Control method and system for resonant converter

Abstract

A control method and system for a resonant converter. The control method for a resonant converter comprises: in each switching cycle, determining a target power value on the basis of an input power control amount and a compensation amount corresponding to a bridge leg (S101); on the basis of the target power value, an input voltage, circuit parameters of the resonant converter, and the current operating mode of a full-bridge inverter module, determining a target slope control amount corresponding to a counter which corresponds to a switching transistor (S102); determining a comparison threshold on the basis of the target slope control amount, the current count value of the counter which corresponds to the switching transistor, and a DC bias voltage of a resonant capacitor corresponding to the current operating mode, wherein the counter starts counting using the DC bias voltage as an initial value in each switching cycle until the actual voltage of the resonant capacitor is equal to the comparison threshold (S103); and determining a control signal on the basis of the actual voltage of the resonant capacitor and the comparison threshold, and controlling the switching transistor on the basis of the control signal (S104).

Description

Control method and system of resonant converter

[0001] This application claims priority to the Chinese patent application No. 202411277131.4, filed on September 12, 2024, with the Chinese Patent Office, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of resonant converter, for example, to a control method and system of resonant converter. BACKGROUND

[0003] The direct current-direct current converter (DC-DC) usually adopts a Buck circuit or a flyback circuit. By controlling the duty cycle of the control signal of the switching transistor in the DC-DC converter, the output gain of the DC-DC converter can be controlled. However, the Buck circuit or the flyback circuit is difficult to realize zero-voltage zero-current switching and is not suitable for high-frequency design. The resonant DC-DC converter is easy to realize zero-voltage zero-current switching and is convenient for high-frequency design. By controlling the frequency of the control signal of the switching transistor, the resonant DC-DC converter can realize the control of the output gain. However, the high conversion efficiency working frequency range is relatively narrow, and when the input and output voltage range is wide, the conversion efficiency is low.

[0004] The full-bridge resonant converter includes a full-bridge conversion circuit, and the working mode of the full-bridge conversion circuit includes a full-bridge working mode and a half-bridge working mode. The conversion gain of the full-bridge conversion circuit in the full-bridge working mode is one time of the conversion gain of the full-bridge conversion circuit in the half-bridge working mode at the same switching frequency. When the working mode of the full-bridge conversion circuit is switched, it is necessary to keep the output voltage stable. For example, the papers Modulation Transition Methods Based on Trajectory Control for LLC Resonant Converters Operating in Wide Input- and / or Output-Voltage Range (IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 37, NO. 12, DECEMBER 2022) and Wide Voltage Input Full Bridge (FB) / Half Bridge (HB) Morphing-Based LLC DC-DC Converter Using Numerical Optimal Trajectory Control (IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 70, NO. 4, APRIL 2023) disclose an optimal trajectory control method based on direct frequency or duty cycle control, that is, the switching frequency of the switching transistor in the full-bridge conversion circuit or the duty cycle of the control signal of the switching transistor is controlled, and the output voltage is adjusted to keep the output voltage stable.

[0005] However, controlling the switching frequency of the switching transistor or the duty cycle of the control signal of the switching transistor in the full-bridge conversion circuit requires complex calculations, has high requirements for the accuracy of the parameters of the resonant element, and has poor dynamic performance when directly controlling the switching frequency. For example, in the paper Bang-Bang Charge Control for LLC Resonant Converters (IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 2, FEBRUARY 2015), in order to obtain high dynamic performance of the resonant DC-DC converter, a current-mode control method using resonant cavity state (resonant capacitor voltage or resonant capacitor current) feedback is adopted, that is, the switching time of the switching transistor is controlled through the feedback voltage or feedback current of the resonant capacitor in the resonant circuit, and then the output voltage of the resonant converter is controlled. However, these methods cannot be directly used for transient control during mode switching of the resonant topology, and have poor transient control performance during the operation of the resonant converter, and cannot well control the output of the resonant converter. SUMMARY

[0006] The present application provides a control method and system of a resonant converter to solve the problem that the existing control method of the resonant converter has poor transient control performance during the operation of the resonant converter, cannot realize transient control during mode switching, and cannot well control the output of the resonant converter.

[0007] The present application provides a control method of a resonant converter, the resonant converter comprising a full-bridge inverter module, a resonant conversion module and a rectifier module; the full-bridge inverter module is connected with the resonant conversion module, and the resonant conversion module is connected with the rectifier module; the full-bridge inverter module comprises at least two bridge arms; the resonant conversion module comprises a resonant capacitor; the method is executed by a control system of the resonant converter; the control system is connected with the control electrode of the switching transistor of each of the at least two bridge arms respectively, and the control system comprises a counter; the method comprises:

[0008] In each switching period, the target power value of each of the bridge arms is determined according to the input power control amount and the compensation amount corresponding to each of the bridge arms;

[0009] The target slope control amount corresponding to the counter corresponding to the switching transistor is determined according to the target power value, the input voltage, the circuit parameters of the resonant converter and the current working mode of the full-bridge inverter module; wherein the working mode comprises a full-bridge working mode or a half-bridge working mode;

[0010] determine a comparison threshold value according to the target slope control amount, a current count value of a counter corresponding to the switching transistor, and a DC offset voltage of the resonant capacitor corresponding to a current working mode; wherein the counter starts counting with the DC offset voltage as an initial value in each switching period, until an actual voltage of the resonant capacitor is equal to the comparison threshold value;

[0011] determine a control signal according to the actual voltage of the resonant capacitor and the comparison threshold value, and control the switching transistor according to the control signal.

[0012] Embodiments of the present application provide a control system of a resonant converter, the resonant converter comprising a full-bridge inverter module, a resonant conversion module, and a rectifier module; the full-bridge inverter module is connected with the resonant conversion module, and the resonant conversion module is connected with the rectifier module; the full-bridge inverter module comprises at least two bridge arms; the resonant conversion module comprises a resonant capacitor; the control system is connected with control electrodes of switching transistors of the at least two bridge arms respectively; the control system comprises a counter; and the control system comprises:

[0013] a target power value determination module configured to determine a target power value corresponding to each of the bridge arms according to an input power control amount corresponding to each of the bridge arms and a compensation amount in each switching period;

[0014] a target slope control amount determination module connected with the target power value determination module and configured to determine a target slope control amount corresponding to a counter of the switching transistor according to the target power value, an input voltage, circuit parameters of the resonant converter, and a current working mode of the full-bridge inverter module; wherein the working mode comprises a full-bridge working mode or a half-bridge working mode;

[0015] a comparison threshold value determination module connected with the target slope control amount determination module and configured to determine a comparison threshold value according to the target slope control amount, a current count value of a counter corresponding to the switching transistor, and a DC offset voltage of the resonant capacitor corresponding to a current working mode; wherein the counter starts counting with the DC offset voltage as an initial value in each switching period, until an actual voltage of the resonant capacitor is equal to the comparison threshold value;

[0016] a control module connected with the comparison threshold value determination module and configured to determine a control signal according to the actual voltage of the resonant capacitor and the comparison threshold value, and control the switching transistor according to the control signal. BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG. 1 is a circuit structure schematic diagram of a resonant converter provided by embodiments of the present application;

[0018] Fig. 2 is a schematic diagram of a first working mode of the resonant converter in Fig. 1;

[0019] Fig. 3 is a schematic diagram of a second working mode of the resonant converter in Fig. 1;

[0020] Fig. 4 is a schematic diagram of a third working mode of the resonant converter in Fig. 1;

[0021] Fig. 5 is a schematic diagram of a fourth working mode of the resonant converter in Fig. 1;

[0022] Fig. 6 is a flow chart of a control method of a resonant converter according to an embodiment of the present application;

[0023] Fig. 7 is a flow chart of a control method of a resonant converter according to another embodiment of the present application;

[0024] Fig. 8 is a flow chart of a control method of a resonant converter according to yet another embodiment of the present application;

[0025] Fig. 9 is a schematic diagram of time-domain working waveforms of a resonant converter according to an embodiment of the present application;

[0026] Fig. 10 is a schematic diagram of state plane running track of a resonant converter switching from full-bridge working mode to half-bridge working mode according to an embodiment of the present application;

[0027] Fig. 11 is a schematic diagram of state plane running track of a resonant converter switching from half-bridge working mode to full-bridge working mode according to an embodiment of the present application;

[0028] Fig. 12 is a schematic diagram of a control system of a resonant converter according to an embodiment of the present application;

[0029] Fig. 13 is a schematic diagram of a control system of a resonant converter according to another embodiment of the present application;

[0030] Fig. 14 is a schematic diagram of a circuit structure of a full-bridge inverter module according to an embodiment of the present application;

[0031] Fig. 15 is a schematic diagram of a circuit structure of a resonant module according to an embodiment of the present application;

[0032] Fig. 16 is a schematic diagram of a circuit structure of another resonant module according to an embodiment of the present application;

[0033] Fig. 17 is a schematic diagram of a circuit structure of a rectifier module according to an embodiment of the present application;

[0034] Fig. 18 is a schematic diagram of a circuit structure of another rectifier module according to an embodiment of the present application;

[0035] Fig. 19 is a schematic diagram of a circuit structure of yet another rectifier module according to an embodiment of the present application;

[0036] Fig. 20 is a schematic diagram of a circuit structure of another rectifier module according to an embodiment of the present application;

[0037] Fig. 21 is a schematic diagram of a circuit structure of another rectifier module according to an embodiment of the present application;

[0038] Fig. 22 is a schematic diagram of a circuit structure of another rectifier module according to an embodiment of the present application;

[0039] Fig. 23 is a waveform diagram of output voltage and output current of a resonant converter according to an embodiment of the present application;

[0040] Fig. 24 is a partial enlarged view of output voltage and output current of a resonant converter according to an embodiment of the present application;

[0041] Fig. 25 is a schematic diagram of working waveforms when a resonant converter switches from a half-bridge working mode to a full-bridge working mode according to an embodiment of the present application;

[0042] Fig. 26 is a schematic diagram of working waveforms when a resonant converter switches from a full-bridge working mode to a half-bridge working mode according to an embodiment of the present application. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work should fall within the scope of protection of the present application.

