Horizontal Deflection Block - Sony DTV-01 Manual

Horizontal Deflection Block

Both the horizontal driver and output stages have individual PWM stages
that supply regulated B+ voltage to them. The H. output B+ comes from
the PWM stage through the flyback.
This horizontal deflection block has several stages:
1. Horizontal Driver/Output stage feeds the FBT and H yoke.
2. Driver PWM stage controls the Driver transistor B+.
3. H. Output PWM stage controls the H. Output transistor B+.
4. Horizontal Centering stage positions the picture.
Horizontal Driver/Output stage
H o r iz o n t a l D r iv e r / O u t p u t s t a g e
S e c t io n s M a jo r p a r t s
D ig it a l D e f le c t io n I C 1 3 0 5
C o n t r o l I C
B u f f e r s I C 1 7 0 5 , Q 1 7 0 2 ,
Q 1 7 0 3 .
M O S F E T D r iv e r Q 4 0 1 1
H . O u t p u t Q 4 0 1 8
T r a n s is t o r
When the Digital Deflection Control IC1305 is powered, 31.5KHz horizon-
tal and 60Hz. vertical pulses are output. In this set the horizontal pulses
are buffered so there is sufficient current to supply the gate of the MOSFET
horizontal driver. The horizontal driver amplifies the drive signal. The sig-
nal is transformer coupled to the horizontal output transistor (Q4018). The
output transistor feeds the yoke for deflection and the flyback transformer
for high voltage.
Driver PWM stage
D r i v e r P W M s t a g e
S e c t io n s M a jo r p a r t s
S h a p e r I C 1 5 0 2 S h a p e s t h e H d r iv e p u ls e in t o a s in g le s p ik e .
D r iv e r Q 4 0 0 3 1 .
P W M
2 .
3 .
P u r p o s e
M a k e s h o r iz o n t a l d r iv e
s ig n a ls .
C u r r e n t t o v o lt a g e d r iv e r a n d
c u r r e n t lim it e r .
V o lt a g e a m p lif ie r
H ig h c u r r e n t o u t p u t d e v ic e
P u r p o s e
C h a n g e t h e s p ik e in t o a p u ls e ,
C o n t r o l t h e p u ls e w id t h ( P W M ) ,
F ilt e r t h e o u t p u t in t o D C .
89
The purpose of this stage is to:
1. Make B+ voltage for the driver MOSFET.
2. Regulate this voltage.
3. Increase the B+ voltage when a wide picture is called for.
Horizontal Output PWM stage
H o riz o n ta l. O u tp u t P W M s ta g e
S e c tio n s M a jo r p a rts
P u ls e IC 1 7 0 4 ,
w id th IC 1 7 0 5
C o n tro l
H O u tp u t Q 4 0 2 2
P W M
The pulse width control block makes a pulse that can be adjusted. At the
higher horizontal frequency, it is important that the horizontal output tran-
sistor be turned off before the next cycle. To insure this will take place, a
delayed pulse is used to lower the H. Output transistor's collector voltage
after turn on.
The H Output PWM block also adjusts the B+ voltage to compensate for
the slightly higher horizontal frequency used in HDTV reception.
Horizontal Centering stage
This stage only consists of three blocks. The Main Micro IC (not shown)
sends serial data to D/A converter, IC1702 to output a DC voltage. This
DC voltage is amplified by the H Center block, which applies it to the yoke.
This offset voltage is used to center the picture by keeping a constant
magnetic field in the yoke windings which positions the electron beam to
the left or right. The amount of shift is dependent upon the magnitude of
the voltage.
P u rp o s e
M a k e s a n o u tp u t p u ls e o f a fix e d w id th
re g a rd le s s o f th e in p u t fre q u e n c y .
D e la y s th e p u ls e a n d u s e s it to in s u re ra p id
H O u tp u t tra n s is to r tu rn o ff.
U s e s th e p u ls e to d e v e lo p B + fo r th e H .
O u tp u t tra n s is to r.
R e g u la te s th is B + v o lta g e to a s s u re s ta b le
p ic tu re w id th a n d b rig h tn e s s .
C h a n g e s th e B + s lig h tly to a d ju s t fo r a
d iffe re n t h o riz o n ta l fre q u e n c y .