Looking at the data sheets i see a 90V max. Is this AC or DC?
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Part number?
I'm taking a total Google shot in the dark here, but if you mean something like this, it's probably DC, since based on the schematic it looks like the max is simply derived from the number of LEDs being wired in series.
http://www.ngineering.com/CL2.pdf
-Dave
Yes the CL2...and thanks
In regards to the CL2-n3, it is DC,in fact it needs filtered DC to operate. It will take 90 volts but is rated at about a half watt. The chip drops voltage like a resistor and heats up. So you could not drive a single LED from 90 volts since the chip would generate over 4 watts of heat.
Dale H
I have and still use gunrunnerjohn's led driver circuit based on the CL2 constant current approach. It's small when assembled. I like it. if you want the schematic, I'll send it to you.
Originally Posted by Dale H:
In regards to the CL2-n3, it is DC,in fact it needs filtered DC to operate. It will take 90 volts but is rated at about a half watt. The chip drops voltage like a resistor and heats up. So you could not drive a single LED from 90 volts since the chip would generate over 4 watts of heat.
Dale H
You read my mind..Thank you Dale..that was my next question.
For the low current LEDs that most use for model train work figure about 3 volts to drive a single LED, so if you wired 6 in series you would need at least 18 volts out to drive the whole string. In this example you would try and keep the input voltage into the regulator to about 20-22 volts to minimize the power dissipation of the device.
The readily available LED strings use an array of series and parallel circuits to keep the drive voltage lower. Drive voltage required is determined by the number of LEDs in a series group, usually three in many of the LED strips. Every series strip however increases the current requirement.
Pete
With 90V in, the device can deliver 20 ma to a load of 4500 ohms to
a short circuit. It will drive up to 30 white LEDs in series. The
maximum power dissipation is 2 watts so with only one LED
connected or a short circuit load, the maximum power dissipation
will be 1.8 watts.
Without a significant heatsink, the CL2 can't dissipate 2 watts without cooking in short order. I use the LM317T in a constant current mode for larger loads.
