A dual-feedback short circuit protection device

Abstract

This invention puts forward a dual-feedback short-circuit protection device including a current test circuit, a second signal comparison circuit and a short-circuit operating circuit connected orderly characterizing in also including a compensated signal delay circuit, a first signal comparison circuit and the short-circuit operating circuit connectd orderly, in which, the compensated signal delay circuit delays the voltage compensation signal and outputs it to the first signal comparison circuit, which compares the input signal with a threshold value, if it is greater than that, it sends a short-circuit control signal to the operation circuit to control the switch entering into a short-circuit protection state, when the supply with a capacitance load operates normally, the delay circuit outputs a threshold value with the voltage smaller than the first signal comparison circuit, the short-circuit operation circuit does not operate, when the load is over a preset sphere, it outputs a threshold value with the voltage greater than the first one, the operation circuit controls the switch supply entering into a short-circuit protection state.

Description

technical field [0001] The invention relates to a short-circuit protection device for a switching power supply, in particular to the field of switching power supplies that require relatively high capacitive load capacity and reliability. Background technique [0002] Due to its high efficiency, switching power supplies have been widely used. In the protection function of the switching power supply, an output short-circuit protection circuit is generally required to prevent the switching power supply from damaging the power supply and the load due to excessive operating current when it is short-circuited. The performance of the short-circuit protection circuit directly affects the reliability of the entire power supply. At present, most of the short-circuit protection circuits in switching power supplies use the current detection terminal of the current-mode pulse width modulation chip to detect the working current of the primary side of the transformer, and limit its peak v...

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Problems solved by technology

[0004] Another method uses a delay circuit to delay the action of the short-circuit protection circuit to improve the ability of the switching power supply to carry a capacitive load when it is turned on, but this method will increase the circuit loss during short-circuit protection and reduce the reliability of the switching power supply.

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