Thermal Management in LED design


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Thermal management is a crucial isuue in a solid‐state lighting.
The most effective simple way is to reduce excessive thermal loading is by decreasing the drive current. Although decreasing a drive current will slightly reduce the lumen output, at the same time it can increase the Lumen Per Watt (LPW) and enhance a system efficiency.

For example as Cree’s XLamp® XM-L High Flux Cool White LED, i.e. 300lumex.


Figure 1 Forward voltage vs Forward current (@25⁰C)

Figure 2 Forward current vs Relative luminous flux (@25⁰C)

  • When driving 3A (at 25⁰C), LED luminosity is about 300lm x 325% = 975 lm.
    The required power is about 3A x 3.34V = 10.02W, the efficiency is 97.3lm / W.

  • However, when driving 1.5A (at 25⁰C), LED luminosity is about 300lm x 195% = 585 lm.
    The required power becomes 1.5A * 3.14V = 4.71W, the efficiency is increased to 124.2 lm / W.

Therefore, it can consider to increase the number of LEDs to meet the lumen output, while controlling the drive current to reduce the thermal loading to improve the overall system efficiency.

More Tips about Thermal Issue in LED Design:

  1. How to Fix Thermal Design Issue in the LED Design