JP2002319847A - Channel selection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a channel selection system for a television receiver provided with a tuner of the frequency synthesizer system, that can activate the tuner at a proper local oscillating frequency even when the characteristic of an AFT(Automatic Frequency Tuning) circuit is affected with temperature fluctuations and a change over time or when the adjustment of a coil in the AFT circuit causes a deviation from a prescribed value. SOLUTION: When a difference Δf between a local oscillating frequency f0 corresponding to a standard broadcast frequency and a local oscillating frequency f0' obtained by activating the AFT circuit 10 is smaller than a prescribed value fB, the channel selection system stops the operation of the AFT circuit 10 so as to operate the tuner 3 at the local oscillating frequency f0 corresponding to the standard.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel selection system for a television receiver.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of a television receiver including a conventional tuning system, FIG. 8 is a flowchart showing the operation of the tuning system, and FIG. S curve diagram (intermediate frequency signal (I
FIG. 4 is a curve diagram showing characteristics of an output voltage (AFT output voltage) of the automatic frequency adjustment circuit with respect to a frequency of an F signal.

As shown in FIG. 7, this television receiver selects an antenna 2 for receiving a broadcast signal, and a broadcast signal of a predetermined channel from a plurality of broadcast signals received by the antenna 2, and selects the broadcast signal. A tuner 3 for outputting an intermediate frequency signal corresponding to the signal, a video intermediate frequency amplifying circuit 4 for amplifying the intermediate frequency signal output from the tuner 3, and an intermediate frequency signal amplified by the video intermediate frequency amplifying circuit 4. Detection circuit 5 that performs a detection process to obtain a video signal of a selected channel, a video amplification circuit 6 that amplifies a video signal output from the video detection circuit 5, and a video amplification circuit 6
A cathode ray tube (CRT) 7 for displaying an image represented by a video signal output from the camera, a control unit 8 for controlling the overall operation, and a signal for allowing a user to operate the image display machine. Key operation unit 9.

[0006] The tuning operation of the tuner 3 is controlled by a local oscillation frequency control signal LV provided from a control unit 8 based on a user operation of a key operation unit 9.

[0005] The video intermediate frequency amplification circuit 4 includes an automatic frequency adjustment (AFT) circuit 10. This AFT circuit 10
Receives an image intermediate frequency signal and generates an AFT signal. The control unit 8 adjusts the local oscillation frequency control signal LV based on the AFT signal.

[0006] The tuner 3 is a tuner of a frequency synthesizer (hereinafter abbreviated as FS) system. The frequency synthesizer type tuner includes a local oscillation circuit having a PLL (Phase Locked Loop) and the like, and is a method of directly controlling the local oscillation frequency by externally designated frequency data. Since the predetermined frequency is maintained, there is a feature that the tuning accuracy is high, that is, the frequency accuracy is high.

Hereinafter, the operation of the control unit 8 at the time of channel selection will be described with reference to FIG. When a tuning instruction is issued from the key operation unit 9, the control unit 8 performs tuning according to the flowchart of FIG. First, the control unit 8 outputs a signal designating the local oscillation frequency f0 corresponding to the broadcast frequency defined in the broadcast standard (S1), and changes the value of the data designating the local oscillation frequency up and down (S2). , The local oscillation frequency specified thereby is changed up and down around the standard value f0,
As a result, data of an S curve as shown in FIG. 9 is obtained,
When the frequency is gradually increased, the frequency fA at which the AFT voltage falls below the predetermined value TH is found for the first time (S3). Thereafter, this frequency f0 'is supplied to the tuner 3 as a local oscillation frequency (S5). This completes the channel selection.

If the broadcast frequency (video carrier frequency) of the received television signal is as defined in the broadcast standard (f0), f0 'matches f0. If the broadcast frequency of the received television signal is a value f0 'that deviates from the frequency defined by the broadcast standard (f0), tuning can be performed by setting the local oscillation frequency to f0'. it can. By appropriately selecting a channel as described above, the channel can be reliably selected even if the broadcast frequency of the received television signal deviates from the broadcast standard. When the frequency fA is not found (when the AFT voltage does not fall below the value TH even if the local oscillation frequency is increased), the operation is stopped with the local oscillation frequency set to f0.

