阅读说明：本技术 一种短路保护电路 (Short-circuit protection circuit ) 是由 林友记 俞伟军 陈耀 于 2020-03-31 设计创作，主要内容包括：本发明公开了一种短路保护电路,包括保护开关模块、开机驱动模块、光耦检测驱动模块,延迟锁死模块和防倒灌二极管,光耦检测驱动模块将现有技术的短路检测模块及保护开关驱动模块合并,由光耦检测驱动模块检测负载两端的电压判定是否发生短路,在负载正常时导通保护开关模块,在负载短路时,切断保护开关模块的驱动,达到短路保护的目的。本发明由于增加了开机驱动模块,解决了开机时光耦无法导通的问题；增加了延迟锁死模块,在光耦正常导通后,切断开机驱动信号,由光耦检测输出电压情况,实现短路锁死保护。本发明检测及驱动信号均由光耦检测驱动模块完成,可简化电路,节约成本。(The invention discloses a short-circuit protection circuit, which comprises a protection switch module, a starting drive module, an optical coupling detection drive module, a delay locking module and a backflow prevention diode, wherein the optical coupling detection drive module combines the short-circuit detection module and the protection switch drive module in the prior art, the optical coupling detection drive module detects the voltage at two ends of a load to judge whether short circuit occurs or not, the protection switch module is switched on when the load is normal, and the drive of the protection switch module is switched off when the load is short-circuited, so that the purpose of short-circuit protection is achieved. The invention solves the problem that the optical coupler can not be conducted when the computer is started up due to the addition of the starting-up driving module; the delay locking module is added, after the optical coupler is normally switched on, a starting driving signal is cut off, the output voltage condition is detected by the optical coupler, and short circuit locking protection is realized. The detection and the driving signal are both completed by the optical coupling detection driving module, so that the circuit can be simplified, and the cost is saved.)

1. A short-circuit protection circuit, characterized by:

the device comprises a protection switch module, a starting drive module, an optocoupler detection drive module, a delay locking module and a backflow prevention diode;

the input end of the start-up driving module and the input end of the optocoupler detection driving module are both used for being simultaneously connected with the output positive end of the switching power supply and the load interface positive end, and the output end of the start-up driving module is simultaneously connected with the anode of the anti-backflow diode and the input end of the delay locking module; the output end of the delay locking module is connected with the negative output end of the switching power supply; the control output end of the optocoupler detection driving module is simultaneously connected with the cathode of the backflow prevention diode and the control end of the protection switch module, and the detection output end of the optocoupler detection driving module is used for being connected with the negative end of the load interface; one end of the protection switch module is connected with the negative end of the output of the switch power supply, and the other end of the protection switch module is connected with the negative end of the load interface;

the protection switch module is used for switching on or switching off a power supply loop of the output negative end of the switching power supply and the load interface negative end;

the startup driving module is used for leading a voltage signal of the output positive end of the switching power supply to the control end of the protection switch module through the backflow prevention diode when the switching power supply is started, so that the protection switch module works, and the optical coupling detection driving module is switched on and starts to work;

the optical coupling detection driving module is used for detecting the voltage at two ends of the load after the switching power supply is started and providing a driving signal for the protection switch module;

the delay locking module is used for pulling down a voltage signal provided by the starting drive module to the control end of the protection switch module and continuously locking after the switching power supply is started, so that the protection switch module is ensured to be independently detected and controlled by the optical coupler during normal work.

2. The short-circuit protection circuit of claim 1, wherein: the protection switch module comprises an N-channel MOS tube Q4 and a resistor R14, the grid electrode of the N-channel MOS tube Q4 is connected with one end of the resistor R14 and then is a control end of the protection switch module, the source electrode of the N-channel MOS tube Q4 is connected with the other end of the resistor R14 and then is one end of the protection switch module, and the drain electrode of the N-channel MOS tube Q4 is the other end of the protection switch module.

