GB1249255A - Improvements in or relating to supply and ignition circuits for electric discharge lamps - Google Patents

Abstract

1,249,255. Supply circuits for discharge lamps. COMPAGNIE DES LAMPES S.A. 2 July, 1969 [31 July, 1968; 28 Nov., 1968], No. 33375/69. Heading H2H. A discharge lamp starting circuit includes a bi-directional semi-conductor element which is triggered so as to discharge a capacitor. The pulse produced is amplified by a ballast inductance connected to the lamp. In the circuit shown in Fig. 1, the starter circuit 8 is connected across A.C. supply terminals 6, 7 and is also connected to three tapping points on the ballast inductance 4. A capacitive voltage divider 9, 11 is also connected across the supply. When the main switch 5 is closed, a further capacitor 16 charges until its potential is sufficient to break down a diac 14b which triggers a triac 14a into conduction. The capacitor 9 now discharges through the section 4a-4b of the inductance 4 which then applies an amplified voltage to the lamp 1 resulting in ignition. The components are chosen so that the triac is gated at a peak of the supply voltage and maximum voltage is available. After ignition, resistors 12, 13 are arranged to maintain the voltage on the capacitor 16 below the value necessary to break down the diac 14b. In a modification, Fig. 2 (not shown), two triacs connected through an isolating transformer are used. Breakdown of the first triac generates a control signal for the second, through which the capacitor 9 then discharges as before.