[0009]

In the above-described conventional channel selection system, when the S-curve characteristic of the AFT circuit 10 is affected by a temperature change or a change with time, adjustment of a coil in the AFT circuit 10 is performed. Is deviated from the prescribed value, there is a problem that the frequency accuracy inherent in the frequency synthesizer cannot be exhibited due to these effects.

The present invention has been made in order to solve the above-mentioned problems, and has been made in the case where the S-curve characteristic of the AFT circuit 10 is affected by a temperature change or a change with time,
Even when the adjustment of the coil in the T circuit 10 deviates from the prescribed value, if the broadcast frequency of the received television signal is in accordance with the broadcast standard, tuning can be performed with the frequency accuracy of the frequency synthesizer. An object of the present invention is to provide a television receiver.

[0011]

According to the present invention, there is provided a tuning system for a television receiver, comprising: a tuner (3) of a frequency synthesizer type for receiving a received television signal and generating a video intermediate frequency signal; An automatic frequency adjusting circuit (10) for generating an AFT signal in response to the video intermediate frequency signal output from (3), and receiving an AFT signal from the automatic frequency adjusting circuit (10) and causing the tuner (3) to perform local oscillation A control unit for providing a frequency control signal (8)
The control unit (8) has a local oscillation frequency value (f0 ′) obtained by operating the automatic frequency adjustment circuit (10) and a broadcast frequency defined by a broadcast standard. (F0) of the local oscillation frequency (Δ
f), and when the difference (Δf) is within a predetermined range (fB), a local oscillation frequency control signal designating a local oscillation frequency value (f0) corresponding to a broadcast frequency defined by the broadcast standard Is given to the tuner (3).

The control unit obtains the difference at the time of setting the channel of each channel, and if the difference is within the range, thereafter, when receiving the broadcast of the channel,
The automatic frequency adjustment circuit may not be operated.

The control section calculates the difference when selecting a channel for the first time after the main power is turned on. If the difference is within the range, the same channel is used until the next main power is turned off. , The automatic frequency adjustment circuit may not be operated.

The control unit obtains the difference at the time of automatic channel selection of the broadcast of each channel, and operates the automatic frequency adjustment circuit when receiving the broadcast of the channel if the difference is within the range. It is good not to let it.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments. Embodiment 1 FIG. The channel selection system of the present embodiment has a configuration similar to that shown in FIG. That is, the television receiver of the present embodiment selects an antenna 2 for receiving a broadcast signal, and a broadcast signal of a predetermined channel from a plurality of broadcast signals received by the antenna 2, and corresponds to the broadcast signal. A tuner 3 for outputting an intermediate frequency signal, a video intermediate frequency amplifying circuit 4 for amplifying the intermediate frequency signal output from the tuner 3, and a detection process for the intermediate frequency signal amplified by the video intermediate frequency amplifying circuit 4 A video detection circuit 5 for obtaining a video signal of the selected channel, a video amplification circuit 6 for amplifying a video signal output from the video detection circuit 5, and a video signal output from the video amplification circuit 6 Cathode ray tube (CRT) 7 for displaying an image to be displayed, a control unit 8 for controlling the entire operation, and a key operation unit for inputting a signal for a user to operate the image display machine With the door.

The tuning operation of the tuner 3 is controlled by a local oscillation frequency control signal LV supplied from the control unit 8 based on the operation of the key operation unit 9 by the user.

The video intermediate frequency amplification circuit 4 has an automatic frequency adjustment (AFT) circuit 10. This AFT circuit 10
Receives an image intermediate frequency signal and generates an AFT signal. The control unit 8 adjusts the local oscillation frequency control signal LV based on the AFT signal.

The tuner 3 is a tuner of a frequency synthesizer (hereinafter abbreviated as FS) system. The frequency synthesizer type tuner includes a local oscillation circuit having a PLL (Phase Locked Loop) and the like, and is a method of directly controlling the local oscillation frequency by externally designated frequency data. Since the predetermined frequency is maintained, there is a feature that the tuning accuracy is high, that is, the frequency accuracy is high.

