Starting and dimming circuit for fluorescent lamps

Claim 2

Starting and dimming circuitry for a double ended fluorescent lamp having a discharge sustaining fill of mercury and an emitting filament at each end; comprising an AC power source, a first circuit means for applying a voltage across said lamp including said lamp and the secondary winding of a voltage step-up transformer having it primary winding connected across said power source, and a second circuit means for simultaneously applying a voltage across said filaments thereby to start lamp discharge, said second circuit means including separate secondary windings of said transformer each being connected in series with one of said filaments, said first circuit means further including impedance means for limiting current flow through said lamp, and means for selectively introducing additional impedances into said first circuit to selectively further limit current flow through said lamp, said means for selectively introducing additional impedance means into said first circuit means comprising two capacitors having different values, circuit connections and switching means for selectively connecting said two capacitors in series with said lamp either in parallel with each other, in series with each other or individually.

Claim 3

Starting and dimming circuitry for a double end fluorescent lamp having an emitting filament at each end; comprising an AC power source, a first circuit means for applying a starting voltage across said lamp including said lamp and the secondary winding of a voltage step-up transformer having its primary winding connected across said power source, and a second circuit means for simultaneously applying a voltage across said filaments, said second circuit means including separate secondary windings of said transformer each being connected in series with one of said filaments, said first circuit means including a first impedance means for limiting current flow through said lamp after starting, and means for further limiting current flow through said lamp to a maximum below that limitation effected by said first impedance means and for selectively reducing current flow through said lamp below said maximum comprising a first capacitor in said first circuit connected in series with said lamp and said first impedance means, a plurality of disconnected capacitors having different values, circuit connections and switching means for selectively connecting each of said plurality of disconnected capacitors in parallel with said first capacitor.

Claim 4

Starting and dimming circuitry for a double end fluorescent lamp having an emitting filament at each end; comprising an AC power source, a first circuit means for applying a starting voltage across said lamp including said lamp and the secondary winding of a voltage step-up transformer having its primary winding connected across said power source, and a second circuit means for simultaneously applying a voltage across said filaments, said second circuit means including separate secondary windings of said transformer each being connected in series with one of said filaments, said first circuit means including a first impedance means for limiting current flow through said lamp after starting, and means for further limiting current flow through said lamp to a maximum below that limitation effected by said first impedance means and for selectively reducing current flow through said lamp below said maximum comprising a first capacitor in said first circuit connected in series with said lamp and said first impedance means, a plurality of disconnected capacitors having different values, circuit connections and switching means for selectively connecting each of said plurality of disconnected capacitors in parallel with said first capacitor.

Claim 5

The starting and dimming circuitry claimed in claim 2 in which a relatively low ohmic resistor is connected in series with and adjacent to said first capacitor for subduing arcing when said first resistor is connected in parallel with one of said plurality of capacitors.