[0044] The terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to the process, method, product, or device.

[0045] The control method of the existing resonant converter has poor transient control performance in the working process of the resonant converter, and cannot well control the output of the resonant converter. Embodiments of the present application provide a control method of a resonant converter. The resonant converter can include a full-bridge inverter module, a resonant conversion module and a rectification module. The full-bridge inverter module is connected with the resonant conversion module, and the resonant conversion module is connected with the rectification module. The full-bridge inverter module includes at least two bridge arms. For example, the full-bridge inverter module can include a series full-bridge inverter circuit or a parallel full-bridge inverter circuit, and the embodiments are not limited thereto. The resonant conversion module can include an LLC resonant network formed by connecting a resonant inductor, an excitation inductor and a resonant capacitor. The resonant conversion module further includes a transformer. The rectification module includes a series full-bridge rectification circuit, a parallel full-bridge rectification circuit or a half-bridge rectification circuit.

[0046] For example, FIG. 1 is a schematic diagram of a circuit structure of a resonant converter provided by embodiments of the present application. Referring to FIG. 1, the resonant converter includes a full-bridge inverter module 11, a resonant conversion module 12 and a rectification module 13. The full-bridge inverter module 11 is connected with the resonant conversion module 12, and the resonant conversion module 12 is connected with the rectification module 13. As shown in FIG. 1, the full-bridge inverter module 11 includes a first bridge arm 111 and a second bridge arm 112. The input voltage of the full-bridge inverter module 11 is , the first input voltage of the first bridge arm 111 is , and the second input voltage of the second bridge arm 112 is . The output voltage of the resonant converter is , and the output voltage includes a first output voltage and a second output voltage .

[0047] The first bridge arm 111 includes a first switching transistor and a second switching transistor , the second bridge arm 112 includes a third switching transistor and a fourth switching transistor , and the first switching transistor , the second switching transistor , the third switching transistor and the fourth switching transistor are connected as a series inverter circuit. The full-bridge inverter module 11 further includes an input filter capacitor, which includes a first input filter capacitor and a second input filter capacitor .

[0048] The resonant conversion module 12 includes a resonant inductor , an excitation inductor and a resonant capacitor And transformer T, resonant inductor Magnetizing inductor and resonant capacitor A resonant cavity (resonant network) is formed. The resonant network is connected to the primary winding of transformer T. Rectifier module 13 is connected to the secondary winding of transformer T. Rectifier module 13 includes a first rectifier transistor. Second rectifier transistor Third rectifier transistor Fourth rectifier transistor First output capacitor Second output capacitor The first rectifier transistor Second rectifier transistor Third rectifier transistor Fourth rectifier transistor First output capacitor Second output capacitor The circuit is connected to form a parallel full-bridge rectifier circuit.

[0049] Figure 2 is a schematic diagram of the first operating mode of the resonant converter in Figure 1. As shown in Figure 2, in the first operating mode, the first switching transistor of the resonant converter... and the third switching transistor Turn on, second switching transistor and the fourth switching transistor When switched off, charge is transferred between the port of the first bridge arm 111 and the resonant cavity. That is, charge flows from the input terminal of the first bridge arm 111 through the first switching transistor. and the resonant cavity, and through the third switching transistor and the first input filter capacitor Return to the input port of the first bridge arm 111.

[0050] Figure 3 is a schematic diagram of the second operating mode of the resonant converter in Figure 1. As shown in Figure 3, in the second operating mode, the second switching transistor of the resonant converter... and the fourth switching transistor Turn on, first switching transistor and the third switching transistor When turned off, charge is transferred between the port of the second bridge arm 12 and the resonant cavity.

[0051] Figure 4 is a schematic diagram of the third operating mode of the resonant converter in Figure 1. As shown in Figure 4, in the third operating mode, the second switching transistor... and the third switching transistor Turn on, first switching transistor and the fourth switch transistor off, the charge is transferred between the energy storage element (resonant inductor , excitation inductor and the resonant capacitor .

[0052] Fig. 5 is a schematic diagram of a fourth working mode of the resonant converter in Fig. 1, as shown in Fig. 5, the first switch transistor and the fourth switch transistor on, the second switch transistor and the third switch transistor off, the charge is transferred between the port after the first bridge arm 111 and the second bridge arm 112 in series and the resonant cavity.

[0053] The working modes of the full-bridge inverter module 11 include a full-bridge working mode and a half-bridge working mode. When the full-bridge inverter module 11 works in the full-bridge working mode, the full-bridge inverter module 11 executes in the sequence of the third working mode, the bridge arm power balance adjustment mode (the first working mode or the second working mode), the fourth working mode, the bridge arm power balance adjustment mode (the first working mode or the second working mode), the third working mode in a cycle. The bridge arm power balance adjustment mode can adjust the input power difference of the first bridge arm 111 and the second bridge arm 112, and can realize the input voltage balance control of the first bridge arm 111 and the second bridge arm 112.

[0054] When the full-bridge inverter module 11 works in the half-bridge working mode, the working modes executed can be determined according to actual application requirements. For example, when the working mode is the high-voltage half-bridge mode of the first bridge arm 111, the full-bridge inverter module 11 executes in the sequence of the fourth working mode, the second working mode, the fourth working mode in a cycle. When the working mode is the low-voltage half-bridge mode of the first bridge arm 111, the full-bridge inverter module 11 executes in the sequence of the first working mode, the third working mode, the first working mode in a cycle. When the working mode is the high-voltage half-bridge mode of the second bridge arm 112, the full-bridge inverter module 11 executes in the sequence of the fourth working mode, the first working mode, and the fourth working mode in a cycle. When the working mode is the low-voltage half-bridge mode of the second bridge arm 112, the full-bridge inverter module 11 executes in the sequence of the second working mode, the third working mode, and the second working mode in a cycle. When the working mode is the high-voltage interleaved half-bridge mode, the full-bridge inverter module 11 executes in the sequence of the fourth working mode, the first working mode, the fourth working mode, the second working mode, and the fourth working mode in a cycle. When the working mode is the low-voltage interleaved half-bridge mode, the full-bridge inverter module 11 executes in the sequence of the first working mode, the third working mode, the second working mode, the third working mode, and the first working mode in a cycle.

[0055] In order to adapt to different requirements, it is necessary to switch the working mode of the resonant converter, for example, from full-bridge working mode to half-bridge working mode, or from half-bridge working mode to full-bridge working mode.

[0056] The embodiment of the present application provides a control method of a resonant converter, the control method of the resonant converter is executed by a control system of the resonant converter, and the control system of the resonant converter is connected with control electrodes of switching transistors of bridge arms of a full-bridge inverter module. The control system of the resonant converter comprises a counter, for example, the counter is arranged in one-to-one correspondence with the switching transistors.

[0057] FIG. 6 is a flowchart of the control method of the resonant converter provided by the embodiment of the present application, referring to FIG. 6, the control method of the resonant converter comprises the following steps.

[0058] In each switching cycle, a target power value corresponding to each bridge arm is determined according to an input power control amount and a compensation amount corresponding to each bridge arm.

[0059] The switching cycle can be the time length from the start of conduction of any one switching transistor to the next conduction. Each bridge arm corresponds to an input voltage, and each bridge arm corresponds to an input power. The input power control amount is a control amount for controlling the input power of the bridge arm, and the input power control amount can be input to an output voltage closed-loop controller by inputting input electrical parameters and output electrical parameters of the resonant converter. The compensation amount can adjust the input power control amount, so as to improve the accuracy of the determination of the target power value. For example, the compensation amount can be a preset value. For example, the input electrical parameters comprise the input voltage and / or the input current of the bridge arm, and the output electrical parameters comprise the output voltage and / or the output current of the resonant converter. The target power value is a target value of the input power of the bridge arm, and each bridge arm corresponds to a target power value.

[0060] By determining the target power value according to the input power control amount and the compensation amount corresponding to the bridge arm, direct control of the input power can be realized, so that it is not necessary to adjust the duty cycle of the control signal of the switching transistor in the bridge arm, complex calculation is not necessary, and the parameter accuracy requirement of the resonant network is low.

