JP3019109U - Automatic tuning device - Google Patents

Abstract

(57) [Summary] [Purpose] During automatic tuning, you do not need to select unwanted stations such as weak stations buried in noise or spurious signals from strong input stations, and there is no need to organize preset stations after automatic tuning. so,
Provide an automatic channel selection device capable of speeding up automatic channel selection. [Structure] The microcomputer 5 controls the tuning operation of the tuner 2 and outputs the output of the AGC circuit 6 input to the AGC input terminal of the tuner 2 to the tuner 2 when the operation mode for automatic tuning is entered. Change to reduce the gain. As a result, the spurious signal of a weak station or a strong input station which is buried in noise is not selected.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an automatic channel selection device such as a television for automatically selecting a broadcasting station channel and preset memory.

[0002]

[Prior art]

 Conventionally, in this kind of automatic tuning device, the tuner gain is controlled by an automatic gain control (AGC) circuit, but since it is operated with a constant tuner gain during automatic tuning operation, it is likely to be buried in noise. The spurious signals of weak and strong input stations may be selected and stored in preset memory.

[0003]

[Problems to be solved by the device]

 However, in the conventional automatic channel selection device as described above, unnecessary stations are tuned in.Therefore, it is necessary to organize the preset channels after the channel selection operation. There was a problem that I could not do it. The present invention has been made to solve the above-mentioned problems, and automatically skips unwanted stations such as spurious signals of weak stations or strong input stations that are buried in noise during automatic channel selection. Therefore, it is an object of the present invention to provide an automatic channel selection device that does not need to organize preset stations after automatic channel selection, saves labor, and speeds up automatic channel selection.

[0004]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the invention of claim 1 is a tuner for automatically selecting a broadcasting station channel and selecting a predetermined channel station from received broadcast waves in an automatic tuning device for presetting in a memory. It is equipped with an AGC circuit that outputs a signal to the tuner for automatically controlling the gain by the tuner, and a microcomputer that controls the tuning operation by the tuner. When the microcomputer enters the operation mode for automatic tuning, it The output of the AGC circuit input to the AGC input terminal is changed to reduce the gain of the tuner. According to a second aspect of the present invention, in the apparatus according to the first aspect, there is provided a switching element which is turned on / off according to a signal level from an output port of the microcomputer, and the tuner AGC is provided via the switching element. A resistor is inserted between the input terminal and ground, and the level of the signal input to the AGC input terminal is changed depending on the presence or absence of this resistance.

[0005]

[Action]

 In the automatic channel selection device according to claim 1, having the above configuration, the AGC circuit outputs a signal for automatically controlling the gain by the tuner to the tuner, and the microcomputer controls the tuning operation by the tuner and automatically When the operation mode for tuning is entered, the output of the AGC circuit input to the AGC input terminal of the tuner is changed so as to reduce the gain of the tuner. This prevents spurious signals from weak or strong input stations that might be buried in noise from being tuned. According to another aspect of the automatic channel selecting apparatus of the present invention, the microcomputer turns on / off the switching element, and when the switching element is turned on, a resistor is inserted between the AGC input terminal of the tuner and the ground. By inserting this resistor, the signal level input to the AGC input terminal changes so as to reduce the gain of the tuner. By selecting this resistance value appropriately, the automatic tuning level can be set arbitrarily.

[0006]

【Example】

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a main part of a television equipped with an automatic channel selection device. The automatic channel selection device 1 includes a tuner 2 that selects a predetermined channel station from the received television broadcast radio waves, an IFI C3 that performs intermediate frequency amplification of the channel signal selected by the tuner 2, and an intermediate frequency amplified signal. A video chroma IC 4 for amplifying and detecting a video signal, a microcomputer 2 for controlling the operation of the tuner 2 and other circuits, and an AGC (automatic gain control) input terminal of the tuner 2 An AGC circuit 6 for generating a GC output and an AFT circuit 7 for outputting an AFT signal for AFT (automatic frequency tuning) are provided. A horizontal deflection output circuit, a vertical deflection output circuit, an audio output circuit, a CRT for displaying television images, a speaker for outputting audio, etc. are not shown.

The microcomputer 5 receives an operation signal from a remote controller (not shown), outputs a tuner control signal, and selects an auto preset menu to select an operation mode for automatic tuning. Enter, and at that time, it has the function of reducing the gain of tuner 2. As a specific configuration therefor, the output terminal of the AGC circuit 6 is connected to the AGC input terminal of the tuner 2 via the resistor R1, and the AGC input terminal connects between the resistor R2 and the collector-emitter of the transistor 8. The transistor 8 is grounded via an ON / OFF control according to the signal level from the output port of the microcomputer 5. In this configuration, when the microcomputer 5 enters the auto preset operation, it outputs the H signal from the output port, and accordingly the transistor 8 is turned on. As a result, the AGC input terminal has a resistor R1 and a resistor R1. The divided voltage by R2 is applied, the signal level input to the AGC input terminal decreases, and the gain of the tuner 2 decreases.

