Importance

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Abstract

A discharge lamp circuit for ignition time control and overvoltage protection. The discharge lamp circuit includes drive circuitry, a sensing circuit, a timing circuit and a start-up circuit. The drive circuitry produces a strike voltage for a discharge lamp and provides a lamp current through the discharge lamp. The sensing circuit is provided to detect the lamp current. During lamp start-up, the timing circuit will develop a threshold voltage at the end of a predetermined period if the discharge lamp has not been lit yet, thereby controlling an ignition time of the drive circuitry. The start-up circuit allows the drive circuitry to keep on applying the strike voltage for the ignition time in order to start the discharge lamp before the threshold voltage is developed. Once the sensing circuit detects the absence of the lamp current, the start-up circuit also causes the drive circuitry shutdown.

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First Claim