2. Product & Technical Guidance
2.1.7 Hot Cold Factor
2.1 Optical Properties
14
The term describes the relative drop in light output due to the rise in junction
temperature. Hot/cold factor compares the light output of the LED at 85
℃
and 25
℃
junction temperatures, which are located in the LED datasheet.
In the LED datasheets, the LEDs are measured with a single pulse, which means
that the ambient temperature is practically identical to the junction temperature,
since there is not enough time for the LED die temperature to rise in a significant
manner with a single pulse.
The LG Innotek COB LEDs have a hot/cold factor of around 0.90. That means the
LED will lose only 10% of its nominal performance when the LED is operated at an
ambient temperature of 85
℃
.
4W I
F
=400mA
Case Temperature [
℃
]
10W I
F
=260mA
13W I
F
=340mA
90%
94%
89%
93%
88%
94%
Case Temp. vs. Luminous Flux
Case Temperature [
℃
]
0.70
0.80
0.90
1.00
1.10
25
35
45
55
65
75
85
95
Rela
tiv
e
L
u
min
o
u
s Flu
x
[%
]
Case
Temperature
[
℃
]
7W I
F
= 195mA
90%
95%
