A Constant-on-Time Control DC-DC Buck Converter With the Pseudowave Tracking Technique for Regulation Accuracy and Load Transient Enhancement

Abstract

Constant-on-time (COT) control with an additional current feedback path in conventional buck converters can remove the need of large equivalent series resistance (ESR) at the output capacitor but it induces degraded output voltage regulation accuracy and slow transient response owing to opposite reaction between the output voltage and the additional current feedback information. Therefore, this paper proposes the pseudowave tracking (PWT) technique to reduce the load-dependent dc offset voltage of output load regulation while keeping the fast transient response similar to conventional COT buck converter with large ESR. The PWT technique further improves the transient response instantly by extending on-time and off-time periods during light-to-heavy and heavy-to-light load changes, respectively. The test chip fabricated in 28 nm CMOS process has demonstrated the improvement of offset voltage from 42 to 4 mV, while the transient response can be improved to 4 and 5 mu s with load changes from 0.3 to 1.7 A and vice versa, respectively.