User's Manual

Doc. No.
Rev.
Date
1.00
2011-12-08
Damm Cellular Systems A/S, Denmark
TETRAFLEX
®
V7.5 MANUAL - Power Supply for BS41x
TetraFlex® 7.5 Manual 4-27
The actual produced output voltage depends of the configuration. When battery charging is
active, the delivered output voltage will vary around 54V, controlled of the micro-controller.
The accurate value is determined of the charging voltage setting, consisting of a fixed voltage
part and an associated temperature compensation setting.
When charging is not selected or the external temperature sensor is not working, the rectifier
will deliver 48.0V fixed.
Two different connections are provided on the back plane:
 –48V Battery connection
 –48V DC external load
The –48V battery connection is provided with a current sensor to measure the actual battery
charge/discharge current.
The –48V DC external load connection allows the Base Station to drive external units, e.g.
Ethernet switches, E1 modems etc.
4.6.3 +14V and +26V DC/DC converters
The PS411 Power Supply contains two independent DC/DC converters providing +14V and
+26V respectively from the –48V DC input.
The outputs are fed to two power rails on the back plane. Independent power-share circuits
on each converter ensures about equal load on all inserted PS411.
The input to the two converters comes from the external –48V rail. An internal feed is also
provided allowing the converters to run even if the external –48V rail is short-circuiting to
ground.
The DC/DC converters are able to run on –48V as provided of the rectifier or an external
battery.
The input of the DC/DC converters are provided with an under-voltage detector to turn off the
load on the battery when nearly discharged to prevent deeply discharge of the battery, which
could affect its lifetime. The turn-on voltage is about 45V DC and the turn-off voltage about
40V DC. The 5V hysteresis is provided to prevent oscillations between on and off.
4.6.4 Micro-controller