一个高频间歇周期T HBURST内开关管的第一导通次数N1，和/或，励磁电感L m的第一电流峰值I Lm_R1；
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N1，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。并在一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数均为第一导通次数N1，和/或，励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，若变换器的输出电流I o大于第二切换电流阈值I o2且小于等于第一切换电流阈值I o1，则控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N1，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1；若变换器1的输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3时，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第二导通次数N2，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2；若变换器1的输出电流I o小于或者等于第四切换电流阈值I o3时，则控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第六导通次数N6，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6。
在另一可选实施例中，高压区间H对应的工作参数包括一个高频间歇周期T HBURST内开关管的第三导通次数N3＝N1、N2或N6，和/或，励磁电感L m的第三电流峰值I Lm_R3＝I Lm_R1、I Lm_R2或I Lm_R6；
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第三导通次数N3，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3。并在一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数均为第三导通次数N3，和/或，励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3后，若开关管的导通次数为第三导通次数N3和/或励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3的高频间歇周期T HBURST的频率f HBURST位于预设频率范围内，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第四导通次数N4，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4；并在经过一个高频间歇周期T HBURST内的开关管的导通次数为第四导通次数N4，和/或，一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第五导通次数N5，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5；若开关管的导通次数为第三导通次数N3和/或励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3的高频间歇周期T HBURST的频率f HBURST位于预设频率范围外，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第三导通次数N3，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3。
具体的，在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图 4所示的三个电压区间中，确定出变换器1的输出电压V o所在的第一电压区间为高压区间H。进而，曲线控制单元122确定出高压区间H对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第一导通次数N1。
PWM控制单元121在接收到该工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，以使变换器1从CRM模式切换至HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1后，PWM控制单元121计算得到开关管的导通次数N SW为第一导通次数N1的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第四导通次数N4(如1)，并在经过一个高频间歇周期内主开关管S1和辅开关管S2的导通次数N SW均为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第五导通次数N5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。话句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1。
假设开关管的导通次数N SW为第一导通次数N1的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1。并在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o2且大于第四切换电流阈值I o3的情况下，即当前输出电流I o位于第二电流区间(I o3,I o2]时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第二导通次数N2(如2)，变换器1仍处于HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2后，PWM控制单元121计算得到开关管的导通次数N SW为第二导通次数N2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2。
假设开关管的导通次数N SW为第二导通次数N2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2。并在变换器1的当前输出电流I o小于或者等于第四切换电流阈值I o3的情况下，即当前输出电流I o位于第五电流区间(0,I o3]时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第六导通次数N6(如1)，变换器1仍处于HBURST模式。并在主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6后，PWM控制单元121计算得到开关管的导通次数N SW为第六导通次数N6的高频间歇周期T HBURST的频率 f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载调整开关管在一个高频间歇周期的导通次数N SW以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
可选的，高压区间H对应的工作参数还可以为励磁电感L m在一个高频间歇周期内的第一电流峰值I Lm_R1。
PWM控制单元121在接收到高压区间H对应的工作参数后，通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1处于HBURST模式。并在励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，PWM控制单元121计算得到励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，并在经过一个高频间歇周期内的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，PWM控制单元121通过控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。
假设励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。并在变换器1的当前输出电流I o位于第二电流区间(I o3,I o2]的情况下，PWM控制单元121控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。并在励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为电流峰值I Lm_R2后，PWM控制单元121计算得到励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单 元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。