[0061] In addition, by determining the target power value in each switching cycle, for example, at the start of each switching cycle, the input power of the bridge arm is controlled according to the target power value, so that the input power of the bridge arm can be adjusted in each switching cycle, and the output voltage of the resonant converter is controlled, which is beneficial to guarantee the stability of the output voltage of the resonant converter in each switching cycle. Therefore, even if the working mode is switched before the current switching cycle, the stability of the output voltage of the resonant converter can be guaranteed.

[0062] S102, determine a target slope control quantity corresponding to a counter of a switch transistor according to the target power value, the input voltage, circuit parameters of the resonant converter and a current working mode of the full-bridge inverter module; wherein the working mode comprises a full-bridge working mode or a half-bridge working mode.

[0063] Each switch transistor corresponds to a counter. The counter can count according to a count step value, for example, count up by one every count step value of time, and then the counter can output a slope signal that changes over time. In some other embodiments, the counter can also be replaced by a slope signal generator. The target slope control quantity is a target slope control quantity of a comparison threshold value, and each counter corresponds to a comparison threshold value, that is, each counter corresponds to a target slope control quantity. The target slope control quantity is related to the target power value, and by determining the target slope control quantity, the slope control quantity corresponding to the counter is the target slope control quantity, so that the input power of the corresponding bridge arm can reach the target power value, thereby achieving control of the input power.

[0064] The input voltage is the input voltage of the bridge arm, and the circuit parameters of the resonant converter can be the electrical parameters of the devices in the resonant converter.

[0065] By determining the target slope control quantity corresponding to the counter, the product of the count value of the counter and the target slope control quantity can be obtained. Therefore, the comparison threshold value is dynamically changing, and according to the comparison threshold value, it can be determined whether to control the corresponding switch transistor to turn off, so as to control the output voltage of the resonant converter, which is conducive to ensuring the stability of the output voltage and improving the transient control during the operation of the resonant converter, and the output of the resonant converter can be better controlled.

[0066] In addition, the target slope control quantity is determined according to the current working mode of the full-bridge inverter module, different working modes correspond to different target slope control quantities, and when the working mode is switched, the target slope control quantity corresponding to the current working mode can be determined, so that the target slope control quantity corresponding to the updated working mode can be determined when the working mode is switched, so that the comparison threshold value determined according to the target slope control quantity corresponds to the updated working mode, and the transient control during the working mode switching process of the resonant converter is realized. For example, the target slope control quantity corresponding to the half-bridge working mode is twice the target slope control quantity corresponding to the full-bridge working mode, and it can also be other relationships, and the present embodiment is not limited thereto.

[0067] S103, determine a comparison threshold value according to the target slope control quantity, a current count value of the counter corresponding to the switch transistor and a direct current offset voltage of the resonant capacitor corresponding to the current working mode; wherein the counter starts counting with the direct current offset voltage as the initial value in each switching period, and the actual voltage of the resonant capacitor is equal to the comparison threshold value.

[0068] The full-bridge inverter module can convert DC to AC, and the voltage of the resonant capacitor is AC voltage, which is approximately sinusoidal, and the DC offset voltage is the offset distance of the sinusoidal wave, that is, the voltage of the resonant capacitor changes around the DC offset voltage, and the counter also starts counting from the initial value of the DC offset voltage.

[0069] When the comparison threshold value calculated by the counting value of the counter corresponding to the switch transistor of one bridge arm is equal to the actual voltage of the resonant capacitor, the counter stops counting, the counter corresponding to the other switch transistor of the bridge arm starts counting from the initial value of the DC offset voltage, and the counting value of the counter corresponding to the other switch transistor is calculated until the comparison threshold value is equal to the actual voltage of the resonant capacitor.

[0070] The target slope control quantity can be used as the slope, the counting value of the counter is the variable, and the DC offset voltage of the resonant capacitor is the intercept. Therefore, the curve corresponding to the comparison threshold value calculated according to the target slope control quantity, the current counting value of the counter corresponding to the switch transistor, and the DC offset voltage of the resonant capacitor corresponding to the current working mode is a straight line, and the straight line changes simultaneously with the AC voltage of the resonant capacitor.

[0071] In addition, the DC offset voltage of the resonant capacitor corresponding to different working modes is different, and by determining the DC offset voltage of the resonant capacitor according to the current working mode, the calculated comparison threshold value can be applied to different working modes, so that the control of the switch transistor can be realized even if the working mode is switched.

[0072] S104, determining a control signal according to the actual voltage of the resonant capacitor and the comparison threshold value, and controlling the switch transistor according to the control signal.

[0073] The control signal is determined according to the actual voltage of the resonant capacitor and the comparison threshold value, so that the corresponding switch transistor can be controlled. For example, when the comparison threshold value calculated by the counting value of the counter corresponding to one switch transistor is greater than the actual voltage, the control signal is an effective level, and the switch transistor is controlled to be turned on; when the comparison threshold value is equal to the actual voltage, the control signal is an ineffective level, and the switch transistor is controlled to be turned off, and the switch transistor is turned on again when the complementary switch transistor is turned off. For example, the effective level is high level, and the ineffective level is low level; or the effective level is low level, and the ineffective level is high level. The control signals of the two complementary switch transistors are opposite, that is, when one switch transistor is turned on, the other switch transistor is turned off.

[0074] For example, as shown in FIG. 1, the resonant converter, for example, when the first switch transistor is turned on, the second switch transistor is turned off, and when the first switch transistor is turned off, the second switch transistor Conducting. In the first switch transistor Conducting, the first switch transistor The corresponding counter starts counting, the first switch transistor The comparison threshold value calculated by the count value of the corresponding counter is greater than the actual voltage, the first switch transistor Keep conducting, the first switch transistor When the comparison threshold value obtained by the count value of the corresponding counter is equal to the actual voltage of the resonant capacitor, the first switch transistor is controlled Turn off, the second switch transistor Conducting, the second switch transistor The corresponding counter starts counting, the second switch transistor The comparison threshold value calculated by the count value of the corresponding counter is less than the actual voltage, the second switch transistor Keep conducting, the second switch transistor When the comparison threshold value obtained by the count value of the corresponding counter is equal to the actual voltage of the resonant capacitor, the second switch transistor is controlled Turn off. Repeat this way to achieve waveform control of the actual voltage, and can output multiple periods of actual voltage, which is convenient for realizing power supply to the load.

[0075] The technical scheme of the embodiment determines the target power value corresponding to each bridge arm according to the input power control amount and the compensation amount corresponding to each bridge arm in each switching period, determines the target slope control amount corresponding to the counter of the switch transistor according to the target power value, the input voltage, the circuit parameters of the resonant converter and the current working mode of the full-bridge inverter module, adjusts the comparison threshold value according to the target slope control amount, and controls the conduction or turn-off of the switch transistor according to the relationship between the comparison threshold value and the actual voltage of the resonant capacitor, thereby adjusting the input power and realizing direct control of the single-cycle input power. And the direct current offset voltage of the resonant capacitor corresponding to different working modes is different, so that the determined comparison threshold value can be applied to different working modes, and the switching of different working modes is realized. Even if the working mode is switched, the output voltage of the resonant converter can also be well controlled, and stable output of the output voltage is realized. Moreover, the comparison threshold value is determined according to the count value of the counter, so that the comparison threshold value is a variable, which can improve the transient control in the working process of the resonant converter and realize better control of the output of the resonant converter.

[0076] On the basis of the above technical scheme, optionally, the direct current offset voltage is the product of the direct current offset voltage control amount corresponding to the working mode on the resonant capacitor and the sampling coefficient.

[0077] For example, the direct current offset voltage is , the corresponding DC offset voltage control quantity on the resonance capacitor is , and the sampling coefficient is . Then .

[0078] For example, the full-bridge inverter module includes a first bridge arm and a second bridge arm, the first bridge arm includes a first switch transistor and a second switch transistor, and the second bridge arm includes a third switch transistor and a fourth switch transistor, that is, the full-bridge inverter module shown in FIG. 1. Alternatively, the DC offset voltage is the product of the switching duty ratio of the first switch transistor and the first input voltage of the first bridge arm, plus the second input voltage of the second bridge arm, minus the product of the switching duty ratio of the third switch transistor and the second input voltage.

[0079] For example, the switching duty ratio of the first bridge arm is , the first input voltage of the first bridge arm is , the switching duty ratio of the second bridge arm is , the second input voltage of the second bridge arm is , when the full-bridge inverter module works in the full-bridge working mode, the switching duty ratio of the first switch transistor is the switching duty ratio of the first bridge arm, and the switching duty ratio of the third transistor is the switching duty ratio of the second bridge arm. Then , when , then .

[0080] When the full-bridge inverter module works in the half-bridge working mode, the switching duty ratios of the first bridge arm and the second bridge arm are both 50%, and the first bridge arm and the second bridge arm will work at 50% duty ratio every other period in steady state. The actual duty ratio of the first switch transistor is , the actual duty ratio of the third switch transistor is , and then .

[0081] On the basis of the above technical solutions, optionally, when the working mode of the full-bridge inverter module is switched, the control method of the resonant converter further includes:

[0082] enabling or disabling the half-bridge working mode of the full-bridge inverter module, and updating the DC offset voltage of the resonance capacitor according to the switched working mode, and updating the target slope control quantity according to the switched working mode.

