Loss Reduction of LLC Converter Using Bridge-Capacitor

Current resonance type of LLC converter is widely used owing to their low switching losses; however, the problem is that they have a large transformer loss. We examine the reduction of AC resistance of the transformer winding and high coupling between the primary and secondary windings of the transformer, as a method for reducing the copper loss. In this case, it is necessary to consider the effects of the increase in stray capacitance between the primary and secondary windings of the transformer. This paper describes the influence of the loss due to the capacitance generated between the transformer windings when a noise filter is connected to the LLC converter. Furthermore, we propose a new method for reducing loss by connecting a bridge-capacitor between the primary and secondary sides of the transformer. The results of the new method are shown, and compared with those of the simulations to demonstrate effectiveness.