Short circuit protection circuit, flyback power supply and inverter

Abstract

The invention discloses a short-circuit protection circuit, a flyback power supply and an inverter. The short-circuit protection circuit comprises a control module, a short-circuit protection module, a transformer, a primary side driving module connected with a primary side winding of the transformer, and a secondary side feedback module connected with a secondary side winding of the transformer. The output end of the control module is connected with the primary driving module, the primary sampling end of the control module is connected with the short-circuit protection module, and the feedback end of the control module is connected with the secondary feedback module and the short-circuit protection module; the short circuit protection module is used for pulling up the voltage of the primary side sampling end of the control module to a preset reference voltage under the condition that the short circuit of the secondary side winding is detected; and the control module is used for detecting feedback voltage generated by the secondary side feedback module at the feedback end, and is also used for blocking the PWM signal output to the primary side driving module under the condition that the voltage of the primary side sampling end is detected to be greater than the feedback voltage. According to the invention, the technical problem of circuit damage caused by short circuit of the secondary winding is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, and particularly relates to a short-circuit protection circuit, a flyback power supply and an inverter. BACKGROUND

[0002] At present, in the power electronics industry, most small power supplies use flyback power supplies. The flyback power supply realizes voltage conversion and isolation through a transformer. For example, the control chip of the flyback power supply can control the duty cycle of the PWM (Pulse Width Modulation) drive by controlling the feedback voltage of the secondary winding in the transformer, so as to control the energy input of the primary winding and realize stable regulation of the output voltage of the secondary winding.

[0003] When the secondary winding is short-circuited, the energy of the primary winding of the transformer cannot be released, so that the current of the primary winding continuously works at the maximum current point, thereby causing damage to the circuit. SUMMARY

[0004] The main purpose of the present application is to provide a short-circuit protection circuit, a flyback power supply and an inverter, which aims to solve the technical problem of circuit damage caused by short-circuit of the secondary winding.

[0005] To achieve the above purpose, the short-circuit protection circuit comprises a control module, a short-circuit protection module, a transformer, a primary drive module connected with the primary winding of the transformer, and a secondary feedback module connected with the secondary winding of the transformer.

[0006] The output end of the control module is connected with the primary drive module, the primary sampling end of the control module is connected with the short-circuit protection module, and the feedback end of the control module is connected with the secondary feedback module and the short-circuit protection module.

[0007] The short-circuit protection module is used for pulling up the voltage of the primary sampling end of the control module to a preset reference voltage when detecting that the secondary winding is short-circuited.

[0008] The control module is used for detecting the feedback voltage generated by the secondary feedback module at the feedback end, and is also used for blocking the PWM signal output to the primary drive module when detecting that the voltage of the primary sampling end is greater than the feedback voltage.

[0009] In an embodiment, the short-circuit protection module comprises a switching unit, a comparison unit and a voltage dividing unit.

[0010] The switching unit comprises a first switch tube, a first resistor and a second resistor, and the voltage dividing unit comprises a first capacitor, a third resistor and a fourth resistor.

[0011] The base of the first switch tube is connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the comparison unit, the second end of the comparison unit is connected to the first end of the third resistor and the first end of the first capacitor, the second end of the third resistor is connected to the feedback end, the first end of the fourth resistor is connected to the first end of the third resistor, and the second end of the fourth resistor and the second end of the first capacitor are grounded.

[0012] The collector of the first switch tube is connected to the primary sampling end, and the emitter of the first switch tube is connected to the reference voltage end of the control module and the first end of the second resistor.

[0013] In an embodiment, when the first switch tube is turned on, the first switch tube is used to pull up the voltage of the primary sampling end to a preset reference voltage.

[0014] In an embodiment, the short circuit protection module further comprises a delay unit arranged between the collector of the first switch tube and the primary sampling end, and the delay unit comprises a second capacitor, a fifth resistor, a sixth resistor, a seventh resistor and a second switch tube.

[0015] The first end of the second capacitor is connected to the first end of the fifth resistor and the first end of the sixth resistor, and the second end of the fifth resistor is connected to the collector of the first switch tube.

[0016] The second end of the sixth resistor is connected to the base of the second switch tube, the emitter of the second switch tube is connected to the primary sampling end, the collector of the second switch tube is connected to the first end of the seventh resistor, and the second end of the seventh resistor is connected to the reference voltage end of the control module.

[0017] In an embodiment, the delay unit is used to prolong the time for the voltage of the feedback end to be fed back to the comparison unit when the control module starts power-on.

[0018] In an embodiment, the first switch tube is a PNP type triode, and the second switch tube is an NPN type triode.

[0019] In an embodiment, the comparison unit is a voltage stabilizer or a comparator.

[0020] In an embodiment, when the comparison unit is a voltage stabilizer, the third end of the comparison unit is grounded.

[0021] The voltage stabilizer is used to pull down the voltage of the base of the first switch tube to turn on the first switch tube when the voltage of the second end of the comparison unit is greater than the preset comparison voltage threshold of the voltage stabilizer.

[0022] When the comparison unit is a comparator, the short-circuit protection module further includes an eighth resistor and a ninth resistor. The third terminal of the comparison unit is connected to the first terminal of the eighth resistor and the first terminal of the ninth resistor. The second terminal of the eighth resistor is connected to the reference voltage terminal of the control module, and the second terminal of the ninth resistor is grounded.

[0023] The comparator is used to pull down the voltage at the base of the first switch transistor to turn on the first switch transistor when the voltage at the second terminal of the comparator unit is greater than the voltage at the third terminal of the comparator unit.

