because i thought battery operated circuit should be much simpler and i thought this ccfl bulb will work on low voltage (12V maybe?) at its both pins during normal operation. but it seems to jump start this bulb still needs somesort of high voltage oscillator. my brain hurts listening to those advice esp when a schematics drawing is missing. i dont even know how a "ballast" work
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anyway, this is for my pcb photo resist / mask curing project using the uv bulb.
Ah, okay, let's back up a second. I thought you wanted to make a battery powered lamp as well. If you can operate the bulb from the mains then things can be greatly simplified, especially for a lamp that won't be operated very much.
A ballast in electronics is merely a means of limiting current - it could be a resistor, an inductor or even a capacitor.
In all cases you need to know, at a minimum, the voltage drop across the bulb during operation and the recommended current. The PL-9W (aka CFT-9W/G23) bulb I cracked open - which, coincidentally, is the same size/wattage as the 4 bulbs used in that UV nail drier - requires 59V volts at 0.18A. Starting the bulb requires a much higher voltage, however - 3x to 6x is typical - and this voltage varies inversely with temperature (hence the use of preheat filaments). You can skip preheating - at the cost of bulb life - by applying a much higher voltage during starting (up to 10x); this is what "instant start" lamp fixtures do.
There are MANY ways to operate fluorescent bulbs, and that may be a source of confusion here. If the peak of the mains voltage is sufficiently high to reliably start a bulb then either a resistor or capacitor can be used as the ballast, with the capacitor greatly preferred for efficiency reasons. In this case, 220V RMS mains should be more than sufficient to reliably start a PL-9W bulb, while starting from the 120V mains in the US would be marginal without some assistance from inductive kickback (hence the popularity of the choke/inductor type ballast in the US).
A passive ballast (whether a resistor, capacitor or inductor) needs to drop the difference between the RMS mains voltage and the bulb voltage at the desired operating current. More specifically, driving a bulb rated for 59V at 0.18A from 220V/50Hz mains requires a ballast resistance (or impedance, to be more correct) of 894 ohms. That can be achieved with a resistor, of course (but watch out for the nearly 30W in loss!), or a 3.56uF capacitor or a 2.846H inductor.
If going the capacitor route then you need to use an appropriate type for direct mains operation. Examples would be any X2 or Y2 rated capacitor (though you'll require a whole bunch of them to get to 3.56uF), metallized or foil plastic film capacitors (e.g. - MKP, MKT, FKP, FKT, etc.) of sufficient voltage rating (usually a DC rating >430VDC will be required), oil filled "motor run" and other various but less common types.
Otherwise it should be possible to buy the appropriate inductor (aka "magnetic") ballast from a hardware or electrical supply store. You'll also need a socket for the bulb. Usually 9W twin tube bulbs are coded as "G23" base, but could also be GX23. These two bases might look the same, but they are not interchangeable.