A High-Efficiency Current-Mode Buck Converter With a Power-Loss-Aware Switch-On-Demand Modulation Technique for Multifunction SoCs

Modern multifunction systems on chip often require a high-efficiency buck converter over a wide load current range as the main power source, for which complex multimode operation with mode detection/change is a frequent compromise between efficiency and transient response. This paper proposes a novel power-loss-aware switch-on-demand modulation (PLASOM) technique based on accurate power loss modeling to switch critical components/parameters of power loss on demand: the ON/OFF status and the size of the power transistor, the dead time, and the ON/OFF status of power-hungry subcircuits. The proposed PLASOM-based converter can work as either an adaptive on-time mechanism with constant frequency or a cycle-extended adaptive ON/OFF-time mechanism with variable frequency without mode detection/change, so that the conversion efficiency and transient response can be improved. A proposed buck converter with the PLASOM technique was implemented using the TSMC 90-nm 1/3.3-V CMOS process. Experimental results show that a conversion efficiency higher than 90% was achieved over the 1-500 mA load current range, whereas the voltage variation/recovery time during the 0.1-500 mA load transient were less than 50 mV/25 μs. Performance evaluations indicate that the proposed PLASOM technique is favorable for wide load current range buck converters in terms of conversion efficiency, transient response, and voltage ripples.