Switching power supply circuit and electrical equipment

Abstract

The invention discloses a switching power supply circuit and electrical equipment, and belongs to the field of switching power supplies. According to the switching power supply circuit, when the first switching tube is switched off, the primary winding of the transformer discharges to charge the second polar capacitor, so that when the first switching tube is switched on, the primary winding of the transformer is charged, and the current path is finally grounded from the negative electrode of the second polar capacitor to the positive electrode of the second polar capacitor. Therefore, when the switching power supply is switched on, the second polar capacitor can be rapidly discharged, and when the traditional switching power supply is switched on, the second polar capacitor is charged. Therefore, according to the scheme, additional discharging is not needed, the discharging speed is high, feedback is fast, an optocoupler is not needed, and cost is low.

Description

Technical Field

[0001] The present application relates to the technical field of switching power supplies, and in particular, to a switching power supply circuit and electrical equipment. Background Art

[0002] As an important guarantee for the normal operation of all loads in the system, the switching power supply must not only be able to provide voltage to the load continuously and stably, but also ensure the safety of primary and secondary isolation, while also being as space-saving and cost-effective as possible.

[0003] In order to achieve precise control, a feedback switching power supply is generally used. The traditional feedback switching tube power supply adopts a secondary-side optocoupler isolated feedback switching power supply. However, in order to achieve strong and weak electrical isolation between the primary and secondary, an optocoupler is required, which is costly and occupies a large space. The AC isolated feedback switching power supply on the primary side has a slow discharge and cannot provide timely feedback, resulting in inaccurate control. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present application provides a switching power supply circuit and electrical equipment to solve the problem that the existing isolated switching power supplies are either high in cost or discharge slowly and cannot provide timely feedback, resulting in inaccurate control.

[0005] The technical solution adopted by this application to solve its technical problem is:

[0006] In a first aspect, a switching power supply circuit is provided, comprising: a transformer and a first switching tube;

[0007] The transformer comprises a primary winding, a secondary winding and an auxiliary winding;

[0008] The first pin of the auxiliary winding is connected to the VCC pin of the chip inside the first switch tube; the first pin of the auxiliary winding is also connected to the first pin of the first switch tube through a reverse-connected transient suppression diode, and the first pin of the auxiliary winding is grounded; the first pin of the auxiliary winding is connected to the second pin of the first switch tube through a second polarity capacitor;

[0009] The second pin of the auxiliary winding is connected to the second pin of the first switch tube via a reversely connected third diode;

[0010] The first pin of the first switch tube is connected to the second pin of the first switch tube through a fifth resistor; the third pin of the first switch tube is connected to the feedback pin of the internal chip through a third resistor; the second pin of the first switch tube is connected to the first preset pin of the internal chip;

[0011] The second preset pin of the internal chip is directly connected to the fourth pin of the primary winding; the second preset pin of the internal chip is connected to the fifth pin of the primary winding through a second diode and a filter circuit.

[0012] Furthermore, the filtering circuit includes a first resistor and a first capacitor connected in parallel.

[0013] Furthermore, the first pin of the auxiliary winding is connected to the VCC pin of the internal chip of the first switch tube through a second resistor.

[0014] Furthermore, the first pin of the auxiliary winding is connected to the first pin of the first switch tube through a fourth resistor and a reverse-connected transient voltage suppressor diode.

[0015] Furthermore, one leg of the secondary winding is grounded, and the other leg is positively connected to a fourth diode. A third polarity capacitor is connected between two legs of the primary winding, and a fourth capacitor is connected in parallel at both ends of the third polarity capacitor.