[0024] In one embodiment, the primary-side driving module includes a primary-side sampling unit and a primary-side driving unit. The primary-side sampling unit includes a first sampling resistor, a third capacitor, and a tenth resistor. The primary-side driving unit includes a power switch and an eleventh resistor.

[0025] The primary winding is connected to the first terminal of the power switch transistor, the second terminal of the power switch transistor is connected to the first terminal of the eleventh resistor, and the second terminal of the eleventh resistor is connected to the output terminal of the control module.

[0026] The third terminal of the power switch is connected to the first terminal of the first sampling resistor and the first terminal of the tenth resistor. The second terminal of the first sampling resistor is connected to the first terminal of the third capacitor. The two terminals of the third capacitor and the second terminal of the tenth resistor are connected to the primary side sampling terminal.

[0027] The primary-side sampling unit is used to detect the primary-side voltage of the primary-side winding.

[0028] In one embodiment, the secondary feedback module is used to convert the secondary voltage of the secondary winding into a secondary current and feed the secondary current back to the feedback terminal.

[0029] In one embodiment, the feedback terminal of the control module includes a feedback interface, a current source, and a second sampling resistor;

[0030] The first end of the second sampling resistor is connected to the current source and the feedback interface, the second end of the second sampling resistor is grounded, and the feedback interface is connected to the short-circuit protection module and the secondary feedback module;

[0031] The control module is used to detect the feedback voltage generated by the secondary current of the secondary feedback module in the second sampling resistor.

[0032] The present invention also provides a flyback power supply, which includes the short-circuit protection circuit described above.

[0033] The present invention also provides an inverter, which includes the short-circuit protection circuit described above.

[0034] This invention provides a short-circuit protection circuit, which can achieve at least the following technical effects: By setting a short-circuit protection module in the short-circuit protection circuit, and both the short-circuit protection module and the secondary-side feedback module are connected to the feedback terminal of the control module, the control module can detect the feedback voltage generated at the feedback terminal by the secondary-side feedback module. The secondary-side feedback module is connected to the secondary winding of the transformer, so when the secondary winding is short-circuited, the feedback voltage generated at the feedback terminal by the secondary-side feedback module will also change. Since the short-circuit protection module is also connected to the feedback terminal, it will also be affected when the secondary winding is short-circuited. When the short-circuit protection module in this invention is affected by the secondary winding short circuit, it will pull the voltage at the primary-side sampling terminal of the control module up to a preset reference voltage. The reference voltage can be used to describe the reference voltage of the control module. In order to ensure the stability of the control module output, the reference voltage of the control module is set higher than the voltage generated at the feedback terminal by the secondary feedback module. Therefore, when the primary sampling terminal of the control module is pulled up to the preset reference voltage, the voltage at the primary sampling terminal will be greater than the feedback voltage. Thus, the control module can detect that the primary sampling voltage is greater than the feedback voltage. When the primary sampling voltage is greater than the feedback voltage, the control module blocks the PWM signal output to the primary drive module. Since the primary drive module is connected to the primary winding, after the control module blocks the PWM signal, it can also cut off the continuous current generated in the primary winding when the secondary winding is short-circuited, thereby realizing short-circuit protection and avoiding circuit damage caused by short circuit. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of a short-circuit protection circuit according to an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of a short-circuit protection module in the short-circuit protection circuit of the present invention;

[0039] Figure 3 This is a circuit connection diagram of an embodiment of the short-circuit protection module in the short-circuit protection circuit of the present invention;

[0040] Figure 4This is a schematic diagram of another embodiment of the short-circuit protection module in the short-circuit protection circuit of the present invention;

[0041] Figure 5 This is a circuit connection diagram of another embodiment of the short-circuit protection module in the short-circuit protection circuit of the present invention;

[0042] Figure 6 This is a circuit connection diagram of another embodiment of the short-circuit protection module in the short-circuit protection circuit of the present invention;

[0043] Figure 7 This is a schematic diagram of another embodiment of the short-circuit protection circuit of the present invention;

[0044] Figure 8 This is a circuit connection diagram of one embodiment of the short-circuit protection circuit of the present invention;

[0045] Figure 9 This is a circuit connection diagram of another embodiment of the short-circuit protection circuit of the present invention.

[0046] Explanation of icon numbers:

[0047] 100. Control module; 200. Transformer; 210. Primary winding; 220. Secondary winding; T1. Core; 300. Primary drive module; 400. Secondary feedback module; 500. Short circuit protection module; CS. Primary sampling terminal; OUT. Output terminal of control module; FKD. Feedback terminal; VRef. Reference voltage terminal; 510. Switching unit; 520. Comparison unit; 530. Voltage divider unit; 540. Delay unit; 221. Main winding; 222. Secondary winding; 230. Chip power supply winding; 310. Primary drive module; 320, primary-side sampling unit; 410, feedback unit; 600, rectifier input unit; R1~R12, first resistor~twelfth resistor; C1~C6, first capacitor~sixth capacitor; D1~D4, first diode~fourth diode; Q1, first switching transistor; Q2, second switching transistor; Q3, power switching transistor; Rs1, first sampling resistor; Rs2, second sampling resistor; IS, current source; B1, Zener diode; B2, comparator; VCC, power supply terminal of control module; Comp, feedback interface; GND, ground.

[0048] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0049] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Currently, in the power electronics industry, most low-power power supplies use flyback power supplies. Flyback power supplies achieve voltage conversion and isolation through transformers. For example, the control chip of a flyback power supply can control the feedback voltage of the secondary winding in the transformer to adjust the duty cycle of the PWM drive in real time, thereby controlling the energy input of the primary winding and achieving stable regulation of the output voltage of the secondary winding.

