JPS5942757Y2 - Tuning device for electronic tuner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tuning device attached to an electronic tuner of a television receiver.

Generally, the tuning circuit of an electronic tuner used in a television receiver etc. uses a variable capacitance diode, and by changing the tuning voltage applied to the diode, it is possible to tune to the frequency of each television broadcast.

However, it is generally considered difficult to cover the entire frequency range used in television broadcasting by relying solely on the rate of change in capacitance of the variable capacitance diode.

In order to compensate for this lack of capacitance change rate of the variable capacitance diode, the number of TV broadcast channels to be received is 1 to 3.
channel (VHF low band) or 4~
12 channel (VHF high band), in other words, the frequency band to be received is from 90 to
108MH2 (7) Is it in the low frequency band?176~222
Band switching using a band switching control voltage is also used for VHF low band and VHF high band to determine whether it is in the high frequency band of MH2.

Next, the above conventional example will be explained with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing an example of a conventional tuning device, and FIG. 2 shows a tuning variable resistor equipped with a VH-VL switch suitably used in the tuning device shown in FIG. 3 is a schematic diagram, and FIG. 3 is a waveform diagram showing voltage waveforms in the tuning device shown in FIGS. 1 and 2. FIG.

In FIG. 1, a tuning device having a tuning variable resistor 20 and a SW voltage control voltage generator 50 for controlling the band switching voltage (VSW) of the tuner is attached to a voltage tuner 10.

The circuit configuration and operation of the variable resistor 20 and the control voltage generator 50 are substantially the same as the circuit of the embodiment according to the present invention, which will be described later, so a description thereof will be omitted.

Next, a description will be given with reference to FIGS. 2 and 3.

The tuning variable resistor is a two-part resistor and VH-V.
It is equipped with an L switch.

When the television receiver turns a knob (not shown) to receive a desired program, the first movable contact 21 of the two-part resistor and the second movable contact 31 of the switch
sliding along resistors 22, 23 and conductors 32, 33, respectively.

Since the circuit configuration is as shown in FIG. 2, as the knob is rotated, a tuning voltage, a VH control voltage, and a VL control voltage as shown in FIG. 3 are generated.

Then, based on the VH and VL control voltages, the ■S
The VSW voltage is obtained by the W voltage control voltage generator 50.

According to the circuit configuration shown in Fig. 1, when the VL signal is high (for example, +15V), the SW voltage is a negative voltage of -15V, and in other cases (for example, zero volts), the SW voltage is a negative voltage of -15V.
The voltage becomes a positive voltage +15V.

When the knob is rotated and the rotation angle falls within the range b to C, the tuning voltage terminal 24 becomes open.

Normally, a reverse bias voltage is applied to the variable capacitance diode, but in this way, the tuning voltage terminal 2
4 is open, high frequency signal voltages from other circuits connected to the tuner tuning line may be rectified by this diode and appear at the tuning voltage terminal 24, which may reach +7 volts. be.

Even if the rotation angle of the knob is in the range b to C, a positive voltage is generated as the VSW voltage, as described above.

Therefore, at this time, if the tuning voltage that should be zero takes a certain positive voltage value due to the influence of other circuits as described above, the rotation angle at which the knob emits the voltage in the range C to d. The situation is the same as when the setting is set to , and an unnatural reception state due to malfunction occurs in a range where reception should normally be impossible.

The purpose of the present invention is that when the knob of a tuning variable resistor is rotated, the tuning voltage terminal connected to a movable contact slidably provided on the two-part resistor of the variable resistor is opened. It is an object of the present invention to provide a tuning device that can prevent reception of television broadcasting due to malfunction in a rotation angle range of .

