Need help with power supply design!

[Scubasteve]

Hey everyone,

I need a 3.7-3.8Vdc power supply to be able to adjust from 1A to 4A, which will be varying the brightness of an array of 188 LEDs. I will not use a switching supply, because they have an initial pulse of current at startup which would ruin the array.

What I am looking for is perhaps a circuit which I can control with a 0-5V signal from a DAC. Perhaps I can use a pulse-width modulation, but I need to be sure it will work before I try it out. These LEDs are worth over 200$!

Steve

 

[stevez]

Steve - not sure I understand the requirements exactly - but will offer an idea. I've used LM723 regulator with pass transistors. This IC has current limiting built in - load current passes thru very low ohm resistor and the voltage drop is read across two pins of the IC. You have to manaully adjust the current limit.

The 723 has been around a while. All I can offer you is that I think you'd be able to bias or adjust the voltage remotely with 0 to 5 volts but I am not certain. 723 application sheets have circuits. If you can't find I'll copy from my handbooks and mail to you. The cost of the 723 is like $1 so experimenting isn't costly.

I have seen regulators that are "programmable" and I interpret what I read about them to believe that they can be adjusted remotely - just no experience with them at all.

 

[Sebi]

You can build additional current limiter for any SMPS. I've made this few years ago for accu charger.

 

[Scubasteve]

Wow guys , great help!
You're gonna kill me, but I have decided to do a little PWM with the maximum current that I want flowing.
Thanks for your help though, it is always appreciated!

Steve