Timer based anti-surge current circuit

Abstract

The invention relates to a timer based anti-surge current circuit, which mainly solves the problem of surge current at a moment of power-on in a conventional bridge type rectifier and filter circuit.The anti-surge current circuit includes a current limiting circuit and a 555 timer driving circuit. A capacitance rectifier and filter circuit converts alternating current power into direct current power and supplies the direct current power to the current limiting circuit and the 555 timer driving circuit. The current limiting circuit clamps charging current of a rectifier and filter circuit capacitor. When the voltage of the rectifier and filter circuit capacitor rises to make a 555 timer normally work through a voltage dividing resistor, a delay capacitor is charged to a threshold so as tomake the driving circuit based on the 555 timer to trigger the current limiting circuit to be closed. Suppression time of the anti-surge current circuit of the invention is adjustable, surge current does not change with temperature, and the circuit is reliable and can be applied in high-power switching power supplies.

Description

technical field [0001] The invention belongs to the technical field of power supplies, and in particular relates to a surge current suppression circuit in a bridge rectifier filter circuit. Background technique [0002] With the development of electronic technology, the output power of the power supply is getting bigger and bigger. The filter capacitor at the back end of the rectifier bridge of the AC-to-DC power supply is also becoming larger and larger. Most switching power supplies usually use thermistors or common-mode inductors to reduce the high inrush current generated when the switching power supply is powered on. The inrush current is mainly generated by the charging of the filter capacitor. At the moment of electrical conduction on the rectifier bridge of the switching power supply, the capacitor presents low impedance characteristics to the DC power at the rear end of the rectifier bridge. If no protective measures are taken, the peak current of the input surge c...

AI Technical Summary

Problems solved by technology

[0003] The existing method of series-connecting thermistors (NTC) uses the resistance of the thermistor at the moment of power-on to limit the inrush current, and the resistance of the thermistor decreases after steady state to reduce the loss of the thermistor. This method is relatively simple , but limited by its own loss and poor high-temperature start-up performance, it is generally only suitable for occasions below 500W and low requirements for power supply

However, the method of connecting a common-mode inductor in front of the filter capacitor to suppress the inrush current is too bulky, and the practicability is particularly poor.

Images