假设励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。并在变换器1的当前输出电流I o位于第五电流区间(0,I o3]的情况下，PWM控制单元121控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6，变换器1仍处于HBURST模式。并在励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6后，PWM控制单元121计算得到励磁电感L m的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载调整励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
可选的，高压区间H对应的工作参数还可以为励磁电感L m在一个高频间歇周期T HBURST内的第一电流峰值I Lm_R1，以及开关管在一个高频间歇周期T HBURST的第一导通次数N1。
PWM控制单元121在接收到高压区间H对应的工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1(如3)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1，以使变换器1处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1后，PWM控制单元121计算得到开关管的导通次数N SW为第一导通次数N1且励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，并在经过一个高频间歇周期内的励磁电感L m的电流峰值I Lm(PEAK)为 第四电流峰值I Lm_R4且开关管的导通次数N SW为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。
假设开关管的导通次数N SW为第一导通次数N1且励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N1，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R1。并在变换器1的当前输出电流I o位于第二电流区间(I o3,I o2]的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第二导通次数N2(如2)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2，变换器1仍处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2后，PWM控制单元121计算得到开关管的导通次数N SW为第二导通次数N2且励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。
假设开关管的导通次数N SW为第二导通次数N2且励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N2，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R2。并在变换器1的当前输出电流I o位于第五电流区间(0,I o3]的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第六导通次数N6(如1)，并控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6，变换器1仍处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6后，PWM控制单元121计算得到开关管的导通次数N SW为第六导通次数N6且励磁电感L m的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判 断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第六导通次数N6，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第六电流峰值I Lm_R6。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载同时调整一个高频间歇周期内的开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
在另一可选实施例中，请再参见图5，在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图4所示的三个电压区间中，确定出变换器1的输出电压V o所在的第一电压区间为中压区间M。
首先需要说明的是，在第一电压区间为中压区间M的情况下，第一切换电流阈值、第二切换电流阈值和第三切换电流阈值分别为I o2、I o3和I o4，第一导通次数、第二导通次数、第三导通次数、第四导通次数和第五导通次数分别为N2、N6、N3、N4和N5，第一电流峰值、第二电流峰值、第三电流峰值、第四电流峰值和第五电流峰值分别为I Lm_R2、I Lm_R6、I Lm_R3、I Lm_R4和I Lm_R5。其中，I o2＞I o3＞0，I o2＞I o4＞0，I o3与I o4不等。N2＞N6，N3≥N4，N5＝0，N2、N3、N4和N6均为正整数。I Lm_R2＞I Lm_R6＞0，I Lm_R3≥I Lm_R4＞0，I Lm_R5＝0，I Lm_R2、I Lm_R3、I Lm_R4和I Lm_R6的取值满足变换器1的开关频率f SW小于开关频率最大值f SW(MAX)以及高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围外的条件即可。
进而，曲线控制单元122确定出中压区间M对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第一导通次数N2和/或励磁电感L m的第一电流峰值I Lm_R2，并将该工作参数发送至PWM控制单元121。
具体的，为了便于介绍，以下以中压区间M对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第一导通次数N2和励磁电感L m的第一电流峰值I Lm_R2为例进行介绍。
PWM控制单元121在接收到中压区间M对应的工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，并控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2后，PWM控制单元121比较变换器1的当前输出电流I o与第二切换电流阈值I o3之间的大小。在当前输出电流I o大于第二切换电流阈值I o3且小于等于第一切换电流阈值I o2时，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，并继续 控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。在当前输出电流I o小于或者等于第二切换电流阈值I o3时，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6，并控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6。
这里，当中压区间M对应的工作参数为第一导通次数N2或第一电流峰值I Lm_R2时，变换器1的工作原理均可参照本实施例的描述，此处不再赘述。
需要说明的是，在变换器1从CRM模式切换至HBURST模式后，上述实施例均是基于当前输出电流I o所在的电流区间，控制变换器1处于HBURST模式。下面结合变换器1的输出电流的变化趋势进行示例介绍。在变换器1从CRM模式切换至HBURST模式后，变换器1在输出电流降低的过程中降低HBURST模式下的工作参数，如在输出电流下降至第二切换电流阈值I o3时，变换器1降低一个高频间歇周期T HBURST内的开关管的导通次数和/或励磁电感的电流峰值。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，变换器1可以基于负载的变化，调整一个高频间歇周期T HBURST内开关管的导通次数N SW以及励磁电感L m的电流峰值I Lm(PEAK),保证按需输出，避免输出多于负载所需的情况，从而降低能源损耗和开关管损耗，进而提高变换器1的效率。再者，由于在负载逐渐变轻的过程中，开关管在一个高频间歇周期T HBURST内的导通次数N SW和励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)均逐渐减小，可进一步减小能量输出，因此，还可进一步降低轻载情况下变换器1的输出电压纹波，适用性更强。
