JPS5942759Y2 - 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 television receivers etc. uses a variable capacitance diode to control the button, and by changing the tuning voltage applied to this button, 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 variable capacitance diodes, the number of TV broadcast channels to be received is reduced from 1 to 3.
channel (VHF low band) or 4~
12 channel (■F high band), in other words, the frequency band to be received is 90~1.
08MHz low frequency band or 176~222MH2
Band switching is also used with a band switching control type for CVHF low band and VHF high band.

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. FIG. 3 is a waveform diagram showing voltage waveforms applied to the tuning device shown in FIGS. 1 and 2. FIG.

As shown in FIG. 1, for the electronic tuner 10, a tuning variable resistor 20 and a vsw voltage control voltage generator 5 that controls the band switching voltage (VSW voltage) of the tuner.
A tuning device with 0 is attached.

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 the second fixation and FIG. 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) in order to receive a desired program, the first movable contact 21 button of the two-part resistor and the second movable contact 31 of the switch
sliding along resistor 22.23 and conductor 32.33, respectively.

As shown in FIG. 2, since the circuit configuration is k-shaped, 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 VHb and VL control voltages, the ■S
A SW voltage is obtained by the W voltage control voltage generator 50.

According to the circuit configuration shown in Figure 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
The W voltage becomes positive voltage +15■.

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 signal is generated as the SW 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 it is set to , and the button is pressed in a range where reception should not be possible, resulting in an unnatural reception state due to malfunction.

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 button and a tuning voltage terminal; and a VL voltage. a first conductor connected to the terminal;
a second conductor connected to the VH voltage terminal;
The button and V are provided in conjunction with the movable contacts of
a VH-VL switch having a second movable contact connected to an H-VL voltage source;
In a tuning device equipped with a first switching circuit for controlling the SW voltage etc., the VH control voltage output and the VL control voltage are a second switching circuit configured such that the output is input and the output terminal is connected to the tuning voltage terminal, and the rotation angle range in which the VH control voltage output and the VL control voltage are simultaneously zero volt input In the electronic tuner tuning device, the circuit is configured such that the second switching circuit operates so that the tuning voltage terminal voltage becomes substantially zero volts.

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 is a waveform diagram showing the waveform of the tuning voltage in the tuning device shown in FIG.

4 shows a tuning device energized by the electronic tuner 10, which includes a tuning variable resistor 20 and a SW voltage control voltage generator 50.

The variable resistor 20 is the same as that shown in FIG. 2, and includes a two-part resistor and a VH-VL 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 VH-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.

Next, explanation will be given while referring to FIG. 2, FIG. 4, and FIG. 5 at the same time.

1. First, consider the case where the rotation angle of the movable contact 21.31 is in the range a to b by operating the knob (not shown) of the tuning variable resistor.
1.31 is provided so that it always rotates 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 v1×C/Ω appears.

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

Then, +15V is applied to the first VL control voltage input terminal 51 connected to the VL voltage terminal 34, and the VH voltage terminal 3
The first VH control voltage input terminal 52 connected to VH 5 becomes zero voltage.

Then, since a positive voltage (15 V - voltage drop due to the diode 54) is applied to the connection point 53 via the diode 54, the transistor 55 whose emitter is connected to the positive voltage source (+15 V) 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 collector of the transistor 55 is connected to the transistor side end of the resistor 56. A negative voltage, for example -15V, appears at the connected SW voltage terminal 57.

Next, consider the case where the rotation angle of the movable contact 21.31 is in the range of C to d.

In this case, as mentioned above, the second
A voltage obtained by dividing the voltage V1 applied to the resistor 23 by the first movable contact 21 appears at the tuning voltage terminal 24.

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

Therefore, the transistor 55 becomes conductive, and a positive voltage (in this embodiment, +
15■) is applied.

Next, consider a case in which the conventional device had a problem, that is, a case where the movable contact 21.31 is within the range of rotation angle C.

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

That is, if we focus only on the voltage applied to the SW voltage terminal 57, even though the movable contact 21.31 is in the rotation angle range of b to C, it is in the rotation angle range of C to d. It can be said that the state is indistinguishable from the case where it is present.

