Flyback switching power supply

Abstract

The invention provides a flyback switching power supply, which comprises an input capacitor, a transformer, a primary side main switching tube, a diode and an energy storage unit, and is characterized in that the transformer comprises a primary side winding, a primary side auxiliary winding and a secondary side winding, and the input capacitor, the primary side winding, the primary side main switching tube and the energy storage unit are sequentially connected in series to form a loop; and the energy storage unit is connected in parallel with a branch in which the primary side auxiliary winding and the diode are connected in series. When the primary side main switching tube is switched off, the primary side auxiliary winding charges the energy storage unit, when the primary side main switching tube is switched on, the energy storage unit begins to discharge, the voltage on the energy storage unit can reflect the voltage on the primary side auxiliary winding more truly no matter the load is light or heavy, the influence of switching noise on feedback is reduced, the load adjustment rate is improved, and the service life of the energy storage unit is prolonged. And the performance of the flyback switching power supply is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a flyback switching power supply. Background Art

[0002] Flyback switching power supplies are widely used in the design of power adapters and offline battery chargers due to their advantages such as low cost and simple control. Flyback switching power supplies include a primary circuit with a primary main switch tube, a transformer, and a secondary circuit with a rectifier diode. The energy conversion from the primary circuit to the secondary circuit is achieved by controlling the on and off of the primary main switch tube, and the voltage feedback is used to adjust the working state of the primary main switch tube to achieve a regulated voltage output of the secondary circuit.

[0003] The flyback switching power supply adopts the DC primary voltage regulation solution to save optocouplers and controllable precision voltage regulator chips (usually TL431 chips), which is lower in cost, but the load regulation rate is poor. Summary of the invention

[0004] The object of the present invention is to provide a flyback switching power supply to solve the problem of poor load regulation of the existing flyback switching power supply.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a flyback switching power supply, including an input capacitor, a transformer, a primary main switch tube, a diode and an energy storage unit, the transformer includes a primary winding, a primary auxiliary winding and a secondary winding, the input capacitor, the primary winding, the primary main switch tube and the energy storage unit are connected in series in sequence to form a loop, and the energy storage unit is connected in parallel with a branch in which the primary auxiliary winding and the diode are connected in series.

[0006] Optionally, when the primary main switch tube is turned on, the energy storage unit starts to discharge; when the primary main switch tube is turned off, the primary auxiliary winding charges the energy storage unit through the diode.

[0007] Optionally, the first end of the energy storage unit is connected to the primary main switch tube and the first end of the primary auxiliary winding, the second end of the primary auxiliary winding is connected to the anode of the diode, and the cathode of the diode is connected to the second end of the energy storage unit.

[0008] Optionally, the energy storage unit includes a polarized capacitor, the negative electrode of the polarized capacitor is the first end of the energy storage unit, and the positive electrode of the polarized capacitor is the second end of the energy storage unit.

[0009] Optionally, the polarized capacitor is an electrolytic capacitor.

[0010] Optionally, a current limiting resistor is further included, wherein a first end of the current limiting resistor is connected to the primary main switch tube, and a second end of the current limiting resistor is connected to the first end of the energy storage unit.

[0011] Optionally, it also includes a voltage sampling unit and a control unit, wherein the voltage sampling unit is connected in parallel to the energy storage unit, and is used to collect the voltage on the energy storage unit and output a voltage sampling signal; the control unit is connected to the voltage sampling unit and the primary main switch tube to output a control signal according to the voltage sampling signal to control the duty cycle of the primary main switch tube.

[0012] Optionally, the voltage sampling unit includes a first resistor and a second resistor, the first end of the first resistor is connected to the control unit and the first end of the energy storage unit, the second end of the first resistor is connected to the first end of the second resistor and the control unit, and the second end of the second resistor is connected to the second end of the energy storage unit.

[0013] Optionally, the secondary winding includes a first secondary winding, and the flyback switching power supply also includes a first rectifier diode and a first output capacitor, the anode of the first rectifier diode is connected to the second end of the first secondary winding, the cathode of the first rectifier diode is connected to the first end of the first output capacitor, and the second end of the first output capacitor is connected to the first end of the first secondary winding.

