Physio Control LIFEPAK 9 - Page 23

BATT CHRG Indicator
Power Conversion
PCB Assembly
(803724)
Power Control
© August 1993 Physio-Control
Description 1
the battery at approximately +4.5A. This limit is implemented when the
Power Supply PCB sources current into a dead short, a requirement when
charging a severely depleted battery.
A battery-charging LED signal illuminates the front panel BATT CHRG
indicator whenever the ac power is connected to the instrument and the rear
panel mains power switch is on. An interlock in the battery harness prevents
the indicator from lighting if the battery is not installed.
The Power Conversion PCB contains circuitry for power on/off switching,
additional voltage generation and monitoring, energy storage capacitor
charging, and defibrillation energy transfer. Refer to Figure 1-3, page 1-10.
The Power Control circuit regulates battery voltage for the circuits which
control instrument operation. The circuits directly affected by the Power
Control circuit are: Switching Power Supply, Logic Power Monitor, External
Control Input, Low Energy Charge Rate, and Energy Storage Capacitor
Charger circuits.
The Front Panel ON momentary pushbutton provides the start-up signal for
the Power Control circuit. When the power switch is first pressed (turning
power on), V BATT passes to the gate of Q11, causing Q11 to conduct,
which in turn causes Q10 to conduct. A portion of V BATT is held on the
gate of Q11 by R52, which keeps Q10 conducting. During this time the
PWR SW MONITOR line is low and the Power Control circuit provides the
SWBATT voltage for the rest of the Power Conversion PCB Assembly
circuits.
When the power switch is pressed a second time (turning power off),
V BATT is divided by R108 and R109, forward-biasing CR44 and switching
the PWR SW MONITOR line high. The System microprocessor reads the
low-to-high transition and activates the Logic Power Monitor circuit,
disabling the Power Control circuit. The functional integrity of the Power
Control circuit may be confirmed by monitoring two pins on the test
connector: R60 (connects to the gate of Q10) and R57 (connects to the gate
of Q11).
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