Synchronous rectifier control method for converter, and circuit and application apparatus

Abstract

Provided in the present disclosure are a synchronous rectifier control method for a converter, and a circuit and an application apparatus. A converter comprises a transformer, a main switch transistor, a synchronous rectifier transistor, a main control module and a synchronous drive module, wherein one end of the synchronous drive module is connected to the main control module, and the other end of the synchronous drive module is connected to the synchronous rectifier transistor. The method comprises: a synchronous drive module acquiring a feedback signal of a body diode of a synchronous rectifier transistor (S302); the synchronous drive module receiving a PWM signal sent by a main control module (S304); and the synchronous drive module outputting a drive signal on the basis of the feedback signal and the PWM signal, wherein the drive signal is used for adjusting the turn-off timing of the synchronous rectifier transistor (S306). A feedback signal of a body diode of a synchronous rectifier transistor is detected by means of a synchronous drive module, a drive signal of the synchronous rectifier transistor is adjusted on the basis of the feedback signal and a PWM signal output by a main control module, and the turn-off timing of the synchronous rectifier transistor is changed by means of adjusting a falling edge, thereby realizing the accurate turn-off of the synchronous rectifier transistor and avoiding the problems of shoot-through of a bridge arm and increased loss.

Description

Synchronous Rectification Control Method, Circuit and Application Device of Converter

[0001] This application claims the priority of the Chinese invention patent application with the application number 202510114580.5 and the invention title "Synchronous Rectification Control Method, Circuit and Application Device of Converter" submitted to the Chinese Patent Office on January 23, 2025, the entire content of which is incorporated into this application by reference. Technical Field

[0002] This application relates to the field of power electronics technology, and particularly relates to a synchronous rectification control method, circuit, converter, power supply device, storage medium and program product of a converter. Background Art

[0003] In a switching power supply, in order to improve the power density, the switching frequency is increased, which directly leads to an increase in switching losses. The LLC resonant converter circuit has the characteristic of soft switching, and can achieve zero-voltage switching of the primary switching tube and zero-current turn-off of the secondary synchronous rectifier tube within a wide range, reducing switching losses. In order for the LLC converter to achieve low losses, the synchronous rectifier tube needs to realize the function of synchronous rectification output. Therefore, precise turn-off of the synchronous rectifier tube is required. If the synchronous rectifier tube is turned off too early, it will also cause an increase in the working time of the current in the body diode; if it is turned off too late, it will cause bridge arm short-circuit or a new low-resistance freewheeling loop to appear, which is very harmful.

[0004] In the prior art, when the synchronous rectifier tube is in the half-switching period, if fsw (switching frequency) < fs (LLC operating frequency), the turn-on time of the synchronous rectifier tube is equal to half of the resonant period. However, this scheme cannot ensure that the synchronous rectifier tube is accurately turned on or off at the zero-crossing point of the output current, and the load and input voltage will affect the LLC operating frequency. Especially in a three-phase topology, when the three-phase loads are unbalanced, the phenomenon of midpoint drift will occur. Premature or late turn-on and turn-off of the synchronous rectifier tube (which can also be simply referred to as SR) will lead to serious consequences such as low efficiency, negative current or excessive drain-source stress.

[0005] Therefore, there is an urgent need for a synchronous rectification control method to achieve the precise turn-off effect of the synchronous rectifier tube and avoid the problems of bridge arm short-circuit and increased losses. Summary of the Invention

[0006] The embodiments of this application provide a synchronous rectification control method, circuit, converter, power supply device, storage medium and program product of a converter, so as to achieve the precise turn-off of the synchronous rectifier tube and avoid the problems of bridge arm short-circuit and increased losses.

[0007] In a first aspect, embodiments of this application provide a synchronous rectification control method for a converter. The converter includes a transformer, a main switching transistor, a synchronous rectifier transistor, a main control module, and a synchronous drive module. One end of the synchronous drive module is connected to the main control module, and the other end of the synchronous drive module is connected to the synchronous rectifier transistor. The method includes:

[0008] The synchronous drive module obtains the feedback signal from the body diode of the synchronous rectifier.

[0009] The synchronous drive module receives the PWM signal sent by the main control module;

[0010] The synchronous drive module outputs a drive signal based on the feedback signal and the PWM signal. The drive signal is used to adjust the turn-off timing of the synchronous rectifier tube.

[0011] In one embodiment, the synchronous drive module outputs a drive signal based on the feedback signal and the PWM signal, specifically including:

[0012] The synchronous drive module determines the conduction time of the body diode based on the feedback signal;

[0013] The synchronous drive module determines the conduction state of the synchronous rectifier tube based on the conduction time of the body diode;

[0014] The synchronous drive module adjusts the falling edge transmission time of the PWM signal according to the conduction state of the synchronous rectifier diode, so as to adjust the turn-off timing of the synchronous rectifier diode.

