Flyback synchronous rectification circuit, switching power supply and power supply equipment

Abstract

The utility model discloses a flyback synchronous rectification circuit, a switching power supply and power supply equipment. The flyback synchronous rectification circuit comprises a transformer; a voltage output end; the rectifying circuit is connected with the output winding of the transformer and also connected with the voltage output end, and the rectifying circuit is used for rectifying the output current of the output winding of the transformer and then outputting the rectified output current through the voltage output end; and the RCD absorption circuit is connected between the rectifying circuit and the voltage output end in series, the RCD absorption circuit is connected with the output winding of the transformer in parallel, and the RCD absorption circuit is used for absorbing peak voltage generated when the rectifying circuit works. According to the utility model, the problem that the energy loss is large when the inverse peak voltage is absorbed in the rectification circuit is solved.

Description

Technical Field

[0001] This utility model relates to the field of flyback synchronous rectifier circuit, switching power supply and power supply equipment. Background Technology

[0002] MOSFETs are now used as rectifier devices in rectifier circuits. Compared to diodes, MOSFETs have advantages such as low on-resistance, fast switching, and higher current carrying capacity. In switching power supplies, MOSFETs are often used for synchronous rectification. However, during operation, when a MOSFET switches from the on state to the off state, the change in current causes a momentary increase in the voltage between the drain and source, generating a reverse voltage peak, which affects the stability of the circuit.

[0003] In current rectifier circuits, an RC snubber circuit is usually set across the MOSFET to absorb the reverse peak voltage generated when the MOSFET is working. However, in order to ensure a good absorption effect, the RC constant of the RC snubber circuit needs to be set to a large value, which will lead to an increase in the energy loss of the circuit. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this utility model is to provide a flyback synchronous rectifier circuit, a switching power supply and a power supply device to solve the problem of large energy loss when absorbing reverse peak voltage in the rectifier circuit.

[0005] The technical solution of this utility model is as follows:

[0006] This utility model provides a flyback synchronous rectifier circuit, including:

[0007] transformer;

[0008] Voltage output terminal;

[0009] A rectifier circuit is connected to the output winding of the transformer and also to the voltage output terminal. The rectifier circuit is used to rectify the output current of the output winding of the transformer and output it through the voltage output terminal.

[0010] An RCD snubber circuit is connected in series between the rectifier circuit and the voltage output terminal. The RCD snubber circuit is connected in parallel with the output winding of the transformer. The RCD snubber circuit is used to absorb the reverse peak voltage generated when the rectifier circuit is working.

[0011] Optionally, the rectifier circuit includes:

[0012] The positive terminal rectifier circuit is connected to the output winding of the transformer and also to the voltage output terminal. The positive terminal rectifier circuit is used to rectify the positive half-cycle AC power output from the output winding of the transformer and output it through the voltage output terminal.

[0013] The negative-end rectifier circuit is connected to the output winding of the transformer and also to the voltage output terminal. The negative-end rectifier circuit is used to rectify the negative half-cycle AC power output from the output winding of the transformer and output it through the voltage output terminal.

[0014] Optionally, the positive-side rectifier circuit includes a first MOSFET, the gate of which is connected to an external controller, the source of which is connected to the output winding of the transformer, and the drain of which is connected to the voltage output terminal; the negative-side rectifier circuit includes a second MOSFET, the gate of which is connected to an external controller, the source of which is connected to the voltage output terminal, and the drain of which is connected to the output winding of the transformer.

[0015] Optionally, the RCD snubber circuit includes a positive-terminal snubber circuit and a negative-terminal snubber circuit. The positive-terminal snubber circuit is connected in series between the positive-terminal rectifier circuit and the voltage output terminal, and the positive-terminal snubber circuit is connected in parallel with the output winding of the transformer. The negative-terminal snubber circuit is connected in series between the negative-terminal rectifier circuit and the voltage output terminal, and the negative-terminal snubber circuit is connected in parallel with the output winding of the transformer.

