Consant Current Drivers

[cenote]

Have a question for technical people on here. I was playing with the CL25N3's and ended up blowing up a set of expensive 5-chip 100mA LED's. Wondering what I did wrong and why smoke?

Here is the CC Chip specs: http://www.supertex.com/pdf/datasheets/CL25.pdf

I had 24v on Va
Had (4) CL's wired parallel
Had (3) 3.2v 100mA 5-chip LEds in series after CL
Had a good amp meter inline before CL

When I plugged in, I blew the 200mA safety fuse on meter
Of coarse I had to bypass the fuse (first mistake) and turn hooked it up to the 10amp setting...here is when it went bad....
Plugged in, and pufff went the LED's, cat ran out of room cause of odor

Any suggestion, and don't say wait for the Nudies to come....looking to construct some to withstand some heat.

 

[budude]

Did you mean CL6 (or CL7)? These are the 100mA driver chips while the CL25s are 25mA. I was looking at the CL6 to convert my MightyMini's to constant current but it's a bit pricey to do so (8 required per MM). There are two modes of operation where one supplies 100mA and the other 107.5mA according to the datasheet.

 

[KeithTarpley]

Greetings,,,

Well, since you worked it out in chat, initially with one device, you had that part working. And I'm guessing you set things up per the pdf pic. So, my first thing to check would be for any possible short around the devices...

Keith

 

[AussiePhil]

Chuck

My first thought is that you had one in back the front, the internal diode will provide a nice short circuit. Can't say i have ever done it myself but that's the theory.

Which package are you using?

Phil

 

[cenote]

Chuck

Which package are you using?

Phil

Using the -G which I guess mean threw hole (3) pin, not the SM

 

[cenote]

Greetings,,,

Well, since you worked it out in chat, initially with one device, you had that part working. And I'm guessing you set things up per the pdf pic. So, my first thing to check would be for any possible short around the devices...

Keith

I thought maybe the same, and going to dare set up another test with a few more LED's I have left. ALso, I am going to tame down the Va to about 15v with a 5 amp Volt Reg.

 

[cenote]

Did you mean CL6 (or CL7)? These are the 100mA driver chips while the CL25s are 25mA. I was looking at the CL6 to convert my MightyMini's to constant current but it's a bit pricey to do so (8 required per MM). There are two modes of operation where one supplies 100mA and the other 107.5mA according to the datasheet.

Am thinking the same, but I wanted to jumper the two sets of LED's and power with 24v. rate now, playing with the CL25's. Specs says they are able to Parallel them together to make 100. Wanted to prove the concept, than make one out of the CL7 and see about how to dissipate the heat.

 

[budude]

You can use 3-4 regular diodes in series to mimic an LED until you have things ironed out - it's not exact but 1N400x diodes are only a couple pennies a piece and will easily take a couple hundred mA... once you get the circuit figured out you can pop in your pricey LEDs.

 

[cenote]

Thanks for that idea budude. Pennies always better than dollars....

 

[AussiePhil]

diodes will only drop 0.7v not the 3.0v of a white led, theory is valid you just need a lot more of them.

Personally i would just use a 2c red led and a 1K resistor and let the led be overdriven and the resistor disapate some heat for the purpose of testing.

Some of this is complicated by the devices requiring about 5v of overhead for current regulation.

Phil

 

[budude]

diodes will only drop 0.7v not the 3.0v of a white led, theory is valid you just need a lot more of them.

Personally i would just use a 2c red led and a 1K resistor and let the led be overdriven and the resistor disapate some heat for the purpose of testing.

Some of this is complicated by the devices requiring about 5v of overhead for current regulation.

Phil

Yep - that's why I said to use 3-4 in series which would provide about 2.1 - 2.8V in drop - plus they will easily take most current "mishaps" (at least up to 1A or so). I was under the impression he was looking to get to 100mA as well so this would be viable for this.