A high-efficiency burst mode boost converter with a sharing main power NMOS for start-up

Abstract

This paper presents a high-efficiency boost converter with a wide input range and a start-up strategy of sharing main power NMOS which can start-up at an input voltage of 700 mV. A burst mode with boundary conduction mode (BMBCM) control is utilized in the proposed boost converter to achieve high efficiency across the wide input power range. A method is also suggested to determine the optimal peak inductor current for a given input range. Compared to other start-up strategies, the proposed start-up circuit reduces chip area by sharing the main power NMOS with the normal operation mode, eliminating the need for an additional start-up power transistor. A new ultra-low-power voltage detection circuit is used to control the start-up process. The proposed boost converter is designed and fabricated in a 180 nm BCD process with an active chip area of only 0.33 mm2. The circuit achieves a peak efficiency of 94.8% at an input voltage of 3 V and an output voltage of 3.6 V, while maintaining an efficiency of at least 65.9% across the input power range of 7 μW to 300 mW.