An improved constant on/off time control scheme for photovoltaic DC/DC MIC

In the medium and large PV power generation systems, a popular commercialized module integrated converter (MIC), comprised of H-bridge Buck-Boost topology with a pass through switch, would increase the MPPT efficiency when irradiation mismatch occurs. This paper proposes a novel control structure that, in Boost-mode, it works with constant on time control, in Buck-mode, and it works with constant off time control. The scheme can achieve ultra-fast transient response to track the fast-changing input voltage reference from MPPT block. In constant on time control, an improved ramp compensation which is from input capacitor current would increase the efficiency compared with the popular inductor current ramp compensation. A digital and analog mixed technology would be taken in this paper to realize a low cost and high performance structure. The simulation and experiment have been taken to verify the good performance of this control scheme.