ViewSonic A91f+-1, Руководство по обслуживанию

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1
﹒
POWER SUPPLY
﹒
1.1 Power supply
﹒
A
﹒
Primary Side
﹒
The raw DC voltage is built on C101 from AC line voltage through EMI filter
﹐
and bridge rectifier CR101
﹐
then
composes with main transformer
（
T101
）﹐
switching MOSFET
（
Q101
）
and PWM IC
（
IC101
）
to form a DC-DC
voltage converter by fly back switching topology, which means that the power energy is pumped up at primary
winding of transformer during duty “ON” cycle
﹐
then transfer the stored energy to primary side
﹐
and voltage
regulated by PWM IC
（
3842
）
using way of pulse width modulation
﹒
The IC101 starts up through some components composed of R103
﹐
R104
﹐
R105
﹐
Q102
﹐
ZD101 D110.R118.
R107 to build up VCC voltage at pin7
﹐
and supplied by transformer once secondary voltage is established
﹒
IC101 have to work synchronously with horizontal sync by feeding fly back pulse through C110
﹒
R124 .R125, C112 and D114 composed a soft-start circuit to prevent over-stress occurred during power start
﹒
The TP202
：
40V voltage can be adjusted through VR101
﹒
B
﹒
Secondary
﹒
Each raw of DC voltage output from T101
﹒
a
﹒
TP201 voltage output from T101 pin9 and is rectified by D202
﹐
C201
﹒
b
﹒
TP202 voltage output from T101 pin14 and is rectified by D203
﹐
D214. C202
﹒
c
﹒
TP203 voltage output from T101 pin15 and is received by D205
﹐
C205
﹒
d
﹒
TP204 voltage output from T101 pin16 and is rectified by D206
﹐
C206
﹒
e
﹒
TP205 voltage output from T101 Pin15 and is rectified by Q206
﹐
ZD201 and D208.C210.
﹒
f
﹒
TP206 voltage output from TP204 and is rectified by Q208.Q209.
﹐
R214. R215.and R213
﹒
g
﹒
TP207 voltage output from T204
﹒
and is rectified by Q210 ZD202 D209 R217.C211and C212.
1.2
Power saving
﹒
The EPA power management state as follows
：
State SUS Pd Power consummation LED
Normal H H 110W Green
Active off L L
≤
5W Amber
SUS
= IC301
（
MCU
）
pin17 output
﹒
PD = IC301
（
MCU
）
pin18 output
﹒
There is no output from Q206 and Q203 while is in Active off mode and SUS
（
IC301 pin17
）
and PD
（
IC301 pin18
）
are at low level voltage
﹒
That is, there is no output for 12V and 6.3V
﹒
1.3
Degauss
﹒
When the powers is on and when press manual degauss
﹐
IC301 pin20 output high level voltage to turn on
Q201
﹐
RL101 and activate Degauss
﹒
4. Circuit Description
19
ViewSonic Corporation
Co
nfidential - Do Not Copy A91f+-1