Inhaltsverzeichnis
Werbung
GDV 100 D/002
Circuit description
Input circuit
The input circuit consists of a lightning protection circuit and an EMI
filter.
The lightning protection comprises R3120, gasarrestor 1125 and
R3124.
The EMI filter is formed by C2120, L5120, C2125 and C2126. It
prevents inflow of noises into/from the mains.
Primary rectifier/smoothing circuit
The AC input is rectified by rectifier bridge 6120 and smoothed into
C2121. The voltage over C2121 is approximately 300V. It can vary
from 100V to 390V.
Start circuit and V
supply
cc
This circuit is formed by R3123, R3134, C2129, D6129, R3129,
R3111, C2133 and C2111.
When the power plug is connected to the mains voltage, the stabilised
voltage over D6129 (24V) will charge C2133 via R3129. When the
voltage reaches 14.5V across C2111, the control circuit of IC7110 is
turned on and the regulation starts. During regulation, V
be supplied by the rectified voltage from winding 7-9 via R3135, D6132
and C2133.
Control circuit
The control circuit exists of IC7110 and its peripheral components. The
frequency of the oscillator is defined by C2102 and R3102.
Power switch circuit
This circuit comprises MOSFET T7125, R
R3128.
Regulation circuit
The regulation circuit comprises optocoupler 7200 which isolates the
error signal from the control IC on the primary side and a reference
component IC7201.
The KA431LZ (IC7201) can be represented by two components:
• a very stable and accurate reference diode
• a high gain amplifier
KA431LZ 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 optocoupler.
The collector current of the optocoupler flows through R3106, produc-
ing an error voltage, connected to pin 14 of IC7110.
Overvoltage protection circuit
This circuit consists of D6114, C2114, R3115 and R3116.
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 7-9. When an overvoltage
longer than 2.0 seconds is detected, the output is disabled until Vcc is
removed and then re-applied.
On/Off circuit
During Off mode pin 1 of connector 0206 is connected to pin 2, forcing
the opto-coupler 7200 to conduct. IC7110 is switched off and no supply
voltages are output.
Secondary rectifier/smoothing circuit
There are six rectifier/smoothing circuits on the secondary side. Each
voltage depends on the number of windings of the transformer.
The +5Vstby power supply is derived from the +12Vstby by voltage
regulator 7233, C2233 and L5233.
The -5V voltage is regulated by voltage regulator 7259 and will be
switched off via D6256, T7256 and T7255 during standby.
The +5V power supply is derived from +6Vstby by the loaderup circuit
formed by MOSFET 7236, reference component 7237, R3236, R3237
and C2239. This voltage will be switched off during standby via T7235.
The +3V3 power supply is regulated by the control loop (IC7201,
IC7200, IC7110) of the switched mode PSU.
Voltage regulator 7221 regulates the +2V9 power supply. This voltage
is used as filament voltage for the display. The output voltage during
standby is +1.5V.
GRUNDIG Service
of IC7110 will
cc
R3126, R3127 and
sense
K
R
+
2.5V
–
A
Keyboard Control Unit
IC7600
TMP87C874F: USER microprocessor
Function Overview
TMP87C874F is a high speed and high performance 8-bit single chip
microcomputer, containing 8-bit A/D conversion inputs and a VFT
(Vacuum Fluorescent Tube) driver.
In this application, it is used as USER microprocessor and as VFTD
driver. All the communication to the digital board runs via the Serial bus
interface (I
C).
2
7600
TMP87C874F
64
63
62
61
60
59
58
57
56
55
54
53
I/O PORT8 (VFT)
I/O PORT7 (VFT)
65
66
67
DATA MEMORY
PROGR MEMORY
68
( RAM )
512X8 BIT
69
70
C P U
71
72
73
16 BIT
INTERRUPT
74
TIMER/COUNTER
CONTROLLER
75
76
8 BIT A/D
CLOCK/TIMING CONTROLLER
77
CONVERT.
( I/O PORT2 )
78
VKK
79
80
I/O PORT0
1
2
3
4
5
6
7
8
9
10
11
12
Pin name
Function
INT0
external interrupt input 0
INT1
external interrupt input 1
RESETN
reset signal input, active low
SCL
I
2
C-bus serial clock input/output
SDA
I
2
C-bus serial data input/output
TEST
test pin, tied to low
VAREF
analog reference voltage input
VASS
analog reference ground
VDD
+5V
VKK
VFT driver power supply
VSS
ground
XIN, XOUT
resonator connecting pins for high-frequency clock
Description
52
51
50
49
48
47
46
45
44
43
42
41
I/O PORT6 (VFT)
VDD
VAREF
VASS
PROGRAM
( ROM )
COUNTER
8kX8 BIT
8 BIT
TIMER/COUNTER
I/O PORT1
I C 2
PORT3
13
14
15
16
17
18
19
20
21
22
23
24
2 - 9
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
Werbung
Inhaltsverzeichnis
