LIFEPAK 20/20e Defibrillator/Monitor
Device Description
Functional Description
(continued)
A04 Therapy PCB
(continued)
■
Power Switch
— A power switch is a control circuit that detects the
ON
button selection from the A05 User Interface PCB or a timer event from the
A01 System Control PCB to power up the device. This portion of the
A04 Therapy PCB is powered at all times, with very low quiescent current
draw. When a power-on request is detected, this circuit switches VBatt
(battery and/or ac converted dc power) provided by the A03 Power Module
to the remaining PCBs in the device. Low Battery (Battery Fail) is detected
and a discrete signal is broadcast to other PCBs if battery voltage falls
rapidly or reaches the point where normal operation is no longer feasible.
■
Cap Charger
— The cap charger is a high-voltage, patient-isolated circuit
that charges the A13 Energy Capacitor to the correct voltage for biphasic
defibrillation (2 to 360 joules). Control is provided by the CPU, and capacitor
voltage is provided back to the CPU for feedback. The cap charger is
designed to nominally provide maximum charge rates and to automatically
scale back to slower charge rates when low battery voltage is detected.
■
Pacer Power Supply
— The pacer power supply is a patient-isolated circuit
that charges the A13 Energy Capacitor up to the correct voltage for pacing.
Control is provided by the CPU, and voltage regulation is maintained locally
within the pacer supply. Capacitor voltage is provided back to the CPU for
control through the cap charger circuitry.
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