Active absorption circuit and switching power supply device

Abstract

The application relates to the technical field of switching power supply, and discloses an active absorption circuit and a switching power supply device, wherein the active absorption circuit comprises a spike absorption unit, a driving control unit, a gate voltage protection unit and a discharge unit; the spike absorption unit comprises an absorption capacitor and a second diode, and the negative electrode of the second diode is connected with the absorption capacitor; the driving control unit comprises an absorption MOS tube, a first diode, a first resistor and an energy storage capacitor, the drain electrode of the absorption MOS tube is connected with the positive electrode of the first diode and the second diode, and the negative electrode of the first diode is connected with the first resistor; the gate electrode of the absorption MOS tube is connected with the first resistor and the energy storage capacitor; the source electrode of the absorption MOS tube is connected with the absorption capacitor and the negative electrode of the second diode; the gate voltage protection unit comprises a bidirectional voltage stabilizing diode which is connected in parallel between the gate electrode and the source electrode of the absorption MOS tube; and the discharge unit comprises a second resistor which is connected in parallel across the energy storage capacitor. The active absorption of the spike voltage can be realized in a low-cost mode.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and in particular to an active absorption circuit and a switching power supply device. Background Technology

[0002] Switching power supplies, as core devices in power electronics technology, are widely used in consumer electronics, industrial control, communication power supply, and new energy supporting fields due to their advantages of high efficiency and miniaturization. Power MOSFETs, with their fast switching speed, simple driving method, and low conduction loss, have become the core switching devices in various hard-switching topologies.

[0003] In hard-switching mode, parasitic parameters such as transformer leakage inductance, PCB wiring parasitic inductance, and device lead inductance inevitably exist inside the circuit. When the main power MOSFET is turned off at high speed, the current in the circuit will change drastically, and the parasitic inductance will generate a high reverse induced electromotive force. When this electromotive force is superimposed on the DC bus voltage, it will form a large voltage spike between the drain and source of the MOSFET.

[0004] These voltage spikes can have multiple adverse effects: on the one hand, they can cause MOSFETs to be subjected to voltage stress far exceeding their rated operating range, significantly increasing the probability of device breakdown and failure, and reducing the reliability and lifespan of the power supply system; on the other hand, the high-frequency oscillations accompanying voltage spikes can cause serious electromagnetic interference, deteriorate the electromagnetic compatibility performance of the system, interfere with the normal operation of surrounding circuits, and make it difficult to meet the relevant electromagnetic compatibility specifications of the industry.

[0005] To suppress the aforementioned voltage spikes, the industry mainly adopts two types of technical solutions.

[0006] One is the passive absorption scheme, represented by the RCD absorption circuit. This scheme consists of resistors, capacitors, and diodes. It is widely used due to its simple structure and low material cost. However, its core drawback is that the peak energy stored in the absorption capacitor will be dissipated as heat through the resistor, resulting in additional energy loss and reducing power conversion efficiency. In high-frequency and high-power applications, the energy loss and heat generation problems will be further aggravated.

[0007] The second is the active absorption scheme, with active clamping circuits as a typical example. This scheme can efficiently feed peak energy back to the power supply or load by adding a dedicated control chip, auxiliary drive circuit and active switching device. It has good peak suppression effect and low energy loss, but the circuit structure is complex, the number of components is large, the control logic is complicated, and the research and development and material costs are high. It is only suitable for high-end scenarios with extremely high efficiency requirements and low cost sensitivity, and cannot be applied on a large scale in economic and popular power supply products.

[0008] In summary, low-cost passive absorption schemes come at the cost of conversion efficiency, while high-efficiency active absorption schemes are limited by structure and cost, making them unpopular. The industry has always lacked a solution that is simple in structure, low in cost, easy to control, and can achieve efficient peak suppression and energy recovery. Summary of the Invention

[0009] To address the aforementioned issues, this invention proposes an active absorption circuit and a switching power supply device that can achieve active absorption of peak voltages at low cost. This can be applied to the absorption of Vds peaks in switching power supply MOSFETs, reducing voltage stress on the MOSFETs and improving the EMI performance of the switching power supply.

