Author Topic: Multiple LED's, 5V source, EMC compliance  (Read 469 times)

0 Members and 1 Guest are viewing this topic.

Offline JesterTopic starter

  • Frequent Contributor
  • **
  • Posts: 898
  • Country: ca
Multiple LED's, 5V source, EMC compliance
« on: May 10, 2020, 11:22:10 pm »
I need to design a simple white LED circuit with 9 LED's in an array all on at the same time, not sure on total power but somewhere between 2-5W total. 

Walwart 5Vdc power supply, perhaps something like this: https://www.digikey.ca/en/products/detail/cui-inc/SWI5-5-N-MUB/6579911

The circuit will need to pass EMC compliance test first time, so I prefer to avoid switch mode current regulators.

I'm considering using a voltage regulator configured as a current regulator, and simply parallel all the LED's and hope that the variation in brightness LED to LED is not overly noticeable.

Has anyone tried this?

 

« Last Edit: May 11, 2020, 01:12:20 am by Jester »
 

Online mawyatt

  • Super Contributor
  • ***
  • Posts: 4119
  • Country: us
Re: Multiple LED's, 5V source, EMC compliance
« Reply #1 on: May 11, 2020, 12:25:28 am »
From what you've indicated these 9 LEDs will draw about 1 amp total, so each LED will require ~111ma. From my limited experience with LEDs (more on the higher power area than lower power) you can't depend on them current sharing when paralleled. You can use separate ballast resistors for each LED, or better yet design a current source with 9 equal outputs. For this current source I would use PNP rather than PMOS output devices, since discrete bipolar transistors match better, and use a modest emitter degeneration, maybe 3~5 ohms.

Best,
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 

Offline dragondude

  • Newbie
  • Posts: 6
  • Country: au
Re: Multiple LED's, 5V source, EMC compliance
« Reply #2 on: May 11, 2020, 12:42:06 am »
You could use a DS2003 darlington driver or 2 with load resistors to limit the current to about 30 to 60 mA per LED. You need the specs for the LEDS before jumping in. What you are trying to do has been done 000,s of times before so simple circuits will be on the web somewhere. Also I am not sure of the quality of Walmart products but if you want EMC compliance I would buy a quality power supply.
« Last Edit: May 11, 2020, 12:44:13 am by dragondude »
Engineers design things......Technicians make them work.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf