An active-clamp absorption circuit and switching power converter

Abstract

The application discloses an active clamping absorption circuit and a switching power supply converter, and the absorption circuit is applied to a secondary side rectifier circuit of the switching power supply converter which transmits energy in positive and negative half periods; the active clamping absorption circuit comprises a suppression circuit, a first rectifier circuit, a second rectifier circuit and a discharge circuit; compared with a conventional active clamping absorption circuit, the active clamping absorption circuit has the rectifier circuits and shares the suppression circuit and the discharge circuit, the design difficulty of a plurality of discharge circuit control circuits is reduced, the flexibility of the layout of the active clamping absorption circuit is improved, the clamping absorption of power tube stress can be more effectively performed, the voltage clamping of the power tube of the secondary side active clamping circuit of the switching power supply is effectively realized, and the reliability of the circuit is improved.

Description

Technical Field

[0001] This invention relates to the field of switching power supplies, and particularly to an active clamping snubber circuit and a switching power converter used on the secondary side of a switching power supply. Background Technology

[0002] In all secondary-side rectifier circuits of switching power supply converters, whether diode rectification or synchronous rectification, there is a common problem: resonance occurs during secondary-side rectification due to the leakage inductance of the transformer and the parasitic junction capacitance of the rectifier switch. This resonance occurs when the rectifier switch is turned off, and neither the leakage inductance nor the junction capacitance can be eliminated. When the leakage inductance is large, the peak generated during resonance is even larger. Especially in high-power, high-power-density switching power supplies, secondary-side rectifier circuits of switching power supply converters that transfer energy during both the positive and negative half-cycles of the transformer are often used (such as the bridge rectifier circuit shown in the left figure of Figure 1 and the full-wave rectifier circuit shown in the left figure of Figure 2). Due to the high output power, the resonance peaks caused by the parasitic parameters of the wiring are huge, posing a significant challenge to the stress on the rectifier switch. Therefore, how to eliminate resonance peaks becomes a critical issue.

[0003] In existing technologies, both bridge rectifier circuits and full-wave rectifier circuits have corresponding active clamping absorption circuits. The active clamping circuit for a bridge rectifier circuit (as shown in Figure 1, right) simply adds a clamping capacitor and a switching transistor (or a switching transistor connected in parallel with a diode). Specifically, the clamping capacitor C301, the switching transistor TR301, and the diode D301 in the secondary clamping circuit are all relatively simple. However, the clamping capacitor C301 has only one path, resulting in a relatively large absorption loop with any rectifier transistor on the secondary side of the bridge rectifier circuit, leading to poor absorption. The active clamping circuit for a full-wave rectifier circuit (as shown in Figure 2, right) adds a clamping capacitor and a switching transistor (or a switching transistor connected in parallel with a diode) to each rectifier transistor. Compared to the suppression circuit in Figure 1, the design in Figure 2 effectively reduces the absorption loop, at the cost of adding one more switching transistor and increasing the complexity of the control circuits corresponding to the two interleaved switching transistors. To address the aforementioned issues, a novel active clamping absorption circuit needs to be designed, which can improve layout flexibility, reduce the routing path of the absorption loop, reduce the discharge circuit, simplify the control circuit, and optimize the circuit size of the control circuit. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to propose an active clamping absorption circuit and a secondary rectifier circuit of a switching power converter that transmits energy in both the positive and negative half-cycles of the transformer. By freely combining the suppression circuit, rectifier circuit and discharge circuit, the layout flexibility is improved, the wiring path of the absorption circuit is reduced, the discharge circuit is reduced, the control circuit is simplified, and the circuit volume of the control circuit is optimized.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0006] In a first aspect, an active clamping circuit is provided for use in the secondary rectifier circuit of a switching power supply converter that transfers energy during both the positive and negative half-cycles of the transformer. The converter includes, in sequence, an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201. The secondary rectifier circuit is a bridge rectifier circuit with four connection points: V1, V2, V3, and V4. Connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The active clamping absorption circuit includes a suppression circuit, a first rectifier circuit, a second rectifier circuit, and a discharge circuit. The second terminal of the suppression circuit, the second terminal of the first rectifier circuit, and the second terminal of the first rectifier circuit are connected. The second end of the rectifier circuit and the second end of the discharge circuit are connected together to form connection point V0; the first end of the first rectifier circuit and the first end of the second rectifier circuit are connected to connection points V2 and V3 respectively; the first end of the discharge circuit is connected to connection point V1, and the first end of the suppression circuit is connected to connection point V4, or the first end of the discharge circuit is connected to connection point V4, and the first end of the suppression circuit is connected to connection point V1; the starting edge of the drive signal of the discharge circuit lags behind the rising edge of the signal at connection point V1, and there is a dead time dt1 > 0; the ending edge of the drive signal of the discharge circuit leads the falling edge of the signal at connection point V1, and there is a dead time dt2 > 0.

