Siemens SC 7000 Service Manual page 33

SC 7000 and SC 9000XL Patient Monitors
6.1.3 Power On / Off
6.1.4 Power Source Control
6.1.5 Battery charging
6.1.6 Indicator LEDs
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It also provides a safety timer for the NBP pneumatics, which are controlled
by the main processor FPGA.
Logic circuits on the main gate array sequence the power to the Pods,
Cartridges, and Recorder to reduce power on load transients.
The monitor is normally switched on by the user pushing the On/Off button
for at least 1 second. (The monitor may switch on when the switch is
pushed for as short a time as 50 msec.)
The power down sequence may be initiated either by the user pushing the
on/off switch for at least 1 second or when the batteries are depleted. When
the power down sequence is initiated, the power conversion board control
logic generates an interrupt for the processor. 100 ms later, the power
supply shuts down. An immediate shutdown is initiated if a power fault
occurs (such as overvoltage).
Power for the monitor is provided by the Docking Station / PSL, External
(Auxiliary) Battery, or Main (Internal) Battery.
The PSL and Docking Station inputs are wired in parallel and are therefore
treated as a single power source. This input is monitored by a voltage
comparitor to determine that adequate voltage is present for Dock Power
operation. The main and external batteries also have voltage comparitors
indicating that their voltage is high enough to provide power.
Based on the information provided by the comparitors, a power source is
connected to VBUSS in the priority of docking station, external battery, and
then main battery.
The battery charger is a two-level constant voltage charger with a fixed
current limit and temperature compensated voltage levels. When the
docking station power comes on, the main battery is fast charged at the
high voltage until the current drops below a specific threshold. Then the
charger switches to charge the auxiliary battery. When both have been
charged, the charger voltage drops to the lower "float" voltage and is time
multiplexed between the two batteries.
Since the presence of the auxiliary battery is established by the voltage
comparitor, a means for detecting that it has been unplugged during the
charging process is necessary. For this reason, the external battery voltage
comparitor is disabled during the battery's "float" charge interval. This
function is not needed during the fast charge interval since no current will
flow when the battery is disconnected and the fast charge mode will be
exited automatically.
The fast charge cycle for the main battery is initiated every time the docking
station power comes on. The auxiliary battery will fast charge every time the
main battery finishes the fast charge or when the main battery is charged
and the auxiliary battery is plugged in.
Two green LED indicators on the front bezel of the monitor indicate power
and charger status, as given in Table 2-1.
Table 2-1 Power and Charger LED Indicators
LED
Power Processor power on
processor power off
Siemens Medical Systems, EM-PCS Danvers
NOT A CONTROLLED DOCUMENT
CONDITION LED STATE
on
off
Service Manual
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