Adaptive on-time synchronous rectification method for three-phase LLC circuit

Abstract

The application discloses a synchronous rectification method for adaptive conduction duration of a three-phase LLC circuit, comprising: collecting a total output current value and a minimum current value of the three-phase LLC circuit; when the three-phase LLC circuit works at a resonant frequency, judging whether a turn-off moment is in a first judgment interval, if yes, judging whether the total output current value of the turn-off moment is greater than a sum of the minimum current value and a first preset compensation value, if yes, increasing a conduction time of a synchronous rectification tube; when the three-phase LLC circuit works at an under-resonant frequency, judging whether the turn-off moment is in a second judgment interval, if yes, judging whether the total output current value of the turn-off moment is greater than a sum of the minimum current value and a second preset compensation value, if yes, increasing the conduction time of the synchronous rectification tube. The embodiment of the application can realize the synchronous rectification of the three-phase LLC circuit by only setting a single current detection device or a total output current sampling circuit in the three-phase LLC circuit.

Description

Technical Field

[0001] This application relates to the field of resonant converter technology, and in particular to a synchronous rectification method for an adaptive on-time of a three-phase LLC circuit. Background Technology

[0002] Three-phase LLC (resonant circuit) has attracted widespread attention due to its magnetic integration characteristics, current sharing mechanism, and current ripple suppression effect. However, when operating at low voltage and high current, although the primary-side switching transistor can achieve soft switching to reduce overall losses, the secondary-side diode rectification will become the main part of the losses. Synchronous rectification of three-phase LLC plays a crucial role in improving efficiency.

[0003] Regarding research on LLC synchronous rectification strategies, some scholars sample the drain voltage of the synchronous rectifier diodes and analyze voltage changes and magnitudes to determine the turn-on and turn-off timings. To reduce the number of components, some scholars introduce the concept of virtual current to continuously increase the synchronous rectification drive's on-time. For three-phase LLC synchronous rectification strategies, traditional designs collect the current of each synchronous rectifier device, turning it on when the current reaches a certain threshold and turning it off when it falls below. This approach requires six current sensing devices, significantly reducing the power density of the designed power supply. For this reason, some scholars use the same approach, collecting the sum of the currents of the two synchronous transistors on the same path at the transformer secondary output. Based on the current switching status of the transistors, they determine the corresponding synchronous drive transistor and then use a threshold design method for the synchronous rectification strategy. This scheme reduces the required six current sensing devices to three. However, considering that power supply designs typically collect the total current from all three paths, this scheme still uses as many as four current sampling circuits. Summary of the Invention

[0004] The purpose of this application is to provide a synchronous rectification method for a three-phase LLC circuit with adaptive on-time, thereby solving the technical problem that existing three-phase LLC synchronous rectification methods require a large number of current sensing devices. The various technical effects of the preferred solutions among the many technical solutions provided in this application are detailed below.

[0005] To achieve the above objectives, this application provides the following technical solutions:

[0006] This application provides a synchronous rectification method for adaptive on-time of a three-phase LLC circuit, comprising: acquiring the total output current value and minimum current value of the three-phase LLC circuit, wherein the minimum current value is the minimum current value of the synchronous rectifier tube within a judgment interval; when the three-phase LLC circuit operates at the resonant frequency, determining whether the turn-off time of the synchronous rectifier tube is within a first judgment interval; if it is within the first judgment interval, determining whether the total output current value at the turn-off time of the synchronous rectifier tube is greater than the sum of the minimum current value and a first preset compensation value; if it is greater, increasing the on-time of the synchronous rectifier tube; when the three-phase LLC circuit operates at an under-resonant frequency, determining whether the turn-off time of the synchronous rectifier tube is within a second judgment interval; if it is within the second judgment interval, determining whether the total output current value at the turn-off time of the synchronous rectifier tube is greater than the sum of the minimum current value and a second preset compensation value; if it is greater, increasing the on-time of the synchronous rectifier tube.