In the tuning system of the present embodiment,
The control unit 8 is configured to operate as shown in FIG. 1 unlike FIG. The control unit 8 is constituted by a microcomputer, and the contents of a computer program used for controlling the operation are different.

FIG. 1 is a flowchart showing the operation of the control unit 3 according to the present embodiment. 8, the same reference numerals as those in FIG. 8 denote the same or corresponding processes. In FIG. 1, steps S1 to S4 are the same as those in FIG. The difference is that steps S6 to S8 are added, and the process proceeds to step S5 if the determination result in step S7 is N.

In step S6, the absolute value | f0−f0 ′ | = Δf of the difference between the local oscillation frequency f0 ′ obtained in step S4 and the local oscillation frequency f0 corresponding to the standard value is calculated. In the next step S7, it is determined whether or not the difference Δf is smaller than a predetermined value fB. If smaller, the process proceeds to step S8. In step S8, a signal for setting the local oscillation frequency to f0 is output, the AFT operation is stopped, and the channel selection ends. If the frequency difference Δf is not smaller than the predetermined value fB in step S7, a signal for setting the local oscillation frequency to f0 ′ is output (S5).

As described above, in this embodiment, when the frequency difference Δf is equal to or larger than the predetermined value fB, that is, when the difference between the broadcast frequency of the received television signal and the standard value is large, the frequency difference Δf is obtained by AFT. When the frequency difference Δf is smaller than the predetermined value fB, that is, when the broadcast frequency of the received television signal is sufficiently close to the standard value, the local oscillation frequency f0 obtained by the AFT is set. By using the local oscillation frequency f0 corresponding to the standard value instead of ', it is possible to obtain the local oscillation frequency with the frequency accuracy originally possessed by the frequency synthesizer. Therefore, even when the AFT circuit 10 is affected by a temperature change or an aging change, a channel can be selected without being affected by the change.

Embodiment 2 FIG. The configuration of the tuning system of this embodiment is the same as that of the first embodiment. However, the operation of the control unit 8 is different. That is, in this embodiment, the same processing as described in the first embodiment is performed at the time of channel setting of each channel, and the frequency difference Δf is set to a predetermined value.
If it is smaller than fB, then, when the channel is selected, a signal for setting the local oscillation frequency to f0 is output without performing the AFT operation, and the channel selection is completed.

[0024] Channel setting means that a tuner is tuned to a broadcast frequency of a broadcast station to be received, and after confirming that the broadcast is receivable, a channel is assigned to the broadcast station and the broadcast frequency of the broadcast station is stored in a channel memory corresponding to the channel. Say something to remember.

In this embodiment, when such a channel setting is performed, the same processing as described in the first embodiment is performed to determine the frequency difference Δf, and the frequency difference Δf is set to a predetermined value.
When it is smaller than fB, f0 is stored as local oscillation frequency data in a channel memory corresponding to the channel, and when the channel is selected later, the local oscillation frequency data (representing f0) is stored from the channel memory. It reads the data and supplies the data to the tuner.

FIGS. 2 and 3 show the operation of the control unit 8 in the present embodiment. In these figures, the same reference numerals as those in FIG. 1 indicate the same or corresponding processes.

FIG. 2 shows the operation when setting a channel.
First, when the channel setting operation is instructed by operating the key operation unit 9 (S11), the same processing as steps S1 to S8 in FIG. 1 is performed. At that time, in step S2, a value of the local oscillation frequency corresponding to the broadcast frequency of the broadcast station to be set is selected as f0. If it is determined in step S7 that the frequency difference Δf is smaller than the predetermined value fB, the process of step S8 is performed and the process of step S9 is performed. In step S9, a flag indicating that the frequency difference Δf is determined to be smaller than the predetermined value fB (hereinafter referred to as “f0 flag”) is set in the corresponding channel memory.

FIG. 3 shows the operation at the time of channel selection. When the selection of a certain channel is started (S21), it is determined whether or not the selected channel has been set (S22). If it is determined that the setting has been completed, it is determined whether or not the f0 flag is set in the channel memory (S23). If the f0 flag is set, a signal designating the local oscillation frequency f0 is supplied to the tuner 3 (S24). If the f0 flag is not set, the same processing as in steps S1 to S8 in FIG. 1 is performed to determine the local oscillation frequency (S25).

