SOFT-OFF CONTROL CIRCUIT, POWER CONVERTER AND ASSOCIATED CONTROL METHOD

摘要

A power converter having a soft-off control circuit and a variable reference signal generation module and associated method for controlling the power converter. The variable reference signal generation module is configured to provide a variable reference signal to the power converter. The soft-off control circuit is configured to determine whether an input voltage of the power converter exceeds an over-voltage threshold, and to control the variable reference signal to increase once the input voltage reaches the over-voltage threshold and to decrease when the input voltage is lower than the over-voltage threshold. The power converter can regulate an output voltage to increase with the increase of the variable reference signal and to decrease with the decrease of the variable reference signal so that during a soft-off procedure the input voltage may not exceed the over-voltage threshold, enabling the power converter to be safely shut off.

主权项

1. A soft-off control circuit for controlling a soft-off procedure of a power converter, wherein the power converter comprises a main switch and is configured to receive an input voltage and to provide an output voltage based on driving the main switch to switch on and off, and wherein the power converter further comprises a soft-start/soft-off pin configured to provide a variable reference signal; the soft-off control circuit comprising:
a first input terminal configured to receive the input voltage of the power converter; a second input terminal configured to receive an enable signal, wherein the enable signal has a first enable state for controlling the power converter to shut off and start the soft-off procedure and a second enable state for controlling the power converter to power on; a third input terminal configured to receive an over-voltage threshold, wherein the over-voltage threshold is designed to indicate an over-voltage of the input voltage during the soft-off procedure; and an output terminal configured to provide a soft-off control signal; wherein the soft-off control circuit is configured to generate the soft-off control signal at least based on the enable signal, the input voltage and the over-voltage threshold, and wherein when the enable signal is at the first enable state, the soft-off control signal is configured to control the variable reference signal to increase when the input voltage is higher than the over-voltage threshold, and to control the variable reference signal to decrease when the input voltage is lower than the over-voltage threshold.