For Darren

[reefburnaby]

Hi,

A relay electrically isolates, by physical means, the ballast outputs from the tube (and the other ballast). Think of a relay has an electrical switch that can be controlled electrically.

There is built in protection in side the ballast because they usually use HEXFET transistors as the main driver. They are very sensitive to voltage over-stress. Hence, they do have built in diode to prevent voltage over-stress from damaging the transistor. Voltage overstress can occur when there is feedback (aka refelections) from the load (lamps).

- Victor.