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Starting and operating method and apparatus for discharge lamps

  • US 4,525,650 A
  • Filed: 01/10/1984
  • Issued: 06/25/1985
  • Est. Priority Date: 02/11/1982
  • Status: Expired due to Term
First Claim
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1. Apparatus for starting and operating miniature metal-vapor discharge lamp means, said apparatus having input terminals adapted to be connected across a source of AC potential of predetermined magnitude, and said apparatus having output terminals across which said discharge lamp means is adapted to be operatively connected, said apparatus comprising:

  • AC current-limiting and rectifying means having an input connected to said apparatus input terminals and operable to generate at the output thereof a current-limited low-ripple DC potential;

    a lamp means starting circuit comprising series-connected inductor means and capacitor means forming a resonant circuit, said starting circuit capacitor means connected across said apparatus output terminals, a blocking capacitor and a charging impedance connected in series with said starting circuit, and the series combination of said starting circuit, blocking capacitor and charging impedance connected across said output of said AC current-limiting and rectifying means;

    a pair of transistors comprising oscillator means electrically connected in series arrangement across said output of said AC current-limiting and rectifying means, and the connection between said transistors being electrically connected to said blocking capacitor means;

    air-core transformer means comprising a pair of feedback windings and a pair of driving windings, a first of said feedback windings connecting in series with said starting circuit inductor means and capacitor means, and the second of said feedback windings and a current-controlling impedance means connecting in parallel with said starting circuit inductor means and capacitor means, a first of said driving windings connecting in circuit between the base and the emitter of one of said transistors and the second one of said driving windings connecting in circuit between the base and the emitter of the other of said transistors; and

    trigger means responsive to initial energization of said apparatus to apply a turn-on pulse to the base of one of said transistors to initiate oscillations between said transistors to generate square waves;

    whereby after initial energization of said apparatus and until said lamp means is started said transistors alternately conduct to deliver square waves of current to said lamp means at an oscillation frequency determined by the resonant frequency of said starting circuit series-connected inductor means and capacitor means, and said air-core transformer having a magnetizing inductance such that after said lamp means is started said transistors alternately conduct to deliver square waves of current to said operating lamp at an oscillation frequency determined by the rate of current flow into said second feedback winding.

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