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，控制变换器1处于HBURST模式，并在变换器1处于HBURST模式后，根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式的具体实现方式可以是以下两个可选实施例的组合：
在一可选实施例中，中压区间M对应的工作参数包括一个高频间歇周期T HBURST内开关管的第一导通次数N2，和/或，励磁电感L m的第一电流峰值I Lm_R2；
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N2，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。并在一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数均为第一导通次数N2，和/或，励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2后，若变换器1的输出电流I o小于或者等于第二切换电流阈值I o3时，则控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第二导通次数N6，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6；若变换器的输出电流I o大于第二切换电流阈值I o3且小于等于第一切换电流阈值I o2，则控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N2，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。
在另一可选实施例中，中压区间M对应的工作参数包括一个高频间歇周期T HBURST内开关管的第三导通次数N3＝N2，和/或，励磁电感L m的第三电流峰值I Lm_R3＝I Lm_R2；
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第三导通次数N2，和/或，控制 一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R2。并在一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数均为第三导通次数N2，和/或，励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R2后，若变换器的输出电流I o小于或者等于第三切换电流阈值I o4，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第四导通次数N4，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4；并在经过一个高频间歇周期T HBURST内的开关管的导通次数为第四导通次数N4，和/或，一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第五导通次数N5，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5；若变换器的输出电流I o小于或者等于第一切换电流阈值I o2且大于第三切换电流阈值I o4，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第三导通次数N2，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R2。
具体来讲，在变换器1切换至HBURST模式后，根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式的具体实现步骤，均是基于以下四个电流区间所对应的步骤的组合所得到的。
在当前输出电流I o位于第四电流区间(0,I o4]时，控制器12基于一个高频间歇周期T HBURST内的开关管的导通次数N SW为第四导通次数N4，和/或励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，控制变换器1处于LBURST模式；在当前输出电流I o位于第五电流区间(0,I o3]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6，和/或控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6；在当前输出电流I o位于第二电流区间(I o3,I o2]或者第六电流区间(I o4,I o2]时，控制器12控制开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，和/或，控制励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。
显然，上述四个电流区间中均在多个电流区间重叠的情况，在上述四个电流区间之间出现一个由多个电流区间重叠所产生的重叠电流区间的情况时，PWM控制单元121可以从上述重叠的多个电流区间中选取任一电流区间或者满足变换器1的实际工况的一个电流区间作为目标电流区间，并在当前输出电流I o位于上述重叠电流区间内时，控制变换器1执行当前输出电流I o位于目标电流区间时的步骤。基于此，可以得到变换器1处于HBURST模式或者LBURST模式的控制方式多样，灵活性高。此外，I o4和I o3之间的大小关系多样，从而使变换器1处于HBURST模式或者LBURST模式的控制方式更加多样，灵活性更高。
为了便于介绍，下面以I o3＞I o4为例，对变换器1处于HBURST模式或者LBURST模式进行说明。在I o3＞I o4的情况下，可以得到第二电流区间(I o4,I o2]与第六电流区间(I o3,I o2]发生重叠且该重叠电流区间为(I o3,I o2]，控制器12可以选择第二电流区间(I o4,I o2]或者第六电流区间(I o4,I o2]作为重叠电流区间(I o3,I o2]下的目标电流区间，本实施例以第二电流区间(I o4,I o2]为重叠电流区间(I o3,I o2]下的目标电流区间为例进行介绍；第五电流区间(0,I o3]与第六电流区间(I o4,I o2]发生重叠且该重叠电流区间为(I o4,I o3]，控制器12可以选择第五电流区间(0,I o3]或者第六电流区间(I o4,I o2]作为重叠电流区间(I o4,I o3]下的目标电流区间，本实施例以第五电流区间(0,I o3]为重叠电流区间(I o4,I o3]下的目标电流区间为例进行介绍；第五电流区间(0,I o3]与第四电流区间(0,I o4]发生重叠且该重叠电流区间为 (0,I o4]，控制器12可以选择第五电流区间(0,I o3]或者第四电流区间(0,I o4]作为重叠电流区间(0,I o4]下的目标电流区间，本实施例以第四电流区间(0,I o4]为重叠电流区间(0,I o4]下的目标电流区间为例进行介绍。
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图4所示的三个电压区间中，确定出变换器1的输出电压V o所在的第一电压区间为中压区间M。进而，曲线控制单元122确定出中压区间M对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第一导通次数N2和/或励磁电感L m的第一电流峰值I Lm_R2，并将该工作参数发送至PWM控制单元121。
为了便于介绍，以下以中压区间M对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第一导通次数N2和励磁电感L m的第一电流峰值I Lm_R2为例进行介绍。
具体的，PWM控制单元121在接收到中压区间M对应的工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2(如2)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2，以使变换器1从CRM模式切换至HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2后，PWM控制单元121比较变换器1的当前输出电流I o与第二切换电流阈值I o3、第三切换电流阈值I o4之间的大小。在当前输出电流I o小于或者等于第一切换电流阈值I o2且大于第二切换电流阈值I o3的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o3且大于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第五电流区间(0,I o3]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R6)，并在经过一个高频间歇周期T HBURST内的开关管的导通次数N SW为导通次数N4且励磁电感L m的电流峰值I Lm(PEAK)为电流峰值I Lm_R4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第三切换电流阈值I o4的情况下，变换器1处于LBURST模式。其中，第一工作周期次数为正整数，示例性的，第一工作周期次数为3。
