Philips L01.2E AB Service Manual Download

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Circuit Description

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

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

capacitor will be

recharged to the V

(start)

level. If the temperature is still too high,

the V

voltage will drop again to the UVLO level (Safe-Restart

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

). In this case, the

supply will not be able to start-up because the V

capacitor

will not be charged to the start-up voltage.

9.7

Control

Figure 9-17

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

P. Communication to other ICs is done via

the I

C-bus.

9.7.2

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

C-bus. An internal I

C-bus

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 ‘KEYBOARD_protn’ line, also serves to detect faults in the
E/W circuit, which would require the

P to shut down the set (by

forcing the power supply in standby mode).

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 have another functionality:
–

The ‘Bass_panorama’ line is used to switch the panorama
mode in widescreen sets (to fit 4:3 pictures into a 16:9
display, it is possible to apply a panoramic horizontal
distortion, to make a screen-fitting picture without black
sidebars or lost video).

–

The ‘Treble_Buzzer_Hosp_app’ is used in ITV applications
for other feautures, and in widescreen sets to enable the
‘Tilt’ feature (via R3172 on diagram A8) in the deflection
part.

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.
–

0 to 2 V: INTERNAL 4:3

–

4.5 to 7 V: EXTERNAL 16:9

–

9.5 to 12 V: EXTERNAL 4:3

•

STATUS2

This signal provides information to the

microprocessor on whether a video signal is available on
the SCART2 AV input and output port (signal is low). For
sets with an SVHS input, it provides the additional
information if a Y/C or CVBS source is present (signal is
high). The presence of an external Y/C source makes this
line ‘high’ while a CVBS source makes the line ‘low’.
–

0 to 2 V: INTERNAL 4:3

–

4.5 to 7 V: EXTERNAL 16:9

CL 16532016_015.eps

220301

Signal

Processing

User

Interface

uP - Control

LED

PANORAMA