WO2022247531A1 - 谐振变换系统和控制方法 - Google Patents

谐振变换系统和控制方法 Download PDF

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Publication number
WO2022247531A1
WO2022247531A1 PCT/CN2022/087628 CN2022087628W WO2022247531A1 WO 2022247531 A1 WO2022247531 A1 WO 2022247531A1 CN 2022087628 W CN2022087628 W CN 2022087628W WO 2022247531 A1 WO2022247531 A1 WO 2022247531A1
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Prior art keywords
signal
slope
threshold
current threshold
current
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PCT/CN2022/087628
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English (en)
French (fr)
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陈建
刘源俊
胡志祥
王帅兵
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华为数字能源技术有限公司
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Publication of WO2022247531A1 publication Critical patent/WO2022247531A1/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
    • H02M3/01—Resonant DC/DC converters
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/12—Measuring rate of change
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • 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
    • H02M3/33571—Half-bridge at primary side of an isolation transformer
    • 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

Definitions

  • the present application relates to the technical field of switching converters, and more particularly, relates to a resonant conversion system and a control method.
  • the resonant soft switching topology can achieve soft switching control through zero voltage switching (ZVS) technology.
  • the half-bridge LLC usually adopts pulse frequency modulation (pulse frequency modulation, PFM).
  • PFM pulse frequency modulation
  • the switching tube S1 and the switching tube S2 are each turned on for 50% of the time, and the resonant cavity is changed by adjusting the switching frequency fs.
  • Input and output voltage gain to realize the adjustment of the output voltage.
  • the gain curve can be divided into an inductive area and a capacitive area.
  • the half-bridge LLC needs to work in the inductive region; if it works in the capacitive region, ZVS cannot be realized, and there is a risk of S1 and S2 through-through.
  • the traditional method usually uses the frequency limiting method to limit the lowest operating frequency, so that the operating frequency is greater than fm, but under some abnormal conditions, such as output short circuit, overload, etc., the frequency limiting method will fail and the entire system Working in the capacitive region, the zero-voltage turn-on of the switch cannot be realized.
  • the present application provides a resonant conversion system and a control method, which enable the system to continuously work in the inductive mode, ensure the zero-voltage turn-on of the switch, and at the same time work in a state close to the capacitive mode to maximize the use of the gain range.
  • a resonant conversion system including: a controller; a resonant conversion circuit, including a high-frequency chopper circuit, a resonant cavity, a transformer, and a rectification filter network, the high-frequency chopper circuit includes switches S1 and S2, and the controller uses By controlling the on-off of switches S1 and S2, the DC voltage input to the high-frequency chopper circuit is converted into a high-frequency square wave.
  • the resonant cavity and the transformer are used to receive the high-frequency square wave and couple the power from the primary side of the transformer to the secondary
  • the rectification and filtering network is used to convert the AC voltage coupled to the secondary side of the transformer into a DC voltage
  • the controller is also used to detect the midpoint voltage V SW of the bridge arm, and determine the second voltage according to the midpoint voltage V SW of the bridge arm
  • An electrical signal the midpoint voltage V SW of the bridge arm is the voltage at the midpoint of the bridge arm connected to the switches S1 and S2, the first electrical signal has a correlation with the slope of the midpoint voltage Vsw of the bridge arm;
  • the first electrical signal determines the current threshold signal , the current threshold signal is used to indicate the current threshold;
  • the resonant current on the primary side of the transformer is detected, and the resonant current is compared with the current threshold signal to determine a second electrical signal, which is used to indicate the comparison result; according to the second electrical signal Control the on-off of switch S1 or S2 to
  • the interval of gain is maximized.
  • the first electrical signal includes a first pulse signal slp1 and a second pulse signal slp2, and the controller is specifically configured to:
  • the slope signal V SLP indicates the slope of the midpoint voltage V SW of the bridge arm; according to the slope signal V SLP and the first slope threshold V TH1 , determine the first pulse signal slp1, the pulse length of the first pulse signal slp1 is used to indicate the duration tslp1 of the slope signal V SLP greater than the first slope threshold V TH1 ; according to the slope signal V SLP and the second slope threshold V TH2 , determine the second Two pulse signals slp2, the pulse length of the second pulse signal slp2 is used to indicate the duration tslp2 when the slope signal V SLP is smaller than the second slope threshold V TH2 , the second slope threshold V TH2 is smaller than the first slope threshold V TH1 .
  • the current threshold signal includes a first current threshold signal for indicating the first current threshold ith1 and a second current threshold signal for indicating the second current threshold ith2,
  • the controller is further configured to: determine the first current threshold signal and the second current threshold signal according to the first pulse signal slp1 and the second pulse signal slp2, wherein the controller is specifically configured to:
  • a first initial current threshold and a second initial current threshold are determined, the first initial current threshold is a positive value, and the second initial current threshold is a negative value.
  • the duration tslp1 indicated by the pulse length of the first pulse signal is compared with the first time threshold Tth1, and when the duration tslp1 indicated by the pulse length of the first pulse signal is greater than the first time threshold Tth1, the first initial current threshold is reduced, In order to obtain the first current threshold ith1, when the duration tslp1 indicated by the pulse length of the first pulse signal is less than the first time threshold Tth1, increase the first initial current threshold to obtain the first current threshold ith1.
  • the duration tslp2 indicated by the pulse length of the second pulse signal is compared with the second time threshold Tth2, and when the duration tslp2 indicated by the pulse length of the second pulse signal is greater than the second time threshold Tth2, the second initial current threshold is increased , to obtain the second current threshold ith2, in the case that the duration tslp2 indicated by the pulse length of the second pulse signal is less than the second time threshold Tth2, reduce the second initial current threshold to obtain the second current threshold ith2.
  • the duration indicated by the pulse length of the pulse signal is determined, and the current threshold is adaptively adjusted to perform capacitive protection, so that the system continues to work in the inductive mode and meets the switching requirements. At the same time, it can make the system work in a state close to the capacitive mode, and maximize the use of the gain range.
  • the first electrical signal is a slope signal V SLP
  • the slope signal V SLP represents the slope of the midpoint voltage V SW of the bridge arm
  • the slope detection circuit is specifically used for:
  • the midpoint voltage V SW of the bridge arm is detected, and the slope signal V SLP is output according to the midpoint voltage V SW of the bridge arm.
  • the current threshold signal includes a first current threshold signal for indicating the first current threshold ith1 and a second current threshold signal for indicating the second current threshold ith2
  • the controller is also used to: determine the first current threshold signal and the second current threshold signal according to the slope signal V SLP , wherein the controller is specifically used to:
  • a first initial current threshold and a second initial current threshold are determined, the first initial current threshold is a positive value, and the second initial current threshold is a negative value.
  • the speed of the voltage change is determined, the current threshold is adaptively adjusted, and capacitive protection is performed, so that the system continues to work in the inductive mode and satisfies the zero-voltage turn-on of the switch , and at the same time, it can make the system work in a state close to the capacitive mode, and maximize the use of the gain interval.
  • the second electrical signal includes the first switching signal ic1 and the second switching signal ic2, and the controller is further configured to: detect the resonant current icr on the primary side of the transformer; and the current threshold signal, and output the first switch signal ic1 and the second switch signal ic2, the current threshold signal includes the first current threshold signal for indicating the first current threshold ith1 and the second current threshold signal for indicating the second current threshold ith2 A current threshold signal, wherein the controller is specifically used to:
  • the controller is specifically configured to: determine the first control signal DRV1 according to the first switch signal ic1, and the first control signal DRV1 is used to control the on-off of the switch S1;
  • the second switch signal ic2 determines the second control signal DRV2, and the second control signal DRV2 is used to control the on-off of the switch S2.
  • the controller includes: a slope detection circuit, a threshold control circuit, a current comparison circuit and a switch control circuit.
  • the slope detection circuit includes: a detection capacitor Csw and a detection resistor Rsw.
  • the first end of the detection capacitor Csw is used to receive the midpoint voltage Vsw of the bridge arm, the second end of the detection capacitor Csw is connected to the first end of the detection resistor Rsw, and the second end of the detection resistor Rsw is grounded, wherein the detection resistor Rsw The first terminal of is used to output the slope signal V SLP .
  • the slope detection circuit further includes: a first comparator CMP1 , a second comparator CMP2 and a first invertor INV1 .
  • the first input terminal and the second input terminal of the first comparator CMP1 are respectively used for receiving the slope signal V SLP and the first slope threshold value V TH1 signal, and the output terminal of the first comparator CMP1 is used for outputting the first pulse signal slp1
  • the first input end and the second input end of the second comparator CMP2 are respectively used to receive the slope signal V SLP and the second slope threshold value V TH2 signal, the output end of the second comparator CMP2 and the input end of the first NOT gate INV1 connected, the output terminal of the first inverting gate INV1 is used to output the second pulse signal slp2.
  • the current comparison circuit includes: a third comparator CMP3, a fourth comparator CMP4, and a second invertor INV2.
  • the first input terminal and the second input terminal of the third comparator CMP3 are respectively used to receive the resonant current icr and the first current threshold ith1, and the output terminal of the third comparator CMP3 is used to output the first switching signal ic1;
  • the fourth The first input terminal and the second input terminal of the comparator CMP4 are respectively used to receive the resonant current icr and the second current threshold ith2, the output terminal of the fourth comparator CMP4 is connected to the input terminal of the second invertor INV2, and the second invertor The output end of INV2 is used to output the second switching signal ic2.
  • the resonant conversion system includes: a controller; a resonant conversion circuit including a high-frequency chopper circuit, a resonant cavity, a transformer, and a rectification filter network.
  • the high-frequency chopper circuit includes a switch S1 and S2, the controller is used to convert the DC voltage input into the high-frequency chopper circuit into a high-frequency square wave by controlling the on-off of the switches S1 and S2, and the resonant cavity and the transformer are used to receive the high-frequency square wave and transfer the electric energy from the transformer
  • the primary side of the transformer is coupled to the secondary side, and the rectification and filtering network is used to convert the AC voltage coupled to the secondary side of the transformer into a DC voltage.
  • the method includes: the controller detects the midpoint voltage V SW of the bridge arm, and determines the first electrical signal according to the midpoint voltage V SW of the bridge arm, and the midpoint voltage V SW of the bridge arm is the voltage of the midpoint of the bridge arm connected to the switches S1 and S2 , the first electrical signal has a correlation with the slope of the bridge arm midpoint voltage Vsw; the controller determines the current threshold signal according to the first electrical signal, and the current threshold signal is used to indicate the current threshold; the controller detects the resonant current on the primary side of the transformer, and The resonant current is compared with the current threshold signal to determine a second electrical signal, which is used to indicate the comparison result; the controller controls the on-off of the switch S1 or S2 according to the second electrical signal, so that the system works in an inductive mode.
  • the interval of gain is maximized.
  • the first electrical signal includes a first pulse signal slp1 and a second pulse signal slp2, and the controller detects the bridge arm midpoint voltage V SW , and according to the bridge arm midpoint The voltage V SW determines the first electrical signal, including:
  • the controller detects the midpoint voltage V SW of the bridge arm, and determines the slope signal V SLP according to the midpoint voltage V SW of the bridge arm, and the slope signal V SLP represents the slope of the midpoint voltage V SW of the bridge arm;
  • the controller determines the first pulse signal slp1 according to the slope signal V SLP and the first slope threshold V TH1 , and the pulse length of the first pulse signal slp1 is used to indicate the duration tslp1 during which the slope signal V SLP is greater than the first slope threshold V TH1 ;
  • the controller determines the second pulse signal slp2 according to the slope signal V SLP and the second slope threshold V TH2 , the pulse length of the second pulse signal slp2 is used to indicate the duration tslp2 of the slope signal V SLP less than the second slope threshold V TH2 , the second The slope threshold V TH2 is smaller than the first slope threshold V TH1 .
  • the current threshold signal includes a first current threshold signal for indicating the first current threshold ith1 and a second current threshold signal for indicating the second current threshold ith2,
  • the controller determining the current threshold signal according to the first electrical signal includes: the controller determining the first current threshold signal and the second current threshold signal according to the first pulse signal slp1 and the second pulse signal slp2.
  • determining the first current threshold signal and the second current threshold signal includes:
  • the controller determines a first initial current threshold and a second initial current threshold, the first initial current threshold is positive and the second initial current threshold is negative.