[0016] In a second aspect, a switching power supply circuit is provided, comprising: a transformer and a first switching tube;

[0017] The transformer comprises a primary winding, a secondary winding and an auxiliary winding;

[0018] The first pin of the auxiliary winding is connected to the VCC pin of the chip inside the first switch tube; the first pin of the auxiliary winding is also connected to the first pin of the first switch tube through a reverse-connected transient suppression diode, and the first pin of the auxiliary winding is grounded through a first switch; the first pin of the auxiliary winding is connected to the second pin of the first switch tube through a second polarity capacitor and a second switch;

[0019] The second pin of the auxiliary winding is connected to the second pin of the first switch tube via a reversely connected third diode and the second switch;

[0020] A third switch is provided between the second polarity capacitor and the second switch, the third switch is located between the three diodes and the second switch, and the third switch is grounded;

[0021] The first pin of the first switch tube is connected to the second pin of the first switch tube through a fifth resistor; the third pin of the first switch tube is connected to the feedback pin of the internal chip through a third resistor; the second pin of the first switch tube is connected to the first preset pin of the internal chip;

[0022] The second preset pin of the internal chip is directly connected to the fourth pin of the primary winding; the second preset pin of the internal chip is connected to the fifth pin of the primary winding through a second diode and a filter circuit.

[0023] Furthermore, the filtering circuit includes a first resistor and a first capacitor connected in parallel.

[0024] Furthermore, the first pin of the auxiliary winding is connected to the VCC pin of the internal chip of the first switch tube through a second resistor.

[0025] Furthermore, the first pin of the auxiliary winding is connected to the first pin of the first switch tube through a fourth resistor and a reverse-connected transient voltage suppressor diode.

[0026] Furthermore, one leg of the secondary winding is grounded, and the other leg is positively connected to a fourth diode. A third polarity capacitor is connected between two legs of the primary winding, and a fourth capacitor is connected in parallel at both ends of the third polarity capacitor.

[0027] Furthermore, the first switch and / or the third switch adopts an optical coupler, and the second switch adopts a second switch tube.

[0028] In a third aspect, an electrical device is provided, comprising: a switching power supply circuit provided by any technical solution of the first aspect or the second aspect

[0029] Beneficial effects:

[0030] The technical solution of the present application provides a switching power supply circuit and electrical equipment. When the first switch tube is turned off, the primary winding of the transformer discharges and charges the second polarity capacitor. In this way, when the first switch tube is turned on, the primary winding of the transformer is charged. Since the current path at this time is from the negative pole of the second polarity capacitor to the positive pole of the second polarity capacitor, it is finally grounded. Therefore, the second polarity capacitor is discharging at this time, so when the switching power supply is turned on, the second polarity capacitor can be discharged quickly, while when the traditional switching power supply is turned on, the second polarity capacitor is charged. Therefore, the present application does not need to be discharged separately, the discharge speed is fast, the feedback is fast, and no optical coupling is required, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 This is a circuit diagram of an SSR secondary side optocoupler isolated feedback switching power supply provided in an embodiment of the present application;

[0033] Figure 2 This is a PSR primary side AC isolated feedback switching power supply circuit structure diagram provided in an embodiment of the present application;

[0034] Figure 3 This is a PSR primary side DC isolated feedback switching power supply circuit structure diagram provided in an embodiment of the present application;

[0035] Figure 4 This is a structural diagram of a switching power supply circuit provided in an embodiment of the present application;

[0036] Figure 5 This is a schematic diagram of a circuit path when a first MOS tube in a switching power supply circuit provided by an embodiment of the present application is turned on;

[0037] Figure 6 This is a schematic diagram of a circuit path when a first MOS tube of a switching power supply circuit is turned off, provided in an embodiment of the present application;

[0038] Figure 7 The embodiment of this application provides Figure 3 Schematic diagram of the noise path of the switching power supply circuit shown;

[0039] Figure 8 The embodiment of this application provides Figure 4 Schematic diagram of the noise path of the switching power supply circuit shown;

[0040] Fig. 9 This is another schematic diagram of the structure of a switching power supply circuit provided in an embodiment of the present application;

[0041] Fig.10 The embodiment of this application provides Fig. 9 The control logic diagram of the switching power supply circuit shown; Description of the drawings:

[0043] L3-transformer; Q1-first MOS tube, C1-first capacitor, C2-second polarity capacitor, C3-third polarity capacitor, C4-fourth capacitor, D1-transient suppression diode, D2-second diode, D3-third diode, D4-fourth diode, R1-first resistor, R2-second resistor, R3-third resistor, R4-fourth resistor, R5-fifth resistor, R6-sixth resistor, U1-internal chip, U9-first optocoupler; U2-second optocoupler, Q4-second MOS tube. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application is described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other implementation methods obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0045] There are various problems with the feedback switching power supply in the prior art.

