Adaptive-on-time control technique for output ripple reduction and light-load efficiency enhancement in low-power switched-capacitor DC-DC regulators

This paper presents an adaptive-on-time control (AOTC) technique for low-power switched-capacitor (SC) DC-DC regulators in energy-harvesting applications. When the input voltage varies, the proposed AOTC scheme can automatically adjust the duration of charge transfer between input and output of the converter to control the output ripple voltage. The switching frequency can also be decreased with the load current for reducing the converter switching power loss. An AOTC-based dual-output SC DC-DC regulator was implemented in a standard 0.35-μm CMOS process. Experimental results show that the converter can provide two regulated outputs of 2V and 3V, deliver up to 12mA at each output, and achieve a maximum power efficiency of 89.5%. With the AOTC, the converter output ripple is reduced by as much as 3.8 times over a wide input range from 1.1V to 1.6V.