[0015] In one embodiment, the synchronous drive module determines the conduction state of the synchronous rectifier based on the conduction time of the body diode, specifically including:

[0016] If the conduction time of the body diode is greater than or equal to the first threshold, then the synchronous rectifier is determined to be turned off too early.

[0017] The synchronous drive module performs logical operations on the feedback signal and the PWM signal, and then outputs a first drive signal. This first drive signal is used to control the delayed turn-off of the synchronous rectifier diode; or,

[0018] If the conduction time of the body diode is less than or equal to the second threshold, then the synchronous rectifier is determined to be turned off too late.

[0019] The synchronous drive module performs logical operations on the feedback signal and the PWM signal and outputs a second drive signal, which is used to control the synchronous rectifier tube to turn off in advance.

[0020] In one embodiment, the synchronous drive module performs logical operations on the feedback signal and the PWM signal and outputs a first drive signal; the synchronous drive module performs logical operations on the feedback signal and the PWM signal and outputs a second drive signal, specifically including:

[0021] When the PWM signal is high and the feedback signal is low, the synchronous drive module outputs a high-level drive signal. When the feedback signal is low, the body diode of the synchronous rectifier is turned on.

[0022] When the PWM signal is low and the feedback signal is high, the synchronous drive module outputs a low-level drive signal.

[0023] In one embodiment, obtaining the feedback signal of the body diode of the synchronous rectifier specifically includes:

[0024] The synchronous drive module obtains the output voltage of the synchronous rectifier tube;

[0025] The synchronous drive module determines the feedback signal of the body diode based on the output voltage. The feedback signal is used to determine the conduction state of the body diode.

[0026] In one embodiment, the synchronous rectifier includes a first switch and a second switch, which are connected in series; the main control module stores a first carrier signal and a second carrier signal.

[0027] Before the synchronous drive module receives the PWM signal sent by the main control module, it also includes:

[0028] The main control module adjusts the first carrier signal and the second carrier signal according to the feedback signal, and compares the adjusted first carrier signal and the second carrier signal with the modulation signal to generate a PWM signal;

[0029] The main control module sends a PWM signal to the synchronous drive module. The PWM signal is used to control the turn-off timing of the first and second switching transistors, wherein the first and second switching transistors are complementary in conduction.

[0030] In one embodiment, the synchronous rectifier includes a first switch and a second switch, which are connected in series; the synchronous drive module stores a third carrier signal of the first switch and a fourth carrier signal of the second switch.

[0031] Before the synchronous drive module receives the PWM signal sent by the main control module, it also includes:

[0032] The main control module adjusts the third and fourth carrier signals based on the feedback signal, and then compares the adjusted third and fourth carrier signals with the modulation signal to generate a PWM signal.

[0033] The main control module sends a PWM signal to the synchronous drive module. The PWM signal is used to control the turn-off timing of the first and second switching transistors.

[0034] In one embodiment, the main control module is also used to adjust the third carrier signal and the fourth carrier signal so that the first switch and the second switch are complementary in conduction.

[0035] In one embodiment, the main control module is also used to adjust the duty cycle and dead time of the PWM signal according to the drive signal of the main switch.

[0036] Secondly, embodiments of this application also provide a synchronous rectification control circuit for a converter, including a main control module and a synchronous rectification drive module, wherein the main control module and the synchronous rectification drive module are connected to the converter;

[0037] The converter includes a transformer, a main switch, and a synchronous rectifier. The main switch is connected to the synchronous rectifier through the transformer, and the output of the synchronous rectifier is connected to the load after being filtered by a filter capacitor.

[0038] The main control module is connected to the control terminal of the main switch tube, one end of the synchronous rectification drive module is connected to the main control module, and the other end of the synchronous rectification drive module is connected to the synchronous rectifier tube;

[0039] The synchronous rectification drive module is used to obtain the feedback signal from the synchronous rectifier tube, receive the PWM signal sent by the main control module, and output the drive signal according to the feedback signal and the PWM signal. The drive signal is used to adjust the conduction time of the synchronous rectifier tube.

[0040] In one embodiment, the converter is a three-phase LLC converter, wherein the main switch adopts a three-phase half-bridge topology, and the synchronous rectifier adopts an N-wave or full-bridge rectifier topology.

[0041] Thirdly, embodiments of this application also provide a converter, including a main control module and a synchronous drive module. The synchronous drive module is used to execute the synchronous rectification control method of the converter executed by the synchronous drive module as described above, and the main control module is used to execute the synchronous rectification control method of the converter executed by the main control module as described above.

