K Series Data Sheet
150 Watt DC-DC and AC-DC Converters
Thermal Considerations
If a converter is located in free, quasi-stationary air (convection
cooling) at the indicated maximum ambient temperature
T
A max
(see table:
Temperature specifications)
and is operated at its
nominal input voltage and output power, the temperature
measured at the
Measuring point of case temperature T
C
(see:
Mechanical Data)
will approach the indicated value
T
C max
after
the warm-up phase. However, the relationship between
T
A
and
T
C
depends heavily on the conditions of operation and
integration into a system. The thermal conditions are influenced
by input voltage, output current, airflow and temperature of
surrounding components and surfaces.
T
A max
is therefore,
contrary to
T
C max
, an indicative value only.
Caution:
The installer must ensure that under all operating
conditions
T
C remains within the limits stated in the table
Temperature Specifications.
Notes:
Sufficient forced cooling or an additional heat sink allows
T
A to be higher than 71
°
C (e.g., 85
°
C) if
T
C max is not exceeded.
For -7 or -9 models at ambient temperature
T
A = 85
°
C with only
convection cooling; the maximum permissible current for each
output is approx. 40% of its nominal value as per the figure below.
Output Protection
Each output is protected against overvoltages which could occur
due to a failure of the internal control circuit. Voltage suppressor
diodes (which under worst case condition may become a short
circuit) provide the required protection. The suppressor diodes are
not designed to withstand externally applied overvoltages.
Overload at any of the outputs will cause a shut-down of all
outputs. A red LED indicates the overload condition.
Parallel or Series Connection
Single or double-output models with equal nominal output voltage
can be connected in parallel without any precautions using
Option T (current sharing).
Single output models and/or main and second outputs of double-
output models can be connected in series with any other (similar)
output.
Notes:
– Parallel connection of double output models should include both,
main and second output to maintain good regulation of both
outputs.
– Not more than 5 models should be connected in parallel.
– Series connection of second outputs without involving their main
outputs should be avoided as regulation may be poor.
– Rated output voltages above 36 V need additional measures in
order to comply with the safety requirements for SELV (Safe Extra
Low Voltage)
I
o
/I
o nom
Forced cooling
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
05089_052305
– The maximum output current is limited by the output with the lowest
current limitation if several outputs are connected in series.
Output Voltage Regulation
The figure below applies to single-output or double-output
models with parallel-connected outputs.
T
C max
0.98
V
o
V
o nom
05098_050605
Convection cooling
T
A min
50
60
70
80
90
100
T
A
[˚C]
0.5
I
o1
I
oL
Fig. 7
Output current derating versus temperature for -7 and -9
models.
Thermal Protection
A temperature sensor generates an internal inhibit signal which
disables the outputs if the case temperature exceeds
T
C max
.
The outputs are automatically re-enabled when the temperature
drops below this limit.
Continuous operation under simultaneous worst-case conditions
of the following three parameters should be avoided: minimum
input voltage, maximum output power, and maximum
temperature.
0
0.5
1.0
I
o
I
o nom
Fig. 8
Output Characteristic V
o1
vs. I
o1
(typ.)
APR 26, 2006 revised to MAY 15, 2006
Page 10 of 34
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