CN111355392A - Self-adaptive synchronous rectification control system and method of LLC resonant converter - Google Patents
Self-adaptive synchronous rectification control system and method of LLC resonant converter Download PDFInfo
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- CN111355392A CN111355392A CN201811585002.6A CN201811585002A CN111355392A CN 111355392 A CN111355392 A CN 111355392A CN 201811585002 A CN201811585002 A CN 201811585002A CN 111355392 A CN111355392 A CN 111355392A
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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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
- H02M3/33569—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 having several active switching elements
- H02M3/33576—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 having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33592—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 having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention relates to a self-adaptive synchronous rectification control system and a method of an LLC resonant converter, wherein the system comprises: the input end of the sampling circuit is connected with the drain electrode of the synchronous rectifying tube and is used for collecting the drain electrode voltage of the synchronous rectifying tube; the input end of the comparator is connected with the output end of the sampling circuit and is used for comparing the input drain voltage with a preset voltage threshold value and outputting a comparison result; and the control unit is connected with the comparator and the grid electrode of the synchronous rectifying tube and is used for controlling the conduction duration of the synchronous rectifying tube in one working period. The invention can directly judge the voltage of the drain terminal of the synchronous rectifier tube so as to obtain whether the synchronous rectifier tube is in the optimal turn-off state, and accordingly, the turn-off control is carried out on the synchronous rectifier tube so as to adjust the synchronous rectifier tube to a proper turn-off point. The method adopts a self-adaptive synchronous rectification algorithm, and can realize self-adaptive control of the conduction time of the synchronous rectification tube according to the change trend of the switching frequency of the primary side switching tube.
Description
Technical Field
The invention relates to a synchronous rectification technology, in particular to a self-adaptive synchronous rectification control system and a self-adaptive synchronous rectification control method for an LLC resonant converter.
Background
LLC resonant converters, as an excellent topology, are now recognized and widely used as power supply topologies. The LLC resonant converter can realize zero voltage turn-on of the primary power tube and zero current turn-off of the secondary rectifier diode in a wide load range, so that the LLC resonant converter has the characteristics of higher working efficiency and higher switching frequency compared with a hard switching topology.
However, when the LLC resonant converter operates under a heavy load condition, because the secondary rectifier diode has conduction voltage drop, a large current flows, which results in a large energy loss after passing through the rectifier diode, and reduces the operating efficiency of the LLC resonant converter. In order to solve the problems, a synchronous rectifying tube method is provided, the characteristic that the conduction resistance of a power tube is small is utilized, and the power tube is used for replacing a diode, so that the working efficiency of the LLC resonant converter is greatly improved when the LLC resonant converter works under the condition of heavy load.
In the LLC resonant converter, the start point of the synchronous rectifier is substantially the same as the power tube corresponding to the primary side, and the early and late turn-off points of the synchronous rectifier affect the operating efficiency and characteristics of the overall system. When the turn-off of the synchronous rectifier tube is earlier than the optimal turn-off point, the current can flow through a body diode of the synchronous rectifier tube, and the loss of the synchronous rectifier tube is increased; when the synchronous rectifier tube is turned off later than the optimal turn-off point, the secondary current affects the working state of the primary resonant tank of the LLC resonant converter, and the resonant current is distorted. In the prior art, a control mode of a synchronous rectifier tube which can well solve the problems is lacked.
Disclosure of Invention
In view of the above, there is a need for a control system and method for a synchronous rectifier suitable for an LLC resonant converter.
An adaptive synchronous rectification control system of an LLC resonant converter, for turn-off control of a synchronous rectifier in a half-bridge LLC resonant converter with a synchronous rectifier, the system comprising: the input end of the sampling circuit is connected with the drain electrode of the synchronous rectifying tube and is used for collecting the drain electrode voltage of the synchronous rectifying tube; the input end of the comparator is connected with the output end of the sampling circuit and is used for comparing the input drain voltage with a preset voltage threshold value and outputting a comparison result; the control unit is connected with the comparator and the grid electrode of the synchronous rectifying tube, is used for controlling the conducting time of the synchronous rectifying tube in one working period, and is also used for setting the conducting time of the synchronous rectifying tube in the next working period to be equal to the conducting time of the current working period when the drain voltage is smaller than a preset voltage threshold; the control unit is still used for obtaining the trend of change of the switching frequency of the switch tube of the half-bridge of the former avris of half-bridge LLC resonant converter increases when being in the trend of reducing synchronous rectifier is long when switching on of next duty cycle the switching frequency of the switch tube of the half-bridge of the former avris of half-bridge LLC resonant converter reduces when being in the trend of increasing synchronous rectifier is long when switching on of next duty cycle.
