How to build a variable frequency controler?

Have you looked into electronic ballasts? I too found magnetic ballast flourescents annoying. The new ballasts switch 10KHz or more so don't visibly flicker at all. They only cost around $20. If you change to T-8 lamps you can get more lumens/less power/less flicker AND instant start. 3 ballasts and 6 T-8 lamps ran me $85 and the kitchen lights work great. GG

You need to go up in frequency to at least 3KHz. I say this because my wife always complained that reading by flourescent light gave her a headache. In 1960 I built a flourescent lantern for camping. It used an inverter running at about 3KHz - the state of the art in cheap Ge power transistors at that time. She could read by that light with no undesireable effects.

A GE lighting handbook I had at that time claimed that flourescent lamp efficiency increased with increasing frequency but leveled off in the upper KHz region. I don't recall it going above 5 or 10 KHz. You might search for more up to date results but if I were to build another, I would probly try something in the 10 to 30 KHz range.

Ted