[0007] In some embodiments, the synchronous rectification method for adaptive conduction time of the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at the resonant frequency, determining whether the conduction time of the synchronous rectifier tube is within a third determination interval; if it is within the third determination interval, determining whether the total output current value at the conduction time is greater than the sum of the minimum current value and the third preset compensation value; if it is greater, increasing the conduction time of the synchronous rectifier tube.

[0008] In some embodiments, the synchronous rectification method for adaptive conduction time of the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at the resonant frequency, determining whether the turn-off time of the synchronous rectifier tube is within a fourth determination interval; if it is within the fourth determination interval, determining whether the total output current value at the conduction time is greater than the sum of the minimum current value and the fourth preset compensation value; if it is greater, increasing the conduction time of the synchronous rectifier tube.

[0009] In some embodiments, the adaptive conduction time synchronous rectification method of the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at the resonant frequency, if the total output current value at the turn-off time of the synchronous rectifier is less than the sum of the minimum current value and the first preset compensation value, then the conduction time of the synchronous rectifier is maintained; if the turn-off time of the synchronous rectifier is not within the first judgment interval, then the conduction time of the synchronous rectifier is increased.

[0010] In some embodiments, the adaptive on-time synchronous rectification method for the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at an underresonant frequency, if the total output current value at the turn-off time of the synchronous rectifier is less than the sum of the minimum current value and the second preset compensation value, then the on-time of the synchronous rectifier is maintained; if the turn-off time of the synchronous rectifier is not within the second judgment interval, then the on-time of the synchronous rectifier is increased.

[0011] In some embodiments, the synchronous rectification method for adaptive conduction time of the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at an over-resonant frequency, if the total output current value at the turn-off time of the synchronous rectifier is less than the sum of the minimum current value and the third preset compensation value, then the conduction time of the synchronous rectifier is maintained; if the conduction time of the synchronous rectifier is not within the third judgment interval, then the conduction time of the synchronous rectifier is increased.

[0012] In some embodiments, the adaptive conduction time synchronous rectification method of the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at an over-resonant frequency, if the total output current value at the conduction time of the synchronous rectifier is less than the sum of the minimum current value and the fourth preset compensation value, then the conduction time of the synchronous rectifier is maintained; if the turn-off time of the synchronous rectifier is not within the fourth judgment interval, then the conduction time of the synchronous rectifier is increased.

[0013] In some embodiments, the first determination interval is one-third of a switching cycle centered on the turn-off time of the switching transistor.

[0014] In some embodiments, the second determination interval is one-sixth of a switching cycle before the turn-off time of the switching transistor.

[0015] In some embodiments, the third judgment interval is one-sixth of a switching cycle after the switch is turned off, and the fourth judgment interval is one-sixth of a switching cycle after the other switch in the same phase is turned off.

[0016] Implementing one of the above-described technical solutions of this application has the following advantages or beneficial effects: In this application, different judgment intervals are set for the conduction time of the synchronous rectifier tube according to different operating sections of the three-phase LLC circuit. By collecting the minimum current value within the judgment interval and comparing it with the total output current value of the three-phase LLC circuit, it is determined whether to maintain or increase the conduction time of the synchronous rectifier tube based on the comparison result. In this case, the embodiment of this application only needs to set a single current detection device or a total output current sampling circuit in the three-phase LLC circuit to achieve synchronous rectification of the three-phase LLC circuit. Compared with the prior art, which requires multiple current detection devices, this application can increase power density and reduce circuit cost. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0018] Figure 1 This is a flowchart illustrating the synchronous rectification method for adaptive conduction time of a three-phase LLC circuit according to an embodiment of this application.

[0019] Figure 2 This is a schematic diagram of the structure of a three-phase LLC circuit according to an embodiment of this application;

[0020] Figure 3 This is a schematic diagram of the secondary current waveform of phase A and the total output current waveform when the three-phase LLC circuit of this application operates at the resonant frequency;

[0021] Figure 4 This is a simulation waveform diagram of the three-phase LLC circuit of this application operating at the resonant frequency;

[0022] Figure 5 This is a simulation waveform diagram of the three-phase LLC circuit of this application operating at the under-resonant frequency;

[0023] Figure 6 This is a simulation waveform diagram of the three-phase LLC circuit of this application operating above the resonant frequency. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, various exemplary embodiments described below will be referenced to the accompanying drawings, which form part of the exemplary embodiments and depict various exemplary embodiments that may be adopted to implement this application. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. It should be understood that they are merely examples of processes, methods, and apparatuses consistent with some aspects of this application disclosed as detailed in the appended claims, and other embodiments may be used, or structural and functional modifications may be made to the embodiments listed herein without departing from the scope and spirit of this application.

