Inverter and zero-voltage switching control circuit and method thereof

Abstract

This application relates to the field of switching power supply technology, and discloses a converter and its zero-voltage switching control circuit and method. The converter includes a transformer and a main switching transistor, with the main switching transistor corresponding to the primary winding of the transformer. The zero-voltage switching control circuit includes: a zero-voltage switching winding; and a clamping control unit connected to the zero-voltage switching winding. The clamping control unit includes a clamping switching transistor, and is configured to control the clamping switching transistor to turn on before the main switching transistor is turned on, thereby clamping the voltage of the zero-voltage switching winding. The clamped voltage of the zero-voltage switching winding is coupled to the primary winding through the transformer, causing the voltage across the main switching transistor to drop to zero before the main switching transistor is turned on. This application can achieve zero-voltage switching more ideally, not only avoiding hard switching during transients but also eliminating the need to adjust the appropriate reverse excitation current, greatly improving the system efficiency and reliability.

Description

Technical Field

[0001] This application relates to the field of switching power supply technology, and in particular to a zero-voltage switching control circuit for a converter, a converter, and a zero-voltage switching control method for a converter. Background Technology

[0002] With the rapid development of power electronics technology, the market demands increasingly smaller size, higher efficiency, and higher reliability from switching converters. Flyback converters, due to their simple topology and fewer components, are widely used in low-power switching power supplies. However, the hard switching of the primary-side switching transistors in ordinary flyback converters and the inability to recover leakage inductance energy result in significant losses.

[0003] While AHB (Asymmetric Half-Bridge) flyback converters can achieve ZVS (Zero Voltage Switching) and are more efficient than ordinary flyback converters, their performance cannot be optimized when achieving ZVS. For example, the adjustment of ZVS is not adaptive, resulting in either incomplete ZVS on the primary-side switch or a larger reverse magnetizing current, leading to energy cycling and affecting efficiency. Alternatively, even if the ZVS adjustment is an adaptive closed-loop control, the closed-loop control may not adjust to an appropriate reverse magnetizing current during transients, resulting in hard switching, high device stress, and affecting system reliability. Summary of the Invention

[0004] This application provides a zero-voltage switching control circuit, method, and converter for a converter. By setting a zero-voltage switching winding and voltage clamping, the voltage across the main switching transistor is reduced to zero before the main switching transistor is turned on, which can more ideally achieve zero-voltage switching. This not only avoids hard switching during transients but also eliminates the need to adjust the appropriate reverse excitation current, greatly improving the efficiency and reliability of the system.

[0005] To achieve the above objectives, the main technical solutions adopted in this application include:

[0006] In a first aspect, embodiments of this application provide a zero-voltage switching control circuit for a converter. The converter includes a transformer and a main switching transistor, the main switching transistor being configured corresponding to the primary winding of the transformer. The zero-voltage switching control circuit includes: a zero-voltage switching winding; and a clamping control unit connected to the zero-voltage switching winding. The clamping control unit includes a clamping switching transistor, and is configured to control the clamping switching transistor to turn on before the main switching transistor is turned on, so as to clamp the voltage of the zero-voltage switching winding. The voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, so that the voltage across the main switching transistor is reduced to zero before the main switching transistor is turned on.

[0007] According to the zero-voltage switching control circuit of the converter provided in the embodiments of this application, by setting a zero-voltage switching winding on the primary side of the transformer, the clamping control unit controls the clamping switching transistor to turn on before the main switching transistor is turned on, so as to clamp the voltage of the zero-voltage switching winding. The voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, thereby reducing the voltage across the main switching transistor to zero before the main switching transistor is turned on. This can achieve zero-voltage switching more ideally, not only avoiding hard switching during transients, but also eliminating the need to adjust the appropriate reverse excitation current, greatly improving the efficiency and reliability of the system.

[0008] Optionally, in some embodiments of this application, the clamping control unit further includes a clamping capacitor, which is adapted to clamp the voltage of the zero-voltage switching winding when the clamping switch is turned on.

