GB1529755A - Arrangement for starting and feeding a discharge lamp - Google Patents

Abstract

1529755 Control systems for discharge lamps PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 18 Feb 1976 [21 Feb 1975] 06371/76 Heading H2H An arrangement for starting and feeding a high or low pressure gas and/or vapour discharge lamp has a normal starting mode and a further mode in which a few high voltage peaks are supplied if the lamp fails to start normally. The lamp 5 is in series with a stabilizing inductor 3 and is bridged by a starting circuit in series with a further inductor 9 and comprising components 22, 26, 31, 33 and 37 connected substantially as shown. As described, capacitor 26 charges via resistor 24 and Zener diode 25, until bidirectional voltage sensitive element 25 breaks down, turning on transistor 22 whereupon current flows through the lamp electrodes 4, 6 by way of resistor 20, primary winding 21 of a transformer and the conductive transistor 22. When this current reaches a constant value, the drive for the transistor disappears, the transistor then becoming non-conductive whereupon the voltage across capacitors 7, 8 increases to increase the voltage across the lamp when the lamp should normally start. In the case of difficult lamp a capacitor 37 receives a charge by way of resistors 31, 36 until it achieves the breakdown voltage of a Zener diode 33 whereupon a transistor 30 becomes conductive to short circuit the capacitor 26. In this condition the conduction of transistor 22 is delayed which results in a greater rise of voltage across capacitors 7, 8 and the lamp 5 to ensure the starting of the difficult lamp. In the event of an unacceptably high voltage across the lamp, resistors 39, 40 and a diode 41 render transistor 30 continuously conductive to render transistor 22 inoperative. The breakdown element 28 renders the starting operation ineffective when the lamp is operating normally. Transistor 22 may be replaced by a triac.