UV led hot AND life problem?

[nick703]

Hello friends i have a UV led and and i want to create Led Driver for this UV Led. My UV LED is Edixeon S series UV LED

below is the data sheet **broken link removed**

Now i am using LM317 for LED driver with 12V Supply

Forward Volatge of LED = 3.2 to 5.0
Forward Current of LED = 350 to 700mA

And Resistor i have use 10ohm below is circuit diagram
**broken link removed**


Now problem is this UV led is very hot after turn on 1 min. and also this UV Led is dim after 20 to 25 day.

is that any solution to this problem how can i make led longer life and heat reduce?

 

[jiripolivka]

Your 5V x .7 A is 3.5 W, so you must use a heat sink to cool down the LED. Any semiconductor or resistor can be "killed" by overheating, so please take care of the heat properly.

 

[nick703]

Thanks for your reply,

yes i have also check with changing resistor value but that time i have not getting much brightness but heat problem is solve.
And another question is that any affect if i use constant current source using lm317 IC ?

 

[jiripolivka]

The LM317 T can be used as a constant-current source. In the LED specifications I can see two pages describing the current limit for various heat resistance values. Use a large heat sink for the power dissipation. Junction temperature of 120 deg.C is easy to exceed, long life requires the recommended 80 deg.C max value. Use a small fan if possible. Lowering the temperature causes no harm, contrary to overheating.
LOok in professional LED designs for how to do it. LED lamps sold to replace light bulbs still suffer by overheating in narrow mounting spaces.

 

[marce]

Get a proper LED driver...

 

[Audioguru]

The LED manufacturer probably has an Applications Note that shows how to cool that tiny little package so that the heat does not kill the LED.
Since your LED is now always dim then the heat has damaged it.

 

[nick703]

Get a proper LED driver...

thanks for reply but which type of LED driver can you suggest me i want to make this LED Driver.

 

[Audioguru]

Why do you need a LED driver? If the supply voltage does not change then you can limit the current with a simple series resistor. If the supply voltage changes then the LM317 current source is fine.
How will you cool your tiny LED?