[0025] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," etc., indicate the orientation or positional relationship based on the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the referred element must have a specific orientation, or be constructed and operated in a specific orientation. The terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. The term "multiple" means two or more. The terms "connected" and "linked" should be interpreted broadly, for example, they can be fixed connections, detachable connections, integral connections, mechanical connections, electrical connections, communication connections, direct connections, indirect connections through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. The term "and / or" includes any and all combinations of one or more of the related listed items. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] To illustrate the technical solutions described in this application, specific embodiments are provided below, showing only the parts related to the embodiments of this application.

[0027] like Figures 1 to 6 As shown, this application provides a synchronous rectification method for adaptive on-time of a three-phase LLC circuit, which may include the following steps (steps S1 to S3):

[0028] S1. Collect the total output current value and minimum current value of the three-phase LLC circuit, where the minimum current value is the minimum current value of the synchronous rectifier tube within the judgment interval.

[0029] like Figure 2 As shown, the primary side of the three-phase LLC circuit in this embodiment includes six switching transistors Q1 to Q6, and the secondary side includes six synchronous rectifier transistors SR1 to SR6. The three-phase LLC circuit is equipped with a Hall sensor for acquiring current values, i.e. Figure 2 The Hall sensor in the circuit can transmit signals to the synchronous rectifier controller, i.e. Figure 2 The SR controller in the middle sends the total output current value. Meanwhile, in this embodiment, the output voltage V of the three-phase LLC circuit is used as the reference. out With the set reference voltage V ref The primary-side switching frequency f is obtained. s The signal is then sent to the synchronous rectifier controller. The synchronous rectifier controller is connected to each synchronous rectifier diode and calculates the synchronous rectifier diode signal based on the switching frequency and the total output current value. Based on the synchronous rectifier diode signal, the on-time of the synchronous rectifier diode is adjusted, that is, the on-time and off-time of the synchronous rectifier diode are adjusted. At the same time, the switching frequency is sent to DPWM (Digital Pulse Width Modulation). DPWM is connected to each switching diode and controls the on-time of each switching diode, that is, the on-time and off-time of the switching diode are adjusted.

[0030] Considering that each phase of the three-phase LLC circuit is symmetrical, and the upper and lower transistors on the secondary side of the synchronous rectification are also symmetrical, for ease of description, the following will use the upper transistor of phase A, i.e., switch Q1, the lower transistor of phase A, i.e., switch Q2, and the synchronous rectification transistor SR1 of the three-phase LLC circuit to describe the embodiments of this application. This does not constitute a limitation on the synchronous rectification method involved in the embodiments of this application. In fact, those skilled in the art can synchronously transplant the synchronous rectification method to the synchronous rectification transistors of other phases.

[0031] In some embodiments, the adaptive on-time synchronous rectification method for a three-phase LLC circuit may include: performing interval waveform selection on the total output current value of the three-phase LLC circuit to determine the judgment interval for the synchronous rectifier. When entering the judgment interval, the judgment flag flag can be set to 1. Considering the existence of current waveform imbalance in the three-phase LLC circuit, by setting the judgment interval for the synchronous rectifier, the on-time of the synchronous rectifier can be judged more accurately.

[0032] S2. When the three-phase LLC circuit operates at the resonant frequency, determine whether the turn-off time of the synchronous rectifier is within the first judgment interval. If it is, determine whether the total output current value at the turn-off time of the synchronous rectifier is greater than the sum of the minimum current value and the first preset compensation value. If it is greater, increase the conduction time of the synchronous rectifier. The preset compensation value is a compensation value that takes into account sampling delays, and can be adjusted according to actual needs; no restriction is placed here. Furthermore, the conduction time of the synchronous rectifier can be increased until the total output current value is less than the sum of the minimum current value and the first preset compensation value.

