Research On Photovoltaic Charge Technology For Portable Devices

This paper focuses on solar charger for portable digital devices, in order to choice the system scheme mainly considers MPPT, topology structure of DC-DC converter, control strategy, maintenance of battery, and so on.Firstly, this paper analysis the current state of the application of photovoltaic system, explain the work principle of solar batteries, then give the equivalent circuit of solar batteries. Some MPPT algorithms have been introduced, then choose the proper method to achieve the system’s requirements.Secondly, introduce the storage batteries’kinds, work principles, charging methods and the mainly factors which influence its life for portable devices and combine with the output characteristic of solar batteries, design a charging method which has three steps: limited-current charge, quick charge carried out by MPPT,constant voltage charge.According to the above, adopting Boost circuit based on PWM technology as its main charging circuit. This system uses atmega48as its key controller, the voltage of solar and storage batteries are constantly detected, the charge current is detected too, the duty cycle of switch is adjusted by the detected data to make sure charge method can be achieved.Experimental results indicate that this system can choose proper charge method according to the states of solar and storage batteries intelligently, prolong the storage battery’s life. This system based on Boost topology structure can charge the storage battery when the solar battery’s output less than storage battery’s output, so improve the utilization of solar energy.