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6. DC power operational descriptions
(1) General
When the specified AC input in applied to it, the power unit supplies 5
lines of DC outputs of +38V (VA), +24V (VB), +10V (VC), +5V (VD),
and –20V (VE), and pulse signal FW in synchronization with the AC
input.
It provides separately excited forward convertor outputs. The com-
position except for the partial smoothing section is the same as the
100V series and 200V series.
The block diagram of this power unit is shown below:
Connector
CN701
10
FW signal
output
8-1
Master output
detection error
amplification
Connector
(2) AC input section (Filter, etc.)
After the fuse F701, the input filters are provided in two stages of LC
filters. It reduces common mode noises and normal noises which
enter or invade from he AC line. The LC filter in the first stage is
composed of the across-the-line capacitor C701, the common mode
choke coil L703, and the line bypass capacitors C702 and C703.
The LC filter in the second stage is composed of the common mode
choke coil L704 and the across-the-line capacitor C704.
Fuse F701 is a protective element against an abnormal current in the
circuit.
3
3
2
Rectify
Partial
AC filter
-ing
smoothing
F701
A
100V series
5-1
Master output
detection error
amplification
8-2
Control section
12
Over current
protection
7
Transformer T702
9
9
Rectifying/
Rectifying/
smoothing
smoothing
(VD)
(VE)
+5V line
-20V line
CN702
The figure at left top corner of each block
shows the Item No. in the descriptions.
B
200V series
5-2
SW,IC
Z701
12
Over current
protection
6
7
Main switching
Rectifying/
smoothing
circuit
(+5V, -20V, +10V)
F704
F705
F707
9
F708
Rectifying/
smoothing
F709
(VC)
(VB)
+10V line
+24V line
(3) Rectifying/smoothing circuit
This circuit converts the AC input into a DC output (unstable state). It
is arranged in the sequence of rectifying and then partial smoothing.
Rectifying is performed by the diode bridge RC701, similar to the
100V series and 200V series. The partial smoothing section differs as
follows:
In the case of the 100V series, partial smoothing is performed by the
smoothing capacitors C707 ∼ C710, the diode bridge RC702, and the
thyristor CR701 to extend the conduction angle of the input current
(than the general capacitor input system), improving the power-factor.
The partial smoothing section is provided with the rush current
prevention function. When the AC power is turned on, the current limit
resistors R702 and R703 limits a rush current, and the smoothing
capacitor is charged. When the voltage reaches a certain level, the
separately excited convertor operates. The thyristor turns on through
the transformer T701 (between windings 5 and 6) and the gate output
to pass the limit resistor, preventing against heating in the limit resis-
tor in the steady state.
13 – 15
4
Main switching
circuit
4
Transformer T701
L707
6
Rectifying/
smoothing
F702
(VA)
+38V line
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