[0046] Traditional SSR secondary side optocoupler isolated feedback switching power supply such as Figure 1 As shown in the figure, the mainstream switching power supply on the market is the primary-secondary optocoupler feedback switching power supply solution. Although this solution is stable and reliable, it uses optocouplers for isolation between strong and weak electricity, and TL431 or Zener diodes as feedback. This solution uses optocouplers for isolation, and the cost is not optimal; and it occupies a large layout space.

[0047] Traditional PSR primary side AC isolated feedback switching power supply such as Figure 2 As shown in the figure, there are primary-side AC isolated power supply solutions currently available on the market; 1. AC detection is to detect the transformer winding voltage, which takes a long time to detect; during the detection, the corresponding detection winding platform voltage cannot fluctuate. If there is oscillation, the detection will be inaccurate and the output will be unstable (the process requirements for the transformer are extremely high); 2. Common-mode noise is easily coupled to the winding, and the motor or group pulses are easily coupled to the internal winding of the transformer, resulting in interference with the detection and inability to stabilize the output voltage; 3. Due to the limitation of the detection time, the switching frequency cannot be increased, and the transformer needs to be larger in size to meet the same power requirements.

[0048] Traditional PSR primary side DC isolated feedback switching power supply such as Figure 3 As shown in the figure, the primary-side DC isolated power supply solutions currently on the market have the following problems: 1. The main problem is poor dynamic load adjustment. When the switching power supply is turned on, the capacitor C2 is charged. When it is turned off, the capacitor C2 voltage discharges slowly, resulting in slow feedback, which causes the secondary voltage to be low under heavy load and large dynamic ripple; 2. It is easily affected by the parasitic capacitance of the feedback winding. Noise can charge the capacitor C2 voltage high, resulting in low voltage when the secondary is fully loaded, and the capacitor C2 cannot feedback the real voltage in time.

[0049] To solve this problem, the present application provides a primary-side DC isolated switching power supply circuit, which discharges the second polarity capacitor when the switching power supply is turned on. The first switching tube is a MOS tube as an example for explanation. It can be understood that the first switching tube can also use a switching tube such as an IGBT. The specific pins and the specific names of the internal chips are only explained by taking the MOS tube as an example. When other switching tubes such as IGBT are used, they can be adjusted according to the same principle.

[0050] Embodiment 1:

[0051] Reference Figure 4 , the embodiment of the present application provides a switching power supply circuit, including: a transformer L3 and a first MOS tube Q1;

[0052] The transformer L3 includes a primary winding (i.e. Figure 4 The transformer has windings marked with 4 and 5, where the pin 4 is the fourth pin and the pin 5 is the fifth pin), the secondary winding (i.e. Figure 4 The transformer windings marked with 7 and 10 and the auxiliary winding (i.e. Figure 4 The windings of the transformer are marked with 1 and 2, where the pin where 1 is located is the first pin and the pin where 2 is located is the second pin);

[0053] The first pin of the auxiliary winding is connected to the VCC pin of the chip U1 inside the first MOS tube Q1; the first pin of the auxiliary winding is also connected to the first pin, i.e., the gate, of the first MOS tube Q1 through a reversely connected transient suppression diode D1, and the first pin of the auxiliary winding is grounded; the first pin of the auxiliary winding is connected to the second pin, i.e., the source, of the first MOS tube Q1 through a second polarity capacitor C2;

[0054] The second pin of the auxiliary winding is connected to the second pin, i.e., the source, of the first MOS transistor Q1 through a reversely connected third diode D3;

[0055] The gate of the first MOS tube Q1 is connected to the source of the first MOS tube Q1 through the fifth resistor R5; the third pin, i.e., the drain, of the first MOS tube Q1 is connected to the feedback pin, i.e., the FB pin, of the internal chip U1 through the third resistor R3; the source of the first MOS tube Q1 is connected to the first preset pin, i.e., the S pin, of the internal chip U1;

[0056] The second preset pin of the internal chip U1, namely the DRAIN pin, is directly connected to the fourth pin of the primary winding; the second preset pin of the internal chip U1, namely the DRAIN pin, is connected to the fifth pin of the primary winding through the second diode D2 and the filter circuit.

