LLC resonant high-voltage DC-DC converter with voltage multiplier rectifier

In this paper, a LLC resonant DC-DC converter with voltage multiplier (VM) rectifier is proposed. The proposed converter circuit consists of four main components, which are the full bridge inverter, a resonant tank (LLC), a high voltage transformer, and a high voltage VM circuit. The proposed circuit regulates the output voltages by narrowly varying the switching frequency. The LLC resonant circuit is utilized to retrieve the energy trapped in the leakage inductance of the transformer and to achieve the zero voltage switching feature. The resonant circuit also increases the conversion efficiency. A high voltage transformer is used to step up the AC voltage, and then converted to DC voltage by rectifier. With the equivalent circuit derived based on the first harmonic approximation method, the input-output responses and the DC characteristics in the frequency domain are obtained. The key steady-state waveform and the circuit operation are presented. Finally, an example of the proposed LLC resonant converter with 50V input voltage and 6kV output voltage are simulated and validated by the experimental results.