Electronic & Transformer Engineering Limited

Vusion International Limited

Donald R Ensor

David P Ball

A circuit suitable for the instantaneous starting, continuation, and interruption of current through one or more gasfilled discharge tubes, in particular fluorescent lamps, is described. The circuit and lamp heaters are energized before instantaneous control can occur. One preferred silicon controlled rectifier (SCR) is used with a bridge rectifier. The SCR has the dual role of causing the capacitor to discharge through the pulse transformer, the secondary pulse voltage of which thereby causes the arc to strike immediately upon application of gate current, and then maintianing the lamp current as long as a supply of SCR gate current is provided. A second preferred control device, a TRIAC, is used without a bridge rectifier and again has a dual role of pulse-starting and maintaining current. This type of device is more conveniently arranged to provide for a dimming function as well. Applications include 'flashing' advertising signs, general illumination, and signals.

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Western Springs, New Zealand

Donald R Ensor