Importance

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Abstract

Disclosed is a short-circuit protection circuit for a voltage sampling resistor of a primary side converter, comprising a high voltage power transistor, a high voltage starting resistor, a first voltage dividing resistor of a port VDD, a second voltage dividing resistor of the port VDD, an NMOS transistor, a diode, a first comparator, a second comparator, a third comparator, a time delay circuit, a filter, a first logic circuit, a second logic circuit, a current supply, a first AND gate and a first inverter. The chip of the present disclosure is capable of correctly and effectively detecting whether the sampling resistor is shorted or not before the chip works normally, thereby avoiding the risk of damaging the chip by large current from the voltage feedback port FB due to turn-on of the switching transistor when the upper voltage sampling resistor is shorted, and greatly reducing the input power.

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First Claim