[0051] When the secondary winding is short-circuited, the energy in the primary winding of the transformer has nowhere to be released, causing the current in the primary winding to continue to operate at the maximum current point, which in turn leads to circuit damage.

[0052] To address this issue, this invention proposes a short-circuit protection circuit. The short-circuit protection module in the circuit raises the voltage at the primary-side sampling terminal of the control module, ensuring that the voltage at the primary-side sampling terminal is greater than the feedback voltage generated at the feedback terminal by the secondary-side feedback module. This blocks the PWM signal output by the control module, thereby cutting off the current in the primary winding and preventing continuous high-current operation that could damage the circuit. Furthermore, since this embodiment achieves short-circuit protection by raising the voltage at the primary-side sampling terminal, it extends the hiccup interval of the control module, thus preventing overheating during short circuits and potential circuit damage. For example, it can prevent the auxiliary power supply to the control module from overheating and being damaged.

[0053] Based on this, the present invention proposes a short-circuit protection circuit in the first embodiment, please refer to... Figure 1 The short-circuit protection circuit includes: a control module 100, a short-circuit protection module 500, a transformer 200, a primary drive module 300 connected to the primary winding 210 of the transformer 200, and a secondary feedback module 400 connected to the secondary winding 220 of the transformer 200.

[0054] The output terminal OUT of the control module 100 is connected to the primary-side drive module 300, the primary-side sampling terminal CS of the control module 100 is connected to the short-circuit protection module 500, and the feedback terminal FKD of the control module 100 is connected to the secondary-side feedback module 400 and the short-circuit protection module 500.

[0055] The short-circuit protection module 500 is used to pull up the voltage of the primary sampling terminal cs of the control module 100 to a preset reference voltage when a short circuit is detected in the secondary winding 220.

[0056] The control module 100 is used to detect the feedback voltage generated by the secondary feedback module 400 at the feedback terminal fkd, and is also used to block the PWM signal output to the primary driving module 300 when the voltage at the primary sampling terminal cs is detected to be greater than the feedback voltage.

[0057] In this embodiment, the control module 100 can be a peak current control chip, and the feedback terminal fkd of the control module 100 can detect the feedback voltage of the secondary feedback module 400.

[0058] In the event of a short circuit in the secondary winding 220, the feedback voltage at the feedback terminal fkd of the secondary feedback module 400 connected to the secondary winding 220 will also change, which will also affect the short circuit protection module 500. The short circuit protection module 500 will be affected by the short circuit in the secondary winding 220 and will raise the voltage at the primary sampling terminal cs of the control module 100. When the voltage at the primary sampling terminal cs is greater than the feedback voltage, the PWM signal output by the control module 100 will be blocked to achieve short circuit protection. In this embodiment, when the secondary winding 220 is not short-circuited, the short-circuit protection module 500 is disconnected from the primary sampling terminal CS. When the secondary winding 220 is short-circuited, the short-circuit protection module 500 is connected to the primary sampling terminal CS. The short-circuit protection module 500 can also be connected to the reference voltage terminal Vref of the control module 100. The reference voltage terminal Vref can provide a reference voltage for the short-circuit protection module 500. Thus, when the secondary winding 220 is short-circuited, the short-circuit protection module 500 can pull the voltage of the primary sampling terminal CS up to a preset reference voltage. The preset reference voltage is close to the reference voltage of the control module 100. The preset reference voltage can also be equal to the reference voltage. When the preset reference voltage is close to the reference voltage of the control module 100, the difference between the preset reference voltage and the reference voltage of the control module 100 can be less than the preset voltage difference, which can be less than 1V, etc. This embodiment does not specifically limit this.

[0059] The primary-side sampling terminal CS of the control module 100 can be the CS port (Chip Select) of a peak current control chip, or it can be an interface in the control chip that can receive the primary-side voltage of the primary-side drive module 300. The feedback terminal fkd of the control module 100 can be a COMP (Compensation) angle, which includes the COMP interface.

[0060] The transformer may also include a chip power supply winding connected to the power supply terminal VCC of the control module 100, which can supply power to the control module 100. The power supply capability of the chip power supply winding is affected by the primary-side drive module 300. When the primary-side drive module 300 stops providing energy (e.g., voltage), the chip power supply winding cannot receive energy from the primary-side drive module 300, and the voltage supplied by the chip power supply winding to the control module 100 will also decrease. Since the chip power supply winding also includes a capacitor, when the chip power supply winding does not receive energy from the primary-side drive module 300, the chip power supply winding will periodically supply power to the control module 100 through the capacitor. Therefore, after blocking the PWM signal of the control module 100, the output of energy to the primary-side drive module 300 stops, and the voltage received by the power supply terminal Vcc of the control module 100 will gradually decrease. When the voltage of the power supply terminal Vcc of the control module 100 decreases to a certain value, the control module 100 will continuously restart until the secondary-side feedback module 400 returns to normal. Then, the voltage of the primary-side sampling terminal CS returns to the primary-side voltage, so that the control module 100 can normally adjust the duty cycle of the PWM signal, thereby controlling the primary-side drive module 300 to normally provide energy to the secondary-side winding 220.

