Utah Medical Products FINESSE +, Service Manual

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Service Manual
27
Circuit Descriptions
The is an electrosurgical device powered from 115VAC or 230VAC, 50Hz or 60Hz mains
supplies. The power mains branch into two main modules — the electrosurgical system and the
smoke evacuation system. Independent sets of fuses protect each circuit module. The main
power switch is mounted on the front panel, and when toggled allows power to flow from the AC
receptacle to both the main power transformer and smoke evacuation module.
The core of the system contains a microprocessor and complex programmable logic
device (CPLD). Many of the 's logic functions have been permanently embedded in the
CPLD to reduce the amount of circuit components used and decrease the probability of
component failure.
The microprocessor and CPLD are not user programmable or modifiable. No
attempt should be made to do so.
Power Supply
The Power Supply Board is the power interface between the other circuit boards and the power
transformer. The primary functions of the Power Supply Board are to 1) supply working voltages
for the circuitry and 2) control the smoke evacuator vacuum motor speed, which is
signaled by the Logic Board and at a speed determined by the speed control switch on the front
panel.
Dual secondary windings on the main transformer provide AC power to the Power Supply Board
for rectification to unregulated 200VDC and 50VDC. The 50VDC is then regulated to 15VDC and
5VDC voltages for use on the RF Power Amplifier, Logic, and Display boards.
The Power Supply Board contains a solid state relay K201 that controls the smoke evacuator
motor. The smoke evacuation motor timing is controlled by the microprocessor on the Logic
Board through connector P204.
RF Power Amplification and Control
The RF Power Amplifier Board's main function is to provide electrosurgical output. Two pulse
width modulated signals control 's buck converter and waveform generator. The front
panel output setting controls are fed into the microprocessor. The Buck PWM base values are
determined by lookup tables in the microprocessor, and subsequently sent to the CPLD during
activation. The Buck PWM controls the 200VDC line. An increase in the duty cycle provides more
current to drive the output transformer. The Buck PWM is further modified according to data
received by the microprocessor from the output feedback circuit. A high voltage FET drives the
output of the Buck PWM circuit.
The Waveform PWM provides 450kHz switching to the other primary lead of the output
transformer. The microprocessor and CPLD drive the 450 kHz wave train according to the mode
selected, with pure cut mode being a continuous 450kHz wave train, Blend 1 being a train of 10
pulses followed by a rest period equivalent to 6 pulses, and so on for the other modes. The pulse