[0014] Optionally, the secondary winding also includes a second secondary winding, and the flyback switching power supply also includes a second rectifier diode and a second output capacitor, the anode of the second rectifier diode is connected to the second end of the second secondary winding, the cathode of the second rectifier diode is connected to the first end of the second output capacitor, and the second end of the second output capacitor is connected to the first end of the second secondary winding.

[0015] In the flyback switching power supply provided by the present invention, an input capacitor, a transformer, a primary main switch tube, a diode and an energy storage unit are included, the transformer includes a primary winding, a primary auxiliary winding and a secondary winding, the input capacitor, the primary winding, the primary main switch tube and the energy storage unit are connected in series to form a loop in sequence, and the energy storage unit is connected in parallel with the branch in which the primary auxiliary winding and the diode are connected in series. When the primary main switch tube is turned off, the primary auxiliary winding will charge the energy storage unit, and when the primary main switch tube is turned on, the energy storage unit begins to discharge. At this time, the greater the load, the more energy the switching noise of the primary main switch tube accumulates in the energy storage unit, but the primary current in the loop is also greater, and the energy released when the energy storage unit discharges is more. Therefore, whether it is light load or heavy load, the voltage on the energy storage unit can more truly reflect the voltage on the primary auxiliary winding, thereby reducing the influence of the switching noise on the feedback, improving the load regulation rate, and further improving the performance of the flyback switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A circuit diagram of a flyback switching power supply using a DC primary voltage regulation scheme;

[0017] Figure 2 A circuit diagram of a flyback switching power supply provided in Embodiment 1 of the present invention;

[0018] Figure 3 A circuit diagram of a flyback switching power supply provided in Embodiment 2 of the present invention;

[0019] Wherein, the accompanying drawings are marked as follows:

[0020] Cin1, Cin2-input capacitor; T1, T2-transformer; Np1, Np2-primary winding; Ns1-secondary winding; Ns2-first secondary winding; Ns3-second secondary winding; Nb1, Nb2-primary auxiliary winding; Q1, Q2-primary main switch tube; D1, D2-diode, D3-first rectifier diode; D4-second rectifier diode; Cb1-energy storage capacitor; Cb2-polarized capacitor; Rcs1, Rcs2-current limiting resistor; Rfb1-first resistor; Rfb2-second resistor; 10-control unit; Co-first output capacitor; Co1-second output capacitor. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention will be described in more detail below in conjunction with the schematic diagram. The advantages and features of the present invention will become clearer based on the following description. It should be noted that the drawings are all in a very simplified form and are not in exact proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0022] Figure 1 The figure is a circuit diagram of a flyback switching power supply using a DC primary voltage regulation scheme. Figure 1 As shown, the flyback switching power supply includes an input capacitor Cin1, a transformer T1, a primary main switch tube Q1, a diode D1, an energy storage capacitor Cb1, a current limiting resistor Rcs1, a voltage sampling unit and a control unit, wherein the transformer T1 includes a primary winding Np1, a secondary winding Ns1 and a primary auxiliary winding Nb1. The input capacitor Cin1, the primary winding Np1, the primary main switch tube Q1 and the current limiting resistor Rcs1 are sequentially connected in series to form a loop, the energy storage capacitor Cb1 is connected in parallel with the branch in which the diode D1 and the primary auxiliary winding Nb1 are connected in series, and the voltage on the primary auxiliary winding Nb1 is rectified by the diode D1 to charge the energy storage capacitor Cb1. The voltage sampling unit is connected in parallel to the energy storage capacitor Cb1 to collect the voltage on the energy storage capacitor Cb1 and feed it back to the control unit. The control unit can output a control signal to the control end of the primary main switch tube Q1 according to the feedback signal of the voltage sampling unit to control the working state of the primary main switch tube Q1.