According to the second embodiment, when a channel is determined to have a broadcast frequency determined to be in accordance with a broadcast standard, the AFT operation can be omitted when the channel is subsequently received, and the time required for tuning can be reduced. And the power consumed by the circuit can be saved.

Embodiment 3 The configuration of the tuning system of this embodiment is the same as that of the first embodiment. However, the operation of the control unit 8 is different. That is, in this embodiment, after turning on the main power supply of the television receiver, the same processing as described in the first embodiment is performed when each channel is selected for the first time, and the frequency difference Δf becomes a predetermined value. If it is smaller than fB, then when the channel is selected, the local oscillation frequency is changed to f without performing the AFT operation.
A signal to be set to 0 is output to complete the channel selection.

FIG. 4 shows the operation of the control unit 8 in the present embodiment. In this figure, the same reference numerals as those in FIGS. 2 and 3 indicate the same or corresponding processes. First, the key operation unit 9
When a channel selection for a specific channel is instructed by the operation (S31), it is determined whether or not the channel is the first channel selection after power-on (S3).
2). This is performed by referring to a channel selection flag for each channel described later (indicating whether or not channel selection has been performed). If it is the first time, the same processing as S1 to S9 in FIG. 2 is performed (S33). Then, a flag (tuning flag) indicating that tuning has been performed is set (S34). If it is not the first time, it is determined whether the f0 flag is set in the channel memory (S35). If the f0 flag is set,
A signal for setting the local oscillation frequency to f0 is output (S3
6). If the f0 flag is not set,
The same processing as in steps S1 to S9 is performed to determine the local oscillation frequency (S37).

According to the third embodiment, when a channel is selected for the first time after the main power is turned on, the channel whose broadcast frequency is determined to be in accordance with the broadcasting standard is not changed until the main power is turned off. When receiving the broadcast of AF,
The T operation can be omitted, the time for tuning can be reduced, and the power consumed by the circuit can be saved.

Embodiment 4 FIG. The configuration of the tuning system of this embodiment is the same as that of the first embodiment. However, the operation of the control unit 8 is different. That is, in this embodiment, the same processing as described in Embodiment 1 is performed at the time of automatic channel selection of each channel, and when the frequency difference Δf is smaller than the predetermined value fB, the subsequent channel is selected. When the station is tuned, the signal for setting the local oscillation frequency to f0 is output without performing the AFT operation, and the tuning is completed.

The automatic tuning means that a search is performed within a predetermined band by changing a local oscillation frequency, and a tuning is performed by finding a broadcast frequency.
At the time of automatic channel selection, the same processing as in steps S1 to S8 in FIG. 1 is performed, and the frequency Δf is obtained.

FIGS. 5 and 6 show the operation of the control unit 8 in the present embodiment. 2 and 3 in these figures.
The same reference numerals indicate the same or corresponding processes.

FIG. 5 shows the operation of automatic channel selection. When the automatic tuning (S41) is completed for each station, it is determined whether the frequency difference Δf is smaller than a predetermined value fB (S42). If the frequency difference Δf is smaller, a f0 flag indicating that fact is used. (S43).

FIG. 6 shows the operation when selecting a channel. When the tuning of a station is started (S51), it is determined whether or not the f0 flag is set for the station (S52). If the f0 flag is set, a signal designating the local oscillation frequency f0 is output (S53). If the f0 flag is not set, the same processing as in S1 to S8 of FIG. 1 is performed (S5).
4).

According to the present embodiment, for a channel whose broadcast frequency is determined to be in accordance with the broadcast standard at the time of automatic channel selection, the AFT operation can be omitted when the broadcast is subsequently received, and tuning can be performed. And the power consumed by the circuit can be saved.

