80 volt, 1500ma, LED light string powered by 117 AC

[kinarfi]

Oh yea, I'm now thinking a 9v wall wart may be the way to provide control power for this project, I have a bunch of them taking up space.

 

[audioguru]

Didn't you look at the datasheets?
The datasheet for the 2N4401 shows its very high speed and very high current gain, probably because its maximum voltage is not very high. But the datasheet for the MPSA42 shows its very slow speed and very low current gain probably because its maximum voltage is very high.

 

[kinarfi]

I have both data sheet side by, ON semi, and what I see,
ft=250Mhz(2n4401) & ft=50Mhz(MPSA42) -- I don't know if that's high or low for this purpose.
Ccb=6.5 pF(2n4401) & Ccb=3.0 pF(MPSA42) -- I looked at this, expected the higher Ccb would be slower. The data sheet for 2N4401 has a lot more information than the data sheet for MPSA42. From what I was taught, I would guess that there are a lot more holes to fill in the pn junctions of the MPSA42 than the 2N4401 and that's why there is a Ic lag, but that's just guessing,
Any one have concrete answer?

 

[audioguru]

250MHz is 5 times faster than 50MHz.
Did you also see the big difference in the current gain? The MPSA42 might be faster if you increase its pulsed base current for its turn on and for its turn off.
For a low voltage circuit, do not use a high voltage transistor.

 

[kinarfi]

Is there a practical way to power a 80 volt, 1500 ma Led string of lights from 117 volts AC ? My thoughts are to use a 24 vac transformer to buck the 117, rectify that and use a current limiting circuit to hole the current at 1450 ma.
Anyone have any suggestions?
Thanks,
Jeff

Got my answer figured out -- each device draws 10 volts and has a rating of 1500 ma, 117 volts full wave rectified and capacitor filtered delivers approximately 165 volts minus diode and wire losses, so 16 devices in series strung across 40 - 60 feet of ceiling replaceing 3 8' two tube fluorescent fixtures gives much superior lighting. Love it!!!!!
Jeff
correction, make that 17 devices in series, current drops from 1.3A to just over 1, head gone down, light output change is not noticable