Television – Receiver circuitry – Automatic frequency control
Reexamination Certificate
1999-01-19
2001-02-27
Peng, John K. (Department: 2714)
Television
Receiver circuitry
Automatic frequency control
C348S735000, C348S173000, C348S380000, C348S536000, C348S540000, C348S704000
Reexamination Certificate
active
06195134
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a horizontal electron-beam deflector, an automatic frequency controller (AFC), and a video signal receiver.
2. Description of the Related Art
First, the configuration of a general color television receiver will be explained.
FIG. 12
is a view of the configuration of a general color television receiver.
As shown in
FIG. 12
, a color television receiver comprises an antenna
2
, a station selector
3
, a video signal receiver
4
, an audio signal receiver
5
, a speaker
6
, a synchronization signal deflector
7
, a color signal reproducing portion
8
, and a color video display tube
9
.
In such a color television receiver, a signal of a desired channel is selected by the station selector
3
among television signals received by the antenna
2
, and an intermediate frequency (IF) signal S
3
is generated from the signal.
The intermediate frequency signal S
3
is amplified by an IF amplifier
41
in the video signal receiver
4
and divided into an audio intermediate frequency (IF) signal S
4
a
and a video intermediate frequency (IF) signal S
4
b
. The audio IF signal S
4
a
applied to the audio signal receiver
5
is detected therein and a television audio signal is extracted. Audio in accordance with the television audio signal is output from the speaker
6
.
In the video signal receiver
4
, the video IF signal S
4
b
is detected at a detector
42
and a complex video signal S
4
c
is extracted. The complex video signal S
4
c
is amplified by an amplifier
43
and output to the synchronization signal deflector
7
and the color signal reproducing portion
8
as a complex video signal S
4
d
. Also, the complex video signal S
4
c
is output to the color signal reproducing portion
8
as a luminance signal S
4
e
via a trap circuit and a delay circuit.
In the color signal reproducing portion
8
, a color signal is extracted from the complex video signal S
4
d
and the luminance signal S
4
e
, and three primary colors R (red), G (green), and B (blue) are generated and output to the color video display tube
9
.
The synchronization signal deflector
7
, as shown in
FIG. 13
, comprises a synchronization circuit
7
a
, a vertical deflection circuit
7
b
, and a horizontal deflection circuit
7
c
. In the synchronization circuit
7
a
, a vertical synchronization signal S
7
a
1
and a horizontal synchronization signal S
7
a
2
are extracted from the complex video signal S
4
d
and output respectively to the vertical deflection circuit
7
b
and the horizontal deflection circuit
7
c.
In the vertical deflection circuit
7
b
, a vertical deflection signal S
7
a
is generated and output to a vertical deflection coil
9
b
. As a result, in the color video display tube
9
, an electron beam emitted from a cathode is deflected in the vertical direction before reaching a fluorescent surface of the color video display tube
9
due to a magnetic field by the vertical deflection coil
9
b.
In the horizontal deflection circuit
7
c
, a horizontal deflection signal S
7
b
is generated and output to a horizontal deflection coil
9
a
. As a result, in the color video display tube
9
, an electron beam emitted from a cathode is deflected in the horizontal direction due to the magnetic field by the horizontal deflection coil
9
a.
There is known a color television receiver with a multiscanning function capable of receiving and displaying a television signal having a synchronization signal of a predetermined frequency range of, for example, 31 kHz to 60 kHz.
A synchronization signal deflector in such a color television receiver with such a multiscanning function has to detect the frequency of a synchronization signal included in the received television signal and control internal electronic circuits based on the results of the detection. The configuration of the synchronization signal deflector differs between a color television receiver with a multi scanning function and another without the function.
FIG. 14
is a view of the configuration of a horizontal deflecting circuit
7
c
of a color television receiver with a multiscanning function of the related art.