In one embodiment, the synchronous rectification circuit further comprises a gate driver, an input end of the gate driver is connected with an output end of the control unit, an output end of the gate driver is connected with a gate of the synchronous rectification tube, and the control unit controls the conduction duration of the synchronous rectification tube in one working cycle through the gate driver.
In one embodiment, the synchronous rectifier further comprises a PWM timer, an input end of the PWM timer is connected to an output end of the control unit, an output end of the PWM timer is connected to a gate of the synchronous rectifier, and the control unit controls a conduction time of the synchronous rectifier in one working cycle by adjusting a duty ratio of a PWM signal output by the PWM timer.
In one embodiment, the system comprises an MCU integrated with the comparator, a control unit and a PWM timer.
In one embodiment, an inverting input terminal of the comparator is connected to the output terminal of the sampling circuit, a non-inverting input terminal of the comparator is connected to the voltage setting terminal of the control unit, and the control unit is further configured to set the preset voltage threshold.
In one embodiment, the sampling circuit has an absolute value sampling function, and the drain voltage output to the comparator is set to a positive potential.
In one embodiment, the absolute values of the increased conduction period and the decreased conduction period are equal.
An adaptive synchronous rectification control method of an LLC resonant converter, which is used for carrying out turn-off control on a synchronous rectifier in a half-bridge LLC resonant converter with the synchronous rectifier, and comprises the following steps: step A, obtaining the drain voltage of a synchronous rectifier tube when the synchronous rectifier tube is turned off; step B, if the drain voltage is smaller than a preset voltage threshold, setting the conduction time of the synchronous rectifier tube in the next working period to be equal to the conduction time of the current working period; step C, if the drain voltage is larger than or equal to the preset voltage threshold, acquiring the switching frequency variation trend of a switching tube of a half bridge on the primary side of the half bridge LLC resonant converter; step D, when the switching frequency is in a decreasing trend, increasing the conducting duration of the synchronous rectifier tube in the next working period, and returning to the step A in the next working period; and when the switching frequency is in an increasing trend, reducing the conducting time of the synchronous rectifier tube in the next working period, and returning to the step A in the next working period.
In one embodiment, if the switching frequency is kept stable, after the step B, waiting for a preset duration, and returning to the step a, where the preset duration is greater than the working period.
In one embodiment, the absolute values of the increased on-time and the decreased on-time of step D are equal.
The self-adaptive synchronous rectification control system and the self-adaptive synchronous rectification control method of the LLC resonant converter can directly judge the voltage of the drain end of the synchronous rectifying tube so as to obtain whether the synchronous rectifying tube is in the optimal turn-off state or not, and accordingly, the turn-off control is carried out on the synchronous rectifying tube so as to adjust the synchronous rectifying tube to a proper turn-off point. The method adopts a self-adaptive synchronous rectification algorithm, and can realize self-adaptive control of the conduction time of the synchronous rectification tube according to the change trend of the switching frequency of the primary side switching tube. And each period is judged at most once, so that the realization difficulty of the self-adaptive synchronous rectification system is simplified.
Drawings
For a better understanding of the description and/or illustration of embodiments and/or examples of those inventions disclosed herein, reference may be made to one or more of the drawings. The additional details or examples used to describe the figures should not be considered as limiting the scope of any of the disclosed inventions, the presently described embodiments and/or examples, and the presently understood best modes of these inventions.
FIG. 1 is a circuit topology diagram of a half-bridge LLC resonant converter with synchronous rectifiers;
FIG. 2 is a functional block diagram of an adaptive synchronous rectification control system of the LLC resonant converter in one embodiment;
FIG. 3 is a flow diagram of an adaptive synchronous rectification control method of an LLC resonant converter in one embodiment;
FIG. 4 is a waveform diagram illustrating the control of the circuit of FIG. 1 using the method of FIG. 3 when the switching frequency of the primary side switching tube is decreased;
fig. 5 is a waveform diagram illustrating the control of the circuit shown in fig. 1 using the method shown in fig. 3 when the switching frequency of the primary side switching tube increases.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Fig. 1 is a circuit topology diagram of a half-bridge LLC resonant converter with synchronous rectifiers, the circuit topology of the synchronous rectification LLC resonant converter comprising: primary winding N of transformerPSecondary side first winding N of transformerS1Secondary winding N of transformerS1(ii) a Power tubes M1 and M2 on the primary side of the transformer; the resonant tank comprises a resonant capacitor Cr, a resonant inductor Lr and an excitation inductor Lm; synchronous rectifiers M3 and M4 on the secondary side of the transformer output a capacitor CO. The diodes D1 and D2 on the primary side of the transformer are parasitic diodes of power tubes M1 and M2 respectively, and the capacitors C1 and C2 are parasitic capacitors of M1 and M2 respectively; d3 and D4 on the secondary side of the transformer are parasitic diodes of the synchronous rectifiers M3 and M4, respectively, and C3 and C4 are parasitic capacitances of the synchronous rectifiers M3 and M4, respectively. Power supply VINAn input power supply is provided for the primary side of the transformer, and the output voltage of the output end of the LLC resonant converter is VOOutput current is IOThe equivalent resistance of the load is R.
