A DC power input anti-backfeed circuit and method

Abstract

The invention discloses a direct current power supply input reverse irrigation prevention circuit and method. The circuit comprises a reverse connection prevention circuit, a soft start circuit and a sampling control circuit. The reverse connection prevention circuit comprises a reverse connection prevention metal oxide semiconductor field effect transistor MOSFET. The slow start circuit comprises a slow start MOSFET. The sampling control circuit samples voltage between the drain and the source of the slow start MOSFET. When the voltage between the drain and the source of the slow start MOSFET is less than the reference voltage, the reverse connection prevention MOSFET is controlled to switch off. According to the invention, current reverse irrigation is avoided when input short circuit occurs or input voltage rapidly drops; when a DC / DC converter uses a full bridge circuit, the increasing of the voltage stress of the secondary synchronous rectifier MOSFET drain and source of the converter and the damage of the MOSFET are avoided; when reverse lightning surge occurs in an input port, current reverse irrigation is avoided; and power supply output power-off caused by module input capacitor power-off is avoided.

Description

technical field [0001] The invention relates to the technical field of power supplies, in particular to a DC power supply input anti-backfeed circuit and method. Background technique [0002] At present, high-power DC switching power supplies basically use metal-oxide-semiconductor field-effect transistors (MOSFETs) to realize the anti-reverse polarity function. Such as figure 1 It is an anti-reverse connection circuit for the currently commonly used MOSFET. When the input is normal, the MOSFET is turned on, and the conduction resistance of the MOSFET is small, the loss is small, and the circuit can work normally; when the input is reversed, the MOSFET cannot conduct It can effectively prevent the reverse connection of the circuit. [0003] However, when this kind of circuit is working normally, if there is a sudden input short-circuit fault, the input capacitor will discharge rapidly through the input terminal, causing current backfeeding. In this case, if the DC / DC (dir...

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Problems solved by technology

[0003] However, when this kind of circuit is working normally, if there is a sudden input short-circuit fault, the input capacitor will be quickly discharged through the input terminal, causing current backflow

In this case, if the DC / DC (direct current to direct current) converter adopts a full bridge circuit, it may cause the drain-source voltage stress of the synchronous rectification MOSFET on the secondary side of the converter to increase and damage the MOSFET; the large current generated by the rapid discharge of the input side Shock can also damage the DC power supply

[0004] If a diode is used instead of a MOSFET as an anti-reverse connection circuit, it can prevent current backflow when an input short-circuit fault occurs, but the diode loses too much when the high-power power supply is working normally, which will seriously affect the efficiency of the high-power power supply

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