[0010] The technical solution adopted in this invention is as follows: An active absorption circuit includes a spike absorption unit, a drive control unit, a gate voltage protection unit, and a discharge unit; The peak absorption unit includes an absorption capacitor C1 and a second diode D2, with the negative terminal of the second diode D2 connected to the absorption capacitor C1. The drive control unit includes an absorption MOSFET Q1, a first diode D1, a first resistor R1, and an energy storage capacitor C2. The drain of the absorption MOSFET Q1 is connected to the anodes of the first diode D1 and the second diode D2, and the cathode of the first diode D1 is connected to the first resistor R1. The gate of the absorption MOSFET Q1 is connected to the first resistor R1 and the energy storage capacitor C2. The source of the absorption MOSFET Q1 is connected to the cathodes of the absorption capacitor C1 and the second diode D2. The energy of the absorption capacitor C1 is fed back to the external load through the absorption MOSFET Q1. The gate voltage protection unit includes a bidirectional Zener diode D3 connected between the gate and source of the absorption MOS transistor Q1; The discharge unit includes a second resistor R2 connected in parallel across the energy storage capacitor C2.

[0011] Furthermore, the second diode D2 is a Schottky diode or a fast recovery diode.

[0012] Furthermore, the bidirectional Zener diode D3 is a single-package bidirectional Zener diode, or it is composed of two unidirectional Zener diodes connected back to back.

[0013] Furthermore, the absorption capacitor C1 is an adjustable capacitor, and the voltage spike absorption effect can be changed by adjusting the capacitance of the absorption capacitor C1.

[0014] Furthermore, the second resistor R2 is used to slowly discharge the residual voltage after the energy storage capacitor C2 is de-energized.

[0015] A switching power supply device includes a main power topology circuit and an active absorption circuit. The main power topology circuit includes a full-bridge synchronous rectification topology. In the active absorption circuit, the end of the absorption capacitor C1 furthest from the second diode D2 is connected to the front-end node of the LC filter inductor of the full-bridge synchronous rectification topology. The source of the absorption MOSFET Q1 is connected to the negative output terminal of the full-bridge synchronous rectification topology. The energy of the absorption capacitor C1 is fed back to the load terminal of the full-bridge synchronous rectification topology via the absorption MOSFET Q1.

[0016] Furthermore, the energy storage capacitor C2, in conjunction with the first resistor R1, controls the absorption MOS transistor Q1 to conduct and discharge during the inductor freewheeling phase.

[0017] Furthermore, the switching on and off of the absorption MOSFET Q1 is automatically driven by the drain-source voltage of the main power MOSFET in the main power topology circuit of the switching power supply through the drive control unit, without the need for an additional drive chip and an independent drive power supply.

[0018] A switching power supply device includes a main power topology circuit and an active absorption circuit. The main power topology circuit includes a flyback converter primary topology. In the active absorption circuit, the end of the absorption capacitor C1 away from the second diode D2 is connected to the drain of the main power MOSFET in the primary topology of the flyback converter. The source of the absorption MOSFET Q1 is connected to the negative terminal of the DC bus of the primary topology of the flyback converter. The drain-source spike energy absorbed by the absorption capacitor C1 is fed back to the power supply terminal of the primary topology of the flyback converter via the absorption MOSFET Q1.

[0019] A switching power supply device includes a main power topology circuit and an active absorption circuit. The main power topology circuit includes a full-wave synchronous rectification topology. In the active absorption circuit, the end of the absorption capacitor C1 furthest from the second diode D2 is connected to the drain of the rectifier MOSFET of the full-wave synchronous rectification topology. The source of the absorption MOSFET Q1 is connected to the output terminal of the full-wave synchronous rectification topology. The energy of the absorption capacitor C1 is fed back to the load of the full-wave synchronous rectification topology through the absorption MOSFET Q1.

[0020] The beneficial effects of this invention are as follows: 1. This invention uses conventional discrete components to build a modular circuit, which does not require a dedicated control chip and an independent drive power supply. The overall structure is simple and easy to assemble. The material cost is the same as that of traditional passive absorption circuits, but it can achieve efficient peak suppression and energy recovery effects of active absorption, thus balancing low cost and high performance.

