Ac Unit; Line Filter; Main Power Control; Vce Start Controller - Kenwood pds20-18 Service Manual

AC UNIT (X68-1980)

Line Filter

This filter filtrates AC power and feeds filtrated
power to the primary side rectifier (B).
Main Power Primary Side Rectifier
Diode D4 in this rectifi er circ uit rect ifies AC voltag e
and s upp li es re ct if ied p owe r to th e ma in po we r
switching circuit (D).
Primary Side Current Detector
Th e pr im ar y si de A C cu rr en t is d et ec te d at t hi s
transformer (T3) and fed to the control IC (IC1).
Main Power Switching
This main powe r swi tchi ng ci rcuit use s Q 4 to Q 7
to switch AC voltage rectified by D4. Q4 to Q7 are
driven by Q 2 and Q 3 and controlled based on
signals output by IC1. The switching frequency is
about 135 kHz.

Main Power Control

The IC1-12(ON/OFF) terminal goes Low when the
mai n o utp ut po wer i s o ff. It g oes Hi gh wh en th e
main output power is on. Signals for controlling Q 2
and Q3 are output from the IC1-8 (OUT) terminal.
Triangular wave signals of the frequency decided
by R5 and C8 (about 135 kHz) are output from
IC1-15. IC1-3 (VDET) detects the Ac voltage. The
feed-back signal from PH3 for detecting the
secondary output Voltage is input to IC1-5. If IC1-
4 (OVP) is set to Low, IC1-8 (OUT) is also set to
Low and oscillation stops.
Primary Side Input voltage Detector
This detector uses R14, R15 and R19 to detect the
primary AC voltage a nd output s signals controlle d
by IC100, PH100 and Q101 to the control IC (IC1).
Main Power Secondary S i d e
Rectifier and Smoother
This ci rcu it r ect ifi es and smo oth es elec tri c p owe r
transmitted by the primary side to the secondary
side through the main transformers T1 and T2.
PDS20-18/PDS36-10/PDS60-6
CIRCUIT DESCRIPTION
Line Filter
This line filte r fil trate s DC volta ge ha ving passe d
throug h the seco ndary side recti fier a nd sm oothe r
circuit (G) before it is supplied to the power unit.
Overheat Protector
This overheat protector circuit detects the
temperature of the heat sink on which Q4 to Q7 and
D4, D10 and D11 are mounted. When the
temperature exceeds about 110 , it is short-circuit,
resulting in an alarm.
Secondary Voltage Detector
This c ircui t cont rols the se conda ry out put v oltag e
based on the Vce voltage supplied by the power
unit (X68-1970-0x) and causes PH2 and PH3 to
output signals for making the Vce voltage of Q 1 to
Q 10 of the power unit constant to the control IC
(IC1). Such control is turned on or off by the Vce
start controller block (K).

Vce Start Controller

This controller turns on or off the control for making
the Vce voltage constant using signals from the
control unit.
It turns off the control when the signal is set to High
or turns on the control when the signal is set to Low.
Table 5 below shows the Vce voltage of each type.
Model Vce voltage
20V About 3.5V
36V About 4.5V
60V About 4.5V
Table 5
10