The adaptive synchronous rectification control method of the LLC resonant converter of the present application is used for controlling the turn-off of the synchronous rectifier in the half-bridge LLC resonant converter with the synchronous rectifier, and for the circuit shown in fig. 1, namely, the turn-off of the synchronous rectifiers M3 and M4, the control methods of the synchronous rectifiers M3 and M4 are the same, and the adaptive synchronous rectification control method of the LLC resonant converter in an embodiment is described below with reference to fig. 3.
When parameters such as input/output of the LLC resonant converter change, the optimal turn-off point of the synchronous rectifier tube on the secondary side of the transformer also changes. The invention is characterized in that when the optimal turn-off point of the synchronous rectifier tube changes, the turn-off time of the synchronous rectifier tube is correspondingly adjusted. Referring to fig. 3, an adaptive synchronous rectification control method for an LLC resonant converter in an embodiment includes the following steps:
s310, obtaining the drain voltage of the synchronous rectifier tube when the synchronous rectifier tube is turned off.
In one embodiment, a sampling circuit may be provided to sample the drain voltage of the synchronous rectifier. Since the on-time of the synchronous rectifier in the current working cycle is known (obtained from the previous working cycle by the adaptive synchronous rectification control method of the LLC resonant converter of the present invention), the time when the synchronous rectifier is turned off can be determined according to the on-time of the current working cycle.
And S320, if the drain voltage is smaller than the preset voltage threshold, setting the conduction time of the synchronous rectifier tube in the next working period to be equal to the conduction time of the current working period.
If the obtained drain voltage V of the synchronous rectifier tubeSRLess than a predetermined voltage threshold VHIt is stated that the synchronous rectifier tube in the working cycle is turned off at a low level when turned off, and the turn-off time of the synchronous rectifier tube in the current working cycle is the proper turn-off time, so that the turn-on time of the synchronous rectifier tube in the next working cycle is kept unchanged.
If the obtained drain voltage V of the synchronous rectifier tubeSRGreater than or equal to a predetermined voltage threshold VHIt is described that the synchronous rectifier in the duty cycle is turned off at a high level when turned off, and the turn-off of the synchronous rectifier needs to be adjusted. In this embodiment, the switching frequency variation trend of the switching tube of the half bridge on the primary side of the half bridge LLC resonant converter is obtained to determine whether the synchronous rectifier tube is turned off earlier or later than the optimal turn-off point. When the switching frequency of the switching tube is in an increasing trend, the step S330 is carried out; while when the switching frequency is in a decreasing trendThe process proceeds to step S340.
And S330, reducing the conduction time of the synchronous rectifier tube in the next working period.
In this embodiment, when the switching frequency of the switching tube is in an increasing trend, the on-time of the synchronous rectifier tube in the next working cycle is decreased by Δ t, and the process returns to step S310 to perform the above-mentioned operation once when waiting for the next working cycle. I.e. if the measured V is measured next every cycleSR>VHThe conduction time of the next duty cycle of the synchronous rectifier continues to decrease by Δ t … … until after one or more cycles of regulation, V is measuredSR<VHAnd adjusting the turn-off time of the synchronous rectifier tube to be proper.
And S340, increasing the conduction time of the synchronous rectifier tube in the next working period.
In this embodiment, when the switching frequency of the switching tube is in a decreasing trend, the on-time of the synchronous rectifier tube in the next working cycle is extended by Δ t, and the process returns to step S310 to perform the above-mentioned operation once when waiting for the next working cycle. I.e. if the measured V is measured next every cycleSR>VHThen the conduction time for the next duty cycle of the synchronous rectifier continues to be extended by Δ t … … until V is measured after one or more cycles of regulationSR<VHAnd adjusting the turn-off time of the synchronous rectifier tube to be proper.
