Wide-operating-point DC-DC converter for sub-microwatt photovoltaic power conversion in biomedical implants

Abstract

This article presents a DC-DC converter designed for photovoltaic power conversion in biomedical implants. The design employs a differential topology for switching signal generation, enhancing signal robustness while reducing auxiliary circuit overhead. An input-supplied bootstrap circuit enables cold-start capability and prevents signal decay at low input voltage conditions. The circuit maintains optimal power conversion efficiency across a wide range of input conditions through oscillator tuning and charge pump reconfiguration. Implementation and simulation in 180 nm CMOS process demonstrate end-to-end power conversion efficiency of 50-86 % across an input power range of 1.6 nW-150 μW. The converter remains operational from 723 pW-500 μW with input voltages of 128-420 mV, while maintaining cold-start capability throughout this operating range.