Go Down

Topic: high power led driver (Read 8330 times) previous topic - next topic

Hippynerd

Its kinda relative, 350ma, is a little more than 1/3 amp, which is a lot for a microcontroller, but insignificant if you are talking about a car alternator, and a lot more insignificant than the smallest circuit breaker in your home.


Clearly the microcontroller wont be enough to run one LED, so you will need  power supply for the LEDs, but you may also need to consider heat, those LEDs will probably produce some heat that you may need to consider depending on how you are using them.
https://sites.google.com/site/rgbledcubes

focalist

#16
Dec 11, 2012, 07:58 pm Last Edit: Dec 11, 2012, 08:02 pm by focalist Reason: 1
You'd be surprised how little heat they generate- but they should be at least on one of those aluminum "star" heatsinks, running the raw LED "bead" without a heatsink for more than a few seconds will in fact cook the little beast.  On the plus side, one watt white LED's are less than a quarter each ordered from China.

I have had good luck using aluminum angle bracket and channel from the local Home Depot for heat sinking, and a tube of white lithium grease for compound.  

I have a homebrew LED photo strobe with over 140 watts of LED's on it now- I use a "repurposed" aluminum cable modem casing (about two pounds of thick aluminum) as the heat sink of the gods on that one.

On the subject of Power Supply- simple.  ATX computer power supply, ground the "power good" line and you have a high-capacity 12v and 5v supply... fan cooled, and cheap.. free, if you cannibalize an old PC... Use a fuse though, PC power supplies can kick out quite a bit of current!
When the testing is complete there will be... cake.

Headroom

Judging by the type of LED that you have linked to in your first post, which is a RGB LED you are not dealing with 5 LEDs but with 3x5 = 15!

If, on the other hand, you want to control the brightness of these 5 LEDs independently then things get more complicated.

There are quite a few chips available that can control 3 channels at a time but finding one that actually has a good dimming ratio at high current is not that trivial. But, it depends on what you actually want to achieve.

Te LT3496 can control 3 channels with up to 750mA each at a dimming ratio of 1:3000. I have not been able to find anything comparable. But then, that certainly will not result in a low cost solution, as that chip alone is around $7.

http://trippylighting.com

http://ledshield.wordpress.com/

AlexKite

Hi guys,
I've read LT3496' datasheet and surprisingly see that it needs a lots of additional MOSFEts to work, according to it (see attachment).
Please advise the simplest way for dimming 3W RGB LED, I'm a newbie and my experience with ICs and soldering is very poor ))
I need 3-channel independent and smart dimming.

LED SPECIFICATIONS:
Model Name: CREE XML RGBW
Emitted Color : RGBW/RGB White
Product Voltage: Red 2.25~2.6V, Green 3.3~3.9V, Blue 3.1~3.7V, White 3.1~3.7V
Maximum Drive Current: 1A
Maximum Power: 12W
Max Luminous Flux: Red 87.4LM, Green 114LM, Blue 39.8LM, White 100LM
Viewing Angle: 130 Degree
PCB Diameter: 20mm

Thank you in advance!

MarkT

Talking about high power, the '100W' LED arrays take about 3A at 22 to 33V (depending on colour). 
The green/blue/white ones are close enough to be feasible to run from a 36V supply with some
series resistance of constant-current driver - a power resistor is a cheap and simple solution
when the voltage is a close match as you already need a heatsink for the array.  The advanced
MOSFET boost/buck constant current drivers are significantly more efficient, and control the current
better, but not so cheap to source.

When you have enough LED power you have to worry about cooling - 12V quiet cooling fans are
easy to source, so a 12V in constant-current DC-DC converter makes sense for powering LEDs
(a lot of LED strips are 12V anyway)

PWM is an easy way to dim LEDs but there are issues - not all constant-current drivers are suitable
to PWM at high enough frequencies to be flicker-free, and if you are using a lot of power you can
easily end up generating significants amounts of EMI if you don't take care.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Paul__B

The green/blue/white ones are close enough to be feasible to run from a 36V supply with some series resistance of constant-current driver - a power resistor is a cheap and simple solution when the voltage is a close match as you already need a heatsink for the array.
I fancy Mike is going to crucify you for that suggestion!

AlexKite

I need to handle only one(!!!) 3W RGB LED, and I'm looking for dimming solution with minimal soldering.
I didn't like to use power resistor anyway.
The price difference of $10-20 won't kill me, and the solution must be simple enough to assemle it on the breadboard.

Headroom

This constant current driver is very cheap and has functioned very nicely in previous prototypes.
http://trippylighting.com

http://ledshield.wordpress.com/

AlexKite

Hi Headroom,

Thank you for your advise!
Really good solution for me, already contacted the above shop.

AlexKite

And is it possible to use tlc5940 for controlling the above CREE XML RGBW LED?
How can I set exact voltage for each channel? (>> Product Voltage: Red 2.25~2.6V, Green 3.3~3.9V, Blue 3.1~3.7V, White 3.1~3.7V)

Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy