ABSTRACT:

A dual-mode DC/DC buck converter is presented in this paper. The converter operation includes the soft start, sawtooth oscillator, zero-current detector and PWM/PFM detector. According to the judgment of zero-current detector and PWM/PFM detector, the converter can switch automatically between pulse width modulation (PWM) mode and pulse frequency modulation (PFM) mode. Because of this, the proposed converter model has the ability to adapt to various loading conditions and therefore achieve high efficiency over a wide load-current range which is critical for extended battery life. The converter is modeled and simulated by Simulink. Experimental results show the maximum conversion efficiency is 93% at 140 mA load current. Within all load current range from 10 mA to 500 mA, the converter efficiency is over 85%.