  • the controller compares the duration tslp1 indicated by the pulse length of the first pulse signal with the first time threshold Tth1, and if the duration tslp1 indicated by the pulse length of the first pulse signal slp1 is greater than the first time threshold Tth1, reduces the first initial current threshold to obtain the first current threshold ith1, and increase the first initial current threshold to obtain the first current threshold ith1 when the duration tslp1 indicated by the pulse length of the first pulse signal slp1 is less than the first time threshold Tth1.
  • the controller compares the duration tslp2 indicated by the pulse length of the second pulse signal with the second time threshold Tth2, and if the duration tslp2 indicated by the pulse length of the second pulse signal slp2 is greater than the second time threshold Tth2, increases the second The initial current threshold to obtain the second current threshold ith2, when the duration tslp2 indicated by the pulse length of the second pulse signal slp2 is less than the second time threshold Tth2, reduce the second initial current threshold to obtain the second current threshold ith2 .
  • the duration indicated by the pulse length of the pulse signal is determined, and the current threshold is adaptively adjusted to perform capacitive protection, so that the system continues to work in the inductive mode and meets the switching requirements. At the same time, it can make the system work in a state close to the capacitive mode, and maximize the use of the gain range.
  • the first electrical signal is a slope signal V SLP
  • the slope signal V SLP represents the slope of the midpoint voltage V SW of the bridge arm
  • the controller detects the midpoint voltage V SW of the bridge arm SW
  • determining the first electrical signal according to the midpoint voltage V SW of the bridge arm includes: the controller detects the midpoint voltage V SW of the bridge arm, and determines the slope signal V SLP according to the midpoint voltage V SW of the bridge arm.
  • the current threshold signal includes a first current threshold signal for indicating the first current threshold ith1 and a second current threshold signal for indicating the second current threshold ith2,
  • the controller determining the current threshold signal according to the first electrical signal includes: the controller determining the first current threshold signal and the second current threshold signal according to the slope signal V SLP .
  • the threshold control circuit determines the first current threshold signal and the second current threshold signal according to the slope signal V SLP , including:
  • a first initial current threshold and a second initial current threshold are determined, the first initial current threshold is a positive value, and the second initial current threshold is a negative value.
  • the controller compares the slope signal V SLP with the third slope threshold V TH3 , and in the case that the slope signal V SLP is greater than the third slope threshold V TH3 , reduces the first initial current threshold to obtain the first current threshold ith1, at the slope
  • the first initial current threshold is increased to obtain the first current threshold ith1 .
  • the controller compares the slope signal V SLP with the fourth slope threshold V TH4 , and increases the second initial current threshold to obtain the second current threshold ith2 when the slope signal V SLP is greater than the fourth slope threshold V TH4 .
  • the slope signal V SLP is smaller than the fourth slope threshold V TH4
  • the second initial current threshold is decreased to obtain the second current threshold ith2
  • the fourth slope threshold V TH4 is smaller than the third slope threshold V TH3 .
  • the speed of the voltage change is determined, the current threshold is adaptively adjusted, and capacitive protection is performed, so that the system continues to work in the inductive mode and satisfies the zero-voltage turn-on of the switch , and at the same time, it can make the system work in a state close to the capacitive mode, and maximize the use of the gain interval.
  • the second electrical signal includes the first switching signal ic1 and the second switching signal ic2
  • the controller detects the resonant current on the primary side of the transformer, and compares the resonant current with the current threshold signal Comparing and determining the second electrical signal includes: the controller detects the resonant current icr on the primary side of the transformer; the controller determines the first switching signal ic1 and the second switching signal ic2 according to the resonant current icr and the current threshold signal, and the current threshold signal includes The first current threshold signal for indicating the first current threshold ith1 and the second current threshold signal for indicating the second current threshold ith2.
  • the controller determines the first switch signal ic1 and the second switch signal ic2 according to the resonant current icr and the current threshold signal, including:
  • the controller compares the resonant current icr with the first current threshold ith1, when the resonant current icr is greater than the first current threshold ith1, the first switch signal ic1 is used to instruct to turn on the switch S1, and when the resonant current icr is smaller than the first current threshold In the case of ith1, the first switch signal ic1 is used to instruct to turn off the switch S1 and determine the first switch signal ic1.
  • the controller compares the resonant current icr with the second current threshold ith2. When the resonant current icr is greater than the second current threshold ith2, the second switch signal ic2 is used to instruct to turn off the switch S2. When the resonant current icr is smaller than the second current In the case of the threshold ith2, the second switch signal ic2 is used to indicate to turn on the switch S2, and the second switch signal ic2 is determined.
  • the controller controls the on-off of the switch S1 or S2 according to the second electrical signal, including: the controller determines the first control signal DRV1 according to the first switch signal ic1, the first The control signal DRV1 is used to control the on-off of the switch S1; the controller determines the second control signal DRV2 according to the second switch signal ic2, and the second control signal DRV2 is used to control the on-off of the switch S2.
  • the controller includes: a slope detection circuit, a threshold control circuit, a current comparison circuit and a switch control circuit.
  • Figure 1 is a schematic diagram of a DC-DC resonant converter.
  • FIG. 2 is a schematic diagram of a half-bridge LLC resonant converter topology 200 .
  • Figure 3 is a schematic diagram of the inductive and capacitive regions of LLC work.
  • Fig. 4 is a schematic structural diagram of an example of a resonant conversion system provided by an embodiment of the present application.
  • FIG. 5 is a schematic structural diagram of an example of a slope detection circuit provided by an embodiment of the present application.
  • FIG. 6 is a schematic structural diagram of an example of a current comparison circuit provided by an embodiment of the present application.
  • FIG. 7 is a waveform diagram of an example of a threshold control circuit and a switch control circuit provided by the embodiment of the present application.
  • Fig. 8 is a schematic structural diagram of another example of the resonant conversion system provided by the embodiment of the present application.
  • FIG. 9 is a schematic structural diagram of another example of the slope detection circuit provided by the embodiment of the present application.
  • Fig. 10 is a waveform diagram of another example of the threshold control circuit and the switching circuit provided by the embodiment of the present application.
  • Fig. 11 is a schematic flowchart of an example of a method for controlling a resonant conversion system provided by an embodiment of the present application.
  • Fig. 12 is a schematic flowchart of another example of the method for controlling the resonant conversion system provided by the embodiment of the present application.
  • Fig. 13 is a schematic block diagram of an example of a control device provided by an embodiment of the present application.
  • FIG 1 is a schematic diagram of a typical DC-DC resonant converter.
  • the resonant converter can take the DC input through high-frequency chopping to obtain a high-frequency square wave, then realize voltage regulation and soft switching through the resonant cavity and transformer, and finally obtain the required DC output through rectification and filtering .
  • the high-frequency chopper circuit adopts a half-bridge circuit
  • the resonant cavity adopts an LLC type
  • the rectifier adopts a diode full-wave rectification
  • the commonly used half-bridge LLC resonant converter topology 100 as shown in Figure 1(b) hereinafter referred to as half Bridge LLC).
  • the resonant converter 100 includes a high frequency chopper circuit 101 , a resonant cavity 102 , a transformer 103 and a rectifying and filtering network 104 .
  • the high-frequency chopper circuit 101 includes an input filter capacitor C1, switches S1 and S2 (the diode on the switch is its body diode, and the capacitor is its parasitic capacitance);
  • the resonant cavity 102 includes a resonant inductor Lr and a resonant capacitor Cr, and the resonant inductor Lr includes the leakage inductance of the transformer and the external inductance, and can also be fully integrated in the transformer 103.
  • the transformer 103 can be a transformer Tr, and its primary side excitation inductance is Lm;
  • the rectifier filter network 104 includes diodes D1 and D2, and the output filter capacitor CO .
  • Half-bridge LLC usually adopts pulse frequency modulation (pulse frequency modulation, PFM).
  • PFM pulse frequency modulation
  • S1 and S2 are each turned on for 50% of the time, and the input and output voltage gain of the resonant cavity is changed by adjusting the switching frequency fs , to achieve the regulation of the output voltage.
  • the resonant cavity obtains two resonant frequencies as follows:
  • formula (1) expresses the resonance frequency when the excitation inductance Lm of the transformer does not participate in the resonance
  • formula (2) expresses the resonance frequency when the excitation inductance Lm of the transformer participates in the resonance.
  • the resonant frequency its gain curve can be divided into inductive area and capacitive area.
  • fm is the frequency of the gain peak point, which is also the boundary point between the capacitive area and the inductive area.
  • the voltage gain is constant is 1.
  • the half-bridge LLC In order to realize the zero-voltage turn-on of S1 and S2, the half-bridge LLC needs to work in the inductive region; if it works in the capacitive region, ZVS cannot be realized, and there is a risk of S1 and S2 through-through.
  • the traditional frequency limiting method is usually used to limit the lowest operating frequency, so that the operating frequency is greater than fm, but under some abnormal conditions, such as output short circuit, overload, etc., after the system Q value increases, the fm value increases If it is large, it will cause the frequency limiting method to fail and enter the capacitive region to work.
  • the oscillator delay time is a preset fixed value, after the oscillator delay time ends , it is possible that the voltage at the SW point has not dropped to zero, resulting in the inability to realize the zero-voltage turn-on of the switch tube.
  • the present application provides a resonant conversion system, which enables the system to work continuously in the inductive mode to ensure the zero-voltage turn-on of the switch, and at the same time, it can work in a state close to the capacitive mode to maximize the use of the gain interval.
  • Fig. 4 shows a schematic structural diagram of an example of the transformation system provided by the embodiment of the present application.
  • the resonant conversion system 300 includes a resonant conversion circuit 310 and a controller 320 .
  • the controller 320 includes a slope detection circuit, a threshold control circuit, a current comparison circuit and a switch control circuit.
  • the structure of the resonant conversion circuit 310 is basically the same as that of the resonant converter 100 shown in FIG.
  • the switches S1 and S2 in the resonant conversion circuit 310 may be silicon carbide (silicon carbide, SiC) or gallium nitride (gallium nitride, Metal-oxide-semiconductor field-effect transistor (MOSFET) or insulated gate bipolar transistor (insulated gate bipolar transistor, IGBT) made of materials such as GaN), which is not limited in this application.
  • silicon carbide silicon carbide, SiC
  • gallium nitride gallium nitride
  • MOSFET Metal-oxide-semiconductor field-effect transistor
  • IGBT insulated gate bipolar transistor
  • the controller can detect the voltage at the midpoint of the bridge arm through the slope detection circuit, and adaptively adjust the current threshold through the threshold control circuit according to the time length indicated by the pulse length of the midpoint voltage change signal pulse of the bridge arm, Finally, the current comparator circuit is used to control the switching off of the switch to limit the frequency from entering the capacitive region, so that the system can work close to the capacitive region and maximize the use of the gain range.
  • FIG. 5 shows a schematic structural diagram of an example of the slope detection circuit provided by the embodiment of the present application.
  • the slope detection circuit includes a detection capacitor Csw, a detection resistor Rsw, two comparators CMP1 and CMP2, and an inverter INV1, and its working waveform is shown in Figure (b).
  • switch S1 is turned off and S2 is turned on, the midpoint voltage of the bridge arm will drop from Vin; correspondingly, when S2 is turned off and S1 is turned on, the midpoint voltage of the bridge arm will rise from 0. Therefore, the voltage change at the midpoint of the bridge arm can be detected according to the detection capacitor Csw and the detection resistor Rsw.
  • Its change slope Vslp is shown in formula (3):
  • Vslp When Vslp is greater than V TH1 , the output of slp1 is set to 1, and when Vslp is less than V TH2 , the output of slp2 is set to 1, so the change of the slope at SW can be detected through slp1 and slp2, wherein the embodiment of the present application sets the speed threshold V TH1 and
  • the way of determining V TH2 is not limited, for example, it may be based on actual test, simulation or theoretical calculation.
  • dvsw/dt can be obtained according to the size of the resonant current combined with the resonant capacitor, and the threshold values of V TH1 and V TH2 can be obtained by sampling the resistance and capacitance parameters according to the slope, where V TH2 is smaller than V TH1 ,
  • V TH1 can be a positive value
  • V TH2 can be a negative value.
  • FIG. 6 shows a schematic structural diagram of an example of the current comparison circuit provided by the embodiment of the present application.
  • the current comparison circuit includes two comparators CMP3 and CMP4 and a non-gate INV2, and its waveform diagram is shown in Figure 6(b).
  • icr is the sampling current of the resonant capacitor Cr current. When the current is lower than the threshold ith1, the output of ic1 is set to 0. When icr is greater than ith2, the output of ic2 is set to 0 by 1.