[0007] Preferably, the first rectifier circuit includes diode D311, and the second rectifier circuit includes diode D321; when the first terminal of the discharge circuit is connected to connection point V1, and the first terminal of the suppression circuit is connected to connection point V4, the cathodes of diodes D311 and D321 both serve as the second terminal of the corresponding rectifier circuit, and the anodes both serve as the first terminal of the corresponding rectifier circuit; when the first terminal of the discharge circuit is connected to connection point V4, and the first terminal of the suppression circuit is connected to connection point V1, the cathodes of diodes D311 and D321 both serve as the first terminal of the corresponding rectifier circuit, and the anodes both serve as the second terminal of the corresponding rectifier circuit.

[0008] Preferably, the suppression circuit includes capacitors C311 and C321 connected in parallel.

[0009] Preferably, the discharge circuit includes a switching transistor TR301. When the first end of the discharge circuit is connected to the connection point V1, the switching transistor TR301 is an N-type MOS transistor, with the first end being the source and the second end being the drain. When the first end of the discharge circuit is connected to the connection point V4, the switching transistor TR301 is a P-type MOS transistor, with the second end being the drain and the first end being the source.

[0010] Preferably, the discharge circuit further includes a diode D301. When the switching transistor TR301 is an N-type MOSFET, the anode of the diode D301 is connected to the source of the switching transistor TR301, and the cathode is connected to the drain of the switching transistor TR301. When the switching transistor TR301 is a P-type MOSFET, the anode of the diode D301 is connected to the drain of the switching transistor TR301, and the cathode is connected to the source of the switching transistor TR301.

[0011] Secondly, an active clamping absorption circuit is provided, applied to the secondary rectifier circuit of a switching power supply converter that transfers energy during both the positive and negative half-cycles of the transformer. The converter includes, in sequence, an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201. The secondary rectifier circuit is a full-wave rectifier circuit, and four connection points are provided between the secondary rectifier circuit and the secondary winding of the transformer, namely V1, V2, V3, and V4. Connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The active clamping absorption circuit includes a suppression circuit, a first rectifier circuit, and a second rectifier circuit. The discharge circuit consists of a discharge circuit, a suppression circuit, a first rectifier circuit, a second rectifier circuit, and a discharge circuit. The second terminals of these circuits are connected to form a connection point V0. The first terminals of the first and second rectifier circuits are connected to connection points V2 and V3, respectively. The first terminal of the discharge circuit is connected to connection point V1, and the first terminal of the suppression circuit is connected to connection point V4. The starting edge of the drive signal for the discharge circuit lags behind the rising edge of the signal at connection point V1, resulting in a dead time dt1 > 0. The ending edge of the drive signal for the discharge circuit leads the falling edge of the signal at connection point V1, resulting in a dead time dt2 > 0.

[0012] Thirdly, an active clamping absorption circuit is provided, applied to the secondary rectifier circuit of a switching power supply converter that transfers energy during both the positive and negative half-cycles of the transformer. The converter includes an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201 connected in sequence. The secondary rectifier circuit is a full-wave rectifier circuit, and there are four connection points between the secondary rectifier circuit and the secondary winding of the transformer, namely V1, V2, V3, and V4. Connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The active clamping absorption circuit includes a suppression circuit, a first rectifier circuit, and a second rectifier circuit. The circuit consists of a discharge circuit and a first rectifier circuit. The second terminals of the first and second rectifier circuits are connected to connection points V2 and V3, respectively. The second terminal of the suppression circuit is connected to the second terminal of the discharge circuit to form connection point V0. The first terminals of the first, second, and suppression circuits are all connected to connection point V1, and the first terminal of the discharge circuit is connected to connection point V4. The starting edge of the drive signal of the discharge circuit lags behind the rising edge of the signal at connection point V1, resulting in a dead time dt1 > 0. The ending edge of the drive signal of the discharge circuit leads the falling edge of the signal at connection point V1, resulting in a dead time dt2 > 0.

[0013] Preferably, the secondary winding of the transformer includes a first winding and a second winding; the secondary rectifier circuit includes a switching transistor TR201 and a switching transistor TR202; the same-name terminal of the first winding is connected to the opposite-name terminal of the second winding as connection point V1, the opposite-name terminal of the first winding is connected to the drain of the switching transistor TR201 as connection point V2, the same-name terminal of the second winding is connected to the drain of the switching transistor TR202 as connection point V3, and the source of the switching transistor TR201 and the source of the switching transistor TR202 are connected as connection point V4.

[0014] Preferably, the active clamping absorption circuit further includes a third rectifier circuit and a fourth rectifier circuit; the second end of the third rectifier circuit and the second end of the fourth rectifier circuit are connected to connection point V0, and the first end of the third rectifier circuit and the first end of the fourth rectifier circuit are connected to connection point V2 and connection point V3, respectively.

