Research of LLLC resonant topology circuit

MA Xiaolin
(Acbel Electronic Company, Limited Hangzhou Branch, Hangzhou 310013, China)

Abstract: Aiming at the existing wider working frequency in the wide range output voltage application of LLC topology, a new LLLC resonant topology was proposed. By adding an inductance, the working frequency can be controlled with a narrow range in the same wide output as the LLC′s. As the addition of the inductance, the topology was comprised of four resonant elements and was named as LLLC topology. But there was the same design method each other. To fully understand the working principle of the circuit, the work process was given completely. Then the caculation of key parameters was provided. In particular,the mechanism of reducing working frequency was provided by comparative analysis. Finally, the prototype of 1500W was demonstrated with output voltage range of 43V~58V. The actual measurement results show that, its working frequency is between 110kHz and 270kHz and meets the design requirement. The perimental result shows that this circuit is effective.
Key words: LLC; LLLC; ZVS; ZCS; widerange