Power converter and control method therefor

Abstract

A power converter and a control method therefor. The power converter comprises: a power conversion circuit, which comprises at least one pair of switch tubes, wherein a first end of one switch tube in each pair of switch tubes is connected to a second end of the other switch tube; and a control circuit, which is connected to the power conversion circuit, and is used for controlling the power conversion circuit, and is used for, after one switch tube in a pair of switch tubes is turned off, acquiring an integral charge value which represents the total charge variation of the pair of switch tubes, and when the integral charge value reaches a corresponding charge threshold value, controlling the other switch tube in the pair of switch tubes to turn on.

Description

Power converter and control method thereof

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 202311658533.4, filed on December 5, 2023, entitled “Power Converter and Control Method Thereof,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the field of power electronics technology, and in particular to a power converter and a control method thereof. Background Art

[0004] In a half-bridge or full-bridge converter, a conduction dead zone is generally set to prevent the bridge arm from being directly turned on. During the dead zone of the bridge arm commutation process, there is a process of commutation from the originally turned-on switching device to the parasitic diode of the complementary tube.

[0005] If the dead time is too short, the zero-voltage turn-on of the switching device cannot be achieved, resulting in additional turn-on losses. If the dead time is set too long, the parasitic diode freewheeling time increases. Since the parasitic diodes of switching devices such as MOS tubes, SiC transistors, and GaN transistors usually have a large conduction voltage drop, the conduction losses of the switching devices are greatly increased. In actual applications, for different currents and different bus voltages, the time for commutation from the originally turned-on switching device to the parasitic diode of its complementary tube during the dead time will also be different. Therefore, in order to achieve zero-voltage turn-on of the switching device under all working conditions, the relevant technology often sets a large fixed value when setting the dead time, resulting in the dead time being too long under most working conditions and the conduction loss of the parasitic diode of the switching device increasing. Summary of the Invention

[0006] According to various embodiments of the present application, a power converter and a control method thereof are provided.

[0007] In a first aspect, an embodiment of the present application provides a power converter, comprising:

[0008] The power conversion circuit includes at least one pair of switching tubes, wherein the first end of one switching tube in each pair of switching tubes is connected to the second end of the other switching tube;

[0009] A control circuit is connected to the power conversion circuit and is used to control the power conversion circuit to obtain an integrated charge value representing the total charge change of the pair of switching tubes after one switching tube in the pair of switching tubes is turned off, and to control the other switching tube in the pair of switching tubes to turn on when the integrated charge value reaches a corresponding charge threshold.

[0010] In some embodiments, the control circuit comprises:

[0011] A sampling circuit samples the electrical signals of a pair of switching tubes to obtain a sampling signal;

[0012] an integrating circuit, connected to the sampling circuit, integrating the sampling signal to obtain the integrated charge value;

[0013] A controller is connected to the integration circuit and includes a control module. The control module provides a dead-band signal for controlling the integration circuit and a control signal for controlling the at least one pair of switch tubes. When one switch tube in a pair of switch tubes is turned off, the dead-band signal controls the integration circuit to start integrating the sampled signal. When the integrated charge value reaches a charge threshold, the control signal controls the other switch tube in the pair of switch tubes to turn on.

[0014] In some embodiments, the electrical signal is a current signal representing the magnitude of the current flowing out of and into the connection point of the pair of switching tubes.

[0015] In some embodiments, the control circuit further comprises:

[0016] A detection module, used to detect the turn-off moment of the switch tube and provide a detection signal to the control module;

[0017] A comparison module is configured to compare the integrated charge value with the charge threshold and output a comparison result to the control module.

[0018] In some embodiments, the control circuit further comprises:

[0019] The rectifier circuit is connected between the sampling circuit and the integration circuit, and is used to rectify the sampling signal and output it to the integration circuit. The integration circuit integrates the rectified sampling signal to obtain the integrated charge value.

[0020] In some embodiments, the control circuit further comprises:

[0021] A rectifier selection circuit is connected between the sampling circuit and the integration circuit, rectifies the sampling signal, and selects to output a rectified sampling signal of a first polarity corresponding to the current flowing out of the connection point or a sampling signal of a second polarity corresponding to the current flowing into the connection point according to a selection signal provided by the controller. The integration circuit integrates the rectified sampling signal of the first polarity or the sampling signal of the second polarity to obtain the integrated charge value.

[0022] In some embodiments, when the voltage across a pair of switching tubes is a DC voltage, at the moment when the switching tube on the high side of the pair of switching tubes is turned off, the selection signal controls the output of the rectification selection circuit to switch to a sampling signal of the first polarity after rectification; and / or

[0023] When the switch tube located at the low side of the pair of switch tubes is turned off, the selection signal controls the output of the rectification selection circuit to switch to a rectified sampling signal of the second polarity.

[0024] In some embodiments, when the voltage across a pair of switching tubes is an AC voltage, during a positive half cycle of the power frequency, at the moment when the high-side switch in the pair of switching tubes is turned off, the selection signal controls the output of the rectification selection circuit to switch to a sampling signal of the first polarity after rectification;

[0025] When the low-side switch in the pair of switch tubes is turned off, the selection signal controls the output of the rectification selection circuit to switch to a rectified sampling signal of the second polarity.

[0026] In some embodiments, the rectification selection circuit includes:

[0027] a separation unit, configured to separate the positive and negative polarities of the sampling signal output by the sampling circuit to obtain a sampling signal of a first polarity corresponding to the current flowing out of the connection point and a sampling signal of a second polarity corresponding to the current flowing into the connection point;

[0028] a rectifier unit, configured to rectify the sampling signal of the first polarity and the sampling signal of the second polarity respectively;

[0029] The selection unit is configured to select and output the rectified sampling signal of the first polarity or the sampling signal of the second polarity according to the selection signal.

[0030] In some embodiments, the power conversion circuit includes:

[0031] An inverter circuit, wherein the inverter circuit is used to invert direct current into alternating current;

[0032] a resonant circuit connected to the inverter circuit;

[0033] A cycloconversion circuit, connected to the resonant circuit, comprising two pairs of switching tubes connected in opposite directions for performing AC-AC conversion;

[0034] After one of the pair of switching tubes in the cycloconversion circuit is turned off, the integration circuit obtains a first integrated charge value representing the total amount of charge change of the pair of switching tubes, and when the first integrated charge value reaches a first charge threshold, the control module controls the other switching tube in the pair of switching tubes to turn on.

[0035] In some embodiments, during a positive half-cycle of the power frequency of the output voltage of the cycloconverter circuit, at the moment when the switch located on the high side of one of the two pairs of switch tubes is turned off, the integration circuit starts integrating the sampling signal corresponding to the rectified current flowing out of the connection point of the pair of switch tubes; and at the moment when the switch located on the low side of the pair of switch tubes is turned off, the integration circuit starts integrating the sampling signal corresponding to the rectified current flowing into the connection point of the pair of switch tubes.

[0036] During the negative half-cycle of the industrial frequency of the output voltage of the cycloconversion circuit, at the moment when the switch tube located on the high side of the other pair of switch tubes in the two pairs of switch tubes is turned off, the integration circuit starts to integrate the sampling signal corresponding to the rectified current flowing out of the connection point of the pair of switch tubes; at the moment when the switch tube located on the low side of the pair of switch tubes is turned off, the integration circuit starts to integrate the sampling signal corresponding to the rectified current flowing into the connection point of the pair of switch tubes.

[0037] In some embodiments, when the integrated charge value reaches a corresponding charge threshold, the control module controls the integration circuit to discharge until the integrated charge value drops to zero.

[0038] In some embodiments, the inverter circuit includes at least one pair of switching tubes. After one of the pair of switching tubes in the inverter circuit is turned off, the integration circuit obtains a second integrated charge value representing the total charge change of the pair of switching tubes, and when the second integrated charge value reaches a second charge threshold, the control module controls the other switch tube in the pair of switching tubes to turn on.

[0039] In some embodiments, the integration circuit comprises:

[0040] a first integration circuit, configured to integrate the rectified sampled signal according to a first dead-band signal to obtain a first integrated charge value, wherein the first dead-band signal is generated by the control module according to a turn-off moment of a switch in the cyclotron conversion circuit and a comparison result of the first integrated charge value with a first charge threshold;

[0041] The second integration circuit is used to integrate the rectified sampling signal according to the second dead zone signal to obtain the second integrated charge value, and the second dead zone signal is generated by the control module according to the turn-off moment of the switch tube in the inverter circuit and the comparison result of the second integrated charge value and the second charge threshold.

[0042] In some embodiments, the power conversion circuit further includes a transformer connected between the inverter circuit and the cycloconversion circuit;

[0043] The first charge threshold is determined according to the output voltage of the cyclotron conversion circuit and / or the parasitic capacitance of the switch tube in the cyclotron conversion circuit and the external parallel capacitance;

[0044] The second charge threshold is determined according to the input voltage of the inverter circuit, the turns ratio of the transformer and / or the parasitic capacitance of the switch tube in the inverter circuit and the external parallel capacitance.

[0045] In some embodiments, when the first integrated charge value reaches a first charge threshold, the control module controls the first integration circuit to discharge until the first integrated charge value drops to 0;

[0046] When the second integrated charge value reaches a second charge threshold, the control module controls the second integration circuit to discharge until the second integrated charge value drops to zero.

[0047] In some embodiments, the power conversion circuit is one of a BUCK type conversion circuit, a BOOST type conversion circuit, an LLC type conversion circuit, a dual active bridge conversion circuit, a cycloconversion circuit, a half-bridge circuit, and a full-bridge circuit.

[0048] In some embodiments, the power converter is a DC-DC power converter, a DC-AC power converter, an AC-AC power converter, or an AC-DC power converter.

[0049] In a second aspect, an embodiment of the present application provides a control method for a power converter, which is used for the power converter according to the first aspect, and the method includes:

[0050] After one of the pair of switch tubes is turned off, an integrated charge value representing a total charge change of the pair of switch tubes is obtained;

[0051] When the integrated charge value reaches a corresponding charge threshold, the other switch tube in the pair of switch tubes is controlled to be turned on.

[0052] In some embodiments, sampling signals are obtained by sampling electrical signals of a pair of switching tubes;

[0053] The sampling signal is integrated to obtain the integrated charge value.