[0033] In some embodiments, when the three-phase LLC circuit operates at the resonant frequency, the preset on-time of the synchronous rectifier can be one-third of a switching cycle, and the first judgment interval can be one-third of a switching cycle centered on the off-time of the rectifier. That is, the first judgment interval can be from one-sixth of the switching cycle before the off-time to one-sixth of the switching cycle after the off-time. The on-time of the synchronous rectifier can be the dead time after the corresponding rectifier is turned on, that is, the on-time plus the dead time.

[0034] In some embodiments, the synchronous rectification method for adaptive conduction time of a three-phase LLC circuit may further include: when the three-phase LLC circuit operates at the resonant frequency, if the total output current value at the turn-off time of the synchronous rectifier is less than the sum of the minimum current value and the first preset compensation value, then the conduction time of the synchronous rectifier is maintained; if the turn-off time of the synchronous rectifier is not within the first judgment interval, then the conduction time of the synchronous rectifier is increased.

[0035] Specifically, similar to the single-phase LLC circuit, when the three-phase LLC circuit operates at the resonant frequency, current begins to flow through the corresponding synchronous rectifier SR1 when the primary-side switch Q1 is turned on. Therefore, the turn-on time of the synchronous rectifier SR1 can be selected as the time Td after a certain dead time is added after the switch Q1 is turned on. For the selection of the turn-off time, a current reference mechanism can be introduced, with a preset turn-off time Toff = 5 / 6 Tsw, where Tsw is the switching period. The synchronous rectifier's turn-on time is Tsy_time = Toff - Td. When the synchronous rectifier is turned off, the total output current value Isense is collected. In the first judgment interval, it can be compared with the minimum current value Ioutmin corresponding to the turn-off time of the synchronous rectifier. If Isense - ΔI > Ioutmin, where ΔI is a compensation value considering sampling delay, it indicates that the turn-on time is too short. The turn-on time Tsy_time can be increased until Isense - ΔI... <Ioutmin。

[0036] S3. When the three-phase LLC circuit operates at the under-resonant frequency, determine whether the turn-off time of the synchronous rectifier is within the second judgment interval. If it is, determine whether the total output current value at the turn-off time of the synchronous rectifier is greater than the sum of the minimum current value and the second preset compensation value. If it is greater, increase the conduction time of the synchronous rectifier. Similar to when operating at the resonant frequency, the conduction time of the synchronous rectifier can be increased until the total output current value is less than the sum of the minimum current value and the second preset compensation value.

[0037] In some embodiments, when the three-phase LLC circuit operates at an underresonant frequency, the preset on-time of the synchronous rectifier can be one-third of a switching cycle, and the second judgment interval can be one-sixth of a switching cycle before the turn-off time of the rectifier, that is, the second judgment interval can be from the moment of one-sixth of a switching cycle before the turn-off time of the rectifier to the turn-off time. The on-time of the synchronous rectifier can be the dead time after the corresponding rectifier is turned on, that is, the on-time plus the dead time.

[0038] In some embodiments, the synchronous rectification method for adaptive conduction time of a three-phase LLC circuit may further include: when the three-phase LLC circuit operates at an underresonant frequency, if the total output current value at the turn-off time of the synchronous rectifier is less than the sum of the minimum current value and the second preset compensation value, then the conduction time of the synchronous rectifier is maintained; if the turn-off time of the synchronous rectifier is not within the second judgment interval, then the conduction time of the synchronous rectifier is increased.

[0039] Specifically, when the three-phase LLC circuit operates at an under-resonant frequency, the turn-on time of the synchronous rectifier SR1 can be the same as when operating at the resonant frequency, and can coincide with the turn-on time of the switching transistor Q1. The ideal turn-off time of the synchronous rectifier occurs before the switch Q1 turns off. In this embodiment, the end of the second judgment interval is set as the turn-off time of the switch Q1. The length of the second judgment interval is 1 / 6 of a switching cycle, and the conduction time Tsy_time = Teriod / 3, where Teriod is the switching cycle. By determining whether the current at the turn-off time of the synchronous rectifier is greater than the minimum output current value within the second judgment interval by ΔI, the conduction time of the synchronous rectifier is either increased or maintained.

