Pseudo AC Current Synthesizer and DC Offset-Corrected Technique in Constant-on-time Control Buck Converter for Werable Electronics

Abstract

Constant-on-time (COT) control with an additional current feedback in conventional buck converter has the advantage of using low equivalent series resistance (ESR) output capacitor. Unfortunately, the disadvantage is output voltage regulation accuracy is greatly deteriorated by its DC offset voltage from the current feedback. More seriously, opposite reaction between output voltage and the additional current feedback signal deteriorates transient response. In this paper, pseudo AC current synthesizer and DC voltage offset correction technique are proposed to reduce load-dependent DC offset voltage for improving load regulation. Furthermore, the transient enhancement technique instantly extends on-time and the off-time periods in load change. Test chip fabricated in UMC 28nm CMOS process demonstrated that offset voltage is improved from 65mV to 4mV. Besides, the transient response can be improved to 4 mu s and 5 mu s when load changes from 0.3 to 1.7A and vice versa, respectively. The advantages of compact size, low cost, and high performance power management can maintain wearable electronics small volume, light, and sustainable.