It will be appreciated that in one embodiment, the Δ t for each decrease in step S330 and the Δ t for each extension in step S340 are equal. The specific value of Δ t can be set empirically by those skilled in the art.
The self-adaptive synchronous rectification control method of the LLC resonant converter can directly judge the voltage of the drain end of the synchronous rectifier tube so as to obtain whether the synchronous rectifier tube is in the optimal turn-off state, and accordingly, the turn-off control is carried out on the synchronous rectifier tube so as to adjust the synchronous rectifier tube to a proper turn-off point. The method adopts a self-adaptive synchronous rectification algorithm, and can realize self-adaptive control of the conduction time of the synchronous rectification tube according to the change trend of the switching frequency of the primary side switching tube. And each period is judged once, so that the realization difficulty of the self-adaptive synchronous rectification system is simplified.
After step S320, the synchronous rectifier turn-off time is appropriate, at which point the current turn-off time should be maintained if the system is in a steady state. Therefore, in an embodiment, if the switching frequency of the switching tube of the half bridge at the primary side of the LLC resonant converter is kept stable, the step S320 waits for a preset time period and returns to the step S310, and the on-time of the synchronous rectifying tube does not need to be adjusted within the preset time period, so as to save system resources. It will be appreciated that the preset duration may be significantly greater than the duty cycle of the synchronous rectifier.
The invention also provides a self-adaptive synchronous rectification control system of the LLC resonant converter, which is used for carrying out turn-off control on the synchronous rectification tube in the half-bridge LLC resonant converter with the synchronous rectification tube. Fig. 2 is a schematic block diagram of an adaptive synchronous rectification control system of an LLC resonant converter in an embodiment, and the adaptive synchronous rectification control system 100 of the LLC resonant converter (hereinafter referred to simply as the control system 100) includes a sampling circuit 10, a comparator 20, and a control unit 30.
The input end of the sampling circuit 10 is connected to the drain of the synchronous rectifier M4 for collecting the drain voltage V of the synchronous rectifier M4SR. It is understood that the synchronous rectifier M3 is also connected to a same control system 100 for control (not shown in fig. 2), and the following description will take the control system 100 connected to the synchronous rectifier M4 as an example.
The input terminal of the comparator 20 is connected to the output terminal of the sampling circuit 30, and is configured to compare the drain voltage input by the sampling circuit 30 with a preset voltage threshold, and output a comparison result.
The control unit 30 is connected to the comparator 20 and the gate of the synchronous rectifier M4 for controlling the on-time of the synchronous rectifier M4 in one working cycle and for controlling the drain voltage VSRLess than a predetermined voltage threshold VHAnd setting the conduction time length of the synchronous rectifier tube in the next working period to be equal to the conduction time length of the current working period. The control unit 30 is further configured to obtain a switching tube (e.g., power tube M1 and power tube in fig. 1) of the half bridge on the primary side of the half bridge LLC resonant converterTube M2), increasing the on-time of the synchronous rectifier tube M4 in the next operating cycle when the switching frequency is in a decreasing trend, and decreasing the on-time of the synchronous rectifier tube M4 in the next operating cycle when the switching frequency is in an increasing trend.
The self-adaptive synchronous rectification control system of the LLC resonant converter can directly judge the voltage of the drain end of the synchronous rectifier tube, so as to judge whether the synchronous rectifier tube is in the optimal turn-off state or not, and accordingly, the turn-off control is carried out on the synchronous rectifier tube and the synchronous rectifier tube is adjusted to a proper turn-off point. The method adopts a self-adaptive synchronous rectification algorithm, and can realize self-adaptive control of the conduction time of the synchronous rectification tube according to the change trend of the switching frequency of the primary side switching tube. And each period is judged once, so that the realization difficulty of the self-adaptive synchronous rectification system is simplified.
In one embodiment, the control system 100 further includes a gate driver 50. The input terminal of the gate driver 50 is connected to the output terminal of the control unit 30, and the output terminal of the gate driver 50 is connected to the gate of the synchronous rectifier M4. The control unit 30 controls the on-time of the synchronous rectifier M4 in one duty cycle through the gate driver 50.
In one embodiment, the control system 100 may be implemented by using an MCU (micro controller Unit). In one embodiment, the MCU may be integrated with the control unit 30 and the comparator 20. The MCU is utilized to realize digital control, the circuit structure is simple, an external complex circuit is not needed, and the parasitic effect caused by the parasitic parameters of the loop is reduced.
