An overcurrent protection circuit for a three-way output dc/dc converter

Abstract

The invention provides an over-current protection circuit of a three-way output DC / DC converter. Against the defects of existing over-current protection modes, a mode of directly detecting output load currents is adopted, the problem of drifting of over-current protection points is solved, detected output current signals are collected through a high-precision sampling resistor and then have access to an operational amplifier, over-current error signals are amplified and integrated through the operational amplifier, then control signals are output, and current-limiting protection of the circuit is achieved. Therefore, the control signals are produced after the operational amplifier regulates the over-current error signals, and the purposes of accurate current limit and stable control are achieved. The problem that a power switch tube is switched on and off frequently when a comparer is used is solved, the problem of the drifting of protection currents of a high end and a low end which are used for defecting an input switch current is solved, and the problem that the power switch tube which detects output currents through the resistor is switched on and off frequently and then is burnt up easily is also solved.

Description

Technical field [0001] The invention belongs to a semiconductor integrated circuit and relates to an overcurrent protection circuit of a three-output DC / DC converter. Background technique [0002] The DC / DC converter circuit is an electronic device that has been widely used. In order to improve the reliability of its power supply, a reasonable protection circuit must be designed. Overcurrent protection is one of the protection circuits. It protects the power supply and power switching devices when the output is overloaded or short-circuited. According to the current sampling method, it can be divided into two types: (1) Input switch current detection; (2) Output current detection. The principle of over-current protection is to detect the input switch current or the output current of the power supply through the current detection circuit, compare with the set threshold, and control the PWM signal on and off. When the output of the DC / DC converter is overloaded or short-circuited...

AI Technical Summary

Problems solved by technology

[0005] The technical problem solved by the present invention is to provide an overcurrent protection circuit for a three-way output DC / DC converter, which can achieve the purpose of precise current limiting and stable control, and solves the problem of high and low protection current drift of the input switching current , It also solves the problem that the power switch tube that uses the resistance to detect the output current is frequently turned on and off so that it is easy to burn out

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