这里，当中压区间M对应的工作参数为第一导通次数N2或第一电流峰值I Lm_R2时，变换器1的工作原理均可参照本实施例的描述，此处不再赘述。
需要说明的是，在变换器1从CRM模式切换至HBURST模式后，上述实施例均是基于当前输出电流I o所在的电流区间，控制变换器1处于HBURST模式或者LBURST模式。下面结合变换器1的输出电流的变化趋势进行示例介绍。在变换器1从CRM模式切换至HBURST模式后，变换器1在输出电流降低的过程中降低HBURST模式下的工作参数，如在输出电流继续下降至切换电流阈值I o3时，变换器1降低一个高频间歇周期T HBURST内的开关管的导通次数和/或励磁电感的电流峰值。之后，在变换器1的输出电流继续下降至切换电流阈值I o4时，变换器1从HBURST模式切换至LBURST模式；对应的，在变换器1的输出电流上升至切换电流阈值I o4时，变换器1从LBURST模式切换至HBURST模式。
此外，当I o4和I o3之间的大小关系，为除I o3＞I o4之外的其他大小关系时，在不对称变换器1处于HBURST模式后，变换器1基于输出电流I o处于HBURST模式或者LBURST模式的具体实现方式请参见本实施例中I o3＞I o4时的对应描述，此处不再赘述。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载同时调整一个高频间歇周期内的开关管的导通次数N SW和/或励磁电感L m的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，控制变换器1处于HBURST模式，并在变换器1处于HBURST模式后，根据高频间歇周期T HBURST的频率f HBURST控制变换器1处于HBURST模式或者LBURST模式的具体实现方式可以是以下两个可选实施例的组合：
在一可选实施例中，中压区间M对应的工作参数包括一个高频间歇周期T HBURST内开关管的第一导通次数N2，和/或，励磁电感L m的第一电流峰值I Lm_R2；
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N2，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。并在一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数均为第一导通次数N2，和/或，励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2后，若变换器1的输出电流I o小于或者等于第一切换电流阈值I o2且大于第二切换电流阈值I o3时，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第一导通次数N2，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2；若变换器1的输出电流I o小于或者等于第二切换电流阈值I o3时，则控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第二导通次数N6，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6。
在另一可选实施例中，中压区间M对应的工作参数包括一个高频间歇周期T HBURST内开关管的第三导通次数N3＝N2或N6，和/或，励磁电感L m的第三电流峰值I Lm_R3＝I Lm_R2或I Lm_R6；
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第三导通次数N3，和/或，控制 一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3。并在一个高频间歇周期T HBURST内主开关管S1和辅开关管S2的导通次数均为第三导通次数N3，和/或，励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3后，若开关管的导通次数为第三导通次数N3和/或励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3的高频间歇周期T HBURST的频率f HBURST位于预设频率范围内，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第四导通次数N4，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4；并在经过一个高频间歇周期T HBURST内的开关管的导通次数为第四导通次数N4，和/或，一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第五导通次数N5，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5；若开关管的导通次数为第三导通次数N3和/或励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3的高频间歇周期T HBURST的频率f HBURST位于预设频率范围外，则PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数均为第三导通次数N3，和/或，控制一个高频间歇周期T HBURST的励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3。
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图4所示的三个电压区间中，确定出变换器1的输出电压V o所在的第一电压区间为中压区间M。进而，曲线控制单元122确定出中压区间M对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第一导通次数N2和/或励磁电感L m的第一电流峰值I Lm_R2，并将该工作参数发送至PWM控制单元121。
为了便于介绍，以下以中压区间M对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第一导通次数N2和励磁电感L m的第一电流峰值I Lm_R2为例进行介绍。
具体的，PWM控制单元121在接收到中压区间M对应的工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2(如2)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2，以使变换器1处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2后，PWM控制单元121计算得到开关管的导通次数N SW为第一导通次数N2且励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，并在经过一个高频间歇周期内的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4且开关管的导通次数N SW为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关 管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。
假设开关管的导通次数N SW为第一导通次数N2且励磁电感L m的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2的高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内，则PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第一导通次数N2，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第一电流峰值I Lm_R2。并在变换器1的当前输出电流I o位于第五电流区间(0,I o3]的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW为第二导通次数N6(如1)，并控制主开关管S1的导通时长，以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6，变换器1仍处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6后，PWM控制单元121计算得到开关管的导通次数N SW为第二导通次数N6且励磁电感L m的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121变换器1处于LBURST模式。这里，PWM控制单元121控制变换器1处于LBURST模式的具体实现方式请参见上述实施例中对应部分的描述，此处不再赘述。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第二导通次数N6，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第二电流峰值I Lm_R6。