In the embodiment shown in fig. 2, the adaptive synchronous rectification control system 100 of the LLC resonant converter further includes a PWM timer 40. The input end of the PWM timer 40 is connected to the output end of the control unit 30, the output end of the PWM timer 40 is connected to the gate driver 50, and the control unit 30 controls the conducting time duration of the synchronous rectifier M4 in one working cycle by adjusting the duty ratio of the PWM signal output by the PWM timer. In other embodiments, the control system 100 may also include the PWM timer 40 but not provide the gate driver 50.
In one embodiment, the MCU of the control system 100 may also be integrated with the PWM timer 40.
In the embodiment shown in fig. 2, the inverting input terminal of the comparator 20 is connected to the output terminal of the sampling circuit 10, and the non-inverting input terminal of the comparator 20 is connected to the voltage setting terminal of the control unit 30. The control unit 30 is also arranged to set a preset voltage threshold V supplied to the non-inverting input of the comparator 20H。
In one embodiment, the current I is output at the LLC converterOAccording to the frequency f of the primary switching tube when changingSWDetermines the adjustment direction of the conduction time of the secondary synchronous rectifier tube M4. When primary side switching frequency fSWWhen the current is increased, the conduction time of the secondary synchronous rectifier M4 is correspondingly reduced; when primary side switching frequency fSWWhen the current is reduced, the conduction time of the secondary synchronous rectifier M4 should be increased correspondingly.
The operation of the control system 100 is described below by way of an example, with reference to fig. 3:
firstly, it is determined whether the synchronous rectifier M4 is turned off, if so, the sampling circuit 10 starts to operate, otherwise, the determination is returned to. When the synchronous rectifier M4 is turned off, the sampling circuit 10 collects the voltage signal V when the rectifier is turned off from the drain of the synchronous rectifier M4 on the secondary side of the LLC converterSRIs transmitted to the MCU, and V is transmitted through a comparator 20 in the MCUSRHigh level V set with MCU comparatorHA comparison and logical decision is made. If VSR<VHIf yes, the synchronous rectifier tube M4 is turned off at low level, and the control flow is ended; if VSR<VHIf not, the synchronous rectifier M4 is turned off at high level according to the switching frequency f of the primary power tubeSWTo adjust the conduction time of the synchronous rectifier M4 in the next cycle. If fSWIf the increase is true, the conduction time of the synchronous rectifier M4 in the next period is decreased by delta t, if the increase is not true, i.e. fSWIf the current is decreased, the conduction time of the synchronous rectifier tube M4 in the next period is increased by Δ t, and the operation procedure of the sampling circuit 10 is returned to, and the above steps are repeated.
In one embodiment, the control process of the control system 100 is as follows: synchronous rectification in each duty cycleDuring the detection period of the off state of the pipe M4, the switching frequency f of the primary side switching pipe is detectedSWThe variation trend of the sampling circuit 10 is detected and logically judged on the state of the secondary synchronous rectifier tube M4 of the LLC converter in the current period, the sampling circuit 10 starts to work in the time of the turn-off period of the secondary synchronous rectifier tube M4 of the LLC converter, and the sampling circuit 10 collects the voltage V at the drain end of the synchronous rectifier tube M4SRThe threshold voltage V is transmitted to the inverting input terminal of the comparator 20 and set by the control unit 30HComparing, judging logic, and controlling the conduction time of the synchronous rectifier M4 in the next working period according to the detection result, wherein the specific process is as follows:
(1) when primary side switching frequency fSWWhen the current is decreased, the turn-on time of the secondary synchronous rectifier M4 should be increased accordingly, see fig. 4.
If VSR1<VHIf the comparator output is 1, the turn-off time of the synchronous rectifier tube M4 in the current period is the proper turn-off time; wherein, VSR1The voltage at the drain of the synchronous rectifier M4 in the first cycle is shown.
If VSR1>VHWhen the comparator output is 0, the control unit 30 will increase a high level time Δ t in the next period to prolong the conduction time of the synchronous rectifier M4 in the next period, and the sampling circuit 10 collects the drain voltage V of the synchronous rectifier M4 in the second periodSR2The threshold voltage V set by the control unit 30 and transmitted to the inverting input terminal of the comparator 20HComparing;
if V is measured next every cycleSR>VHIf the output of the comparator 20 is 0, the next period continues to increase by a high level time Δ t;
up to V measured for the current cycleSR<VHWhen the output of the comparator 20 is 1, the synchronous rectifier M4 in this period is turned off at a low level.
