A PWM/PFM switch technique of dual-mode buck converter

In this paper, a new model of dual-mode DC/DC buck converter for portable applications was proposed. The converter combines pulse width modulation (PWM) and pulse frequency modulation (PFM) to keep high efficiency of overall load range. The switch between PWM and PFM mode is based on the judgment of Zero-Current detector and PWM/PFM detector. The converter can operate at 600kHz with supply voltage 2.4V to 4.5V, which is suitable for single-cell lithium-ion battery supply applications^[1]. The converter is modeled and simulated by Simulink. Experimental results show the maximum conversion efficiency is 93% at 140mA load current. Within all load current range from 10mA to 500mA, the converter efficiency is over 85%.