[0023] This flyback switching power supply detects the voltage on the primary auxiliary winding Nb1, and obtains the voltage on the secondary winding in proportion to the voltage on the primary auxiliary winding Nb1. When the load on the secondary side increases, the secondary voltage decreases, the voltage of the secondary winding Ns1 decreases, and the voltage on the primary auxiliary winding Nb1 also decreases along with the decrease in the secondary winding Ns1, resulting in a decrease in the voltage across the energy storage capacitor Cb1. After receiving the signal of the voltage reduction of the energy storage capacitor Cb1, the voltage sampling unit sends the signal to the control unit, and the control unit increases the peak current of the primary main switch tube Q1, the conversion energy of the transformer T1 increases, and the secondary voltage rises to achieve a stable balance. However, the noise of each switch of the primary main switch tube Q1 will accumulate on the energy storage capacitor Cb1, causing the energy storage capacitor Cb1 to generate a non-real voltage, so that the energy storage capacitor Cb1 cannot truly reflect the voltage on the primary auxiliary winding Nb1, resulting in feedback regulation deviation. The greater the load, the higher the switching frequency and the current limit point of the primary main switch tube Q1, the greater the switching noise, resulting in an increase in the voltage on the energy storage capacitor Cb1. However, the feedback reference voltage remains unchanged, so the voltage of the energy storage capacitor Cb1 is required to remain unchanged, resulting in a decrease in the voltage on the primary auxiliary winding Nb1, resulting in a decrease in the voltage on the secondary winding Ns1, resulting in a low secondary output voltage, resulting in a relatively poor load regulation (usually greater than 10%) of the existing DC primary voltage regulation solution, which in turn leads to poor performance of the flyback switching power supply.

[0024] Based on this, the present invention provides a flyback switching power supply, including an input capacitor, a transformer, a primary main switch tube, a diode and an energy storage unit, the transformer including a primary winding, a primary auxiliary winding and a secondary winding, the input capacitor, the primary winding, the primary main switch tube and the energy storage unit are sequentially connected in series to form a loop, and the energy storage unit is connected in parallel with a branch connected in series with the primary auxiliary winding and the diode. When the primary main switch tube is turned off, the primary auxiliary winding will charge the energy storage unit, and when the primary main switch tube is turned on, the energy storage unit begins to discharge. At this time, the greater the load, the more energy the switching noise of the primary main switch tube accumulates in the energy storage unit, but the primary current in the loop is also greater, and the energy released when the energy storage unit discharges is more. Therefore, whether it is light load or heavy load, the voltage on the energy storage unit can more truly reflect the voltage on the primary auxiliary winding, thereby reducing the impact of the switching noise on the feedback, improving the load regulation rate, and thus improving the performance of the flyback switching power supply.

[0025] Embodiment 1

[0026] Figure 2 The circuit diagram of the flyback switching power supply provided in this embodiment. Figure 2As shown, the flyback switching power supply includes an input capacitor Cin2, a transformer T2, a primary main switch Q2, an energy storage unit, a current limiting resistor Rcs2, a diode D2, a voltage sampling unit and a control unit 10. The transformer T2 includes a primary winding Np2, a primary auxiliary winding Nb2 and a secondary winding, wherein the secondary winding includes a first secondary winding Ns2. The primary winding Np2 and the primary auxiliary winding Nb2 are located on the primary side, and the first secondary winding Ns2 is located on the secondary side. The number of turns of the primary winding Np2, the first secondary winding Ns2 and the primary auxiliary winding Nb2 can be designed according to actual needs.

[0027] Furthermore, the input capacitor Cin2, the primary winding Np2, the primary main switch tube Q2 and the energy storage unit are sequentially connected in series to form a loop to form a primary loop. The energy storage unit is connected in parallel with the branch in which the primary auxiliary winding Nb2 and the diode D2 are connected in series. Specifically, the first end of the energy storage unit is connected to the primary main switch tube Q2 and the first end (specifically, the opposite-name end) of the primary auxiliary winding Nb2, the second end (specifically, the same-name end) of the primary auxiliary winding Nb2 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the second end of the energy storage unit.