[0015] Fourthly, a switching power converter is provided, comprising an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201 connected in sequence. The secondary rectifier circuit and the secondary winding of the transformer have four connection points, namely V1, V2, V3, and V4, wherein connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded; it also includes an active clamping absorption circuit as described above, the active clamping absorption circuit being connected to the secondary rectifier circuit.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. Compared with conventional active clamp absorption circuits, this invention adds a rectifier circuit and shares the suppression circuit and discharge circuit, which reduces the design difficulty of the multi-channel discharge circuit control circuit, improves the layout flexibility of the active clamp absorption circuit, can more effectively clamp and absorb the stress of the power transistor, effectively realize the voltage clamping of the power transistor in the secondary active clamp circuit of the switching power supply, and improves the reliability of the circuit.

[0018] 2. This invention improves layout flexibility and reduces the routing path of the absorption circuit by freely combining the suppression circuit, rectifier circuit, and discharge circuit, thereby effectively suppressing the peak stress caused by leakage inductance of the secondary rectifier switch and improving product reliability.

[0019] 3. This invention reduces the application of discharge circuits by freely combining suppression circuits, rectifier circuits, and discharge circuits, simplifies the control circuit of active clamping circuits, optimizes the circuit size of control circuits, and optimizes the topology design of high-power power supplies. Attached Figure Description

[0020] Figure 1a This is a schematic diagram of a conventional full-bridge rectifier topology;

[0021] Figure 1b This is a schematic diagram of a conventional active clamping snubber circuit for a bridge rectifier circuit.

[0022] Figure 2a This is a schematic diagram of a conventional full-bridge full-wave rectifier topology;

[0023] Figure 2b This is a schematic diagram of the application of a conventional active clamping absorption circuit in a full-wave rectifier circuit.

[0024] Figure 3 This is a schematic diagram of the first embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the second embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of the third embodiment of the present invention;

[0027] Figure 6 This is a schematic diagram of the fourth embodiment of the present invention;

[0028] Figure 7 This is a detailed schematic diagram of the first embodiment of the present invention;

[0029] Figure 8 This is a detailed schematic diagram of the second embodiment of the present invention;

[0030] Figure 9 This is a detailed schematic diagram of the third embodiment of the present invention;

[0031] Figure 10 This is a detailed schematic diagram of the fourth embodiment of the present invention;

[0032] Figure 11 This is another specific schematic diagram of the fourth embodiment of the present invention;

[0033] Figure 12 This is a timing diagram showing the relationship between the driving signal GS_31 and the level signal at connection point V1 when designing a discharge circuit using NMOS in the third embodiment of the present invention.

[0034] Figure 13 This is a timing diagram showing the relationship between the driving signal GS_31 and the level signal of the connection point V1 when designing a discharge circuit using PMOS in the first embodiment of the present invention. Detailed Implementation

[0035] The technical solution of the present invention will be described more clearly and completely below with reference to the accompanying drawings of the embodiments provided. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] First Embodiment

[0037] refer to Figure 3 and Figure 7 , Figure 3 This is a block diagram of the active clamping absorption circuit described in this embodiment. Figure 7 This is a detailed schematic diagram of this embodiment;

[0038] In this embodiment, an active clamping circuit is provided, applied to the secondary rectifier circuit of a switching power supply converter that transfers energy during both the positive and negative half-cycles of the transformer. The converter includes an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201 connected in sequence. The secondary rectifier circuit is a bridge rectifier circuit with four connection points, namely V1, V2, V3, and V4. Connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The active clamping absorption circuit includes a suppression circuit, a first rectifier circuit, a second rectifier circuit, and a discharge circuit. The second end of the circuit, the second end of the first rectifier circuit, the second end of the second rectifier circuit, and the second end of the discharge circuit are connected together to form connection point V0; the first end of the first rectifier circuit and the first end of the second rectifier circuit are connected to connection points V2 and V3 respectively; the first end of the discharge circuit is connected to connection point V1, and the first end of the suppression circuit is connected to connection point V4; the starting edge of the drive signal of the discharge circuit lags behind the rising edge of the signal at connection point V1, resulting in a dead time dt1 > 0; the ending edge of the drive signal of the discharge circuit leads the falling edge of the signal at connection point V1, resulting in a dead time dt2 > 0.

[0039] Specifically, the secondary-side rectifier circuit is a bridge rectifier circuit, including four switching transistors, namely TR201, TR202, TR203, and TR204. All four switching transistors are N-type MOSFETs. The drain of switching transistor TR201 is connected to the drain of switching transistor TR203 as connection point V1. The source of switching transistor TR201 is connected to the drain of switching transistor TR202 and the same-name terminal of the secondary winding as connection point V2. The source of switching transistor TR203 is connected to the drain of switching transistor TR204 and the opposite-name terminal of the secondary winding as connection point V3. The source of switching transistor TR202 is connected to the source of switching transistor TR204 as connection point V4.