[0042] Fourthly, embodiments of this application provide a power supply device, including the converter as described above.

[0043] Fifthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement any of the methods described above.

[0044] Sixthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements any of the methods described above.

[0045] This application provides a synchronous rectification control method, circuit, converter, power supply device, storage medium, and program product for a converter. The converter includes a transformer, a main switching transistor, a synchronous rectifier diode, a main control module, and a synchronous drive module. One end of the synchronous drive module is connected to the main control module, and the other end is connected to the synchronous rectifier diode. The method includes: the synchronous drive module acquiring a feedback signal from the body diode of the synchronous rectifier diode; the synchronous drive module receiving a PWM signal sent by the main control module; and the synchronous drive module outputting a drive signal based on the feedback signal and the PWM signal. The drive signal is used to adjust the turn-off timing of the synchronous rectifier diode. By detecting the feedback signal from the body diode of the synchronous rectifier diode and adjusting the drive signal of the synchronous rectifier diode according to the feedback signal and the PWM signal output by the main control module, the turn-off timing of the synchronous rectifier diode is changed by adjusting the falling edge, thereby achieving precise turn-off of the synchronous rectifier diode and avoiding problems such as bridge arm shoot-through and increased losses. Attached Figure Description

[0046] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0047] Figure 1 is a schematic diagram of a converter provided in an embodiment of this application;

[0048] Figure 2 shows the main topology of a three-phase LLC DC-DC converter provided in an embodiment of this application;

[0049] Figure 3 is a flowchart of a synchronous rectification control method for a converter provided in an embodiment of this application;

[0050] Figure 4 is a flowchart of a synchronous rectification control method provided in an embodiment of this application;

[0051] Figure 5 is a schematic diagram of the structure of a synchronous drive module provided in an embodiment of this application;

[0052] Figure 6 is a schematic diagram of EPWM driving provided in an embodiment of this application;

[0053] Figure 7 is a schematic diagram of the adjustment of the synchronous rectifier tube turning off too early according to an embodiment of this application;

[0054] Figure 8 is a schematic diagram of APWM drive provided in an embodiment of this application;

[0055] Figure 9 is a schematic diagram of the output drive signal using APWM technology and a synchronous drive module according to an embodiment of this application;

[0056] Figure 10 is a schematic diagram of adjusting the duty cycle according to an embodiment of this application;

[0057] Figure 11 shows a topology of two sets of synchronous rectifier tubes connected in parallel according to an embodiment of this application.

[0058] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0059] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same or similar reference numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0060] Explanation of nouns or terms:

[0061] EPWM (Enhanced Pulse Width Modulation): An enhanced PWM technology that typically offers higher resolution and more feature options.

[0062] APWM (Asynchronous Pulse Width Modulation): An asynchronous PWM control method, as opposed to synchronous PWM.

[0063] In switching power supplies, increasing the switching frequency to improve power density directly leads to increased switching losses. LLC resonant converter circuits feature soft turn-on, enabling zero-voltage turn-on of the primary-side switch and zero-current turn-off of the secondary-side synchronous rectifier over a wide range, thus reducing switching losses. For low-loss operation, the synchronous rectifier in an LLC converter needs to perform synchronous rectification output. Therefore, precise turn-off of the synchronous rectifier is crucial. Turning it off too early increases the operating time of the current in the body diode; turning it off too late can lead to bridge arm shoot-through or the emergence of new low-impedance freewheeling loops, which are highly detrimental.

[0064] In the prior art, for the synchronous rectifier tube, during the half switching period, if fsw (switching frequency) < fs (LLC operating frequency), the turn-on time of the synchronous rectifier tube is equal to half of the resonant period. However, this solution cannot ensure the precise turn-on or turn-off of the synchronous rectifier tube at the zero crossing point of the output current, and the load and input voltage will affect the LLC operating frequency. Especially in a three-phase topology, when the three-phase load is unbalanced, the phenomenon of midpoint drift will occur. Premature or late turn-on and turn-off of the SR will lead to serious consequences such as low efficiency, negative current, or excessive drain-source stress.

[0065] The present application provides a synchronous rectification control method for a converter. The converter includes a transformer, a main switch tube, a synchronous rectifier tube, a main control module, and a synchronous drive module. One end of the synchronous drive module is connected to the main control module, and the other end of the synchronous drive module is connected to the synchronous rectifier tube. The method includes: the synchronous drive module obtains the feedback signal of the body diode of the synchronous rectifier tube; the synchronous drive module receives the PWM signal sent by the main control module; the synchronous drive module outputs a drive signal according to the feedback signal and the PWM signal, and the drive signal is used to adjust the turn-off timing of the synchronous rectifier tube. By detecting the feedback signal of the body diode of the synchronous rectifier tube through the synchronous drive module, adjusting the drive signal of the synchronous rectifier tube according to the feedback signal and the PWM signal output by the main control module, and changing the turn-off timing of the synchronous rectifier tube by adjusting the falling edge, the present application achieves precise turn-off of the synchronous rectifier tube and avoids problems such as arm short-circuit and increased loss.

