A Buck DC-DC Achieving High Efficiency in an Ultra-wide-load Range from 0.001 to 2A

This paper presents a Buck DC-DC chip based on A-COT (adaptive constant-on-time), which achieves high efficiency within an ultra-wide load current range of 0.001-2A. For heavy load, the bootstrap circuit is employed with NMOS as the high-side (HS) switch to reduce conduction losses. As the load current decreases, the circuit seamlessly transits into discrete conduction mode (DCM) controlled by zero-crossing detection circuit (ZCD) to reduce switching frequency and switch losses. For ultra-light load, the circuit enters low power mode (LPM) to reduce the quiescent current of the control circuit and minimize static losses. To improve output voltage accuracy and circuit stability, a type-III compensator is implemented to enhance loop gain and phase margin. The proposed DC-DC converter achieves peak efficiency of 92.38%. For 1mA load condition, efficiency is up to 86.8%. Within the entire load range of 0.001-2A, the efficiency is all higher than 84.5%.