[0040] Specifically, the secondary rectifier circuit and the suppression circuit are only allowed to be connected through the rectifier circuit, the switching transistor, and the wiring; they are not allowed to be connected through other circuits, inductors, or transformers.

[0041] An active clamping absorption circuit is applied to a bridge rectifier circuit, requiring only two rectifier circuits. The first and second rectifier circuits can be designed using diodes, and the direction of the current absorption of the rectifier diodes is designed according to the stress absorption current of the rectifier diodes. In this embodiment, the first and second rectifier circuits are diodes D311 and D321, respectively. The cathodes of diodes D311 and D321 are connected to connection points V2 and V3, respectively, and diodes D311 and D321 are connected together to form connection point V0.

[0042] The suppression circuit uses two sets of equal-value capacitors C311 and C321 for absorption. The absorption capacitors are positioned close to the secondary rectifier switch transistors where they act. In the actual implementation, capacitors C311 and C321 are connected in parallel.

[0043] like Figure 7 As shown, the discharge circuit is connected between the connection point V4 and the connection point V0 between the secondary rectifier circuit and the secondary ground. As a specific implementation of the discharge circuit, the discharge circuit includes a switching transistor TR301. In the specific implementation, the switching transistor TR301 is a PMOS transistor. The driving signal GS_31 of the discharge circuit, which is also the driving signal GS_31 of the switching transistor TR301, has a certain timing relationship with the voltage jump at the connection point V1 of the secondary rectifier circuit and the energy storage filter inductor L. The starting edge of the driving signal GS_31 lags behind the rising edge of the signal at the connection point V1, resulting in a dead time dt1 > 0; the ending edge of the driving signal GS_31 leads the falling edge of the signal at the connection point V1, resulting in a dead time dt2 > 0.

[0044] The specific working process of the active clamping absorption circuit described in this embodiment is as follows:

[0045] The switching transistor TR301 in the discharge circuit is designed using a PMOS transistor. Figure 13 This is a timing diagram showing the relationship between the drive signal GS_31 and the connection point V1 when designing the discharge circuit using PMOS in this embodiment.

[0046] When switching transistors TR201 and TR204 are off in the full-bridge rectifier circuit, switching transistors TR202 and TR203 are on, and the voltage level of connection point V1 flips to a high level. At this time, switching transistor TR201 absorbs stress through the loop "TR201→C311→D311→TR201", and switching transistor TR204 absorbs stress through the loop "TR204→TR203→C321→D311→TR202→TR204". Since C311 and D311 can be placed close to TR201, the stress in this branch can be effectively reduced.

[0047] After the dead time dt1, the switching transistor TR301 in the discharge circuit is turned on due to the drive signal GS_31. At this time, the energy of capacitor C311 (including C321) in the suppression circuit is released through the loop "TR301→C311→L→Vo". The energy is partially recovered, and capacitor C311 is reset to the plateau voltage (including C321) to prepare for absorption in the next cycle. Here, Vo is the connection point of energy storage filter inductor L and capacitor C201, which serves as the output terminal of the active clamp absorption circuit.

[0048] After the enable time DT2 of the drive signal GS_31, the switch TR301 is turned off, and the capacitor C311 (including C321) in the suppression circuit stops discharging. Furthermore, since a dead time dt2 is required after the enable time DT2 of the drive signal GS_31 ends, all four switches in the bridge rectifier circuit will only enter the fully conducting stage, and the voltage level at connection point V1 will then flip to low. When the voltage level at connection point V1 flips to low, the switch TR301 is already turned off, and the energy of the capacitor C311 (including C321) in the suppression circuit is maintained at the plateau voltage, preventing efficiency loss due to excessive discharge.

[0049] Entering the next phase cycle, when switches TR202 and TR203 of the full-bridge rectifier circuit are turned off, switches TR201 and TR204 are turned on. The level signal at connection point V1 flips to a high level again. At this time, switch TR203 absorbs stress through the loop "TR203→C321→D321→TR203", and switch TR202 absorbs stress through the loop "TR202→TR201→C321→D321→TR204→TR202". Since capacitor C321 and diode D321 are close to switch TR203, the stress in this branch can be effectively reduced. The subsequent process of the drive signal GS_31 flipping before and after is the same as the previous phase cycle, and will not be described again.

