Multiple ballasts operable from a single DC bus

A plurality of lighting ballasts (12, 14, 16) draw power from a single DC bus signal. A power factor correction circuit (10) rectifies and smoothes AC power to produce the DC bus signal. In order to prevent damage to the ballast (12) when a lamp (18) dies or is removed, the ballast (12) includes an...

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Bibliographische Detailangaben
Hauptverfasser:	NERONE LOUIS R, OBERLE JOSEPH C
Format:	Patent
Sprache:	eng
Schlagworte:	APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC,OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWERSUPPLY SYSTEMS CONTROL OR REGULATION THEREOF CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUTPOWER CONVERSION OR DISTRIBUTION OF ELECTRIC POWER ELECTRIC HEATING ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR ELECTRICITY GENERATION
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Beschreibung
Zusammenfassung:	A plurality of lighting ballasts (12, 14, 16) draw power from a single DC bus signal. A power factor correction circuit (10) rectifies and smoothes AC power to produce the DC bus signal. In order to prevent damage to the ballast (12) when a lamp (18) dies or is removed, the ballast (12) includes an AC switch that senses damaging conditions and responds by changing a resonant frequency of the ballast (12). The AC switch operates in 2-3 second cycles. While it is operative, it shunts current away from inductors (38, 40) of the ballast (12) causing a resonant frequency of the ballast (12) to change. At the end of the cycle, the switch turns off, but if a load fault is still present in the ballast (12) it activates again. Preferably, the AC switch has a response time of approximately 500 mus.