Power supply output protection circuit and system

Abstract

The utility model provides a power supply output protection circuit, which comprises a control circuit and a power supply chip, the control circuit is connected with the positive electrode of the output end of a power supply and is periodically opened and closed in response to the output voltage of the power supply, the power supply chip comprises a power supply end, and the power supply end is connected with the control circuit. The power supply output protection circuit provided by the utility model is low in cost, high in efficiency, high in reliability, easy to adjust, wide in application and beneficial to prolonging the service life of the power supply.

Description

[Technical field]

[0001] The utility model belongs to the technical field of power supply, and in particular relates to a power supply output protection circuit and system. [Background technology]

[0002] In electronic circuits, short circuit is a common type of fault. When the power supply and line in the circuit are short-circuited, the current will suddenly increase, which may cause damage to circuit components and lines, or even cause safety hazards such as fire. In order to avoid this phenomenon, short circuit protection is widely used in electronic circuits.

[0003] See also Figure 1 , which is a schematic diagram of a short-circuit protection circuit in the prior art. Before power-on, the initial voltage of capacitor C11 is zero; at the moment of power-on, the input power supply is grounded through capacitor C11, resistor R33, and base b of transistor Q11, forming a charging circuit for capacitor C11; the charging current of capacitor C11 flows through base b of transistor Q11, transistor Q11 is turned on, MOS is turned on, and the output power supply is supplied. When a short-circuit fault occurs at the output power supply end, the output power supply voltage decreases, diode D11 is turned off, base b of transistor Q11 has no holding current, transistor Q11 is turned off, no current flows through resistors R11 and R22, the voltage difference Vgs between gate G and source S of MOS tube M11 is close to zero volts, MOS tube M11 is turned off, input and output power are disconnected, and short-circuit protection is achieved.

[0004] However, when the fault is eliminated, the short-circuit protection state continues to be maintained, and the input power supply will not restore the output power supply. It is necessary to turn off the input power supply and then turn on the input power supply to restore the output, which is inconvenient to use. [Utility Model Content]

[0005] In order to solve the technical problem that the short-circuit protection circuit in the prior art is inconvenient to use, the utility model provides a power supply output protection circuit and system, which can automatically release the short-circuit protection state and is easy to use.

[0006] The utility model provides a power supply output protection circuit, comprising a control circuit and a power supply chip, wherein the control circuit is connected to the positive pole of the output end of the power supply and is periodically turned on and off in response to the output voltage of the power supply, and the power supply chip comprises a power supply end, which is connected to the control circuit.

[0007] In one embodiment, the control circuit includes a feedback circuit and a switch circuit, the feedback circuit is connected to the positive output terminal of the power supply and the positive input terminal of the power supply, and the switch circuit is connected to the feedback circuit and the power supply terminal.

[0008] In one embodiment, the feedback circuit includes an isolation optocoupler, a charging resistor, and a charging capacitor. The positive pin of the emitter of the isolation optocoupler is connected to the positive output terminal of the power supply, the negative pin of the emitter of the isolation optocoupler is connected to the negative output terminal of the power supply, the emitter of the receiver of the isolation optocoupler is connected to the common ground terminal of the power supply chip, the collector of the receiver of the isolation optocoupler is connected to the first end of the charging resistor and the first end of the charging capacitor, the second end of the charging resistor is connected to the positive input terminal of the power supply, and the second end of the charging capacitor is connected to the common ground terminal of the power supply chip.

[0009] In one embodiment, the feedback circuit includes a triode, a charging resistor, and a charging capacitor. The base of the triode is connected to the positive output terminal, the collector of the triode is connected to the first end of the charging resistor and the first end of the charging capacitor, the emitter of the triode Q1 is connected to the common ground terminal of the power supply chip, the second end of the charging resistor is connected to the positive input terminal of the power supply, and the second end of the charging capacitor is connected to the common ground terminal of the power supply chip.

[0010] In one embodiment, the charging resistor includes a first charging resistor and a second charging resistor connected in series.

