Improvements in Light-Load Efficiency and Operation Frequency for Low-Voltage Current-Mode Integrated Boost Converters

This brief presents design techniques to improve both the power efficiency and the operation frequency of low-voltage current-mode boost converters for single-cell NiMH battery applications. For delivering a wide range of load currents, a cross-conduction-free width-switching (CCF-WS) technique is developed to eliminate the short-circuit power loss associated with switching different segments of on-chip power transistors, thereby improving the converter light-load power efficiency. A low-voltage current sensor is also proposed to increase the sensing speed. Hence, the converter operation frequency is improved and the required value of the inductor in the power stage is reduced. A boost converter was implemented in a standard 0.35-μm CMOS process. The converter can accept a minimum input voltage of 1.2 V, deliver a maximum output current of 200 mA, and properly operate at a switching frequency of 1 MHz with only a small inductor of 4.7 μH. The proposed boost converter increases the switching frequency by at least 3.3 times compared with the previously reported low-voltage designs. The converter also achieves a maximum power efficiency of 90% and provides up to 11.5% power efficiency improvement with the CCF-WS technique.