[0054] In some embodiments, the electrical signal is a current signal representing the magnitude of the current flowing out of and into the connection point of the pair of switching tubes.

[0055] In some embodiments, the method further comprises:

[0056] The turn-off moment of the switch tube is detected, and when it is detected that one switch tube in the switch tube pair is turned off, the sampling signal is integrated.

[0057] In some embodiments, the method further comprises:

[0058] The sampling signal is rectified, and the rectified sampling signal is integrated to obtain the integrated charge value.

[0059] In some embodiments, the method further comprises:

[0060] The sampling signal is rectified, and the rectified sampling signal corresponding to the current flowing out of the connection point or the sampling signal corresponding to the current flowing into the connection point is integrated according to the voltage polarity at both ends of the pair of switching tubes and the turn-off moment of the switching tubes to obtain the integrated charge value.

[0061] In some embodiments, when the voltage across a pair of switch tubes is positive, at the moment when the switch tube on the high side of the pair of switch tubes is turned off, a sampling signal corresponding to the current flowing out of the connection point is integrated; and / or

[0062] At the moment when the switch tube located at the low side of the pair of switch tubes is turned off, a sampling signal corresponding to the current flowing into the connection point is integrated.

[0063] In some embodiments, the method further comprises:

[0064] When the integrated charge value reaches the corresponding charge threshold, discharging begins until the integrated charge value drops to 0.

[0065] The details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0067] FIG1 is a schematic diagram of a commutation process of a power conversion circuit in related art.

[0068] FIG2 is a schematic diagram showing the waveform of a control signal and a voltage waveform of a power conversion circuit in the related art.

[0069] FIG3 is a schematic structural diagram of a power converter in the first embodiment provided in this application.

[0070] FIG4 is a schematic diagram of a driving waveform and a voltage waveform in an embodiment provided by the present application.

[0071] FIG5 is a schematic structural diagram of a power converter in a second embodiment provided in this application.

[0072] FIG6 is a schematic structural diagram of a power converter in the third embodiment provided in this application.

[0073] FIG7 is a schematic structural diagram of a power converter in a fourth embodiment provided in this application.

[0074] FIG8 is a schematic structural diagram of a rectifier selection circuit in an embodiment provided by the present application.

[0075] FIG9 is a schematic diagram of the circuit structure of a power converter in the first exemplary embodiment provided in this application.

[0076] FIG10 is a schematic diagram of relevant waveforms of the power converter in the first exemplary embodiment provided in this application.

[0077] FIG11 is a schematic diagram of the circuit structure of a power converter in a second exemplary embodiment provided in this application.

[0078] FIG12 is a schematic diagram of the circuit structure of the power conversion circuit in the third exemplary embodiment provided by the present application.

[0079] FIG13 is a schematic diagram of the circuit structure of the control circuit in the third exemplary embodiment provided in this application.

[0080] FIG14 is a schematic diagram of relevant waveforms of a power converter in the third exemplary embodiment provided in this application.

[0081] FIG15 is a schematic diagram of relevant waveforms of a power converter in the fourth exemplary embodiment provided in this application.

[0082] FIG16 is a schematic diagram of the circuit structure of the control circuit in the fourth exemplary embodiment provided in this application.

[0083] FIG17 is a flow chart of a method for controlling a power converter provided in the present application. DETAILED DESCRIPTION

[0084] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for ordinary technicians in the field related to the contents disclosed in the present application, some changes such as design, manufacturing or production based on the technical contents disclosed in the present application are only conventional technical means and should not be understood as the contents disclosed in the present application being insufficient.

[0085] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments unless there is a conflict.

[0086] Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person of ordinary skill in the technical field to which this application belongs. The words "one", "a", "the" and the like used in this application do not indicate a limit on quantity and may indicate the singular or plural. The terms "include", "comprise", "have" and any variations thereof used in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units that are inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The word "multiple" used in this application means greater than or equal to two. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. The terms "first", "second", "third" and the like involved in this application are merely used to distinguish similar objects and do not represent a specific ordering of the objects.

[0087] FIG1 is a schematic diagram of the commutation process of a power conversion circuit in the related art. The power conversion circuit includes a capacitor C busand connected to the capacitor C bus The complementary conducting switch tubes Q1 and Q2 at both ends, the middle connection point of the switch tubes Q1 and Q2 outputs the current i L Capacitor C1 and capacitor C2 are parasitic capacitances of switch tube Q1 and switch tube Q2 respectively.

[0088] The waveform of the control signal of the switch tube in the above power conversion circuit and the voltage waveform of the switch tube Q2 are shown in Figure 2. c2 is the voltage across the drain and source of the switch tube Q2, Vg1 is the control signal of the switch tube Q1, and Vg2 is the control signal of the switch tube Q2. When the control signal Vg1 is high and the control signal Vg2 is low, the switch tube Q1 is turned on and the switch tube Q2 is turned off. The current i L Flows through the switch tube Q1, as shown in Figure 1(a); after the control signal Vg1 changes from high level to low level, the control signal Vg2 continues to remain at a low level, and the capacitor C bus The voltage V bus The parasitic capacitance C1 of the switch tube Q1 starts to charge, and the current i L Discharge the parasitic capacitance C2 of the switch tube Q2, as shown in Figure 1(b), corresponding to the time period t0 to t1 in Figure 2; when the voltage on the parasitic capacitance C1 rises to V bus At the same time, after the voltage on parasitic capacitor C2 drops to zero, the parasitic diode of switch Q2 begins to conduct, as shown in Figure 1(c), corresponding to the time period t1 to t2 in Figure 2. When the control signal Vg2 of switch Q2 goes high, the current of switch Q2 switches from the parasitic diode to the channel, as shown in Figure 1(d), corresponding to time t2 in Figure 2. This completes the entire commutation process.

[0089] The related art sets the time period t0 to t2 as a fixed dead time, which cannot reduce the parasitic diode conduction loss to near zero under all operating conditions. Therefore, the increased loss will lead to a problem of reduced conversion efficiency of the power converter.

[0090] In Figures 1 and 2, when switch Q1 is turned off, the ideal commutation time of the switch is t0-t1. During this period, parasitic capacitor C1 charges and parasitic capacitor C2 discharges. When switch Q2 is turned off, the ideal commutation time of the switch is t3-t4. During this period, parasitic capacitor C1 discharges and parasitic capacitor C2 charges. The total charge change on parasitic capacitors C1 and C2 (i.e., the total charge change on switches Q1 and Q2) satisfies the following relationship:

[0091] Among them, v c1 is the voltage across the drain and source of the switch tube Q1, v c2is the voltage across the drain and source of the switch tube Q2, C1 (v c1 ) is the capacitance of the parasitic capacitor C1 with respect to the voltage v across the drain and source of the switch tube Q1 c1 Function, C2(v c2 ) is the capacitance of parasitic capacitor C2 with respect to the voltage v across the drain and source of switch tube Q2 c2 function, i1 is the current flowing through the switch tube Q1, i2 is the current flowing through the switch tube Q2, i L is the current flowing into and out of the connection point between the switch tube Q1 and the switch tube Q2.

[0092] Based on this, an embodiment of the present application proposes a power converter, as shown in Figure 3, which includes: a power conversion circuit 10, the power conversion circuit 10 includes at least one pair of switching tubes, and the first end of one switching tube in each pair of switching tubes is connected to the second end of the other switching tube; a control circuit 20, connected to the power conversion circuit 10, for controlling the power conversion circuit 10, after one switching tube in a pair of switching tubes is turned off, obtaining an integrated charge value representing the total charge change of the pair of switching tubes, and when the integrated charge value reaches a charge threshold, controlling the other switching tube in the pair of switching tubes to turn on.

[0093] The switching tubes mentioned above may be MOSFETs, SiC transistors, GaN transistors, and IGBT modules with parallel Schottky diodes.

[0094] It should be noted that when the switching tube is a MOSFET, the first end of the switching tube described in this application is the drain of the switching tube, and the second end of the switching tube is the source of the switching tube. When the switching tube is an IGBT module with a parallel Schottky diode, the first end of the switching tube described in this application is the collector of the switching tube, and the second end of the switching tube is the emitter of the switching tube.

[0095] Among them, the power conversion circuit is used to perform power conversion, for example, it can perform inversion, or rectification, or DC-DC conversion, or AC-AC conversion, and can include any one of a BUCK type conversion circuit, a BOOST type conversion circuit, an LLC type conversion circuit, a dual active bridge conversion circuit, a cycloconversion circuit, a half-bridge circuit, a full-bridge circuit, etc.

[0096] The power converter may be a DC-DC power converter, a DC-AC power converter, an AC-AC power converter, an AC-DC power converter, or the like.

[0097] In this embodiment, after one switch tube in a pair of switch tubes is turned off, an integrated charge value representing the total charge change of the pair of switch tubes is obtained, and when the integrated charge value reaches a charge threshold, the other switch tube in the pair of switch tubes is controlled to turn on, thereby achieving zero-voltage turn-on of the switch tube, avoiding the conduction loss of the parasitic diode of the switch tube, and improving the conversion efficiency of the power converter.

[0098] Since the charge threshold represents the total charge change △Q of a pair of switch tubes in the ideal commutation period t0-t1, it can be calculated based on the voltage V bus (that is, the voltage between the first end of a switch tube and the second end of another switch tube) is adjusted, so that adaptive adjustment of the dead time can be achieved.

[0099] Specifically, the value of the total charge change ΔQ during the ideal commutation period t0-t1 is proportional to the voltage V across the pair of switching tubes. bus The parasitic capacitance of the switch tube is related to its additional parallel capacitance (if there is an additional parallel capacitance). When the capacitance of the switch tube and its parallel capacitance is determined, the total charge change △Q and voltage V in the ideal commutation time period can be fitted. bus Therefore, by adjusting the current i L Integrate to get the integrated charge value that represents the total amount of real-time charge change of a pair of switch tubes. When the integrated charge value is equal to the known voltage V bus When the value of the total charge change △Q in the corresponding ideal commutation time period is equal, the switch commutation is just completed at this time. At this time, the zero voltage turn-on of the switch tube can be achieved and the conduction loss of the parasitic diode of the switch tube is avoided.

