Circuit-, IC Descriptions and List of Abbreviations
9.
depends on the error voltage at the emittor of T7140, which can
be positive or negative (+/- 0,66V). The voltage fed back by the
regulation circuit defines this error voltage.
Power Switch Circuit
This circuit comprises MOSFET 7125, Rsense formed by
R3133, 3134, 3135, 3136 and 3137, R3131, R3132, D6146.
Diodes 6130, 6131 and 6132 protect the control circuit in case
of failure of the MOSFET.
Regulation Circuit
The regulation circuit comprises opto-coupler 7200, which
isolates the base voltage of transistor 7140 at the primary side
from a reference component 7251 at the secondary side. The
TL431(7251) can be represented by two components:
•
a very stable and accurate reference diode
•
a high gain amplifier
Figure 9-2
TL431 will conduct from cathode to anode when the reference
is higher than the internal reference voltage of about 2.5V. If the
reference voltage is lower, the cathode current is almost zero.
The cathode current flows through the LED of the opto-coupler.
The collector current of the opto-coupler will adjust the
feedback level of the error voltage at the emittor of T7140.
Overload Protection Circuit
This circuit consists of R3145, C2143, a thyristor circuit formed
by T7141 and T7143, R3143 and R3142. When the output is
shortened, the thyristor circuit will start to conduct and switch
off the supply voltage over C2140. This results in a switching of
f of the drain current of the MOSFET 7125 and the output will
be disabled. The start circuit will try to start up the power supply
again. If the circuit is still shortened, the complete start and stop
sequence will repeat. The power supply comes in a hiccup
mode (is ticking).
Overvoltage Protection Circuit
This circuit consists of R3149, D6144, 6143, R3144, C2142
and T7142.
When the regulation circuit is interrupted due to an error in the
control loop, the regulated output voltage will increase
(overvoltage). This overvoltage is sensed on the primary
winding 7-8.
When an overvoltage is detected, the circuit will start up the
thyristor circuit T7141-7143. The power supply will come in a
hiccup mode as long as the error in the control loop is present.
Secondary Rectifier/Smoothing Circuit
There are 6 rectifier/smoothing circuits on the secondary side.
Each voltage depends on the number of windings of the
transformer.
From these circuits a lot of voltages are derived and fed to 3
connectors. The following voltages are present at the output:
Connector 209
Functional use: to Digital board + Dvio board
1.
+3V3(for dig pcb + DVio)
2.
+3V3(for dig pcb + DVio)
3.
+3V3(for dig pcb + DVio)
4.
+3V3(for dig pcb + DVio)
5.
GND(for dig pcb + DVio)
6.
+12V(for dig pcb + DVio)
7.
GND(for dig pcb + DVio)
8.
GND(for dig pcb + DVio)
9.
+5V(for dig pcb + DVio)
10. STBY control(for dig pcb + DVio)
11. GND(for dig pcb + DVio)
12. -5V(for dig pcb + DVio)
The +12V is switched off by the STBY_ctrl signal.
When the +12V is switched off, also the +3V3, +5V and -5V are
switched off. All these voltages are low drop regulated.
Connector 0205
Functional use: to analogue board + display board + flap motor
‘STBY‘ indicates that the voltage will not be switched off in the
standby situation.
1.
+12VSTBY(= +12V Standby, for display heating, 8Vstby)
2.
+5VSTBY(= +5V Standby; general use)
3.
-5NSTBY(= -5V Standby; neg. voltage for drivers)
4.
VGNSTBY(= -32V Standby; for display grids)
5.
+33STBY(= +33V Standby; for tuner)
6.
FLYB(flyback pulse for power fail + measurement)
7.
GNDA(Ground for the analogue board)
Connector 0207
Functional use: to engine
1.
+3V3(for engine servo board)
2.
+5V(for engine servo board)
3.
GND(for engine servo board)
4.
+4V6E(for engine analog part)
5.
GND(for engine servo board)
6.
-5V(for engine servo board)
7.
GND(for engine motor currents)
8.
+12V(for engine motor currents)
9.2
Display Board
9.2.1
Operation Unit DC (DC Part)
The core element of the operation unit DC is the microcontroller
TMP88CU77ZF [7156]. The TMP88CU77ZF is an 8 bit
microcontroller fitted with 96kB ROM and 3kB RAM and is
responsible for following functions:
•
Integrated VFD driver
•
Timer
•
Evaluation of the keyboard matrix
•
Decoding the remote control commands from the infra-red
receiver pos. 6170
•
Activation of the display
•
Motor driver
The system clock is generated with the 12MHz quartz (Pos.
1153).
9.2.2
Evaluation of the Keyboard Matrix
There are 15 different keys on the display board. A resistor
network is used to generate a specific direct voltage value,
depending on the key pressed, via the resistors 3145, 3171,
3183 and 3194 on the analog/digital (A/D) ports (7156 Pin 17,
18, 19, 20). Pressing keys simultaneously may lead to
undesired functions!
9.2.3
IR Receiver and Signal Evaluation
The IR receiver [7140] contains a selectively controlled
amplifier as well as a photo-diode. The photo-diode changes
the received transmission (approx. 940nm) in electrical pulses,
which are then amplified and demodulated. On the output of
the IR receiver [7140], a pulse sequence with TTL-level, which
corresponds to the envelope curve of the received IR remote
control command, can be measured. This pulse sequence is
input into the controller for further signal evaluation via input
IRR [7156, pin 2].
A
2.5V
R
K
CL 96532065_071.eps
130799
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