OSRAM OPTOTRONIC Constant current LED power supplies with 3DIM - Manual (Page 31)

31
LEDset APPLICATIONS
Figure 23: TC620 solution – output characteristic. Figure 24: TC620 solution – R
TRIP
vs. temperature.
Example:
Conditions:
Tset
H
= 80 °C Iout
H
= 0 % Inom
max
Tset
L
= 70 °C Iout
L
= 70 % Inom
max
With the TC620 datasheet, it is possible to calculate the
resistance value for the temperature trip points:
Therefore:
R
HS
= 161.5 kΩ
R
HS
= 162 kΩ (E96 1% series) Tset
H
= 80.6 °C
R
LS
= 151.9 kΩ
R
LS
= 150 kΩ (E96 1% series) Tset
L
= 68.8 °C
Regarding Rset resistor:
Rset
1
= 47 kΩ 1 % (100 % of Inom
max
– see chapter 3.1.1.)
In order to achieve the 70 % of Inom
max
, the equivalent paral-
lel resistance Rset
EQ
(Rset
1
||Rset
2
) to be chosen must be
about 26.7 kΩ (see table 4 in chapter 3.1.1.).
Recalculating, the real Iout = 70.2 % of Inom
max
.
(see fi gure 24)
Rset
2
= 61.9 kΩ
(E96 1 % series)
Rset
EQ
26.7 kΩ
Rset
1
Rset
2
Rset
1
+ Rset
2
Rset
2
61.8 kΩ
Rset
1
Rset
EQ
Rset
1
Rset
EQ
R
TRIP
0.5997 T 2.1312