[0100] The result of controlling the power conversion circuit of FIG1 by using the control circuit of this embodiment is shown in FIG4. When the switch tube Q1 is turned off, the outgoing current i L Integrate, and when the integrated charge value reaches the corresponding voltage V bus When the total charge change △Q value of the ideal commutation time period t0-t1 is equal to the value of the ideal commutation time period t0-t1, that is, at time t1, the switch commutation is just completed, and the switch tube Q2 is triggered to turn on to achieve zero voltage turn-on; similarly, when the switch tube Q2 is turned off, the inflow current i L When the integrated charge value reaches the value of the total charge change △Q, that is, at time t3, the switch commutation is just completed, and the switch tube Q1 is triggered to turn on to achieve zero voltage switching.

[0101] From the above analysis, it can be seen that at the time when a switch tube is turned off, the integrated charge value representing the total charge change of the pair of switch tubes is obtained, and the switch commutation completion time is determined based on the integrated charge value and the known charge threshold. After the parasitic diode commutation of the switch tube to the complementary switch tube is completed, the switch tube that is complementary to it is immediately turned on. This can eliminate the time period t1 to t2 or t4 to t5 shown in Figure 2, avoid the conduction loss caused by the conduction of the parasitic diode, improve the efficiency of the power converter, and achieve zero-voltage turn-on.

[0102] In some embodiments, as shown in Figure 5, the control circuit 20 includes: a sampling circuit 201, which samples the electrical signal of a pair of switching tubes to obtain a sampling signal; an integration circuit 202, which is connected to the sampling circuit 201, and integrates the sampling signal to obtain the integrated charge value; a controller 203, which is connected to the integration circuit 202, and includes a control module, which provides a dead zone signal for controlling the integration circuit and a control signal for controlling the at least one pair of switching tubes. When one switching tube in a pair of switching tubes is turned off, the dead zone signal controls the integration circuit 202 to start integrating the sampling signal, and when the integrated charge value reaches a charge threshold, the control signal controls the other switching tube in the pair of switching tubes to turn on.

[0103] The electrical signal is a current signal representing the magnitude of the current flowing out and in from the connection point of the pair of switch tubes. It can be the current output from the connection point of the pair of switch tubes, or it can be the current flowing through each switch tube in the pair of switch tubes, but is not limited thereto.

[0104] The sampling circuit 201 may be a current transformer or a sampling resistor, or other current sampling devices or equipment. If the sampling circuit 201 uses a current transformer for sampling, the sampling circuit 201 also includes a conversion circuit for converting the current signal into a voltage signal.

[0105] The integration circuit 202 may be constructed from components such as an integration capacitor, a switch device, and an amplifier to achieve its integration function.

[0106] The controller 203 may be an MCU (Microcontroller Unit), a DSP (Digital Signal Processing), or the like.

[0107] In practical applications, the charge threshold is related to the voltage V across a pair of switching tubes. bus The corresponding relationship can be represented by a table or a function relationship and stored in the controller 203. The controller 203 is based on the voltage V at both ends of a pair of switch tubes. bus The corresponding charge threshold is determined to achieve adaptive adjustment of the dead time.

[0108] Furthermore, the control circuit 20 further includes: a detection module, which is used to detect the turn-off moment of the switch tube and provide a detection signal to the control module.

[0109] The detection module may be a signal detection circuit inside the controller, for example, detecting the falling edge of the control signal of the switch tube to determine the switch tube's turn-off moment.

[0110] In some embodiments, the detection module may also be provided outside the controller to detect the turn-off moment of the switch tube.

[0111] In some embodiments, the control circuit 20 further includes: a comparison module, configured to compare the integrated charge value with the charge threshold and output the comparison result to the control module.

[0112] It should be noted that the comparison module can be integrated into the controller or provided outside the controller.

[0113] The comparison module can use a comparator or the like to implement its comparison function.

[0114] For some power converters, when the electrical signal is a current signal, the sampling circuit can only sample and process positive polarity current signals. When the actual current signal is a positive and negative bipolar current signal, the negative polarity current signal cannot be sampled normally.

[0115] To solve the above technical problems, in some embodiments, as shown in Figure 6, the control circuit 20 also includes: a rectifier circuit 204, connected between the sampling circuit 201 and the integration circuit 202, for rectifying the sampling signal and outputting it to the integration circuit 202, and the integration circuit 202 integrates the rectified sampling signal to obtain the integrated charge value.

[0116] After passing through the rectifier circuit 204 , the sampling signal with negative polarity is flipped into a sampling signal with positive polarity. At this time, the integration circuit 202 can integrate the sampling signal.

[0117] The rectifier circuit 204 may be composed of rectifier diodes, such as a rectifier bridge.

[0118] For some power converters, under special working conditions, when the electrical signal is a positive and negative bipolar current signal, a current signal of a certain polarity has no effect on the commutation of the switch tube and is an invalid current.

[0119] To solve the above technical problems, in some embodiments, as shown in Figure 7, the control circuit 20 also includes: a rectification selection circuit 205, connected between the sampling circuit 201 and the integration circuit 202, for rectifying the sampling signal and selecting to output the rectified sampling signal of the first polarity corresponding to the current flowing out of the connection point or the sampling signal of the second polarity corresponding to the current flowing into the connection point according to the selection signal provided by the controller 203. The integration circuit 202 integrates the rectified sampling signal of the first polarity or the sampling signal of the second polarity to obtain the integrated charge value.

[0120] The selection signal is generated by the controller according to the voltage polarity at both ends of the pair of switching tubes and the turn-off time of the switching tubes.

[0121] In this embodiment, after a pair of switching tubes are turned off, the sampling signal corresponding to the current that has an effect on commutation is selected by the rectifier selection circuit 205 for integration, thereby ensuring that the power converter can achieve zero-voltage turn-on of the pair of switching tubes even under special working conditions, avoiding the conduction loss of the parasitic diodes of the switching tubes and improving the conversion efficiency of the power converter.

[0122] It should be noted that the first polarity here may be positive, and the corresponding second polarity may be negative; or the first polarity may be negative, and the corresponding second polarity may be positive.

[0123] Specifically, when the voltage V across a pair of switch tubes bus When it is a DC voltage, at the moment when the switch tube located on the high side of the pair of switch tubes is turned off, the selection signal controls the output of the rectification selection circuit 205 to switch to the sampling signal of the first polarity after rectification; and / or at the moment when the switch tube located on the low side of the pair of switch tubes is turned off, the selection signal controls the output of the rectification selection circuit 205 to switch to the sampling signal of the second polarity after rectification.

[0124] The voltage V across a pair of switching tubes bus In the case of AC voltage, in the positive half cycle of the power frequency, that is, the voltage V across a pair of switching tubes bus The selection signal is positive polarity. When the high-side switch in the pair of switch tubes is turned off, the selection signal controls the output of the rectifier selection circuit 205 to switch to the sampling signal of the first polarity after rectification. When the low-side switch in the pair of switch tubes is turned off, the selection signal controls the output of the rectifier selection circuit 205 to switch to the sampling signal of the second polarity after rectification.

[0125] It should be noted that the switch tube located on the high side of a pair of switch tubes described in this application refers to the switch tube at a high potential in the pair of switch tubes; the switch tube located on the low side of a pair of switch tubes described in this application refers to the switch tube at a low potential in the pair of switch tubes.

[0126] As shown in FIG8 , the rectifier selection circuit 205 includes: a separation unit 2051 for separating the sampling signal i cs The positive and negative polarities are separated to obtain a sampling signal of a first polarity corresponding to the current flowing out of the connection point and a sampling signal of a second polarity corresponding to the current flowing into the connection point; a rectifier unit 2052 is used to rectify the sampling signal of the first polarity and the sampling signal of the second polarity respectively; a selection unit 2053 is used to select and output the rectified sampling signal of the first polarity or the sampling signal of the second polarity according to the selection signal to obtain the rectified selected sampling signal i rec .

[0127] Specifically, the separation unit 2051 may be composed of multiple diodes, resistors and other components; the rectification unit 2052 may be composed of rectification diodes and the like; the selection unit 2053 may be composed of selectors, resistors, capacitors and other components.

[0128] In the first exemplary embodiment, the power converter may be a BUCK or BOOST converter. As shown in FIG9 , the power converter includes a power conversion circuit 10 and a control circuit 20. The power conversion circuit 10 includes a pair of switch tubes, a capacitor C dc , capacitor C4 and inductor L. The pair of switch tubes includes a switch tube S1 located on the high side and a switch tube S2 located on the low side. The switch tube S1 and the switch tube S2 are complementary and conductive. The second end of the switch tube S1 is connected to the first end of the switch tube S2. The voltage between the first end of the switch tube S1 and the second end of the switch tube S2 is V dc The connection point of the switch tube S1 and the switch tube S2 is connected to one end of the inductor L, and the output current i L Capacitor C1 and capacitor C2 are parasitic capacitances of switch tube S1 and switch tube S2 respectively, and capacitor C4 is connected between the other end of inductor L and the common ground.

[0129] The control circuit 20 includes a sampling circuit 201, an integrating circuit 202 and a controller 203. The controller 203 includes a control module 2031, a comparison module 206 and a detection module 207. dc When the side is the input side and the capacitor C4 side is the output side, the power converter is a BUCK converter; when the capacitor C dc When the capacitor C4 side is the output side and the capacitor C5 side is the input side, the power converter is a BOOST converter. When the power converter is a BUCK converter, the current i L The direction is to the right, that is, it flows out of the connection point of the switch tube S1 and the switch tube S2, as shown by the arrow in Figure 9. When the power converter is a BOOST converter, the current i L The direction is opposite to that indicated by the arrow in FIG9 , that is, it flows into the connection point between the switch tube S1 and the switch tube S2 .

[0130] The sampling circuit 201 is used to measure the current i L Sampling is performed to obtain the sampling signal i cs .

[0131] The integration circuit 202 performs the sampling signal i cs Integrate to get the integrated charge value Q int .