[0028] In this embodiment, the energy storage unit includes a polar capacitor Cb2, and the polar capacitor Cb2 can be an electrolytic capacitor, the negative electrode of the polar capacitor Cb2 is the first end of the energy storage unit, and the positive electrode of the polar capacitor Cb2 is the second end of the energy storage unit. The input capacitor Cin2, the primary winding Np2, the primary main switch tube Q2, the current limiting resistor Rcs2 and the polar capacitor Cb2 are sequentially connected in series to form a loop. Specifically, the first end of the input capacitor Cin2 is connected to the first end of the primary winding Np2 (specifically, the opposite end), the second end of the primary winding Np2 (specifically, the same end) is connected to the drain of the primary main switch tube Q2, the source of the primary main switch tube Q2 is connected to the first end of the current limiting resistor Rcs2, the second end of the current limiting resistor Rcs2 is connected to the negative electrode of the polar capacitor Cb2, and the positive electrode of the polar capacitor Cb2 is connected to the second end of the input capacitor Cin2. In this way, when the primary main switch tube Q2 is turned on, the primary winding Np2 starts to store energy, and the primary current flows from the negative electrode of the polarized capacitor Cb2 to the positive electrode of the polarized capacitor Cb2 after passing through the primary main switch tube Q2. Therefore, the polarized capacitor Cb2 starts to discharge and release energy.

[0029] Optionally, the capacity of the polar capacitor Cb2 may be greater than or equal to 220 μF to withstand the energy of the primary auxiliary winding Nb2, but it should not be limited thereto. The capacity of the polar capacitor Cb2 may be selected according to the size of the primary current.

[0030] The current limiting resistor Rcs2 can limit the primary current to prevent the primary main switch tube Q2 from being broken down due to excessive primary current. In some embodiments, the current limiting resistor Rcs2 can also be omitted. At this time, the source of the primary main switch tube Q2 is directly connected to the negative electrode of the polarity capacitor Cb2.

[0031] Furthermore, in this embodiment, the negative electrode of the polarized capacitor Cb2 is also connected to the first end of the primary auxiliary winding Nb2, the second end of the primary auxiliary winding Nb2 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the positive electrode of the polarized capacitor Cb2. In this way, when the primary main switch tube Q2 is turned off, the primary winding Np2 transfers energy to the first secondary winding Ns2, and the voltage on the primary auxiliary winding Nb2 can be rectified by the diode D2 to charge the polarized capacitor Cb2.

[0032] In some embodiments, the position of the diode D2 can be changed, for example, the negative electrode of the polar capacitor Cb2 can be connected to the anode of the diode D2, the cathode of the diode D2 is connected to the first end of the primary auxiliary winding Nb2, and the second end of the primary auxiliary winding Nb2 is connected to the positive electrode of the energy storage unit Cb2. In this way, the diode D2 can also rectify the voltage on the primary auxiliary winding Nb2.

[0033] Further, the voltage sampling unit is connected in parallel to the polarized capacitor Cb2, and is used to collect the voltage on the polarized capacitor Cb2 and output a voltage sampling signal to the control unit 10. In the present embodiment, the voltage sampling unit is a resistor voltage divider circuit, which includes a first resistor Rfb1 and a second resistor Rfb2, and the first resistor Rfb1 and the second resistor Rfb2 are connected in series and then connected in parallel to the polarized capacitor Cb2, and are used to divide the voltage on the polarized capacitor Cb2. Specifically, the first end of the first resistor Rfb1 is connected to the control unit 10 and the negative electrode of the polarized capacitor Cb2, the second end of the first resistor Rfb1 is connected to the first end of the second resistor Rfb2 and the control unit 10, and the second end of the second resistor Rfb2 is connected to the positive electrode of the polarized capacitor Cb2.

[0034] Of course, the resistor voltage divider circuit is only a preferred example of the voltage sampling unit, and those skilled in the art can reasonably design the structure of the voltage sampling unit according to actual conditions.

[0035] The control unit 10 is connected to the voltage sampling unit and the primary main switch tube Q2 to output a control signal for controlling the duty cycle of the primary main switch tube Q2 according to the voltage sampling signal. Specifically, the control unit 10 is also connected to the gate of the primary main switch tube Q2 to output a control signal to the primary main switch tube Q2.

