A power supply device and a single photo-coupler control circuit thereof
are provided. The power supply device includes a single photo-coupler
control circuit, a main converter and an auxiliary converter. The main
converter connects to an output load. The auxiliary converter connects in
parallel with the main converter. The single photo-coupler control
circuit, also connected to the output load, monitors the status of the
power supply device and controls the main converter and the auxiliary
converter accordingly. The single photo-coupler control circuit only has
one photo-coupler. The main converter and the auxiliary converter
together provide a first output to the output load when the power supply
device works in a normal mode. The main converter is turned off so that
only the auxiliary converter provides a second output to the output load
when the power supply device works in a standby mode.