An analysis of the ZVS two-inductor boost converter under variable frequency operation

The two-inductor boost converter has been previouslypresented in a zero-voltage switching (ZVS) form wherethe transformer leakage inductance and the MOSFET outputcapacitance can be utilized as part of the resonant elements.In many applications, such as maximum power point tracking(MPPT) in grid interactive photovoltaic systems, the resonanttwo-inductor boost converter is required to operate with variableinput output voltage ratios. This paper studies the variablefrequency operation of the ZVS two-inductor boost converter tosecure an adjustable output voltage range while maintaining theresonant switching transitions. The design method of the resonantconverter is thoroughly investigated and explicit control functionsrelating the circuit timing factors and the voltage gain for a 200-Wconverter are established. The converter has an input voltage of20 V and is able to produce a variable output voltage from 169 Vto 340 V while retaining ZVS with a frequency variation of 1 MHzto 407 kHz. Five sets of theoretical, simulation and experimentalwaveforms are provided for the selected operating points overthe variable load range at the end of the paper and they agreereasonably well. The converter has achieved part load efficienciesabove 92% and an efficiency of 89.6% at the maximum power of200 W.