Circuit Description - Kenwood KAC-X810D Service Manual

1. PWM Signal Waveform Generation
A and B are sent to the comparator so as to generate the
PWM waveform of C. (A clock of 50% in duty ratio is
obtained when B is 0.)
B A
0
C
0
A: Chopping wave
B: Analog input
C: PWM Signal
Chopping wave generator circuit
+10.3V +10.3V
R70
10K
C56
D10
1800P
IC8
8
(1/2)
C59
2
0.01
1
3
4
R58 C42 R78
33K 1u50 1K
+
Q6
Audio
signal
MUTE
SUMMING
AMP
Analog-fed back from
the output stage.

CIRCUIT DESCRIPTION

10.3V
R73
1.5K
A
11
9
7
8
IC9
10
(1/2)
IC9(2/2)
PWM WAVE
GEN CIRCUIT
IC9
IC8
(2/2)
6
(2/2) 5
R105
5 12
4.7K
7 4
6
3
C57 47P
R100 680K
R101 R107
68K 24K
B C
KAC-X810D/PS810D
The waveform of C is divided into upper and lower gate
waveforms. An OFF section is created so that the upper
gate waveform is not turned on simultaneously with the
lower gate waveform.
UP DOWN
Dead Time
The dead time is determined by
this time constant.
+5V
14
1
3 4
2 6 10
5
R84 10K 9
7
IC10
IC10
(1/4) D16
IC10
(2/4)
(3/4)
IC10
(4/4)
13
11 13
R85 12
12
10K
D17 IC11
(2/4)
DEAD TIME
GEN CIRCUIT
UP DOWN UP
+5V
D18
14
8
9
Upper gate
R118
8
10
1K
7
IC11
(1/4)
D19
VI CONV
Lower gate
R119
11
1K
5