[0083] For example, the default working mode of the full-bridge inverter module is the full-bridge working mode, and when the working mode is switched for the first time, the half-bridge working mode of the full-bridge inverter module needs to be enabled, for example, switched to the low-voltage interleaved half-bridge mode. When the working mode is switched again, the half-bridge working mode of the full-bridge inverter module needs to be disabled, and then switched to the full-bridge working mode. And the DC offset voltage of the resonant capacitor and the target slope control quantity are updated according to the switched working mode, so that the comparison threshold determined according to the DC offset voltage and the target slope control quantity can be the comparison threshold in the corresponding mode, so that the determined comparison threshold can be applicable to different working modes, and then after the working mode is switched, the resonant converter can still stably output voltage.

[0084] Enabling or disabling the half-bridge working mode of the full-bridge inverter module, and updating the DC offset voltage of the resonant capacitor according to the switched working mode, and updating the target slope control quantity according to the switched working mode, can be performed before the working mode is switched, that is, before the first switching cycle after the working mode is switched, facilitating smooth transition when the working mode is switched.

[0085] On the basis of the above technical solutions, FIG. 7 is a flow chart of another control method of a resonant converter provided by the embodiment of the present application. Optionally, referring to FIG. 7, the control method of the resonant converter comprises:

[0086] S201, in each switching cycle, input the output voltage, the reference voltage and the first feedback coefficient of the resonant converter to the output voltage closed-loop controller to obtain a first deviation value.

[0087] The output voltage can be divided by the first feedback coefficient to obtain a first feedback voltage, and then the difference between the reference voltage and the first feedback voltage is input to the voltage closed-loop controller, so that the voltage closed-loop controller outputs the first deviation value, facilitating control of the output voltage of the resonant converter according to the first deviation value. The voltage closed-loop controller can be a proportional integral (PI) controller, a proportional integral differentiation (PID) controller or other types of controllers, and the embodiment is not limited thereto.

[0088] For example, the reference voltage is , the output voltage is , and the first feedback coefficient is , then the first feedback voltage is , and the difference between the reference voltage and the first feedback voltage is .

[0089] S202, obtaining a power feedforward value according to the output voltage, the output current of the resonant converter, the first feedback coefficient and the second feedback coefficient, and obtaining an initial target input power value according to the power feedforward value and the first deviation value.

[0090] The output voltage can be divided by the first feedback coefficient to obtain a first feedback voltage. The output current can be divided by the second feedback coefficient to obtain a first feedback current. The first feedback voltage is multiplied by the first feedback current to obtain the power feedforward value. The power feedforward value is added with the first deviation value to obtain the initial target input power value. In this way, the target input power value can be determined according to the output parameters and the input parameters of the resonant converter, so as to facilitate the adjustment of the input power according to the output parameters and the input parameters of the resonant converter, and further to realize the direct control of the input power.

[0091] For example, the output current of the resonant converter is , and the second feedback coefficient is, for example, , then the first feedback current is . The first feedback voltage is , then the power feedforward value is . For example, the first deviation value is , then the initial target input power value is .

[0092] S203, inputting the first input voltage, the second input voltage and a sampling coefficient to an input voltage equalization closed-loop controller to obtain a second deviation value; wherein the full-bridge inverter module comprises a first bridge arm and a second bridge arm, the first input voltage is the input voltage of the first bridge arm, and the second input voltage is the input voltage of the second bridge arm.

[0093] The first input voltage divided by the sampling coefficient can obtain a first actual input voltage, and the second input voltage divided by the sampling coefficient can obtain a second actual input voltage. The difference between the first actual input voltage and the second actual input voltage is input to the input voltage equalization closed-loop controller, and the input voltage equalization closed-loop controller outputs the second deviation value. In this way, the difference between the input voltages of the two bridge arms in the full-bridge inverter module can be determined, so as to facilitate the adjustment of the input power according to the difference between the input voltages of the two bridge arms, thereby balancing the input voltages of the two bridge arms. In this way, the problem of uneven voltage of the two bridge arms after long time work can be avoided. The input voltage equalization closed-loop controller can be a proportional integral controller, or a proportional integral derivative controller or other type of controller, which is not limited in the embodiment.

[0094] For example, the first input voltage is , the second input voltage is , and the sampling coefficient is , the first actual input voltage is , the second actual input voltage is , the difference between the first actual input voltage and the second actual input voltage is input to the input voltage controller, and the input voltage controller outputs a second deviation value .

[0095] S204, determining an input power control amount according to the initial target input power value, the second deviation value and a normalization coefficient.

[0096] For example, the full-bridge inverter module includes a first bridge arm and a second bridge arm. The initial target input power value is multiplied by the normalization coefficient to obtain a first normalized value, the second deviation value is multiplied by the normalization coefficient to obtain a second normalized value, and the first normalized value and the second normalized value are added to obtain an input power control amount corresponding to the first bridge arm. The first normalized value is subtracted from the second normalized value to obtain an input power control amount corresponding to the second bridge arm, i.e. to obtain an input power control amount corresponding to each bridge arm. The normalization coefficient can be a preset value.

[0097] For example, the normalization coefficient is , the initial target input power value is multiplied by the normalization coefficient to obtain a first normalized value , the second deviation value is multiplied by the normalization coefficient to obtain a second normalized value , the first normalized value and the second normalized value are added to obtain an input power control amount corresponding to the first bridge arm , the first normalized value is subtracted from the second normalized value to obtain an input power control amount corresponding to the second bridge arm . In this way, the target power value can be determined according to the input power control amount, and the input power of the bridge arm can be directly controlled.

[0098] S205, in each switching cycle, determining a target power value corresponding to each bridge arm according to the input power control amount corresponding to each bridge arm and a compensation amount.

[0099] S206, determining a target slope control amount corresponding to a counter corresponding to a switching transistor according to the target power value, an input voltage, a circuit parameter of the resonant converter and a current working mode of the full-bridge inverter module; wherein the working mode includes a full-bridge working mode or a half-bridge working mode.

[0100] S207, determine a comparison threshold according to the target slope control quantity, the current counting value of the counter corresponding to the switch transistor, and the DC offset voltage of the resonant capacitor corresponding to the current working mode; wherein the counter starts counting with the DC offset voltage as the initial value in each switching period until the actual voltage of the resonant capacitor is equal to the comparison threshold.

[0101] S208, determine a control signal according to the actual voltage of the resonant capacitor and the comparison threshold, and control the switch transistor according to the control signal.

[0102] On the basis of the above-mentioned multiple technical solutions, FIG. 8 is a flow chart of another control method of a resonant converter provided by the embodiment of the present application. Optionally, referring to FIG. 8, the control method of the resonant converter comprises:

[0103] S301, in each switching period, determine a target power value corresponding to each bridge arm according to an input power control quantity corresponding to each bridge arm and a compensation quantity.

[0104] S302, determine a change slope control quantity corresponding to each bridge arm according to the target power value, the input voltage of each bridge arm, a sampling coefficient, a counting step value of a counter, and a capacitance value of a resonant capacitor, and determine a full-bridge slope control quantity and a half-bridge slope control quantity according to the change slope control quantity.

[0105] For example, the full-bridge inverter module comprises a first bridge arm and a second bridge arm. The input power of the first bridge arm is , the input power of the second bridge arm is , the capacitance value of the resonant capacitor is , the bridge arm switching frequency is , the input voltage of the first bridge arm is , the input voltage of the second bridge arm is , the input power of the first bridge arm (the target power value of the first bridge arm) is , and the input power of the second bridge arm (the target power value of the second bridge arm) is . the voltage of the resonant capacitor when the first switch transistor is turned on or turned off, the voltage of the resonant capacitor when the second switch transistor is turned on or turned off, the voltage of the resonant capacitor when the fourth switch transistor is turned on or turned off, the voltage of the resonant capacitor when the third switch transistor is turned on or turned off. is the output capacitance of the switch transistor.

[0106] And the product of the counting step value and the counting value of the counter can represent the duty cycle of the control signal of the switch transistor, and the bridge arm switching frequency is The counting step value and the counting value of the counter can be used to represent the product. The ratio of the voltage difference of the corresponding resonant capacitor when the two complementary conduction switch transistors are turned off to the sampling coefficient can be represented by the change slope control quantity and the counting value. Therefore, the input power can be obtained by using the change slope control quantity, the input voltage of the bridge arm, the sampling coefficient, the counting step value of the counter, and the capacitance value of the resonant capacitor. Therefore, the change slope control quantity can be determined according to the target power value, the input voltage of the bridge arm, the sampling coefficient, the counting step value of the counter, and the capacitance value of the resonant capacitor.

[0107] The change slope control quantity is a full-bridge slope control quantity. The half-bridge slope control quantity can be obtained by multiplying the change slope control quantity by 2. Because the interleaving prohibits the conduction of the switch transistor once when working in the half-bridge mode, the change slope control quantity corresponding to the half-bridge mode should be twice that of the full-bridge mode, so that the input power of the half-bridge mode and the full-bridge mode is consistent.

[0108] S303, determining the full-bridge slope control quantity or the half-bridge slope control quantity as the target slope control quantity according to the current working mode of the full-bridge inverter module.