[0061] This invention embodiment includes a short-circuit protection module within the short-circuit protection circuit. Both the short-circuit protection module and the secondary-side feedback module are connected to the feedback terminal of the control module. The control module can detect the feedback voltage generated at the feedback terminal by the secondary-side feedback module. Since the secondary-side feedback module is connected to the secondary winding of the transformer, when the secondary winding is short-circuited, the feedback voltage generated at the feedback terminal by the secondary-side feedback module will change. Because the short-circuit protection module is also connected to the feedback terminal, it is also affected when the secondary winding is short-circuited. In this embodiment, the short-circuit protection module, affected by the secondary winding short circuit, will pull the voltage at the primary-side sampling terminal of the control module up to a preset reference voltage. This preset reference voltage can be used to describe the control... The reference voltage of the module; in order to ensure the stability of the control module output, the reference voltage of the control module is set higher than the voltage generated at the feedback terminal of the secondary feedback module. Therefore, when the primary sampling terminal of the control module is pulled up to the preset reference voltage, the voltage at the primary sampling terminal will be greater than the feedback voltage. Thus, the control module can detect that the primary sampling voltage is greater than the feedback voltage. When the primary sampling voltage is greater than the feedback voltage, the control module blocks the PWM signal output to the primary drive module. Since the primary drive module is connected to the primary winding, after the control module blocks the PWM signal, it can also cut off the continuous current generated in the primary winding when the secondary winding is short-circuited, thereby achieving short-circuit protection and avoiding circuit damage caused by short circuit.

[0062] In one feasible embodiment, please refer to Figure 2 and Figure 3The short-circuit protection module 500 includes a switching unit 510, a comparison unit 520, and a voltage divider unit 530;

[0063] The switching unit 510 includes a first switching transistor Q1, a first resistor R1 and a second resistor R2, and the voltage divider unit 530 includes a first capacitor C1, a third resistor R3 and a fourth resistor R4.

[0064] The base of the first switch Q1 is connected to the first terminal of the first resistor R1. The second terminal of the first resistor R1 is connected to the first terminal of the comparator unit 520. The second terminal of the comparator unit 520 is connected to the first terminal of the third resistor R3 and the first terminal of the first capacitor C1. The second terminal of the third resistor R3 is connected to the feedback terminal fkd. The first terminal of the fourth resistor R4 is connected to the first terminal of the third resistor R3. The second terminal of the fourth resistor R4 and the second terminal of the first capacitor C1 are grounded.

[0065] The collector of the first switching transistor Q1 is connected to the primary side sampling terminal cs, the emitter of the first switching transistor Q1 is connected to the reference voltage terminal of the control module 100 and the first terminal of the second resistor R2, and the second terminal of the second resistor R2 is connected to the first terminal of the comparator unit 520.

[0066] It should be noted that, referring to Figure 2 The short-circuit protection module 500 includes a switching unit 510, a comparison unit 520, and a voltage divider unit 530. The voltage divider unit 530 can be used to adjust the voltage at the second terminal of the comparison unit 520 so that when the secondary winding 220 is short-circuited, the voltage at the second terminal of the comparison unit 520 can be greater than the comparison reference voltage of the comparison unit 520, thereby pulling down the voltage at the first terminal of the comparison unit 520 and improving the reliability of the short-circuit protection.

[0067] The voltage divider unit 530 also includes a first capacitor C1. The voltage divider unit 530 can also be used to increase the delay of the short-circuit protection module 500. For example, it can extend the time for pulling down the voltage at the first terminal of the comparison unit 520 to avoid falsely triggering the short-circuit protection mechanism (to prevent the short-circuit protection module 500 from mistakenly pulling up the primary-side sampling voltage to a preset reference voltage). In this embodiment, the comparison unit can be a voltage regulator or a comparator.

[0068] Reference Figure 3 , Figure 3This diagram illustrates one possible circuit connection for the short-circuit protection module when the comparator unit is a voltage regulator. The switching unit 510 controls the conduction and / or disconnection between the short-circuit protection module 500 and the primary-side sampling terminal CS. The first switching transistor Q1 is a PNP transistor. The base of the first switching transistor Q1 is connected to the first terminal of the comparator unit 520 through the first resistor R1. The second terminal of the comparator unit 520 is connected to the feedback terminal fkd of the control module 100 through the third resistor R3. The comparator unit 520 can be used to trigger the switching unit 510 to conduct when the secondary winding 220 is short-circuited, and to keep the switching unit 510 disconnected when the secondary winding 220 is normal. For example, when the secondary winding 220 is short-circuited, the feedback voltage at the feedback terminal fkd will rise. Affected by this rise, the voltage at the second terminal of the comparator 520 will be greater than its reference voltage, pulling down the voltage at the first terminal. This, in turn, lowers the base voltage of the first switching transistor Q1. Since the emitter of the first switching transistor Q1 is connected to the reference voltage terminal of the control module 100, the voltage at the emitter of the first switching transistor Q1 is equal to the base voltage of the control module 100. The reference voltage of block 100 is such that when the voltage at the base of the first switch Q1 is pulled low by the comparator unit 520, the first switch Q1 is turned on. When the collector of the first switch Q1 is connected to the primary side sampling terminal cs, the voltage at the primary side sampling terminal cs can be pulled up to the preset reference voltage when the first switch Q1 is turned on. When the collector of the first switch Q1 is connected to the delay unit 540, the voltage at the primary side sampling terminal cs can be pulled up to the preset reference voltage through the delay unit 540 when the first switch Q1 is turned on.

[0069] In one feasible embodiment, when the first switch is turned on, the first switch is used to pull up the voltage at the primary side sampling terminal to a preset reference voltage.

[0070] It should be noted that since the emitter of the first switch Q1 is connected to the reference voltage terminal vref of the control module 100, the reference voltage terminal vref can provide a reference voltage to the emitter of the first switch Q1. Thus, when the first switch Q1 is turned on, the first switch Q1 can pull the voltage of the primary side sampling terminal cs to the preset reference voltage.

