Improved variable capacitance device and its applications to resonant converters

A new variable capacitance device for use in power electronics is proposed. The capacitance of this device can be varied by DC control voltage. In the new device, constructed by ceramic capacitors, four well-balanced capacitors are bridge-connected. Therefore, the AC leakage current which flows from the control voltage terminals becomes extremely small. The series resistance for suppressing the leakage current can be removed unlike the former three-terminal device. This brings a marked decrease in the time constant as seen from the control voltage terminals. The transient response times are investigated in the case when this device is used as the resonant capacitor of resonant power converters.<<ETX>>