RF Board
Principles of Operation
LigaSure Vessel Sealing Generator Service Manual
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RF Output Relays
Based on footswitch or handswitch requests, relays RL1 through RL6 multiplex
the developed RF energy for distribution to the seal and bipolar output
receptacles.
Command signals originating in the microcontroller route to the RF board to relay
driver chip U12. Upon receiving a positive logic +5 V signal request to the input
of U12, the relay driver output goes low to energize the respective relays and
close the relay switch contacts. Relay switch closure, which provides bipolar RF
energy to the output, is equivalent to a double pole single throw switch. This
avoids a potential patient hazard by eliminating RF energy on any output
receptacle pins when footswitch and handswitch requests are not active.
The method of output relay switching is cold switching the relay contacts. Cold
switched relay contacts make and break contact connections when no RF voltage
or current is present. This promotes an increased life cycle and an increased mean
time between failure (MTBF) for the relay by avoiding the excess contact burn
and premature contact failure experienced with hot switched relay activations.
The following table identifies the output relays activated by the microcontroller
command signals. It also identifies the RF output energy delivered to the
respective output receptacles.
EKG Output Relay
The previous table also lists a relay that does not actively switch RF energy. A
po5 V signal, represented by the RFACT_RLY command input from the
microcontroller to U12, energizes relay K1B. Relay contact K1B provides
isolated SPST switch contact closure when the system generates and delivers any
RF energy in any operative seal or bipolar mode. The K1B switch contact closure
communicates to peripheral equipment in the operating room that RF energy is
present.
Command Signal Inputs
to U12
Output
Relays
Switched
RF Energy
Delivered
Output
Receptacle
RF Activation
Pin
Signal
1
VSRF/
Vout_RLY
RL1A, RL6A
Seal
LigaSure
2
BPRF/
Vout_RLY
RL4A, RL5A
Bipolar
LigaSure
3
BPRF/
Bout_RLY
RL2A, RL3A
Bipolar
Bipolar
4
RFACT_RLY
K1B
None
None
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