User's Manual

B. HORIZONTAL DEFLECTION / VERTICAL DEFLECTION / EHT GENERATOR
HORIZONTAL DEFLECTION:
The heart of horizontal/vertical deflection controller is TDA4841, which can offer a complete and
efficient small signal sync processing for auto-sync monitors, all functions are controlled via I2C bus.
This controller provides sync processing, which can accept separate and composite (H+V) input signals,
a very short settling time after mode change for protection of external power components has been taken
into account.
The TDA4841 provides extensive functions like a flexible B+ controller block of H-deflection and a
geometry control with facilities, leading to excellent picture quality, this device also can directly drive the
vertical deflection output stage, the line driver stage, the E/W output stage and all controls are tracked
with the incoming frequencies, picture can be adjusted along horizontal direction by OSD H-shift control,
horizontal size, east/west, trapezoid corrections are obtained by varying the supply voltage of H-
deflection circuit via buck converter, five or six or seven capacitors plus power MOSFET switches and
DC controlled linearity coil are designed for optimal screen linearity.
VERTICAL DEFLECTION:
The majority of vertical deflection function is integrated by two ICs : TDA4841 and TDA8172.
The TDA4841 takes care of sync polarity correction, automatic catching and holding of the vertical
oscillator, generation of saw-tooth drive current for vertical output and vertical s-correction, and
generation of a correct V-blanking pulse for video blanking during vertical retrace lines.
The TDA8172 is a DC-coupled vertical deflection booster with differential input signals is suitable for
color monitor. The output stage has thermal and soar protection, and high linear saw-tooth signal
amplification to obtain the required vertical deflection current.
EHT GENERATOR
The combine circuit is used to generate required extra high voltage for CRT, the transformer
(LOT) transfers the voltage to required anode voltage and rest tertiary output voltage.
The adjustable focus (G3) and screen (G2) voltages are internally derived from the anode voltage, other
secondary windings are used to generate the voltages for G1, also provides dynamic focus on G4 to get a
good focus performance. (G4 is also adjustable).
For safety reasons, x-ray protection circuit is included, that TDA4841 will shut down EHT generator if
the anode voltage exceeds a certain value (29kV), this circuit is also used for over beam current
protection, it will shut down EHT in case the total beam current exceeds a certain value.