JPH0336811A - Automatic channel selection circuit for television receiver - Google Patents

Abstract

PURPOSE:To simplify the confirmation of the reception state and the program content by stopping once the channel selection every time a synchronizing signal is detected when a channel change key is being depressed and starting the channel selection again after a prescribed time. CONSTITUTION:When a channel UP key 14 is being depressed, while a synchro nizing detection signal 21 is at an L level, a channel setting data 22 is continu ously revised and a tuning voltage 17 is stepwise increased. When a station receives the signal 21 and the signal 21 changes to an H level, the data 22 is fixed and the channel selection is stopped, and a video image is displayed on a picture display section 8 and since a key decision circuit 12 decides the state to be key consecutive depression state, the data 22 is again changed after a prescribed time. Thus, every time the station is received, the video image is displayed for a prescribed time and the channel is being switched, then the reception state and the program content are simply confirmed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an automatic channel selection circuit for television.

[Prior Art J] In conventional search channel selection televisions, if the channel up key or channel town key was held down, the channel immediately moved to the next channel even if a station existed.

[Problem to be solved by the invention 1 The search tuning method is convenient when it is not known how many channels are receivable, but when checking the reception status of all channels in advance, the conventional search tuning method I had to press the channel up key or channel down key, which was very cumbersome to operate.

Therefore, the present invention aims to solve such problems, and its purpose is to stop the channel selection once every time a station is received by pressing and holding the channel change key without having to operate it many times. To provide a channel selection method that allows easy checking of reception status.

[Means for Solving the Problems] The automatic television tuning circuit of the present invention provides: (1)a) A television tuning circuit that performs search tuning using a phase-locked loop.

b) By pressing the CHANNEL LUATSUBU key or CHANNEL DA RANK key, the 5 selected channels will start to go up or down continuously. When it is detected, the channel selection stops, that is, it enters the receiving state, and d) If the channel up key or channel town key is held down, the channel selection starts to go up or down again after a certain period of time after the channel selection stops. Features.

(2) a) In the television automatic channel selection circuit according to paragraph 1, b) in addition to the search channel selection mode, a preset channel selection mode in which only pre-stored channels can be selected; and C) the channel up. If the key or channel down key is kept pressed, channels stored in advance are sequentially selected at intervals shorter than the predetermined time.

[Example] Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 is a block diagram of an automatic channel selection circuit for a television according to the present invention, and FIGS. 2(a) and 2(b) are timing charts showing the operation of FIG. 1.

First, when the channel selection mode switch 13 is in search mode,
As shown in FIG. 2(a), when the channel up key 14 is pressed while an arbitrary station is being received, the key determination circuit 12 outputs a channel up command, and the channel selection control circuit 11 outputs a channel up command. The channel setting data 22 is continuously changed. Therefore, the frequency division ratio of the program frequency divider 4 is changed, and by the action of the phase locked loop 2 composed of the program frequency divider 4, the phase comparator 5, the low pass filter (LPF) 6, and the electronic tuning tuner 3, The tuning voltage 17 increases stepwise.

Therefore, when a station is received, the synchronization signal 20 included in the video signal 19 is separated by the synchronization separation circuit 9, and the synchronization detection signal 21 output from the synchronization detection circuit 10 becomes H level. As a result, the channel selection control circuit 11 fixes the channel setting data 22 and enters the channel selection stop state.

Next, when the channel up key 14 is held down, the channel setting data 22 is continuously changed while the synchronization detection signal 211 is at the JSL level, similar to when the key is momentarily pressed, and the tuning voltage 17 is changed stepwise. On the other hand, when a station is received and the synchronization detection signal 21 changes to H level, the channel setting data 22 is fixed and the channel selection is stopped, and an image is displayed on the image display section 8. Since the key determination circuit 12 determines that key 4 is pressed continuously, the channel setting data 22 is continuously changed again after a certain period of time. In this way, each time a station is received, a video is displayed for a certain period of time, and the channel changes.

Next, when the mode switch 13 is in the preset mode, as shown in FIG. 2(b), when the channel up key 14 is pressed while receiving an arbitrary station,
The channel setting data 22 of the next largest channel stored in advance is output from the channel selection control circuit 11,
Stop tuning.

Further, when the channel up key 14 is continuously pressed, the key determination circuit 12 determines that the key has been pressed continuously,
The channels are changed continuously in the order of pre-stored channel numbers. Therefore, in the preset mode, channels are fast-forwarded.

Further, when the channel down key 15 is pressed, the operation is the same as that for channel up except when the channel is changed in the down direction, so a description thereof will be omitted.

[Effects of the Invention] As explained above, the present invention, if you keep pressing the channel change key during search selection, the selection is temporarily stopped (about 0.5 to 1 second) every time a station is received. You can now easily check the status and program content.

Also, when selecting a preset channel, only the stations necessary for the purpose are memorized, so if you keep pressing the channel change key,
By continuously changing the stored channel number order, it was possible to quickly forward channels, making it possible to select channels very quickly on TVs that did not have direct channel selection keys.

In addition, conventional TVs search and select stations using a voltage synthesizer and preset receivable stations, but the search time is very long, taking 1 to 2 minutes, and in practice only preset channel selection can be used. However, the present invention uses a phase-locked loop to achieve both high-speed search tuning (10 seconds or less) and preset tuning, and is highly practical.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an automatic tuning circuit for a television according to the present invention. FIGS. 2(a) and 2(b) are timing charts showing the operation of FIG. 1.・Antenna・Phase locked loop Electronic tuning tuner Program frequency divider Phase comparator PF Video detection circuit Image display section Synchronization separation circuit Synchronization detection circuit Tuning control circuit Key determination circuit・Tuning mode switch 4 ・Channel up key・Channel down key that's all

Claims (2)

[Claims] (1) a) In a television channel selection circuit that uses a phase-locked loop to search and select channels, b) By pressing the channel up key or channel down key, the selected channel starts to change up or down continuously. c) When the synchronization detection circuit detects the presence or absence of a TV synchronization signal, when this synchronization signal is detected, the channel selection stops, that is, the reception state is entered, and d) When the channel up key or channel down key is held down. , an automatic television channel selection circuit characterized in that the channel selection starts to go up or down again after a certain period of time after tuning stops. (2) a) In addition to the search channel selection mode, there is also a preset channel selection mode in which only pre-stored channels can be selected, and b) If the channel up key or channel down key is held down, 2. The automatic television channel selection circuit according to claim 1, wherein channels are sequentially selected at intervals shorter than the predetermined time.