Controllable LED Driver Design

Thread Starter

arman74

Joined Jul 1, 2017
43
Hey guys.
I need to control about 50 Cree LEDs lights with my microcontroller. As you know for better results we control the current of the LEDs instead of their voltage.
So I would be thankful if you introduce me any ICs generated for this or any schematic diagram or any help.
Thanks.
 

danadak

Joined Mar 10, 2018
4,057
Are these all in a series string, series/parallel, parallel (all individual) ?

Fixed current or variable ? Range of current ?


Regards, Dana.
 

Thread Starter

arman74

Joined Jul 1, 2017
43
Are these all in a series string, series/parallel, parallel (all individual) ?

Fixed current or variable ? Range of current ?


Regards, Dana.
I use different LED colors and for each color I need to have control.Every same LED colors are in series.
As I said the current varies between 0 to 350 mA.
 

Dodgydave

Joined Jun 22, 2012
10,050
If they're all in series, then the psu Voltage is going to be very high, how are you going to wire them, 5 rows of 10 in series??

This can be done with ready made modules or you can do it with a regulator and Mosfets.

Can you post the Cree led details please.
 

Dodgydave

Joined Jun 22, 2012
10,050
Each led takes 3V drop, 10 leds in series is 30V, so your psu needs to be approx 35V or higher, @1amp min Constant Current control,.

Do you want to get ready made current modules or are you going to make your own circuits using Mosfets and Linear regulators?
 

Dodgydave

Joined Jun 22, 2012
10,050
You can use the LM338 5Amp regulator it will will run on 40V,so you can put 10 leds in series and control the current, it will need an Heatsink, if you use the module they need a Pwm signal as well..
 

MisterBill2

Joined Jan 23, 2018
9,274
You can use Pulse Width Modulation and suitable power FET devices and a single current sense resistor for each of the series strings, and then you are not going to need to design any analog control circuits. Just set the voltage for each string at a level that gives about 90% of max output at 100% on time. Then you can do it all in software.Just use a high enough PWM frequency to avoid visible flicker. AND heat-sink those series switch transistors. Probably the cheapest, easiest, most compact way of doing it.
 

danadak

Joined Mar 10, 2018
4,057
Actually because Vled highly T sensitive you want to drive with current.
And fact from one LED to another significant variance of Vthreshold.
Driving with current also helps in uniform brightness LED to LED. Not a
guarantee but helps. So a PWM driven current regulator is desired approach.

Plus PWM driver chips typically have well controlled MOSFET internal driver
interface.


Regards, Dana.
 

MisterBill2

Joined Jan 23, 2018
9,274
Actually because Vled highly T sensitive you want to drive with current.
And fact from one LED to another significant variance of Vthreshold.
Driving with current also helps in uniform brightness LED to LED. Not a
guarantee but helps. So a PWM driven current regulator is desired approach.

Plus PWM driver chips typically have well controlled MOSFET internal driver
interface.


Regards, Dana.
I neglected to mention the "single current sense resistor"should be connected to an analog input so that the current could be set. And setting the high current limit with a resistor may be a bit less efficient but it is very simple and quite reliable. And also it is cheap and easy.
 
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