A Regulated Charge Pump With a Low-Power Integrated Optimum Power Point Tracking Algorithm for Indoor Solar Energy Harvesting

This brief presents a regulated charge pump (CP) with an integrated optimum power point tracking (OPPT) algorithm designed for indoor solar energy harvesting. The proposed OPPT circuit does not require a current sensor that consumes power proportionally to the load. The solar cell voltage is regulated at the optimum power point; the CP output is regulated according to the target voltage. The controller of the OPPT circuit and CP dissipates only 450 nW; thus, the proposed technique is appropriate for indoor solar energy harvesting applications under dim lighting conditions.