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 constructed to prevent such a phenomenon that the vehicle is not heavy, and the switching circuit 6 shown in FIG.
0 is set.

This switching circuit 60 has a second VL control voltage input terminal 61 and a second VH control voltage input terminal 62.

The first and second movable contacts 21.31 are from a to b.
When the rotation angle is set in the rotation angle region, the VL control voltage is applied to the second L control voltage input terminal 61.

This 1L control voltage (+15V) is applied to the base of transistor 66 via diode 64 and resistor 65, making transistor 66 conductive.

Further, the collector of the transistor 66 is connected to the positive voltage source (+15V DC voltage source) via a resistor 67.

When the transistor 66 is conductive, a current flows from the positive voltage source to the ground through the transistor 66, so no driving current is applied to the base of the transistor 69 through the diode 68, and the transistor 69 is cut off. be.

Therefore, the tuning voltage appearing at the tuning voltage terminal 24 is supplied to the electronic tuner 10 without any influence.

Next, consider the case where the first and second movable contacts 21.31 are set in the rotation angle range C to d.

At this time, the VH control voltage appears at the second VH control voltage input terminal 62 and is applied to the base of the transistor 66 through the resistor 70, making the transistor 66 conductive.

Therefore, it appears at the tuning voltage terminal 24 in the same way as when the movable contact 21.31 is set in the rotation angle range a to b.

The tuning voltage is supplied to the electronic tuner 10 without any influence.

Furthermore, since the diode 64 is connected with the polarity shown, the positive voltage appearing at the second VH control voltage input terminal is not applied to the first VLL control voltage input terminal.

As explained above, when the tuning voltage terminal 24 or the first movable contact does not open, the switching circuit according to the present invention operates as usual without being affected by the switching circuit.

Next, when the front am point 21.31 is set in the rotation angle region from b to C, neither the VL control pressure button nor the VH control voltage is generated, so the second VL antistatic voltage input terminal 61 button and the second VH magic pressure input terminal 62 are at zero voltage, and the transistor 66 is in the M state.

Therefore, a driving current flows to the base of the transistor 690 through the positive voltage source, the resistor 67, and the diode 66, and the transistor 69 becomes conductive.

Since the collector of this transistor 69 is connected to the tuning voltage terminal 24, the tuning voltage terminal 24 is grounded when the transistor 69 is conductive.

Therefore, the undesirable phenomenon that a malfunctioning voltage appears at the tuning voltage terminal 24 when the tuning voltage terminal 24 is in the open state W is avoided.

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, 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. There is no.

[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 suitably 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 waveform diagram showing tuning voltage waveforms in the tuning device shown in FIG. 4. 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...VLL voltage terminal, 35...VH voltage terminal, 50...■
SW voltage control voltage generator, 51.61...■L
L control voltage input terminal, 52.62...VH control voltage input terminal, 54.58...Diode, 55.6
6゜69...Transistor, 56...
High impedance resistor, 57...■SW voltage terminal, 60...Switching circuit, 64.68.
...Diode, 65°67.70...
resistance.

Claims (1)

[Scope of utility model registration request] a first resistor having one end grounded and the other end connected to the tuning voltage source; a second resistor having one end grounded and the other end connected to the tuning voltage source; and the first resistor a two-part resistor having a first movable contact slidably disposed relative to the body and the second resistor and connected to a tuning voltage terminal; and a second movable contact connected to a VL voltage terminal. a second conductor connected to a VH voltage terminal; and a second conductor connected to the first movable contact and slidable relative to the first conductor button and the second conductor. a VH-VL switch having a second movable contact provided with a button and connected to a VH-VL voltage source; and at least one of a VH control voltage output and a VL control voltage output of the VH-VL switch. Then, the VH control voltage output and the VL control voltage output are inputted by pressing a button on a tuning device including a first switching circuit for controlling the band switching voltage of the tuner so as to switch the receiving frequency band of the electronic tuner, a second switching circuit configured such that an output terminal is connected to the tuning voltage terminal, and the VH control voltage output and the VL control voltage output are simultaneously pressed in a rotation angle range in which the output voltage is zero volts (my input); A tuning device for an electronic tuner, characterized in that the second switching circuit operates so that the tuning voltage terminal voltage becomes substantially zero volts.