3. The short-circuit protection circuit of claim 1, wherein: the protection switch module comprises an N-channel MOS tube Q4, a resistor R14 and a relay K1, a control end of the protection switch module is arranged after the grid of the N-channel MOS tube Q4 is connected with one end of the resistor R14, a first control end of the relay K1 is connected with the drain of the N-channel MOS tube Q4, a second control end of the relay K1 is connected with the positive end of the output of the switch power supply, the source of the N-channel MOS tube Q4, the other end of the resistor R14 and the first electrifying end of the relay K1 are jointly connected and then are one end of the protection switch module, and the second electrifying end of the relay K1 is the other end of the protection switch module.

4. The short-circuit protection circuit of claim 1, wherein: the boot-up driving module comprises a resistor R7, one end of the resistor R7 is an input end of the boot-up driving module, and the other end of the resistor R7 is an output end of the boot-up driving module.

5. The short-circuit protection circuit of claim 1, wherein: the optical coupler detection driving module comprises an optical coupler U1, a resistor R1 and a resistor R4; one end of the resistor R1 is connected with one end of the resistor R4 and then serves as an input end of the optocoupler detection driving module, and the other end of the resistor R4 is connected with a triode collector inside the optocoupler U1; the other end of the resistor R1 is connected with an anode of an internal light emitting diode of the optocoupler U1, and a cathode of the light emitting diode in the optocoupler U1 is a detection output end of the optocoupler detection driving module; and a triode emission electrode in the optocoupler U1 is a control output end of the optocoupler detection driving module.

6. The short-circuit protection circuit of claim 1, wherein: the delay locking module comprises an N-channel MOS tube Q3; the grid electrode of the N-channel MOS tube Q3 is used for inputting a delay locking signal, the drain electrode of the N-channel MOS tube Q3 is the input end of the delay locking module, and the source electrode of the N-channel MOS tube Q3 is the output end of the delay locking module.

7. The short-circuit protection circuit of claim 6, wherein: the delay locking signal is generated by a delay locking signal generating circuit, and the delay locking signal generating circuit comprises a voltage detection delay network and a self-locking switch network;

the voltage detection delay network comprises a resistor R5, a resistor R13, a capacitor C1, a T L431 reference source U2 and a resistor R3, wherein one end of the resistor R5 is connected to the positive end of the output of the switching power supply, the other end of the resistor R5 is simultaneously connected with one end of the resistor R13, one end of the capacitor C1 and the reference end of the T L431 reference source U2, the other end of the resistor R13, the other end of the capacitor C1 and the anode of the T L431 reference source U2 are commonly connected to the negative end of the output of the switching power supply, one end of the resistor R3 is connected with the positive end of the output of the switching power supply, and the other end of the resistor R3 is connected with the cathode;

the latching switch network includes: the transistor Q1, the MOS transistor Q2, the resistor R2, the resistor R6, the resistor R8, the resistor R11, the capacitor C3, the resistor R12, the resistor R10 and the capacitor C2; one end of the resistor R6 is connected with the cathode of a reference source U2 in the voltage detection delay network, the other end of the resistor R6 is simultaneously connected with one end of the resistor R8 and the base of the triode Q1, and the collector of the triode Q1 is simultaneously connected with one end of the resistor R11, one end of the resistor R12 and one end of the resistor R10; an emitter of the triode Q1 is connected with one end of the resistor R2, and the other end of the resistor R2 is connected to the positive output end of the switching power supply; the other end of the resistor R8 is connected with the drain electrode of the MOS tube Q2, the source electrode of the MOS tube Q2 is connected with the negative output end of the switching power supply, and the base electrode of the MOS tube Q2 is connected with the other end of the resistor R11 and one end of the capacitor C3; the other end of the capacitor C3 and the other end of the resistor R12 are connected to the negative terminal of the output of the switching power supply, the other end of the resistor R10 is connected with one end of the capacitor C2 and outputs a delay locking signal, and the other end of the capacitor C2 is connected with the negative terminal of the output of the switching power supply.

Technical Field

The invention relates to the field of switching power supplies, in particular to an output short-circuit protection circuit of a switching power supply.

