Interleaved LLC series converter with output voltage doubler

A parallel LLC series resonant converter with output voltage doubler is presented in this paper. The interleaved pulse-width modulation (PWM) technique is adopted to reduce the ripple current on input and output capacitors. The capacitance of input and output capacitors can be reduced. The high current stress drawback of conventional LLC resonant converter is overcome by the proposed converter. Thus the adopted converter can be applied for high output current applications. Based on the series resonant behavior, all power switches are turned on at zero voltage switching (ZVS) and the rectifier diodes can be turned off at zero current switching (ZCS). Thus the switching losses on power semiconductors are reduced. In the output side, the voltage doubler topology is adopted for high output voltage applications. Compared with the conventional LLC converter, the advantages of the proposed circuit are low ripple currents on input and output terminals, small size and light weight of transformer, and low conduction losses on power semiconductors. In this paper, the principle of operation, steady state analysis and design consideration of the proposed converter are provided and discussed. In order to validate the proposed converter, the laboratory experiments with 24V/40A output for server power supply were provided.