A regulated charge pump with low-power integrated optimum power point tracking algorithm for indoor solar energy harvesting

This paper 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 450nW, so the proposed technique is appropriate for indoor solar energy harvesting applications under dim lighting conditions.