[0057] One leg of the secondary winding is grounded, and the other leg is positively connected to a fourth diode D4. A third polarity capacitor C3 is connected between the two legs of the primary winding, and a fourth capacitor C4 is connected in parallel at both ends of the third polarity capacitor C3.

[0058] Preferably, the filter circuit comprises a first resistor R1 connected in parallel and a first capacitor C1 connected in parallel. The first resistor R1 connected in parallel and the first capacitor C1 connected in parallel form an RC filter circuit.

[0059] As a preferred implementation of the embodiment of the present application, the first pin of the auxiliary winding is connected to the VCC pin of the internal chip U1 of the first MOS tube Q1 through the second resistor R2.

[0060] Optionally, the first pin of the auxiliary winding is connected to the gate of the first MOS transistor Q1 via a fourth resistor R4 and a reverse-connected transient voltage suppressor diode D1.

[0061] Here’s how it works:

[0062] ① Such as Figure 4 As shown, when the first MOS tube in the switching power supply circuit is turned on, the primary winding voltage is positive at the top (transformer pin 5) and negative at the bottom (transformer pin 4). At this time, the primary side of the transformer is charged to store energy. Due to the unidirectional conduction characteristics of the D3 and D4 diodes, the auxiliary winding (pins 1, 2) and the secondary winding (pins 7, 10) are not conducting.

[0063] ②When the first MOS tube of the switching power supply is turned off (such as Figure 6 As shown), due to the characteristics of the transformer, the primary winding voltage is negative at the top and positive at the bottom. At this time, the primary winding of the transformer is discharged. At this time, the auxiliary winding induction current flows from transformer pin 1 → C2 capacitor positive electrode → C2 capacitor negative electrode → diode D3 rectification → transformer pin 2, charging capacitor C2 and synchronously supplying power to the VCC pin of the internal chip;

[0064] ③When the switching power MOS tube is turned on (such as Figure 5 As shown), the primary winding of the transformer is charged, and the alternating current is rectified through the transformer pin 5 → transformer pin 4 → U1 pin 4 (i.e. S pin, connected to the source of the first MOS tube) → U1 pin S → the negative electrode of the C2 capacitor → the positive electrode of the C2 capacitor → GND; and because the path is from the negative electrode of the C2 capacitor → the positive electrode of the C2 capacitor → GND, the discharge of the C2 capacitor can be accelerated at this time, and when the MOS tube is turned off, the energy of the C2 capacitor will be consumed more quickly, so that the VCC pin and GND voltage of U1 will drop, thereby accelerating the auxiliary winding main feedback. Then the secondary can replenish energy in time and stabilize the output; and the previous traditional DC feedback such as Figure 3 As shown, this is because when the switching power supply is turned on, C2 is charged, and when it is turned off, the C2 voltage discharges slowly, so the feedback terminal voltage is high, resulting in slow feedback, which leads to low secondary voltage and large dynamic ripple when overloaded.

[0065] ④ The circuit of the present application utilizes the characteristics of the circuit flow direction and the reverse discharge of the capacitor, and can make timely adjustments according to the load changes when the load changes; because when the load becomes larger, the energy consumption is high, and the current limit point of the first MOS tube conduction will increase accordingly. At this time, the corresponding discharge energy of C2 will also increase relatively, and the feedback voltage will also decrease. After the feedback voltage decreases, the feedback is accelerated, so that the secondary load end can replenish energy in time and stabilize the voltage output.

[0066] After the change, under dynamic load conditions, the output voltage ripple is small and the output voltage is stable; Figure 3 The output voltage of the circuit shown in the figure under dynamic load has a ripple data of about 1000mA in actual testing. Figure 4The output voltage of the circuit shown under dynamic load has a ripple data of about 160mA during actual testing.

