Abstract: An electronic ballast for discharge lamps comprises an open loop configuration of an impedance converter first stage and an inverter second stage linked by a limiting control stage. The impedance converter stage presents its load, passive or active, as input resistance. It draws a continuous current, through large RFI/EMI suppressing input inductors, which is switched discontinuously through a tank circuit using an energy transfer relationship based on the switch on-time and the inductance and capacitance of the tank circuit. The impedance converter stage supplies unregulated power to the inverter stage which operates stably at a fixed frequency. If an imbalance such as an overcurrent condition or an overvoltage condition develops in the system, the limiting control stage temporarily preempts the converter switching until stability is reestablished.

Abstract: The present invention relates to a method and apparatus for driving discharged lamps and which is adapted to maximize the luminous efficiency of a discharged lamp and its associated electronic driving apparatus. This is accomplished through the power sourcing characteristics of the driver, by causing the required power to dissipated while maintaining the power factor in the lamp as near unity as possible with the real components available for the implementation of the apparatus.