Variable frequency control of the zero-voltage switching two-inductor boost converter

The two-inductor boost converter has been previously presented in a Zero-Voltage Switching (ZVS) form where the transformer leakage inductance and the MOSFET output capacitance 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 resonant converter is required to operate with variable input output voltage ratios. This paper studies the variable frequency control of the ZVS two-inductor boost converter to secure an adjustable output voltage range while maintaining resonant switching transitions. The design method of the resonant converter is thoroughly investigated and explicit control functions relating the circuit timing factors and the voltage gain for a 200 W converter are established. Three sets of theoretical, simulation and experimental waveforms are provided for specific operating points. A variation of the basic circuit, the resonant converter with a voltage clamp, which is capable of operating with a wider output voltage range but a lower switch voltage stress, is also given at the end of the paper.