[0036] Please continue reading Figure 2In this embodiment, the flyback switching power supply further includes a first rectifier diode D3 and a first output capacitor Co. The anode of the first rectifier diode D3 is connected to the second end (specifically, the same-name end) of the first secondary winding Ns2, the cathode of the first rectifier diode D3 is connected to the first end of the first output capacitor Co, and the second end of the first output capacitor Co is connected to the first end (specifically, the opposite-name end) of the first secondary winding Ns2. The first rectifier diode D3 and the first output capacitor Co are respectively used to rectify and filter the voltage on the first secondary winding Ns2, thereby obtaining the output voltage of the flyback switching power supply.

[0037] In this embodiment, the flyback switching power supply has a single-channel output structure, but the present invention should not be limited thereto.

[0038] It should be understood that in the flyback switching power supply in this embodiment, when the primary main switch tube Q2 is turned off, the primary auxiliary winding Nb2 will charge the polar capacitor Cb2. When the primary main switch tube Q2 is turned on, the polar capacitor Cb2 starts to discharge. At this time, the greater the load, the higher the switching frequency of the primary main switch tube Q2, and the more energy the switching noise of the primary main switch tube Q2 accumulates on the polar capacitor Cb2, but the primary current in the loop is also greater, and the polar capacitor Cb2 releases more energy when discharging. Therefore, whether it is light load or heavy load, the voltage on the polar capacitor Cb2 can more truly reflect the voltage on the primary auxiliary winding Nb2, and the voltage sampling signal is more accurate, thereby reducing the influence of switching noise on feedback, improving load regulation, and further improving the performance of the flyback switching power supply.

[0039] Next, the flyback switching power supply in this embodiment will be further proved through experiments to have a good load regulation rate. Table 1 shows Figure 1 Table 2 shows the load regulation rate of the flyback switching power supply in this embodiment. By comparing Table 1 and Table 2, it can be seen that when the input current of the load is in the range of 0-0.65A and 5mA-0.65A, and the input voltage is between 85V-265V (normal input voltage), the load regulation rate of the flyback switching power supply in this embodiment is higher than that of Figure 1 The load regulation rate of the flyback switching power supply is greatly improved.

[0040] Table 1: Figure 1 Load regulation of flyback switching power supply

[0041]

[0042] Table 2: Load regulation of the flyback switching power supply in this embodiment

[0043]

[0044]

[0045] Embodiment 2

[0046] Figure 3 This is a current diagram of the flyback switching power supply provided in this embodiment. Figure 3 As shown, the difference from the first embodiment is that in this embodiment, the flyback switching power supply has a multi-channel output structure.

[0047] Specifically, in this embodiment, the secondary winding also includes a second secondary winding Ns3, and the flyback switching power supply also includes a second rectifier diode D4 and a second output capacitor Co1. Among them, the anode of the second rectifier diode D4 is connected to the second end (specifically, the same-name end) of the second secondary winding Ns3, the cathode of the second rectifier diode D4 is connected to the first end of the second output capacitor Co1, and the second end Co1 of the second output capacitor is connected to the first end (specifically, the opposite-name end) of the second secondary winding Ns3. The second rectifier diode D4 and the second output capacitor Co1 are respectively used to rectify and filter the voltage on the second secondary winding Ns3. At this time, the flyback switching power supply can output two voltages.

[0048] It should be understood that the flyback switching power supply is not limited to outputting two voltages, but can also output three or more voltages. In this case, the flyback switching power supply needs to adaptively increase the number of secondary windings, rectifier diodes and output capacitors, which will not be explained one by one here.

[0049] In summary, the flyback switching power supply provided in the embodiment of the present invention includes an input capacitor, a transformer, a primary main switch tube, a diode and an energy storage unit. The transformer includes a primary winding, a primary auxiliary winding and a secondary winding. The input capacitor, the primary winding, the primary main switch tube and the energy storage unit are connected in series to form a loop in sequence. The energy storage unit is connected in parallel with the branch in which the primary auxiliary winding and the diode are connected in series. When the primary main switch tube is turned off, the primary auxiliary winding will charge the energy storage unit. When the primary main switch tube is turned on, the energy storage unit begins to discharge. At this time, the greater the load, the more energy the switching noise of the primary main switch tube accumulates in the energy storage unit, but the primary current in the loop is also greater, and the energy released when the energy storage unit discharges is more. Therefore, whether it is light load or heavy load, the voltage on the energy storage unit can more truly reflect the voltage on the primary auxiliary winding, thereby reducing the influence of the switching noise on the feedback, improving the load regulation rate, and thus improving the performance of the flyback switching power supply.