[0009] Optionally, in some embodiments of this application, the drain of the clamping switch is connected to the opposite terminal of the zero-voltage switching winding through the clamping capacitor, and the source of the clamping switch is connected to the same terminal of the zero-voltage switching winding and then grounded.

[0010] Optionally, in some other embodiments of this application, the source of the clamping switch is connected to the same-name terminal of the zero-voltage switching winding through the clamping capacitor, and the drain of the clamping switch is connected to the opposite-name terminal of the zero-voltage switching winding and then grounded.

[0011] Optionally, in some embodiments of this application, when the converter is an asymmetric half-bridge converter, the converter further includes a second switching transistor and a first capacitor, the second switching transistor and the main switching transistor forming a half-bridge, and the first capacitor being connected to the opposite end of the primary winding.

[0012] Specifically, the source of the main switching transistor is grounded, the drain of the main switching transistor is connected to the source of the second switching transistor, and is connected to the opposite terminal of the primary winding through the first capacitor. The drain of the second switching transistor is connected to the same terminal of the primary winding through the first inductor, and is suitable for receiving an input voltage.

[0013] Alternatively, in some other embodiments of this application, the source of the main switch is connected to the drain of the second switch and connected to the same-name terminal of the primary winding through a first inductor, the source of the second switch is connected to the opposite-name terminal of the primary winding through the first capacitor, the source of the second switch is grounded, and the drain of the main switch is adapted to be connected to the input voltage.

[0014] Optionally, in some embodiments of this application, the zero-voltage switch control circuit described above further includes: an auxiliary power supply unit connected to both ends of the clamping switch tube, the auxiliary power supply unit being configured to output a power supply voltage based on the voltage of the zero-voltage switch winding.

[0015] The auxiliary power supply unit includes: a rectifier diode, the anode of which is connected to the first terminal of the clamping switch; and a voltage regulator capacitor, one end of which is connected to the cathode of the rectifier diode, and the other end of which is connected to the second terminal of the clamping switch.

[0016] Optionally, in some embodiments of this application, the clamping control unit is further configured to control the clamping switch to turn off after the main switch is turned on.

[0017] Specifically, the clamping control unit further includes a controller configured to start timing when an on control signal is output to the main switch transistor, and to output an off control signal to the clamping switch transistor when the timing reaches a preset time.

[0018] Secondly, embodiments of this application also provide a converter, including: a transformer and a main switching transistor, the main switching transistor being configured to correspond to the primary winding of the transformer; and a zero-voltage switching control circuit described in the above embodiments, the zero-voltage switching control circuit being configured to control the main switching transistor to turn on when the voltage across the main switching transistor drops to zero.

[0019] According to the converter provided in the embodiments of this application, based on the above-described zero-voltage switching control circuit, zero-voltage switching can be achieved more ideally. This not only avoids hard switching during transients but also eliminates the need to adjust the appropriate reverse excitation current, greatly improving the efficiency and reliability of the system.

[0020] Thirdly, this application also provides a zero-voltage switching control method for a converter. The converter includes a transformer, a main switch, and a clamping switch. The main switch is configured to correspond to the primary winding of the transformer, and the clamping switch is configured to correspond to the zero-voltage switching winding of the transformer. The method includes: before the main switch is turned on, controlling the clamping switch to turn on to clamp the voltage of the zero-voltage switching winding. The voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, so that the voltage across the main switch is reduced to zero before the main switch is turned on.

[0021] According to the zero-voltage switching control method of the converter in this application embodiment, before the main switch is turned on, the voltage of the zero-voltage switching winding is clamped by controlling the clamping switch to be turned on. In this way, the voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, so that the voltage across the main switch is reduced to zero before the main switch is turned on. This can achieve zero-voltage switching more ideally, which can not only avoid hard switching during transients, but also eliminate the need to adjust the appropriate reverse excitation current, greatly improving the efficiency and reliability of the system.

[0022] Optionally, in some embodiments of this application, the above-described zero-voltage switch control method further includes: controlling the clamping switch to turn off after the main switch is turned on.