  • the current comparison circuit is used to judge the capacitive mode.
  • Fig. 7 shows the threshold control circuit and the switch control circuit waveform diagram provided by the embodiment of the present application, wherein the first current threshold ith1 and the second current threshold ith2 are determined by the threshold control circuit respectively, the first initial current threshold and the second initial current threshold The current threshold is obtained after adjustment, and the first initial current threshold and the first initial current threshold are preset values according to circuit design.
  • the first initial current threshold can be a positive value
  • the second initial current threshold can be a negative value.
  • the first initial current threshold and the second initial current threshold can be determined by It can be determined by means of actual test, simulation or theoretical calculation.
  • DRV 2 is turned off, at this time icr is still greater than ith2, and the capacitive mode is not triggered; at time t 3 , slp1 changes from 1 to 0, indicating that the Vsw voltage decreases from Vin to 0, and at this time the conduction ZVS can be achieved through S1.
  • Fig. 7(b) shows the threshold control circuit and switch control circuit waveforms in the near-capacitive mode.
  • the switching frequency of switches S1 and S2 is continuously reduced to close to the resonant frequency fm, that is, close to the capacitive region, as shown in Figure 7(b)
  • the resonant current icr is greater than ith2 at time t3 , and ic2 changes from 1 to 0.
  • S2 is turned off, the switching frequency of S1 and S2 will be limited and will not continue to decrease and enter the capacitive region.
  • the resonant current icr will discharge the capacitor of S1 and charge the capacitor of S2, the voltage of sw point will rise, and slp1 will be obtained through the slope detection circuit.
  • the threshold control circuit can perform adaptive adjustment of the current threshold ith1 and ith2 by detecting slp1 (or slp2), so as to ensure that the system continues to work in the inductive mode, satisfying the zero-voltage turn-on of the switch, and can work in a state close to the capacitive mode, the maximum Maximize the use of gain intervals.
  • the threshold control circuit can detect the time length tslp1 (t 4 -t 3 ) indicated by the pulse length of slp1.
  • tslp1 is greater than the time threshold Tth1
  • time threshold Tth1 is a fixed preset value, which can be determined by means of actual test, simulation, or theoretical calculation, and the present application does not limit the way of determination. The same is true for the time threshold Tth2 below, which will not be repeated here.
  • the threshold control circuit detects the time length tslp2 indicated by the pulse length of slp2. When the time tslp2 indicated by the pulse length is less than the time threshold Tth2, it is judged that the current threshold is set too small, so the current threshold ith1 and ith2 (absolute value) are reduced.
  • the controller can detect the voltage at the midpoint of the bridge arm through the slope detection circuit, and adjust the current threshold adaptively according to the midpoint voltage of the bridge arm through the threshold control circuit, and finally control the switch off through the current comparison circuit , limiting the frequency will not enter the capacitive region, so that the system can continue to work in the inductive region, realize zero voltage turn-on, and maximize the use of the gain range.
  • FIG. 8 is a schematic diagram showing another example of the structure of the resonant conversion system provided by the embodiment of the present application.
  • the resonant conversion system 400 includes a resonant conversion circuit 410 and a controller 420 , whose structure is basically the same as that of the resonant conversion system 300 shown in FIG. 4 , and will not be repeated here.
  • the controller can detect the voltage at the midpoint of the bridge arm through the slope detection circuit, and adaptively adjust the current threshold according to the magnitude of the midpoint voltage change of the bridge arm through the threshold control circuit. Therefore, as shown in FIG. 9, in this embodiment, the slope detection circuit no longer sends the slp1 and slp2 signals to the threshold control circuit, but only provides them to the switch control circuit for dead-time control, and needs to output the Vslp signal to the threshold control circuit. Module, used for the judgment of ith1 and ith2.
  • the current comparison circuit is the same as that in the above embodiment, please refer to the description in FIG. 6 for details.
  • FIG. 10 shows a waveform diagram of a threshold control circuit and a switch control circuit provided by the embodiment of the present application.
  • slp1 and slp2 are also obtained by comparing Vslp and speed thresholds V TH1 and V TH2 , but they are only used for dead zone control.
  • slp2 changes from 1 to 0, which means that the Vsw voltage drops from Vin to 0.
  • S2 can be turned on.
  • the first current threshold ith1 and the second current threshold ith2 are respectively obtained by mediating the first initial current threshold and the second initial current threshold determined by the threshold control circuit, and the first initial current threshold and the second initial current threshold
  • An initial current threshold is a preset value according to circuit design.
  • the embodiment of the present application does not limit the manner of determining the speed thresholds V TH3 and V TH4 , for example, it may be based on actual tests, simulations, or theoretical calculations.
  • dvsw/dt can be obtained according to the size of the resonant current and combined with the resonant capacitor
  • the threshold value of V TH3 and V TH4 can be obtained by sampling the resistance and capacitance parameters according to the slope, where V TH4 is smaller than V TH3
  • V TH3 can be a positive value
  • V TH4 can be a negative value.
  • the adaptive adjustment of the current thresholds ith1 and ith2 is controlled by the voltage amplitude of Vslp and the thresholds V TH3 and V TH4 .
  • Vslp is lower than V TH3 during the period from t3 to t4 , indicating that the change speed of vsw is too slow, which may lead to the inability to fully utilize the gain range. Therefore, the current thresholds ith1 and ith2 (absolute value) can be increased.
  • the current threshold ith1 and ith2 can be reduced. After the current threshold ith1 and ith2 (absolute value) are reduced, the Vsw change speed becomes slower. In this way, the system can continue to work in the inductive mode to meet the zero voltage of the switch opened.
  • the controller can detect the voltage at the midpoint of the bridge arm through the slope detection circuit, and adjust the current threshold adaptively according to the midpoint voltage of the bridge arm through the threshold control circuit, and finally control the switch off through the current comparison circuit , limiting the frequency will not enter the capacitive region, so that the system can work close to the capacitive region, realize zero voltage turn-on, and maximize the use of the gain range.
  • Fig. 11 shows a schematic flowchart of an example of a method for controlling a resonance system provided by an embodiment of the present application.
  • the controller may include: a slope detection circuit, a threshold control circuit, a current comparison circuit and a switch control circuit.
  • a slope detection circuit In order to facilitate a clearer understanding of the technical solution of the present application, the actions of each part are described separately below, but it should not be used as a limitation to the technical solution of the present application.
  • the slope detection circuit, threshold control circuit, current comparison circuit and switch control circuit The steps or operations performed can all be performed by the controller.
  • the slope detection circuit detects the midpoint voltage V SW of the bridge arm, and outputs a slope signal V SLP according to the midpoint voltage V SW of the bridge arm.
  • the above-mentioned slope detection circuit may include: a detection capacitor Csw and a detection resistor Rsw.
  • the first end of the detection capacitor Csw is used to receive the midpoint voltage Vsw of the bridge arm, the second end of the detection capacitor Csw is connected to the first end of the detection resistor Rsw, and the second end of the detection resistor Rsw is grounded, wherein the first end of the detection resistor Rsw One end is used to output the slope signal V SLP .
  • the slope detection circuit may execute step S520, and the slope detection circuit outputs pulse signals slp1 and slp2 according to the slope signal V SLP .
  • the slope detection circuit further includes: a first comparator CMP1 , a second comparator CMP2 and a first inverter INV1 .
  • the first input terminal and the second input terminal of the first comparator CMP1 are respectively used to receive the slope signal V SLP and the first slope threshold value V TH1 signal, and the output terminal of the first comparator CMP1 is used to output the first pulse signal slp1;
  • the first input end and the second input end of the second comparator CMP2 are respectively used to receive the slope signal V SLP and the second slope threshold value V TH2 signal, and the output end of the second comparator CMP2 is connected with the input end of the first NOT gate INV1,
  • the output end of the first invertor INV1 is used to output the second pulse signal slp2.
  • the speed thresholds V TH1 and V TH2 can be determined in various ways, for example, according to actual tests, simulations, or theoretical calculations.
  • dvsw/dt can be obtained according to the size of the resonant current combined with the resonant capacitor
  • the threshold values of V TH1 and V TH2 can be obtained by sampling the resistance and capacitance parameters according to the slope, where V TH2 is smaller than V TH1 .
  • V TH1 can be a positive value
  • V TH2 can be a negative value.
  • the threshold control circuit may receive the first pulse signal slp1 and the first pulse signal slp2 output by the slope detection circuit, and execute step S530 to output current threshold signals ith1 and ith2 according to the pulse signals slp1 and slp2.
  • the first current threshold ith1 and the second current threshold ith2 are obtained after adjusting the first initial current threshold and the second initial current threshold respectively determined by the threshold control circuit, and the first initial current threshold and the second initial current threshold are obtained according to The preset value of the circuit design.
  • the first initial current threshold can be a positive value
  • the second initial current threshold can be a negative value.
  • the first initial current threshold and the second initial current threshold can be determined by the actual Determined by means of testing, simulation or theoretical calculation.
  • the threshold value control circuit compares the duration tslp1 indicated by the pulse length of the first pulse signal with the first time threshold Tth1, and in the case that the duration tslp1 indicated by the pulse length of the first pulse signal is greater than the first time threshold Tth1, the first initial current threshold to obtain the first current threshold ith1, and increase the first initial current threshold to obtain the first current threshold ith1 when the duration tslp1 indicated by the pulse length of the first pulse signal is less than the first time threshold Tth1.
  • time threshold Tth1 is a fixed preset value, which can be determined by means of actual test, simulation, or theoretical calculation, and the present application does not limit the way of determination. The same is true for the time threshold Tth2 below, which will not be repeated here.
  • the threshold control circuit compares the duration tslp2 indicated by the pulse length of the second pulse signal with the second time threshold Tth2, and increases the Increase the second initial current threshold to obtain the second current threshold ith2, and reduce the second initial current threshold to obtain the second current when the duration tslp2 indicated by the pulse length of the second pulse signal is less than the second time threshold Tth2 Threshold ith2.
  • the current comparison can receive the first current threshold ith1 and the second current threshold ith2, and execute step S540 to detect the resonant current, and compare the resonant current with the first The current threshold ith1 is compared with the second current threshold ith2, and the switching signals ic1 and ic2 are output.
  • the current comparison circuit may include: a third comparator CMP3 , a fourth comparator CMP4 and a second invertor INV2 .
  • the first input terminal and the second input terminal of the third comparator CMP3 are respectively used to receive the resonant current icr and the first current threshold ith1, and the output terminal of the third comparator CMP3 is used to output the first switching signal ic1;
  • the fourth comparator The first input terminal and the second input terminal of CMP4 are respectively used to receive the resonant current icr and the second current threshold ith2, the output terminal of the fourth comparator CMP4 is connected to the input terminal of the second invertor INV2, and the input terminal of the second invertor INV2 The output terminal is used to output the second switching signal ic2.
  • the switch control circuit outputs a control signal DRV1 to the switch S1 and a control signal DRV2 to the switch S2 according to the first switch signal ic1 and the second switch signal ic2, so as to control the on-off of the switches S1 and S2.
  • the resonant controller can detect the voltage at the midpoint of the bridge arm through the slope detection circuit, and adjust the current threshold adaptively according to the midpoint voltage of the bridge arm through the threshold control circuit, and finally control the switch on and off through the current comparison circuit Off, the frequency limit will not enter the capacitive region, so that the system can continue to work in the inductive region, realize zero voltage turn-on, and maximize the use of the gain range.
  • Fig. 12 shows a schematic flowchart of another example of the method for controlling the resonance system provided by the embodiment of the present application.
  • the controller may include: a slope detection circuit, a threshold control circuit, a current comparison circuit and a switch control circuit.
  • a slope detection circuit In order to facilitate a clearer understanding of the technical solution of the present application, the actions of each part are described separately below, but it should not be used as a limitation to the technical solution of the present application.
  • the slope detection circuit, threshold control circuit, current comparison circuit and switch control circuit The steps or operations performed can all be performed by the controller.
  • the resonant controller can detect the voltage at the midpoint of the bridge arm through the slope detection circuit, and adaptively adjust the current threshold according to the amplitude of the midpoint voltage change of the bridge arm through the threshold control circuit. Therefore, in this embodiment, the slope detection circuit no longer sends the slp1 and slp2 signals to the threshold control circuit, but needs to output the Vslp signal to the threshold control module for judging ith1 and ith2.
  • step S610 this step is consistent with step S510 shown in FIG. 11 , please refer to the description in FIG. 11 for details, and details are not repeated here.
