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c. Rectifying/smoothing circuit
In this circuit, he AC voltage (50/60Hz) is rectified by the rectifier
diode (D701) and smoothed by the smoothing capacitors (C707,
C708). The solid line and the dotted line in the figure below show the
flowing path of the charging current.
L701
SC-07-300J
(L)
CN701-1
(N)
CN701-2
3300P(KC)
Fig. 5 Rectifying/smoothing circuit
d. Invertor circuit (Forward convertor)
R704
R705
47(1W)
47(1W)
R703
1K
L70 2
BO1A
C709
L703
0.1/400V(QXJ)
BO1A
R709
C710
27K(2W)
470P/1KV(HR)
FIG.18
Q701
2SK1940
Q702
2SK1940
R710
27K(2W)
R707
0.1/5W
R708
0.1/5W
R717
R718
100(H)
100(H)
R721
10 K
Fig. 6 Invertor circuit
In the forward convertor system, the FET (Q701, Q702) connected in
series to the convertor transformer (T701) performs the ON/OFF
switching operation. When in ON, energy is supplied to the secondary
side through the convertor transformer. The DC current of the
smoothing circuit is converted into the switching pulses by switching
operation of the FET controlled by the single from the control circuit,
and a high frequency power is supplied to the secondary side.
The solid line in the figure shows the current when the FET is turned
on, and the dotted line shows the closed loop of the snubber circuit
which absorbs a counter electromotive force generated in the conver-
tor transformer.
TR701
BCR16PMBLAA
R703
1K
FA701
R702
3.3
3.3/135K
7W
D701
S15WB40
C706
C721
C722
L711
R732
1000P/1KV(HA)
B01A
33(2W)
2
T701
D702
L712
C-L00-284
N-T01-007
B01A
ERA9102
D717
ESAD92M03
R733
22(3W)
L713
L71 4
B01A
B01A
C727
L716
R734
B01A
33(2W)
C728
L717
B01A
D720
ESAD92M02
R735
33
(3W)
L71 8
B01A
Fig. 7 Invertor operation waveform
e. Secondary side rectifying/smoothing circuit (24V, 38V series)
The voltage of the high frequency pulses generated by the invertor
circuit is dropped by the convertor transformer (T701), rectified by the
diode, and smoothed by the choke coil (L715) and the electrolytic
capacitors (C725 in 38V series, C731 and C732 in 24V series).
L711
B01A
T701
L712
N-T01-007
B01A
L716
B01A
L717
B01A
ESAD92M02
Fig. 8 rectifying/smoothing circuit
f. Control circuit
This circuit employs the power MOS FET as the switching element
and the PWM control (Pulse Width Modulation) system by the primary
side control. Therefore, the output in the secondary side (24V series)
is detected by the output voltage detecting circuit, and the detected
signal is fed back to the control IC (IC701) through the photo coupler
(PC701) to change the pulse width of the switching FET in the
primary side invertor circuit, stabilizing the output voltage.
9 – 24
Q701(Q702)
Gate < > Source voltage (VGS)
0V
Q701(Q702)
Drain < > Source voltage (VDS)
0V
Q701(Q702) drain current (ID)
0A
C721
C722
R732
1000P/1KV(HA) 2
33(2W)
L715
C-L00-284
D717
ESAD92M03
C725
R733
22(3W)
2200(PF)
L713
L714
B01A
B01A
C727
R734
33(2W)
C728
D720
R735
33
(3W)
L718
L719
B01A
B01A
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