[0016] Optionally, the positive terminal absorption circuit includes a first resistor, a first capacitor, and a first diode. The first end of the first resistor and the first end of the first capacitor are connected to the voltage output terminal. The second end of the first resistor and the second end of the first capacitor are connected to the anode of the first diode. The cathode of the first diode is connected to the positive terminal rectifier circuit.

[0017] Optionally, the negative terminal absorption circuit includes a second resistor, a second capacitor, and a second diode. The first end of the second resistor and the first end of the second capacitor are connected to the voltage output terminal. The second end of the second resistor and the second end of the second capacitor are connected to the cathode of the second diode. The anode of the second diode is connected to the positive terminal rectifier circuit.

[0018] Optionally, the flyback synchronous rectifier circuit further includes:

[0019] A filter circuit is connected in parallel with the rectifier circuit. The filter circuit is used to filter the output voltage of the rectifier circuit before outputting it.

[0020] Optionally, the filter circuit includes a third resistor and a third capacitor. The first end of the third resistor is connected to the input terminal of the rectifier circuit, the second end of the third resistor is connected to the first end of the third capacitor, and the second end of the third capacitor is connected to the output terminal of the rectifier circuit.

[0021] This utility model also proposes a switching power supply, including the flyback synchronous rectifier circuit described above.

[0022] This utility model also proposes a power supply device, including the switching power supply described above.

[0023] This utility model's technical solution utilizes a transformer, a voltage output terminal, a rectifier circuit, and an RCD snubber circuit to construct a flyback synchronous rectifier circuit. The rectifier circuit is connected to the transformer's output winding and also to the voltage output terminal. The rectifier circuit rectifies the output current of the transformer's output winding and outputs it through the voltage output terminal. The RCD snubber circuit is connected in series between the rectifier circuit and the voltage output terminal, and also in parallel with the transformer's output winding. The RCD snubber circuit absorbs the reverse peak voltage generated during the operation of the rectifier circuit. Thus, by incorporating the RCD snubber circuit, a good absorption effect on reverse peak voltage can be achieved while maintaining low energy loss. Attached Figure Description

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

[0025] Figure 1 This is a functional module schematic diagram of an embodiment of the flyback synchronous rectifier circuit of this utility model.

[0026] Figure 2 This is a schematic diagram of the circuit structure of an embodiment of the flyback synchronous rectifier circuit of this utility model.

[0027] Figure 3 This is a schematic diagram of the circuit structure of another embodiment of the flyback synchronous rectifier circuit of this utility model.

[0028] Figure 4 This is a schematic diagram of the reverse peak voltage waveform generated in the flyback synchronous rectifier circuit of this utility model.

[0029] Explanation of reference numerals in the attached diagram: 10, rectifier circuit; 20, RCD snubber circuit; 30, filter circuit; T1, transformer; OUT, voltage output terminal; Q1, first MOSFET; Q2, second MOSFET; R1, first resistor; R2, second resistor; R3, third resistor; C1, first capacitor; C2, second capacitor; C3, third capacitor; D1, first diode; D2, second diode. Detailed Implementation

[0030] To make the objectives, technical solutions, and effects of this utility model clearer and more explicit, the present utility model will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0031] In the implementation methods and claims, unless otherwise specified in the text, the terms "a," "an," "the," and "the" may also include plural forms. If the embodiments of this utility model involve descriptions of "first," "second," etc., such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0032] It should be further understood that the term "comprising" as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when an element is referred to as "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements present. Furthermore, "connected" or "coupled" as used herein can include wireless connections or wireless coupling. The term "and / or" as used herein includes all or any unit and all combinations of one or more associated listed items.

[0033] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0034] Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0035] MOSFETs are now used as rectifier devices in rectifier circuits. Compared to diodes, MOSFETs have advantages such as low on-resistance, fast switching, and higher current carrying capacity. In switching power supplies, MOSFETs are often used for synchronous rectification. However, during operation, when a MOSFET switches from the on state to the off state, the change in current causes a momentary increase in the voltage between the drain and source, generating a reverse voltage peak, which affects the stability of the circuit.