[0040] In some embodiments, the adaptive on-time synchronous rectification method for a three-phase LLC circuit may further include: when the three-phase LLC circuit operates above the resonant frequency, determining whether the on-time of the synchronous rectifier is within a third determination interval; if it is within the third determination interval, determining whether the total output current value at the on-time is greater than the sum of the minimum current value and the third preset compensation value; if it is greater, increasing the on-time of the synchronous rectifier. Specifically, the on-time of the synchronous rectifier can be increased until the total output current value is less than the sum of the minimum current value and the third preset compensation value. Further, the on-time of the synchronous rectifier can be advanced to increase the on-time of the synchronous rectifier.

[0041] In some embodiments, the adaptive on-time synchronous rectification method for a three-phase LLC circuit may further include: when the three-phase LLC circuit operates above the resonant frequency, if the total output current value at the turn-off time of the synchronous rectifier is less than the sum of the minimum current value and the third preset compensation value, then the on-time of the synchronous rectifier is maintained; if the on-time of the synchronous rectifier is not within the third judgment interval, then the on-time of the synchronous rectifier is increased. Further, the on-time of the synchronous rectifier can be shifted forward to increase its on-time.

[0042] In some embodiments, the adaptive on-time synchronous rectification method for a three-phase LLC circuit may further include: when the three-phase LLC circuit operates above the resonant frequency, determining whether the turn-off time of the synchronous rectifier is within a fourth determination interval; if it is within the fourth determination interval, determining whether the total output current value at the on-time is greater than the sum of the minimum current value and the fourth preset compensation value; if it is greater, increasing the on-time of the synchronous rectifier. Specifically, the on-time of the synchronous rectifier can be increased until the total output current value is less than the sum of the minimum current value and the fourth preset compensation value. Further, the turn-off time of the synchronous rectifier can be shifted later to increase the on-time of the synchronous rectifier.

[0043] In some embodiments, the adaptive on-time synchronous rectification method for a three-phase LLC circuit may further include: when the three-phase LLC circuit operates above the resonant frequency, if the total output current value at the on-time of the synchronous rectifier is less than the sum of the minimum current value and the fourth preset compensation value, then the on-time of the synchronous rectifier is maintained; if the off-time of the synchronous rectifier is not within the fourth judgment interval, then the on-time of the synchronous rectifier is increased. Further, the off-time of the synchronous rectifier can be shifted later.

[0044] In some embodiments, when the three-phase LLC circuit operates at the resonant frequency, the turn-on time of the synchronous rectifier can precede the turn-off time of the switching transistor by one-third of a switching cycle, and the turn-off time of the synchronous rectifier can be the same as the turn-off time of the switching transistor. The third judgment interval can be one-sixth of a switching cycle after the switching transistor is turned off, that is, the third judgment interval can be from the turn-off time of the switching transistor to the time of one-sixth of a switching cycle after the turn-off time. The fourth judgment interval can be one-sixth of a switching cycle after the other switching transistor in the same phase is turned off, that is, the fourth judgment interval can be from the turn-off time of the other switching transistor in the same phase to the time of one-sixth of a switching cycle after the turn-off time. For the switching transistor Q1 in this embodiment, the other switching transistor in the same phase is the switching transistor Q2.

[0045] Specifically, when the three-phase LLC circuit operates at the resonant frequency, the waveform of the synchronous rectified current is the same as the waveform of the primary-side drive switch Q1 with the same turn-on time, but the waveform has a phase lag, that is, the synchronous rectifier current is 0 after the switch Q1 is driven to turn off.

[0046] When operating above the resonant frequency, embodiments of this application may include strategies for increasing the on-time backward and for increasing the on-time forward. For the strategy of increasing the on-time backward, the turn-off time of switch Q1 can be used as the starting point of the fourth judgment interval. That is, the turn-off time of switch Q1 can be used as the starting point, and the output current at the turn-off time can be compared with the minimum current within the fourth judgment interval to determine whether the turn-off time needs to be shifted backward to increase the on-time.

