Patent ID: 8368249

Claim:
A power supply unit provided with AC/DC voltage detection, comprising: a first stage power circuit connected to a voltage bus for receiving a first voltage and generating a bus voltage accordingly; a second stage power circuit connected to the voltage bus for receiving the bus voltage and generating an output voltage accordingly; a bypass switch connected between an input terminal and an output terminal of the first stage power circuit; and a power control unit connected to the first stage power circuit, the second stage power circuit and the bypass switch for detecting whether the first voltage is a DC voltage or an AC voltage, and manipulating the first stage power circuit and the bypass switch accordingly; wherein the power control unit manipulate the first stage power circuit and the bypass switch to turn on and off according to the form and magnitude of the first voltage; wherein the power control unit comprises an AC/DC voltage detection circuit for detecting the form and magnitude of the first voltage, and the power control unit detects the form of the first voltage by determining whether a differential value between a maximum sampled value and a minimum sampled value produced by the AC/DC voltage detection circuit is greater than a predetermined differential value.