Maximum power point tracker for small number of solar cells connected in series

Maximum power point tracking (MPPT) techniques are widely applied in photovoltaic (PV) systems to fully utilize the PV array output power. Major challenges for MPPT are rapidly changing irradiance conditions and partial shading of the PV cells. These issues become even more severe for mobile applications, such as solar cells on the roof of electric vehicles. This paper deals with the implementation of a fast, fully integrated MPPT for a small number of solar cells connected in series with respect to mobile applications. For this special requirements, different open and closed loop MPPTs have been compared and evaluated. The optimal MPPT has hence been implemented. Furthermore, a bypass concept based on MOSFETs instead of bypass diodes is applied to utilize the maximum available power of the solar cells. The MPPT has been built in VHDL and realized in a 150nm CMOS technology. Due to its adaptive step size and its high sampling rate, the MPPT reaches the MPP within less than 0.65 ms with consumes less than 6.2 μW.