Lcd Display - Philips LC03E Service Manual

Circuit Descriptions, Abbreviation List, and IC Data Sheets
It is a self-resonant oscillator, where one transistor conducts
current while the opposite one does not, and vice versa. The
transformer core saturates in each half cycle, causing each
transistor to switch "on" or "off".
The energy required to operate the transistors as switches is
supplied by the feedback windings of the transformer to the
bases of the transistors.
The resistors R19 and R20 supply the base current for Q5 and
Q6. Capacitor C10/C11 and transformer T1 define the
oscillation frequency (working frequency). For the 15" model,
the working frequency lies around 45 kHz, for the 17" model,
this is about 47 kHz.
Example: If the primary voltage is 15 V_rms, and the
transformer turn ratio is 100, the secondary voltage is about 15
* 100 = 1500 V_rms.
9.10.5 HV Circuit
The High Voltage (HV) circuit supplies the power to drive the
lamps. The output voltage () is:
•
15" model: 520 V (with load), 1189 V (without load).
•
17" model: 609 V (with load), 1257 V (without load).
Note: Ensure that the backlight connectors are fully inserted, in
order to prevent high voltage arcing.
9.10.6 Balance Circuit
The Balance circuit uses an LCR resonant mode, to control the
output current. It delivers the same output current, even if the
load is different.
9.10.7 Feedback Circuit
The sense voltage of the feedback circuit is set at half the 5 V
supply voltage via R15 and R17 (at pin 9 of the comparator).
The control IC compares this voltage with the output current,
and regulates the PWM drive signal.
9.10.8 Protection Circuit
The protection circuit senses the output for current and for
abnormal signal behaviour, in order to protect the inverter:
•
Output current: It monitors the lamp current. If this current
is correct, the inverter will operate continuous. If the current
is incorrect, the inverter will be shut down. This means for
instance that if one lamp is not working, the inverter will go
into protection.
Note: Be sure that the lamp connectors are connected
properly.
•
Abnormal signals: It monitors the signals from the PWM
and Royer stage. If anything is wrong, the protection circuit
will shutdown the inverter.
LC03E

9.11 LCD Display

9.11.1 Specifications
Panel model
Resolution (HxV)
Luminance
Contrast ratio
Supplier
9. EN 111
: LC151X01-C3P1
(15")
: LM171W01-B3 (17")
: LC230W01-A2 (23")
: 1024x768 pixels (15")
: 1280x768 pixels (17")
: 1280x768 pixels (23")
: 400 nit (15")
: 400 nit (17")
: 450 nit (23")
: 350 (15")
: 350 (17")
: 400 (23")
: LG.Philips LCD