JPH01216614A - Tv channel selection device - Google Patents

Abstract

PURPOSE:To attain momentary tuning to a station having watched previously at its frequency band without needing any tuning even when the frequency band is switched by adding a tuning voltage memory circuit and a tuning voltage control circuit to a conventional circuit constitution. CONSTITUTION:When a channel button 28 or 29 is depressed, a clock signal with a prescribed frequency is inputted to an up-down counter 31. The output signal of the counter 31 is converted into a DC voltage by a D/A converter 32 and applied to an electronic tuner 22 as a tuning voltage. In the frequency band switching from a VHF band to a UHF band or vice versa, the output signal of the up-down counter 31 just before the switching is stored in a tuning voltage memory circuit 34. In the case of switching the frequency band from the UHF band into the VHF band or vice versa, the tuning voltage generated in response to the signal from the tuning voltage memory circuit 34 is applied to the electronic tuner 22. Thus, the program having watched previously without channel retrieval again in the frequency band switching is observed momentarily.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a television channel selection device.

[Conventional technology]

As a conventional TV channel selection circuit, application number 60-296
There are 566. As shown in FIG. 1, when the channel up button 8 or the channel down button 9 is pressed, a clock signal of a constant frequency is input to the up/down counter 11. The output signal of this counter 11 is converted into a DC voltage by a D/A converter 12 and then sent to an electronic tuner 2.
The output voltage of the AFT signal generation circuit 3, which detects and corrects the tuning deviation by the IF signal 13 from the electronic tuning tuner 2, which is applied as a tuning voltage to the Nearby, a synchronization signal from a television is detected by the synchronization detection circuit 5, and the circuit is turned on. Here, when the level of the character 8 characteristic passes through certain high and low levels and a synchronization signal is detected, the synchronization detection correction circuit 6
is determined to be tuned, and the automatic tuning control circuit 10 is reset. Therefore, the clock signal to the up/down counter 11 is stopped, and the channel selection operation is completed.

Furthermore, if a tuning deviation occurs after tuning, a correction command is generated from the tuning detection correction circuit 6 based on the APT signal, and a correction clock signal is given to the up/down counter 11 to perform a tuning correction operation. be exposed.

[Problem to be solved by the invention]

However, with the conventional circuit configuration, from VHF to tJHF.
Since the digital output signal of the up/down counter 11 remains unchanged even when the frequency band is switched to LJHF, the same voltage as the tuning voltage at VHF immediately before switching is applied to the electronic tuner 2 as the tuning voltage, and A clock signal is also not input to the up/down counter 11, so the operator cannot view the television screen unless a new tuning point is detected by pressing the channel up button 8 or the channel down button 9.

Next, even if you switch the frequency band from UHF to VHF again, you will not be able to immediately watch the station you were watching in the VHF band before, and by pressing the channel up button 8 or channel down button 9, you will be able to switch to the new VHF band. The tuning point must be detected in the band.

Therefore, the present invention is intended to solve these problems, and its purpose is to instantly change the station that was previously watched on the same band when switching the frequency band from VHF to UHF or from UHF to VHF. The aim is to provide a TV channel selection circuit that can be viewed on the internet.

[Means to solve the problem]

The television tuning device of the present invention includes: (1) a) a television tuning device; b) an electronic tuning tuner that performs tuning operation by applying a DC voltage as a tuning voltage; VHF from obi
When switching to the frequency band, the same "A'1" immediately before the switching
Tuned voltage memory circuit that stores 4 voltages.

d) From UHFW to VHF band again and from VHF band to U
When switching the frequency band to the HF band, according to the signal from the tuning voltage memory circuit, the same i1! The present invention is characterized in that it includes a tuning voltage control circuit that applies voltage again to the electronic tuning tuner.

〔Example〕

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

Channel button 28 or channel down button 2
When 9 is pressed, a clock signal of a constant frequency is input to the up/down counter 31. The output signal of this counter 31 is converted into a DC voltage by a D/A converter 32 and applied as a tuning voltage to the electronic tuner 22. Tuning deviation is detected and corrected by the IF signal 33 from the zero-order electronic tuning tuner 22. The output voltage of the AFT signal generation circuit 23 exhibits a figure-8 characteristic near the station, and near the station, the synchronization signal of the television is detected by the synchronization detection circuit 25 and turns on. Here, when the level of the character 8 characteristic passes certain high and low levels and a synchronization signal is detected, the tuning detection correction circuit 26 determines that the tuning has been achieved and resets the automatic tuning control circuit 30. do. Therefore, up/down counter 31
The clock signal to stops, and the channel selection operation ends.

If a tuning shift occurs after tuning, a correction command is generated from the tuning detection and correction circuit 26 based on the AFT signal, and a correction clock signal is given to the up/down counter 31 to perform a tuning correction operation.

Assume that the above operation is performed to tune to one channel in the VHF band, and the digital output of the 14-bit up-down counter at that time is 00011001010111 from the lower bits.

When switching the frequency band to the UHF band, 0001 is stored in the tuning voltage memory circuit 34 by a command from the counter control circuit 35.
1001010111 is stored.