The gist of the invention includes a first resistor having one end grounded and the other end connected to a tuning voltage source, and a second resistor having one end grounded and the other end connected to the tuning voltage source. , a two-part resistor having a first movable contact slidably disposed relative to the first resistor and the second resistor and connected to a tuning voltage terminal; and a VL voltage terminal. a first conductor connected to;
a second conductor connected to the VH voltage terminal;
is interlocked with a movable contact and is slidably provided with respect to the first conductor and the second conductor, and
a VH-VL switch having a second movable contact connected to an H-VL voltage source;
VSW is set to the optimum operating voltage condition for the electronic tuner used with H control voltage output and VL control voltage output.
In a tuning device including a switching circuit for controlling voltage, etc., a third movable contact that operates in conjunction with the first movable contact and the second movable contact and is connected to the tuning voltage terminal; , the first movable contact is arranged to be in contact with the third movable contact in a movable contact rotation angle region in which the first movable contact does not come into contact with either the first or second resistor, and is grounded. A tuning device for an electronic tuner includes a grounding switch having a ground conductor.

Hereinafter, the tuning device according to the present invention will be explained based on examples.

FIG. 4 is a circuit diagram showing an embodiment of the present invention, and FIG. 5 shows a tuning variable resistor equipped with a VH-vL switch that can be suitably used in the tuning device shown in FIG. This is a schematic diagram, and Figure 6 shows the death of Figure 4 and Figure 5.
FIG. 3 is a waveform diagram showing voltage waveforms applied to the tuning device shown in the figure.

In FIG. 4, a tuning device attached to the electronic tuner 10 is shown, which includes a tuning variable resistor 20 and a VSW voltage control voltage generator 50.

As shown in FIG. 5, the variable resistor 20' includes a two-part resistor, a VH-VL switch, and a ground switch.

The resistor includes a first movable contact 21 connected to a tuning voltage terminal 24, and resistors 22 and 23, one end of which is grounded and the other end connected to a tuning voltage source.

The -VL switch has a second movable contact 31 connected to the VH-VL positive voltage source, a conductor 32 connected at one end to the VL voltage terminal 34, and one end connected to the VH voltage terminal 35. A conductor 33 is provided.

Further, the grounding switch invented according to the present invention includes a third movable contact 41 connected to the tuning voltage terminal 24 and a grounded conductor 42.

Next, a description will be given with simultaneous reference to FIGS. 4 to 6.

Consider a case where the rotation angle of the movable contacts 21, 31.degree. 41 is in the range a to b by operating a knob (not shown) of the tuning variable resistor.

Of course, the movable contacts 21, 31, and 41 are provided so as to always rotate by the same rotation angle in conjunction with the knob □.

As the knob rotates, the voltage 1 applied to the first resistor 22 from the tuning voltage source (+33V in this embodiment) is divided by the first movable contact 21 to the tuning voltage terminal 24. A voltage VIXΩ/crystal appears.

A predetermined voltage (+15V in this embodiment) appears from the VH-VL voltage source at the switched VL voltage terminal 34, while
The voltage at the H voltage terminal 35 becomes zero.

Then, +15V is applied to the VL control voltage input terminal 51 connected to the VL voltage terminal 34, and the VH control voltage input terminal 52 connected to the VH voltage terminal 35 becomes zero voltage.

Then, since a positive voltage (15V - voltage drop due to the diode 54) is applied to the connection point 53 via the diode 54, the transistor 55, which is connected to the positive voltage source (+15V), is cut off.

Further, the collector of the transistor 55 is connected to a negative voltage source (-15V) via a high impedance resistor 56, and when this transistor is in a cut-off state, the transistor side end of the resistor 56 A negative voltage, for example -15V, appears at the SW voltage terminal 57 connected to the SW voltage terminal 57.

Next, consider the case where the rotation angles of the movable contacts 21, 31, and 41 are in the range C to d.

In this case, as mentioned above, the second
A voltage obtained by dividing the voltage (1) applied to the resistor 23 by the first movable contact 21 appears at the tuning voltage terminal 24.

Further, contrary to the above case, the VL voltage terminal 34 becomes zero voltage, and +15V is applied to the VH voltage terminal 35.

Therefore, the transistor 55 becomes conductive, and a positive voltage (+ in this embodiment) is applied from the positive voltage source to the SW voltage terminal 57.
15V) is applied.

The VH control voltage does not seem to have any effect, but by changing the polarity of the transistor, the switching operation of the transistor 55 can be controlled by the VH control voltage.
It is also possible to control the SW voltage.