  • the threshold control circuit outputs current threshold signals ith1 and ith2 according to the slope signal Vslp.
  • the first current threshold ith1 and the second current threshold ith2 are obtained after adjusting the first initial current threshold and the second initial current threshold respectively determined by the threshold control circuit, and the first initial current threshold and the second initial current threshold are obtained according to The preset value of the circuit design.
  • the first initial current threshold can be a positive value
  • the second initial current threshold can be a negative value.
  • the first initial current threshold and the second initial current threshold can be determined by the actual Determined by means of testing, simulation or theoretical calculation.
  • the threshold control circuit compares the slope signal V SLP with the third slope threshold V TH3 , and reduces the first initial current threshold to obtain the first current threshold ith1 when the slope signal V SLP is greater than the third slope threshold V TH3 .
  • the first initial current threshold is increased to obtain the first current threshold ith1 .
  • the threshold control circuit compares the slope signal V SLP with the fourth slope threshold V TH4 , and increases the second initial current threshold to obtain the second current when the slope signal V SLP is greater than the fourth slope threshold V TH4 Threshold ith2, when the slope signal V SLP is smaller than the fourth slope threshold V TH4 , reduce the second initial current threshold to obtain the second current threshold ith2.
  • the speed thresholds V TH3 and V TH4 can be determined in various ways, for example, according to actual tests, simulations, or theoretical calculations. As a possible implementation, it can be determined in the same way as the above-mentioned V TH1 and V TH2 . According to the size of the resonant current, combined with the resonant capacitor, dvsw/dt can be obtained, and V TH3 and V can be obtained by sampling the RC parameters according to the slope. Threshold value of TH4 , where V TH4 is smaller than V TH3 , optionally, V TH3 can be a positive value, and V TH4 can be a negative value.
  • step S630 which is the same as step S540 in FIG. Compared with ith2, output switching signals ic1 and ic2. Therefore, the switch circuit can continue to execute step S640, which is the same as step S550 in FIG. 11 , and will not be repeated here.
  • the resonant controller can detect the voltage at the midpoint of the bridge arm through the slope detection circuit, and adjust the current threshold adaptively according to the midpoint voltage of the bridge arm through the threshold control circuit, and finally control the switch on and off through the current comparison circuit Off, the frequency limit will not enter the capacitive region, so that the system can continue to work in the inductive region, realize zero voltage turn-on, and maximize the use of the gain range.
  • Fig. 13 shows a schematic structural block diagram of a control device provided by an embodiment of the present application.
  • the control device includes a processor 710 and a communication interface 720 .
  • the control device may also include a memory 730 .
  • the memory 730 may be included in the processor 710 .
  • the processor 710, the communication interface 720 and the memory 730 communicate with each other through an internal connection path, the memory 730 is used to store instructions, and the processor 710 is used to execute the instructions stored in the memory 730 to implement the control method provided by the embodiment of the present application.
  • control device can be used to perform the functions of the controller 320 in FIG. 4 or the controller 420 in FIG. 8, wherein the controller 320 and the controller 420 include a slope detection circuit, a threshold control circuit, a current comparison circuit and a switch Control circuit.
  • control device can also be used to execute the control method shown in FIG. 11 or FIG. 12 .
  • a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer.
  • an application running on a computing device and the computing device can be components.
  • One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers.
  • these components can execute from various computer readable media having various data structures stored thereon.
  • a component may, for example, be based on a signal having one or more packets of data (e.g., data from two components interacting with another component between a local system, a distributed system, and/or a network, such as the Internet via a signal interacting with other systems). Communicate through local and/or remote processes.
  • packets of data e.g., data from two components interacting with another component between a local system, a distributed system, and/or a network, such as the Internet via a signal interacting with other systems.
  • the disclosed systems, devices and methods may be implemented in other ways.
  • the device embodiments described above are only illustrative.
  • the division of the units is only a logical function division. In actual implementation, there may be other division methods.
  • multiple units or components can be combined or May be integrated into another system, or some features may be ignored, or not implemented.
  • the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of devices or units may be in electrical, mechanical or other forms.
  • the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.
  • each functional unit in each embodiment of the present application may be integrated into one processing unit, each unit may exist separately physically, or two or more units may be integrated into one unit.
  • the functions described above are realized in the form of software function units and sold or used as independent products, they can be stored in a computer-readable storage medium.
