Cost-Effective Implementation of a Digitally Controlled LLC Resonant Converter for Application in Server-and Telecom-PSUs

The LLC resonant converter has become very popular for use in high efficient DC-DC converters in past years. Whereas the good efficiency of the LLC converter was demonstrated before, the design engineer is faced now with the problem of a cost-effective and reliable implementation of the LLC converter for the purpose of mass production and broad applicability. In this paper a cost-effective design variant is presented, which combines the digital control facilities of a low cost DSP and his peripheral PWM features with the critical control needs of the synchronous rectification (SR), thereby dealing with the parasitic effects that complicate turn-off instant sensing via RDSon voltage drop of the rectifier MOSFETs. Additionally an adaptive voltage controlling approach is presented.