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A circuit and method for running a metal halide arc discharge lamp from an AC power source. The circuit includes a rectifier for producing a DC voltage. The lamp is resistively ballasted by a current limiting filament connected in series with the lamp. The circuit includes a switch that closes durin

A circuit and method for running a metal halide arc discharge lamp from an AC power source. The circuit includes a rectifier for producing a DC voltage. The lamp is resistively ballasted by a current limiting filament connected in series with the lamp. The circuit includes a switch that closes during start up of the lamp so that the resistive filament is energized to provide immediate light prior to the lamp entering the normal run mode.

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A circuit and method for running a metal halide arc discharge lamp from an AC power source. The circuit includes a rectifier for producing a DC voltage. The lamp is resistively ballasted by a current limiting filament connected in series with the lamp. The circuit includes a switch that closes durin

A circuit and method for running a metal halide arc discharge lamp from an AC power source. The circuit includes a rectifier for producing a DC voltage. The lamp is resistively ballasted by a current limiting filament connected in series with the lamp. The circuit includes a switch that closes during start up of the lamp so that the resistive filament is energized to provide immediate light prior to the lamp entering the normal run mode. rminals are energized by said source of AC power; a valley fill circuit having input and output terminals; said input terminals of said valley fill circuit connected to said DC output terminals of said rectifying circuit; an inverter circuit having input terminals connected to said output terminals of said valley fill circuit and producing a high frequency drive voltage for driving a lamp current through said at least one gas discharge lamp when said AC input terminals are energized by said source of AC power; said inverter circuit being adapted to draw current substantially only from said source of AC power and through said rectifying circuit for a time which is greater than 90° of each 180° line frequency half cycle; and a cat ear circuit connected to said source of AC power, said cat ear circuit being adapted to conduct current for a first relatively short time following a first zero crossing of said line voltage and for a second relatively short time prior to the next zero crossing of said line voltage, thereby to reduce the total harmonic distortion of the current drawn from said source of AC power below 33.3%. 9. The electronic ballast of claim 8, wherein the total harmonic distortion of the current drawn from the source of AC power is below about 20%. 10. The electronic ballast of claim 8, wherein said cat ear circuit comprises a cat ear power supply. 11. The electronic ballast of claim 8, wherein said cat ear circuit draws current from said source of AC power only when said line voltage is less than a predetermined absolute value. 12. The electronic ballast of claim 8, wherein said cat ear circuit draws current from said source of AC power only when said current drawn by said inverter circuit from said source of AC power is substantially zero. 13. The electronic ballast of claim 8, wherein said cat ear circuit draws current from said source of AC power at least when said current drawn by said inverter circuit is substantially zero. 14. An electronic ballast for driving at least one gas discharge lamp from a source of AC power which has a substantially sinusoidal line voltage at a given line frequency, comprising: a rectifying circuit having AC input terminals and DC output terminals; said AC input terminals connectable to the source of AC power; said rectifying circuit producing a rectified output voltage at its said DC output terminals when said AC input terminals are energized by said source of AC power; a valley fill circuit having input and output terminals; said input terminals of said valley fill circuit connected to said DC output terminals of said rectifying circuit; said valley fill circuit including an energy storage device directly chargeable from said DC output terminals through an impedance and a first controllably conductive device, said impedance carrying only charging current for said energy storage device; an inverter circuit having input terminals connected to said output terminals of said valley fill circuit and producing a high frequency drive voltage for driving a lamp current through said at least one gas discharge lamp when said AC input terminals are energized by said source of AC power; and a valley fill control circuit coupled to said energy storage device and operable to enable said energy storage device to draw charging current from said rectifying circuit for a time greater than 90° of each 180° line frequency half cycle, whereby the current drawn from the source of AC power has a total harmonic distortion below 33.3%. 15. The electronic ballast of claim 14, wherein said valley fill control circuit includes an inductor. 16. The electronic ballast of claim 14, wherein said valley fill control circuit includes a tapped inductor. 17. The electronic ballast of claim 14, wherein said first controllably conductive device is a MOSFET. 18. The electronic ballast of claim 14, wherein said inverter circuit includes said first controllably conductive device; whereby said first contro llably conductive device serves a dual purpose. 19. The electronic ballast of claim 14, wherein said inverter circuit includes series connected second and third controllably conductive devices connected across said input terminals of said inverter circuit, whereby each of the three controllably conductive devices are independent devices. 20. An electronic ballast for driving at least one gas discharge lamp which draws ballast input current from a source of AC power which has a substantially sinusoidal line voltage at a given line frequency, comprising: a rectifying circuit having AC input terminals and DC output terminals; said AC input terminals connectable to the source of AC power; said rectifying circuit producing a rectified output voltage at its said DC output terminals when said AC input terminals are energized by said source of AC power; a valley fill circuit having input and output terminals; said input terminals of said valley fill circuit connected to said DC output terminals of said rectifying circuit; an inverter circuit coupled between said output terminals of said valley fill circuit and said at least one gas discharge lamp and including series connected first and second controllably conductive devices; said inverter circuit producing a high frequency drive voltage for driving a lamp current through said at least one gas discharge lamp; an inverter control circuit coupled to and independently controlling the conduction times of said series connected first and second controllably conductive devices; said inverter control circuit being operable to reduce the conduction time of said first controllably conductive device to produce a relatively narrow pulse and, simultaneously, increase the conduction time of said second controllably conductive device to produce a relatively wide pulse during the period around the instantaneous peak absolute voltage of each line frequency half cycle, whereby the magnitude of the envelope of said lamp current humps down below the magnitude that would occur in the absence of said changes in said conduction times, causing a reduction in the current crest factor of said lamp current, and whereby said increase in the conduction time of said second controllably conductive device causes said ballast input current to hump up above the magnitude that would occur in the absence of said increase in conduction time, causing a reduction in the total harmonic distortion of said ballast input current. 21. The electronic ballast of claim 20, wherein the lamp current has a current crest factor below 2.1. 22. The electronic ballast of claim 20, wherein the lamp current has a current crest factor below about 1.7. 23. The electronic ballast of claim 20, wherein a current only flows through said first controllably conductive device when no current flows through said second controllably conductive device and vice versa. 24. The electronic ballast of claim 20, wherein current flows alternately through said first and second controllably conductive devices. 25. The electronic ballast of claim 20, wherein a sum of said conduction times of said series connected first and second controllably conductive devices is the period of said high frequency drive voltage. 26. The electronic ballast of claim 20, wherein said valley fill circuit comprises a buck converter circuit. 27. The electronic ballast of claim 20, wherein said valley fill circuit comprises a switched resistor circuit. 28. The electronic ballast of claim 20, wherein said inverter control circuit includes a micro-controller. 29. The electronic ballast of claim 20, wherein said inverter control circuit includes a digital signal processing circuit. 30. The electronic ballast of claim 20, wherein said inverter control circuit includes an ASIC. 31. An electronic ballast for driving at least one lamp comprising: a rectifying circuit operatively connectable to an AC line; a current drawing circuit connected across said rectifying circuit; and an