An Improved IPOS LLC Resonant Converter With Sub-Module Output Voltage Sharing in Low Ripple High-Voltage Applications

This paper proposed an input-parallel and output-series (IPOS) LLC resonant converter for applications with high voltage gain and low ripple, which considers the sharing of submodule output voltages. The resonant converter proposed has an integrated magnetics, which improves the utilization of the core. The reason is because magnetic fluxes can be superimposed or cancelled each other when the resonant currents are interleaved. Moreover, the influence of parameter mismatch in the resonant tank on voltage and current sharing in IPOS-LLC was analyzed based on the passive impedance theory. The results show that, by selecting smaller quality factors and using N-connections in high-voltage applications, the sharing of output voltage among modules can be well reflected, despite tolerances of the resonance parameters. Meanwhile, the voltage stress distribution of the rectifier diodes in each submodule is optimized, which improves the reliability of the circuit. By using the aforementioned conclusions, a prototype with 90 kHz, 40 V/4.8 kV, and 1.15 kW is established. The measured output voltage mismatch of 3.1% and voltage ripple rate of 0.16% at 3.7 nF output capacitance proves the effectiveness and correctness of the proposed resonant converter design.