Digital controlled power supply

In a digital controlled power supply including a digital controller for generating a PWM signal which is used to turn on and off a switching element to obtain an output voltage for a load based on an input voltage, the digital controller includes an AD converter for receiving an analog output current from the power supply and converting the current into a digital value to produce a digital output current value, an arithmetic processing unit for conducting an arithmetic operation of a pulse width for each period of a sampling frequency of the AD converter or a frequency of carrier wave as a criterion to obtain the PWM signal, and a frequency controller for variably controlling the frequency of carrier wave and the sampling frequency on the basis of the digital output current value from the AD converter.