[0047] Correspondingly, for the strategy of increasing the conduction time forward, the preset amount of conduction time can be set as the 2 / 3 time before the switch Q1 is turned off. By comparing the output current at the moment of conduction with the minimum current value in the third judgment interval, it can be determined whether the conduction time needs to be moved forward to increase the conduction time forward.

[0048] The following are simulation experiments of embodiments of this application:

[0049] In this application embodiment, simulation software was used to verify the three operating frequency ranges under the prototype parameters in Table 1. Table 1 shows the specifications and parameters of the three-phase LLC resonant converter. Figure 4 The waveform diagram is a simulation waveform at the resonant frequency. Figure 5 The image shows the simulated waveform when operating at the underresonant frequency. Figure 6 The simulation waveform is shown when the device operates above the resonant frequency.

[0050]

[0051] Table 1

[0052] Simulation results:

[0053] like Figure 4 As shown, the conduction time of the synchronous rectifier tube continuously increases until the current corresponding to the turn-off moment of the synchronous rectifier drive signal is close to the minimum value of the output current, at which point the conduction time of the synchronous rectifier tube no longer increases.

[0054] like Figure 5 As shown, the conduction time of the synchronous rectifier tube continuously increases until the current corresponding to the turn-off moment of the synchronous rectifier drive signal is close to the minimum value of the output current, at which point the conduction time of the synchronous rectifier tube no longer increases.

[0055] like Figure 6As shown, the conduction time of the synchronous rectifier diode is continuously increased, the turn-on time is gradually moved forward, and the turn-off time is gradually moved backward, until the current corresponding to the turn-off and turn-on times of the synchronous rectifier drive signal approaches the minimum value of the output current, at which point the conduction time of the synchronous rectifier diode is no longer increased. The effectiveness of the proposed synchronous rectification method is verified through simulation experiments in the embodiments of this application.

[0056] In this application, different judgment intervals are set for the conduction time of the synchronous rectifier tube according to different operating sections of the three-phase LLC circuit. By collecting the minimum current value within the judgment interval and comparing it with the total output current value of the three-phase LLC circuit, the application determines whether to maintain or increase the conduction time of the synchronous rectifier tube based on the comparison result. In this case, the embodiment of this application only needs to set a single current sensing device or a total output current sampling circuit in the three-phase LLC circuit to achieve synchronous rectification of the three-phase LLC circuit. Compared with the prior art, which requires multiple current sensing devices, this application can increase power density and reduce circuit cost.

[0057] Those skilled in the art will understand that all or part of the features / steps of the above-described method embodiments can be implemented by methods, data processing systems, or computer programs. These features may be implemented without hardware, entirely in software, or in a combination of hardware and software. The aforementioned computer program may be stored in one or more computer-readable storage media. When the computer program is executed (e.g., by a processor), it performs the steps of the synchronous rectification method embodiments of the above-described three-phase LLC circuit with adaptive on-time.

[0058] The aforementioned storage media capable of storing program code include: static hard disks, solid-state hard disks, random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), optical storage devices, magnetic storage devices, flash memory, magnetic disks or optical disks, and / or combinations of the above devices, that is, they can be implemented by any type of volatile or non-volatile storage devices or combinations thereof.

[0059] This application also provides a processing device embodiment, including one or more processors and a memory; wherein the memory is used to store one or more computer programs, and the one or more processors are used to execute the one or more computer programs stored in the memory, so that the processors execute the features / steps of the above-described synchronous rectification method embodiment for adaptive conduction duration of a three-phase LLC circuit.

[0060] The above description is merely a preferred embodiment of this application. Those skilled in the art will understand that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this application. Furthermore, under the teachings of this application, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this application. Therefore, this application is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this application.

