Philips L01.2A AB Service Manual page 55

Circuit Descriptions, Abbreviation List, and IC Data Sheets
Over Power Protection
During the primary stroke, the rectified AC input voltage is
measured by sensing the current drawn from pin 4 (DEM). This
current is dependent on the voltage on pin 9 of transformer
5520 and the value of R3522. The current information is used
to adjust the peak drain current, which is measured via pin
I .
SENSE
Short Winding Protection
If the 'sense' voltage on pin 5 exceeds the short winding
protection voltage (0.75 V), the converter will stop switching.
Once V drops below the UVLO level, capacitor C2521 will be
CC
recharged and the supply will start again. This cycle will be
repeated until the short circuit is removed (safe restart mode).
The short winding protection will also protect in case of a
secondary diode short circuit.
This protection circuit is activated after the leading edge
blanking time (LEB).
LEB time
The LEB (Leading Edge Blanking) time is an internally fixed
delay, preventing false triggering of the comparator due to
current spikes. This delay determines the minimum 'on' time of
the controller.
Over Temperature protection
When the junction temperature exceeds the thermal shutdown
temperature (typ. 140º C), the IC will disable the driver. When
the V voltage drops to UVLO, the V
CC
recharged to the V
(start)
the V voltage will drop again to the UVLO level (Safe-Restart
CC
mode). This mode will persist until the junction temperature
drops 8 degrees typically below the shutdown temperature.
Mains dependent operation enabling level
To prevent the supply from starting at a low input voltage, which
could cause audible noise, a mains detection is implemented
(Mlevel). This detection is provided via pin 8, that detects the
minimum start-up voltage between 60 and 100 V. As previous
mentioned, the controller is enabled between 60 and 100 V.
An additional advantage of this function is the protection
against a disconnected buffer capacitor (C
supply will not be able to start-up because the V
will not be charged to the start-up voltage.
9.7 Control
LED
IR
User
Interface
KEYBOARD/
(EW protection
Deflection
PANORAMA
16:9
Sound
VOLUME/
MUTE
Amplifier
TREBLE/Tilt
Processing
BASS
Tilt
BUZZ
PANORAMA
ITV-DATA-OUT
ITV
or
ITV-DATA-IN
Pip
ITV-CLOCK
RESET
Expansion
Slot
Figure 9-17
capacitor will be
CC
level. If the temperature is still too high,
). In this case, the
IN
capacitor
CC
Signal
internal I2C Bus
Processing
STATUS 1
STATUS 2
I/O
SEL-MAIN-FRNT-RR
uP - Control
POWER_DOWN
Power
Supply
STBY_CON
WRITE Enable
NVM
SEL-IF-LL/M-TRAP
Tuner / IF
I2C Bus
CL 16532016_015.eps
9.7.1 Introduction
The microprocessor part of the UOC, has the complete control
and teletext on board. User menu, Service Default Mode,
Service Alignment Mode and Customer Service Mode are
generated by the µP. Communication to other ICs is done via
2
the I C-bus.
2
9.7.2 I C-Bus
The main control system, which consists of the microprocessor
part of the UOC (7200), is linked to the external devices (tuner,
NVM, MSP, etc) by means of the I
is used to control other signal processing functions, like video
processing, sound IF, vision IF, synchronisation, etc.
9.7.3 User Interface
There are two control signals, called 'KEYBOARD_protn' and
'IR'. Users can interact either through the Remote Control
transmitter, or by activation of the appropriate keyboard
buttons.
The L01 uses a remote control with RC5 protocol. The
incoming signal is connected to pin 67 of the UOC.
The 'Top Control' keyboard, connected to UOC pin 80, 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 5). It is activated to provide the user
information about whether or not the set is working correctly
(e.g., responding to the remote control or fault condition)
9.7.4 Sound Interface
There are three control signals, called 'Volume_Mute',
'Treble_Buzzer_Hosp_app' and 'Bass_panorama'.
The 'Volume_Mute' line controls the sound level output of the
audio amplifier or to mute it in case of no video identification or
from user command. This line also controls the volume level
during set switch 'on' and 'off' (to prevent audio plop).
The 'Treble' and 'Bass' lines are used (in mono 4:3 sets) to
switch between different smart sound modes.
9.7.5 In- and Output 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 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-MAIN-FRNT-RR 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.
9.7.6 Power Supply Control
The microprocessor part is supplied with 3.3 V and 3.9 V both
derived from the 'MainAux' voltage via a 3V3 stabiliser (7560)
220301
and a diode.
Two signals are used to control the power supply:
• Stdby_con This signal is generated by the microprocessor
when over-current takes place at the 'MainAux' line. This is
L01.2A AB 9.
2
C-bus. An internal I
EN 55
2
C-bus