[0132] Specifically, integration circuit 202 includes a selector switch ST, resistors R1-R5, an integrating capacitor C3, and an operational amplifier OP. Resistor R1 is connected between sampling circuit 201 and point a of selector switch ST. One end of resistor R2 is connected to point b of selector switch ST, and the other end is connected to one end of integrating capacitor C3 and to a reference ground. The other end of integrating capacitor C3 is connected to the fixed end of selector switch ST and the non-inverting input of operational amplifier OP. Resistor R5 is connected between a common ground and the inverting input of operational amplifier OP. Resistor R4 is connected between the inverting input and output of operational amplifier OP. Resistor R3 is connected between the non-inverting input and output of operational amplifier OP.

[0133] Resistor R2 serves as the discharge unit, while resistors R1, R3-R5, integrating capacitor C3, and operational amplifier OP form the integration unit. The selector switch ST is a single-pole, double-throw switch that controls the switch contact to connect to point a or point b based on the dead-band signal DS. When the switch contact is connected to point a, the integration unit integrates; when the switch contact is connected to point b, the integration unit stops integrating and the discharge unit begins discharging.

[0134] The detection module 207 is used to detect the turn-off moment of the switch S1 or the switch S2 and provide a detection signal to the control module 2031. This is achieved, for example, by detecting the turn-off edge of the control signal Vg1 for the switch S1 and the turn-off edge of the control signal Vg2 for the switch S2. The detection module 207 can be a signal detection circuit within the controller 203 or independently provided outside the controller 203. This embodiment uses the controller 203 as an example for description.

[0135] The comparison module 206 includes a comparator Comp, which is used to convert the integrated charge value Q int and charge threshold Q ref The comparison is performed and the comparison result is output to the control module 2031. The comparator Comp can be implemented by a comparator inside the controller or by a discrete analog comparator device. This embodiment takes the comparison module 206 disposed in the controller 203 as an example for explanation.

[0136] The control module 2031 generates a dead-time signal DS according to the comparison result and the detection signal, and generates control signals Vg1 and Vg2 including dead-time according to the dead-time signal DS and a reference control signal.

[0137] When the power converter is a BUCK converter, the switch tube S1 is a hard switch, and the control module 2031 performs soft-on control on the switch tube S2. The specific control method is as follows: the sampling circuit 201 performs soft-on control on the current i L Real-time sampling, at any voltage V dc Under the present invention, when the detection module 207 detects the turn-off edge of the control signal Vg1 of the switch tube S1, such as the time t6 corresponding to the control signal Vg- in FIG10 , the control module 2031 provides a high-level dead-zone signal DS according to the detection signal output by the detection module 207, controls the switch contact of the selection switch ST to be connected to the a terminal, and the integration circuit 202 immediately starts integration. When the integrated charge value Q int Reaching the charge threshold Q ref At the time t7 corresponding to the control signal Vg-active in FIG10 , that is, when equation (1) is satisfied, the voltage across the parasitic capacitor C2 of the switch tube S2 just drops to 0V, as shown in the waveform of "VS-synchronization" in FIG10 . The control signal Vg2 controls the switch tube S2 to turn on, achieving zero voltage turn-on. At the same time, the parasitic diode of the switch tube S2 will not conduct, thereby avoiding the large loss caused by the conduction of the parasitic diode. At this time, the comparator Comp in the comparison module 206 immediately outputs a high-level signal, and the control module 2031 provides a low-level dead zone signal DS according to the output signal of the comparator Comp, controls the switch contact of the selection switch ST to be connected to the b terminal, and discharges the charge on the integral capacitor C3 through the resistor R2. Based on the above control method for the BUCK converter, the conduction loss of the parasitic diode of the switch tube S2 is eliminated, the loss of the switch tube S2 is reduced, and the conversion efficiency of the BUCK converter is improved.

[0138] When the power converter is a BOOST converter, the switch tube S2 is a hard switch, and the control module 2031 performs soft opening control on the switch tube S1. The control principle is the same as the adaptive control of the switch tube S2 by the BUCK converter. The difference is that the detection module 207 detects the turn-off edge of the control signal Vg2 of the switch tube S2. When the integrated charge value Q int Reaching the charge threshold Q ref When , the switch tube S1 is turned on. Based on the above control method for the BOOST converter, the conduction loss of the parasitic diode of the switch tube S1 is eliminated, the loss of the switch tube S1 is reduced, and the conversion efficiency of the BOOST converter is improved.

[0139] When the power converter is a BUCK converter, switch S1 is an active switch and switch S2 is a synchronous switch. When the power converter is a BOOST converter, switch S1 is a synchronous switch and switch S2 is an active switch. In Figure 10, "PWM-active" is the reference control signal for the active switch without dead time, and "PWM-synchronous" is the reference control signal for the synchronous switch. A dead time is set between its falling edge and the reference control signal of the active switch, as shown in the period t8 to t9. The reference control signal can be generated by the control module 2031 according to the specific control requirements of the power conversion circuit; the current i L and the sampled signal i cs The waveform of the sampling signal i cs is the input signal of the integration circuit 202; DS is the dead zone signal including the dead zone time; "Vg-active" and "Vg-sync" are the control signals of the active switch tube and the synchronous switch tube, respectively, which are generated by the control module 2031 according to the reference control signal and the dead zone time; "VS-active" and "VS-sync" are the voltage stress waveforms borne by the active switch tube and the synchronous switch tube, respectively.

[0140] It should be noted that when the power converter is in steady state, the voltage V dc It does not change, so there is no need to adaptively adjust the dead time in each cycle. The dead time when entering the steady state can be used as the dead time of each subsequent cycle. It is not necessary to perform integration and comparison controls in each cycle, which further reduces losses.

[0141] When the integrated charge value Q int Reach the corresponding charge threshold Q ref When the control module 2031 controls the integration circuit 202 to discharge, the integrated charge value Q int Dropped to 0.

[0142] In the second exemplary embodiment, the power converter is an LLC converter. As shown in FIG11 , the power conversion circuit in the power converter includes a pair of switch tubes, a capacitor C dc , output capacitor C out , inductance L, excitation inductance L m , resonant capacitor C5, transformer T with a center tap, and rectifier diodes D1 and D2. The pair of switches includes a switch S1 located on the high side and a switch S2 located on the low side. The second end of the switch S1 is connected to the first end of the switch S2. The voltage between the first end of the switch S1 and the second end of the switch S2 is V dc The connection point of the switch tube S1 and the switch tube S2 is connected to one end of the inductor L through the resonant capacitor C5, and the output current i LThe other end of the inductor L is connected to the same end of the primary winding of the transformer T. The excitation inductor L m Connected to the primary side of transformer T, the same-name end and opposite-name end of the secondary winding of transformer T are connected to rectifier diodes D1 and D2 respectively, and rectifier diodes D1 and D2 are connected to an output terminal of the power converter. Output capacitor C out Connect between the center tap of the secondary winding and this output terminal.

[0143] The control circuit includes a sampling circuit 201, an integration circuit 202, a rectifier circuit 204 and a controller 203. The controller 203 includes a control module 2031, a comparison module 206 and a detection module 207. The inductor L can be the leakage inductance of the transformer T or an independent inductor. m is the magnetizing inductance of transformer T.

[0144] The same points as those in the first exemplary embodiment will not be described in detail, and only the differences will be described below.

[0145] In this exemplary embodiment, both the switch S1 and the switch S2 are soft-turned on. The controller 203 performs soft-turning control on the switch S1 and the switch S2. The corresponding detection module 207 is used to detect the turn-off moment of the switch S1 and the switch S2.

[0146] The rectifier circuit 204 is connected between the sampling circuit 201 and the integration circuit 202 and is used to rectify the sampling signal to obtain a rectified sampling signal and output it to the integration circuit 202. The integration circuit 202 integrates the rectified sampling signal to obtain the integrated charge value.

[0147] The specific control method is: the sampling circuit 201 is used to control the current i L The sampling signal is obtained by real-time sampling, and the rectifier circuit 204 rectifies the sampling signal in real time. Assuming that the current i in FIG. 11 is specified L When the current is positive to the right, that is, the current flowing out of the connection point of the switch tube S1 and the switch tube S2 is positive, at any voltage V dc In the following example, when the detection module 207 detects the falling edge of the control signal Vg1 of the switch tube S1, as shown in FIG4 at the time t0 corresponding to the control signal Vg1, the dead zone signal DS controls the switch contact of the selection switch ST to be connected to the a terminal. At this time, the current i L The direction of the current is shown as the arrow in Figure 11 under steady-state operation, which is a positive current. The integration circuit 202 immediately starts integrating the rectified sampling signal. When the integrated charge value reaches the charge threshold Q refWhen , that is, when equation (1) is satisfied, the voltage across the parasitic capacitor C2 of switch tube S2 drops to 0V, and control signal Vg2 turns switch tube S2 on, achieving zero-voltage turn-on. The parasitic diode of switch tube S2 will not conduct, thus avoiding the large losses caused by the conduction of the parasitic diode. At this time, the dead-band signal DS controls the switch contact of the selection switch ST to connect to terminal b, discharging the integrated charge on the integration capacitor C3 through resistor R2.

[0148] When the detection module 207 detects the falling edge of the control signal Vg2 of the switch tube S2, as shown in FIG4 at time t3 corresponding to the control signal Vg2, the dead zone signal DS controls the switch contact of the selection switch ST to be connected to the a terminal. At this time, the current i L The direction of the current is opposite to the direction of the arrow in FIG11 under steady-state operation, which is a negative current. The sampling circuit 201 senses the current i L The sampling circuit 202 immediately integrates the rectified sampling signal after the negative polarity sampling signal is rectified by the rectifier circuit 204. When the integrated charge value reaches the charge threshold Q ref When , that is, when equation (2) is satisfied, the voltage across the parasitic capacitor C1 of switch tube S1 drops to 0V. At this time, control signal Vg1 turns switch tube S1 on, achieving soft switching. The parasitic diode of switch tube S1 will not conduct, thus avoiding the large losses caused by the conduction of the parasitic diode. At this time, the dead-band signal DS controls the switch contact of the selection switch ST to connect to terminal b, discharging the charge on the integral capacitor C3 through resistor R2.

[0149] The half-bridge LLC converter in FIG11 avoids the conduction loss of the parasitic diodes of the switch tubes S1 and S2, thereby improving the efficiency of the converter.