[0036] Current rectifier circuits typically incorporate an RC snubber circuit across the MOSFET to absorb reverse voltage spikes generated during MOSFET operation. However, to ensure effective absorption, the RC constant of the snubber circuit needs to be relatively large, which increases energy loss. This is because a larger RC constant extends the capacitor's charging and discharging time, allowing for more efficient absorption and storage of voltage spike energy. This means the capacitor has more time to charge when a voltage spike occurs, reducing its amplitude and protecting the rectifier and other components. However, a larger resistance also leads to increased heat generation during capacitor charging and discharging, further increasing energy loss. Furthermore, a higher resistance results in increased power dissipation when current flows.

[0037] To solve the above problems, this utility model proposes a flyback synchronous rectifier circuit.

[0038] Reference Figure 1 In one embodiment, the flyback synchronous rectifier circuit includes:

[0039] Transformer T1;

[0040] Voltage output terminal OUT;

[0041] The rectifier circuit 10 is connected to the output winding of the transformer T1 and also to the voltage output terminal OUT. The rectifier circuit 10 is used to rectify the output current of the output winding of the transformer T1 and output it through the voltage output terminal OUT.

[0042] The RCD absorption circuit 20 is connected in series between the rectifier circuit 10 and the voltage output terminal OUT. The RCD absorption circuit 20 is connected in parallel with the output winding of the transformer T1. The RCD absorption circuit 20 is used to absorb the reverse peak voltage generated when the rectifier circuit 10 is working.

[0043] In this embodiment, the voltage output terminal OUT can include a positive output terminal and a negative output terminal, corresponding to the two ends of the output winding of transformer T1. The rectifier circuit 10 can be constructed using MOSFETs. The on-resistance of a MOSFET is typically much lower than the forward voltage drop of a diode, resulting in lower power consumption in the on-state and improved overall efficiency. Furthermore, MOSFETs have very fast switching speeds, making them suitable for high-frequency applications. MOSFETs have no reverse recovery losses when turned off, making them more efficient in high-frequency applications and reducing switching losses. Additionally, MOSFETs can withstand higher currents and voltages, making them suitable for high-power applications. In the synchronous rectifier circuit 10, by combining the MOSFETs with the control circuit, higher efficiency can be achieved during rectification, especially at low output voltages. The RCD snubber circuit 20 can be composed of a resistor, a capacitor, and a diode. The resistor limits the current, preventing excessive current from the capacitor during discharge and protecting other components in the circuit. The capacitor absorbs voltage spikes, stores energy, and releases it when the voltage drops, thus smoothing the voltage waveform. The diode provides a path for current to flow when the inductor generates a reverse electromotive force, preventing voltage spikes from damaging the switching elements. The diode is typically connected in reverse so that it does not conduct during normal operation. Connecting the RCD snubber circuit 20 in parallel with the output winding of transformer T1 provides good absorption of reverse voltage spikes with low losses. The diode in the RCD circuit can conduct quickly, rapidly responding to reverse voltage spikes. When a reverse voltage occurs, the diode immediately conducts, guiding the spike voltage to the capacitor, effectively absorbing the spike and preventing damage to the rectifier and other components. The capacitor in the RCD circuit acts as an energy storage device, rapidly charging and storing energy when a reverse voltage spike occurs, thus reducing the amplitude of the voltage spike. The charging and discharging characteristics of a capacitor allow it to smooth voltage changes and reduce the impact on the circuit. The diodes in an RCD circuit only allow current to flow in one direction, effectively preventing reverse voltage from damaging the rectifier tube. Simultaneously, they provide a low-impedance path to quickly absorb voltage spikes when reverse voltage occurs. Therefore, under normal operating conditions, the diodes in an RCD circuit only conduct when reverse voltage spikes occur, resulting in relatively low power consumption for most of the time. Energy loss only occurs when voltage spikes appear.

