Input overvoltage protection circuit with powered inrush current restraining function

Abstract

The invention discloses an input overvoltage protection circuit with a powered inrush current restraining function. The input overvoltage protection circuit comprises a power supply circuit, a peak detection circuit, a peak voltage sampling comparison circuit, a powered moment switching tube current sampling comparison circuit, a bleeder resistor, a low on-resistance switching tube and a referencevoltage source; the power supply circuit comprises a first diode, a first capacitor and a voltage limiting biasing circuit; the peak detection circuit comprises a second diode and a second capacitor;the peak voltage sampling comparison circuit comprises a first comparator, a first resistor and a second resistor; and the powered moment switching pipe current sampling comparison circuit comprisesa second comparator, a third resistor and a fourth resistor. Therefore, the input overvoltage protection circuit is rapid in overvoltage protection action, and can restrain powered inrush current; theovervoltage protection circuit and the powered inrush current restraining circuit are organically combined to share a power switching tube and the power supply circuit, and thus the number of elements is small and the cost is low. The input overvoltage protection circuit not only solves the problem of input overvoltage protection difficulty, but also restrains the powered inrush current.

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to an input overvoltage protection circuit with a power-on surge current suppression function. Background technique [0002] At present, most DC-DC converter control chips provide overvoltage protection function. This function can force the converter to stop working when abnormal high voltage occurs in the power grid, but it cannot solve the problem of overvoltage of the input filter capacitor, nor can it solve the problem of the output of the APFC circuit. Filter capacitor overvoltage problem. For this reason, some converters add a mains detection circuit to trigger the relay action when the mains is abnormal, and disconnect the input circuit of the converter. However, the reliability of the electromagnetic relay is poor and the action is slow. The input filter capacitor still bears the instantaneous high voltage, which has not been completely solved. security ris...

AI Technical Summary

Problems solved by technology

However, although the above measures can control the power-on surge current within a certain range, they all have certain defects.

For example, the cost of connecting NTC thermistors in series is the lowest, but the AC input current always flows through the thermistors during normal operation, resulting in high power consumption of NTC resistors, high temperature and high current for a long time, and more seriously, power failure Finally, you must wait for the NTC resistor to cool down to normal temperature before powering on, otherwise the thermistor will lose its power-on surge current suppression function, reducing the reliability of the AC-DC converter; the AC zero-crossing trigger method requires a thyristor Rectifier, and additional auxiliary power supply, AC zero-crossing detection circuit, high cost, complicated circuit; although the parallel connection of power resistor and electromagnetic relay can better solve the power-on surge current and the current limit during the normal operation of the converter. The contradiction of resistance power consumption, but the relay pulls in a large current, the reliability of the mechanical contact is poor, and the volume is large

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