As shown in
FIG. 14
, the horizontal deflection circuit
7
c
comprises a computer
10
, an AFC circuit
11
, and a deflection circuit
12
.
The computer
10
detects a frequency of the input horizontal synchronization signal S
7
a
2
and outputs independent control signals S
10
a
and S
10
b
indicating the detected frequency to the deflection circuit
12
and the AFC circuit
11
respectively. In the computer
10
, the control signal S
10
a
and the control signal S
10
b
are synchronized for output.
Here, each bit of the control signal S
10
a
is used to respectively control the on/off operation of a corresponding switch built in the deflection circuit
12
due to the characteristics of the circuit configuration of the deflection circuit
12
, which will be explained below. Namely, the control signal S
10
a
is not decoded in the deflection circuit
12
.
The control signal S
10
b
is output to the AFC circuit
11
via a serial bus which is connected to a plurality of circuits, such as a control circuit for adjusting the brightness of a display, color tone, contour of image, and so fourth. Therefore, the control signal S
10
b
, in addition to a frequency of the horizontal synchronization signal S
7
a
2
, includes data and the like: to specify a circuit for outputting the control signal S
10
b
. The control signal S
10
b
is decoded in the AFC circuit
11
for use.
FIG. 15
is a view of the configuration of the AFC circuit
11
.
As shown in
FIG. 15
, the AFC circuit
11
comprises a register
21
, a current source
22
, an oscillation circuit
23
, and a wiring group
24
.
The register
21
is, for example, an 8-bit register which receives as input from the computer
10
an 8-bit control signal
10
b
indicating a frequency and stores bit data f
0
to f
7
. The register
21
outputs the stored control signal S
10
b
as a control signal S
21
via the 8-bit wiring group
24
to the current source
22
. Here, the wiring group
24
connects the 8-bit register with switches
26
a
to
26
h
, respectively.
The current source
22
comprises constant current sources
25
a
to
25
h
and the switches
26
a
to
26
h.
The constant current sources
25
a
,
25
b
,
25
c
,
25
d
,
25
e
,
25
f
,
25
g
, and
25
h
respectively output constant currents I, 2I, 4I, 8I, 16I, 32I, 64I, and 128I, where I indicates a unit current. One ends of the switches
26
a
,
26
b
,
26
c
,
26
d
,
26
e
,
26
f
,
26
g
, and
26
h
are connected to the oscillation circuit
23
and the other ends are respectively connected to the constant current sources
25
a
,
25
b
,
25
c
,
25
d
,
25
e
,
25
f
,
25
g
, and
25
h
. The switches
26
a
,
26
b
,
26
c
,
26
d
,
26
e
,
26
f
,
26
g
, and
26
h
are, for example, turned on the data f
0
, f
1
, f
2
, f
3
, f
4
, f
5
, f
6
, and f
7
are at a high level, that is “1”, and turned off when the data is at a low level, that is “0”. The current source
22
outputs a current i equivalent to a total summation of the constant currents output from the constant current sources
25
a
to
25
h
corresponding to the turned-on switches among the switches
26
a
to
26
h
to the oscillation circuit
23
. In the current source
22
, the constant currents 2I, 4I, 8I, 16I, 32I, 64I, and 128I are defined as powers of 2 of a reference constant current I, therefore the computer
10
generates the control signal S
10
b
of a digital value proportional to the frequency of the horizontal synchronization pulse signal S
11
.
The oscillation circuit
23
controls the frequency of an oscillation signal output from a built-in voltage-controlled oscillation circuit (VCO) by the current i from the current source
22
and phase-locks the oscillation signal to the horizontal synchronization signal S
7
a
to generate a timing signal. The oscillation circuit
23
generates a horizontal synchronization pulse signal S
11
by using a comparison signal S
12
corres
Nagamine Takatomo
Takahashi Shinji
Kananen Ronald P.
Natnael Paulos
Peng John K.
Rader Fishman & Grauer
Sony Corporation
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