Hold-up time – Rockwell Automation 1606-XLDC92D Power Supply Reference Manual User Manual

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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

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

12ms

28Vdc

Input Voltage

Hold-up Time

(a) 24V, 1.9A, typ.
(b) 24V, 1.9A, min.

(a)

(b)

(c)

(d)

Fig. 6-2 Shut-down test setup

Fig. 6-3 Shut-down behavior, definitions

Load

DC/DC

Converter

Source

Input

Output

- 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.