Table of Contents
Advertisement
T e c h n i c a l I n f o r m a t i o n
Battery Charge Monitor
This PSU output has two functions. In the 0V-2.5V range it indicates the
magnitude of the battery charge current (indicates 2.0V +/-10% at 0.5A).
If there is a fault in the battery system the PSU should drive the output
high (greater then 3.1V) to indicate the condition.
AC Good
This output indicates that the AC supply is within specification. The
System Management Unit uses this output to recognise whether the DC
output modules are powered by AC input or by the battery. This output is
activated (logic high) in the Standby and Power On modes. It is negated
(logic low) in the Backup and Power Off modes.
PSU state diagram
Low Battery OR
Shutdown=True
OR Fault
Backup
AC Good =False
OR
AC input>15A
Figure 5-7 PSU State Diagram
The "Deep discharge" transition on the state diagram occurs when the
PSU detects a very low battery voltage while it is providing a Standby 5V
supply in Power Off mode. This can occur due to excessive battery drain
or the batteries being disconnected by the circuit breaker. In the case of
battery exhaustion in Backup mode, the PSU will remain in the Power
Off state for at least 0.5 second before entering the Dead state. If the
circuit breaker disconnects the batteries, the transition from Backup to
Dead may be instantaneous.
The "Fault" entries in the table below correspond to the equivalent
transitions on the state diagram. Other PSU failures may also cause the
"Fault" transition.
5-54 OWNER'S HANDBOOK
Power Off
(AC Good=False
(AC Good=False
AND Low Battery)
OR Fault
AC Good=True &
!15A Latch
Shutdown=True
AC Good=True &
15A Latch &
Power Up
Power On
AC Good=False
AND
Deep Discharge
Dead
AC Good =True
OR Fault
Standby
Power Up =True
Advertisement
Table of Contents