  • the technical solution of the present application is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including Several instructions are used to make a computer device (which may be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the methods described in the various embodiments of the present application.
  • the aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (read-only memory, ROM), random access memory (random access memory, RAM), magnetic disk or optical disc and other media that can store program codes. .

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Abstract

提供了一种谐振变换系统（300，400），包括：控制器（320，420）；谐振变换电路（310，410），包括高频斩波电路（101）、谐振腔（102）、变压器（103）和整流滤波网络（104），高频斩波电路（101）包括开关S1和S2；控制器（320，420）用于，检测桥臂中点电压V SW，并根据V SW确定第一电信号；根据第一电信号确定用于指示电流阈值的电流阈值信号（ith1，ith2）；检测变压器（103）初级侧的谐振电流，并将谐振电流与电流阈值信号（ith1，ith2）进行比较，确定用于指示比较结果的第二电信号；根据第二电信号控制开关S1或S2的通断，以使得系统工作在感性模式，保证开关的零电压开通，同时可以工作在接近容性模式的状态，最大化利用增益的区间。

Description

谐振变换系统和控制方法
本申请要求于2021年5月27日提交中国专利局、申请号为202110583363.2、申请名称为“谐振变换系统和控制方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及开关变换器技术领域，并且更具体地，涉及一种谐振变换系统和控制方法。
背景技术
随着电子电力领域迅猛发展，开关变换器应用越来越广泛，为了提高变换器的效率通常需要实现器件的软开关。谐振型软开关拓扑可通过零电压开通(zero voltage switching，ZVS)技术实现软开关控制。
半桥LLC通常采用脉冲频率调制控制(pulse frequency modulation，PFM)，一个周期内，忽略死区时间，开关管S1和开关管S2个各导通50％时间，通过调节开关频率fs改变谐振腔的输入输出电压增益，实现对输出电压的调节。其中，根据谐振频率可以将其增益曲线划分成感性区域和容性区域。为了实现开关管的零电压开通，半桥LLC需要工作在感性区域；若工作在容性区域，ZVS无法实现，还会有S1和S2直通的风险。为避免进入容性模式，传统手段通常采用限频法，限制最低的工作频率，使得工作频率大于fm，但是在一些异常条件下，如输出短路、过载等，会导致限频法失效使得整个系统进入容性区域工作，无法实现开关的零电压开通。
因此，亟需一种谐振变换系统，使得系统持续工作在感性模式，保证开关的零电压开通。
发明内容
本申请提供一种谐振变换系统和控制方法，使得系统持续工作在感性模式，保证开关的零电压开通，同时可以工作在接近容性模式的状态，最大化利用增益的区间。
第一方面，提供了一种谐振变换系统，包括：控制器；谐振变换电路，包括高频斩波电路、谐振腔、变压器和整流滤波网络，高频斩波电路包括开关S1和S2，控制器用于通过控制开关S1和S2的通断，将输入高频斩波电路的直流电压转变为高频方波，谐振腔和变压器用于接收高频方波并将电能从变压器的初级侧耦合至次级侧，整流滤波网络用于将耦合至变压器的次级侧的交流电压转换为直流电压；控制器还用于，检测桥臂中点电压V SW，并根据桥臂中点电压V SW确定第一电信号，桥臂中点电压V SW为开关S1和S2相连的桥臂中点的电压，第一电信号与桥臂中点电压Vsw的斜率具有关联关系；第一电信号确定电流阈值信号，电流阈值信号用于指示电流阈值；检测变压器初级侧的谐振电流，并将谐振电流与电流阈值信号进行比较，确定第二电信号，第二电信号用于指示比较结果； 根据第二电信号控制开关S1或S2的通断，以使得系统工作在感性模式。
根据本申请的技术方案，通过检测桥臂中点电压的变化情况，自适应调节电流阈值，进行容性保护，使得系统持续工作在感性模式下，满足开关的零电压开通，同时可以使系统工作在接近容性模式的状态，最大化利用增益的区间。
结合第一方面，在第一方面的某些实现方式中，第一电信号包括第一脉冲信号slp1和第二脉冲信号slp2，控制器具体用于：
检测桥臂中点电压V SW，并根据桥臂中点电压V SW确定斜率信号V SLP，斜率信号V SLP表示桥臂中点电压V SW的斜率；根据斜率信号V SLP与第一斜率阈值V TH1，确定第一脉冲信号slp1，第一脉冲信号slp1的脉冲长度用于指示斜率信号V SLP大于第一斜率阈值V TH1的时长tslp1；根据斜率信号V SLP与第二斜率阈值V TH2，确定第二脉冲信号slp2，第二脉冲信号slp2的脉冲长度用于指示斜率信号V SLP小于第二斜率阈值V TH2的时长tslp2，第二斜率阈值V TH2小于第一斜率阈值V TH1。
结合第一方面，在第一方面的某些实现方式中，电流阈值信号包括用于指示第一电流阈值ith1的第一电流阈值信号和用于指示第二电流阈值ith2的第二电流阈值信号，控制器还用于：根据第一脉冲信号slp1和第二脉冲信号slp2，确定第一电流阈值信号和第二电流阈值信号，其中，控制器具体用于：
确定第一初始电流阈值和第二初始电流阈值，第一初始电流阈值为正值，第二初始电流阈值为负值。
将第一脉冲信号的脉冲长度指示的时长tslp1与第一时间阈值Tth1进行比较，在第一脉冲信号的脉冲长度指示的时长tslp1大于第一时间阈值Tth1的情况下，减少第一初始电流阈值，以得到第一电流阈值ith1，在第一脉冲信号的脉冲长度指示的时长tslp1小于第一时间阈值Tth1的情况下，增大第一初始电流阈值，以得到第一电流阈值ith1。
将第二脉冲信号的脉冲长度指示的时长tslp2与第二时间阈值Tth2进行比较，在第二脉冲信号的脉冲长度指示的时长tslp2大于第二时间阈值Tth2的情况下，增大第二初始电流阈值，以得到第二电流阈值ith2，在第二脉冲信号的脉冲长度指示的时长tslp2小于第二时间阈值Tth2的情况下，减小第二初始电流阈值，以得到第二电流阈值ith2。
根据本申请的技术方案，通过检测桥臂中点电压的变化情况，确定脉冲信号的脉冲长度指示的时长，自适应调节电流阈值，进行容性保护，使得系统持续工作在感性模式下，满足开关的零电压开通，同时可以使系统工作在接近容性模式的状态，最大化利用增益的区间。
结合第一方面，在第一方面的另一种实现方式中，第一电信号为斜率信号V SLP，斜率信号V SLP表示桥臂中点电压V SW的斜率，斜率检测电路具体用于：
检测桥臂中点电压V SW，并根据桥臂中点电压V SW输出斜率信号V SLP。
结合第一方面，在第一方面的另一种实现方式中，电流阈值信号包括用于指示第一电流阈值ith1的第一电流阈值信号和用于指示第二电流阈值ith2的第二电流阈值信号，控制器还用于：根据斜率信号V SLP，确定第一电流阈值信号和第二电流阈值信号，其中，控制器具体用于：
确定第一初始电流阈值和第二初始电流阈值，第一初始电流阈值为正值，第二初始电流阈值为负值。
将斜率信号V SLP与第三斜率阈值V TH3进行比较，在斜率信号V SLP大于第三斜率阈值V TH1的情况下，减少第一初始电流阈值，以得到第一电流阈值ith1，在斜率信号V SLP小于第三斜率阈值V TH3的情况下，增大第一初始电流阈值，以得到第一电流阈值ith1。
将斜率信号V SLP与第四斜率阈值V TH4进行比较，在斜率信号V SLP大于第四斜率阈值V TH4的情况下，增大第二初始电流阈值，以得到第二电流阈值ith2，在斜率信号V SLP小于第四斜率阈值V TH4的情况下，减小第二初始电流阈值，以得到第二电流阈值ith2，第四斜率阈值V TH4小于第三斜率阈值V TH3。
根据本申请的技术方案，通过检测桥臂中点电压的变化情况，确定电压变化的速度，自适应调节电流阈值，进行容性保护，使得系统持续工作在感性模式下，满足开关的零电压开通，同时可以使系统工作在接近容性模式的状态，最大化利用增益的区间。
结合第一方面，在第一方面的实现方式中，第二电信号包括第一开关信号ic1和第二开关信号ic2，控制器还用于：检测变压器初级侧的谐振电流icr；根据谐振电流icr与电流阈值信号，输出第一开关信号ic1和第二开关信号ic2，所述电流阈值信号包括用于指示第一电流阈值ith1的第一电流阈值信号和用于指示第二电流阈值ith2的第二电流阈值信号，其中，控制器具体用于：
将谐振电流icr与第一电流阈值ith1进行比较，在谐振电流icr大于第一电流阈值ith1的情况下，确定第一开关信号ic1用于指示开通开关S1，在谐振电流icr小于第一电流阈值ith1的情况下，确定第一开关信号ic1用于指示关断开关S1；
将谐振电流icr与第二电流阈值ith2进行比较，在谐振电流icr大于第二电流阈值ith2的情况下，确定第二开关信号ic2用于指示关断开关S2，在谐振电流icr小于第二电流阈值ith2的情况下，确定第二开关信号ic2用于指示开通开关S2。
结合第一方面，在第一方面的实现方式中，控制器具体用于：根据第一开关信号ic1，确定第一控制信号DRV1，第一控制信号DRV1用于控制开关S1的通断；根据第二开关信号ic2，确定第二控制信号DRV2，二控制信号DRV2用于控制开关S2的通断。
作为一种可能的实现方式，控制器包括：斜率检测电路、阈值控制电路、电流比较电路和开关控制电路。
可选地，在本申请实施例中，斜率检测电路包括：检测电容Csw、检测电阻Rsw。
其中，检测电容Csw的第一端用于接收桥臂中点电压Vsw，检测电容Csw的第二端与检测电阻Rsw的第一端相连，检测电阻Rsw的第二端接地，其中，检测电阻Rsw的第一端用于输出斜率信号V SLP。
可选地，在本申请实施例中，斜率检测电路还包括：第一比较器CMP1、第二比较器CMP2和第一非门INV1。
其中，第一比较器CMP1的第一输入端和第二输入端分别用于接收斜率信号V SLP和第一斜率阈值V TH1信号，第一比较器CMP1的输出端用于输出第一脉冲信号slp1；第二比较器CMP2的第一输入端和第二输入端分别用于接收斜率信号V SLP和第二斜率阈值V TH2信号，第二比较器CMP2的输出端与第一非门INV1的输入端相连，第一非门INV1的输出端用于输出第二脉冲信号slp2。
可选地，在本申请实施例中，电流比较电路包括：第三比较器CMP3、第四比较器CMP4和第二非门INV2。
其中，第三比较器CMP3的第一输入端和第二输入端分别用于接收谐振电流icr和第一电流阈值ith1，第三比较器CMP3的输出端用于输出第一开关信号ic1；第四比较器CMP4的第一输入端和第二输入端分别用于接收谐振电流icr和第二电流阈值ith2，第四比较器CMP4的输出端与第二非门INV2的输入端相连，第二非门INV2的输出端用于输出第二开关信号ic2。
第二方面，提供了一种谐振变换系统的控制方法，谐振变换系统包括：控制器；谐振变换电路，包括高频斩波电路、谐振腔、变压器和整流滤波网络，高频斩波电路包括开关S1和S2，控制器用于通过控制开关S1和S2的通断，将输入高频斩波电路的直流电压转变为高频方波，谐振腔和变压器用于接收高频方波并将电能从变压器的初级侧耦合至次级侧，整流滤波网络用于将耦合至变压器的次级侧的交流电压转换为直流电压。该方法包括：控制器检测桥臂中点电压V SW，并根据桥臂中点电压V SW确定第一电信号，桥臂中点电压V SW为开关S1和S2相连的桥臂中点的电压，第一电信号与桥臂中点电压Vsw的斜率具有关联关系；控制器根据第一电信号确定电流阈值信号，电流阈值信号用于指示电流阈值；控制器检测变压器初级侧的谐振电流，并将谐振电流与电流阈值信号进行比较，确定第二电信号，第二电信号用于指示比较结果；控制器根据第二电信号控制开关S1或S2的通断，以使得系统工作在感性模式。
根据本申请的技术方案，通过检测桥臂中点电压的变化情况，自适应调节电流阈值，进行容性保护，使得系统持续工作在感性模式下，满足开关的零电压开通，同时可以使系统工作在接近容性模式的状态，最大化利用增益的区间。
结合第二方面，在第二方面的某些实现方式中，第一电信号包括第一脉冲信号slp1和第二脉冲信号slp2，控制器检测桥臂中点电压V SW，并根据桥臂中点电压V SW确定第一电信号，包括：
控制器检测桥臂中点电压V SW，并根据桥臂中点电压V SW确定斜率信号V SLP，斜率信号V SLP表示桥臂中点电压V SW的斜率；
控制器根据斜率信号V SLP与第一斜率阈值V TH1，确定第一脉冲信号slp1，第一脉冲信号slp1的脉冲长度用于指示斜率信号V SLP大于第一斜率阈值V TH1的时长tslp1；
控制器根据斜率信号V SLP与第二斜率阈值V TH2，确定第二脉冲信号slp2，第二脉冲信号slp2的脉冲长度用于指示斜率信号V SLP小于第二斜率阈值V TH2的时长tslp2，第二斜率阈值V TH2小于第一斜率阈值V TH1。
结合第二方面，在第二方面的某些实现方式中，电流阈值信号包括用于指示第一电流阈值ith1的第一电流阈值信号和用于指示第二电流阈值ith2的第二电流阈值信号，控制器根据第一电信号确定电流阈值信号，包括：控制器根据第一脉冲信号slp1和第二脉冲信号slp2，确定第一电流阈值信号和第二电流阈值信号。
其中，根据第一脉冲信号slp1和第二脉冲信号slp2，确定第一电流阈值信号和第二电流阈值信号，包括：