Background

In the field of switching power supplies, in order to prevent the power supply from being damaged or causing other potential safety hazards due to output short circuit, an output short circuit protection function is generally required to be added.

In the existing application design of the switching power supply, whether a short circuit occurs is generally determined by detecting a signal related to output current or voltage, and the connection between the power supply and a load is cut off after the short circuit occurs.

In the prior art, a detection module and a driving circuit of a protection switch are usually separated, that is, an output detection circuit and the protection switch drive two independent parts, so that the circuit is complex and the cost is high. For example, the chinese patent application with the application number of 201810195425.0 and the name of "a short-circuit protection circuit" has a voltage stabilizing module, a short-circuit detection module, and a control driving module, which are separated from each other, and require a constant current source and an operational amplifier for voltage comparison, and a driving control IC, which has a complicated circuit and a high cost.

Disclosure of Invention

Therefore, the technical problem to be solved by the present invention is to provide a short circuit protection circuit, which combines a short circuit detection module and a protection switch driving module to simplify the circuit and reduce the cost.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

a short-circuit protection circuit, characterized by:

the device comprises a protection switch module, a starting drive module, an optocoupler detection drive module, a delay locking module and a backflow prevention diode;

the input end of the start-up driving module and the input end of the optocoupler detection driving module are both used for being simultaneously connected with the output positive end of the switching power supply and the load interface positive end, and the output end of the start-up driving module is simultaneously connected with the anode of the anti-backflow diode and the input end of the delay locking module; the output end of the delay locking module is connected with the negative output end of the switching power supply; the control output end of the optocoupler detection driving module is simultaneously connected with the cathode of the backflow prevention diode and the control end of the protection switch module, and the detection output end of the optocoupler detection driving module is used for being connected with the negative end of the load interface; one end of the protection switch module is connected with the negative end of the output of the switch power supply, and the other end of the protection switch module is connected with the negative end of the load interface;

the protection switch module is used for switching on or switching off a power supply loop of the output negative end of the switching power supply and the load interface negative end;

the startup driving module is used for leading a voltage signal of the output positive end of the switching power supply to the control end of the protection switch module through the backflow prevention diode when the switching power supply is started, so that the protection switch module works, and the optical coupling detection driving module is switched on and starts to work;

the optical coupling detection driving module is used for detecting the voltage at two ends of the load after the switching power supply is started and providing a driving signal for the protection switch module;

the delay locking module is used for pulling down a voltage signal provided by the starting drive module to the control end of the protection switch module and continuously locking after the switching power supply is started, so that the protection switch module is ensured to be independently detected and controlled by the optical coupler during normal work.

As a specific embodiment of the protection switch module, the protection switch module is characterized in that: the protection switch module comprises an N-channel MOS tube Q4 and a resistor R14, wherein a control end of the protection switch module is arranged after a grid electrode of the N-channel MOS tube Q4 is connected with one end of the resistor R14, a source electrode of the N-channel MOS tube Q4 is connected with the other end of the resistor R14 and then is one end of the protection switch module, and a drain electrode of the N-channel MOS tube Q4 is the other end of the protection switch module.

As another specific embodiment of the protection switch module, the protection switch module is characterized in that: including N channel MOS pipe Q4, resistance R14 and relay K1, be the control end of protection switch module after the grid of N channel MOS pipe Q4 is connected with resistance R14's one end, the first control end of relay K1 is connected to N channel MOS pipe Q4's drain electrode, the second control end connection switch power output positive terminal of relay K1, N channel MOS pipe Q4's source electrode, be the one end of protection switch module after the other end of resistance R14 and the first power-on end of relay K1 connect jointly, the second power-on end of relay K1 is the other end of protection switch module.

As a specific implementation manner of the boot drive module, the method is characterized in that: the power-on driving circuit comprises a resistor R7, wherein one end of the resistor R7 is an input end of a power-on driving module, and the other end of the resistor R7 is an output end of the power-on driving module.

