New AC-DC converters using switched-capacitor (SC) transformers are presented. The features of these circuits are as follows. (1) It does not contain any magnetic material. (2) The inrush current of the proposed converter is very small as compared with that of a condenser-input-type rectifier circuit. (3) It is realizable in a hybrid IC form. (4) It excels in size and weight when compared with reactor-type switching regulators of the same output power. As an example, an AC-DC converter using step-up SC transformers was built and tested to confirm the characteristics. The measured characteristics showed good agreement with the calculated ones.

An AC-DC converter using a new switched-capacitor (SC) transformer and its design are presented. The features of this circuit are as follows. (1) The maximum voltage of capacitors is 1/n times that of a condenser-input-type rectificer circuit, where n is the number of chargetransfer capacitors. (2) The output voltage ripple is small, since the equivalent smoothing capacitor value is n times that of conventional SC transformers (series-parallel switching type). Using the presented design method, each element value is designed from the specifications of a test circuit. The experimental results of the test circuit show that (1) the efficiency of the SC transformer is very high (95%), and the total efficiency is 74% due to the losses of the clock generator and the control circuit, (2) the maximum output power is 40 W, (3) the value of the inrush current of the tested converter is only twice the value of the steady state current. The measured characteristics showed good agreement with the calculated ones.