[0023] The step of controlling the clamping switch to turn off after the main switch is turned on includes: starting a timer when an on control signal is output to the main switch, and outputting a turn-off control signal to the clamping switch when the timer reaches a preset time. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a circuit diagram of an asymmetric half-bridge flyback converter in related technologies.

[0026] Figure 2 This is a circuit diagram of another asymmetric half-bridge flyback converter in related technologies;

[0027] Figure 3 This is a schematic diagram of the timing waveform of an asymmetric half-bridge flyback converter operating in critical mode in a related technology.

[0028] Figure 4 A schematic diagram of a zero-voltage switching control circuit for a converter provided in one embodiment of this application;

[0029] Figure 5 This is a schematic diagram of the timing waveform of a converter during operation according to an embodiment of this application;

[0030] Figure 6 A schematic diagram of a zero-voltage switching control circuit for a converter provided in another embodiment of this application;

[0031] Figure 7 A circuit diagram illustrating the application of a zero-voltage switching control circuit to an AHB converter according to an embodiment of this application;

[0032] Figure 8 A circuit diagram illustrating the application of a zero-voltage switching control circuit to an AHB converter, as provided in another embodiment of this application;

[0033] Figure 9 This is a schematic diagram of the timing waveforms of an AHB converter during operation according to an embodiment of this application;

[0034] Figure 10 A circuit diagram illustrating the auxiliary power supply application of the zero-voltage switching control circuit of an AHB converter provided in one embodiment of this application;

[0035] Figure 11 This is a circuit diagram of a converter provided in one embodiment of this application;

[0036] Figure 12 This is a flowchart illustrating a zero-voltage switching control method for a converter provided in one embodiment of this application. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] In related technologies, the circuit topology of the AHB flyback converter generally has two implementation methods, which can be found in the following documents: Figure 1 and Figure 2 As shown. Among them, Figure 1 In the middle, the upper bridge switch Q1' is the first switch and the lower bridge switch Q2' is the second switch; Figure 2In this circuit, the upper bridge switch Q2' is the second switch, and the lower bridge switch Q1' is the first switch. The two circuit topologies operate on essentially the same principle, differing only in the connection method of the primary winding.

[0039] Specifically, with Figure 1 For example, the waveform of this AHB flyback converter operating in critical mode is as follows: Figure 3 As shown, Vg1' and Vg2' are the drive voltage signal waveforms of the first switch Q1' and the second switch Q2', respectively; Lm Vaux is the excitation current waveform on the primary winding Np'; Vs is the voltage waveform across the auxiliary winding Na', obtained by the voltage divider Vs across sampling resistors R1 and R2; Vs DS_Q1’ This is the voltage waveform across the first switching transistor Q1'. To prevent shoot-through between the first switching transistor Q1' and the second switching transistor Q2', a certain dead time, such as td1 and td2, needs to be included in the drive voltage signals provided to the first and second switching transistors Q1' and Q2'. Figure 3 As shown, the asymmetric half-bridge flyback converter, in principle, controls the second switch Q2' to be turned on for an additional period of time, for example, t. ZVS This generates a reverse excitation current, causing the voltage across the first switch Q1' to drop to zero, and then controls the first switch Q1' to turn on, thereby achieving zero-voltage turn-on of the first switch Q1'.

[0040] However, the performance of the AHB flyback converter in the related technology is not optimized enough when achieving zero-voltage turn-on of the first switch Q1'. There are problems such as the primary-side switch not achieving complete ZVS or the reverse excitation current being larger, resulting in energy cycling, which affects the converter efficiency.

[0041] Therefore, the converter and its zero-voltage switching control circuit and method provided in this application embodiment, by setting a zero-voltage switching winding on the primary side of the transformer, controls the clamping switch to turn on before the main switch is turned on, so as to clamp the voltage of the zero-voltage switching winding. The voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, thereby reducing the voltage across the main switch to zero before the main switch is turned on. This can more ideally realize zero-voltage switching, not only avoiding hard switching during transients, but also eliminating the need to adjust the appropriate reverse excitation current, greatly improving the efficiency and reliability of the system.

