DCU20
User Manual rev. 19
Page 9/29
In case the load (PC) current exceeds the DCU20 dry contact rating the use of an external relay with
suitable current/voltage rating is needed, relay coil voltage shall match output voltage. It should be
driven by the DCU20 internal dry contact.
Fuse 5x20
4A Fast
OUTPUT-
Figure 3: Internal relay
OUTPUT-
Relay
Figure 4: External relay
The diagram below shows the DCU20 behavior when Shutdown and automatic restart is enabled.
Time
PC OFF signal
PC status
Output voltage
Output current
Input voltage
T1
T2
T3
...
...
T4 T3
E3
E1
E2
E4
Ioff
Figure 5: Shutdown and restart chart
Parameter Name
Description
E1
Backup
Power failure on the line happens. System enters backup mode.
E2
Automatic PC
shutdown
The
POWERMASTER
sends a shutdown command to the PC.
Optionally: a task is called before shutdown.
This
event is triggered by the “
PC shutdown delay
”
(§5.2.23) or
“
Battery low alarm
” (§5.2.8), whatever comes first.
E3
Unexpected PC
shutdown
The PC shutdowns in an unexpected way, for example caused by
OS crash.
E4
PC restart
DCU20 detect the PC being OFF because the output current was
9
DCU20_1680-21539-0006-E-1117