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CIRCUIT DESCRIPTION
1. MAIN POWER SOURCE
The AC input voltage is rectified by D1-D4, and the output
smoothed by the choke coils T2 and C1. The thyristors D1
and D2 are controlled in the phase control circuit. The rec-
tified voltage goes through the series control transistors
Q1-Qn and current detecting resistor R10, and is supplied
to the output
+OUT
terminal. The
—OUT
terminal goes
through D6 and returns to the recitification circuit.
2. REFERENCE VOLTAGE CIRCUIT
This circuit generates the control circuit power source and
a variable reference voltage for voltage and current (V,.,,
|). The AC voltage is recitified by D1 and, a constant
voltage of +15 V is generated in the constant voltage cir-
cuit which consists of Q1-Q8, U1 and D14.
The reference voltage of +15 V is generated by the zener
diode D14.,
—15V
is generated
by the
error
amplifier
U1
(1/2),
reference voltage (D14) and the dividing resistors R20 and
R21.
+15 V is generated by the error amplifier U1
(2/2) and
dividing resistors R9 and R10.
The GND of the +15
V is indicated by 4 V< on the circuit
diagram, and is connected
to the
+OUT
terminal.
The
power source of this differential amplifier U1 is supplied by
the zener diodes D6 and D9.
V.. is the variable reference voltage for constant voltage
control, and the V,., voltage (0-10 V) is output between
the rear terminals (3)-(5) from U3 (2/2), VR1 [VOLTAGE].
lL. is the variable reference voltage for constant
current
control, and the V,., voltage (0-10 V) is output to the rear
terminals (8)-(11) from U3 (1/2), VR2 [CURRENT].
3. VOLTAGE/CURRENT
CONTROL
CIRCUIT
(See Fig. 2)
With the floating type of voltage control, the control circuit
is controlled using the + OUT terminal as a reference GND.
The GND of the contro! power source +15 V (4V¢) is
therefore of equal potential to the
+ OUT terminal.
The
+ OUT terminal voltage and a voltage divided by the
voltage detecting resistors R42 and R43 are applied to the
voltage control feedback amplifier U4.
Both input terminals of U4 are operated to keep the same
potential.
The output from the feedback amplifier U4 goes through
D26,
is amplified by Q12
and Q13, passes through Q7
(Y86),
and drives the base
of the next
stage current
amplification circuit Q1-Qn.
The voltage at both ends of
the constant current detecting resistor R10 (0.025 ohms,
40 W) is used as a reference for the next constant current
operation.
This point is the GND during constant current operation, is
indicated by ¥l_ on the circuit diagram, and becomes the
reference point.
When the output current |, flows, the voltage produced in
the current detecting resistor R10 is applied to the control
amplifier U5. The voltage divided to I,.,; voltage feedback by
R45 and R46 is applied to U5.
When the voltage at both ends of R10 exceeds this divided
voltage (R45 and R46), U5 is operated to drive as the con-
stant current through D27.
The
output
from
U5
drives
Q1-Qn
(series
regulators)
through the same route as during constant voltage opera-
tion. When the current exceeds the constant current set-
ting value, the operation of the feedback amplifier circuit
U4 is simultaneously stopped, and the D26 route is inter-
rupted. Namely D26 and D27 are control OR circuits.
4. METER CIRCUIT
The voltmeter indicating circuit detects voltage from the
+OUT
terminal, which goes through U2 (2/2), the OVP
CHECK switch, U6 (1/2), the V/I CHECK switch, the OUT-
PUT ON/OFF switch, meter amp U7 (2/2) and is applied to
the voltmeter.
When V/I CHECK is on, the V,.,; voltage is applied directly to
the meter amp U7 (2/2).
The voltage detected by the current detecting resistor R10
for the ammeter circuit goes through the V/I CHECK switch
and is applied to the ammeter amp U7 (1/2).
During V/I CHECK, the I,., voltage is applied directly to the
meter amp U7 (1/2). Q1-Qn (series regulators) are controll-
ed by 010, Q12, Q13 (X73) and Q7 (Y86), by operating
the OUTPUT
ON/OFF
switch, to turn output voltage ON
and OFF.
5. OVP CIRCUIT AND OCP CIRCUIT
The D5 (zener diode) reference voltage that is divided with
VR1 and the +OUT terminal voltage divided by R3, Ré4 is
applied to the OVP voltage detecting comparator U1 (1/2).
When the output voltage exceeds the voltage setting of
VR1 (OVP setting VR), the output of U1 is inverted. The in-
verted
output
goes
through
D8,
Q1
and
D9,
drives
thyristor D10 and turns the breaker switch $1 OFF.
The reference (GND) of the OVP circuit is the same as the
+ OUT terminal V, of the voltage control circuit.
The detecting voltage generated by the current detecting
resistor R10
and the reference
voltage
of D28
(zener
diode) is applied to the OCP current detecting comparator
U6 (2/2).
If an excessive amount of current flows (overcurrent), the
output of U6 (2/2) is inverted, it goes through D7, Q1 and
D9 to drive the thyristor D10 and turns the breaker switch
$1 OFF.
Furthermore, the thermal relay provided on the heat sink to
prevent
overheating
of
the
series
regulator
transistor
detects abnormal
temperature
rise, and turns the breaker
switch S1 OFF through D6.
The OVP circuit, OCP circuit and overheating prevention
protective circuit drive the breaker switch S1 with the OR
7
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