这里，当中压区间M对应的工作参数为第一导通次数N2或第一电流峰值I Lm_R2时，变换器1的工作原理均可参照本实施例的描述，此处不再赘述。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载同时调整一个高频间歇周期内的开关管的导通次数N SW和/或励磁电感L m的电流峰值I Lm(PEAK),以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
在又一可选实施例中，请再参见图5，在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图4所示的三个电压区间中，确定出变换器1的输出电压V o所在的第一电压区间为低压区间L。
首先需要说明的是，在第一电压区间为低压区间L的情况下，第一切换电流阈值和第二切换电流阈值分别为I o3和I o4，第三导通次数、第四导通次数和第五导通次数分别为N3、N4和N5，第三电流峰值、第四电流峰值和第五电流峰值分别为I Lm_R3、I Lm_R4和I Lm_R5。其中，I o3＞I o4＞0。N3≥N4，N5＝0，N3和N4均为正整数。I Lm_R3≥I Lm_R4＞0，I Lm_R5＝0，I Lm_R3和I Lm_R4的取值满足变换器1的开关频率f SW小于开关频率最大值f SW(MAX)以及高频间歇周期 T HBURST的频率f HBURST处于人耳听觉范围外的条件即可。
进而，曲线控制单元122确定出低压区间L对应的工作参数为图5所示的一个高频间歇周期T HBURST内的开关管的第三导通次数N3和/或励磁电感L m的第三电流峰值I Lm_R3，并将该工作参数发送至PWM控制单元121。
为了便于介绍，以下以低压区间L对应的工作参数为一个高频间歇周期T HBURST内的开关管的第三导通次数N3(即图5所示的N6)和励磁电感L m的第三电流峰值I Lm_R3(即图5所示的I Lm_R6)为例进行介绍。
具体的，PWM控制单元121在接收到低压区间L对应的工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3，并控制励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3。
这里，当低压区间L对应的工作参数为第三导通次数N3或第三电流峰值I Lm_R3时，变换器1的工作原理均可参照本实施例的描述，此处不再赘述。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，控制变换器1处于HBURST模式，并在变换器1处于HBURST模式后，根据当前输出电流I o控制变换器1处于HBURST模式或者LBURST模式：
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图4所示的三个电压区间中，确定出变换器1的输出电压V o所在的第一电压区间为低压区间L。进而，曲线控制单元122确定出低压区间L对应的工作参数为一个高频间歇周期T HBURST内的开关管的第三导通次数N3(即图5所示的N6)和/或励磁电感L m的第三电流峰值I Lm_R3(即图5所示的I Lm_R6)，并将该工作参数发送至PWM控制单元121。
为了便于介绍，以下以低压区间L对应的工作参数为一个高频间歇周期T HBURST内的开关管的第三导通次数N3和励磁电感L m的第三电流峰值I Lm_R3为例进行介绍。
具体的，PWM控制单元121在接收到低压区间L对应的工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，以使变换器1从CRM模式切换至HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3，以及励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3后，PWM控制单元121比较变换器1的当前输出电流I o与第二切换电流阈值I o4之间的大小。在当前输出电流I o小于或者等于第一切换电流阈值I o3且大于第二切换电流阈值I o4的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，变换器1仍处于HBURST模式。在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o4的情况下，PWM控制单元121执行当前输出电流I o位于第四电流区间(0,I o4]时的上述步骤，即控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期T HBURST内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4(如I Lm_R4＝I Lm_R3)，并在经过一个高频间歇周期T HBURST内的开关管的导通次数 N SW为第四导通次数N4且励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在变换器1的当前输出电流I o小于或者等于第二切换电流阈值I o4的情况下，变换器1处于LBURST模式。其中，第一工作周期次数为正整数，示例性的，第一工作周期次数为3。
这里，当低压区间L对应的工作参数为第三导通次数N3或第三电流峰值I Lm_R3时，变换器1的工作原理均可参照本实施例的描述，此处不再赘述。
需要说明的是，在变换器1从CRM模式切换至HBURST模式后，上述实施例均是基于当前输出电流I o所在的电流区间，控制变换器1处于HBURST模式或者LBURST模式。下面结合变换器1的输出电流的变化趋势进行示例介绍。在变换器1从CRM模式切换至HBURST模式后，在变换器1的输出电流继续下降至切换电流阈值I o4时，变换器1从HBURST模式切换至LBURST模式；对应的，在变换器1的输出电流上升至切换电流阈值I o4时，变换器1从LBURST模式切换至HBURST模式。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载同时调整一个高频间歇周期内的开关管的导通次数N SW和/或励磁电感L m的电流峰值I Lm(PEAK)以使变换器1始终处于HBURST模式的实施例而言，本实施例中对极轻载情况下变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，由于极轻载情况下，变换器1处于LBURST模式，使得输出能量得到进一步减少，因此，本实施例不仅可以降低轻载情况下变换器1的输出电压纹波，还可进一步降低极轻载情况下变换器1的输出电压纹波，适用性更强。
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，控制变换器1处于HBURST模式，并在变换器1处于HBURST模式后，根据高频间歇周期T HBURST的频率f HBURST控制变换器1处于HBURST模式或者LBURST模式：
在当前开关频率f SW达到频率阈值f SW(MAX)的情况下，曲线控制单元122从图4所示的三个电压区间中，确定出变换器1的输出电压V o所在的第一电压区间为低压区间L。进而，曲线控制单元122确定出低压区间L对应的工作参数为一个高频间歇周期T HBURST内的开关管的第三导通次数N3(即图5所示的N6)和/或励磁电感L m的第三电流峰值I Lm_R3(即图5所示的I Lm_R6)，并将该工作参数发送至PWM控制单元121。
为了便于介绍，以下以低压区间L对应的工作参数为一个高频间歇周期T HBURST内的开关管的第三导通次数N3和励磁电感L m的第三电流峰值I Lm_R3为例进行介绍。
