Constant-current, constant-voltage half-bridge resonant power supply for capacitor charging

A novel high-frequency half-bridge resonant converter is proposed which is suitable for application as a capacitor charging-power supply (CCPS). The proposed LCL-T resonant converter with clamp diodes is shown to have in-built constant current (CC) - constant voltage (CV) characteristics. Therefore, the need to sense output current and voltage, and their feedback control circuit, is eliminated. The converter operates in CC mode while the energy-storage capacitor is being charged and operates in CV mode when the voltage across the capacitor is regulated. The changeover from CC to CV mode or vice versa is automatic and smooth. The principle of operation of the converter is described and analysed. Considerations in the design of the converter as CCPS are presented. A prototype CCPS operating at 100 kHz is designed, built and tested. The experimental results verify the operation and application of proposed converter as a CCPS.