Wide adjustable range LLC resonant converter's maximum switching frequency for realizing the ZVS operation

In this paper, the FHA and a simple TDA approaches have been used to derive the normalized maximum switching frequency of wide adjustable range LLC resonant converter for realizing the ZVS operation even under the worst-case conditions. By accounting the resonant current higher harmonics, more accurate expressions are derived. These analyses demonstrate that the normalized maximum switching frequency depends on the dead-time and the converter inductance ratio. It also depends on the ratio of the converter resonant capacitor and the effective capacitance appeared in parallel with the power MOSFETs drain-sources. The simulated and experimental results are in good agreement with the derived expressions based on these analyses. Soft switching is achieved for all power devices in inductive region, by choosing the dead-time and maximum switching frequency, properly. Developed prototype of the converter has been tested under different loads (0-3 A dc) and input voltages (320-370 V dc) to achieve an output voltage, adjustable in a wide-range (35-165 V dc), for using as an ion implanter Arc power supply.