Philips L01.1E Service Manual Download Page 64

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Circuit Description

GB 64

L01.1E

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 are used (in mono 4:3 sets) to
switch between different smart sound modes. For other set
executions (e.g. stereo, widescreen), they 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

CL 16532016_015.eps

220301

Signal

Processing

User

Interface

uP - Control

LED

PANORAMA

BUZZ

BASS

TREBLE/Tilt