[0050] Second Embodiment

[0051] refer to Figure 4 and Figure 8 , Figure 4 This is a schematic block diagram of the second embodiment of the active clamp absorption circuit of the present invention. Figure 8 This is a detailed schematic diagram of this embodiment. Unlike the first embodiment, in this embodiment, the first end of the discharge circuit is connected to connection point V4, the first end of the suppression circuit is connected to connection point V1, the first rectifier circuit and the second rectifier circuit are diodes D311 and D321, respectively, the anodes of diodes D311 and D321 are connected to connection points V2 and V3, respectively, and the cathodes are connected together to point V0.

[0052] The suppression circuit uses two sets of equal-capacitance capacitors C311 and C321 for absorption, and the absorption capacitors are arranged in a way that corresponds to the secondary rectifier switch transistors that act on them.

[0053] The discharge circuit is connected between the connection point V1 and the connection point V0 of the secondary rectifier circuit and the energy storage filter inductor L. As a specific implementation of the discharge circuit, the discharge circuit includes a switch TR301 and a diode D301 connected in parallel, wherein the switch TR301 is an NMOS transistor.

[0054] Similar to the first embodiment, the driving signal GS_31 of the discharge circuit has a certain timing relationship with the voltage jump at the connection point V1 of the secondary rectifier circuit and the energy storage filter inductor L. The starting edge of the driving signal GS_31 lags behind the rising edge of the signal at the connection point V1, resulting in a dead time dt1 > 0; the ending edge of the driving signal GS_31 leads the falling edge of the signal at the connection point V1, resulting in a dead time dt2 > 0.

[0055] The working principle of this circuit is basically the same as that of the first embodiment, with two differences: First, due to the alternation of the positions of the suppression circuit and the discharge circuit, the stress absorption path of each switch in the bridge rectifier circuit changes; second, since the discharge circuit is designed using NMOS transistors, the corresponding drive signal GS_31 enable signal is a high-level signal. Other working details will not be elaborated further.

[0056] Third Embodiment

[0057] refer to Figure 5 and Figure 9 , Figure 5 This is a schematic diagram of the principle of this embodiment. Figure 9 This is a detailed schematic diagram of this embodiment. Unlike the first embodiment, this embodiment provides an active clamping absorption circuit applied to the secondary rectifier circuit of a switching power converter that transfers energy during both the positive and negative half-cycles of the transformer. The converter includes, in sequence, an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201. The secondary rectifier circuit is a full-wave rectifier circuit. The secondary rectifier circuit and the secondary winding of the transformer have four connection points: V1, V2, V3, and V4. Connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The active clamping absorption circuit includes a suppression circuit... A first rectifier circuit, a second rectifier circuit, and a discharge circuit; the second terminals of the suppression circuit, the first rectifier circuit, the second rectifier circuit, and the discharge circuit are connected together to form a connection point V0; the first terminals of the first rectifier circuit and the second rectifier circuit are connected to connection points V2 and V3 respectively; the first terminal of the discharge circuit is connected to connection point V1, and the first terminal of the suppression circuit is connected to connection point V4; the starting edge of the drive signal of the discharge circuit lags behind the rising edge of the signal at connection point V1, resulting in a dead time dt1 > 0; the ending edge of the drive signal of the discharge circuit leads the falling edge of the signal at connection point V1, resulting in a dead time dt2 > 0.

[0058] Specifically, the secondary winding of the transformer includes a first winding T-1 and a second winding T-2; the secondary rectifier circuit includes a switching transistor TR201 and a switching transistor TR202; the same-name terminal of the first winding T-1 is connected to the opposite-name terminal of the second winding T-2 as connection point V1, the opposite-name terminal of the first winding T-1 is connected to the drain of the switching transistor TR201 as connection point V2, the same-name terminal of the second winding T-2 is connected to the drain of the switching transistor TR202 as connection point V3, and the source of the switching transistor TR201 and the source of the switching transistor TR202 are connected as connection point V4.

[0059] The first rectifier circuit and the second rectifier circuit are diodes D311 and D321, respectively. The anodes of diodes D311 and D321 are connected to connection points V2 and V3, respectively, and their cathodes are connected together to connection point V0.

[0060] The suppression circuit uses two sets of equal-capacitance capacitors C311 and C321 for absorption, and the absorption capacitors are arranged in a way that corresponds to the secondary rectifier switch transistors that act on them.

[0061] The discharge circuit is connected between the connection point V1 and the connection point V0 of the secondary rectifier circuit and the energy storage filter inductor L. In specific implementation, the discharge circuit includes a switch TR301 and a diode D301 connected in parallel, wherein the switch TR301 is an NMOS transistor.

[0062] Similar to the first embodiment, the driving signal GS_31 of the discharge circuit has a certain timing relationship with the voltage jump at the connection point V1 of the secondary rectifier circuit and the energy storage filter inductor L. The starting edge of the driving signal GS_31 lags behind the rising edge of the signal at the connection point V1, resulting in a dead time dt1 > 0; the ending edge of the driving signal GS_31 leads the falling edge of the signal at the connection point V1, resulting in a dead time dt2 > 0.

