Hi, recentely my lcd ccfl were gone, so i replaced them with an led strip, with some success.
Because i need more light from that lcd, now i'm building an 50-led array boost ballast (180V OCV, 20mA limited current).
Because i'm frightened about load disconnection (bad solder, bad wire, murphy's law, etc...), do you think i can use two neon glow lamp in series to protect output from going over 180V?
I know there are varistors, transil, etc, but i need some clear fault indicators.
I know 20mA on neon lamp will decrease indicator's life, but they will work only 10 minutes on ballast's life (9 minutes for testing purpose).

the ballast is the same (with different mosfet and resistors values) of which i posted in gallery some years ago.

May you re-post a link?
The 180V 10mA is too high power to be just dissipated, even for 10 minutes, so better to use some converter shut down, most controller IC's provide some means for that and even when they don't, it is not as difficult to make one...
But to help you there I will need to know what ballast design to start from...

hi medved!
the schematic is on your pm (where you suggested me some useful upgrade).

now i have solved with two feedback: one is current limiter, and another is voltage limiter (via resistor divider)

hi medved!
the schematic is on your pm (where you suggested me some useful upgrade).

now i have solved with two feedback: one is current limiter, and another is voltage limiter (via resistor divider)

That is exactrlythe style of protection I had in mind.
I could not find it back anymore (But I did recall some discussions), but you figured it out, so hope it will work well...

Hi, the schematic is this:
http://www.lighting-gallery.net/gallery/displayimage.php?album=2416&pos=1&pid=65801

i'll add an overvoltage protection via an trimmer and an resistor.

I meant just that... :-)