In addition, in combination with a UHF tuner (not shown), VH
This is necessary to configure a control circuit to enable F, UHF reception.

However, since this is not directly related to the present invention, the explanation will be omitted.

Next, consider a case in which the conventional device had a problem, that is, a case where the movable contacts 21, 31, 41 are within the rotation angle range C.

In this case, since the voltage at the VL control voltage input terminal 51 is zero, the transistor 55 is in a conductive state, and the VL control voltage input terminal 51 is in a conductive state.
A predetermined positive voltage of +15V is applied to the S'w voltage terminal 57.

That is, if we focus only on the voltage applied to the VSW voltage terminal 57, even though the movable contact 21° 31.41 is within the rotation angle range b to C, it is within the rotation angle range C to d. It can be said that the condition is indistinguishable from the case where it is within the range.

Therefore, if a positive voltage appears at the tuning voltage terminal 24 for some reason, the fourth to twelfth
Among the channels, the channel corresponding to that voltage value will be received.

The device of the present invention is designed to prevent such undesirable phenomena.

That is, one end is connected to the tuning voltage terminal 24 and the first and second movable contacts 21.3
A third movable contact 41 provided to rotate in conjunction with 1
In addition, in a state where the tuning voltage terminal 24 and the first movable contact 21 are in a non-contact (blocking) state and the tuning voltage terminal 24 is open,
A grounding switch having a conductor 42 for grounding the tuning voltage terminal 24 via the third movable contact 41 is provided.

Incidentally, instead of grounding the terminal 24 when it is open, a negative voltage may be applied thereto.

According to the above configuration, as shown in FIG.
A desired tuning voltage can be obtained for the rotation angle of the movable contacts 21, 31, and 41, and when the tuning voltage terminal is in an open state, an unnatural reception state due to malfunction as in conventional devices is not caused. do not have.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional tuning device. FIG. 2 is a schematic diagram showing a tuning variable resistor equipped with a VH-VL switch that is preferably used in the tuning device shown in FIG. FIG. 3 is a waveform diagram showing an example of a voltage waveform in the tuning device. FIG. 4 is a circuit diagram showing an embodiment of the present invention. FIG. 5 is a schematic diagram showing a tuning variable resistor equipped with a VH-VL switch that is suitably used in the tuning device shown in FIG. 4. FIG. 6 is a waveform diagram showing voltage waveforms in the tuning device. 10...Electronic tuner 20,20...
...Tuning variable resistor, 21, 31, 41...
...Movable contact, 22, 23...Resistor, 24
...Tuning voltage terminal, 32, 33, 42
...Conductor, 34...VL voltage terminal, 3
5...VH voltage terminal, 50...■SW
Voltage control voltage generator, 51...VL control voltage input terminal, 52...VH control voltage input terminal, 54...
...Diode, 55...Transistor,
56... High impedance resistor, 57...
...■SW voltage terminal.

Claims (1)

[Claims for Utility Model Registration] A first resistor having one end grounded and the other end connected to the tuning voltage source; and a second resistor having one end grounded and the other end connected to the tuning voltage source. a two-part resistor having a first movable contact slidably disposed relative to the first resistor and the second resistor and connected to a tuning voltage terminal; a first conductor connected to the voltage terminal, a second conductor connected to the VH voltage terminal, and the first conductor and the second conductor interlocked with the first movable contact; 9 and VH-VL
-V with a second movable contact connected to a voltage source
A switching circuit for controlling the band switching voltage of the tuner so as to switch the reception frequency band of the electronic tuner using the L switch and at least one of the VH control voltage output and the VL control voltage output of the -VL switch. A tuning device comprising: a third movable contact that is interlocked with the first movable contact and the second movable contact and is connected to the tuning voltage terminal; and a third movable contact that is connected to the tuning voltage terminal; a grounding switch, the grounding switch having a grounded conductor arranged to contact the third movable contact in a movable contact rotation angle region where the movable contact does not come into contact with either the second resistor; A tuning device for an electronic tuner characterized by: