POWER SUPPLY CONTROLLER AND METHOD THEREFOR

A power supply controller and a method thereof are provided to improve operation efficiency of a power supply at soft load conditions by reducing an EMI(Electromagnetic Interference) between inner components. A power supply controller includes a PWM(Pulse Width Modulation) control block and a first circuit. The PWM control block is arranged to form a PWM driving signal for adjusting an output voltage within a desired voltage range. The first circuit is arranged to select a first clock with a first frequency, such that a first PWM driving signal is activated during a normal operation mode of a power supply. The first circuit is arranged to select a second clock with a second frequency, such that a second PWM driving signal is activated during a second operation mode of the power supply. The PWM control block includes a PWM latch(47), a PWM comparator(46), and a ramp generator(44). The second clock sets the PWM latch and activates the ramp signal, such that the second PWM driving signal is activated.