Applications of nonlinear impedance circuit composed of diodes and capacitors or inductors

摘要

The authors propose nonlinear impedance circuits, namely, a nonlinear capacitor circuit and a nonlinear inductance circuit, composed of diodes and capacitors or inductors. They present two applications of each circuit, in a rectifier and chopper. The structures of these circuits vary according to the direction of current or the polarity of the applied voltage because of the diodes' conducting and nonconducting states. Applying the nonlinear impedance circuit in rectifiers can substantially reduce the harmonics in the input current and therefore improve the power factor. The capacitor input rectifier using the nonlinear capacitance circuit satisfies the harmonics regulation of IEC class-A. The charge-pump type rectifier using the nonlinear inductance circuit also has a high power factor and a small third-harmonic component in the input current at heavy load. In the chopper applications, the Cuk converter using the nonlinear capacitance circuit has lower output voltage than the conventional one at the same duty ratio. The step-up chopper employing the nonlinear inductance circuit has a high step-up ratio that is about three at the duty of 50%, a small ripple in the output voltage, and a reduced current rating of the diodes.