Over-voltage protection circuit for boosting-type switching power supply

Abstract

The invention provides an over-voltage protection circuit applied to a boost switching power, which consists of a bleeder circuit and a voltage comparator. The voltage comparator compares an output voltage and a reference voltage of the bleeder circuit and then sends the voltages into a control logic circuit for obtaining a controlling signal. The over-voltage protection circuit further includes a sampling voltage reducing circuit. An input end of the sampling reducing circuit is connected with a drain electrode of switching power and an output end of the sampling reducing circuit is connected with an input end of the bleeder circuit. Therefore the drain electrode of the switching power is sampled and the voltage is reduced. The over-voltage protection circuit in the invention, compared with other over-voltage protection methods, adopts a reverse breakdown voltage of a diode as a condition for detecting whether over voltage occurs, thus realizing the simple structure with low cost. Through an SW pin, the output voltage is detected; therefore, the judgment of whether over voltage occurs by detecting a VOUT pin is avoided, thus reducing the exterior pins of a chip and saving the encapsulation cost.

Description

technical field [0001] The invention relates to an overvoltage protection circuit suitable for a step-up switching power supply. Background technique [0002] The function of the step-up switching power supply chip is to use a lower voltage as the power supply to obtain a higher output voltage, and adjust the output voltage by adjusting the voltage division coefficient of the voltage division network outside the chip. When the voltage division coefficient of the external application circuit of the step-up switching power supply chip is improperly set, or the pin setting of the chip is wrong, it may cause the feedback voltage of the chip to be set to other potentials by mistake, resulting in the output voltage exceeding the normal working range. The continuous progress of the existing process technology makes the size of the chip smaller and smaller, and the breakdown voltage of the chip is also smaller and smaller. When the output voltage is higher than the source-drain bre...

AI Technical Summary

Problems solved by technology

However, for high output voltage, if the resistance value of the resistor network 11 is too small, the power consumption of the chip will be too large, and if the resistance value of the resistor network 11 is made larger, it may consume a larger chip area and increase the cost of the chip.

Images