POWER SUPPLY FOR FEEDING AND IGNITING A GAS DISCHA

专利名称：POWER SUPPLY FOR FEEDING AND

IGNITING A GAS DISCHARGE LAMP

发明人：VENKITASUBRAHMANIAN,

Sreeraman,MASON, Clint,XIA, Yong-Ping,HU,Feng-Kang,SCHLEJEN, Jacob

申请号：EP97917376.0申请日：19970505公开号：EP0838130A1公开日：19980429

摘要：A ballast for a gas discharge lamp includes a detection circuit which detects anoperating state of the lamp in which the lamp current for the column discharge of onepolarity is different from the lamp current for the column discharge of the other polarityby detecting the DC component of the voltage across the discharge lamp. The detectioncircuit includes (i) a device coupled such that a DC voltage is imposed there across whenthe lamp current is different for the column discharge according to one polarity versesthe other polarity, and (ii) a sensing circuit for sensing the DC voltage across the device.The device may be a capacitive device, and in a particularly inexpensive implementation, isa DC blocking capacitor or a ballast capacitor. The sense circuit senses when the DCvoltage across the device exceeds a threshold value, which may corresponds to fully-rectified state of the lamp or more favorably, to a lesser state of imbalance. In anotherembodiment, the variance in the DC voltage across the lamp is detected at the midpointof a bridge inverter. A control circuit changes the output of the ballasting circuit whenthe DC voltage exceeds the threshold value to turn off the lamp or to recurrently cycle

the lamp on and off to signal the user that the lamp needs to be changed.

申请人：Philips Electronics N.V.

地址：Groenewoudseweg 1 5621 BA Eindhoven NL

国籍：NL

代理机构：Evers, Johannes Hubertus Maria, et al

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