Power supply short circuit protection circuit

Abstract

The invention provides a power supply short circuit protection circuit comprising a voltage detection module, a switching control module, and a time-delay holding module. The voltage detection module is used for detecting a voltage related to the short circuit of an output terminal of a power supply. Whether the output terminal of the power supply is short-circuited is judged based on the detected voltage. When that the output terminal of the power supply is short-circuited is judged, a control signal is output to a terminal which controls a control IC to output or stop outputting a PWM signal. According to the power supply short circuit protection circuit, no matter if the control IC of a power circuit has a short circuit protection function, the control IC can be reliably enabled to stop outputting the PWM signal to achieve the purpose of short circuit protection, and the effective value of an output current when the output of a power supply is short-circuited can be reduced.

Description

technical field [0001] The invention relates to an output short-circuit protection circuit of a power supply. Background technique [0002] As an indispensable part of electrical appliances, power supply has always been one of the important guarantees for the normal operation of electrical appliances. In particular, switching power supplies have the characteristics of small size, light weight, and high conversion efficiency, and are widely used in various electronic devices in the fields of industrial control, communication office, and home consumption. A power supply generally consists of a control integrated circuit (hereinafter referred to as a control IC) for pulse width modulation (Pulse Width Modulation: PWM), switching elements such as power field effect transistors or triodes, and components such as transformers. [0003] Depending on the electronic equipment, the power supply used by the electronic equipment also adopts different technical specifications and indica...

AI Technical Summary

Problems solved by technology

[0005] However, when the output of the power supply is low voltage and high current, for example, when the output voltage is below 5V and the output current is above 10A, when a short circuit occurs at the output end of the power supply circuit, due to the large leakage inductance of the transformer , or the output impedance of the secondary short circuit is too large, etc., although the change of the output power in the short circuit has reached the threshold of the overpower on the primary side, however, figure 1 The voltage across the primary coil T1 of the transformer in the transformer cannot drop below the specified threshold for the control IC to stop outputting PWM signals, and even the control IC with the short-circuit protection function of primary side overpower cannot achieve short-circuit protection

[0006] For another example, when the power supply has multiple outputs, if one of the outputs is short-circuited and the other outputs are unloaded, the short-circuit output power can make the primary side of the power supply reach the overpower threshold, but the control IC on the primary side The voltage of the power supply terminal VCC cannot drop below the specified threshold to make the control IC stop outputting the PWM signal

Even a control IC with a short-circuit protection function for primary side overpower cannot achieve short-circuit protection

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