As a concrete implementation mode of opto-coupler detection drive module, its characterized in that: the circuit comprises an optical coupler U1, a resistor R1 and a resistor R4; one end of the resistor R1 is connected with one end of the resistor R4 and then serves as an input end of the optocoupler detection driving module, and the other end of the resistor R4 is connected with a triode collector inside the optocoupler U1; the other end of the resistor R1 is connected with an anode of an internal light emitting diode of the optocoupler U1, and a cathode of the light emitting diode in the optocoupler U1 is a detection output end of the optocoupler detection driving module; and a triode emission electrode in the optocoupler U1 is a control output end of the optocoupler detection driving module.

The specific implementation mode of the delay locking module is characterized in that: comprises an N-channel MOS tube Q3; the grid electrode of the N-channel MOS tube Q3 is used for inputting a delay locking signal, the drain electrode of the N-channel MOS tube Q3 is the input end of the delay locking module, and the source electrode of the N-channel MOS tube Q3 is the output end of the delay locking module.

Furthermore, the delay locking signal is generated by a delay locking signal generating circuit, and the delay locking signal generating circuit comprises a voltage detection delay network and a self-locking switch network;

the voltage detection delay network comprises a resistor R5, a resistor R13, a capacitor C1, a T L431 reference source U2 and a resistor R3, wherein one end of the resistor R5 is connected to the positive end of the output of the switching power supply, the other end of the resistor R5 is simultaneously connected with one end of the resistor R13, one end of the capacitor C1 and the reference end of the T L431 reference source U2, the other end of the resistor R13, the other end of the capacitor C1 and the anode of the T L431 reference source U2 are commonly connected to the negative end of the output of the switching power supply, one end of the resistor R3 is connected with the positive end of the output of the switching power supply, and the other end of the resistor R3 is connected with the cathode;

the latching switch network includes: the transistor Q1, the MOS transistor Q2, the resistor R2, the resistor R6, the resistor R8, the resistor R11, the capacitor C3, the resistor R12, the resistor R10 and the capacitor C2; one end of the resistor R6 is connected with the cathode of a reference source U2 in the voltage detection delay network, the other end of the resistor R6 is simultaneously connected with one end of the resistor R8 and the base of the triode Q1, and the collector of the triode Q1 is simultaneously connected with one end of the resistor R11, one end of the resistor R12 and one end of the resistor R10; an emitter of the triode Q1 is connected with one end of the resistor R2, and the other end of the resistor R2 is connected to the positive output end of the switching power supply; the other end of the resistor R8 is connected with the drain electrode of the MOS tube Q2, the source electrode of the MOS tube Q2 is connected with the negative output end of the switching power supply, and the base electrode of the MOS tube Q2 is connected with the other end of the resistor R11 and one end of the capacitor C3; the other end of the capacitor C3 and the other end of the resistor R12 are connected to the negative terminal of the output of the switching power supply, the other end of the resistor R10 is connected with one end of the capacitor C2 and outputs a delay locking signal, and the other end of the capacitor C2 is connected with the negative terminal of the output of the switching power supply.

According to the short-circuit protection circuit, under the condition that the load of a switching power supply is normal, the pressure difference between the input end and the detection output end of an optical coupling detection driving module is normal, an internal light emitting diode is conducted to emit light, and after an internal phototriode receives a light signal, a driving signal is provided to the control end of a protection switch module, so that the protection switch module works, and a power supply loop of the output negative end of the switching power supply and the load interface negative end is switched on; when a short-circuit event occurs, the pressure difference between the input end and the detection output end of the optical coupling detection driving module is zero, the internal light-emitting diode is not bright, the phototriode is cut off, the protection switch module is lost, the protection switch module does not work, the power supply loop of the output negative end of the switch power supply and the power supply loop of the load interface negative end are cut off, and short-circuit protection is rapidly realized. The invention solves the problem that the optical coupler can not be conducted when the computer is started up due to the addition of the starting-up driving module; the delay locking module is added, after the optical coupler is normally switched on, a starting driving signal is cut off, the output voltage condition is detected by the optical coupler, and short circuit locking protection is realized.