[0150] This second exemplary embodiment only takes a half-bridge LLC converter as an example, but is not limited thereto. It may be a DAB (Dual Active Bridge) converter, a half-bridge DC-DC converter, a full-bridge DC-DC converter, an active PFC (Power Factor Correction) circuit, a three-phase inverter bridge or a three-phase active rectifier bridge circuit, etc.

[0151] In a third exemplary embodiment, the power converter is an inverter, the input of which can be connected to a photovoltaic DC power source or an energy storage battery, etc., and inverts the DC power provided by the photovoltaic DC power source or the energy storage battery into AC power, which can be used to supply power to the grid or a load. The photovoltaic DC power source can be, for example, a single photovoltaic module, a single photovoltaic cell substring, multiple photovoltaic modules connected in series and / or parallel, or multiple photovoltaic cell substrings connected in series and / or parallel. Taking the input end connected to a photovoltaic DC power source and supplying power to the grid as an example, as shown in FIG12 , the power converter includes a power conversion circuit 10 and a control circuit 20.

[0152] The power conversion circuit 10 includes an inverter circuit 101, which is used to convert DC power into AC power; a transformer T connected to the inverter circuit 101 for stepping up and down the voltage; a resonant circuit 103 connected to the secondary winding of the transformer T for soft switching; and a cycloconverter circuit 102 connected to the resonant circuit 103, comprising two pairs of reversely connected switching transistors for AC-AC conversion. A filter circuit 104 is connected to the output of the cycloconverter circuit 102 for filtering to obtain an AC voltage V that can be provided to the power grid. grid .

[0153] After one of the pair of switch tubes in the cyclo-wave conversion circuit 102 is turned off, the integration circuit 202 obtains a first integrated charge value representing the total charge change of the pair of switch tubes, and when the first integrated charge value reaches a first charge threshold, the control module controls the other switch tube in the pair of switch tubes to turn on.

[0154] During the positive half-cycle of the power frequency output voltage of the cycloconverter circuit 102, when the high-side switch in one of the two pairs of switches is turned off, the integration circuit 202 begins to integrate the sampling signal corresponding to the rectified current flowing out of the connection point of the pair of switches; and when the low-side switch in the pair of switches is turned off, the integration circuit 202 begins to integrate the sampling signal corresponding to the rectified current flowing into the connection point of the pair of switches.

[0155] During the negative half-cycle of the industrial frequency of the output voltage of the cyclo-wave conversion circuit 102, at the moment when the switch tube located on the high side of the other pair of switch tubes in the two pairs of switch tubes is turned off, the integration circuit 202 starts to integrate the sampling signal corresponding to the rectified current flowing out of the connection point of the pair of switch tubes; at the moment when the switch tube located on the low side of the pair of switch tubes is turned off, the integration circuit 202 starts to integrate the sampling signal corresponding to the rectified current flowing into the connection point of the pair of switch tubes.

[0156] Specifically, the resonant circuit 103 is connected to one end of the secondary winding of the transformer T, and includes an inductor L and a resonant capacitor C5 connected in series. The inductor L may be the leakage inductance of the transformer T or an independent inductor.

[0157] The turns ratio of the primary and secondary windings of the transformer T is 1:N.

[0158] The cycloconverter circuit 102 is a half-bridge cycloconverter comprising two pairs of switches connected in opposite directions. Specifically, one pair of switches comprises a switch S3 on the high side and a switch S5 on the low side, with switches S3 and S5 conducting in a complementary manner. The other pair of switches comprises a switch S4 on the low side and a switch S6 on the high side, with switches S4 and S6 conducting in a complementary manner. The second end of switch S3 is connected to the first end of switch S5 via switch S4, and the second end of switch S6 is connected to the first end of switch S4 via switch S5. Switches S3 and S5 are connected in opposite directions to switches S4 and S6. Switches S4 and S5 are connected at point A and are connected to the resonant circuit 103. The connection point A between the switch tube S4 and the switch tube S5 is the connection point between the switch tube S3 and the switch tube S5, and is also the connection point between the switch tube S4 and the switch tube S6. Therefore, the current signal representing the magnitude of the current flowing out and into the connection point between the switch tube S3 and the switch tube S5 is the current i flowing through the resonant circuit 103. L , which is the resonant current. The current signal representing the magnitude of the current flowing out and in at the connection point between the switch tube S4 and the switch tube S6 is also the current i flowing through the resonant circuit 103. L .

[0159] The filter circuit 104 includes an inverter-side filter capacitor C f and the inverter side filter inductor L f , filter inductor L f The high-frequency switching current is filtered to obtain a clean industrial frequency AC output current.

[0160] Furthermore, the inverter circuit 101 includes at least one pair of switching tubes. After one of the pair of switching tubes in the inverter circuit 101 is turned off, the integration circuit 202 obtains a second integrated charge value representing the total charge change of the pair of switching tubes, and controls the other switching tube in the pair of switching tubes to turn on when the second integrated charge value reaches a second charge threshold.

[0161] Specifically, the inverter circuit can be a full-bridge circuit or a half-bridge inverter circuit, with the full-bridge circuit being taken as an example. The inverter circuit 101 includes two pairs of switches, one pair of which includes a switch S7 located on the high side and a switch S8 located on the low side, and the second end of the switch S7 is connected to the first end of the switch S8; the other pair includes a switch S9 located on the high side and a switch S10 located on the low side, and the second end of the switch S9 is connected to the first end of the switch S10; the switch S7 and the switch S8 are complementary conductive; the switch S9 and the switch S10 are complementary conductive. The middle connection point of the switches S7 and S8 and the middle connection point of the switches S9 and S10 are respectively connected to the two ends of the primary winding of the transformer T. The current signal representing the magnitude of the current flowing out and in at the connection point of the switch S7 and the switch S8 is the current i flowing through the resonant circuit 103. L The current signal representing the magnitude of the current flowing out and in at the connection point between the switch tube S9 and the switch tube S10 is also the current i flowing through the resonant circuit 103. L .

[0162] The input voltage of the inverter circuit 101, that is, the voltage across the two pairs of switches is V dc , is a DC voltage. Switches S3 to S6 and S7 to S10 have parasitic capacitances C30, C40, C50, C60, C70, C80, C90, and C100, respectively.

[0163] As shown in FIG. 13 , the control circuit 20 includes a sampling circuit (not shown), an integration circuit 202 , a control module 2031 , a detection module 207 , a comparison module 206 and a rectification circuit 204 .

[0164] The sampling circuit is used to measure the resonant current i L Sampling is performed to obtain the sampling signal i cs .

[0165] The rectifier circuit 204 provides a sampling signal i to the sampling circuit. cs Rectify to obtain the rectified sampling signal i rec and provided to the integration circuit 202 .

[0166] The integration circuit 202 integrates the rectified sampling signal i rec Integrate to obtain a first integrated charge value Q representing the total charge change of each pair of switch tubes in the cyclic conversion circuit 102 int1 and obtaining a second integrated charge value Q representing the total charge change of each pair of switching tubes in the inverter circuit 101 int2 .

[0167] The comparison module 206 is used to compare the first integrated charge value Q int1 and the first charge threshold Q ref1The comparison is performed and the comparison result is output to the control module 2031, and the second integrated charge value Q is int2 and the second charge threshold Q ref2 Perform comparison and output the comparison result to the control module 2031.

[0168] The detection module 207 is used to detect the turn-off moments of the switches S3 - S6 and S7 - S10 , for example, by detecting the turn-off edges of the control signals Vg3 - Vg6 of the switches S3 - S6 and the control signals Vg7 - Vg10 of the switches S7 - S10 .

[0169] The control module 2031 is used to generate control signals Vg3 - Vg6 for controlling the switches S3 - S6 and control signals Vg7 - Vg10 for the switches S7 - S10 , and to generate a first dead zone signal DS1 and a second dead zone signal DS2 according to outputs of the detection module 206 and the comparison module 206 .

[0170] The integration circuit 202 includes: a first integration circuit 2021 for integrating the rectified sampling signal i according to the first dead zone signal DS1 provided by the control module 2031. rec Integrate to obtain the first integrated charge value Q int1 The first dead zone signal DS1 is generated by the control module 2031 according to the turn-off time of the switch tube in the cyclotron circuit 102 and the first integrated charge value Q int1 With the first charge threshold Q ref1 The comparison result is generated; a second integrator circuit 2022 for rectified sampling signal i according to the second dead zone signal DS2 provided by the control module 2031 rec Integrate to obtain the second integrated charge value Q int2 The second dead zone signal DS2 is generated by the control module 2031 according to the turn-off time of the switch tube in the inverter circuit 101 and the second integrated charge value Q int2 With the second charge threshold Q ref2 The comparison result is generated.

[0171] The first integration circuit 2021 and the second integration circuit 2022 may adopt the structure of the integration circuits in the aforementioned embodiments of the present application.

[0172] The comparison module 206 includes: a first comparison unit 2061, configured to compare the first integrated charge value Q int1 and the first charge threshold Q ref1The comparison is performed and the comparison result is output to the control module 2031. The control module 2031 generates a first dead zone signal DS1 according to the detection signal corresponding to the switch tube in the frequency conversion circuit 102 and the comparison result output by the first comparison unit 2061 and provides the signal to the first integration circuit 2021. The second comparison unit 2062 is used to convert the second integrated charge value Q int2 and the second charge threshold Q ref2 The comparison is performed and the comparison result is output to the control module 2031 . The control module 2031 generates a second dead zone signal DS2 according to the detection signal corresponding to the switch tube in the inverter circuit 101 and the comparison result of the second comparison unit output 2062 and provides it to the second integration circuit 2022 .