[0050] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0051] It should also be noted that, although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

[0052] It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are merely used to distinguish between the various components, elements, steps, etc. in the specification, and are not used to indicate the logical relationship or sequential relationship between the various components, elements, steps, etc.

[0053] It should also be recognized that the terms described herein are only used to describe specific embodiments and are not intended to limit the scope of the invention. It should be noted that the singular forms "a" and "an" used herein and in the appended claims include plural references unless the context clearly indicates otherwise. For example, a reference to "a step" or "a device" means a reference to one or more steps or devices, and may include secondary steps and secondary devices. All conjunctions used should be understood in the broadest sense. And, the word "or" should be understood to have the definition of a logical "or", rather than a logical "exclusive or", unless the context clearly indicates otherwise. In addition, the implementation of the method and / or device in the embodiments of the present invention may include performing the selected task manually, automatically, or in combination.

Claims

1. A flyback switching power supply, It is characterized in that It includes an input capacitor, a transformer, a primary main switch tube, a diode and an energy storage unit. The transformer includes a primary winding, a primary auxiliary winding and a secondary winding. The input capacitor, the primary winding, the primary main switch tube and the energy storage unit are connected in series to form a loop. The energy storage unit is connected in parallel with a branch in which the primary auxiliary winding and the diode are connected in series.

2. The flyback switching power supply according to claim 1, It is characterized in that When the primary main switch is turned on, the energy storage unit starts to discharge; when the primary main switch is turned off, the primary auxiliary winding charges the energy storage unit through the diode.

3. The flyback switching power supply according to claim 1, It is characterized in that The first end of the energy storage unit is connected to the primary main switch tube and the first end of the primary auxiliary winding, the second end of the primary auxiliary winding is connected to the anode of the diode, and the cathode of the diode is connected to the second end of the energy storage unit.

4. The flyback switching power supply according to claim 3, It is characterized in that The energy storage unit includes a polar capacitor, the negative electrode of the polar capacitor is the first end of the energy storage unit, and the positive electrode of the polar capacitor is the second end of the energy storage unit.

5. The flyback switching power supply according to claim 4, It is characterized in that The polarized capacitor is an electrolytic capacitor.

6. The flyback switching power supply according to any one of claims 3 to 5, It is characterized in that It also includes a current limiting resistor, a first end of which is connected to the primary main switch tube, and a second end of which is connected to the first end of the energy storage unit.

7. The flyback switching power supply according to any one of claims 3 to 5, It is characterized in that It also includes a voltage sampling unit and a control unit. The voltage sampling unit is connected in parallel to the energy storage unit and is used to collect the voltage on the energy storage unit and output a voltage sampling signal; the control unit is connected to the voltage sampling unit and the primary main switch tube to output a control signal according to the voltage sampling signal to control the duty cycle of the primary main switch tube.

8. The flyback switching power supply according to claim 7, It is characterized in that The voltage sampling unit includes a first resistor and a second resistor, the first end of the first resistor is connected to the control unit and the first end of the energy storage unit, the second end of the first resistor is connected to the first end of the second resistor and the control unit, and the second end of the second resistor is connected to the second end of the energy storage unit.

9. The flyback switching power supply according to any one of claims 1 to 5, It is characterized in that The secondary winding includes a first secondary winding, and the flyback switching power supply also includes a first rectifier diode and a first output capacitor, the anode of the first rectifier diode is connected to the second end of the first secondary winding, the cathode of the first rectifier diode is connected to the first end of the first output capacitor, and the second end of the first output capacitor is connected to the first end of the first secondary winding.

10. The flyback switching power supply according to any one of claims 9, It is characterized in that The secondary winding also includes a second secondary winding, and the flyback switching power supply also includes a second rectifier diode and a second output capacitor, the anode of the second rectifier diode is connected to the second end of the second secondary winding, the cathode of the second rectifier diode is connected to the first end of the second output capacitor, and the second end of the second output capacitor is connected to the first end of the second secondary winding.

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