A high efficiency flyback micro-inverter with a new adaptive snubber for photovoltaic applications

Based on the hybrid operation of interleaved flyback micro-inverter in Discontinuous and Boundary Conduction Modes (DCM and BCM), a novel adaptive snubber is proposed in this paper. The proposed snubber limits the drain-to-source voltage overshoot of the flyback´s main switch during the turn-off process, enabling the use of lower voltage MOSFETs. It also recovers the stored energy in the leakage inductance of the flyback transformer and provides soft switching for the main flyback switch by limiting the rising slope of the MOSFET voltage during the turn off process resulting in higher efficiency. Exploiting the natural resonant of the flyback converter in BCM the adopted controller provides ZVS and ZCS for the main switch during the BCM operation. The operation of the flyback micro-inverter with associated controllers is analytically studied, and considerations for an optimum design aiming to higher efficiency are presented. Performance of the flyback micro-inverter with the proposed adaptive snubber and the corresponding controllers are experimentally verified based on a 250W interleaved flyback micro-inverter hardware setup.