[0173] Since the inverter provides AC output, the AC voltage V grid In each power frequency cycle, the output voltage of the cyclic conversion circuit 102 (that is, the filter capacitor C f The voltage on the power frequency has a positive half cycle and a negative half cycle. Taking the control of the cycloconverter circuit 102 as an example, in the positive half cycle of the power frequency of the output voltage of the cycloconverter circuit 102, that is, the AC voltage V grid During the positive half cycle, the control module 2031 controls the switch tube S4 and the switch tube S6 to remain in the on state, and the corresponding control signal Vg4 and the control signal Vg6 are high-level signals. The high-level signal represents that the drive switch tube is turned on. At this time, the switch tube S3 and the switch tube S5 are connected in series to withstand the positive polarity AC voltage V grid , so S3 is the high-side switch tube and S5 is the low-side switch tube. The voltage between the first terminal of the switch tube S3 and the second terminal of the switch tube S5 is V grid In the negative half cycle of the output voltage of the cyclic conversion circuit 102, that is, the AC voltage V grid During the negative half cycle, the control module 2031 controls the switch tubes S3 and S5 to remain in the on state, and the corresponding control signals Vg3 and Vg5 are high level signals. At this time, the switch tubes S4 and S6 are connected in series to withstand the negative polarity AC voltage V grid , so S6 is the high-side switch tube and S4 is the low-side switch tube. The voltage between the first terminal of the switch tube S6 and the second terminal of the switch tube S4 is V grid .

[0174] Figure 14 is a schematic diagram of the relevant waveforms of the power converter during the positive half-cycle in the third exemplary embodiment. PWM-S3 and PWM-S5 are reference control signals without dead zones for switches S3 and S5 within control module 2031, respectively. These signals do not directly control the corresponding switches and are generated by control module 2031 based on the specific control requirements of the power conversion circuit. Control module 2031 performs logic or program conversion on the reference control signals PWM-S3 and PWM-S5 with the dead zone signal DS1 to generate control signals Vg3 and Vg5 for switch S3 and S5, respectively. VS3 and VS5 represent the voltage stress waveforms experienced by switches S3 and S5, respectively. Because control signals Vg4 and Vg6 for switch S4 and S6, provided by control module 2031, are constant high-level signals during the positive half-cycle, maintaining switches S4 and S6 in a normally-on state, the relevant waveforms are not shown in Figure 14.

[0175] In the positive half cycle of the output voltage of the cycloconverter circuit 102, it is assumed that the current signal i in FIG. 12 is L When the current is positive to the right, that is, the current flowing into the connection point of the switch tube S3 and the switch tube S5 is positive, the AC voltage V grid When the detection module 207 detects the turn-off edge of the control signal Vg5 of the switch tube S5, the dead zone signal DS1 output by the control module 2031 controls the switch contact of the selection switch ST to be connected to the a terminal. At this time, the current i L In the steady-state operation, as shown by the arrow in FIG12, the current is positive, and the first integrator 2021 immediately senses the sampling signal i corresponding to the rectified current flowing into the connection point of the switch tube S3 and the switch tube S5. rec Integration begins when the first integrated charge value Q int1 Reaching the first charge threshold Q ref1 (The first charge threshold Q ref1 The first charge threshold Q is determined according to the output voltage of the cycloconverter circuit and / or the parasitic capacitance of the switch tube in the cycloconverter circuit and the external parallel capacitance. ref1 With the AC voltage V grid When the voltage across the parasitic capacitor C30 of the switch tube S3 drops to 0V (in real time with changes in the voltage), the control signal Vg3 turns on the switch tube S3, achieving soft switching. The parasitic diode of the switch tube S3 will not conduct, thus avoiding the significant losses caused by the parasitic diode conduction. At this time, the comparison module 206 immediately outputs a high-level signal. The control module 2031 controls the switch contact of the selection switch ST in the first integration circuit 2021 to connect to the b terminal based on the dead-band signal DS1 provided by the output signal of the comparison module 206, thereby discharging the charge on the integration capacitor C3 through the resistor R2.

[0176] When the detection module 207 detects the turn-off edge of the control signal Vg3 of the switch tube S3, the dead zone signal DS1 output by the control module 2031 controls the switch contact of the selection switch ST to be connected to the a terminal. At this time, the current i L The direction is opposite to that shown by the arrow in FIG12 in steady-state operation, that is, the current flowing out of the connection point of the switch tube S3 and the switch tube S5 is a negative current. The first integrator 2021 immediately rectifies the sampling signal i corresponding to the current flowing out of the connection point of the switch tube S3 and the switch tube S5. rec Integration begins when the first integrated charge value Q int1 Reaching the first charge threshold Q ref1 When the voltage across the parasitic capacitor C50 of switch S5 drops to 0V, control signal Vg5 turns on switch S5, achieving zero-voltage turn-on. The parasitic diode of switch S5 is not conducting, thus avoiding the significant losses caused by the conduction of the parasitic diode. At this point, comparison module 206 immediately outputs a high-level signal. Control module 2031, based on the dead-band signal DS1 provided by the output signal of comparison module 206, controls the switch contact of selection switch ST in first integrator circuit 2021 to connect to terminal b, discharging the charge on integration capacitor C3 through resistor R2.

[0177] During the negative half-cycle of the power frequency, the control principle is the same as that of the positive half-cycle of the power frequency. The difference is that the detection module 207 detects the turn-off edge of the control signal of the switch tube S4 or the switch tube S6. After control, the control signals of the switch tube S4 and the switch tube S6 with adaptive dead time are obtained.

[0178] For the inverter circuit 101, the switch tubes S7 and S10 may have a conduction phase shift angle, and the adaptive dead time control of the switch tubes S7 to S10 is the same as the control principle of the secondary side switch tubes S3 to S6. It should be noted that since the resonant current i L It is the current on the secondary side of transformer T. Therefore, for switches S7 to S10, the turns ratio 1:N of transformer T needs to be taken into account before calculating the integrated charge value. ref2 and the input voltage V of the inverter circuit 101 dc Related, the second charge threshold Q ref2 According to the input voltage V of the inverter circuit 101 dc , the turns ratio of the transformer T and / or the parasitic capacitance of the switch tube in the inverter circuit 101 and the external parallel capacitance. For example, when the turn-off edge of the control signal Vg7 of the switch tube S7 is detected, the dead zone signal DS2 controls the second integration circuit 2022 to start sampling the rectified sampling signal i rec Integrate to obtain the second integrated charge value Qint2 , when the second integrated charge value Q int2 Reaching the second charge threshold Q ref2 When V is on, the control signal Vg8 controls the switch tube S8 to turn on, achieving zero voltage turn-on of the switch tube S8 and no parasitic diode conduction loss. The specific control principle is similar to the adaptive dead time control principle of the switch tubes S3 to S6 in Figure 12, and will not be repeated here. However, due to V dc It is a DC voltage, so there is no difference between the positive half cycle and the negative half cycle in control.

[0179] The switches S3 to S6 and S7 to S10 in FIG12 all use adaptive dead-time control, which means that all switches are turned on at zero voltage, and the conduction losses of the parasitic diodes are all zero, thereby reducing the losses of all switches and improving the efficiency of the overall converter.

[0180] When the first integrated charge value Q int1 Reaching the first charge threshold Q ref1 When the control module 2031 controls the first integration circuit 2021 to discharge, the first integrated charge value Q int1 Drops to 0; when the second integrated charge value Q int2 Reaching the second charge threshold Q ref2 When the control module 2031 controls the second integration circuit 2022 to discharge until the second charge threshold Q ref2 Dropped to 0.

[0181] Figures 13 and 14 are schematic diagrams of the control circuit and related waveforms for a common steady-state operation of this exemplary embodiment. However, in actual operation, a special state may exist. Taking the switch tube of the cycloconverter circuit 102 as an example, and taking the positive half cycle as an example, when the switch tube S3 or S5 is turned off, the current i L The direction or positive and negative polarity is the same as that of i in Figure 14 L The direction is opposite, as shown in Figure 15, that is, t6~t7, t8~t9, t 10 ~t 11 The current i corresponding to the time period L The current at this time has no effect on the commutation of the switch tube S3 and the switch tube S5. It is an invalid current and cannot participate in the integration and control of the dead time. The real commutation start time needs to wait until t6, t8, t 10 The absolute value of the current at the turn-off time drops to 0, i.e., t7, t9, t 11 time.

[0182] FIG16 is a schematic structural diagram of a control circuit in a fourth exemplary embodiment, in which the rectifier circuit 204 in the third exemplary embodiment is replaced by a rectifier selection circuit 205 .

[0183] During the positive half-cycle of the power frequency of the output voltage of the cycloconversion circuit 102, when the switch located on the high side of one of the two pairs of switch tubes (switch tube S3 and switch tube S5) is turned off, the selection signal controls the output of the rectifier selection circuit 205 to switch to the sampling signal of the first polarity after rectification; when the switch located on the low side of the pair of switch tubes is turned off, the selection signal controls the output of the rectifier selection circuit 205 to switch to the sampling signal of the second polarity after rectification; during the negative half-cycle of the power frequency of the output voltage of the cycloconversion circuit 102, when the switch located on the high side of the other pair of switch tubes (switch tube S4 and switch tube S6) is turned off, the selection signal controls the output of the rectifier selection circuit 205 to switch to the sampling signal of the second polarity after rectification; when the switch located on the low side of the pair of switch tubes is turned off, the selection signal controls the output of the rectifier selection circuit 205 to switch to the sampling signal of the first polarity after rectification.

[0184] The waveform of the output signal of the rectifier selection circuit 205 is shown in waveform i in FIG. 15. rec As shown. The rectified sampling signal i obtained by the control module 2031 is rec The value during the inactive current time is 0, so it does not affect the control of the integral value and dead time.

[0185] In the fourth exemplary embodiment, the control principle of the output voltage of the frequency conversion circuit 102 in the negative half-cycle of the industrial frequency is the same as that in the positive half-cycle of the industrial frequency. Taking the positive half-cycle of the industrial frequency as an example, when the detection module 207 detects the turn-off edge of the control signal Vg3 of the switch tube S3 or the control signal Vg5 of the switch tube S5, the integration circuit 202 starts integration. When the corresponding charge threshold is reached, the integration ends, and at the same time, the complementary conduction switch tubes are turned on with zero voltage.

[0186] When the switches S7 to S10 of the inverter circuit 101 are working, the current waveform also has the special working state shown in FIG15 , so the control circuit and control method shown in FIG16 are also required. The specific control principle is the same as that of the switches S3 to S6 and will not be repeated here.

[0187] The control method for the power converter in the special working state in the fourth example embodiment is also applicable to the power converter in the normal working state in the third example embodiment.