[0109] If the current working mode of the full-bridge inverter module is the full-bridge working mode, the target slope control quantity is the full-bridge slope control quantity. If the current working mode of the full-bridge inverter module is the half-bridge working mode, the target slope control quantity is the half-bridge slope control quantity. In this way, the target slope control quantity is suitable for different working modes.

[0110] S304, determining a comparison threshold according to the target slope control quantity, the current counting value of the counter corresponding to the switch transistor, and the direct current offset voltage of the resonant capacitor corresponding to the current working mode; wherein the counter starts counting with the direct current offset voltage as the initial value in each switching period, and the actual voltage of the resonant capacitor is equal to the comparison threshold.

[0111] S305, determining a control signal according to the actual voltage of the resonant capacitor and the comparison threshold, and controlling the switch transistor according to the control signal.

[0112] On the basis of the above technical solutions, optionally, the change slope control quantity corresponding to each bridge arm is determined according to the target power value, the input voltage of each bridge arm, the sampling coefficient, the counting step value of the counter, and the capacitance value of the resonant capacitor, comprising:

[0113] Step a1, divide the target power value by the input voltage of the corresponding bridge arm, and divide by the capacitance value of the resonance capacitor, to obtain a first intermediate value.

[0114] Step a2, divide the first intermediate value by the sampling coefficient, and multiply by the count step value, to obtain the change slope control quantity of the corresponding bridge arm.

[0115] For example, a full-bridge inverter module includes a first bridge arm and a second bridge arm. The input power of the first bridge arm is , the input power of the second bridge arm is , the capacitance value of the resonance capacitor is , the bridge arm switching frequency is , the input voltage of the first bridge arm is , the input voltage of the second bridge arm is , the input power of the first bridge arm is , and the input power of the second bridge arm is . is the voltage of the resonance capacitor when the first switching transistor is turned on or turned off, is the voltage of the resonance capacitor when the second switching transistor is turned on or turned off, is the voltage of the resonance capacitor when the fourth switching transistor is turned on or turned off, is the voltage of the resonance capacitor when the third switching transistor is turned on or turned off. is the output capacitance of the switching transistor. The output capacitance of the switching transistor is much smaller than the capacitance value of the resonance capacitor , and , which is usually much smaller than the minimum load power, and can be ignored. Then there is , wherein is the input power of the first bridge arm or the input power of the second bridge arm , is or , is or , is or .

[0116] When the bridge arms are symmetrically switched, the maintenance time length of each switching transistor being turned on or turned off is half of the switching period, so there is , wherein a count step value of the counter, a count value of the counter. Then, i.e. , wherein, a sampling coefficient, a change slope control quantity.

[0117] Therefore, substituting into , we can get i.e. , so divide the target power value by the input voltage of the corresponding bridge arm, and divide the capacitance value of the resonant capacitor, to get the first intermediate value . Divide the first intermediate value by the sampling coefficient, and multiply it by the count step value, to get the change slope control quantity of the corresponding bridge arm, i.e. .

[0118] On the basis of the above-mentioned multiple technical solutions, optionally, the control signal is determined according to the actual voltage of the resonant capacitor and the comparison threshold, and the switching transistor of the bridge arm is controlled according to the control signal, comprising:

[0119] Step b1, when the ratio of the actual voltage to the sampling coefficient is less than the comparison threshold, the first target switching transistor in the corresponding bridge arm is turned on.

[0120] The first target switching transistor can be the first switching transistor or the third switching transistor , or the second switching transistor or the fourth switching transistor .

[0121] By setting the sampling coefficient, it is convenient to restore the actual voltage obtained by sampling. The ratio of the actual voltage to the sampling coefficient is the real voltage of the resonant capacitor. When the ratio of the actual voltage to the sampling coefficient is less than the comparison threshold, the first target switching transistor in the corresponding bridge arm can be turned on. When the ratio of the actual voltage to the sampling coefficient is equal to the comparison threshold, the first target switching transistor in the corresponding bridge arm is turned off, and the counter corresponding to the first target switching transistor can stop counting until the second target switching transistor complementary to the first target switching transistor is turned off, the first target switching transistor is turned on, and the counter corresponding to the first target switching transistor starts counting again. Thus, the voltage change on the resonant capacitor is controlled, and the output voltage of the resonant converter is controlled, so that the resonant converter stably outputs the voltage.

[0122] Step b2, when the absolute value of the ratio of the actual voltage to the sampling coefficient is greater than the comparison threshold, the second target switching transistor in the corresponding bridge arm is turned on.

[0123] For example, the first target switch transistor is the first switch transistor , the second target switch transistor is the second switch transistor ; or the first target switch transistor is the third switch transistor , the second target switch transistor is the fourth switch transistor .

[0124] When the ratio of the actual voltage and the sampling coefficient is less than the comparison threshold value, the second target switch transistor is turned off, and the first target switch transistor is turned on. When the ratio of the actual voltage and the sampling coefficient is greater than the comparison threshold value, the first target switch transistor is turned off, the second target switch transistor in the corresponding bridge arm is turned on, and the counter corresponding to the second target switch transistor starts counting until the absolute value of the ratio of the actual voltage and the sampling coefficient is equal to the comparison threshold value calculated by the count value of the counter corresponding to the second target switch transistor. The second target switch transistor is turned off, and the first target switch transistor is turned on. In this way, the complementary switching of the first target switch transistor and the second target switch transistor is realized, which facilitates the voltage on the resonant capacitor to be an alternating voltage. Thus, the voltage change on the resonant capacitor is controlled, and the output voltage of the resonant converter is further controlled, so that the resonant converter stably outputs the voltage.

[0125] Optionally, the control signal is determined according to the actual voltage of the resonant capacitor and the comparison threshold value, and the switch transistor of the corresponding bridge arm is controlled according to the control signal, and the method further comprises:

[0126] When the ratio of the actual voltage and the sampling coefficient is equal to the comparison threshold value corresponding to the first target switch transistor, the first target switch transistor corresponding to the counter is turned off, and the second target switch transistor is turned on, wherein the control signal of the first target switch transistor and the control signal corresponding to the second target switch transistor are inverse. That is, when the control signal of the first target switch transistor is high, the control signal of the second target switch transistor is low; when the control signal of the first target switch transistor is low, the control signal of the second target switch transistor is high, so that when the first target switch transistor is turned on, the second target switch transistor is turned off; when the first target switch transistor is turned off, the second target switch transistor is turned on, that is, the first target switch transistor and the second target switch transistor are complementary turned on.

[0127] When the ratio of the actual voltage and the sampling coefficient is equal to the comparison threshold value corresponding to the first target switch transistor, the first target switch transistor corresponding to the counter is turned off, and the second target switch transistor is turned on, which facilitates the complementary turning on of the first target switch transistor and the second switch transistor, so that the voltage on the resonant capacitor is an alternating voltage, the control of the voltage on the resonant voltage is realized, and the output voltage of the resonant converter is further controlled, so that the resonant converter stably outputs the voltage.

[0128] On the basis of the above-mentioned multiple technical solutions, optionally, the target power value corresponding to each arm is determined according to the input power control amount and the compensation amount corresponding to each bridge arm, comprising:

[0129] The sum of the input power control amount and the compensation amount corresponding to each bridge arm is taken as the target power value corresponding to each bridge arm.

[0130] By setting the compensation amount, the input power control amount can be compensated, facilitating the accuracy of the target power value determination. The compensation amount can be a preset value.

[0131] For example, the input power control amount corresponding to the first bridge arm is , the compensation amount of the first bridge arm is , the target power value of the first bridge arm is , and . For example, the input power control amount corresponding to the second bridge arm is , the compensation amount of the second bridge arm is , the target power value of the second bridge arm is , and .

[0132] For example, FIG. 9 is a time-domain working waveform diagram of a resonant converter provided by an embodiment of the present application. As shown in FIG. 9, the first current waveform is the current of the first rectifier transistor , the second current waveform is the current of the second rectifier transistor , the third current waveform is the current flowing through the resonant inductor , and the fourth current waveform is the current flowing through the magnetizing inductor . is the actual voltage of the resonant capacitor. , are the output voltages of the first bridge arm and the second bridge arm, respectively; , , , are the gate voltages of the first switch transistor , the second switch transistor , the third switch transistor , and the fourth switch transistor , respectively. is the corresponding DC offset voltage on the resonant capacitor of the first bridge arm in full-bridge working mode; is the corresponding DC offset voltage on the resonant capacitor of the second bridge arm in full-bridge working mode. It is the DC offset voltage on the resonant capacitor of the first bridge arm when the bridge is in half-bridge operating mode; It is the DC offset voltage on the resonant capacitor of the second bridge arm when the bridge is in half-bridge operating mode; These are the sampling coefficients; It is the first switching transistor in full-bridge operation mode. The corresponding comparison threshold; It is the third switching transistor in full-bridge operation mode. The comparison threshold corresponding to the shutdown; It is the second switching transistor in full-bridge operation mode. The comparison threshold corresponding to the shutdown; It is the fourth switching transistor in full-bridge operation mode. The comparison threshold corresponding to the shutdown; It is the first switching transistor in half-bridge operating mode. The comparison threshold corresponding to the shutdown; It is the third switching transistor in half-bridge operation mode. The comparison threshold corresponding to the shutdown; It is the second switching transistor in half-bridge operating mode. The comparison threshold corresponding to the shutdown; It is the fourth switching transistor in half-bridge operation mode. The comparison threshold corresponding to the shutdown; It is the input voltage of the first bridge arm; It is the input voltage of the second bridge arm; the times from t0 to t6 and from t0' to t6' are the key control points in the topology operating mode switching process; It is the switching cycle of the full-bridge operating mode; It is the switching cycle of the half-bridge operating mode.