具体的，PWM控制单元121在接收到低压区间L对应的工作参数后，控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3，以使变换器1处于HBURST模式。并在开关管在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3，且励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3后，PWM控制单元121计算得到开关管的导通次数N SW为第 三导通次数N3且励磁电感L m的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3的高频间歇周期T HBURST的频率f HBURST＝1/T HBURST，并判断高频间歇周期T HBURST的频率f HBURST是否位于人耳听觉范围内。在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第四导通次数N4(如1)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4，并在经过一个高频间歇周期内的励磁电感L m的电流峰值I Lm(PEAK)为第四电流峰值I Lm_R4且开关管的导通次数N SW为第四导通次数N4的第一工作周期次数后，PWM控制单元121控制主开关管S1和辅开关管S2在一个高频间歇周期的导通次数N SW均为第五导通次数N5(即0)，并控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第五电流峰值I Lm_R5(即0)，也即PWM控制单元121控制主开关管S1和辅开关管S2一直处于关断状态。换句话说，在高频间歇周期T HBURST的频率f HBURST位于人耳听觉范围内的情况下，变换器1处于LBURST模式。在高频间歇周期T HBURST的频率f HBURST不位于人耳听觉范围内的情况下，PWM控制单元121继续控制主开关管S1和辅开关管S2在一个高频间歇周期T HBURST的导通次数N SW为第三导通次数N3，并继续控制主开关管S1的导通时长以使励磁电感L m在一个高频间歇周期内的电流峰值I Lm(PEAK)为第三电流峰值I Lm_R3。
这里，当中压区间M对应的工作参数为第三导通次数N3或第三电流峰值I Lm_R3时，变换器1的工作原理均可参照本实施例的描述，此处不再赘述。
可以理解的，在当前开关频率f SW达到频率阈值f SW(MAX)时，控制变换器1从CRM模式切换至HBURST模式，可有效降低变换器1的开关频率f SW，从而降低开关损耗，进而提高变换器1的效率。此外，在变换器1切换至HBURST模式后，相比基于负载同时调整一个高频间歇周期内的开关管的导通次数N SW和/或励磁电感L m的电流峰值I Lm(PEAK),以使变换器1始终处于HBURST模式的实施例而言，本实施例中对高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时变换器1的工作模式进行了进一步优化，使变换器1处于LBURST模式，从而可进一步降低能源损耗和开关管损耗，进而可进一步提高变换器1的效率。再者，在高频间歇周期T HBURST的频率f HBURST处于人耳听觉范围内时，变换器1处于LBURST模式，可有效降低变换器1的开关噪声。
在本实施方式中，在当前开关频率f SW达到频率阈值f SW(MAX)时，变换器1可以根据不同输出电压调整变换器1的HBURST模式进入点，从而降低原副边绕组损耗与开关管导通损耗，进而可优化变换器1在全范围输出电压下的效率。此外，变换器1还可以在处于HBURST模式时，根据负载变化调整一个高频间歇周期内开关管的导通次数和/或励磁电感的电流峰值，可降低极轻载情况下输出电压的纹波。
参见图8a，图8a是本申请提供的变换器的另一结构示意图。如图8a所示，变换器1包括主开关管S1、辅开关管S2、变压器11、控制器12和电压采样电路13。其中，变压器11包括原边绕组N P、副边绕组N S、辅助绕组N A、铁芯T 1、铁芯T 2、励磁电感L m、谐振电感L r和谐振电容C r，原边绕组N P和副边绕组N S均耦合至铁芯T 1上，辅助绕组N A和副边绕组N S均耦合至铁芯T 2上。电压采样电路13包括采样电阻R 3和R 4，采样电阻R 3的一端连接辅助绕组N A的同名端，采样电阻R 3的另一端通过采样电阻R 4连接辅助绕组N A的异名端，采样电阻R 3和R 4之间的连接点连接控制器12。这里，变压器11内部的具体连接方式以及变换器1中其他部分的具体连接方式请参见图3a所示实施例中对应部分的描述，此处不再赘述。
具体的，控制器12可以为图8b的控制器12。如图8b所示，控制器12包括输入端VBULK、输入端FB、输入端AUX、输出端MDRV、输出端SDRV、PWM控制单元121和曲线控制单元122。其中，输入端AUX连接采样电阻R 3和R 4之间的连接点。这里，控制器12中其他部分与变换器1中各部分之间的具体连接方式请参见图3b所示实施例中对应部分的描述，此处不再赘述。
在变换器1开始工作后，电压采样电路13开始实时采集采样电阻R 4的电压V R4，并将采样电阻R 4的电压V R4输出至控制器12的输入端AUX。其中，采样电阻R 4的电压V R4可以表征辅助绕组N A的电压。控制器12中的曲线控制单元122基于采样电阻R 4的电压V R4计算得到辅助绕组N A的电压V NA＝V R4*(R 3+R 4)/R 4，进而计算得到变换器1的当前输出电压V o＝V NA*P 2，其中，P 2为副边绕组N S与辅助绕组N A之间的匝数比。之后，曲线控制单元122并基于当前输出电压V o和当前输出电流I o，或者基于当前输出电压V o和当前开关频率f SW，控制变换器1在第一工作模式与第二工作模式之间切换。
本实施例中，除了变换器1的当前输出电压V o的获取方式与图3b所示实施例不同之外，变换器1的工作原理中其他部分的描述均与图3b所示实施例中对应部分的描述一致。
在本申请中，变换器1可基于输出电压调整模式切换点或者HBURST模式进入点的方式，优化电源适配器在全范围输出电压下的效率，灵活性高。
需要说明的是，本申请中的电流区间的划分(包括区间的端点值设定以及区间个数设定)可以根据实际应用场景进行调整，本申请对此不做限制。
参见图9，图9是本申请提供的不同输出电压下变换器的效率示意图。如图9所示，本申请选取输入电压为400V，输出电压为5-20V的变换器1分别在输出电压为20V、12V和5V的效率进行示例说明。具体来讲，在输出电压为20V的情况下，本申请提供的变换器1的效率曲线(即图9中的输出电压和输出电流分别为20V,7.5A的可变曲线)，对比针对不同输出电压均采用相同模式切入点的变换器的效率曲线(即图9中的输出电压和输出电流分别为20V，7.5A的固定曲线)而言，在负载达到25％时，本申请提供的变换器1的效率与采用相同模式切换点的变换器的效率相同，随着负载的增加，本申请提供的变换器1的效率明显高于采用相同模式切换点的变换器的效率。在输出电压为12V的情况下，本申请提供的变换器1的效率曲线(即图9中的输出电压和输出电流分别为12V,3A的可变曲线)，对比针对不同输出电压均采用相同模式切入点的变换器的效率曲线(即图9中的输出电压和输出电流分别为12V，3A的固定曲线)而言，负载在25％至100％之间时，本申请提供的变换器1的效率始终明显高于采用相同模式切换点的变换器的效率。在输出电压为5V的情况下，本申请提供的变换器1的效率曲线(即图9中的输出电压和输出电流分别为5V,3A的可变曲线)，对比针对不同输出电压均采用相同模式切入点的变换器的效率曲线(即图9中的输出电压和输出电流分别为5V，3A的固定曲线)而言，负载在25％至100％之间时，本申请提供的变换器1的效率始终明显高于采用相同模式切换点的变换器的效率，且本申请提供的变换器1的效率可以达到88.6％以上，甚至高达91.7％。由此可见，本申请提供的变换器1的输出电压不论在高压、中压和低压的情况下，均可显著提高变换器1的效率，且在输出电压为低压时的变换器1的效率优化效果最显著。
参见图10，图10是本申请提供的变换器的控制方法的一流程示意图。本申请实施例提供的变换器的控制方法适用于图3a至图8b所示的变换器1中的控制器12。变换器 的控制方法可包括步骤：
S101，获得变换器的输出电压，并基于变换器的输出电压得到模式切换参数。
在一可选实施方式中，模式切换参数为第一电流阈值。
在另一可选实施方式中，模式切换参数为变换器处于第二工作模式下的第一工作参数。
变换器中的控制器获得变换器的输出电压和开关频率，并在开关频率达到频率阈值时，根据输出电压得到第一工作参数。其中，第一工作参数包括主开关管和辅开关管在变换器的一个工作周期的导通次数，或者励磁电感在一个工作周期的电流峰值。
S102，根据模式切换参数控制变换器在第一工作模式与第二工作模式之间切换。
其中，第一工作模式下变换器的开关频率的大小与变换器的输出电流的大小负相关，第二工作模式下在变换器的一个工作周期内变换器的开关频率不变。
在一可选实施方式中，变换器中的控制器比较变换器的输出电流与第一切换电流阈值的大小，并根据比较结果控制变换器在第一工作模式与第二工作模式之间切换。
在另一可选实施方式中，变换器中的控制器基于第一工作参数控制变换器从第一工作模式切换至第二工作模式。
具体实现中，本申请提供的变换器的控制方法中控制器所执行的更多操作可参见图3a至图8b所示的变换器1中控制器12所执行的实现方式，在此不再赘述。
在本申请实施例中，变换器可以基于输出电压调整变换器1的模式切换点的方式，或者基于输出电压调整变换器从第一工作模式切换至第二工作模式下的工作参数的方式，优化变换器在全范围输出电压下的效率，灵活性高。
参见图11，图11是本申请提供的变换器的一结构示意图。如图11所示，终端设备包括变换器1和电池2。其中，变换器1与电池2相连，用于向电池2充电。本申请提供的终端设备可以为智能手机、平板电脑、智能音箱以及可穿戴设备等。
