voltage regulator help - ot

[mister_e]

There's still another way before jumping to another regulator. The solution is to use a transistor to boost the current. In this case, you can use a TO-92 as regulator and almost any TO-220 in Full-Pack (or isotab someting like that). About the efficiency? fair to bad depending the transistor you'll use. Some have a huge drop between Collector and Emitter when the current rise across.

OR you can even build your own regulator with a simple transistor, zener diode and a resistor. Problem is almost the same as previous

Build one with a PIC or an OP-AMP to monitor the output and apply according correction is a better solution. That's what i did on some occasion.

BUT the ultimate, look at LT1085 but the TAB is often the output so... it solve a problem but not the other. www.linear.com

About a DIP solution? Yish, i can't recommend any if it exist anyways. I feel they'll mostely burn your PCB before.

In many case, you can place a heatsink on your Regulator and secure it on your PCB. This work really well in many case. This avoid the insulator stuff.

As you want to make it 'water-proof' Less holes, and screw have to be consider... except if you really want to add some scellant.

[Acetronics2]

Hi, Doc

Your question is a bit surprising ...

As Leds are to be driven at constant current ( your Leds are supposed to need a lot ...), the evident solution could be to drive a switching regulator ... current regulating, and just voltage limiting .

And may be no more voltage to adjust, then ...

Alain

[mister_e]

mmmpfff can't agree 100% with you Alain. Desolé

Switching regulator are great... but linear too. No more improvement over the previous ... oh well maybe a bit less of heat... but much expensive... at the end, you never ever save a cent.

Just rethink of your reply.. If you regulate the current... it's still a 3 LED driving plah plah. What will be the result when all 3LEDs have to be Full on to produce a WHITE color? Nothing else than a dimmed white

[Acetronics2]

Hi, Steve

I think we could know better what Doc' wants to do ...

a "simplissime" current regulator can also be achieved with a Red Led as volt ref, two resistors ( one for LED and one for emitter current ) and a transistor.

That makes 3 cases ... if TO 220 ... makes min. 3 watts to be dissipated.

Alain

[docwisdom]

Thanks for the replies.
When I arrive home today I will post a schematic. For now, here is a link to the LEDs I am driving http://www.laminaceramics.com/products/bl4000.aspx. For now I am running 1 RGB, I would like to run up to 8 in parallel, therefore the necessity for powerful regulators and powerful mosfets.
I tried using specialized LED drivers, but they all maxed out at 1amp. Cost me $60 too, I may sell them or return them.

I am a filmmaker by trade and that is the ultimate purpose for these LED's. A low power solution for car kits and mobile rigs.

P.S. My source voltage, ~12-14v will not be constant, I know that. A switching regulator that doesnt vary ouput based on input would be nice. The LT1074 looks interesting, also the LM2676. What do you think?

[docwisdom]

Here is the full schematic, it includes the LED drivers instead of the mosfets.

[Acetronics2]

Hi, Doc


Looking back to your first post ... make me think using LM350 ( T or K ) or LM 338K's ( 5A )instead of the 317's would be a very good solution ... as it exists some insulating silicone pads ( or Mica sheets ...) and insulating spacers to avoid connecting reg.case to your aluminium casing !!!

The " best " solution surely is here !!!

See here i.e. : http://www.selectronic.fr/soussousfa...0&ssfam_ref=30

or here : http://www.selectronic.fr/soussousfa...0&ssfam_ref=20


Alain

[wanhaibin]

I also had the heat problem with such linear regualtor. I was not able to find a good heat sink to remove the heat. The problem was solved after I change to a switch type regualtor (LM2575). Although the connection is more complicated, it brings good relibility to my control board.