I'm working on a circuit to drive a 3W RGB LED that uses the LM317T in the constant current configuration. From what I've read, the LM317 provides constant current, even with varying input voltages (within limits).
Now for my question: given that LEDs have a varying forward voltage drop, depending on various conditions, such as temperature, does the LM317 account for this (i.e. will it be able to maintain 350mA while the forward voltage drop of the LED increases)? If the answer is no, then I'm not sure if it still makes sense for me to use the LM317 verses a simple resistor to limit current through the LED since my input power supply is regulated. It seems that intended purpose of this circuit is to provide a constant current when you have a varying voltage power supply, such as a battery.
Here's the spec: http://www.st.com/stonline/products/literature/ds/2154/lm217.pdf
and here's the circuit http://www.instructables.com/id/Super-simple-high-power-LED-driver/
Now for my question: given that LEDs have a varying forward voltage drop, depending on various conditions, such as temperature, does the LM317 account for this (i.e. will it be able to maintain 350mA while the forward voltage drop of the LED increases)? If the answer is no, then I'm not sure if it still makes sense for me to use the LM317 verses a simple resistor to limit current through the LED since my input power supply is regulated. It seems that intended purpose of this circuit is to provide a constant current when you have a varying voltage power supply, such as a battery.
Here's the spec: http://www.st.com/stonline/products/literature/ds/2154/lm217.pdf
and here's the circuit http://www.instructables.com/id/Super-simple-high-power-LED-driver/