The microcomputer 5 also receives the synchronization signal (SD) detected by the video chroma IC 4 and the AFT output from the AFT circuit 7. Then, the preset data obtained by the automatic tuning operation is preset in the built-in RAM of the microcomputer 5 for each channel. If the output of the tuner 2 is low, the AGC circuit 6 in the normal operation works to raise the output voltage of the AGC and increase the output of the tuner 2.

The auto preset operation of the automatic channel selection device 1 of the present embodiment configured as described above will be described with reference to the flowcharts of FIGS. 2 and 3. In FIG. 2, when the microcomputer 5 enters the auto-preset operation, H is output to the auto-preset terminal of the output port, thereby turning on the transistor 8 to lower the AGC signal to the AGC terminal of the tuner 2. The tuner gain is reduced (S1). After that, the tuning operation signal is output from the microcomputer 5 to perform the tuning operation (S2). After the tuning operation, L is output to the auto preset terminal and the transistor 8 is turned off to restore the AGC signal to the AGC terminal of the tuner 2 to the original value and set the tuner gain to a normal value (S3).

FIG. 3 shows the details of the tuning operation. When a channel is designated by an operation from a remote controller (not shown), the microcomputer 5 outputs a tuner control signal of the designated channel to the tuner 2 and the tuner 2 outputs the tuner control signal. 2 tunes the channel (S21). The tuning output of the tuner 2 is input to the IFIC 3 via the preamplifier and is amplified at the intermediate frequency. The video signal obtained by the IFIC3 is input to the video chroma IC 4 which extracts the sync signal SD if there is a broadcast channel. Further, the AFT circuit 7 receiving the signal from the IFIC 3 outputs the AFT signal. The microcomputer 5 checks whether the sync signal SD is present (S22), and if the sync signal SD is present, further checks whether the AFT signal is normal (S23). If the AFT signal is normal, the channel station is preset, that is, stored in the internal RAM (S24). After that, the operation proceeds to the tuning operation for the next channel (S25), and the above operation is repeated again. If the sync signal SD is not present in S22 and if the AFT signal is not normal in S23, the process proceeds to S25 without performing the preset process of S24. It should be noted that the threshold value for determining whether or not the sync signal SD 1 is present in S22 may be set appropriately.

Since the above tuning operation is performed in a state where the tuner gain of the tuner 2 is small, a channel station signal having a weak radio field intensity and a spurious signal of a strong input station are not tuned. Since unwanted channel stations are not preset, it does not take time to organize the preset channels after the automatic channel selection operation.

The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the operation mode in which automatic tuning is performed, the level of automatic tuning can be arbitrarily set by appropriately selecting the value of the resistor R2 inserted to reduce the gain of the tuner 2. Further, as a configuration for reducing the gain of the tuner 2, the configuration may be such that the microcomputer 5 controls the operation of the AGC circuit 6.

[0013]

[Effect of device]

 As described above, according to the automatic channel selection device of the first aspect of the present invention, the output of the AGC circuit is changed at the time of automatic channel selection to reduce the tuner gain, so that a weak station or a strong input station that is buried in noise. No unwanted stations such as spurious signals are tuned in. Therefore, there is no need to organize preset stations after automatic tuning, which saves time and effort, and speeds up automatic tuning. Further, according to the automatic channel selection device of the invention of claim 2, in addition to the above effect, a resistor is inserted between the AGC input terminal of the tuner and the ground to change the gain of the tuner. By selecting the resistance value appropriately, the automatic tuning level can be set arbitrarily.

[Brief description of drawings]

FIG. 1 is a block diagram of an automatic channel selection device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an automatic channel selection operation by the device.

FIG. 3 is a flowchart of an automatic channel selection operation when a channel is designated.

[Explanation of symbols]

 1 Automatic tuning device 2 Tuner 5 Microcomputer 6 AGC circuit 8 Transistor R2 Resistance

Claims (2)

[Scope of utility model registration request] 1. A tuner for automatically selecting a broadcasting station channel and presetting in a memory, a tuner for selecting a predetermined channel station from received broadcast waves, and a gain for automatically controlling the gain by the tuner. An AGC circuit for outputting a signal to the tuner and a microcomputer for controlling the tuning operation by the tuner are provided, and the microcomputer inputs to the AGC input terminal of the tuner when the operation mode for automatic tuning is entered. The automatic channel selection device characterized in that the output of the above-mentioned AGC circuit is changed to reduce the gain of the tuner. 2. A switching element that is turned on / off according to a signal level from an output port of the microcomputer, and a resistor is inserted between the AGC input terminal of the tuner and the ground via the switching element. The automatic channel selection device according to claim 1, wherein the signal level input to the AGC input terminal is changed depending on the presence or absence of a resistor.