[0067] ⑤ When the MOS tube is turned off, the auxiliary winding is connected from transformer pin 1 → capacitor C2 positive pole → capacitor C2 negative pole → transformer pin 2; for the reverse connection of the auxiliary winding D3 diode at this time, transformer pin 1 is negative voltage, and transformer pin 2 is positive voltage after the diode is turned on; and the interference noise of the primary winding needs to follow the principle of high voltage flowing to low voltage; at this time, since the auxiliary winding voltage is the lowest, the noise of the primary winding flows to the auxiliary winding after passing through the secondary winding, and the auxiliary winding is connected to the ground of the primary winding path, so most of the noise can be filtered out by strong electricity. Its noise path is as follows Figure 8 shown.

[0068] If D3 is positively connected, such as Figure 7 As shown, most of the noise flows to the secondary side load end and will be coupled to the load interference; after changing to reverse connection, most of the noise flows to the primary side auxiliary winding. The auxiliary winding is connected to the primary side's GND, and the noise introduced into GND disappears.

[0069] The switching power supply circuit provided in the embodiment of the present application is that when the first MOS tube is turned off, the primary winding of the transformer is discharged and the second polarity capacitor is charged, so that when the first MOS tube is turned on, the primary winding of the transformer is charged, because at this time the current path is from the negative pole of the second polarity capacitor to the positive pole of the second polarity capacitor, and finally grounded. So at this time, the second polarity capacitor is discharging, so when the switching power supply is turned on, the second polarity capacitor can be discharged quickly, and when the traditional switching power supply is turned on, the second polarity capacitor is charged. Therefore, the present application scheme does not need to be discharged separately, the discharge speed is fast, the feedback is fast, and no optical coupling is required, and the cost is low.

[0070] Taking the load as an air conditioner as an example, the air conditioner load is divided into static load and dynamic load according to whether the power changes (the load here does not refer to a fixed load, but two types of loads; for example, a stepper motor sometimes works and sometimes does not work, and the working power also changes. According to logical judgment, this type of load is a dynamic load; but if it is a load like a net ion module, it is always on when the command is on, and always off when it is off, and the power is constant, which is a static load); if the air conditioner has only a static load and the power supply voltage varies in a wide range (for example: load control relays, etc.), it is necessary to minimize the switching cycle of the switching power supply and reduce the switching loss to improve the conversion efficiency of the switching power supply; if the air conditioner has a dynamic load or the static load and dynamic load coexist, since the secondary output energy continues to change, high-response feedback is required to stabilize the voltage; then it is necessary to respond quickly to the switch according to the changes in the secondary load in time.

[0071] However, the switch power supply circuit in the first embodiment cannot achieve this effect. Based on this, the present application makes improvements on the basis of the first embodiment and proposes a circuit in the second embodiment.

[0072] Embodiment 2:

[0073] like Fig. 9 As shown, an embodiment of the present application provides a switching power supply circuit, including: a transformer L3 and a first MOS tube Q1;

[0074] The transformer L3 includes a primary winding, a secondary winding and an auxiliary winding;

[0075] The first pin of the auxiliary winding is connected to the VCC pin of the chip U1 inside the first MOS tube Q1; the first pin of the auxiliary winding is also connected to the first pin, i.e., the gate, of the first MOS tube Q1 through a reversely connected transient suppression diode D1, and the first pin of the auxiliary winding is grounded through a first switch; the first pin of the auxiliary winding is connected to the second pin, i.e., the source, of the first MOS tube Q1 through a second polarity capacitor C2 and a second switch; for example, Fig. 9 As shown, the first switch is composed of a control circuit 2 and a second optical coupler U2.

[0076] The second pin of the auxiliary winding is connected to the second pin of the first MOS transistor Q1 through a reversely connected third diode D3 and the second switch; preferably, a sixth resistor R6 is provided between the second switch and the second pin of the first MOS transistor Q1. Fig. 9 As shown, the second switch is composed of a control circuit 3 and a second MOS transistor Q4. It is understandable that other switch transistors may be used to replace the second MOS transistor in practice, such as IGBT, triode, etc.

[0077] A third switch is provided between the second polarity capacitor C2 and the second switch, the third switch is located between the three diodes and the second switch, and the third switch is grounded; illustratively, as Fig. 9 As shown, the third switch is composed of a control circuit 1 and a first optical coupler U9.