控制器确定第一初始电流阈值和第二初始电流阈值，第一初始电流阈值为正值，第二初始电流阈值为负值。
控制器将第一脉冲信号的脉冲长度指示的时长tslp1与第一时间阈值Tth1进行比较，在第一脉冲信号slp1的脉冲长度指示的时长tslp1大于第一时间阈值Tth1的情况下，减少 第一初始电流阈值，以得到第一电流阈值ith1，在第一脉冲信号slp1的脉冲长度指示的时长tslp1小于第一时间阈值Tth1的情况下，增大第一初始电流阈值，以得到第一电流阈值ith1。
控制器将第二脉冲信号的脉冲长度指示的时长tslp2与第二时间阈值Tth2进行比较，在第二脉冲信号slp2的脉冲长度指示的时长tslp2大于第二时间阈值Tth2的情况下，增大第二初始电流阈值，以得到第二电流阈值ith2，在第二脉冲信号slp2的脉冲长度指示的时长tslp2小于第二时间阈值Tth2的情况下，减小第二初始电流阈值，以得到第二电流阈值ith2。
根据本申请的技术方案，通过检测桥臂中点电压的变化情况，确定脉冲信号的脉冲长度指示的时长，自适应调节电流阈值，进行容性保护，使得系统持续工作在感性模式下，满足开关的零电压开通，同时可以使系统工作在接近容性模式的状态，最大化利用增益的区间。
结合第二方面，在第二方面的另一些实现方式中，第一电信号为斜率信号V SLP，斜率信号V SLP表示桥臂中点电压V SW的斜率，控制器检测桥臂中点电压V SW，并根据桥臂中点电压V SW确定第一电信号，包括：控制器检测桥臂中点电压V SW，并根据桥臂中点电压V SW确定斜率信号V SLP。
结合第二方面，在第二方面的另一些实现方式中，电流阈值信号包括用于指示第一电流阈值ith1的第一电流阈值信号和用于指示第二电流阈值ith2的第二电流阈值信号，控制器根据第一电信号确定电流阈值信号，包括：控制器根据斜率信号V SLP，确定第一电流阈值信号和第二电流阈值信号。
其中，阈值控制电路根据斜率信号V SLP，确定第一电流阈值信号和第二电流阈值信号，包括：
确定第一初始电流阈值和第二初始电流阈值，第一初始电流阈值为正值，第二初始电流阈值为负值。
控制器将斜率信号V SLP与第三斜率阈值V TH3进行比较，在斜率信号V SLP大于第三斜率阈值V TH3的情况下，减少第一初始电流阈值，以得到第一电流阈值ith1，在斜率信号V SLP小于第三斜率阈值V TH3的情况下，增大第一初始电流阈值，以得到第一电流阈值ith1。
控制器将斜率信号V SLP与第四斜率阈值V TH4进行比较，在斜率信号V SLP大于第四斜率阈值V TH4的情况下，增大第二初始电流阈值，以得到第二电流阈ith2，在斜率信号V SLP小于第四斜率阈值V TH4的情况下，减小第二初始电流阈值，以得到第二电流阈值ith2，第四斜率阈值V TH4小于第三斜率阈值V TH3。
根据本申请的技术方案，通过检测桥臂中点电压的变化情况，确定电压变化的速度，自适应调节电流阈值，进行容性保护，使得系统持续工作在感性模式下，满足开关的零电压开通，同时可以使系统工作在接近容性模式的状态，最大化利用增益的区间。
结合第二方面，在第二方面的实现方式中，第二电信号包括第一开关信号ic1和第二开关信号ic2，控制器检测变压器初级侧的谐振电流，并将谐振电流与电流阈值信号进行比较，确定第二电信号，包括：控制器检测变压器初级侧的谐振电流icr；控制器根据谐振电流icr与电流阈值信号，确定第一开关信号ic1和第二开关信号ic2，电流阈值信号包括用于指示第一电流阈值ith1的第一电流阈值信号和用于指示第二电流阈值ith2的第二电 流阈值信号。
其中，控制器根据谐振电流icr与电流阈值信号，确定第一开关信号ic1和第二开关信号ic2，包括：
控制器将谐振电流icr与第一电流阈值ith1进行比较，在谐振电流icr大于第一电流阈值ith1的情况下，第一开关信号ic1用于指示开通开关S1，在谐振电流icr小于第一电流阈值ith1的情况下，第一开关信号ic1用于指示关断开关S1，并确定第一开关信号ic1。
控制器将谐振电流icr与第二电流阈值ith2进行比较，在谐振电流icr大于第二电流阈值ith2的情况下，第二开关信号ic2用于指示关断开关S2，在谐振电流icr小于第二电流阈值ith2的情况下，第二开关信号ic2用于指示开通开关S2，并确定第二开关信号ic2。
结合第二方面，在第二方面的实现方式中，控制器根据第二电信号控制开关S1或S2的通断，包括：控制器根据第一开关信号ic1，确定第一控制信号DRV1，第一控制信号DRV1用于控制开关S1的通断；控制器根据第二开关信号ic2，确定第二控制信号DRV2，二控制信号DRV2用于控制开关S2的通断。
作为一种可能的实现方式，控制器包括：斜率检测电路、阈值控制电路、电流比较电路和开关控制电路。
附图说明
图1是DC-DC谐振变换器的示意图。
图2是半桥LLC谐振变换器拓扑200的示意图。
图3是LLC工作的感性区和容性区的示意图。
图4是本申请实施例提供的谐振变换系统的一例结构示意图。
图5是本申请实施例提供的斜率检测电路的一例结构示意图。
图6是本申请实施例提供的电流比较电路的一例结构示意图。
图7是本申请实施例提供的阈值控制电路和开关控制电路一例波形图。
图8是本申请实施例提供的谐振变换系统的另一例结构示意图。
图9是本申请实施例提供的斜率检测电路的另一例结构示意图。
图10是本申请实施例提供的阈值控制电路和开关制电路另一例波形图。
图11是本申请实施例提供的谐振变换系统控制方法的一例流程示意图。
图12是本申请实施例提供的谐振变换系统控制方法的另一例流程示意图。
图13是本申请实施例提供的控制设备的一例示意性框图。
具体实施方式
下面将结合附图，对本申请中的技术方案进行描述。
为便于理解本申请实施例，下面将结合图1和图2对本申请实施例的应用场景进行介绍。
图1是一种典型的DC-DC谐振变换器的示意图。如图1(a)所示，谐振变换器可以将直流输入经过高频斩波得到高频方波，然后经过谐振腔以及变压器实现调压以及软开关实现，最后通过整流滤波得到需要的直流输出。其中，如果高频斩波电路采用半桥电路，谐振腔采用LLC型，整流采用二极管全波整流则得到如图1(b)所示的常用的半桥LLC 谐振变换器拓扑100(后面简称半桥LLC)。该谐振变换器100包括高频斩波电路101，谐振腔102、变压器103和整流滤波网络104。其中，高频斩波电路101包括输入滤波电容C1，开关S1和S2(开关上的二极管为其体二极管，电容为其寄生电容)；谐振腔102包括谐振电感Lr和谐振电容Cr，该谐振电感Lr包括变压器的漏感和外加的电感，也可以全部集成在变压器103里面，变压器103可以是变压器Tr，其初级侧励磁电感为Lm；整流滤波网络104包括二极管D1和D2，以及输出滤波电容CO。
半桥LLC通常采用脉冲频率调制控制(pulse frequency modulation，PFM)，一个周期内，忽略死区时间，S1和S2个各导通50％时间，通过调节开关频率fs改变谐振腔的输入输出电压增益，实现对输出电压的调节。其谐振腔依据变压器的励磁电感Lm是否参与谐振，得到两个谐振频率如下：
Figure PCTCN2022087628-appb-000001
Figure PCTCN2022087628-appb-000002
其中，公式(1)表示变压器的励磁电感Lm不参与谐振时的谐振频率，公式(2)表示变压器的励磁电感Lm参与谐振时的谐振频率。根据谐振频率可以将其增益曲线划分成感性区域和容性区域，如图2所示，fm为增益峰值点的频率，也是容性区域和感性区域分界点，当工作在fr时，电压增益恒定为1。为了实现S1和S2的零电压开通，半桥LLC需要工作在感性区域；若工作在容性区域，ZVS无法实现，还会有S1和S2直通的风险。为避免进入容性模式，传统通常采用限频法，限制最低的工作频率，使得工作频率大于fm，但是在一些异常条件下，如输出短路、过载等，系统Q值增大后，fm值增大，会导致限频法失效而进入容性区域工作。
在面对上述技术问题时，现有技术一般采用以下处理方法：
(1)在传统半桥LLC谐振变换器拓扑中引入斜率检测电路、延迟振荡器和开关电路。如图3(a)所示，在正常状态下，S1或S2关断后，SW电压将下降或者上升，以S1为例，当其导通时，SW点电压等于输入电压Vin，当S1关断时，SW点电压从Vin下降到0，然后开通S2实现零电压开通。但是若系统进入容性模式，S1关断后，SW点电压将不发生变化。因此，现有技术中可以通过斜率检测电路检测S1关断后，SW点电压是否变化来判断电路是否进入容性模式。判断进入容性模式后，延迟振荡器进行延时，待电流极性正常或振荡器延时时间到后，再打开开关管；然后在确保安全的条件下逐步提高开关频率，从而避免长时间处于容性区造成开关管损坏。但是在该技术中，实际上在整个系统已经进入容性模式工作才动作，电路存在损坏的风险，同时，由于振荡器延时时间为一预设的固定值，在振荡器延时时间结束后，可能SW点电压并未降为零，导致无法实现开关管的零电压开通。
(2)在传统半桥LLC谐振变换器拓扑中引入电流比较电路和开关控制电路。其工作原理如图3(b)所示，在感性模式下，S1或者S2关断时，谐振电流应该大于某一阈值(正阈值)或者小于某一阈值(负阈值)。以S1为例，S1关断时，谐振电流应该大于某一阈值(正阈值)，若关断时电流小于这一阈值，如图3(b)中t0时刻，系统将进入容性区域。该技术通过谐振电流与这一阈值的比较判断容性模式，当容性模式触发时，关闭S1 和S2的若干个周期，如图t0到t1期间，等到满足开通条件后(例如，t 1时刻)才重新开启S1或S2。但是，在该技术中，在关闭S1和S2的若干个周期里，系统没有带载能力，除此之外，仍旧是在整个系统已经进入容性模式工作才出发保护，电路存在损坏的风险。
(3)与上述(2)中原理一样通过谐振电流与阈值比较进行控制，不同的是该技术中控制谐振电流绝对值小于阈值的时候，直接关断S1或者S2的，因此系统可以在接近容性模式区域工作，而且由于阈值的限制不会进入容性模式。如图3(c)所示，原本S1应该在t1时刻关断，但是t0时刻，谐振电流icr低于电流阈值，S1会直接关断，从而防止进入容性模式。但在实际应用中，系统在不同工作状态下，电流变化的速度不一样，固定的阈值无法得到最优的控制，阈值过大导致电压增益裕量的浪费，阈值过小不能保障ZVS的可靠实现。
基于上述原因，本申请提供了一种谐振变换系统，使得系统持续工作中在感性模式，保证开关的零电压开通，同时可以工作在接近容性模式的状态，最大化利用增益的区间。
图4示出了本申请实施例提供的变换系统的一例结构示意图。如图4所示，谐振变换系统300包括谐振变换电路310和控制器320。其中，控制器320包括斜率检测电路、阈值控制电路、电流比较电路和开关控制电路，谐振变换电路310与图1(b)中所示的谐振变换器100结构基本相同，在此不再赘述。
应理解，谐振变换电路310中的开关S1与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)等材料制成的金属氧化物半导体场效应晶体管(metal-oxide-semiconductor field-effect transistor，MOSFET)或绝缘栅双极性晶体管(insulated gate bipolar transistor，IGBT)，本申请不对其进行限定。
在本申请实施例中，控制器可以通过斜率检测电路检测桥臂中点的电压，并通过阈值控制电路根据桥臂的中点电压变化信号脉冲的脉冲长度指示的时间长度自适应调节电流阈值，最后通过电流比较电路控制开关的关断，限制频率不会进入容性区域，使得系统可以接近容性区域工作，最大化利用增益的区间。
下面将结合图5、图6和图7对该实施例进行详细说明。
图5示出了本申请实施例提供的斜率检测电路的一例结构示意图。如图5(a)所示，斜率检测电路包括检测电容Csw、检测电阻Rsw、两个比较器CMP1和CMP2，非门INV1，其工作波形图如图(b)所示。开关S1关断到S2导通，桥臂中点电压会从Vin下降；对应地，当S2关断到S1导通，桥臂中点电压会从0开始上升。因此，根据检测电容Csw和检测电阻Rsw可以检测桥臂中点的电压变化。其变化斜率Vslp如公式(3)所示：
Figure PCTCN2022087628-appb-000003
当Vslp大于V TH1时，slp1输出置1，当Vslp小于V TH2时，slp2输出置1，因此通过slp1和slp2可以检测得到SW处斜率的变化，其中，本申请实施例对速度阈值V TH1和V TH2的确定方式不做限定，例如，可以根据实际测试、仿真模拟或理论计算等方式。作为一种可能的实现方式，可以根据谐振电流的大小，结合谐振电容，可以得到dvsw/dt，根据斜率采样阻容参数即可得到V TH1和V TH2阈值的大小，其中V TH2小于V TH1，可选地，V TH1可以为正值，V TH2可以为一负值。
图6示出了本申请实施例提供的电流比较电路的一例结构示意图。如图6(a)所示，电流比较电路包括两个比较器CMP3和CMP4以及非门INV2，其波形图如图6(b)所示。icr为谐振电容Cr电流的采样电流，当电流低于阈值ith1时，ic1输出由1置0，当icr大于ith2时，ic2输出由1置0。电流比较电路用于容性模式的判断，当S1还导通时，若ic1输出由1置0，则表示容性模式触发，然后关闭S1，从而防止系统进入容性模式；同理，当S2导通时，若ic2输出由1置0，则表示容性模式触发，然后关闭S2。其中，阈值ith1和ith2由阈值控制电路提供。
图7示出了本申请实施例提供的阈值控制电路和开关控制电路波形图，其中，第一电流阈值ith1和第二电流阈值ith2分别由阈值控制电路确定的第一初始电流阈值和第二初始电流阈值经调解后得到，第一初始电流阈值和第一初始电流阈值是根据电路设计好的预设值。
可选地，第一初始电流阈值可以为一个正值，第二初始电流阈值可以为一个负值，参照上述V TH1和V TH2的确定方式，第一初始电流阈值和第二初始电流阈值可以由实际测试、仿真模拟或理论计算等方式确定。
