PWM/PSM Dual-Mode Controller for High Efficiency DC-DC Buck Converter

This paper introduces a novel method of realizing PWM/PSM dual-mode controller for high efficiency DC-DC buck converters. A minimum duty cycle control module is added to the PWM control loop, and with a simple logic control, the system can work in PSM mode when the load is light to improve the efficiency of the system over wide load range. A testing chip of the dual-mode DC-DC buck converter is implemented by CSMC's 0.5 ¿m 40 V BCD process. The testing results proved the system functioned well in both PWM mode and PSM mode, and switched smoothly between the two modes. The efficiency is greatly improved when the load is light. It is no less than 75% over the whole load range and can reach 91% with heavy load.