[0011] In one embodiment, the switching circuit includes a trigger diode, a zener diode, a boosting resistor, a discharging resistor, and a switching transistor. The first end of the trigger diode is connected to the first end of the charging capacitor, the second end of the trigger diode is connected to the common ground terminal of the power supply chip, the negative electrode of the zener diode is connected to the first end of the charging capacitor, the positive electrode of the zener diode is connected to the first end of the boosting resistor, the second end of the boosting resistor is connected to the switching transistor, and the first end of the discharging resistor is connected to the switching transistor.

[0012] In one embodiment, the switching transistor is an NPN triode. The base of the triode is connected to the second end of the boosting resistor, the collector of the triode is connected to the power supply terminal, and the emitter of the triode is connected to the common ground terminal of the power supply chip.

[0013] In one embodiment, the trigger voltage of the trigger diode is greater than the breakdown voltage of the zener diode and less than the voltage of the positive input terminal of the power supply, and the breakdown voltage of the zener diode is less than the voltage of the positive input terminal of the power supply.

[0014] In one embodiment, the power supply chip has a soft start function.

[0015] A power output protection system comprises a power supply and a power output protection circuit which are connected and arranged, wherein the power output protection circuit comprises a control circuit and a power chip, wherein the control circuit is connected to the positive pole of the output terminal of the power supply and is turned on or off in response to the output voltage of the power supply, and the power chip comprises a power supply terminal which is connected to the control circuit and is turned off when the control circuit is turned on and is turned on when the control circuit is turned off.

[0016] Compared with the prior art, the power output protection circuit of the utility model detects whether an output short circuit fault occurs through the voltage change of the positive electrode of the output terminal. When a short circuit fault occurs, the voltage of the positive electrode of the output terminal is pulled down to the short circuit voltage, and the short circuit voltage is close to zero. The control circuit starts to open and close periodically in response to the output voltage of the power supply, and controls the power chip to shut down and start periodically through the power supply end, thereby controlling the working state of the power supply, realizing automatic release of the short circuit protection state, and being easy to use. At the same time, the power output protection circuit of the utility model does not require a sampling resistor to detect a short circuit fault, has high efficiency and reliability, and instantaneous heavy load will not trigger false protection.

Brief Description of the Drawings

[0017] Figure 1 It is a schematic diagram of a short-circuit protection circuit in the prior art;

[0018] Figure 2 This is a schematic diagram of the structure of a power output protection system provided by the utility model:

[0019] Figure 3 A schematic diagram of a power output protection circuit provided by the utility model;

[0020] Figure 4 for Figure 3 A schematic diagram of another embodiment of a feedback circuit is shown;

[0021] Figure 5 for Figure 3 The schematic diagram of voltage changes of Vout, point A, point B and Vcc when the power output protection circuit is working is shown. [Specific implementation method]

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0023] See also Figure 2, which is a schematic structural diagram of a power output protection system provided by the present utility model. The power output protection system 1 includes a power output protection circuit 100 and a power supply 200. The power output protection circuit 100 is connected to the power supply 200 to perform short-circuit protection on the power supply 200. The protection circuit 100 includes a control circuit 10 and a power supply chip 30. The control circuit 10 is periodically turned on and off in response to the output voltage of the power supply 200. The power supply chip 30 includes a power supply terminal Vcc, and the power supply terminal Vcc is connected to the control circuit 10, and is turned off when the control circuit 10 is turned on, and is started when the control circuit 10 is turned off. The control circuit 10 includes a feedback circuit 11 and a switching circuit 14. The feedback circuit 11 is connected to the positive terminal Vout of the output of the power supply 200 and the positive terminal Vin of the input of the power supply 200. The switching circuit 14 is connected to the feedback circuit 11 and the power supply terminal Vcc of the power supply chip 30.

