DC-DC converters with high efficiency over wide load ranges

Abstract

An integrated switching regulator is presented, including theory of operation, circuit design, and test results. This DC-DC converter introduces several novel circuits which enable more efficient operation at output powers from l00J.1W to lW. Efficiency above 80% is achieved from 500JlW to 500mW. Specifically, depending on the load current, the regulator automatically switches between Pulse Frequency Modulation (PPM) and Pulse Width Modulation (PWM), and also automatically selects the optimum switching MOSFET. The current sensing is done without an additional current sense resistor. PFM mode operation is synchronous to allow sampled data systems to avoid sampling on switching transitions. In all modes of operation, the regulator output voltage is digitally programmable. This enables variable voltage architectures, in which the power supply of a digital system is dynamically changed depending on the throughput requirements, resulting in significant power reductions.