Switching mode power supply

PURPOSE: A switching mode power supply is provided to reduce power consumption by stopping a PWM IC in the no-load mode. CONSTITUTION: A DC to DC converter(100) converts the level of DC power. A PWM IC(200) converts the level of the DC power by controlling a switching duty of the DC to DC converter. A control unit(1000) includes a no-load determining unit(300), a no-load control unit(400), a timing signal generating unit(500), and a PWM IC control unit(600). The PWM IC control unit controls the on and off of the PWM IC according to a timing signal. A sub power source(700) supplies power to the no-load control unit and the no-load determining unit in a no-load mode. [Reference numerals] (100) DC/DC converter; (300) No-load determining unit; (400) No-load control unit; (500) Timing signal generating unit; (600) PWM IC control unit; (700) Sub power source; (AA) Rectifier