[0042] The zero-voltage switching control circuit of the converter, the converter having the zero-voltage switching control circuit, and the zero-voltage switching control method of the converter provided in this application will now be described in detail with reference to the accompanying drawings.

[0043] refer to Figure 4The diagram shown is a schematic of a zero-voltage switching control circuit for a converter according to an embodiment of this application. Figure 4 As shown, the converter includes a transformer Tr and a main switch Q1. The main switch Q1 is configured to correspond to the primary winding Np of the transformer Tr. The zero-voltage switching control circuit includes a zero-voltage switching winding N. zvs And clamp control unit 10.

[0044] In the embodiments of this application, the input voltage Vin on the primary side is coupled to the secondary side for output by controlling the turn-on and turn-off of the main switch Q1. The relationship between the input voltage Vin and the output voltage Vo is determined based on the turns ratio between the primary winding Np and the secondary winding Ns.

[0045] like Figure 4 As shown, the clamping control unit 10 and the zero-voltage switching winding N zvs Connected, the clamp control unit 10 includes a clamp switch transistor Q. zvs The clamping control unit 10 is configured to control the clamping switch Q before the main switch Q1 is turned on. zvs Turn on, to the zero-voltage switching winding N zvs voltage V zvs Clamping is performed, wherein the zero-voltage switching winding N zvs The clamped voltage is coupled to the primary winding Np through the transformer Tr, causing the voltage V across the main switch Q1 to... DS_Q1 The value is reduced to zero before the main switch Q1 is turned on.

[0046] Optionally, in one embodiment of this application, such as Figure 4 As shown, the clamping control unit 10 also includes a clamping capacitor C. zvs Clamping capacitor C zvs Suitable for clamping switching transistor Q zvs When the circuit is open, for the zero-voltage switching winding N zvs voltage V zvs Perform clamping.

[0047] In other words, in this application, an auxiliary winding, namely a zero-voltage switching winding N, is provided on the primary side of the transformer Tr. zvs And zero-voltage switching winding N zvs A series clamping capacitor C is connected in parallel across its two ends. zvs and clamping switch Q zvs In this way, before the main switch Q1 is turned on, the clamping switch Q is controlled first. zvs When switched on, the zero-voltage switching winding N... zvs The voltage on is clamped by capacitor C zvs Voltage clamping on, at this time zero voltage switching winding N zvs voltage V zvs=Vin*Nzvs / Np, and then coupled through the windings of transformer Tr, at this time the voltage across the primary winding is equal to Vin, making the voltage across the main switch Q1 V DS_Q1 The transistor is pre-discharged to zero volts, and then the main switch Q1 is turned on, achieving zero-voltage turn-on of the main switch Q1. For details, please refer to [reference needed]. Figure 5 As shown.

[0048] Furthermore, such as Figure 5 As shown, during the current switching cycle of the converter, at time t3, the control clamping switch Q is activated. zvs Turn on, zero-voltage switching winding N zvs Voltage V on zvs Clamping capacitor C zvs Voltage clamping on, V zvs =Vin*Nzvs / Np, and then coupled to the primary winding through transformer Tr, so that the voltage across the primary winding is equal to Vin, making the voltage V across the main switch Q1 equal to Vin. DS_Q1 The circuit is prematurely discharged to zero; at time t4, the main control switch Q1 is turned on, the input voltage Vin charges the primary magnetizing inductor, and the magnetizing current I_Lm on the primary winding Np begins to rise, while the clamping switch Q1 is held in place. zvs Turn-on; at time t5, after the main switch Q1 is turned on, the clamping switch Q is controlled. zvs During the t0-t1 time period, the main switch Q1 remains on, and the magnetizing current I_Lm on the primary winding Np continues to rise. At time t1, the main switch Q1 is turned off until time t3, at which point the next switching cycle begins. This process repeats to transfer the input voltage Vin from the primary side of the transformer Tr to the secondary side.