[0024] Please refer to Figure 3 , which is a schematic diagram of a power output protection circuit provided by the present utility model. The feedback circuit 11 includes an output resistor R1, an isolation optocoupler G1, a charging resistor, and a charging capacitor C1. The positive terminal pin of the emitter of the isolation optocoupler G1 is connected to the positive terminal Vout of the output of the power supply 200 through the output resistor R1. The negative terminal pin of the emitter of the isolation optocoupler G1 is connected to the negative terminal OUT_GND of the output of the power supply 200. The emitter of the receiving end of the isolation optocoupler G1 is connected to the common ground terminal GND of the power supply chip 30. The collector of the receiving end of the isolation optocoupler G1 is connected to the first end of the charging resistor at point A. The collector of the receiving end of the isolation optocoupler G1 is connected to the first end of the charging capacitor C1 at point A. The second end of the charging resistor is connected to the positive terminal Vout of the input of the power supply 200. The second end of the charging capacitor C1 is connected to the common ground terminal GND of the power supply chip 30.

[0025] In this embodiment, the number of the charging resistors is two, which are a first charging resistor R2 and a second charging resistor R3 respectively, and the first charging resistor R2 and the second charging resistor R3 are connected in series.

[0026] The switch circuit 14 includes a trigger diode D1, a voltage stabilizing diode ZD1, a boosting resistor R4, a discharging resistor R5, a switching transistor Q1, and a power supply resistor R6. The first end of the trigger diode D1 is connected to the first end of the charging capacitor C1 at point A. The second end of the trigger diode D1 is connected to the common ground terminal GND of the power supply chip 30. The negative electrode of the voltage stabilizing diode ZD1 is connected to the first end of the charging capacitor C1 at point A. The positive electrode of the voltage stabilizing diode ZD1 is connected to the first end of the boosting resistor R4 at point B. The second end of the boosting resistor R4 is connected to the switching transistor Q1. The first end of the discharging resistor R5 is connected to the switching transistor Q1. The second end of the discharging resistor R5 is connected to the common ground terminal GND of the power supply chip 30.

[0027] The switching transistor Q1 is an NPN triode. The base of the switching transistor Q1 is connected to the second end of the boosting resistor R4 and also connected to the first end of the discharging resistor R5. The collector of the switching transistor Q1 is connected to the power supply terminal Vcc of the power supply chip 30 through the power supply resistor R6. The emitter of the switching transistor Q1 is connected to the common ground terminal GND of the power supply chip 30.

[0028] Wherein, the trigger voltage of the trigger diode D1 is greater than the breakdown voltage of the voltage stabilizing diode ZD1 and less than the voltage of the positive electrode Vin of the input end of the power supply 200. The breakdown voltage of the voltage stabilizing diode ZD1 is also less than the voltage of the positive electrode Vin of the input end of the power supply 200.

[0029] It can be understood that the isolation optocoupler G1 is used for isolated output. In some embodiments, the isolation optocoupler G1 can be replaced by a triode Q2 for non-isolated output. As Figure 4 shown, the base of the triode Q2 is connected to the positive electrode Vout of the output end. The collector of the triode Q2 is connected to the first end of the charging resistor at point A. The collector of the triode Q2 is connected to the first end of the charging capacitor C1 at point A. The emitter of the triode Q2 is connected to the common ground terminal GND of the power supply chip 30.

[0030] In one embodiment, the power supply chip 30 has a soft start function.

[0031] The above combination Figure 2 and Figure 3 is used to illustrate the power output protection circuit provided by the embodiment of the present invention. Next, the working principle of the power output protection circuit provided by the present invention will be described in conjunction with Figure 5 The working principle of the power output protection circuit provided by the present invention will be described.

[0032] The power output protection circuit 100 includes a normal working state and a short-circuit fault working state.

[0033] Normal operating state: The power supply 200 outputs a normal voltage, the voltage of the positive terminal Vout of the output is normal, the isolation optocoupler G1 works, the voltage at point A is pulled down, lower than the breakdown voltage of the zener diode ZD1, the zener diode ZD1 is not broken down, the switching transistor Q1 is cut off, the control circuit 10 is in the off state, the voltage of the power supply terminal Vcc is within the normal power supply voltage range of the power supply chip 30, and the power supply works stably.

