Synthesis of buck converter based current sources

Abstract

Ripple free DC or AC current source can be implemented by operating a switching converter in current mode control and setting the switching frequency much higher than the operating frequency. However, due to presence of the output filter across the load, it exhibits deviation from the ideal output impedance characteristics of an ideal current source. In this paper, a DC and an AC current source are presented which provides low ripple output current without sacrificing the high output impedance characteristics of an ideal current source. The DC and AC current sources are realized using a buck converter and a voltage source inverter, respectively with a coupled LL-LC output filter replacing the traditional LC output filter. The low ripple output current is obtained by utilizing the notch behavior of the coupled LL-LC filter. The operating principle of the proposed current source structures are explained in details. The performances of the proposed current sources are validated using simulations and experiments. The proposed DC current source and sinusoidal AC current source shows only 0.4% and 1.33% ripple content at their output current, respectively.