Energy Efficient Stepwise Charging of a Capacitor Using a DC-DC Converter With Consecutive Changes of its Duty Ratio

Energy storage technology is becoming more and more important in today's environmentally conscious society. In the conventional method of directly charging a capacitor under a constant power supply voltage, the amount of energy dissipation is the same as the energy stored in the capacitor. In this paper, we propose the stepwise charging of a capacitor by consecutively changing the duty ratio of the DC-DC down converter. In N step charging, the energy dissipation is reduced to one Nth when compared with the conventional direct charging. The reduction of the dissipated energy is verified by SPICE simulations and by breadboard experiments, through which an energy reduction of one fourth and one eighth is confirmed from the measured power supply currents in four and eight step charging, respectively.