High efficiency DCM buck converter with dynamic logic based adaptive switch-time control

Abstract

This paper presents a dynamic logic based adaptive switch-time control circuit (DASTC) for fast control to minimize body diode conduction losses and dead-time of a buck regulator operating in discontinuous conduction mode. Dead-time is an important metric for improving efficiency of low voltage converters. DASTC provides instant sensing and feedback based on the load to minimize dead-time significantly compared to prior-art and scales low side power switch pulse width adaptively across load currents, just enough to discharge the stored inductor energy fully. Furthermore, the converter has inherent pulse skipping mode to lower the switching frequency at light loads to enhance light load efficiency. The proposed 1.5 V buck regulator was fabricated in 0.35 $$\upmu$$μm CMOS process with an input voltage range of 1.8---3 V and load current range of 1---200 mA. Measurement results demonstrate a peak power efficiency of 94.6 % and a high overall power efficiency ( >~89 %) for load currents greater than 5 mA for $${V_{IN}}$$VIN = 1.8 V. The proposed scheme achieves 4× (~5 ns) better dead-time and 4---5.5 % better power efficiency compared to prior-art over the load current range.