I’m designing SLA 3D printer and I need to design UV LED array for LCD screen backlight. Preliminary design is 5x3 (5 parallel strings with three LEDs in each). All LEDs will be soldered on PCB.

The catch is that every LED will have 1W and my inner engineer cries out for active regulation, even though I understand, that passive regulation (via resistors) would be much simpler. I’m just high school student with very little knowledge about electronics, so could you point me to some solutions?

I’m going to solder the PCB myself and I’m not working on the project full-time, so I would definitely prefer something simpler (maybe regulation via MOSFETs?). I don’t need complicated dimming of individual LEDs via IC in BGA package or something like that.

LED parameters: voltage: 3.2-3.6V current: 300-350 mA further info: https://www.aliexpress.com/item/1W-...GB-High-Power-LED-Chip-Light/32804097246.html

I’m sorry for any grammar mistakes, I’m not a native speaker.

 

To get uniform brightness, assuming the LEDs themselves are relatively
matched, you should drive each string with a current source. Thats easy
to do with a 3 terminal adjustable regulator, all you need is a Rsense for
the 3 term reg. An example -

You have to do the worst case thermal calculations to establish
size of a heat sink.

http://rohmfs.rohm.com/en/products/...regulator/three_terminal_heatsink_appli-e.pdf

http://www.ti.com/lit/an/slva118a/slva118a.pdf


Regards, Dana.

 

Thanks for your reply .
Could LM334 circuit be used without heatsink? I'm talking about this design (fig. 3):
http://www.bristolwatch.com/ccs/

Best regards,
Adam

 

Short answer is no to LM334, its only good for 10 mA. And its
package very limited to getting heat out.

TO220 package more appropriate, you have to calc worst case
Pdiss and then do the thermal design.

http://www.ti.com/lit/an/snva419c/snva419c.pdf

Tools - http://www.ti.com/adc/docs/midlevel.tsp?contentId=105986

Regards, Dana.