Functional Description

Functional Description

The overall function of the LIFEPAK 9A defibrillator/monitor is shown in Figure 1-2. The defibrillator/monitor includes six mechanical assemblies (Keypad, Rear Panel Membrane Switch, Strip Chart Recorder, Transfer Relay, Paddles, and Battery Pack) and five Printed Circuit Board (PCB) assemblies (Power Supply, Power Conversion, Interconnect, Main, and Display).

The Keypad and Rear Panel Membrane Switch Assemblies receive operator input. The Strip Chart Recorder Assembly provides printed output. The Transfer Relay and Paddle Assemblies help deliver defibrillator pulses. The Battery Pack provides temporary backup power.

The Power Supply PCB functions over the full range of input voltages from 90Vac to 270Vac at 50Hz or 60Hz without input line voltage selection. The Power Supply PCB converts the ac line power to the nominal +18.4Vdc supplied to the Power Conversion PCB.

The Power Conversion PCB performs a variety of power-handling functions: power on/off switching, generation of additional power supply voltages, defibrillation charging, and stored energy transfer. A test load circuit is also present on the Power Conversion PCB.

The Interconnect PCB provides the electrical connection between the Main PCB and the Power Conversion PCB. It also contains circuitry to produce the audible tones and to drive the front panel LEDs.

The Main PCB has three major sections of circuitry: the Preamp, the System Controller, and the Display/Recorder Interface. The Preamp receives input from both the 3-lead patient cable and QUIK-LOOK paddles inputs. The System Controller directs the overall operation of the other circuits. QRS detection, rate calculation, and synchronous cardioversion are all implemented in the System Controller software. The current state of the System microprocessor and the ECG data are transmitted from the System microprocessor to the Display/Recorder microprocessor, allowing the Display/Recorder microprocessor to select and format the appropriate CRT messages and recorder annotations. The Display PCB/CRT Assembly contains a Monitor PCB that drives the 5-inch diagonal Cathode Ray Tube (CRT). It uses electromagnetic beam deflection and incorporates vertical and horizontal deflection circuitry to produce a raster scan.

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