A low-cost photovoltaic energy harvesting circuit for portable devices

This paper presents an efficient solar energy harvesting circuit for mobile phone battery chargers which can also be easily adapted for other mobile devices. The energy harvesting circuit is capable of making Maximum Power Point Tracking (MPPT) and also has a built-in battery protection function. A polycrystalline solar panel which supplies an average of 400mW (under 1 sun solar insolation) of power was selected for use in the proposed circuit. MPPT in the circuit is achieved by using the constant voltage tracking principle which is a non-complex yet highly efficient MPPT control method. It is implemented with purely discrete analog components with ultra-low power consumption. The proposed design is extremely compact and is feasible for commercial applications. The solar energy harvesting circuit consumes less than 330μW of power and achieves an overall efficiency of approximately 80-90%.