Power Unit; Power Control Circuit; Current Detector Circuit; Alarm Detector Circuit - Kenwood pds20-18 Service Manual

POWER UNIT (X68-1970)

Power Control Circuit

Q12 uses the control signals from the control unit
to control the current of the constant
circuit consisting of Q 13 and to driv e Q 11. Q 11
supplies the base current to Q1 to Q10.
The collector emitter voltage of Q 1 to Q 10 is
detected and supplied as the Vce voltage to the
secondary voltage detector circuit of the AC unit.

Current Detector Circuit

R46 detects the output current. IC
as shown in Table 1 and outputs amplifier current to
the control unit. The current is rev ersed by IC1
1/2 and used as the reference current for the slav e
side in the one control parallel operation mode.
Model Gain
20-18 33 time as high
36-10 33 time as high
60-6 36 time as high
Table 1
Bleeder Circuit
Two bleeder circuit are used : Input bleeder
circuit, and output bleeder circuit.
The input bleeder circuit has a constant
circuit consisting of Q17 and Q19. It bleeds current
as shown in Table 2. When the voltage exceeds
value shown in Table 2, Q14 functions and reduces
the bleeder to about half.
exceeds the output current shown in Table 2, the
comparator IC3 1/2 function and turns on Q 16 to
deactivate the bleeder circuit.
The output bleeder circuit has a constant current
circuit consisting of Q 20.
shown in Table 3. It is turned on or off by the
bleeder signal output by the control unit.
CIRCUIT DESCRIPTION
current
2/2 amplifier it
current
When the current
It bleeds current as
PDS20-18/PDS36-10/PDS60-6
Input side
Model
Bleeder current
20-18 About 1 A
36-10 About 1 A
60-6 About 0.5 A
Table 2
Model Output side Bleeder current
20-18 About 150 mA
36-10 About 80 mA
60-6 About 50 mA
Table 3

Alarm Detector Circuit

This unit employs three alarm detector circuits : Pre
overvoltage, overcurrent, and overheat detector
circuits.
The pre overvoltage detector circuit has a
comparator IC4 1/2, which compares the input
voltage. When the input voltage exceeds the level
shown in Table 4, the circuit outputs an alarm signal.
The overcurrent detector circuit has a comparator
IC4 2/2, which outputs an alarm signal when the
current detected by IC1 exceeds about 115% of the
full scale level. The IC4 2/2 also serves as an
error amplifier and provides CC control when the
output current reaches about 115% of the full scale.
The overheat detector circuit has a TS1
thermal switch on the heat sink. This
functions and circuit outputs an alarm signal when
the temperature exceeds about 110 .
Model Detection voltage
20-18 About 30V
36-10 About 50V
60-6 About 75V
Table 4
Switching
Off
Voltage
Current
About 20 V About 3.5 A
About 10 V About 3 A
About 30 V About 1.5 A
switch
7