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Lighting circuit for high-pressure discharge lamp for vehicles

  • US 5,142,203 A
  • Filed: 05/30/1990
  • Issued: 08/25/1992
  • Est. Priority Date: 06/02/1989
  • Status: Expired due to Term
First Claim
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1. In a lighting circuit for a high-pressure discharge lamp for a vehicle comprising:

  • a DC voltage booster circuit for boosting an input voltage from a DC voltage input terminal to provide an output voltage that is converted into an AC voltage to be applied to a discharge lamp;

    the improvement which comprises;

    an output voltage detector for detecting the output voltage of the DC voltage booster circuit and outputting a signal corresponding to a difference between the detected output voltage and a reference value;

    an output current detector for detecting an output current of the DC voltage booster circuit and outputting a signal corresponding to a difference between the detected output current and a reference value;

    a control circuit for generating a control signal corresponding to signals from the output voltage detector and the output current detector and applying the control signal to the DC voltage booster circuit to control the output voltage of the DC voltage booster circuit; and

    a timer means for applying a signal corresponding to the output voltage of the DC voltage booster circuit to the output current detector upon elapse of a time period corresponding to a turn-off time of the discharge lamp and adding said signal to a signal corresponding to said output current of the DC voltage booster circuit for transition to constant power control so as to make a result of said addition constant;

    whereby, in lighting the discharge lamp starting from a cool state, an operation of the timer means causes transition to constant power control using rated power after execution of control so as to supply power exceeding said rated power to the output voltage detector and the output current detector in order.

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