[0066] The technical solution of the present application and how the technical solution of the present application solves the above technical problems will be described in detail below with specific embodiments. These specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below with reference to the accompanying drawings.

[0067] As shown in FIG. 1, FIG. 1 is a schematic structural diagram of a converter provided by an embodiment of the present application. The converter includes a transformer, a main switch tube, a synchronous rectifier tube, a main control module, and a synchronous drive module. One end of the synchronous drive module is connected to the main control module, and the other end of the synchronous drive module is connected to the synchronous rectifier tube. As shown in FIG. 2, FIG. 2 is a main topology structure of a three-phase LLC DC-DC converter provided by an embodiment of the present application. The main switch tube adopts a three-phase half-bridge structure, and the synchronous rectifier tube adopts a three-phase full-wave rectification structure. Among them, Q1, Q2, Q3, Q4, Q5, and Q6 are the main switch tubes composed of six MOS tubes, and the connection method is as shown in FIG. 2, C rA 、C rB 、C rC are the resonant capacitors of phase A, phase B, and phase C respectively, and L rA 、L rB 、L rC are the resonant inductors of phase A, phase B, and phase C respectively, and TrA T rB T rC These are the magnetizing inductances in a three-phase delta-connected transformer, S R1 S R2 S R3 S R4 S R5 S R6 For six synchronous rectifier MOSFETs, C o For the output filter capacitor, R o The load is an inductor L. rX T rX and capacitor C rX L m Connected in parallel with a transformer, it can be determined by the transformer's magnetizing inductance T. rX To achieve this; resonant capacitor C rX Connected in series in the primary loop, it also serves to block DC. Figure 2 is just one example of a converter; other types of topologies are also possible.

[0068] This application provides a synchronous rectification control method for a converter, as shown in Figure 3. Figure 3 is a flowchart of the synchronous rectification control method for a converter provided in an embodiment of this application. The method includes steps S302 to S306. The control method of this embodiment can be directly applied to the embodiments in Figures 1 and 2, and can also be applied to other topologies. This application does not limit the application here.

[0069] Step S302: The synchronous drive module obtains the feedback signal of the body diode of the synchronous rectifier.

[0070] Specifically, when the synchronous rectifier is turned on, current flows through it, and the body diode of the synchronous rectifier is in an open state. When the synchronous rectifier is turned off, current flows through the body diode, but if the current flows through the body diode for too long, it will increase losses. Therefore, the feedback signal of the body diode of the synchronous rectifier is obtained through the synchronous drive module, thereby obtaining the on-state of the synchronous rectifier.

[0071] In one embodiment, step S302 specifically includes the following steps:

[0072] The synchronous drive module obtains the output voltage of the synchronous rectifier tube;

[0073] The synchronous drive module determines the feedback signal of the body diode based on the output voltage. The feedback signal is used to determine the conduction state of the body diode.

[0074] The synchronous drive module obtains the output voltage of the synchronous rectifier and analyzes the feedback signal of the body diode based on the output voltage of the synchronous rectifier, thereby obtaining the conduction state of the synchronous rectifier.

[0075] Step S304: The synchronous drive module receives the PWM signal sent by the main control module.

[0076] Specifically, the PWM signal sent by the main control module is used to control the turn-on and turn-off times of the synchronous rectifier tube; secondly, the main control module also controls the turn-on and turn-off of the main switching tube.

[0077] Step S306: The synchronous drive module outputs a drive signal based on the feedback signal and the PWM signal. The drive signal is used to adjust the turn-off timing of the synchronous rectifier tube.

[0078] Specifically, the synchronous drive module adjusts the drive signal of the synchronous rectifier in real time based on the feedback signal and the PWM signal. This application detects the conduction state of the body diode of the synchronous rectifier and adjusts the falling edge of the PWM signal to enable the synchronous rectifier to be precisely turned off, thereby improving the overall output efficiency of the machine. Secondly, the control method is simple and highly reliable.

[0079] In one embodiment, step S306 specifically includes steps S402 to S406, as shown in FIG4. FIG4 is a flowchart of a synchronous rectification control method provided in an embodiment of the present application.

[0080] Step S402: The synchronous drive module determines the conduction time of the body diode based on the feedback signal.

[0081] Step S404: The synchronous drive module determines the conduction state of the synchronous rectifier tube based on the conduction time of the body diode.