(2) When primary side switching frequency fSWWhen the current is increased, the conduction time of the secondary synchronous rectifier M4 should be reduced, see fig. 5.
If VSR1<VHIf the comparator output is 1, the cycle is determinedWhen the SR is switched off, the low-level switching-off is performed;
if VSR1>VHIf the comparator output is 0, the high level time Δ t is decreased in the next period, the turn-on time of the synchronous rectifier M4 in the next period is shortened, and the drain voltage V4 of the synchronous rectifier M4 in the next period is collected by the sampling circuit 10SR2The threshold voltage V set by the control unit 30 and transmitted to the inverting input terminal of the comparator 20HComparing;
if V is measured next every cycleSR>VHIf the output of the comparator 20 is 0, the next period is continuously decreased by a high level time Δ t;
up to V measured for the current cycleSR<VHIf the output of the comparator 20 is 1, the synchronous rectifier M4 in the period is turned off at a low level.
According to the switching frequency f of a primary side switching tube of an LLC converterSWThe variation trend of the voltage is used for guiding the adjustment trend of the conduction time of the secondary synchronous rectifier tube M4 to adjust the drain-source voltage V of the LLC resonant converter synchronous rectifier tube M4SRWhen the value is sampled, 0 or 1 output is performed by the comparator 20 inside the MCU. The time length of the turn-on of the secondary synchronous rectifier M4 is changed by the control unit 30 in each switching period, so that the secondary synchronous rectifier M4 can be turned off at a low voltage level. Therefore, the secondary synchronous rectifier M4 of the LLC converter can be switched off at a low voltage point through the adjustment of a plurality of working cycles, and the function of self-adaptive synchronous rectification is realized. Compared with the mode of judging the state of the turn-off moment by collecting the current passing through the synchronous rectifier tube, the embodiment shown in fig. 2 does not need to sample the current through the detection resistor, and has an advantage in circuit loss; compared with the method of acquiring the drain-source voltage VDS of the synchronous rectifier tube, the method of controlling the on-off time of the synchronous rectifier tube by comparing the voltage with the on-threshold of the synchronous rectifier tube to determine whether the body diode of the synchronous rectifier tube is on or off is advantageous in circuit loss as the body diode of the synchronous rectifier tube can be switched on or off and the loss of the on body diode can be increased; phase (C)For detecting the conduction time of the body diode of the synchronous rectifier after the synchronous rectifier is turned off, judging the mode of adjusting the conduction time of the synchronous rectifier in the next period, when the system works at high frequency, the influence of the parasitic parameters of the added circuit is not negligible, and the sampling result of the MCU is influenced by the circuit oscillation generated by the parasitic parameters, so the design of the anti-noise capability of the circuit has to be considered, while the circuit structure of the embodiment shown in FIG. 2 is simple, no external complex circuit is needed, the MCU is used for realizing the required functions, and the parasitic effect caused by the parasitic parameters of the loop is reduced.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. An adaptive synchronous rectification control system of an LLC resonant converter, for turn-off control of a synchronous rectifier in a half-bridge LLC resonant converter with a synchronous rectifier, the system comprising:
the input end of the sampling circuit is connected with the drain electrode of the synchronous rectifying tube and is used for collecting the drain electrode voltage of the synchronous rectifying tube;
the input end of the comparator is connected with the output end of the sampling circuit and is used for comparing the input drain voltage with a preset voltage threshold value and outputting a comparison result;
the control unit is connected with the comparator and the grid electrode of the synchronous rectifying tube, is used for controlling the conducting time of the synchronous rectifying tube in one working period, and is also used for setting the conducting time of the synchronous rectifying tube in the next working period to be equal to the conducting time of the current working period when the drain voltage is smaller than a preset voltage threshold; the control unit is still used for obtaining the trend of change of the switching frequency of the switch tube of the half-bridge of the former avris of half-bridge LLC resonant converter increases when being in the trend of reducing synchronous rectifier is long when switching on of next duty cycle the switching frequency of the switch tube of the half-bridge of the former avris of half-bridge LLC resonant converter reduces when being in the trend of increasing synchronous rectifier is long when switching on of next duty cycle.
2. The adaptive synchronous rectification control system of the LLC resonant converter of claim 1, further comprising a gate driver, an input terminal of the gate driver being connected to an output terminal of the control unit, an output terminal of the gate driver being connected to a gate of the synchronous rectifier, the control unit controlling a duration of conduction of the synchronous rectifier within one duty cycle by the gate driver.