Claims

1. A synchronous rectification method for an adaptive on-time of a three-phase LLC circuit, characterized in that, include: Collect the total output current value and minimum current value of the three-phase LLC circuit, wherein the minimum current value is the minimum current value of the synchronous rectifier tube within the judgment interval; When the three-phase LLC circuit operates at the resonant frequency, it is determined whether the turn-off time of the synchronous rectifier is within the first judgment interval. If it is within the first judgment interval, it is determined whether the total output current value at the turn-off time of the synchronous rectifier is greater than the sum of the minimum current value and the first preset compensation value. If it is greater, the conduction time of the synchronous rectifier is increased. When the three-phase LLC circuit operates at the under-resonant frequency, it is determined whether the turn-off time of the synchronous rectifier is within the second judgment interval. If it is within the second judgment interval, it is determined whether the total output current value at the turn-off time of the synchronous rectifier is greater than the sum of the minimum current value and the second preset compensation value. If it is greater, the conduction time of the synchronous rectifier is increased. The first judgment interval is one-third of a switching cycle centered on the turn-off time of the switching transistor, and the second judgment interval is one-sixth of a switching cycle before the turn-off time of the switching transistor.

2. The synchronous rectification method for adaptive conduction time of a three-phase LLC circuit according to claim 1, characterized in that, The adaptive on-time synchronous rectification method for the three-phase LLC circuit further includes: When the three-phase LLC circuit operates at the resonant frequency, it is determined whether the conduction time of the synchronous rectifier is within the third judgment interval. If it is within the third judgment interval, it is determined whether the total output current value at the conduction time is greater than the sum of the minimum current value and the third preset compensation value. If it is greater, the conduction time of the synchronous rectifier is increased. The third judgment interval is one-sixth of a switching cycle after the switching transistor is turned off.

3. The synchronous rectification method for adaptive on-time of a three-phase LLC circuit according to claim 2, characterized in that, The adaptive conduction time synchronous rectification method for the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at the resonant frequency, determining whether the turn-off time of the synchronous rectifier is within the fourth judgment interval; if it is within the fourth judgment interval, determining whether the total output current value at the conduction time is greater than the sum of the minimum current value and the fourth preset compensation value; if it is greater, increasing the conduction time of the synchronous rectifier; the fourth judgment interval is one-sixth of a switching cycle after the other switch in the same phase is turned off.

4. The synchronous rectification method for adaptive on-time of a three-phase LLC circuit according to claim 1, characterized in that, The adaptive on-time synchronous rectification method for the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at the resonant frequency, if the total output current value at the turn-off time of the synchronous rectifier is less than the sum of the minimum current value and the first preset compensation value, then the on-time of the synchronous rectifier is maintained; if the turn-off time of the synchronous rectifier is not within the first judgment interval, then the on-time of the synchronous rectifier is increased.

5. The synchronous rectification method for adaptive on-time of a three-phase LLC circuit according to claim 1, characterized in that, The adaptive on-time synchronous rectification method for the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at an underresonant frequency, if the total output current value at the turn-off time of the synchronous rectifier is less than the sum of the minimum current value and the second preset compensation value, then the on-time of the synchronous rectifier is maintained; if the turn-off time of the synchronous rectifier is not within the second judgment interval, then the on-time of the synchronous rectifier is increased.

6. The synchronous rectification method for adaptive on-time of a three-phase LLC circuit according to claim 3, characterized in that, The adaptive conduction time synchronous rectification method for the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at the resonant frequency, if the total output current value at the turn-off time of the synchronous rectifier is less than the sum of the minimum current value and the third preset compensation value, then the conduction time of the synchronous rectifier is maintained; if the conduction time of the synchronous rectifier is not within the third judgment interval, then the conduction time of the synchronous rectifier is increased.

7. The synchronous rectification method for adaptive on-time of a three-phase LLC circuit according to claim 3, characterized in that, The adaptive conduction time synchronous rectification method for the three-phase LLC circuit further includes: when the three-phase LLC circuit operates at the resonant frequency, if the total output current value at the conduction time of the synchronous rectifier is less than the sum of the minimum current value and the fourth preset compensation value, then the conduction time of the synchronous rectifier is maintained; if the turn-off time of the synchronous rectifier is not in the fourth judgment interval, then the conduction time of the synchronous rectifier is increased.

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