Compared with the prior art, the invention detects whether the output is short-circuited and provides the driving signal for the protection switch module after the switching power supply is started, and the detection and the driving circuit can be simplified and the cost can be reduced.

Drawings

Fig. 1 is a schematic block diagram of a short-circuit protection circuit according to an embodiment of the present invention;

fig. 2-1 is a schematic diagram of a short-circuit protection circuit according to a first embodiment of the present invention;

fig. 2-2 is a schematic diagram of a delay locked signal generating circuit according to a first embodiment of the present invention;

fig. 3 is a schematic diagram of a short-circuit protection circuit according to a second embodiment of the present invention.

Detailed Description

The circuit of the present invention will be described with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the inventive circuit.

Referring to fig. 1, fig. 1 is a schematic block diagram of a short-circuit protection circuit according to the present invention. The system comprises an optical coupling detection driving module 11, a protection switch module 12, a starting driving module 13, a delay locking module 14 and a backflow prevention diode D1. The input end of the start-up driving module 13 and the input end of the coupling detection driving module 11 are both used for simultaneously connecting the output positive end of the switching power supply and the positive end of the load interface, and the output end of the start-up driving module 13 is simultaneously connected with the anode of the backflow prevention diode D1 and the input end of the delay locking module 14; the output end of the delay locking module 14 is connected with the output negative end GND of the switching power supply; the control output end of the optical coupling detection driving module 11 is simultaneously connected with the cathode of the backflow prevention diode D1 and the control end of the protection switch module 12, and the detection output end of the optical coupling detection driving module 11 is used for being connected with the negative end of the load port; one end of the protection switch module 12 is connected to the negative terminal GND of the switch power supply output, and the other end of the protection switch module 12 is connected to the negative terminal of the load port.

First embodiment

Referring to fig. 2-1, fig. 2-1 is a schematic diagram of a short-circuit protection circuit 1 according to a first embodiment of the present invention, and the functional modules are composed and connected as follows:

the protection switch module 12 includes an N-channel MOS transistor Q4, a resistor R14, a control terminal of the protection switch module 12 is connected between a gate of the N-channel MOS transistor Q4 and one end of the resistor R14, an end of the protection switch module 12 is connected between a source of the N-channel MOS transistor Q4 and the other end of the resistor R14, and a drain of the N-channel MOS transistor Q4 is the other end of the protection switch module 12.

The start-up driving module 13 includes a resistor R7, one end of the resistor R7 is connected to the positive output terminal VO + of the switching power supply to serve as an input terminal of the start-up driving module 13, and the other end of the resistor R7 is connected to the anode of the back-flow prevention diode D1 and the input terminal of the delay locking module 14 to serve as an output terminal of the start-up driving module 13.

The optical coupler detection driving module 11 comprises an optical coupler U1, a resistor R1 and a resistor R4. One end of the resistor R1 and one end of the resistor R4 are connected to the positive output terminal VO + of the switching power supply in common and serve as the input end of the optical coupling detection driving module 11; the other end of the resistor R1 is connected with the anode of an internal light-emitting diode of the optocoupler U1; the cathode of a light emitting diode in the optocoupler U1 is connected with the negative end VO-of the load port to serve as the detection output end of the optocoupler detection driving module 11; an emitter of a triode in the optocoupler U1 is connected with the control end of the protection switch module 12 to serve as the control output end of the optocoupler detection driving module 11; the other end of the resistor R4 is connected with the collector of the triode in the optocoupler U1.

The delay locked module 14 includes an N-channel MOS transistor Q3. The grid electrode of the N-channel MOS tube Q3 is connected with a delay locking signal, and the drain electrode of the N-channel MOS tube Q3, the output end of the start-up driving module 13 and the anode of the backflow prevention diode D1 are connected together to be used as the input end of the delay locking module; the drain of the N-channel MOS transistor Q3 is connected to the negative terminal GND of the switching power supply as the other terminal of the delay locked module 14.

