Printer power supply for 20W SMD LED chip?

Thread Starter

Davoinn

Joined Jul 10, 2016
11
I got this printer power supply with 2 out puts, 32v @750mA and 16v @200mA. Can I use it to power a 20w smd led rated 30-32V @560-600mA and a 100 ohm 1/4w resistor on the 16v for cooling fan 12v @150mA or if i need a head sink and a cooling fan for the led?
 

Marley

Joined Apr 4, 2016
369
The LED will need to be current controlled. The LED voltage is only approximate. Normally this is done with a special switch-mode controller that regulates the current.

The current could be controlled with a series resistor but to get accurate control the power supply voltage needs to be 10-20% higher than the expected LED voltage and there will be quite a lot of power lost in the resistor.

So I don't think your power supply is any good for this.
 

Dodgydave

Joined Jun 22, 2012
9,651
Don't see why not, you need a constant current source for the led,like a lm338 or your using a series resistor.
 
Last edited:

Alec_t

Joined Sep 17, 2013
11,739
Suman,
Click the 'Forums' tab near the top of the page,
Click on the appropriate forum title,
Click the 'Post new thread' button near the top right of the page.
 

ci139

Joined Jul 11, 2016
1,696
16v @200mA , 100 ohm 1/4w resistor , fan 12v @150mA
the fan at startup can draw some 3 times the nominal power - which may develope the supply fault over a longer period of time ? half a year or more - which also may not dev. that fault if the supply design is such - the momentary 70% overload falls into standard 2x nominal short circuit curent range - the bad thing here is when switched power supply starts and also the fan starts - so if your fan starts normally - no problem - if if not - time the fan start by some 3 to 10 seconds - if it still gets slow into speed - it's no good

((( despite the fan starting normally the near spec continuous or longer duration loading may heat up the supply itself - the hotter the semiconductor the shorter it's aging . . . )))
 
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