[0133] Line ① represents the slope control quantity (target slope control quantity) of the comparison threshold change corresponding to the first switching transistor in full-bridge operating mode. The comparison threshold is obtained by multiplying the count value by the DC offset voltage of the resonant capacitor in full-bridge operation mode. This comparison threshold, corresponding to the first switching transistor in full-bridge operation mode, varies along line ①. Line ② represents the slope control quantity (target slope control quantity) of the comparison threshold change corresponding to the second switching transistor in full-bridge operation mode. The comparison threshold, obtained by multiplying the count value by the DC offset voltage of the resonant capacitor in full-bridge operation mode, is the comparison threshold corresponding to the second switching transistor in full-bridge operation mode, which varies along line ②. Line ③ represents the slope control quantity (target slope control quantity) of the comparison threshold of the third switching transistor in full-bridge operation mode. The comparison threshold value corresponding to the third switch transistor in the full-bridge working mode varies along the straight line ③, which is obtained by adding the product of the count value and the DC offset voltage of the resonant capacitor in the full-bridge working mode to the comparison threshold value. The comparison threshold value corresponding to the fourth switch transistor in the full-bridge working mode varies along the straight line ④, which is obtained by adding the product of the count value and the DC offset voltage of the resonant capacitor in the full-bridge working mode to the comparison threshold value.

[0134] The change slope control quantity (target change slope control quantity) of the comparison threshold value corresponding to the first switch transistor in the half-bridge working mode is the straight line ⑤. The comparison threshold value corresponding to the first switch transistor in the half-bridge working mode varies along the straight line ⑤, which is obtained by adding the product of the count value and the DC offset voltage of the resonant capacitor in the half-bridge working mode to the comparison threshold value. The change slope control quantity (target change slope control quantity) of the comparison threshold value corresponding to the second switch transistor in the half-bridge working mode is the straight line ⑥. The comparison threshold value corresponding to the second switch transistor in the half-bridge working mode varies along the straight line ⑥, which is obtained by adding the product of the count value and the DC offset voltage of the resonant capacitor in the half-bridge working mode to the comparison threshold value. The change slope control quantity (target change slope control quantity) of the comparison threshold value corresponding to the third switch transistor in the half-bridge working mode is the straight line ⑦. The comparison threshold value corresponding to the third switch transistor in the half-bridge working mode varies along the straight line ⑦, which is obtained by adding the product of the count value and the DC offset voltage of the resonant capacitor in the half-bridge working mode to the comparison threshold value.

[0135] As shown in FIG. 9, when the first switch transistor is turned on, the straight line ① is above the actual voltage of the resonant capacitor, that is, the ratio of the actual voltage of the resonant capacitor to the sampling coefficient is less than the comparison threshold value, and the actual voltage of the resonant capacitor gradually increases. When the ratio of the actual voltage of the resonant capacitor to the sampling coefficient is equal to the comparison threshold value on the straight line ①, the first switch transistor is turned off, the second switch transistor is turned on, the actual voltage of the resonant capacitor gradually decreases, and the counter corresponding to the second switch transistor starts counting. The comparison threshold value varies along the straight line ② until the ratio of the actual voltage of the resonant capacitor to the sampling coefficient is equal to the comparison threshold value on the straight line ②, the second switch transistor is turned off, and the control of one switching period is realized.

[0136] As shown in FIG. 9, at t2, when the working mode of the resonant converter is switched from the full-bridge working mode to the half-bridge working mode, the DC offset voltage of the resonant capacitor and the target slope control quantity change, when the first switch transistor is turned on, the straight line 5 is above the actual voltage of the resonant capacitor, that is, the ratio of the actual voltage of the resonant capacitor to the sampling coefficient is less than the comparison threshold, and the actual voltage of the resonant capacitor gradually increases. When the ratio of the actual voltage of the resonant capacitor to the sampling coefficient is equal to the comparison threshold on the straight line 5, the first switch transistor is turned off, the second switch transistor is turned on, the actual voltage of the resonant capacitor gradually decreases, and the counter corresponding to the second switch transistor starts counting. The comparison threshold changes along the straight line 6 until the ratio of the actual voltage of the resonant capacitor to the sampling coefficient is equal to the comparison threshold on the straight line 6, the second switch transistor is turned off, and the control of one switching cycle is realized. In this way, the stable control of the output voltage is realized, and the smooth transition at the mode switching can be realized.

[0137] The control of the third switch transistor and the fourth switch transistor is the same as the control principle of the first switch transistor and the second switch transistor, and will not be described here.

[0138] FIG. 10 is a state plane running trajectory diagram when the resonant converter is switched from the full-bridge working mode to the half-bridge working mode according to an embodiment of the present application. As shown in FIG. 10, the horizontal axis is the actual voltage of the resonant capacitor , and the vertical axis is the current of the resonant inductor . At t2, the resonant converter is switched from the full-bridge working mode to the half-bridge working mode, and the smooth transition can be realized.

[0139] FIG. 11 is a state plane running trajectory diagram when the resonant converter is switched from the half-bridge working mode to the full-bridge working mode according to an embodiment of the present application. As shown in FIG. 11, the horizontal axis is the actual voltage of the resonant capacitor , and the vertical axis is the current of the resonant inductor . At t2', the resonant converter is switched from the half-bridge working mode to the full-bridge working mode, and the smooth transition can be realized.

[0140] In FIGS. 10 and 11, , is the comparison threshold corresponding to the turn-off of the second switch transistor in the full-bridge working mode; is the comparison threshold corresponding to the turn-off of the fourth switch transistor in the full-bridge working mode. , is the comparison threshold corresponding to the turn-off of the second switch transistor in the half-bridge working mode; ​​​​​​corresponding comparison threshold value when turned off; is the fourth switch transistor in the half-bridge operation mode corresponding comparison threshold value when turned off. is or , is the first switch transistor in the half-bridge operation mode corresponding comparison threshold value when turned off; is the third switch transistor in the half-bridge operation mode corresponding comparison threshold value when turned off. is or , is the first switch transistor in the full-bridge operation mode corresponding comparison threshold value when turned off; is the third switch transistor in the full-bridge operation mode corresponding comparison threshold value when turned off.

[0141] The embodiment of the present application further provides a control system of a resonant converter, Figure 12 is a structural schematic diagram of a control system of a resonant converter provided by the embodiment of the present application, referring to Figure 12, the control system of the resonant converter comprises a target power value determination module 110, a target slope control quantity determination module 120, a comparison threshold value determination module 130 and a control module 140;

[0142] The target power value determination module 110 is configured to determine a target power value corresponding to each bridge arm according to an input power control quantity and a compensation quantity corresponding to each bridge arm in each switching cycle;

[0143] The target slope control quantity determination module 120 is connected with the target power value determination module 110, and the target slope control quantity determination module 120 is configured to determine a target slope control quantity corresponding to a counter of a switch transistor according to a target power value, an input voltage, a circuit parameter of the resonant converter and a current operation mode of a full-bridge inverter module; wherein the operation mode comprises a full-bridge operation mode or a half-bridge operation mode;

[0144] The comparison threshold value determination module 130 is configured to determine a comparison threshold value according to the target slope control quantity, a current counting value of the counter of the switch transistor and a direct current offset voltage of the resonant capacitor corresponding to the current operation mode; wherein the counter starts counting with the direct current offset voltage as an initial value in each switching cycle until an actual voltage of the resonant capacitor is equal to the comparison threshold value;

[0145] The control module 140 is connected with the comparison threshold value determination module 130, and the control module 140 is configured to determine a control signal according to the actual voltage of the resonant capacitor and the comparison threshold value, and to control the switch transistor according to the control signal.

[0146] The target power value determination module 110, the target slope control quantity determination module 120, the comparison threshold value determination module 130, and the control module 140 can be implemented by a circuit, and a control system of the resonant converter can execute the control method of the resonant converter provided in any embodiment of the present application, and the control system of the resonant converter has the same function as the control method of the resonant converter provided in any embodiment of the present application, and will not be described here.

[0147] On the basis of the above technical solutions, the circuit structures that the target power value determination module 110, the target slope control quantity determination module 120, the comparison threshold value determination module 130, and the control module 140 can include are described below, but are not as a limitation of the present application.

[0148] On the basis of the above technical solutions, FIG. 13 is a structural schematic diagram of another control system of a resonant converter provided in an embodiment of the present application. Optionally, referring to FIG. 13, the target power value determination module 110 includes a first adder U1.

[0149] The first input end of the first adder U1 is connected to the input power control quantity, and the second input end of the first adder U1 is connected to the compensation quantity. The first adder U1 is configured to add the input power control quantity and the compensation quantity to obtain the target power value.