[0063] The specific working process of the active clamping absorption circuit described in this embodiment is as follows:

[0064] In the third embodiment, the discharge circuit is designed using an NMOS transistor. Figure 12 This is a timing diagram showing the relationship between the drive signal GS_31 and the level signal at connection point V1 when designing the discharge circuit using NMOS in this embodiment.

[0065] When the switch TR201 of the full-wave rectifier circuit is turned off, the switch TR202 is turned on, and the level signal at connection point V1 flips to a high level. At this time, the switch TR201 absorbs stress through the loop "TR201→D311→C311→TR201". Since the capacitor C311 and the diode D311 can be placed close to the switch TR201, the stress in this branch can be effectively reduced.

[0066] After the dead time dt1, the switching transistor TR301 in the discharge circuit is turned on due to the drive signal GS_31. At this time, the energy of the capacitor C311 (including C321) in the suppression circuit is released through the loop "C311→TR301→L→Vo". The energy is partially recovered, and the capacitor C311 is reset to the plateau voltage (including C321) to prepare for the absorption function in the next cycle.

[0067] After the enable time DT2 of the drive signal GS_31, the switch TR301 is turned off, and the capacitor C311 (including C321) in the suppression circuit stops discharging. Furthermore, since a dead time dt2 is required after the enable time DT2 of the drive signal GS_31 ends, both switches in the full-wave rectifier circuit only enter the fully conducting stage, and the voltage level at connection point V1 only then flips to low. When the voltage level at connection point V1 flips to low, the switch TR301 is already turned off, and the energy of the capacitor C311 (including C321) in the suppression circuit is maintained at the plateau voltage, preventing efficiency loss due to excessive discharge.

[0068] Entering the next phase cycle, when the full-wave rectifier circuit's switch TR202 is turned off, switch TR201 is turned on, and the voltage level at connection point V1 flips to high again. At this time, switch TR202 absorbs stress through the loop "TR202→C321→D321→TR202". Since capacitor C321 and diode D321 can be placed close to TR202, the stress in this branch can be effectively reduced. The subsequent process of the drive signal GS_31 flipping before and after is the same as the previous phase cycle, and will not be described again.

[0069] Fourth embodiment

[0070] refer to Figure 6 and Figure 10 , Figure 6 This is a block diagram of the active clamping absorption circuit described in this embodiment. Figure 10This is a schematic diagram of the specific principle of this embodiment. In this embodiment, an active clamping absorption circuit is provided, applied to the secondary rectifier circuit of a switching power converter that transfers energy in both the positive and negative half-cycles of the transformer. The converter includes an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201 connected in sequence. The secondary rectifier circuit is a full-wave rectifier circuit. The secondary rectifier circuit and the secondary winding of the transformer have four connection points, namely V1, V2, V3, and V4. Connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The active clamping absorption circuit includes a suppression circuit and a first rectifier circuit. The circuit comprises a second rectifier circuit and a discharge circuit; the second terminals of the first rectifier circuit and the second rectifier circuit are connected to connection points V2 and V3, respectively; the second terminal of the suppression circuit is connected to the second terminal of the discharge circuit to form connection point V0; the first terminals of the first rectifier circuit, the second rectifier circuit, and the suppression circuit are all connected to connection point V1, and the first terminal of the discharge circuit is connected to connection point V4; the starting edge of the drive signal of the discharge circuit lags behind the rising edge of the signal at connection point V1, resulting in a dead time dt1 > 0; the ending edge of the drive signal of the discharge circuit leads the falling edge of the signal at connection point V1, resulting in a dead time dt2 > 0.

[0071] Specifically, the secondary winding of the transformer includes a first winding T-1 and a second winding T-2; the secondary rectifier circuit includes a switching transistor TR201 and a switching transistor TR202; the same-name terminal of the first winding T-1 is connected to the opposite-name terminal of the second winding T-2 as connection point V1, the opposite-name terminal of the first winding T-1 is connected to the drain of the switching transistor TR201 as connection point V2, the same-name terminal of the second winding T-2 is connected to the drain of the switching transistor TR202 as connection point V3, and the source of the switching transistor TR201 and the source of the switching transistor TR202 are connected as connection point V4.

[0072] As a specific implementation of the first and second rectifier circuits, the first and second rectifier circuits are respectively diodes D311 and D321. Diode D311 is connected in parallel across the first winding T-1, and diode D321 is connected in parallel across the second winding T-2. Specifically, the cathodes of diodes D311 and D321 are connected to connection point V1, the anode of diode D311 is connected to connection point V2, and the anode of diode D321 is connected to connection point V3.

[0073] The suppression circuit uses two sets of equal-capacitance capacitors C311 and C321 for absorption, and the absorption capacitors are arranged in a way that corresponds to the secondary rectifier switch transistors that act on them.

