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Topic: What will happen if I drive LEDs in parallel from a TLC5947? (Read 1 time) previous topic - next topic

scswift

Given that these LEDs are super bright and 50% current looks like 75% brightness, I'm not too worried if there are small differences in the brightness.  In this instance it doesn't matter if they're super uniform. 

Grumpy_Mike

You are or should be worried if one LED is taking more current than it is rated for. Without a seprate resistor for each LED, worst case, one LED takes twice the design current.

scswift

These LEDs are attached to a constant current driver.  So there's no worries about that happening.

fungus


These LEDs are attached to a constant current driver.  So there's no worries about that happening.


He's got you there, Mike...

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

dc42

If you are using the TLC5947 to drive a lot of LEDs, then you need to take the power dissipation of the chip into account. For each channel, it is the voltage at the output pin (which is the supply voltage less the LED forward voltage) times the output current. Then multiply by the number of channels you are using.

You may find that you need to reduce the voltage at the output pin to keep the power dissipation within limits. One way of doing this is to use series resistors - which gives you the opportunity to use the same series resistors for balancing the current between the LEDs.
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