Heating problem with 3W white LED

[jayanthyk192]

Hi,

i just bought a 3W white led(max current <700mA).i have 5V regulator which supplies a max. 440mA of current.i connected the led to it and the led lit,but it started heating up,even with the sink(aluminum plate).i couldnt hold it for long and the temperature kept rising.earlier i burnt another of 1 watt.so i need to know if the temp.can rise that much.

 

[Prototyp_V1.0]

Does the led have a internal resistor?

If not, I suggest you reconfigure your voltage regulator into a constant current source.

 

[jayanthyk192]

Does the led have a internal resistor?

If not, I suggest you reconfigure your voltage regulator into a constant current source.

no it does'nt have any resistors.it looks like the attachment.and if i increase the current over 200mA,the led becomes really hot.will the led withstand the temperatures it might reach?

 

[emontllo]

LEDs get very hot if not properly heatsinked.
The electric energy is converted basically into light energy and heat which should be dissipated. Conventional light bulbs are less efficient but dissipate most of its energy as radiated energy (infrared light) and therefere heatsinking is not necessary. Maybe you need a heatsink with lower thermal resistance. Check if the thermal contact between LED and aluminum plate is correct (you can use thermally conductive paste, adhesives or films). Improving the heat dissipation will also increase LED efficiency (the lower the temperature, the higher the lumen/W!)
In additon LEDs should be powered with constant current sources rather than constant voltage power sources. Check the LED manufacturer datasheet, 1 W leds have a maximum of 350 mA (typical) constant current, you may have burnt the chip with 440 mA current.

Ernest

---------- Post added at 17:08 ---------- Previous post was at 17:06 ----------

The LED package you are using DOES need extra heatsink, increasing contact pressure between LED and heatsink will improve heat dissipation too.

 

[jayanthyk192]

LEDs get very hot if not properly heatsinked.
The electric energy is converted basically into light energy and heat which should be dissipated. Conventional light bulbs are less efficient but dissipate most of its energy as radiated energy (infrared light) and therefere heatsinking is not necessary. Maybe you need a heatsink with lower thermal resistance. Check if the thermal contact between LED and aluminum plate is correct (you can use thermally conductive paste, adhesives or films). Improving the heat dissipation will also increase LED efficiency (the lower the temperature, the higher the lumen/W!)
In additon LEDs should be powered with constant current sources rather than constant voltage power sources. Check the LED manufacturer datasheet, 1 W leds have a maximum of 350 mA (typical) constant current, you may have burnt the chip with 440 mA current.

Ernest

so you suggest the problem is only with the sink.if i use a larger sink the led should remain cool and not burn out.

---------- Post added at 17:16 ---------- Previous post was at 17:11 ----------

i added a desktop heatsink+thermal paste,now it works really good.thank you.

 

[alexan_e]

This is a led mounted on a thin star heatsink, it gets hot very fast even when it operated with the rated current, you have to mount it in a heatsink, note that it will still get hot but not so much and not to temperatures that will limit the led lifespan or even destroy it..
In any case you have to use some king of constant current driver to drive it properly with the rated current (or lower)

Alex

 

[emontllo]

You are welcome.
Appropriate heat sink and constant current sources are the key!

 

[jayanthyk192]

yes, i added a computer heat sink and now it works fine

 

[chuckey]

You "burn" yourself at a temperature > 55 deg C!, not too much for a semiconductor?
Frank