[0034] Short-circuit fault state: The output of the power supply 200 is short-circuited, the voltage of the positive terminal Vout of the output is pulled down to nearly 0V, the isolation optocoupler G1 is cut off, and the positive terminal Vin of the input charges the charging capacitor C1 through the first charging resistor R2 and the second charging resistor R3; the voltage of the charging capacitor C1 rises, the voltage at point A rises, and after time t1, it rises to the sum of the breakdown voltage of the zener diode ZD1, the base conduction voltage of the switching transistor Q1, and the voltage across the boost resistor R4, then the zener diode ZD1 is broken down, the switching transistor Q1 is turned on, the control circuit 10 is in the on state, the voltage of the power supply terminal Vcc is pulled down to the turn-off voltage of the power supply chip 30, the power supply chip 30 is turned off and stops working; due to the existence of the boost resistor R4, the voltage of the charging capacitor C1 continues to rise, the voltage at point A rises, and after time t2, it reaches the trigger voltage of the trigger diode D1, the trigger diode D1 is turned on, the charging capacitor C1 discharges rapidly, the voltage of the charging capacitor C1 drops, the voltage at point A drops, when the voltage of the charging capacitor C1 drops to the sum of the breakdown voltage of the zener diode ZD1, the base conduction voltage of the switching transistor Q1, and the voltage across the boost resistor R4, the zener diode ZD1 is cut off, the switching transistor Q1 discharges rapidly through the discharge resistor R5 and is cut off, the control circuit 10 returns to the off state, the voltage of the power supply terminal Vcc rises to the start voltage of the power supply chip 30, and the power supply chip 30 starts to work; when the voltage of the charging capacitor C1 drops to the conduction voltage drop value of the trigger diode D1, the positive terminal Vin of the input will charge the charging capacitor C1 through the first charging resistor R2 and the second charging resistor R3 again. In this way, the control circuit 10 is periodically turned on and off, and the power supply chip 30 is periodically turned off and started to achieve short-circuit protection. The power supply chip 30 turns off for time t2 and then works for time t1, running periodically. During the t1 time period, it detects whether the output short-circuit fault is eliminated, and does not work during the t2 time period to protect the power supply 200.

[0035] Wherein, when the short - circuit fault is removed and the power supply chip 30 enters the working state, the voltage of the positive terminal Vout of the output immediately rises, the isolation optocoupler G1 conducts, the voltage of the charging capacitor C1 is pulled down, the voltage at point A is pulled down, the switching transistor Q1 remains in the cut - off state, the control circuit 10 remains in the off state, and the power output protection circuit 100 resumes the normal working state.

[0036] It can be understood that the conduction voltage drop value of the trigger diode D1 is less than the sum of the breakdown voltage of the voltage - stabilizing diode ZD1, the base conduction voltage of the switching transistor Q1, and the voltage across the step - up resistor R4.

[0037] It should be noted that those skilled in the art can change the lengths of t1 time and t2 time by configuring different charging resistors, the charging capacitor C1, the trigger diode D1, and the voltage - stabilizing diode ZD1 to obtain the required t1 time, t2 time, and the period t of the control circuit 10. For example, t1 = 20ms and t2 = 180ms can be configured, then the period t is 200ms. To greatly reduce the damage to the power supply caused by output short - circuit, t1 = 5ms and t2 = 295ms can also be configured, then the period t is 300ms.

