Table of Contents
Advertisement
4. Circuit Description
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（VC3843B）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
Normal
Active off
PD = IC301（MCU）pin17 output﹒
There is no output from Q206 and Q203 while is in Active off mode and PD（IC301 pin17）is 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﹒
ViewSonic Corporation
SUS
Pd
Power consummation
H
H
L
L
19
LED
100W
Green
≤ 4W
Amber
Confidential - Do Not Copy
G90f/B-3
Advertisement
Table of Contents