在一可选实施方式中，在终端设备电量不足的情况下，终端设备中的变换器1将外部直流电源输入的第一直流电压进行直流变换后得到第二直流电压，并向电池2输出第二直流电压，从而实现对电池2的供电。与此同时，变换器1在向电池2进行充电的过程中，变换器1获取自身的当前输出电压，并基于该当前输出电压得到模式切换参数。变换器1根据模式切换参数控制变换器1在第一工作模式与第二工作模式之间切换，其中，第一工作模式下变换器1的开关频率的大小与变换器1的输出电流的大小负相关，第二工作模式下在变换器1的一个工作周期内变换器的开关频率不变。
具体实现中，本申请提供的终端设备中变换器1所执行的更多操作可参见图3a至图8b所示的变换器1所执行的实现方式，在此不再赘述。
在本申请实施例中，变换器1可以基于输出电压调整变换器1的模式切换点的方式，或者基于输出电压调整变换器1从第一工作模式切换至第二工作模式下的工作参数的方式，优化变换器1在全范围输出电压下的效率，从而优化终端设备的工作效率，灵活性高。
以上，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (25)

  1. 一种变换器，其特征在于，所述变换器包括主开关管、辅开关管、变压器和控制器，其中：
    所述主开关管和所述辅开关管串联在所述变换器的输入端和参考地之间，所述变压器的输入端分别连接至所述辅开关管的两端，所述变压器的输出端连接所述变换器的输出端；
    所述控制器用于获得所述变换器的输出电压，并基于所述变换器的输出电压得到模式切换参数；根据所述模式切换参数控制所述变换器在第一工作模式与第二工作模式之间切换，其中，所述第一工作模式下所述变换器的开关频率的大小与所述变换器的输出电流的大小负相关，所述第二工作模式下在所述变换器的一个工作周期内所述变换器的开关频率不变。
  2. 根据权利要求1所述的变换器，其特征在于，所述模式切换参数为第一电流阈值；
    所述控制器用于比较所述变换器的输出电流与所述第一切换电流阈值的大小，并根据比较结果控制所述变换器在所述第一工作模式与所述第二工作模式之间切换。
  3. 根据权利要求2所述的变换器，其特征在于，所述控制器用于基于所述输出电压，从多个电压区间中得到所述输出电压所在的第一电压区间；从所述电压区间对应的多个切换电流阈值中得到所述第一电压区间对应的所述第一切换电流阈值，其中，所述多个电压区间与所述多个切换电流阈值一一对应。
  4. 根据权利要求2或3所述的变换器，其特征在于，所述控制器用于在所述输出电流小于或者等于所述第一切换电流阈值且大于第二切换电流阈值时，控制所述主开关管和所述辅开关管在所述变换器的一个工作周期的导通次数均为第一导通次数；
    所述控制器还用于在所述输出电流小于或者等于所述第二切换电流阈值时，控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为第二导通次数，其中，所述第二导通次数小于所述第一导通次数。
  5. 根据权利要求2或3所述的变换器，其特征在于，所述变压器包括励磁电感；
    所述控制器用于在所述输出电流小于或者等于所述第一切换电流阈值且大于第二切换电流阈值时，控制所述励磁电感在所述变换器的一个工作周期的电流峰值为第一电流峰值；
    所述控制器还用于在所述输出电流小于或者等于所述第二切换电流阈值时，控制所述励磁电感在所述一个工作周期的电流峰值为第二电流峰值，其中，所述第二电流峰值小于所述第一电流峰值。
  6. 根据权利要求2或3所述的变换器，其特征在于，所述控制器用于在所述输出电流小于或者等于所述第一切换电流阈值且大于第三切换电流阈值时，控制所述主开关管和所述辅开关管在所述变换器的一个工作周期的导通次数均为第三导通次数；
    所述控制器还用于在所述输出电流小于或者等于所述第三切换电流阈值时，控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为第四导通次数；并在经过所述一个工作周期内的导通次数为所述第三导通次数的第一工作周期次数后，控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为第五导通次数，其中，所述第四导通次数小于或者等于所述第三导通次数且大于所述第五导通次数。
  7. 根据权利要求2或3所述的变换器，其特征在于，所述变压器包括励磁电感；
    所述控制器用于在所述输出电流小于或者等于所述第一切换电流阈值且大于第三切换电流阈值时，控制所述励磁电感在所述变换器的一个工作周期的电流峰值为第三电流峰值；
    所述控制器还用于在所述输出电流小于或者等于所述第三切换电流阈值时，控制所述励磁电感在所述一个工作周期的电流峰值为第四电流峰值；并在经过所述一个工作周期内的电流峰值为所述第三电流峰值的第一工作周期次数后，控制所述励磁电感在所述一个工作周期的电流峰值为第五电流峰值，其中，所述第四电流峰值小于或者等于所述第三电流峰值且大于所述第五电流峰值。
  8. 根据权利要求2或3所述的变换器，其特征在于，所述控制器用于在所述输出电流小于或者等于所述第一切换电流阈值时，控制所述主开关管和所述辅开关管在所述变换器的一个工作周期的导通次数均为第三导通次数；
    所述控制器还用于在所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为所述第三导通次数后，若所述变换器的工作频率位于预设频率范围内，则控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为第四导通次数；并在经过所述一个工作周期内的导通次数为所述第四导通次数的第一工作周期次数后，控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为第五导通次数，其中，所述第四导通次数小于或者等于所述第三导通次数且大于所述第五导通次数；
    所述控制器还用于在所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为所述第三导通次数后，若所述变换器的工作频率位于所述预设频率范围外，则控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为所述第三导通次数。
  9. 根据权利要求2或3所述的变换器，其特征在于，所述变压器包括励磁电感；
    所述控制器用于在所述输出电流小于或者等于所述第一切换电流阈值时，控制所述励磁电感在所述变换器的一个工作周期的电流峰值为第三电流峰值；
    所述控制器还用于在所述励磁电感在所述一个工作周期的电流峰值为所述第三电流峰值后，若所述变换器的工作频率位于预设频率范围内，则控制所述励磁电感在所述一个工作周期的电流峰值为第四电流峰值；并在经过所述一个工作周期内的电流峰值为所述第四电流峰值的第一工作周期次数后，控制所述励磁电感在所述一个工作周期的电流峰值为第五电流峰值，其中，所述第四电流峰值大于所述第五电流峰值且小于或者等于所述第三电流峰值；
    所述控制器还用于在所述励磁电感在所述一个工作周期的电流峰值为所述第三电流峰值后，若所述变换器的工作频率位于所述预设频率范围外，则控制所述励磁电感在所述一个工作周期的电流峰值为所述第三电流峰值。
  10. 根据权利要求1所述的变换器，其特征在于，所述模式切换参数为所述变换器处于所述第二工作模式下的第一工作参数；
    所述控制器还用于获得所述变换器的开关频率；
    所述控制器用于在所述开关频率达到频率阈值时，根据所述输出电压得到所述第一工作参数；基于所述第一工作参数控制所述变换器从第一工作模式切换至所述第二工作模式，其中，所述第一工作参数包括所述主开关管和所述辅开关管在所述变换器的一个工作周期的导 通次数，或者所述励磁电感在所述一个工作周期的电流峰值。
  11. 根据权利要求10所述的变换器，其特征在于，所述控制器用于在所述开关频率达到所述频率阈值时，从多个电压区间中得到所述输出电压所在的第一电压区间；从所述多个电压区间对应的多个工作参数中得到所述第一电压区间对应的所述第一工作参数，其中，所述多个电压区间与多个工作参数一一对应。
  12. 根据权利要求11所述的变换器，其特征在于，所述多个电压区间还包括第二电压区间，在所述第二电压区间中的任意值均小于所述第一电压区间中的任意值时，所述第二电压区间对应的第二工作参数小于所述第一工作参数。
  13. 根据权利要求10-12任一项所述的变换器，其特征在于，所述第一工作参数包括所述导通次数，所述导通次数为第一导通次数；
    所述控制器用于控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数为所述第一导通次数；
    所述控制器还用于在所述主开关管和所述辅开关管在所述一个工作周期的导通次数为所述第一导通次数后，若所述变换器的输出电流小于或者等于第二切换电流阈值，则控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为第二导通次数，其中，所述第二导通次数小于所述第一导通次数；
    所述控制器还用于在所述主开关管和所述辅开关管在所述一个工作周期的导通次数为所述第一导通次数后，若所述变换器的输出电流大于所述第二切换电流阈值且小于或者等于第一切换电流阈值，则控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为所述第一导通次数。