[0078] It should be noted that the specific structures of the control circuit 1, the control circuit 2 and the control circuit 3 can be set according to actual needs, and this application does not make specific restrictions. The reason why the control circuit 1 and the control circuit 2 use optical couplers is that weak electricity needs to control strong electricity. Therefore, it is understandable that the control circuit 1 and the control circuit 2 can also use relays, and the control circuit 3 does not need to isolate strong and weak electricity, so it can use MOS tubes and other switch tubes.

[0079] The first pin of the first MOS tube Q1 is connected to the second pin of the first MOS tube Q1 through the fifth resistor R5; the third pin, i.e., the drain, of the first MOS tube Q1 is connected to the feedback pin, i.e., the FB pin, of the internal chip U1 through the third resistor R3; the second pin of the first MOS tube Q1 is connected to the first preset pin, i.e., the S pin, of the internal chip U1;

[0080] The second preset pin of the internal chip U1, namely the DRAIN pin, is directly connected to the fourth pin of the primary winding; the second preset pin of the internal chip U1 is connected to the fifth pin of the primary winding through the second diode D2 and the filter circuit.

[0081] One leg of the secondary winding is grounded, and the other leg is positively connected to a fourth diode D4. A third polarity capacitor C3 is connected between the two legs of the primary winding, and a fourth capacitor C4 is connected in parallel at both ends of the third polarity capacitor C3.

[0082] Preferably, the filtering circuit includes a first resistor R1 connected in parallel and a first capacitor C1 connected in parallel.

[0083] As a preferred implementation of the embodiment of the present application, the first pin of the auxiliary winding is connected to the VCC pin of the internal chip U1 of the first MOS tube Q1 through the second resistor R2.

[0084] Furthermore, the first pin of the auxiliary winding is connected to the first pin, ie, the gate, of the first MOS transistor Q1 through a fourth resistor R4 and a reversely connected transient voltage suppressor diode D1.

[0085] Control logic such as Fig.10 As shown:

[0086] 1. Static load is uniformly defined as load type T, and dynamic load is uniformly defined as load type D; the situation where the first optocoupler U9 is turned on by control circuit 1 is called IO1, the situation where the second optocoupler U2 is turned on by control circuit 2 is called IO2, and the situation where the second MOS tube Q4 is turned on by control circuit 3 is called IO3;

[0087] 2. If only the load T type is turned on at this time, IO1 and IO3 are turned off, IO2 is turned on, and the second MOS tube Q4 is turned on. Therefore, the path for the first MOS tube Q1 of the switching power supply to turn on does not pass through the negative end of the second polarity capacitor C2, but is directly connected to GND; at this time, the dynamic response is not so timely, and the switching cycle will be correspondingly reduced, thereby reducing the switching loss;

[0088] 3. If only the load D type is turned on or both the load D type and the load T type are turned on at this time, IO2 is turned off, IO1 and IO3 are turned on, so that the first optocoupler U9 and the second optocoupler U2 are turned on, so that the path of the first MOS tube Q1 of the switching power supply is consistent with the path in the first embodiment, achieving the effect of fast dynamic response and stable output voltage.

[0089] The switching power supply circuit provided in the embodiment of the present application can not only achieve the effect of the first embodiment, but also change the current path according to the load. When there is only a static load, the switching cycle is reduced, thereby reducing the switching loss. When there is a dynamic load, the dynamic response is fast and the output voltage is stable.

[0090] Based on the same inventive concept, the present application also provides an electrical device, which includes the switching power supply circuit provided in the above-mentioned embodiment 1 or embodiment 2.

[0091] The electrical equipment provided by the embodiment of the present application has the switching power supply circuit provided by embodiment one or embodiment two. When the first MOS tube is turned off, the primary winding of the transformer discharges and charges the second polarity capacitor. When the first MOS tube is turned on, the primary winding of the transformer is charged, and the current path is from the negative pole of the second polarity capacitor to the positive pole of the second polarity capacitor, and finally grounded. Therefore, the second polarity capacitor is discharging at this time, so when the switching power supply is turned on, the second polarity capacitor can be discharged quickly, and when the traditional switching power supply is turned on, the second polarity capacitor is charged. Therefore, the present application does not need to be discharged separately, the discharge speed is fast, the feedback is fast, and no optical coupling is required, and the cost is low.

