AC-to-DC converter incorporating a chopper and charge-pump circuit combination

摘要

An AC-to-DC converter for providing a step-down output DC voltage from an AC voltage source. The converter includes a rectifier connected to the AC voltage source to provide therefrom a rectified DC voltage to a step- up chopper. The chopper includes an inductor and a switching element which is connected in series with the inductor across the rectifier and which is driven to periodically turn on and off so as to store into the inductor an energy from the rectified DC voltage when the switching element is turned on and to release the energy from the inductor through a blocking diode to a charge-pump circuit when the switching element is turned off. The charge-pump circuit is connected to receive the energy released from the inductor as well as from the rectifier to accumulate a first voltage and provides a divided voltage of the first voltage to charge a smoothing capacitor by the divided voltage so as to develop thereat the step-down output DC voltage for driving a load. The converter further includes a switch which is turned on during at least a portion of an ON-period of the switching element in order to connect the smoothing capacitor to the charge-pump circuit for charging the smoothing capacitor by the divided voltage. The switch is turned off during an OFF-period of the switching element in order to disconnect the smoothing capacitor from the chopper.