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100
80
60
40
20
0
65
75
ThermalGuard
100
75
50
0
-40
-20
0
Design-in Guide - Philips Xitanium LED Xtreme SR driver
86
92
96
Tcase (°C)
80 86
20
40
60
Tcase (°C)
Shown on the left is an example graph of the ThermalGuard feature.
In this example, the output current is reduced from t
temperature = 86°C onwards down to 10% at 92°C. Between 92°C
and 96°C the output current will remain at 10%. If the output
current reduction is sufficient to decrease the t
then the output current will be increased accordingly up to the pre-
set 100% level.
If the output current reduction is not sufficient to offset the t
temperature increase then the output current is eventually reduced
to zero at 96°C and the driver output will be switched off. Normal
operation will not resume until the t
down to 92°C. A power cycle is not required to resume driver
operation. The 4°C hysteresis will prevent the luminaire from
blinking on and off as a measure to prevent nuisance.
Driver Temperature Limit (DTL)
Depending on commercial or application needs it may be required
to improve driver lifetime. This can be achieved by safeguarding
that the maximum driver case point temperature in the application
is not exceeding a predefined limit set below t
configurable DTL feature enables this by offering an adjustable
t
point temperature threshold at which the output current is
c
reduced and switched off. DTL configuration can be done by
MultiOne software.
Shown on the left are a DTL and driver lifetime example graph. The
green line represents the output current as function of the t
temperature with DTL activated through a custom profile based on
the requirement that the driver lifetime be at least 75khrs. The red
line represent (non-configurable) ThermalGuard behavior. In
this example, the output current is reduced from t
temperature of 80°C onwards and the t
whereas it would have been allowed to reach up to 96°C without
DTL enabled as defined by the ThermalGuard feature.
The DTL feature can also be applied as a substitute for Module
Temperature Protection (MTP) in order to protect the LED module
against overheating and to maintain a certain lumen maintenance.
The advantage of using DTL for this purpose is that the additional
NTC on the LED module plus required wiring can be omitted.
However, DTL can only be used as such if the thermal relation
between the driver t
100
defined. Therefore a meticulous thermal investigation of the driver -
LED module driver application is required to prevent DTL from
being activated at a too low or too high LED module temperature!
Warning: the DTL t
output current should be reduced must not be set too
low. Otherwise, undesired light output reduction may result
during normal
operating conditions.
investigation of
ensure that
the configured DTL threshold occurs neither at
too low nor at too high driver operating temperature conditions.
c
point temperature has cooled
c
point will not exceed 86°C
c
point and LED module temperature is well-
c
point threshold temperature at which the
c
A
meticulous
the
driver application
point
c
point temperature
point
c
(max). The
c
point
c
point
c
thermal
is
required
to
13
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