Post by thread:Electroluminescent panel power controller.

I want to design a low cost Electroluminescent panel drive (Output is 280 VAC @ 450Hz and 6Watts. Input power available is at 12V). I am considering a PIC12C508 with 2 of the I/O pins providing an anti-phase drive (at say 100Khz) to a pair of mosfets. The mosfets are arranged to push-pull a center tapped ferrite transformer with the center tap connected to +12V. The secondary of the transformer will be full wave rectified and smoothed to provide a 280VDC supply. Another output of the 12C508 will drive a transistor switch alternately to the 280V rail and then to 0V rail at the required 450Hz. This 280V square wave will be fed to the panel via a coupling capacitor. My problem is that I don't know where to start with selection / design of the transformer. Can I design it myself or am I likely to find an off the shelf item to do the job? Anyone got any leads on ferrite transformer design? Thanks in advance, Gerry Cox. Dorset U.K.

On Thu, 26 Nov 1998 12:57:52 -0000, you wrote: >I want to design a low cost Electroluminescent panel drive (Output is 280 >VAC @ 450Hz and 6Watts. Input power available is at 12V). I am considering a >PIC12C508 with 2 of the I/O pins providing an anti-phase drive (at say >100Khz) to a pair of mosfets. The mosfets are arranged to push-pull a center >tapped ferrite transformer with the center tap connected to +12V. The >secondary of the transformer will be full wave rectified and smoothed to >provide a 280VDC supply. Another output of the 12C508 will drive a >transistor switch alternately to the 280V rail and then to 0V rail at the >required 450Hz. This 280V square wave will be fed to the panel via a >coupling capacitor. Bear in mind that the panel will probably be a mostly capacitive load, so you may need a fairly large output cap. Alternatively, an h-bridge may be a better solution If low cost is important (rather than efficiency or size) , have you looked at using sine(ish)wave drive into an off-the-shelf mains transformer run backwards? You could probably drive the primary with a cheap audio power amplifier chip. If you go the high-frequency route, a flyback type supply would be simpler than push-pull - maxim, LT etc. have plenty of devices, some of which can drive a transformer easily. This would require only one switching device and HV rectifier. 100KHz is probably a bit high unless you need to keep the size of the transformer down. I can't remember off-hand, but you may also be able to use one of the NS simple switcher devices. A PIC may be slight overkill unless it;s used for other things - a CMOS 4060 would probably do the trick (and runs off 12V)!