Apparatus and method for standby power reduction of a flyback power converter

摘要

An apparatus and method for a flyback power converter reduce the standby output voltage of the flyback power converter by switching the reference voltage provided by a shunt regulator of the flyback power converter or the ratio of voltage divider resistors of the shunt regulator, to reduce the standby power consumption by an output feedback circuit of the flyback power converter, the shunt regulator, and the voltage divider resistors, and thereby improve the power loss of the flyback power converter in standby mode.

主权项

1. An apparatus for standby power reduction of a flyback power converter including a capacitor connected between an output and a ground for supplying a load current and an output feedback circuit for output feedback, the apparatus comprising:
a shunt regulator connected to the output feedback circuit, operative to provide a reference voltage; a voltage divider connected to the output and the shunt regulator, for determining an output voltage at the output of the flyback power converter according to a voltage dividing ratio of the voltage divider; a switch-resistor network connected in parallel to a resistor in the voltage divider, including a switch controlled by a sleep mode signal to switch the voltage dividing ratio; a current sense resistor in a current path of the load current to generate a current sense voltage; and a comparator connected to the current sense resistor, comparing the current sense voltage with a threshold value to assert the sleep mode signal.