[0021] 2. This invention uses the voltage signal of the main power device to realize the automatic driving of the absorption device. The control logic is simple and direct, and it can be adapted to various switching power supply topologies such as full-bridge synchronous rectification, flyback converter primary side, and full-wave synchronous rectification, making it highly versatile. The suppression effect of the absorption capacitor can be flexibly adjusted to match the voltage spike absorption requirements under different operating conditions.

[0022] 3. In this invention, the peak energy captured by the absorption capacitor can be efficiently fed back to the load or power supply through the absorption device. The circuit has no energy dissipation components, completely avoiding the resistive heat loss of traditional passive absorption, significantly improving the power conversion efficiency, and improving the circuit heating condition.

[0023] 4. In this invention, after the voltage spikes are effectively suppressed, the voltage stress of the main power devices is greatly reduced, the risk of device breakdown is significantly reduced, and the system's operational stability and service life are improved. The circuit can also weaken high-frequency oscillations and reduce electromagnetic interference, making the system more likely to meet electromagnetic compatibility requirements. Combined with the safety protection design of the discharge unit, the safety of circuit use and maintenance is further improved. Attached Figure Description

[0024] Figure 1 This is a block diagram of an active absorption circuit according to the present invention.

[0025] Figure 2 yes Figure 1 The ideal waveform of an active absorption circuit.

[0026] Figure 3 yes Figure 2 A schematic diagram of the current flow direction during the t1-t2 stage of the waveform.

[0027] Figure 4 yes Figure 2 A schematic diagram of the current flow direction during the t2-t3 stage of the waveform.

[0028] Figure 5 yes Figure 2 A schematic diagram of the current flow direction during the t3-t4 stage of the waveform.

[0029] Figure 6 Based on Figure 1 The DS spike simulation waveform diagram under the active absorption circuit of this invention has not been added.

[0030] Figure 7 Based on Figure 1 The simulation waveform diagram of the DS spike under the active absorption circuit of this invention has been added. Detailed Implementation

[0031] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0032] Example 1 like Figure 1 As shown, this embodiment provides an active absorption circuit, including a spike absorption unit, a drive control unit, a gate voltage protection unit, and a discharge unit, wherein: The peak absorption unit includes an absorption capacitor C1 and a second diode D2, with the negative terminal of the second diode D2 connected to the absorption capacitor C1.

[0033] The drive control unit includes a MOSFET Q1, a first diode D1, a first resistor R1, and an energy storage capacitor C2. The drain of the MOSFET Q1 is connected to the positive terminals of the first diode D1 and the second diode D2, and the negative terminal of the first diode D1 is connected to the first resistor R1. The gate of the MOSFET Q1 is connected to the first resistor R1 and the energy storage capacitor C2. The source of the MOSFET Q1 is connected to the negative terminals of the MOSFET C1 and the second diode D2. The energy of the MOSFET C1 is fed back to the external load through the MOSFET Q1.

[0034] The gate voltage protection unit includes a bidirectional Zener diode D3 connected between the gate and source of the absorption MOSFET Q1.

[0035] The discharge unit includes a second resistor R2 connected in parallel across the energy storage capacitor C2.

[0036] Preferably, the second diode D2 is a Schottky diode or a fast recovery diode. It should be noted that selecting this type of diode can improve the circuit's turn-on and turn-off response speed, reduce the diode's own power loss, and ensure the timeliness of peak energy absorption.

[0037] Preferably, the bidirectional Zener diode D3 is a single-package bidirectional Zener diode, or it can be composed of two unidirectional Zener diodes connected back to back. It should be noted that both methods can stably clamp and absorb the gate-source voltage of the MOSFET Q1, preventing damage to the device due to excessive voltage and improving the circuit's protection reliability.

