To provide a pulse width modulation(PWM) power supply control system having smooth control characteristics over the entire duty ratio range.

The pulse width modulation(PWM) power supply control system employs a peak current program mode(CPM) control, which can make a smooth transition to a voltage mode control at a low duty ratio close to zero, at a high duty ratio. The PWM control system realizes a latch function not through a digital manner being employed generally but through an analog circuit. It can also realize a small delay time because it has no logic circuit inherent to latching nor a delay due to set up.