A. Power supply.
1. Power supply.
1-1. Primary side:
1.1.1 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 IC101 using way of pulse width modulation.
The IC101 starts up through some components composed of R103, R104, R105, Q102 and ZD101to 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 C112.
1.1.2 R120, C108 and D113 composed a soft-start circuit to prevent over-stress occurred during power start.
1.1.3 The TP201: 75V voltage can be adjusted through VR101.
1.1.4 IC102, Q216, R204,R228 is 2W circuit in the power saving mode.
1-2. Secondary side
:
Each raw of DC voltage output from T101.
1.1.5 TP201 voltage output from T101 pin12 and is rectified by D202, C201.
1.1.6 TP202 voltage output from T101 pin11 and is rectified by D203, C202.
1.1.7 TP203 voltage output from T101 pin17 and is received by D205, C205.
1.1.8 TP204 voltage output from T101 pin18 and is rectified by D206, C206.
1.1.9 TP205 voltage output from TP203 is rectified by Q206, ZD201 and D208.
1.1.10 TP207 voltage output from TP204 and is rectified by Q210, ZD202 and D209.
1.1.11 TP209 voltage output from T101 pin10 and is rectified by D207, C207.
2. Power saving.
The EPA power management state as follows:
State SUS Pd Power consummation LED
Normal H H 100% Green
Power saving
L L
d 2W
Amber
SUS = IC301 (MCU) pin 21 output.
PD = IC301 (MCU) pin17 output.
In the power saving mode, no output from Q206 (12V) and Q208 (6.3V)
.
3. Degauss.
When the power is on and when press manual degauss, IC301 pin20 output high level voltage to turn on Q201, RL101 and
activate Degauss.
4. Rotation.
IC301 pin18 PWM to rotation circuit, Q211 and Q213 control flow of current of Rotation coil, when the bases of C215
Increase from 0 to 14V, as Q211 will turn on gradually, the current starts from 14V to 7V via Rotate coil.
When C215decrease from 14V to 0V, the current will change from 7V to GND.
4. Circuit Description
B. Micro (IC301).
1. HS/VS Processor.
HS/VS input pin41 (HS), pin42 (VS), IC301 individually to work on frequency, polarity, process of H+V and power
saving, then output horizontal sync (pin34) and vertical sync (pin33) of positive polarity to IC401 TDA9113 pin1, pin2.
2. PWM Control.
The PWM control of IC301 is pin29 (Brightness), pin19 (DAC ABL), and pin18 (Rotation), the PWM output via R,
C after rectified may
control each function
.
25
ViewSonic Corporation Confidential
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Do Not Copy 70f+SB-3E
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