[0039]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, when the difference between the broadcast frequency of the received television signal and the broadcast frequency defined by the broadcast standard is large, the tuner operates at the local oscillation frequency obtained by AFT. Therefore, even if the broadcast frequency of the received television signal deviates from the broadcast standard, it is possible to appropriately select a station. On the other hand, when the broadcast frequency of the received television signal is sufficiently close to the standard value, control is performed so that the tuner operates at the local oscillation frequency f0 corresponding to the standard value instead of the local oscillation frequency f0 'obtained by AFT. I do. Thereby, the local oscillation frequency can be obtained with the frequency accuracy originally possessed by the frequency synthesizer. That is, when receiving a television signal having a broadcast frequency according to a broadcast standard, it is possible to select a channel with the original frequency accuracy of the frequency synthesizer.

According to the second aspect of the present invention, when a channel is determined to have a broadcast frequency determined to be in accordance with a broadcast standard, the AFT operation can be omitted when the channel is subsequently received. The time can be reduced and the power consumed by the circuit can be saved.

According to the third aspect of the invention, when a channel is selected for the first time after the main power is turned on, a channel whose broadcast frequency is determined to be in accordance with the broadcast standard is broadcast until the main power is turned off. , The AFT operation can be omitted, the time for tuning can be reduced, and the power consumed by the circuit can be saved.

According to the fourth aspect of the present invention, the AFT operation is omitted for a channel whose broadcast frequency is determined to be in accordance with the broadcast standard at the time of automatic tuning of each channel when the broadcast is subsequently received. Thus, the time for tuning can be reduced, and the power consumed by the circuit can be saved.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation of a control unit according to Embodiment 1 of the present invention.

FIG. 2 is a flowchart showing an operation of a control unit at the time of channel setting according to Embodiment 2 of the present invention.

FIG. 3 is a flowchart showing an operation of a control unit at the time of channel selection according to Embodiment 2 of the present invention.

FIG. 4 shows an operation of a control unit at the time of channel selection according to Embodiment 3 of the present invention.

FIG. 5 shows an operation of a control unit at the time of automatic channel selection according to a fourth embodiment of the present invention.

FIG. 6 is a flowchart showing an operation of a control unit at the time of tuning in Embodiment 4 of the present invention.

FIG. 7 is a block diagram of a television receiver including a conventional tuning system.

FIG. 8 is a flowchart showing the operation of the channel selection system.

FIG. 9 is an S-curve diagram showing characteristics of the automatic frequency adjustment circuit.

[Explanation of symbols]

2 antenna, 3 tuner, 4 video intermediate frequency amplifying circuit, 5 video detecting circuit, 6 video amplifying circuit,
7 cathode ray tube, 8 control unit, 9 key operation unit, 1
0 Automatic frequency adjustment circuit.

Claims (4)

[Claims] 1. A tuner (3) of a frequency synthesizer system for generating a video intermediate frequency signal in response to a received television signal, and an AFT signal received in response to a video intermediate frequency signal output from the tuner (3). Automatic frequency adjustment circuit (1
0) and a control unit (8) that receives an AFT signal from the automatic frequency adjustment circuit (10) and supplies a local oscillation frequency control signal to the tuner (3). The control unit (8) is configured to control the automatic frequency adjustment circuit (10).
And a difference (Δf) between the value of the local oscillation frequency (f0 ′) obtained by operating the device and the value of the local oscillation frequency (f0) corresponding to the broadcast frequency defined by the broadcasting standard, and the difference (Δf) is obtained. When Δf) is within a predetermined range (fB), a local oscillation frequency control signal designating a local oscillation frequency value (f0) corresponding to a broadcast frequency defined by the broadcast standard is supplied to the tuner (3). A tuning system characterized by the following. 2. The control unit obtains the difference when setting a channel of each channel, and operates the automatic frequency adjustment circuit when the difference is within the range, and thereafter when the broadcast of the channel is received. The tuning system according to claim 1, wherein the tuning is not performed. 3. The control unit obtains the difference when selecting a channel for the first time after the main power is turned on, and if the difference is within the range, thereafter until the next time the main power is turned off. 2. The tuning system according to claim 1, wherein when receiving a broadcast of the same channel, the automatic frequency adjustment circuit is not operated. 4. The automatic frequency adjustment circuit according to claim 1, wherein the control unit obtains the difference at the time of automatic channel selection of a broadcast of each channel, and if the difference is within the range, thereafter, when receiving the broadcast of the channel, 2. The tuning system according to claim 1, wherein is not operated.