3. The adaptive synchronous rectification control system of the LLC resonant converter of claim 1, further comprising a PWM timer, an input end of the PWM timer being connected to an output end of the control unit, an output end of the PWM timer being connected to a gate of the synchronous rectification tube, the control unit controlling a conduction duration of the synchronous rectification tube in one duty cycle by adjusting a duty ratio of a PWM signal output by the PWM timer.
4. The adaptive synchronous rectification control system of the LLC resonant converter of claim 3, comprising an MCU integrated with said comparator, control unit and PWM timer.
5. The adaptive synchronous rectification control system of the LLC resonant converter of claim 1, wherein an inverting input terminal of the comparator is connected to the output terminal of the sampling circuit, a non-inverting input terminal of the comparator is connected to a voltage setting terminal of the control unit, the control unit further configured to set the preset voltage threshold.
6. The adaptive synchronous rectification control system of the LLC resonant converter of claim 1, wherein the sampling circuit has an absolute value sampling function, setting the drain voltage output to the comparator to a positive potential.
7. The adaptive synchronous rectification control system of the LLC resonant converter of claim 1, wherein the absolute values of said increased conduction period and said decreased conduction period are equal.
8. An adaptive synchronous rectification control method of an LLC resonant converter, which is used for carrying out turn-off control on a synchronous rectifier in a half-bridge LLC resonant converter with the synchronous rectifier, and is characterized by comprising the following steps:
step A, obtaining the drain voltage of a synchronous rectifier tube when the synchronous rectifier tube is turned off;
step B, if the drain voltage is smaller than a preset voltage threshold, setting the conduction time of the synchronous rectifier tube in the next working period to be equal to the conduction time of the current working period;
step C, if the drain voltage is larger than or equal to the preset voltage threshold, acquiring the switching frequency variation trend of a switching tube of a half bridge on the primary side of the half bridge LLC resonant converter;
step D, when the switching frequency is in a decreasing trend, increasing the conducting duration of the synchronous rectifier tube in the next working period, and returning to the step A in the next working period; and when the switching frequency is in an increasing trend, reducing the conducting time of the synchronous rectifier tube in the next working period, and returning to the step A in the next working period.
9. The adaptive synchronous rectification control method of the LLC resonant converter of claim 8, wherein if the switching frequency remains stable, after step B waiting a preset duration and returning to step A, the preset duration being greater than the duty cycle.
10. The adaptive synchronous rectification control method of the LLC resonant converter of claim 8, wherein said step D is such that the absolute values of the increased conduction period and the decreased conduction period at a time are equal.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113904419A (en) * | 2021-11-24 | 2022-01-07 | 中山市浩成自动化设备有限公司 | High-power battery charger and control method thereof |
Citations (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101577494A (en) * | 2008-05-09 | 2009-11-11 | 台达电子工业股份有限公司 | Synchronous rectification circuit with intermittent mode controller and control method thereof |
| CN103023335A (en) * | 2012-12-27 | 2013-04-03 | 万仁春 | LLC (logical link control) converter synchronous rectification method and device |
| CN104065275A (en) * | 2014-06-16 | 2014-09-24 | 矽力杰半导体技术(杭州)有限公司 | Quasi-resonance control circuit and method for zero-voltage switching and flyback converter |
| US20150124492A1 (en) * | 2013-11-04 | 2015-05-07 | Futurewei Technologies, Inc. | Apparatus and Method for High Efficiency LLC Resonant Converters |
| US20150365006A1 (en) * | 2014-06-13 | 2015-12-17 | Fairchild Korea Semiconductor Ltd. | Conduction detecting circuit, rectifying switch controlling circuit including the conduction detecting circuit and power supply for the rectifying switch controlling circuit to be applied |
| CN106026712A (en) * | 2016-07-15 | 2016-10-12 | 深圳南云微电子有限公司 | Secondary-side control method and secondary-side control circuit of switching power supply |