[0074] The discharge circuit is connected between the connection point V4 and the connection point V0 between the secondary rectifier circuit and the secondary ground. In specific implementation, the discharge circuit includes a switching transistor TR301, which is a PMOS transistor TR301.

[0075] Similar to the first embodiment, the driving signal GS_31 of the discharge circuit has a certain timing relationship with the voltage jump at the connection point V1 of the secondary rectifier circuit and the energy storage filter inductor L. The starting edge of the driving signal GS_31 lags behind the rising edge of the signal at the connection point V1, resulting in a dead time dt1 > 0; the ending edge of the driving signal GS_31 leads the falling edge of the signal at the connection point V1, resulting in a dead time dt2 > 0.

[0076] The working principle of this circuit is basically the same as that of the third embodiment, with two differences: First, due to the alternation of the positions of the suppression circuit and the discharge circuit, the stress absorption path of each switch in the full-wave rectifier circuit changes. When switch TR201 is turned off, it needs to be absorbed through the loop "TR201→D311→C311→D301→TR201", and when switch TR202 is turned off, it needs to be absorbed through the loop "TR202→D321→C311→D301→TR202". Second, since the discharge circuit is designed using PMOS, the corresponding drive signal GS_31 enable signal is a negative voltage type. Other working contents will not be described in detail.

[0077] refer to Figure 11 As a preferred embodiment, the active clamping absorption circuit further includes a third rectifier and a fourth rectifier. The second end of the third rectifier circuit and the second end of the fourth rectifier circuit are connected to connection point V0, and the first end of the third rectifier circuit and the first end of the fourth rectifier circuit are connected to connection point V2 and connection point V3, respectively.

[0078] Specifically, the third rectifier is diode D312, and the fourth rectifier is diode D322. The anodes of diodes D312 and D322 are both connected to connection point VO, the cathode of diode D312 is connected to connection point V2, and the cathode of diode D322 is connected to connection point V3.

[0079] When switch TR201 is turned off, it needs to be absorbed through the loop "TR201→D311→C311→D322→TR202→TR201". When switch TR202 is turned off, it needs to be absorbed through the loop "TR202→D321→C311→D312→TR201→TR202".

[0080] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention. Further details will not be provided here, and the protection scope of the present invention should be determined by the scope defined in the claims.

Claims

1. An active clamping absorption circuit, applied to the secondary rectifier circuit of a switching power converter that transfers energy during both the positive and negative half-cycles of the transformer, the converter comprising, in sequence, an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201, characterized in that, The secondary-side rectifier circuit is a bridge rectifier circuit with four connection points: V1, V2, V3, and V4. Connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The active clamping absorption circuit includes a suppression circuit, a first rectifier circuit, a second rectifier circuit, and a discharge circuit. The second terminals of the suppression circuit, the first rectifier circuit, the second rectifier circuit, and the discharge circuit are connected together to form connection point V0. The first terminals of the first rectifier circuit and the second rectifier circuit are connected to connection points V2 and V3, respectively. The first terminal of the discharge circuit is connected to the connection point V0. Point V1 is connected, and the first end of the suppression circuit is connected to point V4; or, the first end of the discharge circuit is connected to point V4, and the first end of the suppression circuit is connected to point V1. The starting edge of the drive signal of the discharge circuit lags behind the rising edge of the signal at point V1, resulting in a dead time dt1 > 0. The ending edge of the drive signal of the discharge circuit leads the falling edge of the signal at point V1, resulting in a dead time dt2 > 0. Point V2 is connected to the first input terminal of the secondary rectifier circuit, and point V3 is connected to the second input terminal of the secondary rectifier circuit.

2. The active clamping absorption circuit according to claim 1, characterized in that, The first rectifier circuit includes diode D311, and the second rectifier circuit includes diode D321. When the first terminal of the discharge circuit is connected to connection point V1 and the first terminal of the suppression circuit is connected to connection point V4, the cathodes of diodes D311 and D321 both serve as the second terminals of the corresponding rectifier circuits, and the anodes both serve as the first terminals of the corresponding rectifier circuits. When the first terminal of the discharge circuit is connected to connection point V4 and the first terminal of the suppression circuit is connected to connection point V1, the cathodes of diodes D311 and D321 both serve as the first terminals of the corresponding rectifier circuits, and the anodes both serve as the second terminals of the corresponding rectifier circuits.

3. The active clamping absorption circuit according to claim 1, characterized in that, The suppression circuit includes capacitors C311 and C321 connected in parallel.

4. The active clamping absorption circuit according to claim 1, characterized in that, The discharge circuit includes a switching transistor TR301. When the first end of the discharge circuit is connected to the connection point V1, the switching transistor TR301 is an N-type MOS transistor, with the first end being the source and the second end being the drain. When the first end of the discharge circuit is connected to the connection point V4, the switching transistor TR301 is a P-type MOS transistor, with the second end being the drain and the first end being the source.

