Comparison of light-load improvement techniques for low power buck converters

Abstract

Recently a great deal of work has been done to improve the efficiency of DC-DC converters at light-load. This has been driven by the desire to increase battery life in portable devices and to reduce standby power consumption in mains powered devices. In general, power supplies are moving towards higher switching frequencies to reduce passive component size, resulting in higher switching and gate drive power loss. Several methods to reduce power loss at light-load including Pulse Frequency Modulation and Diode Emulation are investigated in this paper. These methods however result in higher inductor current ripple as the inductor is designed for operation when output current is at its maximum. Distributing inductors in parallel is shown to provide a means for increasing the effective inductance at light-load through reducing current ripple.