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Feedback control system of an electronic ballast which detects arcing of a lamp

  • US 5,770,926 A
  • Filed: 12/30/1996
  • Issued: 06/23/1998
  • Est. Priority Date: 12/28/1995
  • Status: Expired due to Term
First Claim
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1. A feedback control system for an electronic ballast which drives a lamp, the feedback control system comprising:

  • a multiplier configured to receive a feedback signal from the electronic ballast and a power signal to output a first signal which is proportional to the product of the power signal and the feedback signal;

    a preheating controller configured to receive a preheating control signal and further configured to output a preheating current, for preheating the lamp, responsive to the preheating control signal;

    an adder configured to receive the first signal and the preheating current and produce a second signal corresponding to the sum of the first signal and the preheating current;

    a restart and time controller configured to receive the second signal and a first reference signal, wherein the first reference signal corresponds to a standard operating voltage of the electronic ballast, and further configured to output the preheating control signal responsive to the second signal;

    a first difference amplifier configured to receive the first reference voltage and the second signal and output a third signal which corresponds to the difference between the first reference voltage and the second signal;

    a transconductance circuit configured to receive the third signal, amplify the third signal, integrate the third signal and output a fourth signal which corresponds to the third signal;

    a second difference amplifier configured to receive the fourth signal, a second reference signal, wherein the second reference signal corresponds to a standard operational current of the electronic ballast, and a fifth signal, wherein the fifth signal corresponds to the power signal, and output a sixth signal, wherein the sixth signal corresponds to the difference between the sum of the second reference signal and the sixth signal, on one hand, and the fourth signal; and

    an oscillator &

    output driver configured to receive the sixth signal and coupled to the electronic ballast, wherein the oscillator &

    output driver is further configured to generate a control frequency to be output to the electronic ballast, wherein the control frequency corresponds to the sixth signal.

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