Start-Up And Oscillation Circuit; 3-7-3 - Sony Multiscan GDM-2036S Service Manual

· GDM-2036S
@
Rect switching circuit
When the voltage is below approx. AC ISOV, the triac in
ICI (STR80l4SA) is turned on and the AC rectification
becomes the double-voltage rectifier circuit. In the AC
200V system, the triac is turned off and the AC
rectification becomes the bridge rectifier circuit.
Hereafter Rect. Out voltage is referred to as Ei.
3·7·2. Start·up and oscillation circuit
ICIOI peripheral circuit
RIO
...-_III'r-
+8
Fig. 3-5.
When the Ei starts up, the power is supplied to ICI02 (Low B
system OSC) on the GA board through RS, THP2 and the
series regulator QS on the G board, which it starts to oscillate.
Due to this oscillation, the voltage caused at T3 (SRT -2) is
rectified and smoothed by DI7 and CI9, reaching to ISV Vcc.
When the V cc is completely started up QS gets cut off. Also,
Vcc is supplied to ICIOI of the +B system OSC.
IC202 is the variable shunt regulator (TL431). It controls VC
to regulate VB to 2.5V. In this case, by the increasing of +B,
the current
t
is absorbed and the frequency is lowered with
pin
®
electric potential of IClOi being
IClOi and IClO2 (IR3M02) are the PWM controller,
equivalent to TL494, which are used as the frequency
controller by varying the time constant.
increased via IC8.
3·7·3. Converter section
V GSI
101
V OSI
VGS2
102
VOS2
- 101
- I 02
III
I L2
Principle of operation
Current resonance SEPP
IL I
Ei
SRT--!L2
Irrr...... -
C:--f~
-t __________
L . . . I _ _ _ _
----IL ________
L - I _ _ _
JCJ
Q~i----
] 1------------
-J
L _____ _
I
I
,
:
J _ _ _ _ _ _
~
______
L--!_i
--!--+-~I----L--L~I---
i : : :
~
~
i
~.~:--4----
I I I •
I I
~------1J.:--~----~;----~-4--------
:~;
I
I I I
I I I
I I :
I I
I I
I I
I
I
Fig. 3-6.
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