[0071] Furthermore, in yet another feasible embodiment, please refer to Figure 4 and Figure 5 , Figure 5 The diagram shows the circuit connection of the short circuit protection module including a delay unit and the comparison unit being a voltage regulator B1. The short circuit protection module also includes a delay unit set between the collector of the first switching transistor and the primary side sampling terminal. The delay unit 540 includes a second capacitor C2, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and a second switching transistor Q2.

[0072] The first terminal of the second capacitor C2 is connected to the first terminal of the fifth resistor R5 and the first terminal of the sixth resistor R6, and the second terminal of the fifth resistor R5 is connected to the collector of the first switching transistor Q1.

[0073] The second end of the sixth resistor R6 is connected to the base of the second switch Q2, the emitter of the second switch Q2 is connected to the primary side sampling terminal cs, the collector of the second switch Q2 is connected to the first end of the seventh resistor R7, and the second end of the seventh resistor R7 is connected to the reference voltage terminal of the control module 100.

[0074] In one embodiment, the first switching transistor is a PNP transistor and the second switching transistor is an NPN transistor.

[0075] In one embodiment, the delay unit 540 is used to extend the time for the voltage at the feedback terminal to be fed back to the comparison unit 540 when the control module 100 is powered on.

[0076] It should be noted that the short-circuit protection module 500 may include a delay unit 540. The delay unit 540 is used to increase the delay of the short-circuit protection module 500 to avoid false triggering of the short-circuit protection when the control module 100 is powered on again. For example, the delay can be increased by using the second capacitor C2 and the fifth resistor R5 in the delay unit 540, extending the time for the voltage at the feedback terminal to be fed back to the comparison unit 540, thereby delaying the triggering of the short-circuit protection. When the secondary winding is short-circuited, the voltage of the secondary winding will be low. When the control module starts up, the primary winding has not yet had time to provide energy to the secondary winding, and the voltage of the secondary winding is also low. Therefore, to avoid false triggering of the short-circuit protection mechanism, a delay unit can be added to improve the reliability of the short-circuit protection and prevent the voltage at the primary sampling terminal from being pulled up even when the secondary winding is normal. The second switching transistor Q2 is an NPN transistor.

[0077] The collector of the first switch Q1 is connected to the base of the second switch Q2. When the first switch Q1 is turned on, the voltage transmitted from the first switch Q1 to the base of the second switch Q2 is close to a reference voltage, for example, it can be a preset reference voltage. The emitter of the second switch Q2 is connected to the primary-side sampling terminal cs. Before the second switch Q2 is turned on, the voltage at the primary-side sampling terminal cs is still the primary-side voltage. Since the preset reference voltage is greater than the primary-side voltage, when the base of the second switch Q2 receives the voltage when the first switch Q1 is turned on, the second switch Q2 also turns on, and the second switch Q2 pulls up the voltage at the primary-side sampling terminal cs, for example, it can pull it up to the preset reference voltage. And since the base of the second switch Q2 is connected to the second capacitor C2 and the fifth resistor R5, the second switch Q2 will also turn on with a delay. This can improve the reliability of short-circuit protection and avoid the situation where the short-circuit protection module 500 is mistakenly triggered to pull up the edge sampling voltage when the control module 100 is powered on again because the voltage output by the secondary feedback module 400 is too low and the feedback between the control module 100 and the secondary feedback module 400 has not been established in time.

[0078] In one possible embodiment, the comparison unit 520 is either a voltage regulator B1 or a comparator B2.

[0079] When the comparator unit 520 is a voltage regulator B1, the third terminal of the comparator unit 520 is grounded;

[0080] The voltage regulator B1 is used to pull down the voltage at the base of the first switching transistor Q1 to turn on the first switching transistor Q1 when the voltage at the second terminal of the comparator unit 520 is greater than the preset comparison voltage threshold of the voltage regulator B1.

[0081] When the comparison unit 520 is comparator B2, the short circuit protection module 500 also includes an eighth resistor R8 and a ninth resistor R9. The third terminal of the comparison unit 520 is connected to the first terminal of the eighth resistor R8 and the first terminal of the ninth resistor R9. The second terminal of the eighth resistor R8 is connected to the reference voltage terminal of the control module, and the second terminal of the ninth resistor R9 is grounded.

[0082] Comparator B2 is used to pull down the base voltage of the first switching transistor Q1 to turn on the first switching transistor Q1 when the voltage at the second terminal of the comparison unit 520 is greater than the voltage at the third terminal of the comparison unit 520.

[0083] It should be noted that when the comparator unit 520 is a voltage regulator B1, the third terminal of the comparator unit 520 is the A port of the voltage regulator B1, the first terminal of the comparator unit 520 is the K port of the voltage regulator B1, and the second terminal of the comparator unit 520 is the R port of the voltage regulator B1. The voltage regulator B1 can be a TL431. When the comparator unit 520 is a TL431, the comparison reference voltage is 2.5V. When the voltage at the second terminal of the comparator unit is greater than the preset comparison voltage threshold of the voltage regulator, the first terminal of the comparator unit outputs a low level to pull down the base voltage of the first switching transistor, thereby turning on the first switching transistor Q1.

