149 / 2663 CIRCUIT DESCRIPTION
Art. No.: 80116-201
09 / 2004
is no longer switched through for actuation of the QK output stage, but instead the output signal of the
comparator IC9, PIN 12.
This comparator detects the zero crossings of the high frequency current of the QK output stage and provides
a pulse at the rate of the HF at the priority encoder which switches this rate through to the actuation with
sufficient current flow of the output stage. In this way, the actuation has now been switched over from free-
wheeling by means of the start generator in a no-load case to feedback current control in a load case.
Hardware electronic safety circuits
The current from the QK output stage is measured one more time:
First the measurement voltage is divided by means of the divider R57, R61, then rectified using diode D10
and an average is generated using the time constants from the resistor R50 and the capacitor C10. As a
result, the comparison voltage from the divider is present at the input of the comparator IC4, on the one
hand, and on the other, the average of a voltage which corresponds to the average current of the output
stage. If the average output stage current exceeds the set threshold, the comparator tilts. Its output signal
blocks actuation of the output stage via the AND gate IC7, Pin 4, and the QK output stage is blocked for a
specific minimum time prescribed by the monoflop IC10, part 2. In this way, the circuit is provided with a
recovery time and a pump effect is avoided.
This is therefore an electronic fuse for the QK output stage.
In a similar manner, further measurement dimensions are monitored not only through software, but also
through hardware:
Voltage and current of the patient circuit are directed via their parameters UP_HF and IP_HF from the
Senso-board on the comparator IC6. This also applies to the voltage from the power supply unit U_NETZT
and its current U_INT from the power module.
The integrated module IC6 is a comparator, the threshold voltage of which can be preset as a digital word
via the control bus. In this way, the threshold voltage can be adapted to current requirements prescribed by
the processor. The comparator compares the analog instantaneous values with those limit values set by the
processor and passes its Yes/No decisions on to the NOR circuit IC5. There the signals are summarized and
directed to gate IC7. If one single parameter has exceeded its limit value, the QK output stage actuation is
blocked by the AND circuit IC7. At the same time, the monoflop IC10, Part 1, is triggered, maintaining the
blockade for a specific minimum time, so that a pump effect caused by switching off and back on again too
quickly is avoided.
Via the second part of the AND circuit IC7, further important enable signals are controlled for the QK
output stage:
• Is there an enable signal from the processor?
• Is the safety interlock signal giving its enable?
• Is there currently no reset of the processor?
If any of these questions can be answered with NO, the QK output stage is blocked.
The spark control
Several ICC units offer both a control of the HF output voltage as well as optionally a control of the
Control board
Slot J3
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