Bifurcations in frequency controlled load resonant DC-DC converters

The complex behavior of load resonant converters is investigated by using a newly developed stability analysis tool. In this paper we specifically consider the series-parallel load resonant converter with L-C output filter, controlled by the frequency modulation technique. The close loop variable frequency control consists of a feedback loop and a PI controller with voltage controlled oscillator (VCO). The VCO is used to convert the error in output voltage into a change of frequency to control the voltage in close loop system. Two converter designs are considered with different combinations of L-C output filter. With the variation of the proportional gain, Neimark-Sacker and symmetry-breaking bifurcations are observed.