[0188] The third and fourth exemplary embodiments only take a half-bridge cycloconverter as an example, but are not limited thereto. The cycloconverter circuit 102 may be replaced with a full-bridge type, and the adaptive dead-zone control of the present application may be applied to both.

[0189] Based on the above hardware embodiment, the present application also provides a method for controlling a power converter, as shown in FIG17 , the method comprising:

[0190] S1702: After one of the pair of switching tubes is turned off, obtaining an integrated charge value representing a total charge change of the pair of switching tubes;

[0191] S1704: When the integrated charge value reaches a charge threshold, control the other switch tube in the pair of switch tubes to turn on.

[0192] In this embodiment, after one of a pair of switching tubes is turned off, an integrated charge value representing the total charge change of the pair of switching tubes is obtained, and when the integrated charge value reaches a charge threshold, the other switching tube in the pair is controlled to turn on. This application achieves zero-voltage turn-on of the switching tube, avoids conduction losses in the parasitic diode of the switching tube, and improves the conversion efficiency of the power converter.

[0193] In some embodiments, sampling signals are obtained by sampling electrical signals of a pair of switching tubes;

[0194] The sampling signal is integrated to obtain the integrated charge value.

[0195] In some embodiments, the electrical signal is a current signal representing the magnitude of the current flowing out of and into the connection point of the pair of switching tubes.

[0196] In some embodiments, the method further comprises:

[0197] The turn-off moment of the switch tube is detected, and when it is detected that one switch tube in the switch tube pair is turned off, the sampling signal is integrated.

[0198] In some embodiments, the method further comprises:

[0199] The sampling signal is rectified, and the rectified sampling signal is integrated to obtain the integrated charge value.

[0200] In some embodiments, the method further comprises:

[0201] The sampling signal is rectified, and the rectified sampling signal corresponding to the current flowing out of the connection point or the sampling signal corresponding to the current flowing into the connection point is integrated according to the voltage polarity at both ends of the pair of switching tubes and the turn-off moment of the switching tubes to obtain the integrated charge value.

[0202] In some embodiments, when the voltage across a pair of switch tubes is positive, at the moment when the switch tube on the high side of the pair of switch tubes is turned off, a sampling signal corresponding to the current flowing out of the connection point is integrated; and / or

[0203] At the moment when the switch tube located at the low side of the pair of switch tubes is turned off, a sampling signal corresponding to the current flowing into the connection point is integrated.

[0204] In some embodiments, the method further comprises:

[0205] When the integrated charge value reaches the corresponding charge threshold, discharging begins until the integrated charge value drops to 0.

[0206] The control principle of this method embodiment can refer to the description in the above embodiment, so it will not be repeated here.

[0207] An embodiment of the present application also proposes an inverter, which includes an inverter circuit, a resonant circuit, a cyclotron circuit, and a control circuit connected to the inverter circuit and the cyclotron circuit. The resonant circuit is connected between the inverter circuit and the cyclotron circuit. The cyclotron circuit includes at least two pairs of switching tubes, each pair of switching tubes is complementary conductive, and the first end of one switching tube in each pair of switching tubes is connected to the second end of the other switching tube; the control circuit is used to control the inverter circuit and the cyclotron circuit. After one switching tube in a pair of switching tubes in the cyclotron circuit is turned off, the resonant current of the resonant circuit is sampled and integrated to obtain a first integrated charge value, and when the first integrated charge value reaches a corresponding charge threshold, the other switching tube in the pair of switching tubes is controlled to be turned on.

[0208] In some embodiments, the control circuit comprises:

[0209] a sampling circuit, sampling the resonant current to obtain a sampling signal;

[0210] an integrating circuit, connected to the sampling circuit, integrating the sampling signal to obtain the first integrated charge value;

[0211] A controller is connected to the integration circuit and includes a control module. The control module provides a dead-band signal for controlling the integration circuit and a control signal for controlling the switch tube. When one switch tube in a pair of switch tubes is turned off, the dead-band signal controls the integration circuit to start integrating the sampled signal. When the first integrated charge value reaches a corresponding charge threshold, the control signal controls the other switch tube in the pair of switch tubes to turn on.

[0212] In some embodiments, the control circuit further comprises:

[0213] A detection module, used to detect the turn-off moment of the switch tube and provide a detection signal to the control module;

[0214] A comparison module is configured to compare the first integrated charge value with the charge threshold and output a comparison result to the control module.

[0215] In some embodiments, when the switch tube located on the high side of a pair of switch tubes is turned off, the integration circuit starts to integrate the rectified sampling signal corresponding to the negative polarity resonant current; when the switch tube located on the low side of the pair of switch tubes is turned off, the integration circuit starts to integrate the rectified sampling signal corresponding to the positive polarity resonant current.

[0216] In some embodiments, the control circuit further comprises:

[0217] The rectifier circuit is connected between the sampling circuit and the integration circuit, and is used to rectify the sampling signal and output it to the integration circuit. The integration circuit integrates the rectified sampling signal to obtain the first integrated charge value.

[0218] In some embodiments, the control circuit further comprises:

[0219] A rectifier selection circuit is connected between the sampling circuit and the integration circuit, rectifies the sampling signal, and selects to output the rectified sampling signal corresponding to the negative polarity resonant current or the positive polarity resonant current according to the selection signal provided by the controller. The integration circuit integrates the sampling signal corresponding to the negative polarity resonant current or the sampling signal corresponding to the positive polarity resonant current after rectification to obtain the first integrated charge value.

[0220] In some embodiments, at the turn-off moment of the high-side switch tube in the pair of switch tubes of the cycloconversion circuit, the selection signal controls the output of the rectifier selection circuit to switch to a sampling signal corresponding to the rectified negative resonant current;

[0221] At the turn-off moment of the switch tube located on the low side of the pair of switch tubes, the selection signal controls the output of the rectification selection circuit to switch to a rectified sampling signal corresponding to the positive polarity resonant current.

[0222] In some embodiments, the rectification selection circuit includes:

[0223] a separation unit, configured to separate the positive and negative polarities of the sampling signal output by the sampling circuit to obtain a sampling signal corresponding to the negative polarity resonant current and a sampling signal corresponding to the positive polarity resonant current;

[0224] a rectifier unit, configured to rectify the sampling signal corresponding to the negative polarity resonant current and the sampling signal corresponding to the positive polarity resonant current respectively;

[0225] The selection unit is configured to select and output the rectified sampling signal corresponding to the negative polarity resonant current or the sampling signal corresponding to the positive polarity resonant current according to the selection signal.

[0226] In some embodiments, the cyclic conversion circuit includes two pairs of switching tubes. In a positive half-cycle of the power frequency of the output voltage of the cyclic conversion circuit, when the switch tube located on the high side of one of the two pairs of switching tubes is turned off, the integration circuit starts integrating the rectified sampling signal corresponding to the negative polarity resonant current; when the switch tube located on the low side of the pair of switching tubes is turned off, the integration circuit starts integrating the rectified sampling signal corresponding to the positive polarity resonant current.

[0227] During the negative half-cycle of the industrial frequency of the output voltage of the cycloconversion circuit, at the moment when the switch tube located on the high side of the other pair of switch tubes in the two pairs of switch tubes is turned off, the integration circuit starts to integrate the sampling signal corresponding to the rectified negative polarity resonant current; at the moment when the switch tube located on the low side of the pair of switch tubes is turned off, the integration circuit starts to integrate the sampling signal corresponding to the rectified positive polarity resonant current.

[0228] In some embodiments, when the first integrated charge value reaches a corresponding charge threshold, the control module controls the integration circuit to discharge until the first integrated charge value drops to zero.

[0229] In some embodiments, the integration circuit comprises:

[0230] The first integration circuit is used to integrate the rectified sampling signal according to the first dead zone signal to obtain the first integrated charge value, and the first dead zone signal is generated by the control module according to the turn-off moment of the switch tube in the cyclotron conversion circuit and the comparison result of the first integrated charge value and the first charge threshold.

[0231] In some embodiments, the inverter circuit includes at least one pair of switching tubes. After one of the pair of switching tubes in the inverter circuit is turned off, the integration circuit starts to integrate the sampling signal to obtain a second integrated charge value, and when the second integrated charge value reaches a second charge threshold, the control module controls the other switch tube in the pair of switching tubes to turn on.

[0232] The integration circuit also includes: a second integration circuit, used to integrate the rectified sampling signal according to a second dead zone signal to obtain a second integrated charge value, and the second dead zone signal is generated by the control module according to the turn-off moment of the switch tube in the inverter circuit and the comparison result of the second integrated charge value and the second charge threshold.

[0233] In some embodiments, when the second integrated charge value reaches a second charge threshold, the control module controls the second integration circuit to discharge until the second integrated charge value drops to zero.

[0234] In some embodiments, the power conversion circuit further includes a transformer connected between the inverter circuit and the cycloconversion circuit;

[0235] The first charge threshold is determined according to the output voltage of the cyclotron conversion circuit and / or the parasitic capacitance of the switch tube in the cyclotron conversion circuit and the external parallel capacitance;

[0236] The second charge threshold is determined according to the input voltage of the inverter circuit, the turns ratio of the transformer and / or the parasitic capacitance of the switch tube in the inverter circuit and the external parallel capacitance.

[0237] In some embodiments, the cycloconversion circuit includes two pairs of switching transistors connected in opposite directions, one pair of switching transistors including a first switching transistor and a second switching transistor, the first switching transistor and the second switching transistor being complementary to each other, and the other pair of switching transistors including a third switching transistor and a fourth switching transistor, the third switching transistor and the fourth switching transistor being complementary to each other. The second end of the first switching transistor is connected to the first end of the second switching transistor via the third switching transistor, the second end of the fourth switching transistor is connected to the first end of the third switching transistor via the second switching transistor, and the connection point between the second and fourth switching transistors is connected to the resonant circuit.

[0238] After the first switch tube is turned off, the positive polarity resonant current is sampled and integrated, and when the first integrated charge value reaches the corresponding charge threshold, the second switch tube is controlled to be turned on; after the second switch tube is turned off, the negative polarity resonant current is sampled and integrated, and when the first integrated charge value reaches the corresponding charge threshold, the first switch tube is controlled to be turned on;

[0239] After the third switch tube is turned off, the positive polarity resonant current is sampled and integrated to obtain a first integrated charge value, and when the first integrated charge value reaches a corresponding charge threshold, the fourth switch tube is controlled to be turned on; after the second switch tube is turned off, the negative polarity resonant current is sampled and integrated, and when the first integrated charge value reaches a corresponding charge threshold, the third switch tube is controlled to be turned on.