[0044] This utility model's technical solution uses a transformer T1, a voltage output terminal OUT, a rectifier circuit 10, and an RCD snubber circuit 20 to form a flyback synchronous rectifier circuit. The rectifier circuit 10 is connected to the output winding of the transformer T1 and also to the voltage output terminal OUT. The rectifier circuit 10 rectifies the output current of the transformer T1's output winding and outputs it through the voltage output terminal OUT. The RCD snubber circuit 20 is connected in series between the rectifier circuit 10 and the voltage output terminal OUT, and is also connected in parallel with the output winding of the transformer T1. The RCD snubber circuit 20 absorbs the reverse peak voltage generated when the rectifier circuit 10 is operating. Thus, by setting the RCD snubber circuit 20, a good absorption effect on reverse peak voltage can be achieved while maintaining low energy loss.

[0045] In one embodiment, the rectifier circuit 10 includes:

[0046] The positive terminal rectifier circuit is connected to the output winding of the transformer T1 and also to the voltage output terminal OUT. The positive terminal rectifier circuit is used to rectify the positive half-cycle AC power output from the output winding of the transformer T1 and output it through the voltage output terminal OUT.

[0047] The negative-end rectifier circuit is connected to the output winding of the transformer T1 and also to the voltage output terminal OUT. The negative-end rectifier circuit is used to rectify the negative half-cycle AC power output from the output winding of the transformer T1 and output it through the voltage output terminal OUT.

[0048] In this embodiment, the rectifier circuit 10 includes a positive-side rectifier circuit and a negative-side rectifier circuit. The positive-side rectifier circuit converts the positive half-cycle of the alternating current into direct current, and the negative-side rectifier circuit converts the negative half-cycle of the alternating current into direct current, thus forming a full-wave rectifier circuit 10. The combination of the positive-side and negative-side rectifier circuits allows for more flexible power supply design, meeting the power requirements of different circuits and is suitable for some electronic devices or circuits that require positive and negative power supplies. This design can provide a more stable DC power supply, meeting specific electrical requirements.

[0049] Reference Figures 2 to 3 In one embodiment, the positive terminal rectifier circuit includes a first MOSFET Q1, the gate of which is connected to an external controller, the source of which is connected to the output winding of the transformer T1, and the drain of which is connected to the voltage output terminal OUT; the negative terminal rectifier circuit includes a second MOSFET Q2, the gate of which is connected to an external controller, the source of which is connected to the voltage output terminal OUT, and the drain of which is connected to the output winding of the transformer T1.

[0050] In this embodiment, the positive terminal rectifier circuit can be composed of the first MOS transistor Q1, and the negative terminal rectifier circuit can be composed of the second MOS transistor Q2. In this embodiment, NMOS transistors can be used, or PMOS transistors can be selected according to the actual situation and user needs. Figure 4 This is a schematic diagram of the reverse peak voltage waveform generated by the first MOSFET Q1 and the second MOSFET Q2, where AB represents the reverse peak voltage. In the working state, the capacitor in the RCD absorption circuit 20 is charged, the diode is forward biased and conducts, and a current loop is generated, which can reduce the voltage peak.

[0051] In one embodiment, the RCD snubber circuit 20 includes a positive-terminal snubber circuit and a negative-terminal snubber circuit. The positive-terminal snubber circuit is connected in series between the positive-terminal rectifier circuit and the voltage output terminal OUT, and the positive-terminal snubber circuit is connected in parallel with the output winding of the transformer T1. The negative-terminal snubber circuit is connected in series between the negative-terminal rectifier circuit and the voltage output terminal OUT, and the negative-terminal snubber circuit is connected in parallel with the output winding of the transformer T1.

[0052] In this embodiment, the RCD absorption circuit 20 can be divided into a positive absorption circuit and a negative absorption circuit corresponding to the positive terminal rectifier circuit and the negative terminal rectifier circuit. In this way, the positive terminal absorption circuit can absorb the reverse peak voltage generated when the first MOS transistor Q1 in the positive terminal rectifier circuit is working, and the negative terminal absorption circuit can absorb the reverse peak voltage generated when the second MOS transistor Q2 in the negative terminal rectifier circuit is working.

[0053] Reference Figures 2 to 3 In one embodiment, the positive terminal absorption circuit includes a first resistor R1, a first capacitor C1, and a first diode D1. The first end of the first resistor R1 and the first end of the first capacitor C1 are connected to the voltage output terminal OUT. The second end of the first resistor R1 and the second end of the first capacitor C1 are connected to the anode of the first diode D1. The cathode of the first diode D1 is connected to the positive terminal rectifier circuit.

