Rockwell Automation 1606-XLDC92D Power Supply Reference Manual - Manual (Page 7)

All parameters are specified at 24V, 3.8A, 24Vdc input voltage, 25°C ambient and after a 5 minutes run-in time, unless noted otherwise.
Rockwell Automation Publication 1606-RM023A-EN-P — January 2014 7
Bulletin 1606 Switched Mode Power Supplies
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. 13.8ms input 24Vdc, output: 24Vdc, 1.9A, see Fig. 6-1
typ. 7ms input 24Vdc, output: 24Vdc, 3.8A, 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) 24V, 1.9A, typ.
(b) 24V, 1.9A, min.
(c) 24V, 3.8A, typ.
(d) 24V, 3.8A, 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
+
-
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 at this time.