[0082] Specifically, the conduction state of the synchronous rectifier is determined by the conduction time of the body diode, and the turn-off status of the synchronous rectifier is detected in a timely manner to avoid premature turn-off. The PWM signal is then adjusted in a timely manner according to the conduction time of the body diode to output a reliable drive signal to drive the synchronous rectifier.

[0083] Step S406: The synchronous drive module adjusts the falling edge transmission time of the PWM signal according to the conduction state of the synchronous rectifier tube, so as to adjust the turn-off timing of the synchronous rectifier tube.

[0084] In one embodiment, step S404 specifically includes the following steps:

[0085] If the conduction time of the body diode is greater than or equal to the first threshold, then the synchronous rectifier is determined to be turned off too early.

[0086] The synchronous drive module performs logical operations on the feedback signal and the PWM signal, and then outputs a first drive signal. This first drive signal is used to control the delayed turn-off of the synchronous rectifier diode; or,

[0087] If the conduction time of the body diode is less than or equal to the second threshold, then the synchronous rectifier is determined to be turned off too late.

[0088] The synchronous drive module performs logical operations on the feedback signal and the PWM signal and outputs a second drive signal, which is used to control the synchronous rectifier tube to turn off in advance.

[0089] In one embodiment, the first threshold is greater than the second threshold. The values ​​of the first threshold and the second threshold are determined according to the actual situation, and this application does not impose any restrictions on them.

[0090] As shown in Figure 5, which is a schematic diagram of the synchronous drive module provided in an embodiment of this application, the synchronous drive module includes a logic gate processing module, a diode forward voltage drop detection module, and a trigger. The diode forward voltage drop detection module determines the conduction status of the body diode based on the output voltage of the synchronous rectifier and outputs a feedback signal. The logic gate processing processes the PWM signal and the feedback signal through logic processing and the trigger to output a drive signal, thereby driving the synchronous rectifier to precisely turn off, avoiding premature or late turn-off of the synchronous rectifier, which leads to low efficiency, negative current, and excessive drain-source stress.

[0091] In one embodiment, the synchronous drive module performs logical operations on the feedback signal and the PWM signal to output a first drive signal; the synchronous drive module performs logical operations on the feedback signal and the PWM signal to output a second drive signal, specifically including the following steps:

[0092] When the PWM signal is high and the feedback signal is low, the synchronous drive module outputs a high-level drive signal. When the feedback signal is low, the body diode of the synchronous rectifier is turned on.

[0093] When the PWM signal is low and the feedback signal is high, the synchronous drive module outputs a low-level drive signal.

[0094] Table 1 Truth table of input and output signals of the synchronous drive module

[0095] The internal S and Q pins are the trigger pins. When the body diode of the synchronous rectifier is turned on, the feedback signal is low, meaning the synchronous rectifier is off. As shown in Table 1, the synchronous drive module has four possible scenarios based on the feedback and PWM signals: First, when both the feedback and PWM signals are high: the drive signal remains the same as the previous stage, and the system does not change the current drive state because the body diode is not turned on and the PWM signal is high. Second, when both the feedback and PWM signals are high: the drive signal is low. When the body diode is not turned on and the PWM signal is low, the synchronous rectifier is turned off, ensuring timely shutdown. Third, when both the feedback and PWM signals are high: the drive signal is high. When both the body diode and PWM signal are high, the synchronous rectifier is turned on, requiring it to be on to improve efficiency. The fourth scenario is when the feedback signal is low and the PWM signal is low: the drive signal is low, keeping the synchronous rectifier tube off, because the PWM signal is low.

[0096] In one embodiment, please refer to Figure 2. Figure 2 shows a synchronous rectifier with three bridge arms. This embodiment uses one bridge arm as an example. The synchronous rectifier includes a first switch and a second switch, which are connected in series. The main control module stores a first carrier signal and a second carrier signal. Before step S304, the following steps are also included:

[0097] The main control module adjusts the first carrier signal and the second carrier signal according to the feedback signal, and then compares the adjusted first carrier signal and the second carrier signal with the modulation signal to generate a PWM signal.

[0098] The main control module sends a PWM signal to the synchronous drive module. The PWM signal is used to control the turn-off timing of the first and second switching transistors, wherein the first and second switching transistors are complementary in conduction.

