Calculating of the heat dissipation of a LED

In summary, the LED will generate more heat than it will consume, so you will need to design the enclosure and cooling for 100% heat generation.
  • #1
NJZFW
2
1
Hello Forum,

I write you with the challenge of calculation the heat dissipation of a LED.

The LED in question is http://www.seoulsemicon.com/en/product/spec/SZ5-M3-W0-00/22
a download of the datasheet is possible.

The LED binning is 290lm (W4, 5000K) at 700mA, the efficacy is 157lm/Watt,electrical

I think I need to convert der chart "relative radiant Power over wavelength [%]" in "spectral radiant Power (W/nm) [%]".
But Iam not sure how!

Thanks in advance!
 
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  • #2
Welcome to PF.
At best, you can expect about 20% quantum efficiency from an LED.
The heat will therefore be greater than 80% of total power input.
You must run the LED cool for high efficiency, and for long life.
That suggests you should design for 100% heat generation.
Vf = 2.85 V. If = 700 mA.
Maximum heat generation is 2.85 * 0.7 = 2.0 watt.
At best, that might be a 20% overestimate.
 
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  • #3
NJZFW said:
I write you with the challenge of calculation the heat dissipation of a LED.

The LED in question is http://www.seoulsemicon.com/en/product/spec/SZ5-M3-W0-00/22
a download of the datasheet is possible.

So using the initial numbers from @Baluncore can you say what type if heat sink and enclosure you have in mind for this? Will there be multiple of those LEDs in the same fixture on the same heat sink?
 
  • #4
Hi you two and thanks for the replies.

The cooling is already set, my task is to calculate if there will be overheating.
Roughly 400 of those LED's are used in a big floodlight.

What I need is basically the luminous efficacy of the LED (luminous flow/radiant flow). At this point I am quite sure the provided data in the datasheet is not enough to calculate that number.

My rough estimate of those LED is a luminous efficacy of 300lm/W which results in a energetic efficacy of roughly 40%. So about 60% of the total elctric power, dissipates a heat. Therefore it would be not expedient to use the assumption of 100%.

Once I figure it out I will write you share my information-
 
  • #6
NJZFW said:
The cooling is already set, my task is to calculate if there will be overheating.
That sounds kind of backwards, no? Who "designed" the enclosure and cooling without knowing the power dissipation requirements?
 

1. How do you calculate the heat dissipation of a LED?

The heat dissipation of a LED can be calculated by multiplying the LED's power consumption by its thermal resistance. The formula is: Heat Dissipation = Power Consumption x Thermal Resistance.

2. What is thermal resistance and how does it affect heat dissipation?

Thermal resistance is a measure of how easily heat can flow through a material. It is usually measured in degrees Celsius per watt (°C/W). A lower thermal resistance means that heat can flow more easily through the material, resulting in better heat dissipation.

3. How does the design of the LED affect its heat dissipation?

The design of the LED can greatly impact its heat dissipation. Factors such as the size and shape of the LED, the materials used, and the placement of heat sinks can all affect how efficiently heat is dissipated from the LED.

4. What are some common methods for improving the heat dissipation of a LED?

Some common methods for improving the heat dissipation of a LED include using heat sinks, increasing the surface area of the LED, and using materials with high thermal conductivity. Proper ventilation and thermal management systems can also help to dissipate heat effectively.

5. How does the operating temperature of a LED affect its heat dissipation?

The operating temperature of a LED is closely related to its heat dissipation. If the LED is operating at a higher temperature, it will have a higher thermal resistance and therefore, a lower heat dissipation. It is important to keep the operating temperature of a LED within its recommended range to ensure optimal heat dissipation.

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