[0038] Preferably, the absorption capacitor C1 is an adjustable capacitance capacitor, and the voltage spike absorption effect can be changed by adjusting the capacitance value of the absorption capacitor C1. Specifically, an adjustable capacitance absorption capacitor C1 is used in the spike absorption unit. The capacitance value of the absorption capacitor C1 is adjusted according to the actual amplitude of the voltage spike in the circuit to adapt to different spike absorption requirements. It should be noted that the capacitance value of the absorption capacitor can be flexibly adjusted so that the circuit can adapt to voltage spike suppression under different operating conditions, improving the versatility of the circuit.

[0039] Preferably, the second resistor R2 is used to slowly discharge residual voltage after the energy storage capacitor C2 is de-energized. Specifically, by connecting the second resistor R2 in parallel across the energy storage capacitor C2, when the entire active absorption circuit is de-energized and stops working, the residual charge inside the energy storage capacitor C2 forms a discharge circuit through the second resistor R2, gradually releasing the charge. It should be noted that the second resistor R2 can prevent residual voltage in the energy storage capacitor C2 after de-energization, eliminate the potential for electrical contamination in the circuit, and improve the safety of equipment use and maintenance.

[0040] This embodiment also provides a switching power supply device, including a main power topology circuit of the switching power supply and the above-mentioned active absorption circuit, which are described in detail below.

[0041] Preferably, the main power topology of the switching power supply can be a full-bridge synchronous rectification topology. In the active snubber circuit, the end of the snubber capacitor C1 furthest from the second diode D2 is connected to the front-end node of the LC filter inductor of the full-bridge synchronous rectification topology. The source of the snubber MOSFET Q1 is connected to the negative output terminal of the full-bridge synchronous rectification topology. The energy of the snubber capacitor C1 is fed back to the load terminal of the full-bridge synchronous rectification topology through the snubber MOSFET Q1. It should be noted that this switching power supply device can effectively suppress voltage spikes in the full-bridge synchronous rectification topology, reduce voltage stress on the main power devices, and improve power conversion efficiency.

[0042] More preferably, the energy storage capacitor C2 and the first resistor R1 work together to control the conduction and discharge of the absorption MOSFET Q1 during the inductor freewheeling phase. Specifically, during the inductor freewheeling phase of the full-bridge synchronous rectification topology, the energy storage capacitor C2 and the first resistor R1 work together to generate a drive signal that triggers the absorption MOSFET Q1 to conduct. The peak energy stored inside the absorption capacitor C1 is then discharged through the conducting absorption MOSFET Q1. It should be noted that this method can precisely control the conduction timing of the absorption MOSFET Q1, achieving directional release of peak energy and ensuring the effectiveness of energy feedback.

[0043] More preferably, the switching on and off of the absorption MOSFET Q1 is automatically driven by the drain-source voltage of the main power MOSFET in the main power topology circuit of the switching power supply through the drive control unit, without the need for an additional drive chip or independent drive power supply. Specifically, the drive control unit directly acquires the drain-source voltage of the main power MOSFET as the drive signal, and automatically controls the switching on and off of the absorption MOSFET Q1 according to the voltage change, without the need for an external dedicated drive chip or independent drive power supply. It should be noted that this method can eliminate additional drive devices and power supply circuits, greatly simplifying the circuit structure and reducing the production cost and control complexity of the device.

[0044] Preferably, the main power topology of the switching power supply can be a flyback converter primary-side topology. In the active snubber circuit, the end of the snubber capacitor C1 furthest from the second diode D2 is connected to the drain of the main power MOSFET in the primary-side topology of the flyback converter. The source of the snubber MOSFET Q1 is connected to the negative terminal of the DC bus of the primary-side topology of the flyback converter. The energy spike from the drain and source of the main power MOSFET absorbed by the snubber capacitor C1 is fed back to the power supply terminal of the primary-side topology of the flyback converter via the snubber MOSFET Q1. It should be noted that this method can effectively suppress voltage spikes on the primary side of the flyback converter, protect the main power MOSFET, and simultaneously achieve energy recovery, thereby improving the operating efficiency of the flyback power supply.

