Datasheet
CD5.121
CD-Series
DC/DC Converter 12V, 8A
6. HOLD-UP TIME
The input side of the DC/DC converter is equipped with a bulk capacitor which keeps the output voltage alive for a
certain period of time when the input voltage dips or is removed. The bulk capacitor can be discharged by loading the
DC/DC converter on the output side or through a load which is parallel to the input. There is no protection in the
DC/DC converter which prevents current from flowing back to the input terminals. If prevention is needed, an external
diode should be used.
Hold-up Time typ. 12.8ms input 24Vdc, output: 12Vdc, 4A, see Fig. 6-1
typ. 7ms input 24Vdc, output: 12Vdc, 8A, see Fig. 6-1
Fig. 6-1 Hold-up time vs. input voltage
0
2
4
6
8
12ms
18 20 22 24 28Vdc
Input Voltage
Hold-up Time
(a) 12V, 4A, typ.
(b) 12V, 4A, min.
(c) 12V, 8A, typ.
(d) 12V, 8A, min.
10
26
(
a
)
(
b
)
(
c
)
(
d
)
Fig. 6-2 Shut-down test setup Fig. 6-3 Shut-down behavior, definitions
Load
+
-
DC/DC
Converter
DC
Source
+
-
Input
Output
+
-
CD5
S1
- 5%
Hold-up Time
Output
Voltage
Intput
Voltage
S1 opens
Note: At no load, the hold-up time can be up to several seconds. The green DC-ok lamp is also on during this time.
Oct 2009 / Rev. 1.3 DS-CD5.121-EN
All parameters are specified at 12V, 8A, 24Vdc input voltage, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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