A Reconfigurable SC DC–DC Regulator With Fixed On-Time Control for Transcutaneous Power Transmission

A reconfigurable switched-capacitor dc-dc regulator for transcutaneous power transmission is presented in this paper. An area-efficient power stage that can be configured to four different conversion ratios (2×/2.5×/3×/4×) under different input voltages, is proposed to maintain high power efficiencies and small output ripples of the regulator over a wide input voltage range caused by coupling variations. Instead of using a low-dropout regulator for post regulation, a fixed on-time regulation scheme is developed to provide output regulation and reduce the switching power loss under the light load condition. Implemented in a standard 0.35-μm n-well CMOS process, the proposed regulator delivers a maximum output current of 10 mA and achieves the peak power efficiency of 82%. When the input voltage varies by 1.6 V, the power efficiency of the proposed regulator can be improved by 40% compared with the regulator efficiency with a fixed-ratio 4× power stage. The output ripple reaches 24 mV that is 0.5% of the output regulated voltage.