A Master-and-Slave Resonant Tank Switch Approach To Effectively Reduce Frequency Range in LCC Converter

A new master-and-slave resonant tank switch approach is proposed to realize narrow switching frequency range and whole range zero voltage switching (ZVS) for series-parallel resonant converter (LCC) with wide operation range. A systematic switch strategy employing paralleled series capacitor (C
_s
) tanks is fully explored. A master resonant tank is firstly derived based on converter actual operation range. A series of slave resonant tanks are derived using geometric progressions, as 1/2
ⁱ
. The voltage gain is divided into different pieces and different resonant tanks are employed. The switching frequency range maintained similar for each segments. A 5kW SiC LCC converter is built to demonstrate the proposed concept. Three resonant tanks with C
_s
of 5nF, 10nF and 20nF are adopted respectively. With single resonant tank of C
_s
equaling to 20nF, switching frequency need to be adjusted from 280 kHz to 470 kHz for gain range from 0.3-1.05. With the proposed master-and-slave tank switch technique, switching range is shrink to the 390 kHz to 470 kHz for the same gain range by adopting two slave tanks. A 58% reduction of frequency range is achieved.