LLC resonant converter with shared power switches and dual coupled resonant tanks to achieve automatic current sharing

In this paper, a novel LLC resonant converter with parallel input and parallel output circuit topology is proposed to achieve the good performance of reduced switch count and medium power compared with conventional parallel half-bridge resonant converter. The proposed LLC resonant converter has two resonant circuits, two resonant circuits use the same power switches to transmit power so that the switch counts are reduced compared with the conventional two-phase LLC resonant converter. The resonant inductors of each resonant circuit are shared to achieve automatic resonant current sharing performance and then to balance the current stress of passive elements, such as transformer, secondary-side rectifier even sough there are components tolerance of each resonant circuit. Mathematical model based on Fundamental Harmonic analysis (FHA) is built. The FHA analysis shows that there is same ZVS and ZCS performance with conventional LLC Converter. Two-phase conventional LLC converter and proposed LLC converter can be analyzed. A 600W experiment prototype is built to verify the feasibility and excellent current sharing performance has been demonstrated. The experimental results are shown that the current sharing error of two tanks is smaller 5% at worst case. The resonant current error of each tank is only 2.5% at total rated load power with the proposed LLC converter.