The Design of a Micro Power Management System for Applications Using Photovoltaic Cells With the Maximum Output Power Control

An inductor-less on-chip micro power management system for light energy harvesting applications is presented. We target at wide variety of applications that operate at different lighting environments ranging from strong sunlight to dim indoor lighting where the output voltage from the photovoltaic cells is low. A step-up charge pump is used to directly operate the circuit or to charge a rechargeable battery. The power management system operation is discussed and the control strategy for transferring the maximum output power from the power system is presented. Low power circuit design is proposed for the implementation of the system maximum output power control. The system was implemented using a 0.35-mum CMOS process. The chip was fabricated and measurements were conducted for different lighting conditions to demonstrate the system operation and verify the control strategy.