Electronic ballasts - how do they work?

[ywh]

I need a biger pic so I can look for it.
can you take pic ?

[Eva]

DIY electronic ballast for four 15W fluorescent lamps, just in case someone is interested... (I know, the lamps used in projectors are somewhat harder to drive)

Electronic ballast that drives four 15W fluorescent lamps (ideal for PCB UV exposure)

[ywh]

Hi !
is this ballast your need?

[ywh]

mark

[crazifunguy]

Can the wattage be changed in these electronic ballasts? I have a AC ballast (Spark Gap Ignition)? It is electronic. The wattage is 250. Can it be changed to 150 or less with some component changes or a pot in place of a sense resistor?

[crazifunguy]

No electronic wizzes able to input on this??

[mbates14]

old old and dead thread... sorry. As far as wattage goes, it really doesnt matter if you have a schematic you can adjust the resistor dividers in the run and ignition feedback circuits. inside an electronic ballast is a feedback comparator that is used to read the amount of current drawn from the lamp at all times. 250 watt lamps have specific current and voltage ratings and the ballast is designed around that...

Using a 150watt lamp, these change. ignition voltage could be the same, but the run current is definately not the same. simple ohms law would state that if you go from 250 watts down to 150watts, your loosing 100watts of power. So therefore, at 65V run voltage, at 250 watts, your pulling 3.85amps of current through the ballast, that circuit monitors this to confirm the bulb is lit continuously. youll drop to 2.31 amps for 150 watts, significantly lower. This can cause an issue, becuase it could be below its lamp lit threshold settings in the feedback circuit, so the ballast would think the lamp is dying and WILL shut down. depends on the circuitry.

this is why you must use lamps rated for ballasts.