Small-signal modeling of discharge lamps through step response and its application to low-frequency square-waveform electronic ballasts

In this paper, a simple method to obtain the small-signal model of discharge lamps, and particularly metal halide lamps, is proposed. A DC voltage source with a series resistor is used to supply the lamp at the required power level. Then, the lamp response against an input voltage step transient is analyzed. From this analysis, the parameters of the equivalent lamp model can be calculated. The proposed method allows obtaining the lamp model in a straight manner from a single test. With this technique, a 35W metal halide lamp is modeled at two different power levels. A validation circuit, which includes a resistive ballast and a capacitance, is analyzed to evaluate the possibilities of the proposed modeling technique. The obtained experimental results are in good agreement with the theoretical analysis. The derivation of a time domain lamp model for SPICE-based computer simulators is also introduced. Finally, an example of application in low-frequency square-waveform electronic ballasts is presented.