The block diagram of the MPPT control is shown in Fig. 5 The proposed control consists of two loops, the maximum power point tracking loop is used to set a corresponding yef to the charger input, the voltage regulating loop is used to regulate the solar array output voltage according to ye,, which is set in the MPPT loop. The functions of the two loops are performed by a DSP-based controller. The controller senses the solar array current and voltage to calculate the solar array output power, power slope and v for maximum power control.