Single stage, high power factor, lamp ballast

Unlike conventional ballasts requiring two cascaded stages, a new lamp ballast achieves near unity input power factor and high frequency sinusoidal lamp current in a single power conversion stage. A new discontinuous inductor current mode (DICM) of input inductor makes this possible by separating the input current shaping from high frequency output lamp ballasting function. The high efficiency is further enhanced by soft switching improvement, which is provided naturally through lagging current of the output resonant matching network. Design equations and experimental results verify all the advantages of the new lamp ballast