The core device of the embodiment is the optical coupling detection driving module 11, the optical coupling detection driving module 11 provides a driving signal for the MOS transistor Q4 while detecting the voltage at two ends of the load R L, the driving signal is normally provided when the voltage at two ends of the load R L is normal, the driving signal is stopped to be provided when the voltage at two ends of the load is zero, and the detection and driving circuit is simple and reliable.

The detailed working principle analysis of the embodiment is as follows:

detect the detection of drive module 11 completion load both ends voltage by the opto-coupler, whether have voltage to judge whether take place the short circuit through detecting the load both ends, work normally like the load, do not take place short circuit trouble promptly, there is voltage at the load both ends, then 1 foot of emitting diode (being the positive pole) of opto-coupler U1, 2 foot (being the negative pole) have the electric current to flow through, 3 feet of phototriode (being the projecting pole) that make opto-coupler U1, 4 feet (being the collecting electrode) switch on, will provide drive signal to N channel MOS pipe Q4, make N channel MOS pipe Q4 switch on, make the load can normally insert the power output end. If the two ends of the load are short-circuited, the voltage at the two ends of the load is zero, the light emitting diode of the optical coupler does not have current, the 3 pins and the 4 pins of the phototriode of the U1 of the optical coupler are cut off, a driving signal cannot be added to the switch of the N-channel MOS tube Q4, the N-channel MOS tube Q4 is cut off, and the load is disconnected with the negative output end of the switching power supply, so that short-circuit protection is realized.

Considering that before the N-channel MOS transistor Q4 is turned on, a current loop is not established, even if the load is not short-circuited, the voltage at two ends of the load is still zero, and the light emitting diode of the optocoupler U1 cannot be turned on, so the start-up driving module 13 is added in the present application, when the vehicle is started, a VO + voltage signal is introduced to the gate of the N-channel MOS transistor through the anti-backflow diode D1, so that the N-channel MOS transistor is turned on, the voltage at two ends of the load is normal, and the light emitting diode of the optocoupler U1 is normally turned on, and the optocoupler U1 provides a driving signal to the gate of the N-channel.

Considering that after the N-channel MOS transistor is turned on by the start-up driving module 13, in order to enable the optical coupler U1 to detect the load end voltage and provide a driving signal solely by the optical coupler U1, the application adds the delay locking module 14 to pull down the voltage signal for driving the N-channel MOS transistor provided by the start-up driving module 13 and continuously lock and pull down, thereby ensuring that the N-channel MOS transistor is detected solely by the optical coupler and controlled during normal operation.

Fig. 2-2 shows the delay lock-up signal generating circuit 141 of the present embodiment, which includes a voltage detection delay network and a self-locking switch network, wherein the voltage detection delay network includes a resistor R5, a resistor R13, a capacitor C1, a T L431 reference source U2 and a resistor R3, and the self-locking switch network includes a triode Q1, a MOS transistor Q2, a resistor R2, a resistor R6, a resistor R8, a resistor R11, a capacitor C3, a resistor R12, a resistor R10 and a capacitor C2.

One end of a resistor R is connected to a positive output end VO + of the switching power supply, the other end of the resistor R is connected with one end of the resistor R, one end of a capacitor C and the 1 st pin of the reference end of a T431 reference source U, the other end of the resistor R, the other end of the capacitor C and the 3 rd pin of the anode of the T431 reference source U are connected to the negative output end of the switching power supply together, one end of the resistor R is connected with the output end of the switching power supply, the other end of the resistor R is connected with the positive end of the resistor R and the 2 nd pin of the cathode of the reference source U, the other end of the resistor R is connected with one end of the resistor R and the base of a triode Q, the collector of the triode Q is connected with one end of the resistor R, one end of the resistor R and one end of the resistor R, the emitter of the triode Q is connected with one end of the resistor R, the other end of the resistor R is connected with the output end of the switching power supply, the other end of the resistor R is connected with the drain of the MOS tube Q, the drain of the MOS tube Q is connected with the negative output end of the switching power supply, the resistor R is connected with the negative output end of the switch, and the capacitor.