[0084] You can refer to Figure 6 , Figure 6 This diagram illustrates the circuit connection of the short-circuit protection module without a delay unit, where the comparison unit is comparator B2. When the comparison unit 520 is comparator B2, its third terminal is connected to the first terminal of the eighth resistor R8 and the first terminal of the ninth resistor R9. The second terminal of the eighth resistor R8 is connected to the reference voltage terminal of the control module, and the second terminal of the ninth resistor R9 is grounded. The preset comparison voltage threshold of the comparison unit 520 is the voltage at the third terminal of comparator B2, which can be calculated based on the eighth resistor R8, the ninth resistor R9, and the reference voltage, for example, Vref×(R8 / (R8+R9)). If the voltage at the second terminal of the comparison unit 520 is greater than the voltage at the third terminal, the voltage at the first terminal of the comparison unit 520 is pulled down to lower the voltage at the base of the first switching transistor. When the comparison unit is a voltage regulator or a comparator, the short-circuit protection module may or may not include a delay unit; this embodiment does not specifically limit this.

[0085] Furthermore, in another feasible embodiment, please refer to Figure 7 and Figure 8 The primary-side driving module 300 includes a primary-side sampling unit 320 and a primary-side driving unit 310. The primary-side sampling unit 320 includes a first sampling resistor Rs1, a third capacitor C3 and a tenth resistor R10. The primary-side driving unit 310 includes a power switch Q3 and an eleventh resistor R11.

[0086] The primary winding 210 is connected to the first terminal of the power switch Q3, the second terminal of the power switch Q3 is connected to the first terminal of the eleventh resistor R11, and the second terminal of the eleventh resistor R11 is connected to the output terminal out of the control module 100.

[0087] The third terminal of the power switch Q3 is connected to the first terminal of the first sampling resistor Rs1 and the first terminal of the tenth resistor R10. The second terminal of the first sampling resistor Rs1 is connected to the first terminal of the third capacitor C3. The two terminals of the third capacitor C3 and the second terminal of the tenth resistor R10 are connected to the primary side sampling terminal cs.

[0088] The primary-side sampling unit is used to detect the primary-side voltage of the primary winding 210.

[0089] It should be noted that when the secondary winding 220 is not short-circuited, the circuit consisting of the control module 100, transformer 200, primary drive module 300, and secondary feedback module 400 can operate normally. The primary drive module 300 is connected to the primary sampling terminal CS of the control module 100. The primary drive module 300 can be used to detect the primary voltage of the primary winding 210. For example, the control module 100 can obtain the primary voltage detected by the primary drive module 300 at the primary sampling terminal CS, and can detect the feedback voltage of the secondary feedback module 400 at the feedback terminal FKD. The control module 100 can accurately determine the duty cycle of the output PWM signal based on the primary voltage and the feedback voltage, so that the primary drive module 300 can stably provide energy to the secondary feedback module 400.

[0090] It should also be noted that the first terminal of the power switch can be the drain, the second terminal can be the gate, and the third terminal can be the source. The primary winding 210 can provide energy to the secondary winding 220. The primary drive module 300 may also include a first diode D1, with the anode of the first diode D1 connected to the rectifier input unit 600, the cathode of the first diode D1 connected to the first terminal of the primary winding 210, and the second terminal of the primary winding 210 connected to the drain of the power switch Q3. (Refer to...) Figure 8 , Figure 8 The diagram shows the circuit connection between the control module, transformer, primary drive module, and secondary feedback module. The short-circuit protection circuit may also include a rectifier input unit 600 and a twelfth resistor R12. The rectifier input unit 600 can be a DC or AC rectifier input. The primary winding 210 can be connected to the rectifier input unit 600. The first end of the twelfth resistor R12 is connected to the rectifier input unit 600, and the second end of the twelfth resistor R12 is connected to the chip power supply winding 230.

[0091] The short-circuit protection circuit may also include a second diode D2 and a fourth capacitor C4. The cathode of the second diode D2 is connected to the second terminal of the twelfth resistor R12, and the anode of the second diode D2 is connected to the first terminal of the chip power supply winding 230. The second terminal of the chip power supply winding 230 is connected to the power supply terminal Vcc of the control module 100. There is an iron core T1 between the primary winding 210 and the secondary winding 220.

[0092] In the primary-side sampling unit, the first terminal of the first sampling resistor Rs1 and the first terminal of the third capacitor C3 are grounded. The first sampling resistor Rs1 can detect the primary-side voltage of the primary winding 210 and transmit it to the primary-side sampling terminal cs, so that the control module 100 can obtain the primary-side voltage at the primary-side sampling terminal cs. The power switch Q3 is connected to the output terminal out of the control module 100. The output terminal out of the control module 100 can output a PWM signal. By adjusting the duty cycle of the output PWM signal, the on and off time of the power switch Q3 can be adjusted, thereby driving the primary winding 210 to provide energy to the secondary winding 220. When the PWM signal is blocked, the power switch Q3 is turned off, so that no current flows through the primary winding 210. Therefore, when the secondary winding 220 is short-circuited, the primary winding 210 can be prevented from continuously operating at high current, thus preventing burnout. Furthermore, when no current flows through the primary winding 210, no magnetic field change is generated in the primary winding 210. Without magnetic field change, no electromotive force is induced in the secondary winding 220, so the secondary winding 220 does not provide energy to the load, ensuring the safety of the circuit.

[0093] In one feasible embodiment, reference may continue to be made to... Figure 8 The secondary feedback module 400 is used to convert the secondary voltage of the secondary winding 220 into secondary current and feed the secondary current back to the feedback terminal fkd.