[0045] Preferably, the main power topology of the switching power supply can be a full-wave synchronous rectification topology. In the active absorption circuit, the end of the absorption capacitor C1 furthest from the second diode D2 is connected to the drain of the rectifier MOSFET of the full-wave synchronous rectification topology, and the source of the absorption MOSFET Q1 is connected to the output terminal of the full-wave synchronous rectification topology. The energy of the absorption capacitor C1 is fed back to the load of the full-wave synchronous rectification topology through the absorption MOSFET Q1. It should be noted that this method is adapted to the spike suppression requirements of the full-wave synchronous rectification topology, reducing energy loss and optimizing the electromagnetic compatibility performance of the power supply while reducing device voltage stress.

[0046] Example 2 This embodiment provides an active absorption circuit, such as Figure 1 As shown in the dashed box, C1 is the peak voltage absorption capacitor, D2 provides a unidirectional path for the charging current of C1, Q1 provides a discharge path for C1, D3 clamps the GS voltage of Q1, D1 and R1 enable unidirectional charging of C2, the voltage on C2 ensures that Q1 is turned on when it is necessary to discharge the absorption capacitor C1, and the function of R2 is to slowly discharge C2 to ensure that there is no voltage on C2 after power-off.

[0047] It should be noted that the active absorption circuit in this embodiment is applicable to most applications where the MOSFET's drain-source voltage has spikes, and is not limited to these applications. Figure 1 The illustrated full-bridge power conversion topology is based on the same inventive concept. Figure 1The active absorption circuit in the middle can be separated, and the circuit parameters can be adjusted to make a small module with peak absorption function.

[0048] The active absorption circuit in this embodiment uses conventional devices such as MOSFETs, diodes, resistors, and capacitors to achieve active absorption of peak voltages. It can be applied to the absorption of Vds peaks in switching power supply MOSFETs, reducing voltage stress on the MOSFETs and improving the EMI performance of the switching power supply.

[0049] Specifically, this active absorption circuit utilizes the Vds voltage of the MOSFET as the drive signal for the active absorption MOSFET, eliminating the need for an external drive signal. This simplifies the control logic, reduces the number of components used, and improves circuit reliability. The spike absorption effect can be adjusted by changing the size of the absorption capacitor, and the turn-on and turn-off timings of the active absorption MOSFET can be achieved using voltage divider resistors and capacitors. The charging and discharging process of the absorption capacitor is primarily handled by the active absorption MOSFET, eliminating the energy loss across the resistors present in traditional RCD passive absorption circuits. Furthermore, the energy from the absorption capacitor can be fed back to the load. Therefore, this active absorption circuit achieves the effect of complex active absorption using simple passive absorption circuitry and components, achieving the effect of active absorption at the cost of passive absorption.

[0050] The active absorption circuit in this embodiment is mainly used for absorbing the voltage spike of the MOSFET in the switching power supply, such as... Figure 1 The circuit shown is for the application of Vds spike absorption in a full-bridge synchronous rectifier MOSFET. With minor modifications, this active absorption circuit can also be applied to more applications such as Vds spike absorption in a flyback primary-side MOSFET and Vds spike absorption in a full-wave synchronous rectifier MOSFET.

[0051] like Figure 1 As shown, the circuit consisting of D1, R1, R2, and C2 within the dashed box controls the turn-on and turn-off of the absorption MOSFET Q1. C1 is the absorption capacitor, D2 is used for peak pre-charging, and D3 is a bidirectional Zener diode, which protects Q1's Vgs voltage from exceeding its rated range. Q6 to Q9 are the primary-side main power MOSFETs, and Q2 to Q5 are the secondary-side rectifier MOSFETs. Q6 and Q9 form one bridge arm, with Q2 and Q5 as their corresponding rectifier bridge arms. Similarly, Q7 and Q8 form the other bridge arm, with Q3 and Q4 as their corresponding rectifier bridge arms.

[0052] Based on the control logic of the switching power supply, under the condition of continuous inductor current (CCM), the ideal waveform is as follows: Figure 2 As shown, it includes the primary-side MOSFET drive waveforms PAH / PAL and PBH / PBL, the secondary-side MOSFET drive waveforms SRAH / SRAL and SRBH / SRBL, and the LC filter inductor front-wave signal SW.