5. The active clamping absorption circuit according to claim 4, characterized in that, The discharge circuit also includes a diode D301. When the switching transistor TR301 is an N-type MOSFET, the anode of the diode D301 is connected to the source of the switching transistor TR301, and the cathode is connected to the drain of the switching transistor TR301. When the switching transistor TR301 is a P-type MOSFET, the anode of the diode D301 is connected to the drain of the switching transistor TR301, and the cathode is connected to the source of the switching transistor TR301.

6. An active clamping absorption circuit, applied to the secondary rectifier circuit of a switching power converter that transfers energy during both the positive and negative half-cycles of the transformer, the converter comprising, in sequence, an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201, characterized in that, The secondary rectifier circuit is a full-wave rectifier circuit. Four connection points are provided between the secondary rectifier circuit and the secondary winding of the transformer: V1, V2, V3, and V4. Connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The active clamping absorption circuit includes a suppression circuit, a first rectifier circuit, a second rectifier circuit, and a discharge circuit. The second terminals of the suppression circuit, the first rectifier circuit, the second rectifier circuit, and the discharge circuit are connected to form connection point V0. The first terminal of the first rectifier circuit and the second rectifier circuit... The first terminal is connected to connection points V2 and V3 respectively; the first terminal of the discharge circuit is connected to connection point V1, and the first terminal of the suppression circuit is connected to connection point V4; the start edge of the drive signal of the discharge circuit lags behind the rising edge of the signal at connection point V1, resulting in a dead time dt1 > 0; the end edge of the drive signal of the discharge circuit leads the falling edge of the signal at connection point V1, resulting in a dead time dt2 > 0; connection point V2 is connected to the first input terminal of the secondary rectifier circuit, and connection point V3 is connected to the second input terminal of the secondary rectifier circuit.

7. An active clamping absorption circuit, applied to the secondary rectifier circuit of a switching power converter that transfers energy during both the positive and negative half-cycles of the transformer, the converter comprising, in sequence, an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201, characterized in that, The secondary rectifier circuit is a full-wave rectifier circuit. Four connection points are provided between the secondary rectifier circuit and the secondary winding of the transformer: V1, V2, V3, and V4. Connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The active clamping absorption circuit includes a suppression circuit, a first rectifier circuit, a second rectifier circuit, and a discharge circuit. The second terminals of the first and second rectifier circuits are connected to connection points V2 and V3, respectively. The second terminal of the suppression circuit is connected to the second terminal of the discharge circuit to form connection point V0. The first rectifier circuit... The first terminal, the first terminal of the second rectifier circuit, and the first terminal of the suppression circuit are all connected to connection point V1. The first terminal of the discharge circuit is connected to connection point V4. The start edge of the drive signal of the discharge circuit lags behind the rising edge of the signal at connection point V1, resulting in a dead time dt1 > 0. The end edge of the drive signal of the discharge circuit leads the falling edge of the signal at connection point V1, resulting in a dead time dt2 > 0. Connection point V2 is connected to the first input terminal of the secondary rectifier circuit, and connection point V3 is connected to the second input terminal of the secondary rectifier circuit.

8. The active clamping absorption circuit according to claim 7, characterized in that, The secondary winding of the transformer includes a first winding and a second winding; the secondary rectifier circuit includes a switching transistor TR201 and a switching transistor TR202; the same-name terminal of the first winding is connected to the opposite-name terminal of the second winding as connection point V1, the opposite-name terminal of the first winding is connected to the drain of the switching transistor TR201 as connection point V2, the same-name terminal of the second winding is connected to the drain of the switching transistor TR202 as connection point V3, and the source of the switching transistor TR201 and the source of the switching transistor TR202 are connected as connection point V4.

9. The active clamping absorption circuit according to claim 7, characterized in that, It also includes a third rectifier circuit and a fourth rectifier circuit; the second end of the third rectifier circuit and the second end of the fourth rectifier circuit are connected to connection point V0, and the first end of the third rectifier circuit and the first end of the fourth rectifier circuit are connected to connection point V2 and connection point V3, respectively.

10. A switching power supply converter, characterized in that, The circuit includes an input filter capacitor C101, a main switching transistor circuit, a transformer, a secondary rectifier circuit, an energy storage filter inductor L, and a capacitor C201 connected in sequence. The secondary rectifier circuit and the secondary winding of the transformer have four connection points, namely V1, V2, V3, and V4, wherein connection point V1 is connected to the energy storage filter inductor L, and connection point V4 is grounded. The circuit also includes an active clamping absorption circuit as described in any one of claims 1-9, wherein the active clamping absorption circuit is connected to the secondary rectifier circuit.

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