2.4A constant current source for LED string

Calum Mackinnon

Hi,

I have a DC input of between 20-24V but not constant current. I am driving a string of 6 LED's, each requiring 3.3V so 19.8V. I neeed a constant current source of 2.5A.

I need someithing that will take the 20-24V in and give me a 20V out constant current of 2.5A. I may be able to tweak the input voltage to be a little higher but 20v is the crrent spec.

Any possible solutions?

Cheers

Calum

over 14 years ago

0 Mike Kosteva over 14 years ago

TI__Intellectual 2590 points

Hi Calum,

I have a few questions concerning your application:

1. Is this application isolated or non-isolated?

2. Can you arrange the LED's to be 2 sets of 3 LED's in series which would yield approximately 10 VDC at 5 amps across the string?

3. Is there any dimming required for your application?

There are several approaches I can discuss based on your answer to the above.

Thanks,

Mike Kosteva

0 Calum Mackinnon over 14 years ago in reply to Mike Kosteva

Genius 4155 points

Hi Mike,

This is for a customer of nmone.

Looks like it is isolated. You can see the power supply they are using here http://www.xppower.com/orderPriceList2.php?seriesid=100527&groupid=100025&catuid=1&lang=EN

I can ask about the rearranging the strings.

Dimming is required - they are planning on using a using a resistive pot to control a PWM input to the LED driver.

The other option may be to replace the AC/DC convertor with a TI module - is that possible? They would need two outputs:-

1. 20V constant 2.5A fro LED string - with dimming

2. 12V 0.5A for a fan

Cheers

Calum

0 Mike Kosteva over 14 years ago in reply to Calum Mackinnon

TI__Intellectual 2590 points

Calum,

Also there's the option of going from 115 to a 20VDC 2.4 amp LED driver reducing it to 1 stage instead of a 2 stage approach.

Mikr

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2.4A constant current source for LED string