5 • Circuit Descriptions
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80116-443
10.16
Function 3 The controller supervisor functions as a low-active reset output. This out-
put leads to a defined input in the controller.
The power-fail signal is emitted when a voltage of less than 1.25 V is de-
tected at the PFI input. This voltage is tapped by the unregulated and only
weakly filtered 18 V via a voltage divider.
R1 = 100 KOhm; R2 = 7.5 KOhm,
U
PFI
= 1.25 V, U = 17.9 V
If the voltage after the rectifier is lower than 17.9 V, the processor detects
a power-fail.
Power switch
The power on/off switch disconnects the unit from the mains. The switch
is soldered directly to the printed-circuit board. It is a momentary-contact
switch.
Transformer (only for 100 and 120 V unit variants)
The ring core transformer sets the input mains voltage up to 230 V and
supplies the fan motor with the required energy via the mains filter.
Power supply
The power supply is subdivided into three main areas:
The three power supplies are effected via a transformer. The three voltag-
es are electrically isolated from each other.
Low voltage supply of
the electronics, display and
controller
This voltage is rectified via a bridge-connected rectifier and stabilized to 5
V using a switching controller. The switching controller has an input volt
-
age range of 7 – 40 V and a clock frequency of 52 kHz.
Power supply for
controlling the motor
This voltage is rectified via a bridge-connected rectifier and stabilized to
12 V using a linear voltage regulator.
Power supply for
the ECB interface
This voltage is rectified via a bridge-connected rectifier and stabilized to
5
V using a linear voltage regulator.
Potential equalization socket
The potential equilization socket is for connecting up an external ground
conductor. This socket is grounded.
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