Design of a green mode PWM control IC

To decrease the power consumption of a switching power supply, the most effective approach is to lower the switching frequency. Hence, the current mode pulse-width-modulation (PWM) controller used in a switching regulator must be capable of frequency modulation at light-load condition. The green mode circuit is designed in proposed current mode PWM control IC with the concept of off-time modulation. The switching frequency reduction and switch losses will be proportion to the load decrease at light-load condition. Also, the leading edge blanking (LEB), soft start, slope compensation, and over voltage protection (OVP) functions are integrated into the proposed chip.