[0092] It should be noted that, in the description of this application, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0093] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

Claims

1. A switching power supply circuit, characterized in that: include: A transformer and a first switching tube; The transformer comprises a primary winding, a secondary winding and an auxiliary winding; The first pin of the auxiliary winding is connected to the VCC pin of the chip inside the first switch tube; the first pin of the auxiliary winding is also connected to the first pin of the first switch tube through a reverse-connected transient suppression diode, and the first pin of the auxiliary winding is grounded; The first pin of the auxiliary winding is connected to the second pin of the first switch tube through a second polarity capacitor; The second pin of the auxiliary winding is connected to the second pin of the first switch tube via a reversely connected third diode; The first pin of the first switch tube is connected to the second pin of the first switch tube through a fifth resistor; The third pin of the first switch tube is connected to the feedback pin of the internal chip through a third resistor; the second pin of the first switch tube is connected to the first preset pin of the internal chip; The second preset pin of the internal chip is directly connected to the fourth pin of the primary winding; the second preset pin of the internal chip is connected to the fifth pin of the primary winding through a second diode and a filter circuit.

2. The switching power supply circuit according to claim 1, characterized in that: The filter circuit includes a first resistor and a first capacitor connected in parallel.

3. The switching power supply circuit according to claim 1, characterized in that: The first pin of the auxiliary winding is connected to the VCC pin of the chip inside the first switch tube through a second resistor.

4. The switching power supply circuit according to claim 1, characterized in that: The first pin of the auxiliary winding is connected to the first pin of the first switch tube through a fourth resistor and a reverse-connected transient suppression diode.

5. The switching power supply circuit according to claim 1, characterized in that: One foot of the secondary winding is grounded, and the other foot is positively connected to a fourth diode. A third polarity capacitor is connected between the two feet of the primary winding, and a fourth capacitor is connected in parallel at both ends of the third polarity capacitor.

6. A switching power supply circuit, characterized in that: include: A transformer and a first switching tube; The transformer comprises a primary winding, a secondary winding and an auxiliary winding; The first pin of the auxiliary winding is connected to the VCC pin of the chip inside the first switch tube; the first pin of the auxiliary winding is also connected to the first pin of the first switch tube through a reverse-connected transient suppression diode, and the first pin of the auxiliary winding is grounded through a first switch; the first pin of the auxiliary winding is connected to the second pin of the first switch tube through a second polarity capacitor and a second switch; The second pin of the auxiliary winding is connected to the second pin of the first switch tube via a reversely connected third diode and the second switch; A third switch is provided between the second polarity capacitor and the second switch, the third switch is located between the three diodes and the second switch, and the third switch is grounded; The first pin of the first switch tube is connected to the second pin of the first switch tube through a fifth resistor; The third pin of the first switch tube is connected to the feedback pin of the internal chip through a third resistor; the second pin of the first switch tube is connected to the first preset pin of the internal chip; The second preset pin of the internal chip is directly connected to the fourth pin of the primary winding; the second preset pin of the internal chip is connected to the fifth pin of the primary winding through a second diode and a filter circuit.

7. The switching power supply circuit according to claim 6, characterized in that: The filter circuit includes a first resistor and a first capacitor connected in parallel.

8. The switching power supply circuit according to claim 6, characterized in that: The first pin of the auxiliary winding is connected to the VCC pin of the chip inside the first switch tube through a second resistor.

9. The switching power supply circuit according to claim 6, characterized in that: The first pin of the auxiliary winding is connected to the first pin of the first switch tube through a fourth resistor and a reverse-connected transient suppression diode.

10. The switching power supply circuit according to claim 6, characterized in that: One foot of the secondary winding is grounded, and the other foot is positively connected to a fourth diode. A third polarity capacitor is connected between the two feet of the primary winding, and a fourth capacitor is connected in parallel at both ends of the third polarity capacitor.

11. The switching power supply circuit according to claim 6, characterized in that: The first switch and / or the third switch adopts an optical coupler, and the second switch adopts a second switch tube.

12. An electrical device, characterized in that: include: A switching power supply circuit as described in any one of claims 1 to 5 or claims 6 to 11.

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