簡易MPPT機能を有する熱発電腕時計用可変段数型スイッチトキャパシタ昇圧回路

抄録

A DC-DC converter scheme for thermoelectrically powered wristwatch is described. The converter consists of a variable-stage switched-capacitor (SC) circuit, a clock circuit, and a control circuit. The converter boosts the output voltage of thermoelectric (TE) generator that outputs a voltage of over 0.25V and supplies the generating power to a rechargeable battery with a voltage of 1.3V. A simple maximum-power-point-tracking technique makes it possible to extract power, which is close to maximum power, from the TE generator with a large internal resistance of 1.2kΩ. The maximum power point was automatically obtained by detecting the output open voltage of the variable-stage SC circuit and also by selecting the stage of multi-stage SC circuits. To verify the effectiveness of our converter, we fabricated a prototype with a 0.6μm CMOS process and measured the power extracted from a TE generator. The power extraction efficiency to the converter is 89% and the total conversion efficiency of the power supply module is 29%.