[0240] In some embodiments, the cycloconverter circuit is a half-bridge cycloconverter or a full-bridge cycloconverter.

[0241] In some embodiments, the cycloconversion circuit is a three-phase topology or a single-phase topology.

[0242] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0243] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A power converter, characterized in that: The power converter comprises: The power conversion circuit comprises at least one pair of switch tubes, wherein a first end of one switch tube in each pair of switch tubes is connected to a second end of another switch tube; A control circuit is connected to the power conversion circuit and is used to control the power conversion circuit. After one switch tube in a pair of switch tubes is turned off, an integrated charge value representing the total charge change of the pair of switch tubes is obtained, and when the integrated charge value reaches a corresponding charge threshold, the other switch tube in the pair of switch tubes is controlled to be turned on.

2. The power converter according to claim 1, wherein: The control circuit comprises: A sampling circuit samples the electrical signals of a pair of switch tubes to obtain a sampling signal; an integrating circuit, connected to the sampling circuit, integrating the sampling signal to obtain the integrated charge value; A controller is connected to the integration circuit and includes a control module. The control module provides a dead zone signal for controlling the integration circuit and a control signal for controlling at least one pair of switch tubes. When one switch tube in a pair of switch tubes is turned off, the dead zone signal controls the integration circuit to start integrating the sampling signal, and when the integrated charge value reaches a charge threshold, the control signal controls the other switch tube in the pair of switch tubes to turn on.

3. The power converter according to claim 2, wherein: The electrical signal is a current signal that characterizes the magnitude of the current flowing out and into the connection point of the pair of switch tubes.

4. The power converter according to claim 3, wherein: The control circuit further comprises: A detection module, used to detect the turn-off moment of the switch tube and provide a detection signal to the control module; A comparison module is used to compare the integrated charge value with the charge threshold and output the comparison result to the control module.

5. The power converter according to claim 3, wherein: The control circuit further comprises: The rectifier circuit is connected between the sampling circuit and the integration circuit, and is used for rectifying the sampling signal and outputting it to the integration circuit. The integration circuit integrates the rectified sampling signal to obtain the integrated charge value.

6. The power converter according to claim 3, wherein: The control circuit further comprises: A rectifier selection circuit is connected between the sampling circuit and the integration circuit, rectifies the sampling signal, and selects to output a rectified sampling signal of a first polarity corresponding to the current flowing out of the connection point or a sampling signal of a second polarity corresponding to the current flowing into the connection point according to a selection signal provided by the controller. The integration circuit integrates the rectified sampling signal of the first polarity or the sampling signal of the second polarity to obtain the integrated charge value.

7. The power converter according to claim 6, wherein: When the voltage across a pair of switch tubes is a DC voltage, at the moment when the switch tube located at the high side of the pair of switch tubes is turned off, the selection signal controls the output of the rectification selection circuit to switch to a sampling signal of the first polarity after rectification; and / or At the moment when the switch tube located at the low side of the pair of switch tubes is turned off, the selection signal controls the output of the rectification selection circuit to switch to a rectified sampling signal of the second polarity.

8. The power converter according to claim 6, wherein: When the voltage across a pair of switch tubes is an AC voltage, in the positive half cycle of the power frequency, at the moment when the high-side switch tube in the pair of switch tubes is turned off, the selection signal controls the output of the rectification selection circuit to switch to a sampling signal of the first polarity after rectification; At the moment when the low-side switch in the pair of switch tubes is turned off, the selection signal controls the output of the rectification selection circuit to switch to a rectified sampling signal of the second polarity.

9. The power converter according to claim 6, wherein: The rectification selection circuit comprises: a separation unit, configured to separate the positive and negative polarities of the sampling signal output by the sampling circuit to obtain a sampling signal of a first polarity corresponding to the current flowing out of the connection point and a sampling signal of a second polarity corresponding to the current flowing into the connection point; A rectifying unit, used for rectifying the sampling signal of the first polarity and the sampling signal of the second polarity respectively; The selection unit is used to select and output the rectified sampling signal of the first polarity or the sampling signal of the second polarity according to the selection signal.

10. The power converter according to claim 5 or 6, wherein: The power conversion circuit comprises: An inverter circuit, wherein the inverter circuit is used to invert direct current into alternating current; A resonant circuit connected to the inverter circuit; A cycloconversion circuit, connected to the resonant circuit, comprising two pairs of switch tubes connected in reverse order for performing AC-AC conversion; After one of a pair of switch tubes in the frequency conversion circuit is turned off, the integration circuit obtains a first integrated charge value representing the total amount of charge change of the pair of switch tubes, and when the first integrated charge value reaches a first charge threshold, the control module controls the other switch tube in the pair of switch tubes to turn on.

11. The power converter according to claim 10, wherein: In the positive half cycle of the power frequency of the output voltage of the cycloconversion circuit, at the moment when the switch tube located at the high side of one pair of switch tubes in the two pairs of switch tubes is turned off, the integration circuit starts to integrate the sampling signal corresponding to the rectified current flowing out of the connection point of the pair of switch tubes; at the moment when the switch tube located at the low side of the pair of switch tubes is turned off, the integration circuit starts to integrate the sampling signal corresponding to the rectified current flowing into the connection point of the pair of switch tubes; In the negative half cycle of the industrial frequency of the output voltage of the cycloconversion circuit, at the moment when the switch tube located on the high side of the other pair of switch tubes in the two pairs of switch tubes is turned off, the integration circuit starts to integrate the sampling signal corresponding to the rectified current flowing out of the connection point of the pair of switch tubes; at the moment when the switch tube located on the low side of the pair of switch tubes is turned off, the integration circuit starts to integrate the sampling signal corresponding to the rectified current flowing into the connection point of the pair of switch tubes.

12. The power converter according to claim 2, wherein: When the integrated charge value reaches the corresponding charge threshold, the control module controls the integration circuit to discharge until the integrated charge value drops to zero.

13. The power converter according to claim 10, wherein: The inverter circuit includes at least one pair of switch tubes. After one switch tube in the pair of switch tubes in the inverter circuit is turned off, the integration circuit obtains a second integrated charge value representing the total amount of charge change of the pair of switch tubes, and when the second integrated charge value reaches a second charge threshold, the control module controls the other switch tube in the pair of switch tubes to turn on.

14. The power converter according to claim 13, wherein: The integration circuit comprises: a first integration circuit, used for integrating the rectified sampling signal according to a first dead zone signal to obtain the first integrated charge value, wherein the first dead zone signal is generated by the control module according to the turn-off time of the switch tube in the frequency conversion circuit and the comparison result of the first integrated charge value and the first charge threshold; The second integration circuit is used to integrate the rectified sampling signal according to the second dead zone signal to obtain the second integrated charge value, and the second dead zone signal is generated by the control module according to the turn-off time of the switch tube in the inverter circuit and the comparison result of the second integrated charge value and the second charge threshold.

15. The power converter according to claim 13, wherein: The power conversion circuit also includes a transformer connected between the inverter circuit and the cycloconversion circuit; The first charge threshold is determined according to the output voltage of the frequency conversion circuit and / or the parasitic capacitance of the switch tube in the frequency conversion circuit and the external parallel capacitance; The second charge threshold is determined according to the input voltage of the inverter circuit, the turns ratio of the transformer and / or the parasitic capacitance of the switch tube in the inverter circuit and the external parallel capacitance.

16. The power converter according to claim 14, wherein: When the first integrated charge value reaches a first charge threshold, the control module controls the first integration circuit to discharge until the first integrated charge value drops to 0; When the second integrated charge value reaches a second charge threshold, the control module controls the second integration circuit to discharge until the second integrated charge value drops to zero.

17. The power converter according to claim 1, wherein: The power conversion circuit is one of a BUCK type conversion circuit, a BOOST type conversion circuit, an LLC type conversion circuit, a dual active bridge conversion circuit, a cycloconversion circuit, a half-bridge circuit, and a full-bridge circuit.

18. The power converter according to claim 1, wherein: The power converter is a DC-DC power converter, a DC-AC power converter, an AC-AC power converter, or an AC-DC converter.

19. A control method for a power converter, used for the power converter according to any one of claims 1 to 18, characterized in that: The method comprises: After one of the pair of switch tubes is turned off, an integrated charge value representing a total charge change of the pair of switch tubes is obtained; When the integrated charge value reaches a corresponding charge threshold, the other switch tube in the pair of switch tubes is controlled to be turned on.

20. The method according to claim 19, wherein: Sampling the electrical signals of a pair of switch tubes to obtain sampling signals; The sampling signal is integrated to obtain the integrated charge value.

21. The method according to claim 20, wherein: The electrical signal is a current signal that characterizes the magnitude of the current flowing out and into the connection point of the pair of switch tubes.

22. The method according to claim 21, wherein: The method further comprises: The switch-off time of the switch tube is detected, and when it is detected that one switch tube in the switch tube pair is turned off, the sampling signal is integrated.

23. The method according to claim 21, wherein: The method further comprises: The sampling signal is rectified, and the rectified sampling signal is integrated to obtain the integrated charge value.

24. The method according to claim 21, wherein: The method further comprises: The sampling signal is rectified, and the rectified sampling signal corresponding to the current flowing out of the connection point or the sampling signal corresponding to the current flowing into the connection point is integrated according to the voltage polarity at both ends of the pair of switch tubes and the turn-off moment of the switch tubes to obtain the integrated charge value.

25. The method according to claim 21, wherein: When the voltage across a pair of switch tubes is positive, at the moment when the switch tube located at the high side of the pair of switch tubes is turned off, integrating the sampling signal corresponding to the current flowing out of the connection point; and / or At the moment when the switch tube located at the low side of the pair of switch tubes is turned off, the sampling signal corresponding to the current flowing into the connection point is integrated.

26. The method of claim 19, wherein: The method further comprises: When the integrated charge value reaches the corresponding charge threshold, discharging begins until the integrated charge value drops to zero.

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