Patent ID: 8390260

Claim:
A power supply for a negative voltage load comprising: a switch-mode power unit having a rectifying circuit connected to an AC power source and converting AC power to DC sine wave power; a power factor correction circuit having input terminals connected to the rectifying circuit, receiving the DC sine wave power from the rectifying circuit, adjusting current and voltage of the DC sine wave power to be in phase with each other and having output terminals; and a DC to DC power circuit having input terminals connected to the output terminals of the power factor correction circuit, having output terminals connected to power terminals of the negative voltage load, reducing and stabilizing the adjusted DC power from the power factor correction circuit and outputting at least one low-voltage DC power to the negative voltage load; a monitoring unit coupled to the switch-mode power unit to detect operation status of the switch-mode power unit and having power terminals, an input terminal and an output terminal; a first auxiliary power unit having input terminals connected to the output terminals of the power factor correction circuit, having output terminals connected to the power terminals of the monitoring unit, converting the DC power from the power factor correction circuit to a first DC power and outputting the first DC power to the power terminals of the monitoring unit; and a second auxiliary power unit having input terminals connected to the output terminals of the DC to DC power circuit and the input terminal of the monitoring unit, having output terminals connected to the power terminals of the monitoring unit, having an enable terminal connected to the output terminal of the monitoring unit, enabled by a control signal produced by the monitoring unit, converting negative voltage power of the negative voltage load to a second DC power and outputting the second DC power to the power terminals of the monitoring unit.