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Discharge lamps require high ignition voltage from typically one to several kilovolts for cold-start, but have low on-state voltage of typically 100 V. For discharge arc monitoring purposes, it is difficult or uneconomical to implement voltage sensor to cover such a wide range of voltage. In this paper, a nonintrusive and electrically isolated method, based on the single-sensor principle, is used to derive the system parameters and variables for system monitoring and control purposes. Unlike the traditional resistive potential divider for voltage feedback, the proposed method is nondissipative. Only one coupled winding is used to derive the converter inductor voltage, from which the lamp power, lamp arc resistance and inverter dc link voltage can be accurately derived. The proposal is verified with good agreement between derived values and measurements in an electronic ballast-fluorescent lamp system. The proposal can be useful in applications in which sensing the voltage across the load is either difficult or costly.
Date of Publication: July 2005