Circuit Descriptions, List of Abbreviations, and IC Data Sheets
EN 46
L03.1U AA
9.
The L03 range consists of TV sets spanning from 14 to 21 inch
using the same chassis architecture. For the chassis
architecture, the CRTs used do not need East/West Correction.
Therefore the geometry correction needed is horizontal shift,
vertical slope, vertical amplitude, vertical S-correction, vertical
shift and vertical zoom for geometry corrections (with the
appropriate offsets required for NTSC channels on PAL sets).
9.7
Power Supply
For a detailed circuit description of this part, we refer to the
L01.2L AA manual (see the beginning of this chapter for the
ordering codes). Please note that there can be minor
differences in the text (e.g. other item numbers), but the
described circuit principle is comparable.
9.7.1
Introduction
The supply is a Switching Mode Power Supply (SMPS). The
frequency of operation varies with the circuit load. This 'Quasi-
Resonant Flyback' behavior has some important benefits
compared to a 'hard switching' fixed frequency Flyback
converter. The efficiency can be improved up to 90%, which
results in lower power consumption. Moreover, the supply runs
cooler and safety is enhanced.
The control IC in this power supply is the TEA1506 (L01=
TEA1507). Unlike the TEA1507 control IC, the TEA1506 has
no internal high voltage start-up source, and therefore needs to
be started by means of an external bleeder resistor (R3506 and
R3507). The operating voltage for the driver circuit is also taken
from the 'hot' side of this transformer.
The switching regulator IC 7520 starts switching the FET 'on'
and 'off', to control the current flow through the primary winding
of transformer 5520. The energy stored in the primary winding
during the 'on' time is delivered to the secondary windings
during the 'off' time.
The "MainSupply" line is the reference voltage for the power
supply. It is sampled by resistors 3543 and 3544 and fed to the
input of the regulator 7540 / 6540. This regulator drives the
feedback optocoupler 7515 to set the feedback control voltage
on pin 6 of 7520.
The power supply in the set is "on" any time AC power is
connected to the set.
9.7.2
Derived Voltages
The voltages supplied by the secondary windings of T5520 are:
•
"MainSupply" for the horizontal output.
•
"V_aux/V_audio" for the audio circuit.
•
An optional "DVD_Supply" for future extensions.
Other voltages are provided by the LOT. It supplies -12 V, the
tuner voltage, the filament voltage, and the +160 V source for
the video drive. These secondary voltages of the LOT are
monitored by the "EHT" lines.
9.8
Control
The microprocessor part of the UOC has the complete control
and CC/Teletext processing on board. The User menu's and
Service Default / Alignment Mode's are generated by the uP.
Communication to other ICs is done via the I2C-bus.
9.8.1
I2C-Bus
The main control system, which consists of the microprocessor
part of the UOC (7200), is linked to the external devices (Tuner,
NVM, Audio ICs, etc) by means of the I2C-bus. An internal I2C-
bus is used to control other signal processing functions, like
video processing, sound IF, vision IF, synchronization, etc.
9.8.2
User Interface
The chassis uses a remote control with RC5 protocol. The
incoming signal is connected to pin 67 of the UOC.
The keyboard, connected to UOC pin 8, can also control the
set. Button recognition is done via a voltage divider.
The front LED (6691) is connected to an output control line of
the microprocessor (pin 11). It is activated to provide the user
information about whether or not the set is working correctly
(e.g., responding to the remote control, normal operation (USA
only) or fault condition)
9.8.3
I/O Selection
For the control of the input and output selections, there are
three lines:
STATUS1
This signal provides information to the microprocessor on
whether a video signal is available on the SCART1 AV input
and output port (only for Europe). This signal is not connected
in LATAM/NAFTA sets.
STATUS2
This signal provides information to the microprocessor on
whether a video signal is available on the SCART2 AV input
and output port (only for Europe).
For sets with an SVHS input it provides the additional
information if a Y/C or CVBS source is present.
The presence of an external Y/C source makes this line 'high'
while a CVBS source makes the line 'low'.
SEL_AV1_AV2
This is the source select control signal from the
microprocessor. This control line is under user control or can
be activated by the other two control lines.
9.8.4
Power Supply Control
The Power Supply is interfaced with the microcontroller (UOC)
to provide the power supply with the control signals required for
burst mode operation in standby and to vary the picture width
by adjusting V_BAT.
The microprocessor part is supplied with 3.3 V and 8 V. The 3.3
V is derived from the "V_aux/V_audio" voltage via a 3V3
stabilizer (7493). The 8 V is derived from the 33V tuner voltage
via TS7491 and TS7496.
Two signals are used to control the power supply: STD_CON
and PW_ADJ.
STD_CON
This signal is generated by the microprocessor when over-
current takes place at the "Main" line. This is done to enable the
power supply into standby burst mode, and to enable this mode
during a protection.
This is of logic "high" (3.3 V) under normal operation of the TV.
When the TV set is in Standby (or fault) condition, this signal is
a continuous pulse of 5 ms "low" (0 V) and 5 ms "high".
Note:
In the L01 chassis this was inverted.
Figure 9-4 Block diagram of power supply interface with UOC
POWER SUPPLY
BLOCK WITH
TEA 1506
CONTROL IC
UOC
AC INPUT
Std_Con
+3V3
PW_ADJ
CL 36532044_039.eps
180603
