Bovie Aaron 1250, Руководство по обслуживанию, Страница: 40 / 68

RF Amplifier Circuit
The RF Amplifier Circuit generates the RF output energy that is delivered to the patient. It is a single-ended power
amplifier incorporating three power MOSFETs, and two step-up transformers.
The initial RF drive pulse is generated by the Digital PWM circuit and the system logic unit. When the RF drive
pulse turns the power MOSFETs "ON," current flows from the high voltage supply through one of the output
transformers, depending on which mode the unit is in, through the clamping diodes, and then through the
MOSFETs to high voltage ground.
The energy developed by the "ON" time is stored in an LC tank circuit. When the MOSFETs are OFF the energy is
delivered to the patient through the output capacitors. A longer "ON" time develops more energy in the LC tank cir-
cuit; therefore, more energy is delivered to the patient.
Monopolar Select Circuit
The monopolar select circuit is used to switch the Aaron 1250 between each of the four-monopolar modes. Selection
of the modes is accomplished through the matrix switches on the front panel. High voltage relays are used to switch
and isolate the four-monopolar configurations one from the other.
Monopolar / Bipolar Select Relays
The monopolar / bipolar select relays changes which output transformer is used to deliver the RF output to the
patient.
Controls and Indicators
The Aaron 1250 controls and indicators are listed below:
• MEMBRANE SWITCHES Toggle between modes.
• DISPLAYS Seven segment displays indicate the output power in watts.
• MODE INDICATORS Green LEDs indicate the present mode of the unit.
• POWER CONTROL KNOBS These mechanical encoders adjust the output power for each mode.
• POWER SWITCH A double pole single throw switch that snaps into the front bezel. This switch supplies the AC
mains current to the generator.
Digital PWM Circuit
The Digital Pulse Width Modulation (PWM) Circuit controls the output power of the unit. This digitally controlled
signal is used by the system logic to provide a precise signal to the RF drive.
The pulse width is determined by power setting (generated by the user) on the front of the unit.
When a power is selected, the system logic determines what the pulse width needs to be to deliver the requested
output.
SYSTEM LOGIC
The control logic uses a Field Programmable Gate Array as the “brain” of the Aaron 1250 Electrosurgical Generator.
This system interprets all of the inputs and delivers the correct corresponding outputs.
Every operation of the unit is controlled from this system.
A System Clock Circuit, composed of an oscillator, provides the basic operating frequency of 5 MHz.
The Reset Circuit provides a single pulse at the time the Aaron 1250 Electrosurgical Generator is turned on.
This pulse resets Field Programmable Gate Array to ensure proper operation.
40 Bovie / Aaron Medical