[0049] Optionally, in some embodiments of this application, such as Figure 4 As shown, clamping switch Q zvs The drain is clamped by capacitor C. zvs Connected to zero-voltage switching winding N zvs The opposite terminal, clamping switch Q zvs The source and zero-voltage switching winding N zvs After connecting the terminals with the same name, ground them.

[0050] This is based on the zero-voltage switching winding N zvs The connection method between the corresponding terminal of the primary winding and the corresponding terminal of the primary winding Np enables the coupling and transmission of clamping voltage, so that the voltage V across the main switch Q1 is... DS_Q1 Being discharged to zero volts in advance allows for a more ideal zero-voltage switching.

[0051] Alternatively, in some other embodiments of this application, such as Figure 6 As shown, clamping switch Qzvs The source is clamped by capacitor C. zvs Connected to zero-voltage switching winding N zvs The same terminal, clamping switch Q zvs The drain and zero-voltage switching winding N zvs After connecting the different-named terminals, ground them.

[0052] This is achieved by changing the zero-voltage switching winding N. zvs The same terminal and clamping switch Q zvs The connection method between the source and drain can also achieve the coupling and transmission of clamping voltage, so that the voltage V across the main switch Q1 is... DS_Q1 Being discharged to zero volts in advance allows for a more ideal zero-voltage switching.

[0053] Optionally, in some embodiments of this application, such as Figure 7 or Figure 8 As shown, when the converter is an asymmetric half-bridge converter, the converter also includes a second switch Q2 and a first capacitor C1. The second switch Q2 and the main switch Q1 form a half-bridge, and the first capacitor C1 is connected to the opposite terminal of the primary winding Np.

[0054] Among them, such as Figure 7 As shown, the source of the main switch Q1 is grounded, the drain of the main switch Q1 is connected to the source of the second switch Q2, and is connected to the opposite terminal of the primary winding Np through the first capacitor C1. The drain of the second switch Q2 is connected to the same terminal of the primary winding Np through the first inductor L1, and is suitable for connecting the input voltage Vin.

[0055] Or, such as Figure 8 As shown, the source of the main switch Q1 is connected to the drain of the second switch Q2, and is connected to the same-name terminal of the primary winding Np through the first inductor L1. The source of the second switch Q2 is connected to the opposite-name terminal of the primary winding Np through the first capacitor C1. The source of the second switch Q2 is grounded, and the drain of the main switch Q1 is suitable for connecting the input voltage Vin.

[0056] In the embodiments of this application, regardless of the connection method between the half-bridge switch and the primary winding of the asymmetrical half-bridge converter, an auxiliary winding, namely a zero-voltage switching winding N, is provided on the primary side of the transformer Tr. zvs And zero-voltage switching winding N zvs A series clamping capacitor C is connected in parallel across its two ends. zvs and clamping switch Q zvs In this way, before the main switch Q1 is turned on, the clamping switch Q is controlled first. zvs When switched on, the zero-voltage switching winding N... zvs The voltage on is clamped by capacitor C zvsVoltage clamping on, at this time zero voltage switching winding N zvs voltage V zvs = (Vin-Vc1)*Nzvs / Np, and then coupled through the windings of transformer Tr, the voltage across the primary winding is equal to (Vin-Vc1), making the voltage V across the main switch Q1 equal to (Vin-Vc1). DS_Q1 The transistor is pre-discharged to zero volts, and then the main switch Q1 is turned on, achieving zero-voltage turn-on of the main switch Q1. For details, please refer to [reference needed]. Figure 9 As shown.

