Patent ID: 8441270

Claim:
An alternating current (AC) detection circuit for power supply, the AC detection circuit comprising: a rectifying part configured to rectify an AC voltage; a voltage division part configured to divide the rectified voltage according to a preset division ratio; a voltage stabilization circuit part configured to stabilize the divided voltage; a first square wave generating part connected to a first operation voltage terminal and configured to compare the stabilized voltage with an internal reference voltage, and generate a first square wave signal having a duty ratio based on a result of comparing the stabilized voltage and the internal reference voltage; and a second square wave generating part connected to a second operation voltage terminal and configured to be interlocked with the first square wave generating part, and generate a second square wave signal, wherein the second square wave generating part is configured as a photocoupler connected to each of the first and second operation voltage terminals and configured to generate the second square wave signal.