在正常感性模式，当DRV 1和DRV 2关断时刻，icr都大于阈值ith1和ith2，因此不会触发容性模式保护。如图7(a)所示，t 0时刻，DRV 1关断，此时icr仍大于ith1，容性模式未触发；t 1时刻，slp2由1变成0，表示Vsw电压从Vin减小到0，此时导通S2可以实现ZVS。同理，在t 2时刻，DRV 2关断，此时icr仍大于ith2，容性模式未触发；t 3时刻，slp1由1变成0，表示Vsw电压从Vin减小到0，此时导通S1可以实现ZVS。
图7(b)示出了接近容性模式下的阈值控制电路和开关控制电路波形图。当开关S1和S2的开关频率不断降低到接近谐振频率fm时，即接近容性区域时，如图7(b)所示，在t 3时刻谐振电流icr大于ith2，ic2由1变0，此时关断S2，则S1和S2的开关频率将被限制而不会继续降低而进入容性区域。S2关断后，谐振电流icr将对S1电容进行放电，对S2电容进行充电，sw点电压上升，通过斜率检测电路得到slp1。
阈值控制电路可以通过检测slp1(或slp2)进行电流阈值ith1以及ith2的自适应调节，以保证系统持续工作在感性模式，满足开关的零电压开通，同时可以工作在接近容性模式的状态，最大化利用增益区间。
例如，图7(c)中t 3时刻，若ith2设置太小(绝对值)，sw点的电压Vsw变化缓慢，slp1脉冲长度指示的时间变长，不能充分利用增益区间。所以阈值控制电路可以检测slp1脉冲长度指示的时间长度tslp1(t 4-t 3)，当tslp1大于时间阈值Tth1，判断为阈值ith2(绝对值)设置太小，因此增加阈值ith1和ith2(绝对值)。如图7(c)中t 4时刻，判断tslp1(t 4-t 3)大于时间阈值Tth1，控制电流阈值ith1和ith2(绝对值)增大，t 6时刻icr低于电流阈值ith1时关断，由于ith1增大了，Vsw变化速度加快，tslp2(t 7-t 6)减小。
其中，时间阈值Tth1是固定的预设值，其可以由实际测试、仿真模拟或理论计算等方式确定，本申请对其确定方式不作限定。下文中的时间阈值Tth2与此同理，在此不再赘述。
又例如，图7(d)中t 3时刻，若ith2设置太大(绝对值)，sw点的电压Vsw变化太快，slp2脉冲长度指示的时间很短，系统可能进入容性模式，不利于开关零电压开通的实现。所以阈值控制电路检测slp2脉冲长度指示的时间长度tslp2，当脉冲长度指示的时间 tslp2小于时间阈值Tth2，判断为电流阈值设置太小，因此减小电流阈值ith1和ith2(绝对值)。如图7(d)中t 4时刻，判断tslp2(t 4-t 3)小于时间阈值Tth2，控制电流阈值ith1和ith2(绝对值)增大，t 6时刻icr低于电流阈值ith1时关断，由于ith1减小了，Vsw变化速度变慢，tslp2(t 7-t 6)增大，系统可以在接近容性模式下工作而不会进入容性区域。
根据本申请的技术方案，控制器可以通过斜率检测电路检测桥臂中点的电压，并通过阈值控制电路根据桥臂的中点电压自适应调节电流阈值，最后通过电流比较电路控制开关的关断，限制频率不会进入容性区域，使得系统可以持续工作在感性区域，实现零电压开通，并最大化利用增益的区间。
图8示出了本申请实施例提供的谐振变换系统的另一例结构示意图。如图8所示，谐振变换系统400包括谐振变换电路410和控制器420，其结构与图4中所示的谐振变换系统300基本相同，在此不再赘述。
在该实施例中，控制器可以通过斜率检测电路检测桥臂中点的电压，并通过阈值控制电路根据桥臂的中点电压变化幅值自适应调节电流阈值。因此，如图9所示，该实施例中，斜率检测电路不再将slp1和slp2信号输送给阈值控制电路，仅提供给开关控制电路进行死区时间控制，而需要将Vslp信号输出到阈值控制模块，用于ith1和ith2的判断。电流比较电路与上述实施例中相同，具体请参照图6中的描述。
图10示出了本申请实施例提供的阈值控制电路和开关控制电路波形图。如图10所示，slp1和slp2同样根据Vslp和速度阈值V TH1和V TH2比较得到，但是仅仅用于死区的控制。例如，图中t 1时刻，slp2由1变成0，代表Vsw电压从Vin降低到0，此时死区时间结束，可以导通S2。
应理解，与上述实施例相同，第一电流阈值ith1和第二电流阈值ith2分别由阈值控制电路确定的第一初始电流阈值和第二初始电流阈值经调解后得到，第一初始电流阈值和第一初始电流阈值是根据电路设计好的预设值。
还应理解，本申请实施例对速度阈值V TH3和V TH4的确定方式不做限定，例如，可以根据实际测试、仿真模拟或理论计算等方式。作为一种可能的实现方式，可以根据谐振电流的大小，结合谐振电容，可以得到dvsw/dt，根据斜率采样阻容参数即可得到V TH3和V TH4阈值的大小，其中V TH4小于V TH3，优选地，V TH3可以为正值，V TH4可以为一负值。
在本实施例中，电流阈值ith1和ith2的自适应调节通过Vslp电压幅值与阈值V TH3和V TH4进行控制。根据上述公式3可知，开关关断时刻，icr越大，Vsw变化速度越快，Vslp的电压幅值越大。如图10中t 3到t 4时间内，Vslp均低于V TH3，表示vsw变化速度变化过慢，这可能导致不能充分利用增益区间。因此可以增加电流阈值ith1和ith2(绝对值)，t 6时刻icr低于阈值ith1时关断，由于ith1增大了，Vsw变化速度加快，Vslp电压提高，直到大于阈值V TH3(绝对值)，这样，可以使得系统可以工作在接近容性模式的状态，最大化利用增益区间。同理，若Vslp电压大于另一阈值(例如，V TH5和V TH6)，表示Vsw变化速度变化过快，这可能导致系统进入容性模式，不利于开关零电压开通的实现。因此可以减小电流阈值ith1和ith2(绝对值)，在电流阈值ith1和ith2(绝对值)减小后，Vsw变化速度变慢，这样，可以使得系统持续工作在感性模式，满足开关的零电压开通。
根据本申请的技术方案，控制器可以通过斜率检测电路检测桥臂中点的电压，并通过阈值控制电路根据桥臂的中点电压自适应调节电流阈值，最后通过电流比较电路控制开关 的关断，限制频率不会进入容性区域，使得系统可以接近容性区域工作，实现零电压开通，并最大化利用增益的区间。
图11示出了本申请实施例提供的谐振系统的控制方法的一例示意性流程图。
在本申请实施例中，控制器可以包括：斜率检测电路、阈值控制电路、电流比较电路和开关控制电路。以下为便于更清楚地理解本申请的技术方案将各部分的动作分别描述，但其不应作为对本申请技术方案的限定，其中，斜率检测电路、阈值控制电路、电流比较电路和开关控制电路所执行的步骤或操作均可以用控制器执行。
S510，斜率检测电路检测桥臂中点电压V SW，并根据桥臂中点电压V SW输出斜率信号V SLP。
具体地，上述斜率检测电路可以包括：检测电容Csw、检测电阻Rsw。检测电容Csw的第一端用于接收桥臂中点电压Vsw，检测电容Csw的第二端与检测电阻Rsw的第一端相连，检测电阻Rsw的第二端接地，其中，检测电阻Rsw的第一端用于输出斜率信号V SLP。
当得到斜率信号V SLP后，斜率检测电路可以执行步骤S520，斜率检测电路根据斜率斜率信号V SLP输出脉冲信号slp1和slp2。
其中，该斜率检测电路还包括：第一比较器CMP1、第二比较器CMP2和第一非门INV1。第一比较器CMP1的第一输入端和第二输入端分别用于接收斜率信号V SLP和第一斜率阈值V TH1信号，第一比较器CMP1的输出端用于输出第一脉冲信号slp1；第二比较器CMP2的第一输入端和第二输入端分别用于接收斜率信号V SLP和第二斜率阈值V TH2信号，第二比较器CMP2的输出端与第一非门INV1的输入端相连，第一非门INV1的输出端用于输出第二脉冲信号slp2。
在本申请实施例中，速度阈值V TH1和V TH2可以由多种确定方式，例如，可以根据实际测试、仿真模拟或理论计算等方式。作为一种可能的实现方式，可以根据谐振电流的大小，结合谐振电容，可以得到dvsw/dt，根据斜率采样阻容参数即可得到V TH1和V TH2阈值的大小，其中V TH2小于V TH1，优选地，V TH1可以为正值，V TH2可以为一负值。
阈值控制电路可以接收斜率检测电路输出的第一脉冲信号slp1和第一脉冲信号slp2，并执行步骤S530，根据脉冲信号slp1和slp2输出电流阈值信号ith1和ith2。
具体地，第一电流阈值ith1和第二电流阈值ith2分别由阈值控制电路确定的第一初始电流阈值和第二初始电流阈值经调节后得到，第一初始电流阈值和第二初始电流阈值是根据电路设计好的预设值。
优选地，第一初始电流阈值可以为一个正值，第二初始电流阈值可以为一个负值，参照上述V TH1和V TH2的确定方式，第一初始电流阈值和第二初始电流阈值可以由实际测试、仿真模拟或理论计算等方式确定。
阈值控制电路将第一脉冲信号的脉冲长度指示的时长tslp1与第一时间阈值Tth1进行比较，在第一脉冲信号的脉冲长度指示的时长tslp1大于第一时间阈值Tth1的情况下，减少第一初始电流阈值，以得到第一电流阈值ith1，在第一脉冲信号的脉冲长度指示的时长tslp1小于第一时间阈值Tth1的情况下，增大第一初始电流阈值，以得到第一电流阈值ith1。
其中，时间阈值Tth1是固定的预设值，其可以由实际测试、仿真模拟或理论计算等方式确定，本申请对其确定方式不作限定。下文中的时间阈值Tth2与此同理，在此不再赘述。
对应地，阈值控制电路将第二脉冲信号的脉冲长度指示的时长tslp2与第二时间阈值Tth2进行比较，在第二脉冲信号的脉冲长度指示的时长tslp2大于第二时间阈值Tth2的情况下，增大第二初始电流阈值，以得到第二电流阈值ith2，在第二脉冲信号的脉冲长度指示的时长tslp2小于第二时间阈值Tth2的情况下，减小第二初始电流阈值，以得到第二电流阈值ith2。
在阈值控制电路输出第一电流阈值ith1和第二电流阈值ith2后，电流比较可以接收第一电流阈值ith1和第二电流阈值ith2，并执行步骤S540，检测谐振电流，并将谐振电流与第一电流阈值ith1和第二电流阈值ith2进行比较，输出开关信号ic1和ic2.
具体地，电流比较电路可以包括：第三比较器CMP3、第四比较器CMP4和第二非门INV2。第三比较器CMP3的第一输入端和第二输入端分别用于接收谐振电流icr和第一电流阈值ith1，第三比较器CMP3的输出端用于输出第一开关信号ic1；第四比较器CMP4的第一输入端和第二输入端分别用于接收谐振电流icr和第二电流阈值ith2，第四比较器CMP4的输出端与第二非门INV2的输入端相连，第二非门INV2的输出端用于输出第二开关信号ic2。
S550，开关控制电路根据第一开关信号ic1和第二开关信号ic2，输出控制信号DRV1给开关S1，输出控制信号DRV2给开关S2，以控制开关S1和S2的通断。
根据本申请的技术方案，谐振控制器可以通过斜率检测电路检测桥臂中点的电压，并通过阈值控制电路根据桥臂的中点电压自适应调节电流阈值，最后通过电流比较电路控制开关的关断，限制频率不会进入容性区域，使得系统可以持续工作在感性区域，实现零电压开通，并最大化利用增益的区间。
图12示出了本申请实施例提供的谐振系统的控制方法的另一例示意性流程图。
在本申请实施例中，控制器可以包括：斜率检测电路、阈值控制电路、电流比较电路和开关控制电路。以下为便于更清楚地理解本申请的技术方案将各部分的动作分别描述，但其不应作为对本申请技术方案的限定，其中，斜率检测电路、阈值控制电路、电流比较电路和开关控制电路所执行的步骤或操作均可以用控制器执行。
在该实施例中，谐振控制器可以通过斜率检测电路检测桥臂中点的电压，并通过阈值控制电路根据桥臂的中点电压变化幅值自适应调节电流阈值。因此，该实施例中，斜率检测电路不再将slp1和slp2信号输送给阈值控制电路，而需要将Vslp信号输出到阈值控制模块，用于ith1和ith2的判断。
S610，该步骤与图11中所示的步骤S510一致，具体请参照图11中的描述，在此不再赘述。
S620，阈值控制电路根据斜率信号Vslp输出电流阈值信号ith1和ith2。
具体地，第一电流阈值ith1和第二电流阈值ith2分别由阈值控制电路确定的第一初始电流阈值和第二初始电流阈值经调节后得到，第一初始电流阈值和第二初始电流阈值是根据电路设计好的预设值。
优选地，第一初始电流阈值可以为一个正值，第二初始电流阈值可以为一个负值，参照上述V TH1和V TH2的确定方式，第一初始电流阈值和第二初始电流阈值可以由实际测试、仿真模拟或理论计算等方式确定。
阈值控制电路将斜率信号V SLP与第三斜率阈值V TH3进行比较，在斜率信号V SLP大于 第三斜率阈值V TH3的情况下，减少第一初始电流阈值，以得到第一电流阈值ith1，在斜率信号V SLP小于第三斜率阈值V TH3的情况下，增大第一初始电流阈值，以得到第一电流阈值ith1。
对应的，阈值控制电路将斜率信号V SLP与第四斜率阈值V TH4进行比较，在斜率信号V SLP大于第四斜率阈值V TH4的情况下，增大第二初始电流阈值，以得到第二电流阈ith2，在斜率信号V SLP小于第四斜率阈值V TH4的情况下，减小第二初始电流阈值，以得到第二电流阈值ith2。
在本申请实施例中，速度阈值V TH3和V TH4可以由多种确定方式，例如，可以根据实际测试、仿真模拟或理论计算等方式。作为一种可能的实现方式，可以与上述V TH1和V TH2的确定方式相同，根据谐振电流的大小，结合谐振电容，可以得到dvsw/dt，根据斜率采样阻容参数即可得到V TH3和V TH4阈值的大小，其中V TH4小于V TH3，可选地，V TH3可以为正值，V TH4可以为一负值。
在得到第一电流阈值ith1和第二电流阈值ith2后，电流比较电路可以执行步骤S630，该步骤与图11中步骤S540相同，电流比较电路可以检测谐振电流，并将谐振电流与电流阈值信号ith1和ith2进行比较，输出开关信号ic1和ic2。从而，开关电路可以继续执行步骤S640，该步骤与图11中的步骤S550相同，在此不再赘述。
根据本申请的技术方案，谐振控制器可以通过斜率检测电路检测桥臂中点的电压，并通过阈值控制电路根据桥臂的中点电压自适应调节电流阈值，最后通过电流比较电路控制开关的关断，限制频率不会进入容性区域，使得系统可以持续工作在感性区域，实现零电压开通，并最大化利用增益的区间。