When the power-on device is started, the output voltage VO + of the positive output end of the switching power supply charges C1 through a resistor R5 and a resistor R13, and the charging time of C1 is the required delay time; after the voltage at the two ends of the C1 reaches the reference voltage of the reference source U2, the 2 nd pin (namely the cathode) of the reference source U2 is pulled down, the 2 nd pin of the reference source U2 pulls down the 1 st pin (namely the base) of the triode Q1 through the current limiting resistor R6, so that the triode Q1 is turned on, the VCC voltage is introduced into the gate of the MOS transistor Q2 through the current limiting resistors R2, R11 and the voltage dividing resistor R12, the gate of the MOS transistor Q2 is at a high level, the MOS transistor Q2 is turned on, and a delay locking signal is output to the MOS transistor Q3 through the current limiting resistor R10; the conduction of the MOS tube Q2 pulls down the 1 st pin of the triode Q1 through the current-limiting resistor R8, so that the triode Q1 is continuously conducted, the deadlock signal is continuously provided to the MOS tube Q3, the triode Q1 and the MOS tube Q2 are mutually triggered and conducted, the status of continuous deadlock is formed, and the deadlock signal is continuously provided to the MOS tube Q3.

Second embodiment

Referring to fig. 3, fig. 3 is a schematic diagram of a short-circuit protection circuit according to a second embodiment of the invention. As shown in fig. 3, the protection switch module 12 of the second embodiment includes an N-channel MOS transistor Q4, a resistor R14, and a relay K1, as compared to the first embodiment. The protection switch module of the second embodiment is composed and connected as follows:

the grid of N channel MOS pipe Q4 and the 3 rd pin of resistance R14 are connected to the negative pole of preventing flowing backward diode D1 and opto-coupler U1 jointly and are regarded as the control end of protection switch module, the drain electrode of N channel MOS pipe Q4 is connected with the first control end of relay K1, the second control end and the switching power supply output of relay K1 are connected, the source electrode of N channel MOS pipe Q4, the other end of resistance R14 and the first power-on end of relay K1 are connected to the switching power supply output negative terminal jointly and are regarded as the one end of protection switch module, the second power-on end and the load interface negative terminal of relay K1 are connected and are regarded as the other end of protection switch module.

The start-up driving module 13, the optical coupling detection driving module 11, the delay locking module 14 and the backflow prevention diode D1 in the second embodiment are the same as those in the first embodiment, and the working principle of the protection switch module is as follows:

the optical coupling detection control module 11 controls an N-channel MOS tube Q4 by detecting the short circuit condition of a load, when the N-channel MOS tube Q4 is conducted, the control end of a relay K1 is electrified, the electrified end of a relay K1 is conducted, and the load is connected into a power supply; when the N-channel MOS tube Q4 is turned off, the control end of the relay K1 is not electrified, and the electrified end of the relay is disconnected, so that the connection between the load and the power supply is disconnected.

The core device of the detection driving module of the second embodiment is still an optical coupler, the detection and control logic of the detection driving module is unchanged, only the relay driving tube is added, the working principle is the same as that of the first embodiment, and the same effect can be achieved.

It can be seen from the above embodiments that, in the short-circuit protection circuit provided by the present invention, the optical coupler detection driving module 11 is adopted to combine the short-circuit detection module and the protection switch driving module in the prior art, the optical coupler detection driving module 11 detects the voltages at the two ends of the load to determine whether a short circuit occurs, the protection switch module 12 is turned on when the load is normal, and the driving of the protection switch module 12 is turned off when the load is short-circuited, so as to achieve the purpose of short-circuit protection. The detection and the driving signal are provided by the optical coupling detection driving module 11, so that the circuit can be simplified, and the cost is saved.

The above-described embodiments of the present invention are not intended to limit the scope of the present invention, and the embodiments of the present invention are not limited thereto, and various other modifications, substitutions and alterations can be made to the above-described structure of the present invention without departing from the basic technical concept of the present invention as described above, according to the common technical knowledge and conventional means in the field of the present invention.