[0099] As shown in Figure 6, Figure 6 is a schematic diagram of EPWM drive provided in an embodiment of this application. The main control module of the three-phase LLC main power topology includes EPWM1 ​​to EPWM6 modules, which are used to modulate the PWM signals of the main switching transistors and synchronous rectifier transistors. Among them, the main switching transistors Q1 to Q6 on the primary side use the PWM signals output by the EPWM1 ​​to EPWM3 modules in the main control module. The carrier signal CMP1A configured for phase A of the main switching transistor is 0*P1; the carrier signal CMP1B is 1 / 2*P2; the carrier signal CMP2A configured for phase B is 1 / 3*P3; CMP2B is 5 / 6*P4; the carrier signal CMP3A configured for phase C is 2 / 3*P5; CMP3B is 1 / 6*P6. Among them, P1, P2, P3, P4, P5 and P6 are the period, and P1, P2, P3, P4, P5 and P6 can be the same value or different values. The synchronous rectifier diodes SR1 to SR6 are controlled by EPWM4 to EPWM6 modules and a diode forward voltage drop detection module. The control of the falling edge of the PWM signal by EPWM4 to EPWM6 differs from that of EPWM1 ​​to EPWM3, but otherwise they are identical. The first feedback signal and the second feedback signal are the SR1 and SR2 signals detected by the diode forward voltage drop detection module. Both the first and second feedback signals have valid levels before and after the synchronous rectifier diodes are turned on. These signals are filtered in the main control module. In this embodiment, the main control module only obtains the feedback signal at the moment the synchronous rectifier diodes are turned off to adjust the falling edge of the PWM4 signal. Additionally, the feedback signal before the synchronous rectifier diodes are turned on is automatically enabled by the hardware logic in the diode forward voltage drop detection module according to Table 1. This embodiment uses synchronous rectifier diodes SR1 and SR2 as examples; the adjustment principle of the other bridge arm synchronous rectifier diodes is the same as that of SR1 and SR2.

[0100] As shown in Figure 7, Figure 7 is a schematic diagram of the adjustment of synchronous rectifier turn-off too early according to an embodiment of this application. The main control module obtains the effective level time of the feedback signal. Here, the effective level is a low level, i.e., the conduction time of the body diode. If the conduction time of the body diode is greater than or equal to the first threshold, it is determined that the synchronous rectifier turn-off is too early. The value of the carrier signal CMPx of EPWM4 to EPWM6 is adjusted. After the EPWM configuration takes effect, a delayed turn-off PWM signal is issued, which is then applied to the synchronous rectifier after logical operation by the synchronous drive module. Optionally, the carrier signal can be adjusted in a stepwise manner, which can control the turn-off time of the synchronous rectifier in real time and adjust it gradually. If the conduction time of the body diode is less than or equal to the second threshold, it is determined that the synchronous rectifier turn-off is too late. Similarly, the value of the carrier signal CMPx of EPWM4 to EPWM6 is adjusted. After the EPWM configuration, an early turn-off PWM signal is issued and applied to the diode conduction voltage drop detection module, which is then applied to the synchronous rectifier drive after logical operation.

[0101] In one embodiment, the synchronous rectifier includes a first switch and a second switch, which are connected in series; the synchronous drive module stores a third carrier signal of the first switch and a fourth carrier signal of the second switch; before step S304, the following steps are also included:

[0102] The main control module adjusts the third and fourth carrier signals based on the feedback signal, and then compares the adjusted third and fourth carrier signals with the modulation signal to generate a PWM signal.

[0103] The main control module sends a PWM signal to the synchronous drive module. The PWM signal is used to control the turn-off timing of the first and second switching transistors.

[0104] As shown in Figure 8, Figure 8 is a schematic diagram of APWM drive provided in an embodiment of this application. When the number of switching transistors in the topology of the embodiment in Figure 2 or other topologies is large, the resources of the main control module are limited. If EPWM technology is used to output PWM signals, it is difficult to support the driving of all switching transistors. Therefore, this embodiment uses APWM technology to drive the synchronous rectifier transistors. Taking the topology in Figure 2 as an example, the main switching transistors Q1 to Q6 are directly driven by the EPWM1 ​​to EPWM6 modules in the main control module. The configuration of the carrier signal is the same as that in the embodiment in Figure 6, and will not be described again here. The PWM signal width of the main switching transistors is adjusted by setting the dead time of the rising edge. The synchronous rectifier transistors SR1 to SR6 are controlled by the APWM1 to APWM6 modules and the synchronous drive module. In order to achieve a 120-degree phase shift of the three-phase PWM waves and to generate output for LLC frequency converter control, the rising edge drive of the synchronous rectifier transistors is synchronized with the rising edge drive of the main switching transistors PWM1, PWM3 and PWM5, as shown in Figure 8.

