Apparatus for controlling power

The purpose of the present purpose is to provide a power source control apparatus which detects a primary power voltage and regulates the power voltage outputted therefrom. The present invention comprises: a direct current power source supply part for converting a commercial power source into a direct current power source; a transformer for receiving the direct current power source and generating an induced electromotive force; a voltage controller connected to a primary winding of the transformer for detecting an input voltage (Vin) supplied to a PWM controller and outputting an operation control signal to the PWM controller according to a voltage variation of the detected input voltage (Vin); and the PWM controller for outputting a PWM control signal to generate the electromotive force induced from the primary winding to a secondary winding of the transformer according to the operation control signal of the voltage controller. The present invention can simplify the implementation of a circuit by detecting the voltage of a primary power source and regulating the voltage of the power source outputted therefrom, and can reduce the size of the circuit by eliminating a photo-coupler.