Over-current protection circuit of direct-current electronic contactor

Abstract

The invention discloses an over-current protection circuit of a direct-current electronic contactor, which is characterized in that a drain electrode of an NMOS switching transistor is connected witha positive electrode of a direct-current power supply, and a source electrode is connected with a negative electrode of the direct-current power supply through a load; and a control signal of a single-chip microcomputer is input into a grid electrode of the NMOS switching transistor through a driving circuit. Multiple paths of the NMOS switching transistor are connected in parallel. The drain electrode of the NMOS switching transistor is connected with a non-inverting input end of a differential amplifier through a relay protection circuit and a differential resistor, the source electrode ofthe NMOS switching transistor is further connected with an inverting input end of the differential amplifier through a relay coil equivalent resistor and a differential resistor, and the output end ofthe differential amplifier is connected with an AD conversion module of the single-chip microcomputer. The driving signal controls the NMOS switching transistor to be switched on. The over-current protection circuit samples voltage at the drain electrode end and the source electrode end of the NMOS switching transistor, and when the voltage exceeds a set threshold value, over-current shutdown protection is performed. The over-current protection circuit is simple in design, the use cost of the circuit can be reduced, and the reliability and the stability of the circuit during working can be improved.

Description

technical field [0001] The invention relates to the field of circuit control, in particular to an overcurrent protection circuit of a DC electronic contactor. Background technique [0002] DC power supplies are widely used in various fields of people's production and life, and common applications include electric vehicles, communications, energy, and computer room servers. In a DC power supply circuit composed of a DC power supply and a load, a mechanical contactor switch is usually used to control the on-off of the power supply circuit. However, mechanical contactors are expensive, and when used with high current, they are noisy and prone to arc damage, resulting in high cost of use. In addition, when mechanically switching, there will be pulse spike noise conduction into the surrounding power grid, polluting the grid environment. [0003] In order to solve the above problems, the patent number CN203071900U proposes an electronic contactor, but this patent does not mentio...

AI Technical Summary

Problems solved by technology

[0004] The invention provides an overcurrent protection circuit of a DC electronic contactor, aiming to solve the problem of overcurrent damage to the NMOS switch tube caused by the sudden change in load of the electronic contactor

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