GB1378465A - Power supply arrangement for fluorescent tubes - Google Patents

Abstract

1378465 Supply systems for gas discharge lamps TAKOLOMYJEC 3 July 1973 31744/73 Heading H2H In a circuit arrangement wherein a plurality of fluorescent lamps are supplied from a D.C. supply by way of a transistor oscillator switching means are provided to enable the oscillator to function and supply the lamps when only a single lamp is required or more than one lamp are required simultaneously. The oscillator comprises a single transistor Q1 and a transformer T having primary, feedback and secondary windings N1, N2, N3 respectively. The arrangement includes two fluorescent lamps TL1, TL2 having filamentary electrodes and a switch SA, SB is provided to select one lamp TL1 or both lamps as required. When one lamp TL1 only is required the switch SA, SB is placed in the ON1 position such that the secondary winding N3 is connected to the filaments of the lamp TL 1 and to a lamp starting electrode M. In this position the filament F1 of the lamp TL1 is in series with the feedback winding N2 and the base of the transistor Q 1 and is therefore preheated by the feedback current. The oscillator thus oscillates at about 3À4 kilohertz at 124 volts output. With the switch SA, SB in position ON2 the secondary winding N3 is connected to the lower filaments of both lamps TL1, TL2 so that the discharge paths thereof are in series. In this position of the switch both filaments F1, F2 of the lamps receive feedback current so as to be preheated whereupon the oscillator output frequency increases to 10 kilohertz and the voltage to 250. The diode Q2, resistor R2 and capacitor C2 provide a transistor anti-saturation device. In other embodiments three or more lamps are used in any combination, the filaments F1, F2 may be in series, capacitors may be introduced into various parts of the circuit and the filament F2 may be connected to the collector of the transistor. A switch may be provided between the filaments F1, F2.