[0105] The falling edge of the drive signal for the synchronous rectifier diodes is controlled by the synchronous drive module. Taking phase A as an example, the feedback signal is the body diode conduction sensing signal inside the diode forward voltage drop detection module. The upper and lower bridge arms of the same phase, SR1 and SR2 on the secondary side, generate complementary waves. APWM1 uses a third carrier signal of 1 / 2PRD, i.e., APWM1.ACMP = 1 / 2PRD, to adjust the falling edge of the first switch SR1. APWM2 uses a fourth carrier signal of PRD-MIN (MIN being the minimum value required to ensure the drive is pulled low), to adjust the falling edge of the second switch SR2. Here, PRD is the period of the PWM signal.

[0106] In one embodiment, as shown in FIG9, FIG9 is a schematic diagram of the output drive signal using APWM technology and a synchronous drive module according to an embodiment of the present application. The main control module is also used to adjust the third carrier signal and the fourth carrier signal so that the first switch and the second switch are complementaryly turned on.

[0107] In one embodiment, the main control module is also used to adjust the duty cycle and dead time of the PWM signal according to the drive signal of the main switch.

[0108] Specifically, the embodiments in Figures 6 to 9 are all exemplified using a 50% duty cycle. As shown in Figure 10, Figure 10 is a schematic diagram of adjusting the duty cycle according to an embodiment of this application. This application also synchronously adjusts the duty cycle of the synchronous rectifier and sets the dead time based on the drive signal of the main switch. The pulse width modulation is achieved by delaying the rising edge of the drive by setting the dead time. The delay length Td can be calculated using the formula: Td = dead time + (0.5 * period - duty cycle * period). The duty cycle is adjusted within the range of 0 to 0.5.

[0109] This application embodiment also provides a synchronous rectification control circuit for a converter, including a main control module and a synchronous rectification drive module, which are connected to the converter. The converter includes a transformer, a main switching transistor, and a synchronous rectifier transistor. The main switching transistor is connected to the synchronous rectifier transistor through the transformer, and the output of the synchronous rectifier transistor is connected to the load after being filtered by a filter capacitor. The main control module is connected to the control terminal of the main switching transistor, one end of the synchronous rectification drive module is connected to the main control module, and the other end of the synchronous rectification drive module is connected to the synchronous rectifier transistor. The synchronous rectification drive module is used to acquire the feedback signal of the synchronous rectifier transistor, receive the PWM signal sent by the main control module, and output a drive signal according to the feedback signal and the PWM signal. The drive signal is used to adjust the conduction time of the synchronous rectifier transistor.

[0110] In one embodiment, the converter is a three-phase LLC converter, wherein the main switch adopts a three-phase half-bridge topology, and the synchronous rectifier adopts an N-wave or full-bridge rectifier topology.

[0111] Changing the main circuit topology in Figure 2 from three-phase to single-phase, changing the full-bridge structure of the main switch to a half-bridge structure, and changing the LLC structure to a phase-shifted full-bridge structure; or changing the secondary side to n full-wave or full-bridge rectifiers in parallel, all fall within the scope of this embodiment. As shown in Figure 11, Figure 11 is a topology structure of two sets of synchronous rectifiers connected in parallel provided in an embodiment of this application.

[0112] This application embodiment also provides a converter, including a main control module and a synchronous drive module. The synchronous drive module is used to execute the synchronous rectification control method of any of the converters described above, and the main control module is used to execute the synchronous rectification control method of any of the converters described above.

[0113] This application provides a power supply device, including the converter as described above.

[0114] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0115] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0116] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0117] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0118] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0119] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static 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), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0120] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0121] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may take electrical, mechanical, or other forms.

[0122] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0123] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0124] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0125] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0126] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A synchronous rectification control method for a converter, characterized in that, The converter includes a transformer, a main switching transistor, a synchronous rectifier transistor, a main control module, and a synchronous drive module. One end of the synchronous drive module is connected to the main control module, and the other end of the synchronous drive module is connected to the synchronous rectifier transistor. The method includes: The synchronous drive module acquires the feedback signal of the body diode of the synchronous rectifier tube; The synchronous drive module receives the PWM signal sent by the main control module; The synchronous drive module outputs a drive signal based on the feedback signal and the PWM signal, and the drive signal is used to adjust the turn-off timing of the synchronous rectifier tube.

2. The synchronous rectification control method according to claim 1, characterized in that, The synchronous drive module outputs a drive signal based on the feedback signal and the PWM signal, specifically including: The synchronous drive module determines the conduction time of the body diode based on the feedback signal; The synchronous drive module determines the conduction state of the synchronous rectifier tube based on the conduction time of the body diode. The synchronous drive module adjusts the falling edge transmission time of the PWM signal according to the conduction state of the synchronous rectifier tube, so as to adjust the turn-off timing of the synchronous rectifier tube.

