A New Control Method for Switched Buck-Boost DC-DC Converters with Delta-Sigma Modulation for Mobile Equipment

This paper presents a new approach to creating high-performance DC-DC converter systems for mobile-phone applications. The required supply voltage is 2.5 V, and the output voltage of recent lithium-ion secondary-batteries ranges from 4.2 V to about 2 V as they discharge. We have developed a bridge-configuration switching regulator that toggles between voltage-buck and voltage-boost modes, and maintains output voltage regulation even with a small input-output voltage differential. It uses delta-sigma modulation, switches smoothly between voltage-buck and voltage-boost modes with plusmn6 mV ripple (at constant load), and load regulation is within plusmn20 mV for a load current step of 0.5 A