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2-3. SMPS BASIC OPERATING DESCRIPTION
1) Power supply block circuit
F801
AC 125V 4A
PWC1
Z801
SVC2710
VARISTOR
R804
2.2M(COMP)
1/2W
2) Initial Operating Conditions
– When AC voltage is applied at PWC1, the bridge rectifier converts the output voltage to DC and is filtered by C806.
– This voltage is applied to pin 9(V in term.) of I801, through R806 thus starting the operation of I801.
– After C807 charges up to approx. 8V through series resistance R806, then the CTRL circuit starts operating.
– The time constant created by R806 and C807 determines the time delay before the CTRL circuit operation begins
after the AC power is applied. Therefore if the value of C807 is high, it could delay the starting of I801 circuit.
– CTRL circuit operation begins when drive(oscillation) at pin 3 of T801, forward biases D808 and charges C807.
– When the voltage increases at pin 4 of T801, this forward biases D807 and charges C809. When the voltage across
C809 turns off the power to T810.
– This results in the energy stored in the primary being induced into the secondary circuit.
D802-D805
:1S1888
C801
D803
D805
O.1U(M)
L801
C803
C805
AC250V
TLF-472BE
D802
D804
C802
C804
Vin
1
1
START UP
PRE REA
7
SENSE
T.S.D
R1
C802-C805
4700P 500V
R812
R803
120K
1 OHM 7W
1/2W
CEMENT
C806
330U(LWF)
200V
R806
36K
2W
R813
100K
1/4W
C809
C807
10U
220U
100V
25V
1801
STR-S5707
DR
4
R807
18 1W
PROPORTION
S
DVP LATCM
ORIVE
4
C808
220U
B
OCP
25V
3
DSC
D810
C
BYV950
REF
1
E
2
OCP
C1
3
C3
C2 R2 C4
6
R832
240(*200)
R809
1/4W
0.27(F)
2W
41
T810
TSM-4242A3
8
9
7
10
123V
6
11
15V
5
12
D807
BYW95C
BYV95C
4
13
D808
BYV95C
15V
14
3
R819
2.2
1/4W
8.5V
2
15
R833
4.7K
1
16
1/4W
D809
BYV95C
L803
R815
MD-5
1.8K
1/4W
C823
3900P
630VPL
C824
4700P
R816
C822
AC400V
1K
1500P
1/4W
50V
C827
1000P(HIKR)
2KV
C815
100U
160V
D814
BYW95C
C814
C828
D813
470U
0.01U
25V
D812
C812
BYV95C
470U
25V
C810
D811
470U
BYV95C
16V
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