Renewable energy sources using photovoltaic (PV) systems in distributed generation networks are increasingly deployed. For PV panels, which cannot be directly connected to the grid, the inverter serves as a power electronic interface, and it relies on a stable input to produce a reliable output. The Maximum power point tracking (MPPT) DC-DC converter that acts as an interface between the PV array and an inverter is required to handle large input voltage variations due to variations in irradiation and temperature. Isolated zero voltage switching (ZVS) converters are being used in medium to high power and high voltage applications due to their capability to use the device parasitics to achieve ZVS, thereby reducing the switching losses. Hence these converters can be switched at a higher switching frequency that reduces the overall converter size. The phase shifted full bridge (PSFB) pulse width modulated (PWM) converter is popular among high voltage and medium to high power applications due to its ease of control for the wide variation in input voltage, zero voltage switching (ZVS), high power density, and low electromagnetic interference (EMI. However, the PSFB converter has an inherent problem. When the converter transitions from freewheeling to power transfer mode, the secondary side full bridge rectifier diodes experience a voltage overshoot due to an oscillating network formed by the leakage inductance of the transformer and parasitic capacitance of diodes.

Early attempts to solve the problem with passives were made, which are highly energy inefficient. The attempts to solve the problem using active snubbers require the snubber switches either to be switched at twice the switching frequency of the PSFB converter which increases the losses in the overall system or require the switches to handle the full load current. A similar snubber topology which was used for this work is used in the literature but the snubber is switched at twice the switching frequency of the PSFB converter and detailed analysis of PSFB converter with the topology is not reported.

The contribution of this work includes, 1) detailed analysis and design of an Active Adaptive Energy Recovery (AAeR) snubber used in PSFB, 2) a control methodology of the AAeR snubber that reduces its switching frequency while only a fraction of the full load current flows through AAeR snubber switch, 3) a clamping voltage that adapts to the changes in input voltage to reduce the voltage stress and voltage ringing magnitude on the secondary diodes and hence the EMI, 4) calculation of energy efficiency of the AAeR snubber. The performance of AAeR snubber is compared with the other approaches in the literature.