User manual

CD5.121
CD–Series
DC/DC Converter; 12V, 8A
Jan. 08 / Rev. 1.1 DS-CD5.121-EN / All parameters are specified at 12V, 8A and 24Vdc input at 25°C ambient unless otherwise noted.
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8. 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.
Input 24Vdc
Hold-up Time typ. 12.8ms Input 24Vdc, Output: 12Vdc, 4A, see
Fig. 8-1
typ. 7ms Input 24Vdc, Output: 12Vdc, 8A, see Fig. 8-1
Fig. 8-1 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. 8-2 Shut-down test setup Fig. 8-3 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.