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.
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