Control Board
Principles of Operation
Force EZ-C Series Service Manual
5-11
Instant Response Algorithm
The Force EZ-C Series Electrosurgical Generator’s Instant Response system is a
closed loop control algorithm implemented in microcontroller firmware. The
system applies it to some settings, but not others:
•
Applied to
•
bipolar
•
monopolar cut modes
•
low 2 coag
•
low 3 coag
•
Not applied to
•
low 1
•
high 1
•
high 2 coag
As tissue impedance increases from short circuit to open circuit, the algorithm
implements first constant current, then constant power, and finally, constant
voltage. Controlling the maximum output voltage reduces capacitive coupling,
reduces video interference, and eliminates sparking. At low impedances, constant
current protects output circuitry. At high impedances, constant voltage control
limits arcing and electromagnetic interference (EMI).
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.
High Impedance Instant Response Operation
The firmware algorithm clamps the output voltage to specific levels for high
impedance conditions. The clamp level is a function of the active mode. This
helps prevent arcing and electromagnetic interference (EMI).
