JPS584269Y2 - Channel selection device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a channel selection device such as a television receiver.

In a channel selection device such as a television receiver that uses an integrated circuit for electronic channel selection (hereinafter referred to as IC), when tuning is performed by remote control, this operation is called "channel". After that, a pulse train is applied to the sequential feed terminal of the electronic channel selection IC to sequentially send the channel selection to the desired channel (hereinafter, this operation will be referred to as channel sending).

FIG. 1 is a circuit diagram of a tuning circuit in an electronic tuning device.

In FIG. 1, the channel selection circuit is the channel selection IC1. Consists of channel selection switches 6-1 to 6□2, variable resistors 7-1 to 7-1□, etc. Although not all are shown in Figure 1, the channel selection switches and variable resistors are used to select channels. There are provided the number of the number, and usually about 10 to 12.

The channel selection IC 1 includes an oscillator 2, a counter 3, a decoder 4, a channel selection output circuit 5, etc., and has output terminals 9-1 to 9-1□ corresponding to the number of channel selection channels.

Hereinafter, the number of channels to be selected will be 12, and the channel selection operation will be explained with reference to FIG.

Assume that the user performs a normal channel selection operation in which the user presses the channel selection switches 6□ to 6□2 to select a channel, and the channel corresponding to the channel selection switch 6□ is currently selected.

Next, when the tuning switch 6□2 is connected, the power terminal 2
0, a DC voltage is applied to the bias voltage terminal 17 of the oscillator 2 via the variable resistor 7-□2, the channel selection switch 6-1□, and the resistor 10, and the oscillator 2 starts oscillating.

The oscillation period of this oscillator 2 is determined by a circuit consisting of a resistor 12 and a capacitor 11.

Further, the output of the oscillator 2 is applied to the tuning output circuit 5 via the counter 3 and the decoder 4, and at this time, the tuning output circuit 5 is applied to the tuning output circuit 5.
The output terminals 9-1 to 9-1□ are 9-1 to 9. ．． 9-3
They are fixed to the ground potential one by one in sequence as shown below.

A timing chart of the channel selection circuit is shown in FIG.

Although not shown in FIG. 1, the output terminals 9□ to 9□2 are of an open collector type and take two states: 'H' level (floating) and 'L' level (earth potential).

As shown in Figure 2, the voltage at output terminals 9□ to 9-1□ is
Since the bias voltage terminal 17 of the oscillator 2 is grounded via the resistor 10 and the channel selection switch 6-12, when the output terminal 9-1□ becomes the L level as the output terminal 9-1□ changes sequentially from the H" level to the L level, The oscillator 20 oscillation operation is stopped.

As a result, the output terminal 9-□2 is maintained at the L level.

At this time, current flows from the power supply terminal 20 to the output terminal 9-1□ via the variable resistor 7-1□, and the sliding terminal of the variable resistor 7-1□ is normally connected to the sliding terminal corresponding to the position of the sliding terminal. A DC voltage of about 0 to 33V can be obtained.

This voltage is passed through the diodes 8□ to 8-1□ and the tuning output terminal 21 to the tuner's variable capacitance diode (not shown).
It is well known that the channel can be selected by applying a signal to the channel.

As mentioned above, in a normal channel selection device, the oscillator 2
A bias voltage is applied to the oscillator to cause oscillation, and this oscillation output sequentially fixes the output terminals 9□ to 9-□2 from a floating state to the ground potential, and this ground potential is applied to the oscillator 2 to stop the oscillation. It has become.

In such a channel selection device, when channel selection is performed by remote control as described above, it would be convenient if channels could be easily reset.

Furthermore, when a television receiver is connected to a video tape recorder (hereinafter referred to as a VTR), it would be convenient if the channel could be easily reset to the VTR playback channel when the playback lever of the VTR is pressed.

An object of the present invention is to provide a tuning device using an IC for electronic tuning, which is equipped with a reset circuit for easily and reliably resetting to a predetermined channel. be.

The present invention will be explained below with reference to examples.

FIG. 3 is a circuit diagram showing an embodiment of the channel selection device of the present invention, in which a reset circuit is constituted by a resistor 13, diodes 14 and 15, and a pulse voltage generating circuit 16.

In this embodiment, the channel is reset to the channel corresponding to the channel selection switch 6□.

Now, a case will be described in which a channel is reset when any of the output terminals 9-2 to 9□2 is at the L level and the output terminal 9-1 is at the H level.

When the channel is reset, the pulse voltage generation circuit 16 operates, and a bias voltage is supplied to the oscillator 2 through the resistor 13 and diode 14.

At this time, the diode 15 is cut off because the output terminal 9-1 is at H level.

When a bias voltage is supplied to the oscillator 2, the oscillator 2 starts oscillating, and channel feeding is performed as described above.

When channel sending is performed and the level of the output terminal 9-1 becomes L level, the diode 15 becomes conductive and the diode 14 is cut off, so that the bias voltage is no longer supplied to the oscillator 2, and the operation of the oscillator 2 is stopped. do.

As a result, the channel feed is stopped and the output terminal 9-1 is set to L.
Since the level is maintained, the channel corresponding to the channel selection switch 6-□ is selected.

Note that the width of the pulse generated by the pulse voltage generation circuit 16 to supply the bias voltage to the oscillator 2 is longer than the time required to sequentially switch the output terminals 9-1 to 9-1□ to the L level for one cycle. must also be large, and must be greater than (oscillation period of oscillator 2) x (number of output terminals - 1).

As explained above, according to the channel selection device of the present invention, it is possible to easily reset the channel to a specific channel.
When remotely controlling a television receiver, it becomes possible to reset the channel to a specific channel and then select the channels sequentially.

Furthermore, when a television receiver is used by connecting it to a VTR, it becomes possible to automatically reset the channel to the VTR playback channel.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional tuning circuit, FIG. 2 is a timing chart of the tuning circuit, and FIG. 3 is a circuit diagram of a tuning circuit according to the present invention. 1... IC for tuning, 2... Oscillator, 9
-~9□2... Output terminal, 14, 15...
...Diode, 16...Pulse voltage generation circuit, 17...Bias voltage terminal.

Claims (1)

[Scope of utility model registration request] An electronic channel selection IC comprising an oscillator operated by a bias voltage applied to a bias voltage terminal, and a plurality of output terminals whose output states are sequentially switched between two types, high and low, by the oscillation operation of the oscillator; A pulse voltage generation circuit that generates a pulse voltage having a time width longer than the time required to switch the output states of all output terminals of an electronic channel selection IC from high to low for one cycle, and between the pulse voltage generation circuit and the bias voltage terminal. A second diode connected to the pulse voltage generation circuit between the first diode connected to the pulse voltage generation circuit and an arbitrary output terminal with an electrode having the same polarity as the electrode of the first diode. A channel selection device comprising: