155 / 2663 CIRCUIT DESCRIPTION
Art. No.: 80116-201
09 / 2004
Power module
Slot J5
Power module UL
Slot J5
The following assemblies are found on the PCB:
• Serial oscillating circuit for the QC power stage
• Generation of the operating voltage for the HF generator
• Driver and output stage of the HF generator
• Output circuit of the HF generator
• Measurement of various operating parameters
Serial oscillating circuit for the QC power stage
The QC power stage has the task of generating a sine-wave current as free of distortion as possible. The QC
power stage is not used in the ICC to generate high-frequency power for cutting or coagulating, but instead
functions here as a switched-mode power supply unit with a high switching frequency and efficiency. The
QC transistors are always switched over in the zero crossing of the current. The current is forced at the
same time through the serial circuit from coil L2 and capacitor C17 into a sinusoidal shape.
Generation of the operating voltage of the HF generator
The high-frequency power is tapped via the transformer UE2 and rectified by means of the diodes D3, D4.
The capacitors C4, C10 are filter capacitors. With 22 µF, they can be measured relatively minimally and the
ripple of the output voltage is nevertheless small due to the high operating frequency. In this way, this
switched-mode power supply unit can also be stabilized very quickly.
The output DC voltage of the power supply unit is available at the cathode of diode D3 and is
a) directed via the U–NT–STE connection to supply the ST output stage,
b) used to operate the HF output stage via relay REL1.
The negative pole of the capacitor C10 leads to the chassis via the resistor R5. R5 is used as a shunt to
measure the output current taken from this power supply unit. The voltage alloted to R5 if used for
measurement by U–INT.
In the activation pauses, the power supply unit can be discharged via NTE (power supply enable). To do
this, the transistor T3 is switched conductively and discharges the stored power supply voltage via the
resistor R12.
The power supply output voltage is divided into smaller values via the resistor divider R7, R8 and lead to
the measuring device (U-NETZT).
Via the relay REL1, the transformer UE2 can be switched over. With an activated relay, a higher output
voltage can be taken from the transformer. This is required to operate the ST output stage to generate
especially high voltage peaks. This high voltage is switched off to protect the HF output stage by means of
the second contact from relay REL1.
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