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Lamp ballast system

  • US 5,023,521 A
  • Filed: 12/18/1989
  • Issued: 06/11/1991
  • Est. Priority Date: 12/18/1989
  • Status: Expired due to Fees
First Claim
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1. A ballast circuit for a fluorescent lamp, comprising:

  • means coupled between the lamp and an alternating current power supply for limiting changes in current flow to the lamp;

    means coupled between the lamp and the power supply for correcting the power factor between the lamp and the power supply and for controlling current flow in the circuit;

    electronic starter means coupled across electrodes of the lamp for providing current through said electrodes for preheating said electrodes, said starter means comprising a triac coupled across said electrodes, said triac having a trigger input coupled to a diac that in turn is coupled to a capacitor coupled to said power supply so that said triac is triggered whenever a sufficient voltage builds up across said capacitor to trigger said diac, said triac and means for limiting current changes being disposed such that termination of triggering of said triac causes a sufficient voltage pulse to be produced across said electrodes to produce an arc thereacross;

    a snubber circuit coupled across said triac and comprising a resistor and capacitor connected in series so that said starter means is prevented from latching at the triggering point of said triac; and

    a diode and resistor coupled in series to form a preheating current path which in turn is coupled across said electrodes thereby to provide additional preheat current through said electrodes during every other half cycle of said current prior to production of said arc.

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