CIRCUIT OVERVIEW
3828VD0171G
3-1
DIGITAL FCS - CIRCUIT OVERVIEW
BASIC CIRCUIT THEORY
POWER SUPPLY DEFINITION
The Power Supply uses a COLD chassis
and is a single sided circuit board
that has been developed for screen sizes
27" through 32". The power supply fea-
tures two switch mode power regulators
for voltages sources. One is intended
for Standby sources and the other one
supplies the main switched voltages.
Both power supplies use direct regula-
tion. One error amplifier and one
optocoupler are used for each power
supply. This chassis also is Energy
Star compliant for low power consump-
tion in standby mode (less than 1 Watt
of consumption). This is the main rea-
son for the standby power supply.
SWITCH MODE REGULATOR
This chassis has two switching power
supplies (quasi-resonant topology type).
The AC line is routed through the fuse
FX3400 (5A @ 250 V slow blow) and then
through the bridge rectifier circuit
BRX3400 and CX3406 for the switched
power supply and through the bridge
rectifier circuit BRX3410 and CX3414
for the stand-by power supply. The AC
operation range is between 90 Vrms to
135 Vrms. A filter consisting of LX3400,
CX3402 and CX3403 is employed before
the rectifier circuits to reduce noise
from the AC line and vice versa (EMI).
STAND-BY START UP
The voltage output of rectifier BRX3410
(+V2 150VDC) is applied to the standby
SMPS which consists of ICX3612, ICX3700,
ICX3701, and the standby chopper trans-
former TX3612.
When the PIN 5 of ICX3612 terminal volt-
age reaches 17.5 VDC (typical), the
control circuit enables regulator op-
eration. Once the regulator output volt-
age is established, the drive winding
DX3601 starts to charge CX3605 via
DX3601. The voltage on CX3605 thus re-
covers to the nominal drive voltage.
SWITCHED POWER SUPPLY START UP
The voltage output of the rectifier
BRX3400 (+V1 150VDC) is supplied to
the Main Switch Mode Regulator Power
Supply (SMPS).
The Main SMPS consists of ICX3670,
ICX3750, and ICX3751. Its chopper trans-
former consists of TX3670.
When the PIN 4 of ICX3670 terminal volt-
age reaches 16 VDC (typical), the con-
trol circuit enables regulator opera-
tion. Once the regulator output volt-
age is established, the drive winding
DX3653 starts to charge CX3653 via
DX3653. The voltage on CX3653 thus re-
covers to the nominal drive voltage.
DEFLECTION AND HIGH VOLTAGE SECTION
The principal function of the Deflec-
tion and HV circuits is to supply hori-
zontal and vertical currents to the
deflection yoke coils, and the high
voltage generation. They are designed
for use in a single frequency televi-
sion. The new FCS converts the NTSC
horizontal scan 15.75KHz to 37.9 KHz
scan by means of a digital video pro-
cessor.
This section can be divided into 5 func-
tional blocks.
1. Horizontal Deflection and HV Gen-
eration
2. Base Drive
3. Pincushion Modulator Circuit
4. Shutdown Circuit
5. Vertical Deflection
Horizontal Deflection and HV Genera-
tion
The Horizontal Deflection circuitry is
a common flyback type used in many tele-
vision and monitor applications. QX3204
is the Horizontal Output Transistor.
When QX3204 is initially turned on,
current is allowed to flow from the B+
supply, through TX3201 and QX3204. This
allows energy to be stored in TX3201.