ViewSonic VP2650WB - Page 27

ViewSonic Corporation
Confidential - Do Not Copy VP2650wb-1
24
C626
470P K
T65 1
390U
2
7 9
11
D655
LL4148
AK
+
C622
<Spec>
1U 100V
12
+
c605
<Spec >
150U 450V M
12
D651
1N5406
A K
ZD652
TZMC 24
AK
R655
10K
C621
0.01U K
E2
+
C624
2.2U K
10V
1 2
R664
3.01K F
A3
A4
+
C623
2.2U K
10V
1 2
A8 A9
E3
A10
Q653
2N7002K-T1-E3
D
G
S
R667
68K
R670
0.22
R669
1K J
R660
1M F
R661
1M F
R657
1M F
R658
1M F
R665
47
B+
R674
8.25K F
R671
499K F
R668
30
R659
20K F
C625
0.1U K
Q651
2SK3502
D
G
S
R663
205K F
R672
232K F
R673
232K F
R662
511K F
L6562N
IC 651
L6562N
VCC
8
MULT
3
COMP
2
GND
6
CS
4
INV
1
GD
7
ZCD
5
A1
E1
A2
R666
22.6K F
C628
1U
C620
1U K
D652
YG971S6R
A K
A-4.) PWM circuit introduction :
IC601 ( NCP1203) is the PWM control IC to get stable DC output. It can transfer high DC
voltage at primary to low DC voltage at secondary .
Pin 1. lets user adjutst the lavel at which the cycle skipping process takes place . Shorting this
pin to ground , permanently disables the skip cycle feature.
Pin 2. is connected to optocoupler , the peak current setpoint is adjusted accordingly to the
output power demand .
Pin 3. senses the primary current and routes it to the internal comparator .
Pin 4. is the IC ground .
Pin 5. is the driver’s output pin to an external MOSFET .
Pin 6. is Vcc pin and connected to an external bulk capacitor .
Pin 7. is empty and ensures adequate creepage distance .
Pin 8. is connected to the high-voltage rail , this pin injects a constant current into the Vcc bulk
capacitor .