  14. 根据权利要求10-12任一项所述的变换器，其特征在于，所述第一切换参数包括所述电流峰值，所述电流峰值为第一电流峰值；
    所述控制器用于控制所述励磁电感在所述一个工作周期的电流峰值为所述第一电流峰值；
    所述控制器还用于在所述励磁电感在所述一个工作周期的电流峰值为所述第一电流峰值后，若所述变换器的输出电流小于或者等于第二切换电流阈值，则控制所述励磁电感在所述一个工作周期的电流峰值为第二电流峰值，其中，所述第二电流峰值小于所述第一电流峰值；
    所述控制器还用于在所述励磁电感在所述一个工作周期的电流峰值为所述第一电流峰值后，若所述变换器的输出电流大于所述第二切换电流阈值且小于或者等于第一切换电流阈值，则控制所述励磁电感在所述一个工作周期的电流峰值为所述第一电流峰值。
  15. 一种变换器的控制方法，其特征在于，所述变换器包括主开关管、辅开关管和变压器，其中，所述主开关管和所述辅开关管串联在所述变换器的输入端和参考地之间，所述变压器的输入端分别连接至所述辅开关管的两端，所述变压器的输出端连接所述变换器的输出端；
    所述方法包括：
    获得所述变换器的输出电压，并基于所述变换器的输出电压得到模式切换参数；
    根据所述模式切换参数控制所述变换器在第一工作模式与第二工作模式之间切换，其中，所述第一工作模式下所述变换器的开关频率的大小与所述变换器的输出电流的大小负相关，所述第二工作模式下在所述变换器的一个工作周期内所述变换器的开关频率不变。
  16. 根据权利要求15所述的方法，其特征在于，所述模式切换参数为第一切换电流阈值；
    所述根据所述模式切换参数控制所述变换器在第一工作模式与第二工作模式之间切换，包括：
    比较所述变换器的输出电流与所述第一切换电流阈值的大小，并根据比较结果控制所述变换器在所述第一工作模式与所述第二工作模式之间切换。
  17. 根据权利要求16所述的方法，其特征在于，所述基于所述变换器的输出电压得到模式切换参数，包括：
    基于所述输出电压，从多个电压区间中得到所述输出电压所在的第一电压区间；
    从所述电压区间对应的多个切换电流阈值中得到所述第一电压区间对应的所述第一切换电流阈值，其中，所述多个电压区间与所述多个切换电流阈值一一对应。
  18. 根据权利要求16或17所述的方法，其特征在于，所述根据比较结果控制所述变换器在所述第一工作模式与所述第二工作模式之间切换，包括：
    在所述输出电流小于或者等于所述第一切换电流阈值且大于第二切换电流阈值时，控制所述主开关管和所述辅开关管在所述变换器的一个工作周期的导通次数均为第一导通次数；
    所述方法还包括：
    在所述输出电流小于或者等于所述第二切换电流阈值时，控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为第二导通次数，其中，所述第二导通次数小于所述第一导通次数。
  19. 根据权利要求16或17所述的方法，其特征在于，所述变压器包括励磁电感；
    所述根据比较结果控制所述变换器在所述第一工作模式与所述第二工作模式之间切换，包括：
    在所述输出电流小于或者等于所述第一切换电流阈值且大于第二切换电流阈值时，控制所述励磁电感在所述变换器的一个工作周期的电流峰值为第一电流峰值；
    所述方法还包括：
    在所述输出电流小于或者等于所述第二切换电流阈值时，控制所述励磁电感在所述一个工作周期的电流峰值为第二电流峰值，其中，所述第二电流峰值小于所述第一电流峰值。
  20. 根据权利要求15所述的方法，其特征在于，所述模式切换参数为所述变换器处于第二工作模式下的第一工作参数；所述方法还包括：
    获得所述变换器的开关频率；
    所述基于所述变换器的输出电压得到模式切换参数，包括：
    在所述开关频率达到频率阈值时，根据所述输出电压得到所述第一工作参数；
    所述根据所述模式切换参数控制所述变换器在第一工作模式与第二工作模式之间切换，包括：
    基于所述第一工作参数控制所述变换器从所述第一工作模式切换至所述第二工作模式，其中，所述第一工作参数包括所述主开关管和所述辅开关管在所述变换器的一个工作周期的导通次数，或者所述励磁电感在所述一个工作周期的电流峰值。
  21. 根据权利要求20所述的方法，其特征在于，所述在所述开关频率达到频率阈值时，根据所述输出电压得到所述第一工作参数，包括：
    在所述开关频率达到所述频率阈值时，从多个电压区间中得到所述输出电压所在的第一电压区间；
    从所述多个电压区间对应的多个工作参数中得到所述第一电压区间对应的所述第一工作参数，其中，所述多个电压区间与多个工作参数一一对应。
  22. 根据权利要求21所述的方法，其特征在于，所述多个电压区间还包括第二电压区间，在所述第二电压区间中的任意值均小于所述第一电压区间中的任意值时，所述第二电压区间对应的第二工作参数小于所述第一工作参数。
  23. 根据权利要求20-22任一项所述的方法，其特征在于，所述第一工作参数包括所述导通次数，所述导通次数为第一导通次数；
    所述基于所述第一工作参数控制所述变换器从所述第一工作模式切换至所述第二工作模式，包括：
    控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数为所述第一导通次数；
    所述方法还包括：
    在所述主开关管和所述辅开关管在所述一个工作周期的导通次数为所述第一导通次数后，若所述变换器的输出电流小于或者等于第二切换电流阈值，则控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为第二导通次数，其中，所述第二导通次数小于所述第一导通次数；
    所述方法还包括：
    在所述主开关管和所述辅开关管在所述一个工作周期的导通次数为所述第一导通次数后，若所述变换器的输出电流大于所述第二切换电流阈值且小于或者等于第一切换电流阈值，则控制所述主开关管和所述辅开关管在所述一个工作周期的导通次数均为所述第一导通次数。
  24. 根据权利要求20-22任一项所述的方法，其特征在于，所述第一工作参数包括所述电流峰值，所述电流峰值为第一电流峰值；
    所述基于所述第一工作参数控制所述变换器从所述第一工作模式切换至所述第二工作模式，包括：
    控制所述励磁电感在所述一个工作周期的电流峰值为所述第一电流峰值；
    所述方法还包括：
    在所述励磁电感在所述一个工作周期的电流峰值为所述第一电流峰值后，若所述变换器的输出电流小于或者等于第二切换电流阈值，则控制所述励磁电感在所述一个工作周期的电流峰值为第二电流峰值，其中，所述第二电流峰值小于所述第一电流峰值；
    所述方法还包括：
    在所述励磁电感在所述一个工作周期的电流峰值为所述第一电流峰值后，若所述变换器的输出电流大于所述第二切换电流阈值且小于或者等于第一切换电流阈值，则控制所述励磁电感在所述一个工作周期的电流峰值为所述第一电流峰值。
  25. 一种终端设备，其特征在于，所述终端设备包括电池和如权利要求1-14任一项所述的变换器，其中，所述变换器用于向所述电池充电。
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002354820A (ja) * 2001-05-28 2002-12-06 Toshiba Tec Corp 電力変換装置
CN106558976A (zh) * 2016-10-26 2017-04-05 广州金升阳科技有限公司 驱动控制方法及驱动控制电路
CN111130353A (zh) * 2019-12-25 2020-05-08 广州金升阳科技有限公司 开关电源装置
CN112564489A (zh) * 2020-11-03 2021-03-26 广州金升阳科技有限公司 一种开关变换器的模式控制方法及开关变换器
CN114865922A (zh) * 2022-05-26 2022-08-05 中国电子科技集团公司第五十八研究所 一种控制方式平滑切换的有源箝位反激变换器

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002354820A (ja) * 2001-05-28 2002-12-06 Toshiba Tec Corp 電力変換装置
CN106558976A (zh) * 2016-10-26 2017-04-05 广州金升阳科技有限公司 驱动控制方法及驱动控制电路
CN111130353A (zh) * 2019-12-25 2020-05-08 广州金升阳科技有限公司 开关电源装置
CN112564489A (zh) * 2020-11-03 2021-03-26 广州金升阳科技有限公司 一种开关变换器的模式控制方法及开关变换器
CN114865922A (zh) * 2022-05-26 2022-08-05 中国电子科技集团公司第五十八研究所 一种控制方式平滑切换的有源箝位反激变换器

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