Rapid-start, low-pressure discharge lamp operating circuit

Abstract

To insure starting of an oscillatory circuit for fluorescent lamp operation scillating, for example, at about 35 kHz, two transistors are serially connected across the output of a rectifier adapted for connection to an a-c network, and the oscillatory circuit is additionally coupled to one of the a-c terminals of the rectifier, to apply to one of the transistors a triggering voltage which recurs with each undulation of the a-c network. The serially connected transistors each have an emitter resistor, which may be a PTC resistor, to balance currents through the transistors and eliminate unbalancing effects of manufacturing tolerances in the transistors. The PTC resistors additionally have current deviation regulating function. For multiple-lamp operation, oscillation control is derived from auxiliary windings on the ballast resistors and applied to the bases of the respective transistors (T1, T2) through an inductance network which insures spaced commutation or switching of the transistors and prevents overlap of conduction phases thereof.