Solid-state direct current overcurrent protection circuit

Abstract

The invention relates to a solid-state direct current overcurrent protection circuit. A direct current power supply is connected with the negative pole of a free-wheeling diode and one end of a load.The other end of the load is connected with the base of a second NPN transistor through a current limiting resistor and a recovery switch, wherein the current limiting resistor and the recovery switchare connected in series. The collector of the second NPN transistor is connected with the direct current power supply through a pull-up resistor. The emitter of the second NPN transistor is connectedwith the gate of a switch tube of the transistor type through a sampling resistor, and is connected with the positive pole of the free-wheeling diode and the other end of the load through the drain of the switch tube. The drain of the switch tube is connected with the base of a first NPN transistor. The emitter of the first NPN transistor is connected with the negative pole of the direct currentpower supply, and the collector is connected with the source of the switch tube. A zener diode and pull-down resistor, which are parallel, are arranged between the base of the first NPN transistor andthe source of the switch tube. According to the invention, the solid-state direct current overcurrent protection circuit has the advantages of simple structure, wide applicable voltage range and short operation time, can be redesigned according to actual occasions by flexibly changing parameters, and has a self-locking function.

Description

technical field [0001] The invention relates to a circuit structure, in particular to a solid-state direct current overcurrent protection circuit. Background technique [0002] At present, many power supply products have over-current protection function, which reflects the important position of over-current protection in power supply safety. The existing over-current protection methods mainly include: 1. Use air switches. 2. Use a switching power supply chip with overcurrent protection for power supply design. 3. Connect the fuse in series. 4 series self-recovery fuses. [0003] The disadvantages of the above schemes are: 1. Air switch: because it is a mechanical structure, an arc may be generated when tripping, so frequent protection actions will greatly reduce the life of the air switch. 2. Use a switching power supply chip with overcurrent protection for power supply design: the structure is complex, and a large number of calculations are required for each design. 3. ...

AI Technical Summary

Problems solved by technology

[0003] The defects of the above schemes are: 1. Air switch: because it is a mechanical structure, an arc may be generated when tripping, so frequent protection actions will greatly reduce the life of the air switch

2. Use a switching power supply chip with overcurrent protection for power supply design: the structure is complex, and a large number of calculations are required for each design

3. Series fuse: The fuse is a one-time use component, and it will be scrapped every time the protection action is used, which is uneconomical

4 Self-recovery fuse: It is a good alternative to traditional fuses, but the withstand voltage is not high, and it is very limited in high-voltage and high-power occasions

[0004] Generally speaking, the above schemes all have the problem of low flexibility. Every time the parameters are changed, they must be redesigned, or even replaced with different types of components, which brings great inconvenience to users.

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