[0053] Figure 2 In the t1-t2 phase of the waveform diagram shown, the bridge arm formed by Q7 and Q8 on the primary side is turned on, and the corresponding rectifier bridge arm formed by Q3 and Q4 on the secondary side is turned on. The current path is as follows. Figure 3 As shown by the dashed line with arrows. In the circuit of this embodiment, the current charges the absorption capacitor C1 through D2, and at the same time, it also charges C2 through D1 and R1. At this time, the GS voltage of Q1 is negative, and Q1 is in the off state until the voltage on the absorption capacitor C1 is the same as SW.

[0054] Figure 2 During the t2-t3 phase of the waveform diagram shown, both primary arms are off, while the secondary side is in freewheeling mode. SW is low at t2, and the gate-source voltage of Q1 suddenly becomes positive, causing Q1 to conduct. The absorption capacitor C1 forms a discharge circuit through Q1 and L1 to the load, as shown in the diagram. Figure 4 As shown by the dashed line with arrows. Since the energy on the absorption capacitor C1 is fed back to the load, the active absorption circuit in this embodiment has very low losses and has almost no impact on the conversion efficiency.

[0055] Figure 2 In the t3-t4 stage of the waveform diagram shown, the bridge arm formed by Q6 and Q9 on the primary side is turned on, and the corresponding rectifier bridge arm formed by Q2 and Q5 on the secondary side is turned on. The current path is as follows. Figure 5 As shown by the dashed line with arrows, the process is similar to stage t1-t2. In this embodiment, the current still charges the absorption capacitor C1 through D2, and simultaneously charges C2 through D1 and R1. At this time, the gate-source voltage (GS) of Q1 is negative, and Q1 is in the off state until the voltage across the absorption capacitor C1 matches SW. Then, after the inductor current freewheeling process in stage t2-t3, the absorption capacitor C1 completes its discharge, and the cycle repeats.

[0056] according to Figure 1 A simulation model of the circuit shown is established. At the instant any bridge arm MOSFET (Q6 and Q9 or Q7 and Q8) turns on, without adding any snubber circuit, the output LC filter inductor... Figure 1 The SW in the waveform will appear as a square wave with damped oscillations, as shown in the figure. Figure 6 As shown. Then, by adding the active absorption circuit of this embodiment, and setting an appropriate capacitance value for the absorption capacitor C1, a good peak absorption effect can be achieved, and its waveform is as follows. Figure 7 As shown, comparing the waveforms before and after adding the absorption circuit, the peak voltage decreased by about 20V after adding the absorption circuit.

[0057] Therefore, this invention perfectly solves the problems of low efficiency in passive absorption and high cost and complexity in active absorption control. It eliminates the need for external control chips and MOSFET drive circuits, using basic components such as MOSFETs, diodes, resistors, and capacitors to achieve efficient absorption of the MOSFET's drain-source (DS) spike voltage in a switching power supply. The MOSFET's Vds voltage is used as the drive signal for the active absorption MOSFET. Without complex control logic, the energy on the absorption capacitor is efficiently fed back to the load or power supply through the absorption MOSFET. In the absorption circuit, energy is not dissipated across the resistors but is directly fed back to the load or power supply in each switching cycle, without reducing the system's conversion efficiency. The switching diodes in this invention can be ordinary Schottky diodes or fast diodes. The bidirectional Zener diode between the MOSFET's gate and source (GS) can be a packaged bidirectional Zener diode or two separate Zener diodes connected back-to-back to achieve the GS voltage clamping function. Other resistors and capacitors have no special requirements; conventional resistors and capacitors are sufficient.

[0058] In summary, by adopting the above design, this invention achieves a solution for efficiently absorbing voltage spikes and at low cost using a simple circuit structure and inexpensive components.

