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3.1 FUNCTIONAL DESCRIPTION
The Functional Block Diagram appears in Figure
5.3. This diagram illustrates the functional parti-
tioning of the unit. Each block defines a major
function along with the reference designator(s) of
the component(s) that serve primary roles in
implementing the function. Dashed lines enclose
major assemblies (A-) for cross-referencing to the
Interconnect Diagram or Assembly Schematics
in Section 5.
The relationships among each block are described
by the signals that interconnect them. Narrow
lines represent individual signals and are marked
with the same signal mnemonics used in the
schematics.
Broad lines denote busses, or groups of signals
which together serve a common function. To
avoid clutter, busses are not necessarily marked
with signal mnemonics. Where a bus contains sig-
nals all bearing a common mnemonic form, the
characters common to all of the mnemonics are
shown, with XXs denoting characters which differ
among the signal names. For example, the bus
marked /FXX contains the signals named /FCT
and /FCG. These refer to the foot switch activa-
tion signals for Cut and Coag respectively.
Arrowheads describe the direction of signal flow.
Most signals are generated at a single source and
have one or more destinations. An exception is
the Data Bus on the A3 Controller PWB. This
bus is bidirectional in that signals may travel
either direction from any one of a number of
sources. However, only one source may be active
at a given time. That source is determined by the
Microprocessor which drives the proper signal
states out on the Address and Control busses.
Power supply and distribution are not shown in
the Functional Block Diagram. This information,
along with further detail regarding the circuitry
shown in Fig. 5.4 is discussed in Sect. 3.7.
Theory of Operation
Section 3.0
3.2 RF OUTPUT SECTION
Refer to Figure 5.7 for the schematic diagram.
This section is located on the forward end of the
A4 Power PWB. Its purpose is to isolate the
patient-connected circuitry from earth while deliv-
ering RF output power, monitoring the return
contact quality and activation switch closures.
3.2.1 RF Output Coupling
RF output power may be supplied through one
of two RF isolation transformers, as selected by
the Bipolar relay, A4K3. When de-energized, K3
connects the power amplifier collector bus to the
Monopolar output transformer, T3, which is res-
onated by C60 and C61 and damped by R100.
The main secondary of T3 is capacitively coupled
by C69 and C70 to the patient plate output jack
and via high-voltage reed relays, to the user
selected monopolar active accessory connectors.
An auxiliary single-turn T3 secondary supplies a
replica of the power amplifier collector voltage to
the VSENSE circuit. This rectifies and peak-
detects this signal for use by the control circuitry
to limit output voltage in Cut.
When K3 is energized, it disconnects T3 and sup-
plies the Bipolar output transformer, T1, with
power from the power amplifier. The primary of
T1 is resonated by C62 and is damped by R100.
This transformer is designed to meet the particu-
lar requirements of bipolar electrosurgery which is
characterized by much lower impedances and per-
missible voltages than those in monopolar opera-
tion. Its secondary is capacitively coupled to the
appropriate output connectors. Output wave-
forms under various conditions are shown in
Figure 3.1.
CAUTION: Because of the high peak-to-peak
amplitudes of these waveforms, use oscillo-
scope probes that can withstand 2 KVpp mini-
mum for cut, 12.0 KVpp minimum for coag,
and 500 Vpp minimum for bipolar.
3-1
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