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AssigneePhilips Electronics North America Corporation
InventorPawel M. Gradzki
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A circuit arrangement for supplying a controlled substantially constant level of electrical power to a discharge lamp in a load circuit includes a feedback loop responsive to a comparison or difference between a power measure signal corresponding to electrical power consumed by the lamp and a reference signal corresponding to a desired consumed power. The power measure signal is formed by a power measure signal forming circuit which includes a one quadrant multiplier which receives at a pair of inputs respective lamp voltage and lamp current measure signals output from a sample and hold device arranged for sampling both a signal indicative of instantaneous lamp voltage and a signal indicative of instantaneous lamp current. The sampling is done at instants at which a signal which is indicative of the derivative of the lamp voltage passes through zero in a predetermined direction. The latter signal constitutes the current through a capacitor which is coupled at one end to a voltage that is indicative of the instantaneous lamp voltage and at the other end to a voltage clamp.
A circuit arrangement for supplying a controlled substantially constant level of electrical power to a discharge lamp in a load circuit, the arrangement including a feedback loop responsive to a comparison or difference between a power measure signal substantially corresponding to electrical power consumed by the lamp and a reference signal corresponding to a desired consumed power, which power measure signal is formed by a power measure signal forming circuit which includes a multiplier which receives at a pair of inputs respective lamp voltage and lamp current measure signals formed by sensing the load circuit, wherein the power measure signal forming circuit comprises a sample and hold device arranged for sampling both a signal substantially indicative of instantaneous lamp voltage and a signal substantially indicative of instantaneous lamp current in response to passage through zero of a signal which is substantially indicative of the derivative of the lamp voltage, the sample and hold device having a pair of outputs respectively feeding the pair of inputs of the multiplier.
Dependencies are inferred from the claim text.