Kenwood KDC-V7521/Y, Руководство по обслуживанию

Страница: 10 / 23

10
KDC-V7521/Y
Using a DAC that can be varied in 256 steps between 0V
and 5V and varying DAC output voltage, the currents that flow
among R7, R9 and R11 are controlled. As a result, the bright-
ness of red, blue and green is adjusted.
Description of Operation
The voltage output from DAC will be in the step-wise wave-
form as shown in A .
When the output voltage is put through R1-3 and C1-3 low-
pass filters for removing noise and smoothing voltage wave-
forms, we get the voltage waveform of B .
The voltage that went through the low-pass filters is input
to the buffer and that will be the input voltage of the V-I con-
verter in the next stage with the voltage waveform of C .
The V-I converter has the function of supplying electric cur-
rent in proportion to the voltage input.
For example, let us assume that the current flowing in the
red LED is IR, and IR = (Q4 base voltage-VBE) /R7.
From this, IR flows in proportion to Q4 base voltage.
Therefore, V-I converter will supply current in proportion to
the voltage input to red, blue and green LED's, which vary the
brightness of LED's.
The registor between D1 and V-I converter is the protection
registor for limiting power supplied to transistors (Q4-6).
CIRCUIT DESCRIPTION/ATTENTION
R1
1
R7 R9
R4 R6 R5
4.7 4.7 4.7
C1 C3 C2
VCC
SDA
A
8
7
AO2
AO1
1
2
IC1
SCA
6
AO3
3
GND
5
NC
4
(BOTTOM VIEW)
Q4
Q5
Q6
Q1
Q2
Q3
100k
100k
100k
100k 100k 100k
470 470 270
R12 R8 R10
150 150 220
(B)
(G)
(R)
PAN5V
GND
SDA
SCL
LOW PASS FILTER
DAC
BUFFER
ILL+B
V-I CONVERTER
R1
R2
R3
D1
A B
C
V V V
T T T
: DAC OUT B : BUFFER INPUT C : V-I CONVERTER INPUT
R G B
PROTECTION
RESISTOR
ATTENTION
Assembly pf FPC (Flexible PC board) onto Roller ass’y
Turn Roller ass’y by 2 times.
Hook the end of Roller ass’y to the tongue.
Insert the FPC into the slit of Roller ass’y then release the end of Roller ass’y and the tongue.
tongue
Turn 2 times.
End of Roller ass’y
FPC
Variable Illumination Circuit