An Efficient Switched Capacitor DC-DC Converter for Body Heat Energy Harvesting

This paper presents an efficient switched capacitor DC-DC converter with a control loop for optimal efficiency tracking and voltage regulation. The proposed DC-DC converter interfaces with thermoelectric generators (TEG) to provide load with harvested power from body heat. This is a key step towards developing self-powered wearable devices. The proposed DC-DC converter employs a switched capacitor boosting scheme. The control loop adjusts the voltage conversion ratio (VCR) of the converter within - x9 and the switching frequency within 0.5 - 15 MHz. A cold start charge pump triggers the DC-DC converter to start up from low input voltages. The proposed DC-DC converter was fabricated in 180 nm standard CMOS process. The circuit specifications and functions have been verified through post-layout simulation. The cold start charge pump starts operation at the minimum input voltage of 310 mV. The control loop can find the optimal VCR and switching frequency to maximize the input power of the DC-DC converter and regulate the output voltage to a target voltage of 2 V. Besides, the DC-DC converter achieves power conversion efficiency (PCE) of 74% and output power of 0.8 mW.