The solar controller is an important part of the solar PV system that automatically prevents the battery pack from overcharging and overturning and has a simple measurement function of the electronic device. As the battery pack is overcharged or over discharged will seriously affect its performance and life, charge and discharge controller in the photovoltaic system is generally essential. It largely determines the reliability of solar photovoltaic systems. The main task of the controller is to realize the solar energy to charge the battery and protect the battery in the PV system.

The switching device T1 in the charging circuit of the parallel type charging and discharging is connected in parallel to the output of the square of the solar cell. When the voltage of the battery is larger than the "full of the cut-off voltage", the switching device T1 is turned on and composed at the same time. A1 is the overvoltage detection controller circuit. The non-inverting input of A1 is supplied with the reference voltage of "over-voltage cut off" by W1, and the inverting input terminates the measured battery. When the battery voltage is greater than the "over-voltage cut-off voltage", A1 output G1 is low, turn off the switching device T1, cut off the charging circuit, play the role of over-voltage protection. When the overvoltage protection battery voltage drops to less than the "overvoltage recovery voltage", A1 inverting input potential is less than the non-inverting input potential, then the output G1 from low to high.

A2 is the under voltage detection control circuit, the reverse termination of the under voltage reference voltage provided by W2, the same phase termination battery voltage (and overvoltage detection controller circuit), when the battery voltage is less than the "under voltage threshold level" , The A2 output G2 is low, the switching device T2 off, cut off the controller output circuit, to achieve "under voltage protection", under voltage protection, with the battery voltage increases, when the voltage is higher than the " Under voltage recovery threshold ", the switching device T2 re-conduction, restore the load power supply. The "under voltage protection threshold" and "under voltage recovery threshold" are adjusted by W2 and R2.