3. The synchronous rectification control method according to claim 2, characterized in that, The synchronous drive module determines the conduction state of the synchronous rectifier diode based on the conduction time of the body diode, specifically including: If the conduction time of the body diode is greater than or equal to the first threshold, then it is determined that the synchronous rectifier is turned off too early. The synchronous drive module performs logical operations on the feedback signal and the PWM signal, and outputs a first drive signal. This first drive signal is used to control the synchronous rectifier diode to turn off with a delay; or... If the conduction time of the body diode is less than or equal to the second threshold, then it is determined that the synchronous rectifier is turned off too late. The synchronous drive module performs logical operations on the feedback signal and the PWM signal and outputs a second drive signal, which is used to control the synchronous rectifier tube to turn off in advance.

4. The synchronous rectification control method according to claim 3, characterized in that, The synchronous drive module performs logical operations on the feedback signal and the PWM signal to output a first drive signal; the synchronous drive module performs logical operations on the feedback signal and the PWM signal to output a second drive signal, specifically including: The synchronous drive module outputs a high-level drive signal when the PWM signal is high and the feedback signal is low, wherein the body diode of the synchronous rectifier is turned on when the feedback signal is low. The synchronous drive module outputs a low-level drive signal when the PWM signal is low and the feedback signal is high.

5. The synchronous rectification control method according to claim 1, characterized in that, Obtaining the feedback signal of the body diode of the synchronous rectifier specifically includes: The synchronous drive module acquires the output voltage of the synchronous rectifier tube; The synchronous drive module determines the feedback signal of the body diode based on the output voltage, and the feedback signal is used to determine the conduction state of the body diode.

6. The synchronous rectification control method according to claim 1, characterized in that, The synchronous rectifier includes a first switch and a second switch, which are connected in series; the main control module stores a first carrier signal and a second carrier signal. Before the synchronous drive module receives the PWM signal sent by the main control module, it further includes: The main control module adjusts the first carrier signal and the second carrier signal according to the feedback signal, and generates the PWM signal by comparing the adjusted first carrier signal and the second carrier signal with the modulation signal. The main control module sends the PWM signal to the synchronous drive module. The PWM signal is used to control the turn-off timing of the first switch and the second switch, wherein the first switch and the second switch are complementary in conduction.

7. The synchronous rectification control method according to claim 1, characterized in that, The synchronous rectifier includes a first switch and a second switch, which are connected in series; the synchronous drive module stores the third carrier signal of the first switch and the fourth carrier signal of the second switch. Before the synchronous drive module receives the PWM signal sent by the main control module, it further includes: The main control module adjusts the third carrier signal and the fourth carrier signal according to the feedback signal, and generates the PWM signal by comparing the adjusted third carrier signal and the fourth carrier signal with the modulation signal. The main control module sends the PWM signal to the synchronous drive module. The PWM signal is used to control the turn-off timing of the first switch and the second switch.

8. The synchronous rectification control method according to claim 7, characterized in that, The main control module is also used to adjust the third carrier signal and the fourth carrier signal so that the first switch and the second switch are complementary in conduction.

9. The synchronous rectification control method according to claim 7, characterized in that, The main control module is also used to adjust the duty cycle and dead time of the PWM signal according to the drive signal of the main switch.

10. A synchronous rectification control circuit for a converter, characterized in that, It includes a main control module and a synchronous rectification drive module, which are connected to the converter; The converter includes a transformer, a main switch, and a synchronous rectifier; the main switch is connected to the synchronous rectifier through the transformer, and the output of the synchronous rectifier is connected to the load after being filtered by a filter capacitor; The main control module is connected to the control terminal of the main switch tube, one end of the synchronous rectification drive module is connected to the main control module, and the other end of the synchronous rectification drive module is connected to the synchronous rectifier tube; The synchronous rectification drive module is used to acquire the feedback signal of the synchronous rectifier tube, receive the PWM signal sent by the main control module, and output a drive signal according to the feedback signal and the PWM signal. The drive signal is used to adjust the conduction time of the synchronous rectifier tube.

11. The synchronous rectification control circuit of the converter according to claim 10, characterized in that, The converter is a three-phase LLC converter, wherein the main switch adopts a three-phase half-bridge topology, and the synchronous rectifier adopts an N-wave or full-bridge rectifier topology.

12. A converter, characterized in that, It includes a main control module and a synchronous drive module, wherein the synchronous drive module is used to execute the synchronous rectification control method of the converter as described in any one of claims 1-5, and the main control module is used to execute the synchronous rectification control method of the converter as described in any one of claims 6-9.

13. A power supply device, characterized in that, Includes the converter as described in claim 12.

14. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any one of claims 1-9.

15. A computer program product, characterized in that, Includes a computer program that, when executed by a processor, implements the method described in any one of claims 1-9.

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