RF Board
Principles of Operation
LigaSure Vessel Sealing Generator Service Manual
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Operative Modes
The LigaSure generator provides three modes of operation, each of which delivers
bipolar RF energy through two front panel output receptacles. The seal,
macrobipolar, and bipolar modes develop RF energy derived from a common RF
source, located on the RF board. All modes provide output at a fixed frequency of
472.8 khz, providing an RF signal with either a continuous or pulsed mode
sinusoid waveshape.
In the seal mode, the developed RF energy originates at capacitor C59.
Multiplexed by relays 1b and 6b, the RF signal developed across capacitor C59
goes to RF board output connector J10. From connector J10, a cable carries the
RF energy to the front panel output receptacle, identified by the LigaSure logo, on
the left side of the generator. The seal mode output RF signal exhibits a pulsed
mode sinusoid waveshape. Closed loop software control initiated by the
embedded microcontroller board determines pulsed mode operation.
In the macrobipolar mode, the developed RF energy originates from the
cumulative output of a capacitor ladder network. Capacitors C58, C62, C59, C65,
and C66 form this ladder network to generate the macrobipolar output,
multiplexed through relays 2b and 3b, to RF output connector J11. From
connector J11, a cable carries the RF energy to the front panel bipolar output
receptacle, located on the right side of the generator below the macrobipolar and
bipolar power display. The macrobipolar mode RF output signal exhibits a
continuous sinusoid waveshape. The developed RF output voltage is greater than
the seal or bipolar mode outputs and has a unique power curve profile to cut
tissue. The microcontroller monitors the macrobipolar output and provides closed
loop control by sensing the tissue impedance and automatically adjusting the
output to achieve the desired clinical effect.
The bipolar mode RF operates from the same point of origin as the macrobipolar
mode. Its output, multiplexed through two pairs of relays, goes to both the seal
and bipolar front panel output receptacles. Relays 2b and 3b route the bipolar RF
to connector J11 for output energy distribution through the bipolar output
connector, while relays 4b and 5b route the bipolar RF to connector J10 for energy
distribution through the seal output connector. The microcontroller determines the
correct distribution of the bipolar energy based on footswitch and handswitch
activation requests. The bipolar mode RF output signal also exhibits a continuous
sinusoid waveshape with a unique power curve profile to coagulate tissue. The
microcontroller monitors the bipolar output and provides closed loop control by
sensing the tissue impedance and automatically adjusting the output to achieve the
desired clinical effect.
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