Sanyo AAI-A Series Training Manual page 30

7. Double/Full-wave rectifier circuit
—
The rectifier circuit of this chassis is employed the double/full-wave rectifier switching circuit
to operate the power supply circuit in stability from 90V to 290V AC input.
The fig. 1 shows the double/full-wave rectifier switching circuit using the triac IC STR81145A,
IC501 .
The triac in the IC501 automatically switches on or off to build up the double or full-wave
rectifier circuit according to the input AC voltage level.
In the range from 90V to 145V AC input, the double rectifier circuit is build up by switching the
triac on in the IC501 as shown in fig.2.
During the positive half cycle of AC input, the current flows as follows; AC(plus)+ IC501 pin2
+ pin3 + C509 + D509 + AC(minus). The voltage is charged in C509. During the
negative half cycle, the current flows as follows; AC(minus)+ D508 + C508 + IC501 pin3 +
pin2 + AC(plus). The voltage is charged in C508. As a result, the DC voltage which is
double of AC input voltage is observed between the output terminals KG-1 and KG-2.
In the range from 145V to 290V AC input, the full-wave rectifier circuit is build up by switching
the triac off as shown in fig.3.
During the positive half cycle, the current flows as follows; AC(plus) + D506 + C508/C509 +
D509 + AC(minus), and the negative half cycle, AC(minus) + D508 + C508/C509 + D507
+ AC(plUS).
The voltage is charged in C508/C509. As a result, the DC voltage which is
same level of AC input voltage is observed between the output terminals KG-1 and KG-2.
This circuit can be supplied the proper DC voltage to the power oscillation circuit when the
AC input voltage varies in the range from 90V to 290V.
R508A
~ KG-1
, . ............................
:
Q
<
AC Input
SW501
D506
/u ~'
!Power ~
VAC
VDC c307~Oscilation j
:Circuit :
~KG-2 :
.............................
D501
2
N
3
1 )
R503
L
L:504 C507
4
IC501
STR81 145A
~
Main Unit
[5
:,,,.,.,,,,,,,...,.,,,,,,,,,,,,,,,,,,,,,,,,,,0, ,,,
Fig.1
@iz3–
Vi= VAC'@ V~c= 2*Vi
--
Vi= VAC'G VDC= Vi
+Fj;i
~ KG-1
Vi
, : 1
VACQ
*vivw=zw
<--------------------- -------------' -
J KG-2
'
C509
—
-- —-—-J IC501
I
2
/.
3
1
1 I
1 4
on
Fig.2 Double Rectifier& Smoothing Circuit
Fig.3 Full Waveform Rectifier& Smoothing Circuit
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AAI -A