[0094] The secondary feedback module 400 includes a feedback unit 410, a third diode D3, a fifth capacitor C5, a fourth diode D4, and a sixth capacitor C6. The feedback unit 410 can be used to convert the secondary voltage of the secondary winding 220 into a secondary current and feed the secondary current back to the feedback terminal fkd. The feedback voltage is detected at the feedback terminal fkd. The secondary winding 220 includes a primary winding 221 and a secondary winding 222. The first end of the primary winding 221 is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the first end of the fifth capacitor C5, and the second end of the fifth capacitor C5 is connected to the second end of the primary winding 221. The secondary winding 222 includes a secondary winding 222, a fourth diode D4, and a sixth capacitor C6. The first end of the secondary winding 222 is connected to the anode of the fourth diode D4, the cathode of the fourth diode D4 is connected to the first end of the sixth capacitor C6, and the second end of the sixth capacitor C6 is connected to the second end of the secondary winding 222. The cathode of the fourth diode D4 is also connected to the input terminal of the secondary feedback module 400, and the output terminal of the secondary feedback module 400 is connected to the feedback terminal fkd of the control module 100.

[0095] In one feasible embodiment, the feedback terminal fkd of the control module 100 includes a feedback interface, a current source IS, and a second sampling resistor Rs2;

[0096] The first end of the second sampling resistor Rs2 is connected to the current source IS and the feedback interface, the second end of the second sampling resistor Rs2 is grounded, and the feedback interface is connected to the short circuit protection module 500 and the secondary feedback module 400.

[0097] The control module 100 is used to detect the feedback voltage generated by the secondary current of the secondary feedback module 400 in the second sampling resistor Rs2.

[0098] It should be noted that the feedback interface can be the COMP interface of the control module 100. The feedback interface, the current source IS, and the second sampling resistor Rs2 can all serve as the feedback terminal fkd of the control module 100. The second sampling resistor Rs2 can be used to detect the feedback voltage.

[0099] When the secondary winding 220 is short-circuited, the current pulled outward from the current source IS of the feedback terminal fkd by the secondary feedback module 400 decreases, causing the current in the current source IS to flow to the first sampling resistor Rs1. This, in turn, increases the voltage across the first sampling resistor Rs1, thus increasing the feedback voltage. Therefore, the feedback voltage increases when the secondary winding 220 is short-circuited. When the feedback voltage increases, the voltage at the second terminal of the comparator unit 520, which is connected to the feedback terminal fkd through the third resistor R3, increases, thereby turning on the first switching transistor Q1 to pull the voltage at the primary sampling terminal cs up to a preset reference voltage.

[0100] Because a 1V Zener diode is installed across the second sampling resistor Rs2, the feedback voltage at the feedback terminal fkd will not exceed 1V even if it rises. The preset reference voltage is close to the reference voltage of the control module 100, which is derived from a voltage divider of the power supply terminal Vcc. The reference voltage of the control module 100 is typically 5V. Therefore, when the primary-side sampling terminal CS is pulled high to the preset reference voltage, the voltage at the primary-side sampling terminal CS will be greater than the voltage at the feedback terminal fkd, thus continuously blocking the PWM signal. Since the voltage at the primary-side sampling terminal CS will continuously rise to the preset reference voltage when the secondary winding 220 is short-circuited, the hiccup time of the control module 100 can be extended, thereby reducing circuit damage caused by overheating.

[0101] To better understand the embodiments of the present invention, please refer to Figure 9 The process of blocking the PWM signal in this embodiment will be briefly described. Figure 9 This is a schematic diagram of the overall circuit connection of one type of short-circuit protection circuit. Figure 9The diagram illustrates the circuit connection of the short-circuit protection circuit when the short-circuit protection module does not include a delay unit and the comparison unit is a voltage regulator: When the secondary winding 220 is short-circuited, the current pulled outward from the current source IS of the feedback terminal fkd by the secondary feedback module 400 decreases, causing the current of the current source IS to flow to the first sampling resistor Rs1. The voltage across the first sampling resistor Rs1 increases, and since the voltage across the first sampling resistor Rs1 is the feedback voltage, the feedback voltage also increases. When the feedback voltage increases, the voltage at the R terminal of TL431 also increases and becomes greater than the comparison reference voltage. At this time, the voltage at the K terminal of TL431 is pulled low, thereby turning on the first switching transistor Q1. The emitter of the first switching transistor Q1 is connected to the reference voltage terminal of the control module 100. The reference voltage terminal can provide a reference voltage to the emitter of the first switching transistor Q1, so that the first switching transistor Q1 can pull the voltage at the primary sampling terminal cs to a preset reference voltage. The value of the preset reference voltage can change with the reference voltage output by the reference voltage terminal of the control module 100.

[0102] This invention also provides a flyback power supply, which includes the short-circuit protection circuit described above, aiming to solve the technical problem of circuit damage caused by a short circuit in the secondary winding. Compared with the prior art, the beneficial effects of the flyback power supply provided by this invention are the same as those of the short-circuit protection circuit provided in the above embodiments, and other technical features of this flyback power supply are the same as those disclosed in the methods of the above embodiments, and will not be repeated here.

[0103] This invention also provides an inverter, which includes the short-circuit protection circuit described above, aiming to solve the technical problem of circuit damage caused by a short circuit in the secondary winding. Compared with the prior art, the beneficial effects of the inverter provided by this invention are the same as those of the short-circuit protection circuit provided in the above embodiments, and other technical features of this inverter are the same as those disclosed in the methods of the above embodiments, and will not be repeated here.

[0104] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent scope of the present invention.