[0054] In this embodiment, the first resistor R1 in the positive terminal absorption circuit is used to limit the current and prevent the first capacitor C1 from generating excessive current during discharge, thereby protecting other components in the circuit. The first capacitor C1 is used to absorb voltage spikes, store energy, and release it when the voltage decreases, thus smoothing the voltage waveform. The first diode D1 is used to provide a path so that current can flow when the inductor generates a back electromotive force, thereby preventing voltage spikes from damaging the switching elements. The first diode D1 is usually connected in reverse so that it does not conduct during normal operation. When the current of the inductive load is cut off, the inductor generates a back electromotive force, causing the voltage to rise instantaneously. The operation of the RCD absorption circuit 20 is as follows: When the MOSFET is turned off, the current in the inductor attempts to continue flowing, generating a high voltage spike. This high voltage causes the first diode D1 to conduct, forming a closed loop, allowing current to flow through the first diode D1 to the first capacitor C1. Then the first capacitor C1 begins to charge, absorbing the energy generated by the inductor and reducing the voltage spike. The first resistor R1 can limit the magnitude of the current, preventing the first capacitor C1 from generating excessive current during discharge. Therefore, through the charging and discharging of the first capacitor C1, the RCD circuit can effectively smooth the voltage waveform and protect the switching elements.

[0055] Reference Figures 2 to 3 In one embodiment, the negative terminal absorption circuit includes a second resistor R2, a second capacitor C2, and a second diode D2. The first ends of the second resistor R2 and the second capacitor C2 are connected to the voltage output terminal OUT. The second ends of the second resistor R2 and the second capacitor C2 are connected to the cathode of the second diode D2. The anode of the second diode D2 is connected to the positive terminal rectifier circuit. The working principle of the negative terminal absorption circuit in this embodiment can refer to the working principle of the positive terminal absorption circuit described above, and will not be repeated here.

[0056] In one embodiment, the flyback synchronous rectifier circuit further includes:

[0057] The filter circuit 30 is connected in parallel with the rectifier circuit 10, and the filter circuit 30 is used to filter the output voltage of the rectifier circuit 10 before outputting it.

[0058] In this embodiment, the filter circuit 30 can filter the voltage after rectification by the rectifier circuit 10, smooth the ripple and noise in the output voltage, and ensure the stability of the output voltage signal.

[0059] Furthermore, referring to Figures 2 to 3In one embodiment, the filter circuit 30 includes a third resistor R3 and a third capacitor C3. The first end of the third resistor R3 is connected to the input end of the rectifier circuit 10, the second end of the third resistor R3 is connected to the first end of the third capacitor C3, and the second end of the third capacitor C3 is connected to the output end of the rectifier circuit 10.

[0060] In this embodiment, the filter circuit 30 consists of a third resistor R3 and a third capacitor C3. The third capacitor C3 is used to smooth the output voltage. The rectified voltage waveform is usually pulsating. The third capacitor C3 can store electrical energy and release it when the input voltage drops, thereby reducing the fluctuation of the output voltage. The third resistor R3 can be used in the circuit to limit the current, protect circuit components, or form an RC time constant with the third capacitor C3, affecting the charging and discharging speed of the voltage. When the third capacitor C3 and the third resistor R3 are connected in series, the time constant of the circuit will affect the charging and discharging process of the third capacitor C3. A larger time constant means that the third capacitor C3 charges and discharges more slowly, thus making the output voltage more stable, but the response speed is slower; a smaller time constant makes the voltage change faster, but may lead to larger output voltage fluctuations.

[0061] This utility model also proposes a switching power supply.

[0062] In one embodiment, the switching power supply includes the flyback synchronous rectifier circuit described above. It is understood that since the aforementioned flyback synchronous rectifier circuit is used in the switching power supply of this invention, the embodiments of the switching power supply of this invention include all the technical solutions of all embodiments of the aforementioned flyback synchronous rectifier circuit, and the achieved technical effects are completely identical, and will not be repeated here.

