GB771940A - Improvements in or relating to circuits comprising gas and/or vapour filled electric discharge tubes - Google Patents

Abstract

771,940. Supply systems for space-discharge tubes. PHILIPS ELECTRICAL INDUSTRIES, Ltd. March 9, 1955 [March 12, 1954; Sept. 18, 1954], No. 6930/55. Class 38 (4). In a circuit comprising a gas and/or vapourfilled electric discharge tube 1, e.g. a fluorescent lamp, having two filament electrodes, 8, 9 and a combined filament heating and arc discharge current supply transformer 2, one, 9, of the electrodes is connected in series with a first winding 12 of a separate auxiliary transformer 11 and the two in series are connected across a secondary winding 3-13 of the transformer 2, and the other electrode, 8, is connected across a second winding 10 of the auxiliary transformer 11; said auxiliary transformer has no more than the two windings which within the transformer are electrically insulated from each other, and has the property of low impedance when on load, but high impedance when on no load, whereby should one filament heating circuit be interrupted the impedance of the winding in the other circuit becomes so high that the electrode therein is not brought to an electron-emissive temperature, thereby preventing initiation of the lamp when one electrode is unheated. As shown, the transformer 2 is autowound, comprising a primary winding 3-5, an arc discharge supplying secondary winding 3-4 and two filament heating secondary windings 3-13 and 14-4, all determined by tapping points on a single coil, and the latter winding supplying electrode 8; in another embodiment, Fig. 1, not shown, the electrode 8 is connected across only the winding 10. The lamp may have on the inner or outer side of its envelope an electricallyconductive coating, not shown, to facilitate ignition. Suitable valves and constructions of circuit components are described in the Specification. Specification 772,525 is referred to.