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1 Simple question about led drivers


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Hi all, and thanks in advance to anyone that takes the time to read and respond. I have been searching for an rgb led controller  and it appears that i have found an ideal one, but  i have one simple but stupid question before i buy the product. The datasheet for the rgb controller does not state if the  current and voltage outputs are constant or regulated. Iam i to assume that they are regulated or not. Finally How can I tell if they are or not.

site for the product

http://www.led-tech.de/en/LED-Controlling/LED-Controlling/MultiLine-RGB-Fader-V2.0-LT-1000_118_31.html

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  • 2 weeks later...

From what I understand, the controller is a PWM one (Pulse With Modulation).  I don't thing there is a voltage or current regulation.
It should just give a constant peak voltage output but a variable duration (PWM) so as to have a variation in the brightness of the led.
According to Specs:

the technical data:

- Speeds: 9
- Channels: 3
- Status LEDs: 12
- 16.000.000 colors
- Reverse polarity protection
- PWM: 150Hz (no flickering!)
- Input: 7-30V DC
- Output: Depending on the input
- Uses common anode (plus)
- Dimensions (LxWxH): 110x111x25mm

- Max. capacitance per channel: 10A
- Max. LED forward voltage: 35V DC
- Max. total capacitance of illuminants: 20A over soldering pads or 16A over clamps


the output voltage depends on the input voltage.  That to me means that it is equal to what you put at the input. 
So we conclude that your LEDs should have a series resistor that would limit the current passing through according to the voltage you supply to the controller.  It also said that it uses a common anode (plus) which I believe it is a kind of open-collector output stage.

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How far you've gone ahead with your LED driver project but to answer your query you only need to regulate the current (use current gen. / reg.) :o and the voltage will be taken care of by the LED itself as long as the supply voltage exceeds the voltage across LED (@/<2v) + min voltage across current regulator required. ::) If you use a micro to drive then use current limiting resistor.

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  • 2 months later...

I'am specializing in LED-Applications, using such RGB-controllers...
In General just make sure:
1. You have the correct Voltage, as LED's are sensitive of overvoltages.
2. Make sure you supply enough current to drive them all especially at the same time.

Use large capacitors and regulate its voltage. If in doubt about the current, you can parallel several LM317...
einstein0

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I'am specializing in LED-Applications, using such RGB-controllers...
In General just make sure:
1. You have the correct Voltage, as LED's are sensitive of overvoltages.

No.
LEDs are driven with current, not voltage. The voltage should be higher than required then the current-limiting resistor or circuit absorbs the extra voltage.

If in doubt about the current, you can parallel several LM317...

No.
Voltage regulators are never paralleled.
The datasheet for the LM317 shows how to add a single inexpensive power transistor to increase the output current.
An LM350 has a 3A output and an LM338 has a 5A output.
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No.
Voltage regulators are never paralleled.
The datasheet for the LM317 shows how to add a single inexpensive power transistor to increase the output current.
An LM350 has a 3A output and an LM338 has a 5A output.

I think he's talking about using the LM317 as a constant current source, in which case several LM317 current sources can be safely connected together than the currents will add together.
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