图13示出了本申请实施例提供的控制设备的一例示意性结构框图。该控制设备包括处理器710、通信接口720。可选地，该控制设备还可以包括存储器730。可选地，存储器730可以包括于处理器710中。其中，处理器710、通信接口720和存储器730通过内部连接通路互相通信，存储器730用于存储指令，处理器710用于执行存储器730存储的指令，以实现本申请实施例提供的控制方法。
可选地，该控制设备可以用于执行图4中的控制器320或图8中控制器420的功能，其中控制器320和控制器420包括斜率检测电路、阈值控制电路、电流比较电路和开关控制电路。
可选地，该控制设备还可以用于执行图11或图12中所展示的控制方法。
在本说明书中使用的术语“部件”、“模块”、“系统”等用于表示计算机相关的实体、硬件、固件、硬件和软件的组合、软件、或执行中的软件。例如，部件可以是但不限于，在处理器上运行的进程、处理器、对象、可执行文件、执行线程、程序和/或计算机。通过图示，在计算设备上运行的应用和计算设备都可以是部件。一个或多个部件可驻留在进程和/或执行线程中，部件可位于一个计算机上和/或分布在2个或更多个计算机之间。此外，这些部件可从在上面存储有各种数据结构的各种计算机可读介质执行。部件可例如根据具有一个或多个数据分组(例如来自与本地系统、分布式系统和/或网络间的另一部件交互的二个部件的数据，例如通过信号与其它系统交互的互联网)的信号通过本地和/或远程进程来通信。
本领域普通技术人员可以意识到，结合本文中所公开的实施例描述的各示例的单元及 算法步骤，能够以电子硬件、或者计算机软件和电子硬件的结合来实现。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本申请的范围。
所属领域的技术人员可以清楚地了解到，为描述的方便和简洁，上述描述的系统、装置和单元的具体工作过程，可以参考前述方法实施例中的对应过程，在此不再赘述。
在本申请所提供的几个实施例中，应该理解到，所揭露的系统、装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合或通信连接，可以是电性，机械或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本申请各个实施例中的各功能单元可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中。
所述功能如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本申请的技术方案本质上或者说对现有技术做出贡献的部分或者该技术方案的部分可以以软件产品的形式体现出来，该计算机软件产品存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)执行本申请各个实施例所述方法的全部或部分步骤。而前述的存储介质包括：U盘、移动硬盘、只读存储器(read-only memory，ROM)、随机存取存储器(random access memory，RAM)、磁碟或者光盘等各种可以存储程序代码的介质。
以上所述，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所述权利要求的保护范围为准。

Claims (13)

  1. 一种谐振变换系统，其特征在于，包括：
    控制器；
    谐振变换电路，包括高频斩波电路、谐振腔、变压器和整流滤波网络，所述高频斩波电路包括开关S1和S2，所述控制器用于通过控制所述开关S1和S2的通断，将输入所述高频斩波电路的直流电压转变为高频方波，所述谐振腔和所述变压器用于接收所述高频方波并将电能从所述变压器的初级侧耦合至次级侧，所述整流滤波网络用于将耦合至所述变压器的次级侧的交流电压转换为直流电压；
    所述控制器还用于：
    检测桥臂中点电压V SW，并根据所述桥臂中点电压V SW确定第一电信号，所述桥臂中点电压V SW为所述开关S1和S2相连的桥臂中点的电压，所述第一电信号与所述桥臂中点电压Vsw的斜率具有关联关系；
    根据所述第一电信号确定电流阈值信号，所述电流阈值信号用于指示电流阈值；
    检测所述变压器初级侧的谐振电流，并将所述谐振电流与所述电流阈值信号进行比较，确定第二电信号，所述第二电信号用于指示比较结果；
    根据所述第二电信号控制所述开关S1或S2的通断，以使得所述系统工作在感性模式。
  2. 根据权利要求1所述的系统，其特征在于，所述第一电信号包括第一脉冲信号slp1和第二脉冲信号slp2，所述控制器具体用于：
    检测所述桥臂中点电压V SW，并根据所述桥臂中点电压V SW确定斜率信号V SLP，所述斜率信号V SLP表示所述桥臂中点电压V SW的斜率；
    根据所述斜率信号V SLP与第一斜率阈值V TH1，确定所述第一脉冲信号slp1，所述第一脉冲信号slp1的脉冲长度用于指示所述斜率信号V SLP大于所述第一斜率阈值V TH1的时长tslp1；
    根据所述斜率信号V SLP与第二斜率阈值V TH2，确定所述第二脉冲信号slp2，所述第二脉冲信号slp2的脉冲长度用于指示所述斜率信号V SLP小于所述第二斜率阈值V TH2的时长tslp2，所述第二斜率阈值V TH2小于所述第一斜率阈值V TH1。
  3. 根据权利要求2所述的系统，其特征在于，所述电流阈值信号包括用于指示第一电流阈值ith1的第一电流阈值信号和用于指示第二电流阈值ith2的第二电流阈值信号，所述控制器还用于：
    根据所述第一脉冲信号slp1和所述第二脉冲信号slp2，确定所述第一电流阈值信号和所述第二电流阈值信号，其中，所述控制器具体用于：
    确定第一初始电流阈值和第二初始电流阈值，所述第一初始电流阈值为正值，所述第二初始电流阈值为负值；
    将所述第一脉冲信号slp1的脉冲长度指示的时长tslp1与第一时间阈值Tth1进行比较，在所述第一脉冲信号slp1的脉冲长度指示的时长tslp1大于所述第一时间阈值Tth1的情况下，减少所述第一初始电流阈值，以得到所述第一电流阈值ith1，在所述第一脉冲信号slp1的脉冲长度指示的时长tslp1小于所述第一时间阈值Tth1的情况下，增大所述第一 初始电流阈值，以得到所述第一电流阈值ith1；
    将所述第二脉冲信号slp2的脉冲长度指示的时长tslp2与所述第二时间阈值Tth2进行比较，在所述第二脉冲信号slp2的脉冲长度指示的时长tslp2大于所述第二时间阈值Tth2的情况下，增大所述第二初始电流阈值，以得到所述第二电流阈值ith2，在所述第二脉冲信号slp2的脉冲长度指示的时长tslp2小于所述第二时间阈值Tth2的情况下，减小所述第二初始电流阈值，以得到所述第二电流阈值ith2。
  4. 根据权利要求1所述的系统，其特征在于，所述第一电信号为斜率信号V SLP，所述斜率信号V SLP表示所述桥臂中点电压V SW的斜率，所述控制器具体用于：
    检测所述桥臂中点电压V SW，并根据所述桥臂中点电压V SW确定所述斜率信号V SLP。
  5. 根据权利要求4所述的系统，其特征在于，所述电流阈值信号包括用于指示第一电流阈值ith1的第一电流阈值信号和用于指示第二电流阈值ith2的第二电流阈值信号，所述控制器还用于：
    根据所述斜率信号V SLP，确定所述第一电流阈值信号和所述第二电流阈值信号，其中，所述控制器具体用于：
    确定第一初始电流阈值和第二初始电流阈值，所述第一初始电流阈值为正值，所述第二初始电流阈值为负值；
    将所述斜率信号V SLP与第三斜率阈值V TH3进行比较，在所述斜率信号V SLP大于所述第三斜率阈值V TH1的情况下，减少所述第一初始电流阈值，以得到所述第一电流阈值ith1，在所述斜率信号V SLP小于所述第三斜率阈值V TH3的情况下，增大所述第一初始电流阈值，以得到所述第一电流阈值ith1；
    将所述斜率信号V SLP与第四斜率阈值V TH4进行比较，在所述斜率信号V SLP大于所述第四斜率阈值V TH4的情况下，增大所述第二初始电流阈值，以得到所述第二电流阈值ith2，在所述斜率信号V SLP小于所述第四斜率阈值V TH4的情况下，减小所述第二初始电流阈值，以得到所述第二电流阈值ith2，所述第四斜率阈值V TH4小于所述第三斜率阈值V TH3。
  6. 根据权利要求1至5中任一项所述的系统，其特征在于，所述第二电信号包括第一开关信号ic1和第二开关信号ic2，所述控制器还用于：
    检测所述变压器初级侧的谐振电流icr；
    根据所述谐振电流icr与所述电流阈值信号，确定所述第一开关信号ic1和所述第二开关信号ic2，所述电流阈值信号包括用于指示第一电流阈值ith1的第一电流阈值信号和用于指示第二电流阈值ith2的第二电流阈值信号，其中，所述控制器具体用于：
    将所述谐振电流icr与所述第一电流阈值ith1进行比较，在所述谐振电流icr大于所述第一电流阈值ith1的情况下，确定所述第一开关信号ic1用于指示开通所述开关S1，在所述谐振电流icr小于所述第一电流阈值ith1的情况下，确定所述第一开关信号ic1用于指示关断所述开关S1；
    将所述谐振电流icr与所述第二电流阈值ith2进行比较，在所述谐振电流icr大于所述第二电流阈值ith2的情况下，确定所述第二开关信号ic2用于指示关断所述开关S2，在所述谐振电流icr小于所述第二电流阈值ith2的情况下，确定所述第二开关信号ic2用于指示开通所述开关S2。
  7. 根据权利要求6所述的系统，其特征在于，所述控制器具体用于：
    根据所述第一开关信号ic1，确定第一控制信号DRV1，所述第一控制信号DRV1用于控制所述开关S1的通断；
    根据所述第二开关信号ic2，确定第二控制信号DRV2，所述二控制信号DRV2用于控制所述开关S2的通断。
  8. 根据权利要求1至7中任一项所述的系统，其特征在于，所述控制器包括：
    斜率检测电路、阈值控制电路、电流比较电路和开关控制电路。
  9. 根据权利要求8所述的系统，其特征在于，所述斜率检测电路包括：
    检测电容Csw、检测电阻Rsw；
    所述检测电容Csw的第一端用于接收所述桥臂中点电压Vsw，所述检测电容Csw的第二端与所述检测电阻Rsw的第一端相连，所述检测电阻Rsw的第二端接地，其中，所述检测电阻Rsw的第一端用于输出所述斜率信号V SLP。
  10. 根据权利要求8所述的系统，其特征在于，
    所述斜率检测电路还包括：第一比较器CMP1、第二比较器CMP2和第一非门INV1；
    所述第一比较器CMP1的第一输入端和第二输入端分别用于接收所述斜率信号V SLP和所述第一斜率阈值V TH1信号，所述第一比较器CMP1的输出端用于输出所述第一脉冲信号slp1；
    所述第二比较器CMP2的第一输入端和第二输入端分别用于接收所述斜率信号V SLP和所述第二斜率阈值V TH2信号，所述第二比较器CMP2的输出端与所述第一非门INV1的输入端相连，所述第一非门INV1的输出端用于输出所述第二脉冲信号slp2。
  11. 根据权利要求8所述的系统，其特征在于，所述电流比较电路包括：
    第三比较器CMP3、第四比较器CMP4和第二非门INV2；
    所述第三比较器CMP3的第一输入端和第二输入端分别用于接收所述谐振电流icr和所述第一电流阈值ith1，所述第三比较器CMP3的输出端用于输出所述第一开关信号ic1；
    所述第四比较器CMP4的第一输入端和第二输入端分别用于接收所述谐振电流icr和所述第二电流阈值ith2，所述第四比较器CMP4的输出端与所述第二非门INV2的输入端相连，所述第二非门INV2的输出端用于输出所述第二开关信号ic2。
  12. 一种谐振变换系统的控制方法，其特征在于，所述谐振变换系统包括：
    控制器；
    谐振变换电路，包括高频斩波电路、谐振腔、变压器和整流滤波网络，所述高频斩波电路包括开关S1和S2，所述控制器用于通过控制所述开关S1和S2的通断，将输入所述高频斩波电路的直流电压转变为高频方波，所述谐振腔和所述变压器用于接收所述高频方波并将电能从所述变压器的初级侧耦合至次级侧，所述整流滤波网络用于将耦合至所述变压器的次级侧的交流电压转换为直流电压；
    所述方法包括：
    所述控制器检测桥臂中点电压V SW，并根据所述桥臂中点电压V SW确定第一电信号，所述桥臂中点电压V SW为所述开关S1和S2相连的桥臂中点的电压，所述第一电信号与所述桥臂中点电压Vsw的斜率具有关联关系；
    所述控制器根据所述第一电信号确定电流阈值信号，所述电流阈值信号用于指示电流阈值；
    所述控制器检测所述变压器初级侧的谐振电流，并将所述谐振电流与所述电流阈值信号进行比较，确定第二电信号，所述第二电信号用于指示比较结果；
    所述控制器根据所述第二电信号控制所述开关S1或S2的通断，以使得所述系统工作在感性模式。
  13. 根据权利要求12所述的方法，其特征在于，所述第一电信号包括第一脉冲信号slp1和第二脉冲信号slp2，
    所述控制器检测桥臂中点电压V SW，并根据所述桥臂中点电压V SW确定第一电信号，包括：
    所述控制器检测所述桥臂中点电压V SW，并根据所述桥臂中点电压V SW确定斜率信号V SLP，所述斜率信号V SLP表示所述桥臂中点电压V SW的斜率；
    所述控制器根据所述斜率信号V SLP与第一斜率阈值V TH1，确定所述第一脉冲信号slp1，所述第一脉冲信号slp1的脉冲长度用于指示所述斜率信号V SLP大于所述第一斜率阈值V TH1的时长tslp1；
    所述控制器根据所述斜率信号V SLP与第二斜率阈值V TH2，确定所述第二脉冲信号slp2，所述第二脉冲信号slp2的脉冲长度用于指示所述斜率信号V SLP小于所述第二斜率阈值V TH2的时长tslp2，所述第二斜率阈值V TH2小于所述第一斜率阈值V TH1。
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