[0150] The first adder U1 is arranged in one-to-one correspondence with the bridge arm. The first adder U1 adds the input power control quantity and the compensation quantity to obtain the target power value. For example, the input power control quantity corresponding to the first bridge arm is , the compensation quantity of the first bridge arm is , the target power value of the first bridge arm is , and . For example, the input power control quantity corresponding to the second bridge arm is , the compensation quantity of the second bridge arm is , the target power value of the second bridge arm is , and .

[0151] Optionally, referring to FIG. 13, the target power value determination module 101 further includes a first multiplier U2, a second adder U3, and a voltage closed-loop controller U4. The first multiplier U2 is configured to multiply the output voltage and the reciprocal of the first feedback coefficient to obtain the first feedback voltage . The second adder U3 is configured to subtract the difference between the reference voltage and the first feedback voltage to obtain . The voltage closed-loop controller U4 is configured to obtain the reference voltage The difference of the first feedback voltage is Output the first deviation value .

[0152] Optionally, referring to FIG. 13, the target power value determination module 110 further comprises a second multiplier U5, a third multiplier U6 and a third adder U7, the second multiplier U5 is configured to multiply the output current of the resonant converter by the reciprocal of the second feedback coefficient to obtain a first feedback current . The third multiplier U6 is configured to multiply the first feedback voltage by the first feedback current to obtain a power feedforward value is . The third adder U7 is configured to add the first deviation value and the power feedforward value to obtain an initial target input power value , that is .

[0153] Optionally, referring to FIG. 13, the target power value determination module 110 further comprises a fourth multiplier U8, a fifth multiplier U9, a fourth adder U10 and an input voltage equalization closed-loop controller U11; the fourth multiplier U8 is configured to multiply the first input voltage of the first bridge arm by the reciprocal of the sampling coefficient to obtain a first actual input voltage . The fifth multiplier U9 is configured to multiply the second input voltage of the second bridge arm by the reciprocal of the sampling coefficient to obtain a second actual input voltage . The fourth adder U10 is configured to calculate the difference of the first actual input voltage minus the second actual input voltage . The input voltage equalization closed-loop controller U11 is configured to output a second deviation value according to the difference of the first actual input voltage minus the second actual input voltage .

[0154] Optionally, referring to FIG. 13, the target power value determination module 110 further comprises a sixth multiplier U12, a seventh multiplier U13, a fifth adder U14 and a sixth adder U15; the sixth multiplier U12 is configured to multiply the initial target input power value by a normalization coefficient to obtain a first normalization value ; the seventh multiplier U13 is configured to multiply the second deviation value by the normalization coefficient to obtain a second normalization value ; the fifth adder U14 is configured to add the first normalization value and the second normalized value to obtain the input power control quantity corresponding to the first bridge arm ; the sixth adder U15 is configured to subtract the second normalized value from the first normalized value to obtain the input power control quantity corresponding to the second bridge arm . In this way, the target power value is determined according to the input power control quantity, and then the direct control of the input power of the bridge arm is realized.

[0155] Optionally, as shown in FIG. 13, the target slope control quantity determination module 120 includes a first divider U16 and an eighth multiplier U17. The first divider U16 is configured to divide the target power value by the ratio of the input voltage to the sampling coefficient. The eighth multiplier U17 is configured to multiply the output value of the first divider U16 by the ratio of the counting step value of the counter to the square of the sampling coefficient and the capacitance value of the resonant capacitor. In this way, the calculation of the target slope control quantity is realized.

[0156] Optionally, as shown in FIG. 13, the control system of the resonant converter further includes a mode switching unit U18. The mode switching unit U18 is configured to output a mode value Mode according to a switching control signal. For example, the output mode value Mode is 1, indicating the full-bridge working mode, and the output mode value Mode is 0, indicating the half-bridge working mode; or the output mode value Mode is 0, indicating the full-bridge working mode, and the output mode value Mode is 1, indicating the half-bridge working mode.

[0157] In FIG. 13, the mode switching unit U18 is located in the target power value determination module 110, but it does not mean that the mode switching unit U18 belongs to the target power value determination module 110.

[0158] Optionally, as shown in FIG. 13, the comparison threshold value determination module 130 includes a first selector U19, a second selector U20, a ninth multiplier U21, a seventh adder U22, and a counter U23. The first selector U19 is configured to select the full-bridge slope control quantity or the half-bridge slope control quantity as the target slope control quantity according to the mode value. The second selector U20 is configured to select the direct current offset voltage corresponding to the half-bridge working mode or the direct current offset voltage corresponding to the full-bridge working mode according to the mode value. The ninth multiplier U21 is configured to multiply the target slope control quantity by the counting value output by the counter U23. The seventh adder U22 is configured to add the direct current offset voltage to the result of multiplying the target slope control quantity by the counting value output by the counter U23, thereby obtaining the comparison threshold value.

[0159] As shown in FIG. 13, ​is a DC offset voltage corresponding to the first bridge arm resonant capacitor in the full-bridge operation mode; is a DC offset voltage corresponding to the second bridge arm resonant capacitor in the full-bridge operation mode; is a DC offset voltage corresponding to the first bridge arm resonant capacitor in the half-bridge operation mode; is a DC offset voltage corresponding to the second bridge arm resonant capacitor in the half-bridge operation mode; is a variation slope control quantity of the comparison threshold in the full-bridge operation mode of the first bridge arm; is a variation slope control quantity of the comparison threshold in the full-bridge operation mode of the second bridge arm; is a variation slope control quantity of the comparison threshold in the half-bridge operation mode of the first bridge arm; is a variation slope control quantity of the comparison threshold in the half-bridge operation mode of the second bridge arm; is a DC offset voltage of the first bridge arm output by the second selector corresponding to the first bridge arm, is a DC offset voltage of the second bridge arm output by the second selector corresponding to the second bridge arm.

[0160] Optionally, referring to FIG. 13, the control module 140 includes a flip-flop U24 and a comparator U25, the comparator U25 is configured to control the switch transistor to be turned off when the comparison threshold corresponding to the count value output by the counter U23 is equal to the ratio of the actual voltage of the resonant capacitor and the sampling coefficient; the flip-flop U24 is configured to trigger the counter U23 to be reset when the comparator U25 outputs a signal for controlling the switch transistor to be turned off, so as to facilitate the counter U23 to start counting again next time. In this way, the control of the switch transistor is realized, so as to control the output voltage of the resonant converter. The flip-flop U24 is, for example, an RS flip-flop. In some other embodiments, the flip-flop U24 can also be a D flip-flop or other flip-flop, and the present embodiment does not make any limitation.

[0161] On the basis of the above-mentioned multiple technical solutions, the resonant converter includes a full-bridge inverter module 11, a resonant module 12 and a rectifier module 13. The full-bridge inverter module can be a series full-bridge circuit as shown in FIG. 1, or can be other circuits, and FIG. 14 is a circuit structure schematic diagram of a full-bridge inverter module provided by an embodiment of the present application, as shown in FIG. 14, the full-bridge inverter module 11 is a parallel full-bridge circuit. The resonant module 12 can include a resonant circuit and a transformer as shown in FIG. 1, or can include other circuits, and FIG. 15 is a circuit structure schematic diagram of a resonant module provided by an embodiment of the present application, as shown in FIG. 15, the resonant module 12 includes a first resonant capacitor , a second resonant capacitor , a first resonant inductor , a second resonant inductor and an excitation inductor Fig. 16 is a schematic diagram of another resonant module according to an embodiment of the present application. The control method of the resonant converter and the control system of the resonant converter according to the present application can be applied to a resonant converter formed by any of the resonant modules shown in Fig. 1, Fig. 15 or Fig. 16. The rectifier module can include a parallel full-bridge rectifier circuit as shown in Fig. 1, or other circuits. For example, Fig. 17 is a schematic diagram of a rectifier module according to an embodiment of the present application. As shown in Fig. 17, the rectifier module 13 includes the same devices as the rectifier module in Fig. 1, and the rectifier module 13 shown in Fig. 17 includes a series full-bridge rectifier circuit. Fig. 18 is a schematic diagram of another rectifier module according to an embodiment of the present application. As shown in Fig. 18, the rectifier module 13 includes a half-bridge rectifier circuit, which is different from the rectifier module 13 in Fig. 1 and Fig. 17 in that the second output capacitor C2 in Fig. 18 is connected to the output terminal of the second high-frequency rectifier transistor Q2. includes a high-voltage output capacitor and a low-voltage output capacitor Fig. 19 is a schematic diagram of another rectifier module according to an embodiment of the present application. As shown in Fig. 19, the rectifier module 13 includes a center-tapped transformer rectifier circuit. Fig. 20 is a schematic diagram of another rectifier module according to an embodiment of the present application. As shown in Fig. 20, the rectifier module 13 includes a half-bridge high-frequency link rectifier circuit. The rectifier module 13 includes a first high-frequency rectifier transistor Q1, a second high-frequency rectifier transistor Q2, a third high-frequency rectifier transistor Q3, a fourth high-frequency rectifier transistor Q4, a first output capacitor C1, a second output capacitor C2, and an output capacitor C3. Fig. 21 is a schematic diagram of another rectifier module according to an embodiment of the present application. As shown in Fig. 21, the rectifier module 13 includes a full-bridge high-frequency link rectifier circuit. Fig. 22 is a schematic diagram of another rectifier module according to an embodiment of the present application. As shown in Fig. 22, the rectifier module 13 includes a cascaded rectifier circuit. The control method of the resonant converter and the control system of the resonant converter according to the present application can be applied to a resonant converter formed by any of the rectifier modules 13 shown in Fig. 1, Fig. 17-22.

