A High-Efficiency and Wide-Load Range Buck Converter with SAR-ADC-Assisted Width Switching Technique

This letter presents a successive-approximation-register (SAR) analog-to-digital converter (ADC) assisted width switching technique in buck converter, to achieve high efficiency over a wide load range. Besides, an isolation buffer is realized so that the sampling behavior in ADC does not affect the PWM main loop. An improved zero current detector (ZCD) circuit is also proposed to ensure discontinuous conduction mode (DCM) operation and improve the efficiency at light-load further. The design, simulated in a typical 0.35μm CMOS process and operated at 2 MHz switching frequency, achieves a peak efficiency of 95%. Moreover, the efficiency is higher than 85% over a wide load current range from 10mA to 4A.