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EN 122
9.
EM5A P/M
If the load continues to increase, the regulator will block at a
certain moment. T
is now at maximum value. This is the point
ON
where V
will go below 141 V and, at further increasing load,
BAT
is switched "off". The voltage across the co-coupled coil
(L5506, pin 4 and 5) will decrease, due to the increasing load.
Therefore, the voltage on the gate of TS7504 comes below the
threshold voltage. The supply switches "off", and an audible
hiccupping can be heard.
On the other hand when the load decreases, V
Consequently, the input voltage of TS7506 will also rise,
resulting in a higher current. This changes the base voltage of
TS7502, and through that the T
The output voltage V
BAT
If, for instance, V
will decrease (e.g. U
IN
V), the slope of the drain-current will be flattened, through
which the FET will be longer into conductance, keeping V
constant.
If, for any reason, the stabilisation circuit might fail, the output
voltage V
can never exceed 200 V (via D6514). D6514 will
BAT
form a short-circuit, V
BAT
(this will also result in an audible hiccupping of the supply).
Switch to "Standby" (via RC)
When the set is switched to "Standby" mode via the Remote
Control, the Main supply is switched "off" by the circuit around
TS7529 (see diagram A1).
During "on"-state, the Main supply is fed with line pulses via the
'SUP-ENABLE' line. They are rectified and smoothed via
D6517, D6516, and C2530, and fed to TS7529. Because they
are less than -20 V, this transistor is blocked. When these
pulses are stopped, TS7529 will be saturated and TS7502 will
switch "on". This will switch "off" the Main supply.
It is important, that the Main supply is switched "off" before the
Standby supply. This in order to prevent several unwanted
phenomena, such as audible plops and visible switch off spots.
Without an extra circuit to force this, this cannot be achieved.
Therefore, the circuit around TS7505 and TS7508 is
implemented.
This circuit compares the Main DC voltage (+375 V) and a
reference voltage (V
BAT
and R3556. Elcap C2539 serves as voltage source for the two
transistors.
When the Main DC voltage will decrease w.r.t. the reference
voltage V
, the 'SUP_ENABLE' line will be activated via
BAT
TS7505, TS7508 and R3559. This will switch "off" the Main
supply via TS7529.
Set to "On" (via 'SUP-ENABLE')
Via the 'STANDBY' command from the OTC, the MOSFETS
7141 and 7131 (diagram A2) are switched "on". When the +5V
and +8V are sensed by the OTC, a command is given to the
HOP to start the drive (via I
When this is sensed via the 'SUP-ENABLE' line (at the base of
line transistor TS7421, diagram A3), the main supply is
switched "on" via TS7529 (diagram A1).
Protection
When, for any reason (interruptions or defective components),
the feedback loop of the Main supply will fail, the V
This is detected via zener diodes D6507, D6508, and D6513.
This will "ignite" thyristor T7503, which will result in the blowing
of fuse 1503.
Audio Supply
The pulses on the secondary winding of L5506 (or L5512) are
rectified by D6535 (+16 V) and D6536 (-16V), and smoothed by
C2542 and C2543.
Circuit Descriptions and Abbreviation List
will rise.
BAT
of the FET will decrease.
ON
will be reduced.
is 180 V i.s.o. 240
MAINS
will drop and the set will switch "off"
) via resistors R3554, R3555, R3560,
2
C).
will rise.
BAT
9.4
Control (Diagram B5)
A0...A19
FLASH
FLASH
DRAM
(SW)
EPG
(TXT)
CVBS-TXT
H, V
+3V3
+5V2
+3V3 +
RESET
OUT
+3V3
KEYBOARD
+5V
+8V
TUNER
WIRELESS EXPANDER
WIRELESS TRANSMITTER
3D COMBFILTER
DVD INTERFACE EXPANDER
DVD ENGINE
MOIRÉ EXPANDER
AUTOSCAVEM DAC
PIP I/O EXPANDER
BOCMA PIP
SfH I/O EXPANDER
Vchip PIP
Figure 9-10 Microprocessor (OTC)
9.4.1
OTC
Introduction
The SAA5801 (IC7001) is called the OTC (OSD, TXT, and
Control). In this IC, the microprocessor and the TXT-decoder
(level 2.5) are integrated.
Some of its functions are:
•
Set control.
•
TXT/OSD acquisition.
•
RGB-outputs to the HOP
•
Menu blending; for blending the contrast, software
controlled.
•
I/O-ports for I
•
Error code generation.
Data Storage
•
The software for EM5A can be 2 MB (Megabyte), and is
stored in IC7006.
•
It is possible to store 1200 TXT pages in IC7007. This is a
DRAM of 4 MBit and this IC is also used to store data of a
working set.
•
The Non Volatile Memory IC7011 is a 4 kB version
M24C32W6.
Power Supply
All ICs in this part are supplied with 3V3. For this voltage, a 3V3
stabiliser is used (IC7005).
With the circuitry around TS7003 and 7004 (diagram B5), a
reset is generated to wake up the OTC (pin 74). During this
reset, all I/O pins of the OTC are made "high".
Via pins 105 and 106, the +8 V and the +5 V are sensed. If one
of them is not present, the Main supply is switched "off" (set in
protection and the red LED will blink at 3 Hz).
7001
D0...D15
P50-OUT
120
NVM
SAM
(PROG)
119
+3V3
SEL_IN_2
117
SAA5801
DEGAUSSING
115
LIGHT SENSOR
5
110
STATUS SC3
109
FRONT DETECT
83,84
108
STANDBY
RESET
104
74
SEL_IN_1
103
RC5/RC6
100
ON/OFF-LED
113
POR
99
P50-IN
97
SDM
107
96
SOUND ENABLE
106
95
RESET AUDIO
105
94
I 2 C1
slow
FRAME
85/86
81
RGB, BLENDING
77,78,79,80
I 2 C2
fast
87/88
I 2 C3
91/92
2
C, RC5/RC6, LED, and service modes.
4005
4006
HIP
HOP
MSP
FBX
TOPIC
NVM
CL 26532041_063.eps
110402
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