[0162] The control method of the resonant converter and the control system of the resonant converter according to an embodiment of the present application are used to control the resonant converter shown in Fig. 1. The circuit parameter values of the resonant converter are shown in Table 1.

[0163] Table 1 Circuit parameter values of the resonant converter

[0164]

[0165] ​​​​​​FIG. 23 is a waveform diagram of output voltage and output current of a resonant converter according to an embodiment of the present application. As shown in FIG. 23, the control method of the resonant converter and the control system of the resonant converter according to the embodiment of the present application control the resonant converter, so that the output voltage and the output current of the resonant converter are stable, and there is no obvious fluctuation of the output voltage and the output current before and after the switching of the working mode.

[0166] FIG. 24 is a partial enlarged view of the output voltage and the output current of the resonant converter according to an embodiment of the present application. As shown in FIG. 24, the change of the output voltage and the output current is small, and there is no instantaneous impact before and after the switching of the working mode.

[0167] FIG. 25 is a working waveform diagram of the resonant converter switching from the half-bridge working mode to the full-bridge working mode according to an embodiment of the present application. As shown in FIG. 25, the voltage of the resonant capacitor, the current of the resonant inductor and the current of the excitation inductor are stable and smooth transition, and there is no oscillation or impact. The current of the first rectifier transistor and the current of the second rectifier transistor are stable and smooth transition.

[0168] FIG. 26 is a working waveform diagram of the resonant converter switching from the full-bridge working mode to the half-bridge working mode according to an embodiment of the present application. As shown in FIG. 26, the voltage of the resonant capacitor, the current of the resonant inductor and the current of the excitation inductor are stable and smooth transition, and there is no oscillation or impact. The current of the first rectifier transistor and the current of the second rectifier transistor are stable and smooth transition.

[0169] Therefore, the control method of the resonant converter and the control system of the resonant converter according to the embodiment of the present application control the resonant converter, so that the resonant converter can stably output voltage when switching the working mode, and the resonant converter can be better controlled.

[0170] ​​​​​​​​​​​​​​​​​​It should be understood that the processes shown above can be re-ordered, steps can be added or removed, and so on. For example, the various steps described in this application can be performed in parallel, in series, in a different order, and so on, so long as the desired results of the technology described in this application are achieved.

Claims

1. A method for controlling a resonant converter, the resonant converter comprising a full-bridge inverter module, a resonant converter module and a rectifier module; the full-bridge inverter module is connected with the resonant converter module, and the resonant converter module is connected with the rectifier module; the full-bridge inverter module comprises at least two bridge arms; the resonant converter module comprises a resonant capacitor; the method is executed by a control system of the resonant converter. The control system is connected with the control electrode of the switch transistor of the at least two bridge arms respectively, and the control system comprises a counter; the method comprises: In each switching cycle, a target power value corresponding to each bridge arm is determined according to an input power control amount and a compensation amount corresponding to each bridge arm; A target slope control amount corresponding to the counter corresponding to the switch transistor is determined according to the target power value, an input voltage, circuit parameters of the resonant converter and a current working mode of the full-bridge inversion module; wherein the working mode comprises a full-bridge working mode or a half-bridge working mode; A comparison threshold is determined according to the target slope control amount, a current count value of the counter corresponding to the switch transistor and a direct current offset voltage of the resonant capacitor corresponding to the current working mode; wherein the counter starts counting with the direct current offset voltage as an initial value in each switching cycle until the actual voltage of the resonant capacitor is equal to the comparison threshold; A control signal is determined according to the actual voltage of the resonant capacitor and the comparison threshold, and the switch transistor is controlled according to the control signal.

2. The method according to claim 1, when the working mode of the full-bridge inversion module is switched, the method further comprises: The half-bridge working mode of the full-bridge inversion module is enabled or disabled, and the direct current offset voltage of the resonant capacitor is updated according to the switched working mode, and the target slope control amount is updated according to the switched working mode.

3. The method according to claim 1, before the target power value corresponding to each bridge arm is determined according to the input power control amount and the compensation amount corresponding to each bridge arm, the method further comprises: An output voltage of the resonant converter, a reference voltage and a first feedback coefficient are input to an output voltage closed-loop controller to obtain a first deviation value; A power feedforward value is obtained according to the output voltage, an output current of the resonant converter, the first feedback coefficient and a second feedback coefficient, and an initial target input power value is obtained according to the power feedforward value and the first deviation value; A first input voltage, a second input voltage and a sampling coefficient are input to an input voltage equalization closed-loop controller to obtain a second deviation value; wherein the full-bridge inversion module comprises a first bridge arm and a second bridge arm, the first input voltage is an input voltage of the first bridge arm, and the second input voltage is an input voltage of the second bridge arm; The input power control amount is determined according to the initial target input power value, the second deviation value and a normalization coefficient.

4. The method of claim 1, wherein, The target slope control amount corresponding to the counter corresponding to the switch transistor is determined according to the target power value, an input voltage, circuit parameters of the resonant converter and a current working mode of the full-bridge inversion module, comprising: A variation slope control amount corresponding to each bridge arm is determined according to the target power value, an input voltage of each bridge arm, a sampling coefficient, a count step value of the counter and a capacitance value of the resonant capacitor, and a full-bridge slope control amount and a half-bridge slope control amount are determined according to the variation slope control amount; The full-bridge slope control quantity or the half-bridge slope control quantity is determined as the target slope control quantity according to the current working mode of the full-bridge inverter module.

5. The method of claim 1, wherein, The control signal is determined according to the actual voltage of the resonant capacitor and the comparison threshold value, and the switch transistor is controlled according to the control signal, including: When the ratio of the actual voltage to the sampling coefficient is less than the comparison threshold value, the first target switch transistor in the corresponding bridge arm is controlled to be turned on; When the ratio of the actual voltage to the sampling coefficient is greater than the comparison threshold value, the second target switch transistor in the corresponding bridge arm is controlled to be turned on.

6. The method of claim 5, wherein, The control signal is determined according to the actual voltage of the resonant capacitor and the comparison threshold value, and the switch transistor is controlled according to the control signal, further including: When the ratio of the actual voltage to the sampling coefficient is equal to the comparison threshold value corresponding to the first target switch transistor, the first target switch transistor corresponding to the counter is controlled to be turned off, and the second target switch transistor is controlled to be turned on, wherein the control signal corresponding to the first target switch transistor is opposite to the control signal corresponding to the second target switch transistor.

7. The method of claim 1, wherein, The target power value is determined according to the input power control quantity and the compensation quantity corresponding to each bridge arm, including: The sum of the input power control quantity and the compensation quantity corresponding to each bridge arm is taken as the target power value corresponding to each bridge arm.

8. The method of claim 4, wherein, The changing slope control quantity corresponding to each bridge arm is determined according to the target power value, the input voltage of each bridge arm, the sampling coefficient, the counting step value of the counter and the capacitance value of the resonant capacitor, including: The target power value is divided by the input voltage of the corresponding bridge arm and by the capacitance value of the resonant capacitor to obtain a first intermediate value; The first intermediate value is divided by the sampling coefficient and multiplied by the counting step value to obtain the changing slope control quantity of the corresponding bridge arm.

9. A control system of a resonant converter, the resonant converter comprising a full-bridge inverter module, a resonant conversion module and a rectifier module; the full-bridge inverter module being connected with the resonant conversion module, the resonant conversion module being connected with the rectifier module; the full-bridge inverter module comprising at least two bridge arms; the resonant conversion module comprising a resonant capacitor. The control system is connected with the control poles of the switch transistors of the at least two bridge arms respectively; the control system includes a counter; the control system includes: A target power value determination module is configured to determine, in each switching cycle, a target power value corresponding to each bridge arm according to an input power control quantity and a compensation quantity corresponding to each bridge arm; A target slope control quantity determination module is connected with the target power value determination module and is configured to determine a target slope control quantity corresponding to a counter corresponding to the switch transistor according to the target power value, an input voltage, circuit parameters of the resonant converter and a current working mode of the full-bridge inverter module; wherein the working mode includes a full-bridge working mode or a half-bridge working mode; A comparison threshold value determination module is connected with the target slope control quantity determination module and is configured to determine a comparison threshold value according to the target slope control quantity, a current counting value of the counter corresponding to the switch transistor and a direct current offset voltage of the resonant capacitor corresponding to the current working mode; wherein the counter starts counting with the direct current offset voltage as the initial value in each switching cycle until the actual voltage of the resonant capacitor is equal to the comparison threshold value. A control module, connected with the comparison threshold value determination module, is configured to determine a control signal according to the actual voltage of the resonance capacitor and the comparison threshold value, and to control the switching transistor according to the control signal.

10. The control system of a resonant converter according to claim 9, wherein, The target power value determination module comprises a first adder; A first input end of the first adder is connected with the input power control amount, and a second input end of the first adder is connected with the compensation amount; the first adder is configured to add the input power control amount and the compensation amount to obtain the target power value.

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