[0063] This utility model also proposes a power supply device.

[0064] In one embodiment, the power supply device includes a switching power supply as described above. It is understood that since the power supply device of this utility model uses the aforementioned switching power supply, the embodiments of the power supply device of this utility model include all the technical solutions of all the embodiments of the aforementioned switching power supply, and the achieved technical effects are exactly the same, and will not be repeated here.

[0065] It should be understood that the application of this utility model is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A flyback synchronous rectifier circuit, characterized in that, include: transformer; Voltage output terminal; A rectifier circuit is connected to the output winding of the transformer and also to the voltage output terminal. The rectifier circuit is used to rectify the output current of the output winding of the transformer and output it through the voltage output terminal. An RCD snubber circuit is connected in series between the rectifier circuit and the voltage output terminal. The RCD snubber circuit is connected in parallel with the output winding of the transformer. The RCD snubber circuit is used to absorb the reverse peak voltage generated when the rectifier circuit is working.

2. The flyback synchronous rectifier circuit as described in claim 1, characterized in that, The rectifier circuit includes: The positive terminal rectifier circuit is connected to the output winding of the transformer and also to the voltage output terminal. The positive terminal rectifier circuit is used to rectify the positive half-cycle AC power output from the output winding of the transformer and output it through the voltage output terminal. The negative-end rectifier circuit is connected to the output winding of the transformer and also to the voltage output terminal. The negative-end rectifier circuit is used to rectify the negative half-cycle AC power output from the output winding of the transformer and output it through the voltage output terminal.

3. The flyback synchronous rectifier circuit as described in claim 2, characterized in that, The positive-side rectifier circuit includes a first MOSFET, the gate of which is connected to an external controller, the source of which is connected to the output winding of the transformer, and the drain of which is connected to the voltage output terminal; the negative-side rectifier circuit includes a second MOSFET, the gate of which is connected to an external controller, the source of which is connected to the voltage output terminal, and the drain of which is connected to the output winding of the transformer.

4. The flyback synchronous rectifier circuit as described in claim 2, characterized in that, The RCD snubber circuit includes a positive-terminal snubber circuit and a negative-terminal snubber circuit. The positive-terminal snubber circuit is connected in series between the positive-terminal rectifier circuit and the voltage output terminal, and is connected in parallel with the output winding of the transformer. The negative-terminal snubber circuit is connected in series between the negative-terminal rectifier circuit and the voltage output terminal, and is connected in parallel with the output winding of the transformer.

5. The flyback synchronous rectifier circuit as described in claim 4, characterized in that, The positive terminal absorption circuit includes a first resistor, a first capacitor, and a first diode. The first end of the first resistor and the first end of the first capacitor are connected to the voltage output terminal. The second end of the first resistor and the second end of the first capacitor are connected to the anode of the first diode. The cathode of the first diode is connected to the positive terminal rectifier circuit.

6. The flyback synchronous rectifier circuit as described in claim 4, characterized in that, The negative terminal absorption circuit includes a second resistor, a second capacitor, and a second diode. The first end of the second resistor and the first end of the second capacitor are connected to the voltage output terminal. The second end of the second resistor and the second end of the second capacitor are connected to the cathode of the second diode. The anode of the second diode is connected to the positive terminal rectifier circuit.

7. The flyback synchronous rectifier circuit as described in claim 1, characterized in that, The flyback synchronous rectifier circuit also includes: A filter circuit is connected in parallel with the rectifier circuit. The filter circuit is used to filter the output voltage of the rectifier circuit before outputting it.

8. The flyback synchronous rectifier circuit as described in claim 7, characterized in that, The filter circuit includes a third resistor and a third capacitor. The first end of the third resistor is connected to the input terminal of the rectifier circuit, the second end of the third resistor is connected to the first end of the third capacitor, and the second end of the third capacitor is connected to the output terminal of the rectifier circuit.

9. A switching power supply, characterized in that, Includes the flyback synchronous rectifier circuit as described in any one of claims 1-8.

10. A power supply device, characterized in that, Including the switching power supply as described in claim 9.

Images