Johnson & Johnson ETHICON ENDO-SURGERY HARMONIC 300, Service Manual

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9
GEN04
Chapter 3 - Theory of Operation
The H
ARMONIC
™ Generator 300 System consists of the following components: Generator (GEN04),
hand piece, instruments, foot switch, and hand switching adaptor (if used). The generator produces an electric
signal, which is transmitted via a coaxial cable to the hand piece, which then converts the electrical signal
into ultrasonic, mechanical motion.
Hand Piece
The hand piece houses several major components that generate, amplify, and deliver ultrasonic energy to the
instrument end-effector. When each component is attached to the other and tuned, an acoustic drive train is
formed. Two key parts of the acoustic system or acoustic drive are:
Acoustic Transducer: Converts the electrical energy into motion. When an AC waveform is applied to the
transducer, the piezoelectric material expands and contracts to produce longitudinal motion.
Instrument: Couples the ultrasonic energy to the tissue and amplifies motion. In a laparoscopic configuration,
the instrument is elongated by means of a "Laparoscopic Extension." This extension allows the ultrasonic
energy to propagate from the hand piece to the instrument with minimal loss.
Generator
The generator converts the AC line voltage to a controlled DC level. The DC level is then modulated at the
resonant frequency of the hand piece. The modulated signal is then filtered and delivered to the hand piece,
where it resonates the acoustic drive train. A more detailed description follows.
Power Entry Module: Accepts a standard, hospital grade utility cord. Refer to Chapter 14 – System
Specifications for details. Provides susceptibility filtering from the external environment as well as
suppressing electromagnetic emissions produced by the generator that could be conducted back through the
power cord.
Power Supply: Provides 48 VDC to DC/DC Converter and Current/Power Regulation Circuit.
Current and Power Regulation Circuit: Provides Current/Power regulation. Current limit circuits protect these
assemblies and others from overload conditions.
Patient Isolation Circuit: Provides a safety isolation barrier to patient and/or user. The voltage generated on
the secondary of the transformer is isolated from the primary and thereby not referenced to earth ground.
Microprocessor: The microprocessor contains the software program that drives the H
ARMONIC
™ Generator
300 System. The software provides the user interface, frequency drive signal, as well as drive signals to the
Liquid Crystal Display, front panel indicators, and generator audio circuit.
Liquid Crystal Display and Front Panel: The Liquid Crystal Display and front panel indicators report the
operating mode of the H
ARMONIC
™ Generator 300 System. They are driven by the microprocessor.
Foot Switch and Hand Switching Adaptor
Foot Switch(es): The foot switch(es) allow(s) the user to activate the system in either the minimum (MIN) or
maximum (MAX) modes based on which foot pedal is being pressed. Pedal activations are communicated to
the microprocessor.
Hand Activation Circuit: The hand switching adaptor allows the user to activate the system in either the
minimum (MIN) or maximum (MAX) modes based on which button is being pressed. Hand activations are
communicated to the microprocessor.