A ripple-based adaptive on-time controlled buck converter with slope balance technique

Abstract

A ripple-based adaptive on-time controlled buck converter with slope balance technique is presented in this paper. The slope balance technique provides a fixed switching frequency. A 4-bit single-slope analog-to-digital converter (ADC) was used to fix switching frequency when power supply was from 3.3 to 4.5 V. The slope balance technique is proposed to achieve an adaptive on-time control and without extra clock-controlled circuits and current sensing circuits. The input voltage can be predicted from the adaptive on-time by using 4-bit single-slope ADC control. Measurement results show that switching frequency is 1.448 and 1.438 MHz when load current is 200 and 1000 mA, respectively. The proposed buck converter was fabricated in 0.35 mu m CMOS technology with a supply voltage of 4.5 V. The output voltage was measured to be 1.2 V and the load current range was determined to range 200-1000 mA.