Pulsar
2
Service Manual
OPTIKON 2000
Cod. 111004SEN Rev.C
5-18
U8C and U8D are used as gates to apply the two square waves to the MC3452
(U16) MOSFET driver only when the control signal ENDIA, from the
microprocessor, is low (0 Vdc).
Two power MOSFET, Q4 and Q5, are operated by the MC3452 driver, their drain
is connected to the primary winding of L5 which provides insulation from the
part applied to the patient.
The amplitude of oscillation can be changed (from 0 to 7 Watt) by changing
the control voltage at the central tap of L5. The adjustable power supply
circuit is the same used for U/S section (see previous description of amplitude
control section).
Output stage consists of R63 and R64 resistors that discharge circuit
capacitance, from C55 and C56 low frequency (heart hazardous) blocking
capacitors and from low-pass pi filters consisting of C53, L6, R73, R72.
The DIATH front panel connector is wired to J4 through a decoupling toroidal
transformer located behind the panel. This transformer is intended to reduce
ground leakage currents. A voltage limiter across the secondary of the
transformer limits the open circuit maximum voltage of the bipolar diathermy.
Safety circuit
A simple Safety circuitry allows to the Control board to check if the 347150 is
generating a Diathermy or Ultrasound output (U/S_SIG and DIA_SIG) and to
measure the voltage level generated by the power supply module of the board
(U/S&DIA_PWR).
If a malfunction is detected (i.e. U/S or Diathermy are emitted when not
required or a wrong power level), The Control Board stops any power emission
driving U/S_SIG and DIA_SIG to a low level.
These signal lines are connected to J5.
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