| CN107147302A (en) * | 2017-02-28 | 2017-09-08 | 东南大学 | The numerical control system and its control method of a kind of synchronous rectification LLC converters |
| CN107425728A (en) * | 2017-02-28 | 2017-12-01 | 东南大学 | The digital optimal control method and its system of a kind of LLC full-bridge converters synchronous rectification |
| US20170358979A1 (en) * | 2016-06-10 | 2017-12-14 | Crane Electronics, Inc. | Dynamic sharing average current mode control for active-reset and self-driven synchronous rectification for power converters |
| CN107979287A (en) * | 2016-10-25 | 2018-05-01 | 万国半导体(开曼)股份有限公司 | Zero voltage switch formula inverter for main switch switch transition |
| CN108306513A (en) * | 2018-02-27 | 2018-07-20 | 成都芯源系统有限公司 | Turn-off control circuit of synchronous rectifier tube and synchronous rectifier control circuit |
| US20180254712A1 (en) * | 2016-10-25 | 2018-09-06 | Alpha And Omega Semiconductor Incorporated | Forced zero voltage switching flyback converter |
| CN108551263A (en) * | 2018-06-27 | 2018-09-18 | 上海新进半导体制造有限公司 | A kind of control device, method and the energy converter of adaptive secondary side synchronous rectification |
| CN108988648A (en) * | 2018-07-06 | 2018-12-11 | 华南理工大学 | A kind of LLC resonant converter synchronous rectification forecast Control Algorithm |
| CN109067181A (en) * | 2018-07-18 | 2018-12-21 | 东南大学 | The adaptive synchronous commutating control system and control method of active clamp flyback converter |
-
2018
- 2018-12-24 CN CN201811585002.6A patent/CN111355392B/en active Active
Patent Citations (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101577494A (en) * | 2008-05-09 | 2009-11-11 | 台达电子工业股份有限公司 | Synchronous rectification circuit with intermittent mode controller and control method thereof |
| CN103023335A (en) * | 2012-12-27 | 2013-04-03 | 万仁春 | LLC (logical link control) converter synchronous rectification method and device |
| US20150124492A1 (en) * | 2013-11-04 | 2015-05-07 | Futurewei Technologies, Inc. | Apparatus and Method for High Efficiency LLC Resonant Converters |
| US20150365006A1 (en) * | 2014-06-13 | 2015-12-17 | Fairchild Korea Semiconductor Ltd. | Conduction detecting circuit, rectifying switch controlling circuit including the conduction detecting circuit and power supply for the rectifying switch controlling circuit to be applied |
| CN104065275A (en) * | 2014-06-16 | 2014-09-24 | 矽力杰半导体技术(杭州)有限公司 | Quasi-resonance control circuit and method for zero-voltage switching and flyback converter |
| US20170358979A1 (en) * | 2016-06-10 | 2017-12-14 | Crane Electronics, Inc. | Dynamic sharing average current mode control for active-reset and self-driven synchronous rectification for power converters |
| CN106026712A (en) * | 2016-07-15 | 2016-10-12 | 深圳南云微电子有限公司 | Secondary-side control method and secondary-side control circuit of switching power supply |
| CN107979287A (en) * | 2016-10-25 | 2018-05-01 | 万国半导体(开曼)股份有限公司 | Zero voltage switch formula inverter for main switch switch transition |
| US20180254712A1 (en) * | 2016-10-25 | 2018-09-06 | Alpha And Omega Semiconductor Incorporated | Forced zero voltage switching flyback converter |
| CN107425728A (en) * | 2017-02-28 | 2017-12-01 | 东南大学 | The digital optimal control method and its system of a kind of LLC full-bridge converters synchronous rectification |
| CN107147302A (en) * | 2017-02-28 | 2017-09-08 | 东南大学 | The numerical control system and its control method of a kind of synchronous rectification LLC converters |
| CN108306513A (en) * | 2018-02-27 | 2018-07-20 | 成都芯源系统有限公司 | Turn-off control circuit of synchronous rectifier tube and synchronous rectifier control circuit |
| CN108551263A (en) * | 2018-06-27 | 2018-09-18 | 上海新进半导体制造有限公司 | A kind of control device, method and the energy converter of adaptive secondary side synchronous rectification |
| CN108988648A (en) * | 2018-07-06 | 2018-12-11 | 华南理工大学 | A kind of LLC resonant converter synchronous rectification forecast Control Algorithm |
| CN109067181A (en) * | 2018-07-18 | 2018-12-21 | 东南大学 | The adaptive synchronous commutating control system and control method of active clamp flyback converter |
Non-Patent Citations (2)
| Title |
|---|
| 第12期: ""高效率数字电源谐振和同步整流控制策略研究"", 《中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑》 * |
| 郭跃森等: "带维持电容自适应LLC谐振变换器同步整流", 《电力电子技术》 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113904419A (en) * | 2021-11-24 | 2022-01-07 | 中山市浩成自动化设备有限公司 | High-power battery charger and control method thereof |
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