LLC converter with Taiwan Tech center-tapped rectifier (LLC-TCT) for solar power conversion applications

An LLC converter with Taiwan Tech center-tapped rectifier (LLC-TCT) is proposed in this paper. In addition to having zero-voltage switching operation on the MOSFETs and zero-current switching on the rectifier diodes inherited from its predecessor, the proposed converter has several additional features. For instance, the rectifier diodes are clamped to the output voltage due to the utilization of the clamping series-diode technique and the recovery of the transformer secondary leakage energy. Besides the output filter capacitor, the load currents are partly provided by the L-C-L filter cell constructed with the leakage inductance of the secondary windings and one clamping capacitor. As a result, the rectifier diode losses and the required high-voltage output filter capacitor can be reduced. These characteristics make it desirable for high frequency, high efficiency and high input-voltage and high output-voltage power conversion applications such as solar power conversion or larger size LED backlit LCD display applications. In addition to the operation principle and design considerations, an LLC with conventional center-tapped rectification circuit (LLC-CT) and the proposed LLC-TCT with 300-400-V input and 200V/400W output are implemented to demonstrate the feasibility and the superiority of the LLC-TCT over the LLC-CT.