High efficiency boost converter with variable output voltage using a self-reference comparator

This paper presents a boost converter with variable output voltage and a new maximum power point tracking (MPPT) scheme for biomedical applications. The variable output voltage feature facilitates its usage in a wide range of applications. This is achieved by means of a new low-power self-reference comparator. A new modified MPPT scheme is proposed which improves the efficiency by 10%. Also, to further increase the efficiency, a level converter circuit is used to lower the Vdd of the digital section. The low input voltage requirements allow operation from a thermoelectric generator powered by body heat. Using this approach, a thermoelectric energy harvesting circuit has been designed in a 180 nm CMOS technology. According to HSPICE Simulation results, the circuit operates from input voltages as low as 40 mV and generates output voltages ranging from 1 to 3 V. A maximum power of 138 μW can be obtained from the output of the boost converter which means that the maximum end-to-end efficiency is 52%.