Research On LCC Resonant Converter For High Power And High Output Voltage Applications

High output voltage power supply is widely used in high voltage applications such as medical X-ray machine and electrostatic precipitator. Conventional 50Hz high output voltage power supply suffers some drawbacks, such as large volume, large weight, low efficiency and poor dymamic response, which limit its further application. High frequency switching-mode high output voltage power supply overcomes these drawbacks and is becoming more and more popular. This paper focuses on the design of switching-mode power supply for high output voltage and high power applications.The high voltage transformer has significant parasitics such as leakage inductance and distributed capacitance due to the large turns ratio. In PWM converters, the leakage inductance causes undesirable voltage spikes which may damage devices, and the distributed capacitance results in circulating current which decreases the converter efficiency. This paper adopts LCC resonant converter with capacitive output filter in which the parasitics can be incorporated into the operation of the circuit so that less components are needed and the volume of the converter is reduced.LCC resonant converter with variable frequency control strategy can operate in continuous current mode (CCM) and discontinuous current mode (DCM) which are both discussed in this paer. The operation principle of LCC resonant converter operating in CCM is analyzed. A comprehensive design procedure for the converter is proposed based on its steady model, aiming to achieve zero-voltage-switching (ZVS) throughout the entire load range, to reduce the current stresses, to reduce the range of the switching frequency variation. Simulation results are given and a prototype rated 41kV/23kW is built to verify the design method.The operation principle of LCC resonant converter operating in DCM is analyzed. Zero-current-switching (ZCS) is achieved in this converter leading to less turn-off loss of IGBTs. A 66kV/72kW high voltage power supply is designed by means of gain characteristic which is attained through state equations. Simulation and experimental results are given to verify the effectiveness of the converter.