Dithering Skip Modulator with a Novel Load Sensor for Ultra-wide-load High-Efficiency DC-DC Converters

Abstract

Dithering skip mode with a novel load sensor for DC-DC converters is proposed to maintain a high efficiency over a wide load range. Due to the efficiency drop of the transition from the pulse-width modulation (PWM) to pulse-frequency modulation (PFM), a novel dithering skip modulation (DSM) is introduced to smooth the efficiency curve. Importantly, DSM mode can dynamically skip the number of gate driving pulses, which is inverse proportional to load current. Besides, a novel proposed load sensor can automatically select the optimum modulation method from these three modulation methods without an external selection pin. Simulation results shows DSM can maintain the efficiency of converters as high as about 89% over a wide load current range from 3mA to 500mA