[0057] Furthermore, such as Figure 9 As shown, during the current switching cycle of the asymmetric half-bridge converter, at time t3, the control clamping switch Q is... zvs Turn on, zero-voltage switching winding N zvs Voltage V on zvs Clamping capacitor C zvs Voltage clamping on, V zvs = (Vin-Vc1)*Nzvs / Np, and then coupled to the primary winding through transformer Tr, so that the voltage across the primary winding is equal to (Vin-Vc1), making the voltage V across the main switch Q1 equal to (Vin-Vc1). DS_Q1 The circuit is prematurely discharged to zero; at time t4, the main control switch Q1 is turned on and the second switch Q2 is turned off. The input voltage Vin charges the magnetizing inductor on the primary side, and the magnetizing current I_Lm on the primary winding Np begins to rise. At the same time, the clamping switch Q is maintained. zvs Turn-on; at time t5, after the main switch Q1 is turned on, the clamping switch Q is controlled. zvs During the t0-t1 time period, the main switch Q1 remains on, and the magnetizing current I_Lm on the primary winding Np continues to rise. At t1, the main switch Q1 is turned off and the second switch Q2 is turned on, remaining on until t2. Then, the second switch Q2 is turned off again, continuing until t3, at which point the next switching cycle begins. This process repeats, transferring the input voltage Vin from the primary side of the transformer Tr to the secondary side.

[0058] The zero-voltage switching control circuit of the converter described in this application, by setting a zero-voltage switching winding on the primary side of the transformer and combining it with voltage clamping, clamps the voltage of the zero-voltage switching winding by controlling the clamping switch to turn on before the main switch is turned on. In this way, the voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, so that the voltage across the main switch is reduced to zero before the main switch is turned on. This can achieve zero-voltage switching more ideally, not only avoiding hard switching during transients, but also eliminating the need to adjust the appropriate reverse excitation current, greatly improving the efficiency and reliability of the system.

[0059] Optionally, in some embodiments of this application, such as Figure 10 As shown, the zero-voltage switching control circuit described above also includes an auxiliary power supply unit 20, which is connected to the clamping switch transistor Q. zvs The two ends of the auxiliary power supply unit 20 are configured to output the supply voltage Vcc based on the voltage of the zero-voltage switching winding.

[0060] Specifically, such as Figure 10 As shown, the auxiliary power supply unit includes a rectifier diode Dvcc and a voltage regulator capacitor Cvcc. The anode of the rectifier diode Dvcc is connected to the clamping switch Q. zvs The first terminal is connected, one end of the Zener capacitor Cvcc is connected to the cathode of the rectifier diode Dvcc, and the other end of the Zener capacitor Cvcc is connected to the clamping switch Q. zvs The second end is connected.

[0061] In the embodiments of this application, the zero-voltage switching control circuit of the AHB converter can also be used to optimize the power supply of the auxiliary winding, that is, in Figure 7 or Figure 8 Based on this, add a rectifier diode Dvcc and a capacitor Cvcc, combined with Figure 9 From the voltage waveform of Vzvs, we can obtain the rectified supply voltage Vcc = Vo*Nzvs / Ns + (Vin - Vc1)*Nzvs / Np. According to the relationship between the output voltage Vo and Vc1 of the AHB converter: Vo*Np / Ns = Vc1, we can obtain the supply voltage Vcc = Vin*Nzvs / Np. It is evident that the supply voltage Vcc of this auxiliary power supply unit is proportional to the input voltage Vin. Since the input voltage Vin has a relatively narrow range in AHB converter applications, the supply voltage Vcc is relatively stable, which simplifies the power supply line design of the entire power system. Therefore, it eliminates the need for additional LDO or Boost voltage to stably output Vcc, reducing costs, significantly saving power consumption, and facilitating the miniaturization design of the converter.

[0062] Optionally, in some embodiments of this application, such as Figure 5 or Figure 9 As shown, the clamping control unit 10 is also configured to control the clamping switch Q after the main switch Q1 is turned on. zvs Turn off.

[0063] Furthermore, the clamping control unit 10 also includes a controller (not shown in the figure), such as a primary-side controller. The controller is configured to start timing when an on-control signal is output to the main switch Q1, and to output an off-control signal to the clamping switch Q1 when the timing reaches a preset time. zvs Control clamping switch Q zvs Turn off.

