A novel fixed off-time control method for single-phase micro-inverter without sensing inductor current

This paper proposes a novel fixed off-time control method for single-phase micro-inverter operating in discontinues conduction mode. In this method, the off-time of the active switch is fixed to a constant value over the whole power level. The on-time of the active switch is obtained for current shaping without sensing inductor current. The proposed method has two advantages. One is that the switching frequency variation is narrowed compared with the micro-inverter operating in boundary conduction mode. So the frequency-dependent switching losses and inductor core losses are reduced and the efficiency in light load condition is improved. The other advantage is that the control method does not need sensing inductor current. So the control is simplified and the hardware cost is reduced. The control method is detailed in this paper and is verified by simulation and experimental results.