Patent ID: 8374013

Claim:
A power supply comprising: an AC-to-DC circuit ( 1 ); a DC-to-DC circuit ( 2 ); an interface ( 3 ) used by both of the AC-to-DC circuit ( 1 ) and the DC-to-DC circuit ( 2 ), wherein the interface ( 3 ) includes an ACL/DC+ input terminal ( 31 ), an ACN/DC− input terminal ( 32 ) and a ground ( 33 ); and a control circuit ( 4 ) for controlling the interface ( 3 ), wherein the control circuit ( 4 ) includes an AC/DC detecting circuit ( 41 ) for determining whether an input voltage is AC or DC, an AC/DC converting circuit ( 42 ) for selectively conducting AC or DC, and an AC/DC conversion controlling circuit ( 43 ) for controlling the direction of the input voltage based on the determination in the AC/DC detecting circuit ( 41 ); said AC/DC converting circuit ( 42 ) includes: a capacitor (C 1 ) formed with two terminals; a relay (K 1 ) formed with a positive input pin and two normally-on pins; and a resistor (R 1 ); wherein one of the terminals of the capacitor (C 1 ) is connected to the ACN/DC− input terminal ( 32 ) via an inductor; wherein the other terminal of the capacitor (C 1 ) is connected to the positive input pin of the relay (K 1 ); wherein one of the normally-on pins of the relay (K 1 ) is connected to the ACN/DC− input terminal ( 32 ) via the inductor; wherein the other normally-on pin of the relay (K 1 ) is connected to the DC-to-DC circuit ( 2 ); wherein the resistor (R 1 ) is connected in parallel to the capacitor (C 1 ).