Control Board
Principles of Operation
LigaSure Vessel Sealing Generator Service Manual
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The master microcontroller, using the dosage error algorithm, checks to make sure
the feedback microcontroller is operating the generator within specific
parameters:
•
During idle, the main sensors receive less than 50% of full scale.
•
The high voltage (HV) power supply board control signal is greater than 90%
and the V/I signals are less than 10% of full scale.
•
The HV power supply and the HV sense signals are within one volt of each
other.
•
The power readings at the main and feedback microcontrollers do not differ
by 50 watts or more.
•
Sensors connected to the main microcontroller are
not
stuck at 100% of full
scale.
•
Desired power at the main and feedback microcontrollers are the same.
•
Actual power is below the error threshold as defined by IEC 60601-2-2,
Dosage Error Limits.
If the algorithm detects that the generator exceeds one or more these parameters,
it signals an error condition. The system displays an error message and shuts
down all generator output.
Instant Response Algorithm
This algorithm controls the current, power, and voltage adjustments for all modes.
Controlling the maximum output voltage reduces high frequency leakage, reduces
video interference, and minimizes sparking. At low impedances, keeping the
current constant protects output circuitry. At high impedances, keeping the
voltage constant limits arcing and electro-magnetic interference.
Constant Current
The algorithm holds output current constant according to this equation:
I = (P/R) ˆ(1/2)
where I is the output current, P is the power set by the user, and R is the constant
current to constant power impedance switchpoint.
Constant Power
The algorithm maintains the power set by the user.
Constant voltage
The algorithm controls the output voltage according to the following equation:
V = (P*R) ˆ(1/2)
where V is the output voltage, P is the power set by the user, and R is the constant
power to constant voltage impedance switchpoint. In some high impedance
conditions, the algorithm modifies this equation to reduce voltage more rapidly.
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