Ballast Design
Hello,
You can find the T5 spec here:
www.tetech.nl/divers/TLspecificaties.pdf. I will leave it there for 10 days.
Some things to remember,
Some regions (like Europe) have strict regulations on power factor, so just a mains rectifier with capacitor will not be sufficient.
The suppliers of controllers ST, IRF, AVR ATMEL have nice application notes to get an idea of the basics.
When you want to make a dimmable ballast, it is important to "feed" the filaments to keep them at the correct temperature to avoid permanent damage to the filament's coating. When you don't heat the filaments during dimmed operation, lamp-life will be extremely short. Some suppliers describe variable frequency schemes to facilitate easy dimming. If you would like to use such an operating scheme, do a careful evaluation to make sure that you are within the T5 specs.
As you might know, reducing the lamp current, increases the lamp voltage. Your design needs sufficient open loop voltage to keep the lamp going at low lamp current.
Other thing is that there maybe requirements for end-off-life detection mandatory for your region. If this ballast design is for mass production, getting the standards is a must.