Erbe ICC 200, Service Manual

Page: 156 / 266

156
/ 266
3 CIRCUIT DESCRIPTION
Driver and output stage of the HF generator
The actuation signal for the HF output stage is generated on the control board (IC16) and fed to the power
module driver IC1 via the motherboard.
Due to the high-gate source capacitance of the output stage transistors T1 and T2, the driver must be able to
emit and accept high reactive currents when transferring this capacitance. That is why two drivers are
switched in parallel. The output current of the driver is restricted by the resistors R1 and R19 to protect the
driver.
The output stage transistors T1 and T2 are switched in parallel due to the necessary high current and
operate on output transformer UE1.
Output circuit of the HF generator
The output circuit of the output stage consists of the transformer UE1 on the primary side and the two
capacitors C5 and C7 switched in parallel. This parallel circuit is designed for the operating frequency of
the HF generator and forms a sine-wave voltage in a no-load case.
At the secondary side, there is a serial circuit made up of coil L1 and the capacitor C1. This serial circuit is
also designed for the operating frequency of the HF generator and produces a sine-wave current in the
output circuit.
In this way, in every load state of the generator, both the voltage and the current are sinusoidal.
Measurement of various operating parameters
The output current in the QC power stage flows via the transformer UE3 which is secondarily loaded with
the resistors R13, R14 and R15 and is used as a current transformer.
The voltage at these resistors corresponds to the output voltage of the QC power stage (half-cycle current)
and is routed as U-IHP to the control board.
The current in the power supply unit is measured at shunt R5 and routed as U-INT (voltage as a function of
the power supply current) to the control board.
The output voltage of the power supply unit is divided via the resistors R7, R8 and routed as U-NETZT to
the control board (IC14).
The HF primary voltage of the output stage is picked up at the oscillating circuit capacitor C5 and routed as
U-PRIM to the control board (IC14).
The output stage temperature is recorded by the thermistor NTC1 and routed as voltage from the divider
R2, NTC1 with the designation TEMP to the control board (IC2).
Power module
Slot J5
Power module UL
Slot J5