A digitally-controlled universal ballast based on magnetic regulator and PSoC device

In this paper a digitally controlled electronic ballast is presented. The ballast corresponds to the so-called universal ballasts, which are intended to operate different lamps with different power ratings without performing any change in the hardware. Thus, the ballast must incorporate some kind of circuitry so that the rated power of the connected lamp can be identified. The ballast must also adjust some of its parameters in order to supply the lamp adequately, which means: (i) as closer as possible to the nominal power and (ii) with the best efficiency. In the proposed ballast, the parameters selected to adapt the power circuit to each lamp are the switching frequency and the resonant tank inductance. The resonant tank inductance is varied by means of a magnetic regulator whose inductance can be adjusted through a dc bias current. The PSoC technology from Cypress is used to implement the control stage. Besides a microprocessor, this technology integrates in a single chip both analog and digital modules that can be programmed, thus reducing the external component count to a minimum. Experimental results from a laboratory prototype for lamp powers ranging from 15 W to 58 W are provided.