Claims

1. A short-circuit protection circuit, characterized in that, The short-circuit protection circuit includes: a control module, a short-circuit protection module, a transformer, a primary drive module connected to the primary winding of the transformer, and a secondary feedback module connected to the secondary winding of the transformer. The output terminal of the control module is connected to the primary-side drive module, the primary-side sampling terminal of the control module is connected to the short-circuit protection module, and the feedback terminal of the control module is connected to the secondary-side feedback module and the short-circuit protection module. The short-circuit protection module is used to pull up the voltage of the primary sampling terminal of the control module to a preset reference voltage when a short circuit is detected in the secondary winding. The control module is used to detect the feedback voltage generated by the secondary feedback module at the feedback terminal, and is also used to block the PWM signal output to the primary driving module when the voltage at the primary sampling terminal is detected to be greater than the feedback voltage.

2. The short-circuit protection circuit as described in claim 1, characterized in that, The short-circuit protection module includes a switching unit, a comparison unit, and a voltage divider unit; The switching unit includes a first switching transistor, a first resistor, and a second resistor; the voltage divider unit includes a first capacitor, a third resistor, and a fourth resistor. The base of the first switching transistor is connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the comparator unit, the second end of the comparator unit is connected to the first end of the third resistor and the first end of the first capacitor, the second end of the third resistor is connected to the feedback terminal, the first end of the fourth resistor is connected to the first end of the third resistor, and the second end of the fourth resistor and the second end of the first capacitor are grounded. The collector of the first switching transistor is connected to the primary side sampling terminal, the emitter of the first switching transistor is connected to the reference voltage terminal of the control module and the first terminal of the second resistor, and the second terminal of the second resistor is connected to the first terminal of the comparison unit.

3. The short-circuit protection circuit as described in claim 2, characterized in that, When the first switch is turned on, the first switch is used to pull the voltage at the primary side sampling terminal up to a preset reference voltage.

4. The short-circuit protection circuit as described in claim 2, characterized in that, The short-circuit protection module further includes: a delay unit disposed between the collector of the first switching transistor and the primary side sampling terminal, the delay unit including a second capacitor, a fifth resistor, a sixth resistor, a seventh resistor and a second switching transistor; The first terminal of the second capacitor is connected to the first terminal of the fifth resistor and the first terminal of the sixth resistor, and the second terminal of the fifth resistor is connected to the collector of the first switching transistor. The second end of the sixth resistor is connected to the base of the second switching transistor, the emitter of the second switching transistor is connected to the primary side sampling terminal, the collector of the second switching transistor is connected to the first end of the seventh resistor, and the second end of the seventh resistor is connected to the reference voltage terminal of the control module.

5. The short-circuit protection circuit as described in claim 4, characterized in that, The delay unit is used to extend the time for the voltage at the feedback terminal to be fed back to the comparison unit when the control module is powered on.

6. The short-circuit protection circuit as described in claim 4, characterized in that, The first switching transistor is a PNP transistor, and the second switching transistor is an NPN transistor.

7. The short-circuit protection circuit as described in any one of claims 2-6, characterized in that, The comparison unit is a voltage regulator or a comparator.

8. The short-circuit protection circuit as described in claim 7, characterized in that, When the comparison unit is a voltage regulator, the third terminal of the comparison unit is grounded; The voltage regulator is used to pull down the voltage at the base of the first switching transistor to turn on the first switching transistor when the voltage at the second terminal of the comparator is greater than the preset comparison voltage threshold of the voltage regulator. When the comparison unit is a comparator, the short-circuit protection module further includes an eighth resistor and a ninth resistor. The third terminal of the comparison unit is connected to the first terminal of the eighth resistor and the first terminal of the ninth resistor. The second terminal of the eighth resistor is connected to the reference voltage terminal of the control module, and the second terminal of the ninth resistor is grounded. The comparator is used to pull down the voltage at the base of the first switch transistor to turn on the first switch transistor when the voltage at the second terminal of the comparator unit is greater than the voltage at the third terminal of the comparator unit.

9. The short-circuit protection circuit as described in claim 1, characterized in that, The primary-side driving module includes a primary-side sampling unit and a primary-side driving unit. The primary-side sampling unit includes a first sampling resistor, a third capacitor, and a tenth resistor. The primary-side driving unit includes a power switch and an eleventh resistor. The primary winding is connected to the first terminal of the power switch transistor, the second terminal of the power switch transistor is connected to the first terminal of the eleventh resistor, and the second terminal of the eleventh resistor is connected to the output terminal of the control module. The third terminal of the power switch is connected to the first terminal of the first sampling resistor and the first terminal of the tenth resistor. The second terminal of the first sampling resistor is connected to the first terminal of the third capacitor. The two terminals of the third capacitor and the second terminal of the tenth resistor are connected to the primary side sampling terminal. The primary-side sampling unit is used to detect the primary-side voltage of the primary-side winding.

10. The short-circuit protection circuit as described in claim 1, characterized in that, The secondary feedback module is used to convert the secondary voltage of the secondary winding into a secondary current and to feed the secondary current back to the feedback terminal.

11. The short-circuit protection circuit as described in claim 1, characterized in that, The feedback terminal of the control module includes a feedback interface, a current source, and a second sampling resistor; The first end of the second sampling resistor is connected to the current source and the feedback interface, the second end of the second sampling resistor is grounded, and the feedback interface is connected to the short-circuit protection module and the secondary feedback module; The control module is used to detect the feedback voltage generated by the secondary current of the secondary feedback module in the second sampling resistor.

12. A flyback power supply, characterized in that, The flyback power supply includes a short-circuit protection circuit as described in any one of claims 1 to 10.

13. An inverter, characterized in that, The inverter includes a short-circuit protection circuit as described in any one of claims 1 to 10.

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