[0064] In this embodiment, the clamping switch Q is controlled by turning on the main switch Q1 for a certain period of time. zvs Turning off ensures that the main switch Q1 remains at zero voltage throughout the entire turn-on process, effectively preventing hard switching during transients.

[0065] like Figure 11 As shown in the figure, this application embodiment also provides a converter 100, which includes: a transformer Tr, a main switch Q1, and a zero-voltage switching control circuit 200 described in the above embodiment. The main switch Q1 is set to the primary winding Np of the transformer Tr, and the zero-voltage switching control circuit 200 is configured to control the main switch Q1 to turn on when the voltage across the main switch Q1 drops to zero.

[0066] Specifically, the clamping control unit 10 can control the clamping switch Q before the main switch Q1 is turned on. zvs Turn on, to the zero-voltage switching winding N zvs voltage V zvs Clamping is performed so that the zero-voltage switching winding N zvs The clamped voltage is coupled to the primary winding Np through the transformer Tr, causing the voltage V across the main switch Q1 to... DS_Q1 The value is reduced to zero before the main switch Q1 is turned on.

[0067] According to the converter 100 provided in the embodiments of this application, based on the zero-voltage switching control circuit 200 described above, zero-voltage switching can be achieved more ideally. This not only avoids hard switching during transients, but also eliminates the need to adjust the appropriate reverse excitation current, greatly improving the efficiency and reliability of the system.

[0068] It is understood that the embodiments of this application are mainly described and illustrated using an asymmetric half-bridge converter as an example, but are not limited to this converter structure. Other similar converters, such as general flyback converters or active clamp flyback converters, can also be used. Applying the control scheme of this application to similar converter structures can also achieve the same or similar beneficial technical effects. The embodiments of this application do not limit this.

[0069] In addition, such as Figure 12 As shown in the figure, this application embodiment also provides a zero-voltage switching control method for a converter. The converter may include a transformer, a main switch transistor, and a clamping switch transistor. The main switch transistor is configured to correspond to the primary winding of the transformer, and the clamping switch transistor is configured to correspond to the zero-voltage switching winding of the transformer. The zero-voltage switching control method includes the following steps:

[0070] S1, before the main switch is turned on, the clamping switch is turned on to clamp the voltage of the zero-voltage switching winding. The voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, so that the voltage across the main switch is reduced to zero before the main switch is turned on.

[0071] S2 controls the clamping switch to turn off after the main switch is turned on.

[0072] Optionally, in some embodiments of this application, controlling the clamping switch to turn off after the main switch is turned on includes: starting a timer when outputting an on control signal to the main switch, and outputting a turn-off control signal to the clamping switch when the timer reaches a preset time.

[0073] In other words, by controlling the main switch to be turned on for a certain period of time and then controlling the clamping switch to be turned off, this application can ensure that the main switch is always in a zero-voltage state throughout the entire turn-on process, effectively avoiding hard switching during transients.

[0074] According to the zero-voltage switching control method of the converter in this application embodiment, before the main switch is turned on, the voltage of the zero-voltage switching winding is clamped by controlling the clamping switch to be turned on. In this way, the voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, so that the voltage across the main switch is reduced to zero before the main switch is turned on. This can achieve zero-voltage switching more ideally, which can not only avoid hard switching during transients, but also eliminate the need to adjust the appropriate reverse excitation current, greatly improving the efficiency and reliability of the system.

[0075] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0076] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A zero-voltage switching control circuit for a converter, characterized in that, The converter includes a transformer and a main switching transistor, the main switching transistor being configured corresponding to the primary winding of the transformer, and the zero-voltage switching control circuit including: Zero-voltage switching winding; A clamping control unit is connected to the zero-voltage switching winding. The clamping control unit includes a clamping switch transistor. The clamping control unit is configured to control the clamping switch transistor to turn on before the main switch transistor is turned on, so as to clamp the voltage of the zero-voltage switching winding. The voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, so that the voltage across the main switch transistor is reduced to zero before the main switch transistor is turned on.

