A dual pulse modulated five-element multi-resonant DC-DC converter and its performance evaluations

A five-element multi-resonant(LLC - LC) dc-dc converter can attain the wide range output power and voltage regulations by a practical-range pulse frequency modulation (PFM). It is a drawback, however, the power conversion efficiency deteriorates under the light load condition due to the conduction power loss in the LC anti-resonant circuit. As a solution to this technical problem, the pulse density modulation (PDM) is applied to the LLC-LC dc-dc converter as the submode power regulation scheme. In this paper, the essential performances of the new prototype of the PFM/PDM dual mode controlled LLC - LC dc-dc converter are presented with the experimental verification. The comparison between the LLC - LC dc-dc converter and the conventional LLC dc-dc converter is described in terms of efficiency as well as output voltage and power regulations characteristics, and the effectiveness of the LLC - LC dc-dc converter is evaluated from a practical point of view.