El-Cheapo Fluoro Ballast

This simple circuit can
start small (15W or less) fluorescent tubes such as those used in PC
board exposure and EPROM ultraviolet erasure
boxes. As you can see, the tube’s filament heaters are not used.
Instead, ignition is provided by a voltage tripler formed by diodes
D1-D3 and the two 6.8nF 2kV capacitors. At switch on, C1 charges up via
R1 until the gas in the tube breaks down (around 700V). C1 then
discharges through the tube, lowering the resistance enough to sustain
continual AC current flow. C1 then continues to act as the ballast, with
R1 included to prevent the three diodes shunting the tube on positive
mains half-cycles.

El Cheapo Fluoro Ballast Circuit

El-Cheapo Fluoro Ballast Circuit Diagram

Author: Adrian Kerwitz
Copyright: Silicon Chip Electronics

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