Characteristics Analysis of LLC and LCL-T Resonant Tank

Resonant converters have been widely used in many applications due to its soft switching capability and high efficiency characteristic. LLC and LCL-T resonant tanks are the most frequently used resonant topologies. For LLC resonant tank, at the series resonant frequency operating point, the output voltage is constant and independent of the load; at the parallel resonant frequency operating point, the output current is constant and independent of the load; for the LCL-T resonant tank, at the series resonant frequency operating point, the output current is constant. Although the characteristics of these resonant tanks have been investigated, the accuracy comparison among them are lack and unclear. Therefore, in this paper, the detailed derivations of these resonant tanks characteristics are presented; then, accuracy comparison among different characteristics are implemented with experimental results. The analysis results of this paper can provide guidance for engineers when analyzing and designing resonant converters.