In the UHF band, it is tuned to channel 30, and the digital output of the 14-bit up-down counter 31 at that time is 10.
Suppose that it is 011001111000.

When the frequency band is switched to the VHF band again, 100
11001111000 is stored, and 0001100 is also stored.
In order to output 1010111 as the set signal of the 14-bit up-down counter and the inverted signal of 00011001010111 as the reset signal of the 14-bit up-down counter, the output of the 14-bit up-down counter becomes oooiio at the same time as switching to the VHF band.

1010111, and you can instantly watch the program you were watching before switching without having to perform a channel search operation again.

FIG. 3 is an example of a detailed logic circuit of the tuning voltage memory circuit 34 and the counter control circuit 35. FIG. 4 shows a timing diagram of various parts of FIG. 3.

41 in FIG. 3 is a VHF/UHF switching signal generation circuit, and as shown in FIG. 4 101, when VHF is selected, the
Outputs low level when HF is selected. VHF/1JH
When the output of the F switching signal generation circuit 41 is input to the flip-flop 42 which operates at the rising edge of the clock, the result shown in FIG.
03 waveform is obtained. When the output of the flip-flop 42 is input again to the flip-flop 43, the waveform shown in FIG. 4 104 is obtained. The signal 104 is input to the electronic tuner 46 as a signal for switching frequency bands.

The output of flip-flop 43 and the output of flip-flop 42
By performing an AND with the inverted output of , the waveform shown in FIG. 4 105 is obtained. Also, if we take the AND of the output of the clip-flop 42 and the inverted output of the flip-flop 43, we get the fourth
The waveform shown in FIG. 106 is obtained.

47 is a 14-bit up/down counter. 48
．． 49, . . . , 61 are latches that take in the data signal when the clock signal is high, and hold the data signal at the falling edge while the clock signal is low.

The output of the AND gate 45 is input as a clock signal to the latches 48, 49, . . . , 61, and the 14-bit output signal of the up/down counter 47 is input as a data signal to the latches 48, 49, . Then, during the period when UHF is selected, the last output state of the up/down counter when VHF was previously selected is latched 48.4.
9,..., 61 are remembered.

When switching the frequency band from UHF to VHF again, go to ND
The output of gate 44 and latches 48, 49, . . . , 61
The output of each gate is inputted as a set signal to the up/down counter 47, and the output of the AND gate 44 is ANDed with the inverted output of the latches 48, 49, . . . , 61. By inputting each gate output as a reset signal to the up/down counter 47, when switching the frequency band to VHF, it is possible to reproduce the tuning voltage at VHF immediately before switching to UHF.

〔Effect of the invention〕

As described above, by adding a tuning voltage memory circuit and a tuning voltage control circuit to the conventional circuit configuration, the present invention eliminates the need for tuning operations even when switching frequency bands. It is extremely convenient because it allows you to instantly tune into the station that you are listening to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional television automatic tuning circuit. FIG. 2 is a block diagram of an automatic tuning circuit for a television according to the present invention. FIG. 3 is a diagram showing an example of a detailed circuit configuration of the tuning voltage memory circuit and the counter control circuit, and FIG. 4 is a timing diagram of various parts of FIG. 3. 1... Antenna 2... Electronic tuning tuner 3... APT signal generation circuit 4... Video detection circuit 5... Synchronization detection circuit 6... Tuning detection correction circuit 7... Clock generation circuit 8 ...Channel up button 9...Channel down button 10...Automatic tuning control circuit 11...Up/down counter 12...D/A converter 13...IF multiplication signal 1...Antenna 22... Electronic tuning tuner 23... AFT signal generation circuit 24... Video detection circuit 25... Synchronization detection circuit 26... Tuning detection correction circuit 27... Clock generation circuit 28... Channel up Button 29... Channel down button 30... Automatic leaving control circuit 31... Up/down counter 32... D/A converter 33... IF double signal 4... Tuning voltage memory circuit 35... ...Counter control circuit 41 ...-VHF/UHFgJ conversion signal generation time 1142
... Flip-flop 43 ... Flip-flop 44 ... Two-man power AND gate 45 ... Two-man power AND gate 46 ... Electronic tuning tuner 47 ... 14-bit up-down counter 48 ...
Latch 49... Latching 61... Latch 101... V HF/U HF switching signal generation circuit output waveform □ 102... Clock signal input waveform 103... Flip-flop 42 output waveform 104.
...Output waveform 105 of flip-flop 43...AN
Output waveform 106 of D gate 44...AND gate 45
Figure 1 Figure 2

Claims (1)

[Claims] (1) a) In a TV channel selection device, b) An electronic tuning tuner that performs tuning operation by applying a DC voltage as a tuning voltage, c) From a VHF band to a UHF band, or from a UHF band to a VHF band.
A tuning voltage memory circuit that stores the tuning voltage immediately before switching when changing frequency bands. d) From UHF band to VHF band or from VHF band to UH
A TV tuning device comprising a tuning voltage control circuit that applies a tuning voltage generated according to a signal from the tuning voltage memory circuit to the electronic tuning tuner when switching the frequency band to the F band.