[0059] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims. In the description of the present invention, it should be noted that the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

Claims

1. An active absorption circuit, characterized in that, It includes a spike absorption unit, a drive control unit, a gate voltage protection unit, and a discharge unit; The peak absorption unit includes an absorption capacitor C1 and a second diode D2, with the negative terminal of the second diode D2 connected to the absorption capacitor C1. The drive control unit includes an absorption MOSFET Q1, a first diode D1, a first resistor R1, and an energy storage capacitor C2. The drain of the absorption MOSFET Q1 is connected to the anodes of the first diode D1 and the second diode D2, and the cathode of the first diode D1 is connected to the first resistor R1. The gate of the absorption MOSFET Q1 is connected to the first resistor R1 and the energy storage capacitor C2. The source of the absorption MOSFET Q1 is connected to the cathodes of the absorption capacitor C1 and the second diode D2. The energy of the absorption capacitor C1 is fed back to the external load through the absorption MOSFET Q1. The gate voltage protection unit includes a bidirectional Zener diode D3 connected between the gate and source of the absorption MOS transistor Q1; The discharge unit includes a second resistor R2 connected in parallel across the energy storage capacitor C2.

2. The active absorption circuit according to claim 1, characterized in that, The second diode D2 is a Schottky diode or a fast recovery diode.

3. The active absorption circuit according to claim 1, characterized in that, The bidirectional Zener diode D3 is a single-package bidirectional Zener diode, or it can be composed of two unidirectional Zener diodes connected back to back.

4. The active absorption circuit according to claim 1, characterized in that, The absorption capacitor C1 is an adjustable capacitor, and the voltage spike absorption effect can be changed by adjusting the capacitance of the absorption capacitor C1.

5. The active absorption circuit according to claim 1, characterized in that, The second resistor R2 is used to slowly discharge the residual voltage after the energy storage capacitor C2 is de-energized.

6. A switching power supply device, comprising a main power topology circuit for the switching power supply and an active absorption circuit as described in any one of claims 1-5, characterized in that, The main power topology circuit of the switching power supply includes a full-bridge synchronous rectification topology. In the active absorption circuit, the end of the absorption capacitor C1 away from the second diode D2 is connected to the front-end node of the LC filter inductor of the full-bridge synchronous rectification topology. The source of the absorption MOSFET Q1 is connected to the negative output terminal of the full-bridge synchronous rectification topology. The energy of the absorption capacitor C1 is fed back to the load terminal of the full-bridge synchronous rectification topology through the absorption MOSFET Q1.

7. The switching power supply device according to claim 6, characterized in that, The energy storage capacitor C2 works in conjunction with the first resistor R1 to control the absorption MOS transistor Q1 to conduct and discharge during the inductor freewheeling phase.

8. The switching power supply device according to claim 6, characterized in that, The switching on and off of the absorption MOSFET Q1 is automatically driven by the drain-source voltage of the main power MOSFET in the main power topology circuit of the switching power supply through the drive control unit, without the need for an additional drive chip or independent drive power supply.

9. A switching power supply device, comprising a main power topology circuit for a switching power supply and an active absorption circuit as described in any one of claims 1-5, characterized in that, The main power topology circuit of the switching power supply includes a flyback converter primary topology; in the active absorption circuit, the end of the absorption capacitor C1 away from the second diode D2 is connected to the drain of the main power MOSFET in the primary topology of the flyback converter, the source of the absorption MOSFET Q1 is connected to the negative terminal of the DC bus of the primary topology of the flyback converter, and the drain-source peak energy of the main power MOSFET absorbed by the absorption capacitor C1 is fed back to the power supply terminal of the primary topology of the flyback converter via the absorption MOSFET Q1.

10. A switching power supply device, comprising a main power topology circuit for a switching power supply and an active absorption circuit as described in any one of claims 1-5, characterized in that, The main power topology circuit of the switching power supply includes a full-wave synchronous rectification topology; in the active absorption circuit, the end of the absorption capacitor C1 away from the second diode D2 is connected to the drain of the rectifier MOSFET of the full-wave synchronous rectification topology, the source of the absorption MOSFET Q1 is connected to the output terminal of the full-wave synchronous rectification topology, and the energy of the absorption capacitor C1 is fed back to the load of the full-wave synchronous rectification topology through the absorption MOSFET Q1.

Images