2. The zero-voltage switching control circuit according to claim 1, characterized in that, The clamping control unit further includes a clamping capacitor, which is adapted to clamp the voltage of the zero-voltage switching winding when the clamping switch is turned on.

3. The zero-voltage switching control circuit according to claim 2, characterized in that, The drain of the clamping switch is connected to the opposite terminal of the zero-voltage switch winding through the clamping capacitor, and the source of the clamping switch is connected to the same terminal of the zero-voltage switch winding and then grounded.

4. The zero-voltage switching control circuit according to claim 2, characterized in that, The source of the clamping switch is connected to the same-name terminal of the zero-voltage switch winding through the clamping capacitor, and the drain of the clamping switch is connected to the opposite-name terminal of the zero-voltage switch winding and then grounded.

5. The zero-voltage switching control circuit according to any one of claims 1-4, characterized in that, In the case where the converter is an asymmetric half-bridge converter, the converter further includes a second switching transistor and a first capacitor. The second switching transistor and the main switching transistor form a half-bridge, and the first capacitor is connected to the opposite terminal of the primary winding.

6. The zero-voltage switching control circuit according to claim 5, characterized in that, The source of the main switching transistor is grounded, the drain of the main switching transistor is connected to the source of the second switching transistor, and is connected to the opposite terminal of the primary winding through the first capacitor. The drain of the second switching transistor is connected to the same terminal of the primary winding through the first inductor, and is suitable for receiving an input voltage.

7. The zero-voltage switching control circuit according to claim 5, characterized in that, The source of the main switch is connected to the drain of the second switch and is connected to the same-name terminal of the primary winding through the first inductor. The source of the second switch is connected to the opposite-name terminal of the primary winding through the first capacitor. The source of the second switch is grounded. The drain of the main switch is suitable for receiving an input voltage.

8. The zero-voltage switching control circuit according to claim 1, characterized in that, Also includes: An auxiliary power supply unit is connected to both ends of the clamping switch tube and is configured to output a power supply voltage based on the voltage of the zero-voltage switching winding.

9. The zero-voltage switching control circuit according to claim 8, characterized in that, The auxiliary power supply unit includes: A rectifier diode, wherein the anode of the rectifier diode is connected to the first terminal of the clamping switch transistor; A voltage-regulating capacitor, one end of which is connected to the cathode of the rectifier diode, and the other end of which is connected to the second terminal of the clamping switch.

10. The zero-voltage switching control circuit according to any one of claims 1-4, characterized in that, The clamping control unit is also configured to control the clamping switch to turn off after the main switch is turned on.

11. The zero-voltage switching control circuit according to claim 10, characterized in that, The clamping control unit further includes a controller configured to start timing when an on control signal is output to the main switch transistor, and to output an off control signal to the clamping switch transistor when the timing reaches a preset time.

12. A converter, characterized in that, include: A transformer and a main switch, wherein the main switch is configured corresponding to the primary winding of the transformer; According to any one of claims 1-11, the zero-voltage switching control circuit is configured to control the main switching transistor to turn on when the voltage across the main switching transistor drops to zero.

13. A zero-voltage switching control method for a converter, characterized in that, The converter includes a transformer, a main switch, and a clamping switch. The main switch is configured corresponding to the primary winding of the transformer, and the clamping switch is configured corresponding to the zero-voltage switching winding of the transformer. The method includes: Before the main switch is turned on, the clamping switch is turned on to clamp the voltage of the zero-voltage switching winding. The voltage of the zero-voltage switching winding after being clamped is coupled to the primary winding through the transformer, so that the voltage across the main switch is reduced to zero before the main switch is turned on.

14. The zero-voltage switching control method according to claim 13, characterized in that, Also includes: After the main switch is turned on, the clamping switch is turned off.

15. The zero-voltage switching control method according to claim 14, characterized in that, Controlling the clamping switch to turn off after the main switch is turned on includes: When the turn-on control signal is output to the main switch, a timer is started, and when the timer reaches a preset time, a turn-off control signal is output to the clamping switch.

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