[0038] Compared with the prior art, the power output protection circuit 100 of the present utility model has fewer components and a simple circuit structure. It can be connected to the power supply chip 30 through external surface - mounted components to achieve short - circuit protection. When the short - circuit fault is removed, the power supply 200 automatically resumes power supply output, with low cost and convenient use. Secondly, by the voltage change of the positive terminal Vout of the output, it is confirmed whether an output short - circuit fault occurs, without the need for a sampling resistor to detect the short - circuit fault, improving efficiency and having high reliability, and momentary heavy loads will not trigger false protection. Thirdly, after an output short - circuit fault occurs, the working time t1 of the control chip 30, the turn - off time t2 of the control chip 30, and the period t of the control circuit 10 can be conveniently adjusted according to actual needs, which is easy to adjust and widely applicable. Finally, when in the short - circuit fault state, the control circuit 10 is periodically turned on and off, controlling the power supply chip 30 to be periodically turned off and started. Cooperating with the soft - start function of the power supply chip 30, each time the power supply chip 30 starts, it controls the power supply 200 to perform soft - start, which can greatly reduce the damage caused by short - circuit faults to circuit devices.

[0039] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power output protection circuit, characterized in that: include: A control circuit connected to the positive output terminal of the power supply and periodically turned on and off in response to the output voltage of the power supply; The power chip comprises a power supply end, and the power supply end is connected to the control circuit.

2. The power output protection circuit according to claim 1, characterized in that: The control circuit includes a feedback circuit and a switch circuit. The feedback circuit is connected to the positive electrode of the output terminal of the power supply and the positive electrode of the input terminal of the power supply. The switch circuit is connected to the feedback circuit and the power supply terminal.

3. The power output protection circuit according to claim 2, characterized in that: The feedback circuit includes an isolation optocoupler, a charging resistor and a charging capacitor. The positive emitter pin of the isolation optocoupler is connected to the positive output terminal of the power supply, the negative emitter pin of the isolation optocoupler is connected to the negative output terminal of the power supply, the emitter of the isolation optocoupler is connected to the common ground terminal of the power chip, the collector of the receiving end of the isolation optocoupler is connected to the first end of the charging resistor and the first end of the charging capacitor, the second end of the charging resistor is connected to the positive input terminal of the power supply, and the second end of the charging capacitor is connected to the common ground terminal of the power chip.

4. The power output protection circuit according to claim 2, characterized in that: The feedback circuit includes a transistor, a charging resistor and a charging capacitor. The base of the transistor is connected to the positive electrode of the output terminal, the collector of the transistor is connected to the first end of the charging resistor and to the first end of the charging capacitor, the emitter of the transistor Q1 is connected to the common ground terminal of the power chip, the second end of the charging resistor is connected to the positive electrode of the input terminal of the power supply, and the second end of the charging capacitor is connected to the common ground terminal of the power chip.

5. The power output protection circuit according to claim 3 or 4, characterized in that: The charging resistor includes a first charging resistor and a second charging resistor connected in series.

6. The power output protection circuit according to claim 3 or 4, characterized in that: The switching circuit includes a trigger diode, a voltage regulator diode, a boost resistor, a discharge resistor and a switching transistor. The first end of the trigger diode is connected to the first end of the charging capacitor, the second end of the trigger diode is connected to the common ground terminal of the power chip, the cathode of the voltage regulator diode is connected to the first end of the charging capacitor, the anode of the voltage regulator diode is connected to the first end of the boost resistor, the second end of the boost resistor is connected to the switching transistor, and the first end of the discharge resistor is connected to the switching transistor.

7. The power output protection circuit according to claim 6, characterized in that: The switching transistor is an NPN transistor, the base of the transistor is connected to the second end of the boost resistor, the collector of the transistor is connected to the power supply end, and the emitter of the transistor is connected to the common ground end of the power chip.

8. The power output protection circuit according to claim 6, characterized in that: The trigger voltage of the trigger diode is greater than the breakdown voltage of the voltage regulator diode and less than the voltage of the positive electrode of the input end of the power supply. The breakdown voltage of the voltage regulator diode is less than the voltage of the positive electrode of the input end of the power supply.

9. The power output protection circuit according to claim 1, characterized in that: The power chip has a soft start function.

10. A power output protection system, comprising a power supply and a power output protection circuit which are connected to each other, wherein the power output protection circuit is the power output protection circuit according to any one of claims 1 to 9.

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