JPS5855694Y2 - Electronic tuner channel selection device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a channel selection device for a television receiver using an electronic tuner.

In general, VHFHF Ketyanner low channel, i.e. the first
~The third channel is allocated 90-108 MHz, and the high channel, that is, the 4th to 12th channels, is allocated 177 MHz.
~222 MHz is allocated, so when selecting a channel using an electronic tuner, the band selection switch is used to switch between three bands: the low and high channels of the VHF band, and the VHF band.

A tuning coil for the low channel and a tuning coil for the high channel are provided corresponding to the above band selection switch, and when configured as an all-channel tuner, the UH
Install a tuning coil for F.

On the other hand, a variable capacitance diode (hereinafter abbreviated as VCD) coupled to each of the coils is provided, and a bias voltage is applied to the VCD.

The present invention provides a suitable tuning device for an electronic tuning tuner in which a resonant circuit is formed by each of the tuning coils and a VCD, and will be explained below with reference to the drawings.

Figure 1 shows an example of selecting 4 stations. 1゜2.3.4 are terminals for applying the tuning instruction signal, 5, 6, 7.8 are 1-circuit 3-contact type band preset switches, 9, 10 , 11° 12 is a reverse current blocking diode, 18 is a bias voltage control circuit that generates a bias voltage for the variable capacitance diode, 19, 2
0, 21, and 22 indicate a holding circuit having a memory function such as a flip-flop.

26 is a tuning coil 23 for VHF low band and vHF
A VHF tuner consisting of a high band tuning coil 24 and a variable capacitance diode 27 forming a resonant circuit with these tuning coils, 28 is a UHF tuner having a UHF tuning coil 25 and a variable capacitance diode 29,
The electronic tuner 17 consists of these VHF tuner 26 and UHF tuner 28.

16 is commonly connected to the UHF contacts of band preset switches 5 to 8, and is connected to the VHF tuner 2 according to the control signal.
This is a VHF/UHF switching control circuit that applies a power supply voltage (10 B) to the VHF tuner 6 and the UHF tuner 28 so that one of them operates.

30 is connected to the other contacts H and L of each of the band preset switches 5 to 8, and is connected to the VHF tuner 2 according to the control signal.
6, this is a high/low band switching control circuit that supplies high band and low band switching voltages.

In FIG. 1, when a channel selection instruction pulse is applied to the first input terminal 1, the output of the holding circuit 19, that is, the input signal of the high/low band switching control circuit 30, the VHF/UHF switching circuit 16, and the bias voltage control circuit 18 is positive. DC voltage is generated, the diode 9 is turned on, and applied to the high/low band switching control circuit 30 via the changeover switch 5, and the output voltage causes the VHF high channel tuning coil 24 of the tuner 17 to switch to a variable capacitance diode. 27
is combined with

At this time, the bias voltage control circuit 1
8 operates, a bias voltage corresponding to the first channel is obtained, which is applied to the variable capacitance diode 27, and by setting the capacitance to a predetermined value, a resonant circuit is formed with the high channel tuning coil 23, and the bias voltage corresponding to the first channel is obtained. 1 receiving station can receive.

Next, when a channel selection instruction pulse is applied to the second receiving station set to the low channel, the positive DC voltage of the bias voltage control circuit 18 is applied as in the above example, and at the same time, the DC voltage is applied to the band switching control circuit. A resonance circuit is configured by the low channel tuning coil 23 and the variable capacitance diode 27, and the second receiving station can receive the signal.

Furthermore, when a channel selection instruction pulse is applied to the input terminal 3 of the third receiving station set to the UHF channel, the positive DC voltage generated on the output side of the holding circuit 1 is applied to the bias voltage control circuit 18 and the VHF/UHF switching control circuit. 16, a variable capacitance diode 29 and a UHF tuning coil 25 constitute a resonant circuit.

A specific example of the VHF/UHF switching control circuit 16 is shown in FIG.

In Fig. 2, U of band preset switches 5 to 8 is
When a positive DC voltage is applied to the terminal 36 connected to the HF contact, the transistor 37 turns on when receiving UHF.
Along with this, the transistor 38 is also turned on, and the terminal 39
Since a positive DC voltage appears, this can be used as the B voltage for the UHF tuner.

On the other hand, in this case, the transistor 40 is off and the transistor 41 is also off, so the terminal 42 is at ground potential, and the B voltage is not applied to the VHF tuner connected to the next stage, keeping it in an inactive state.

When the terminal 36 is open, that is, when receiving a VHF station, the transistors 37 and 38 are off, and the transistors 40 and 41 are off, so the terminal 39 is at ground potential, while a positive voltage appears at the terminal 42, so that the B voltage of the VHF tuner ■Keep the HF tuner in working condition.

Further, a specific example of the high-low band switching control circuit 30 is shown in FIG.

When the output voltages of the holding circuits 19 to 22 are used via the band preset switch and a positive DC type voltage is applied to the terminal 31, the transistors 32 and 33 are turned on, a positive voltage is obtained at the terminal voltage 34, and the terminal 31 is opened. , 35, transistors 32 and 33 are both male and a negative voltage appears at terminal 34.

Therefore, if the voltage appearing at the terminal 34 is the control voltage,
The coil 23 or 24 can be selected.

The terminal 31 is connected to the high band contact H of the band preset switches 5 to 8, and the terminal 35 is connected to the low band contact H, but the other end of the terminal 35 is connected to the high band contact H of the band preset switches 5 to 8, and the other end of the terminal 35 is connected to the high band contact H of the band preset switches 5 to 8. is only connected to ground,
Since it is not related to the voltage generated at the output terminal 34, it can be omitted, and therefore the low band contact may not be connected anywhere.

As described above, in the present invention, a single circuit three-contact switch having contacts equal to the number of frequency bands of the channel to be selected is provided for each channel, and these are set in advance to desired positions, and the channel to be selected is set in advance. If the VCD bias voltage control circuit is set in accordance with Therefore, since tuning can be obtained, it is not necessary to provide as many band switching control circuits as there are channels.

Moreover, the VHF/UHF switching control circuit must switch and supply power of the same polarity to either the VHF tuner or the UHF tuner (semiconductor switches are connected to the power path to the VHF tuner and the power path to the UHF tuner, respectively).
The transistors 38 and 41) shown in Figure 2 are configured, and these semiconductor switching elements are configured to perform opposite switching operations using a common control signal, so that VHF
, : The circuit configuration for UHF switching becomes simple.

Furthermore, set the other contacts of the band preset switch to high.
It is connected to the drive of the low band switching control circuit, and switching between VHF and UHF and switching between VHF low band and high band can be easily set using the band preset switch of the -circuit 3 contact.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a channel selection device implementing the present invention. 2 and 3 are specific circuit diagrams showing a part of FIG. 1. 5-8...Band preset switch, 16.
...VHF, UHF switching control circuit, 17...
...Electronic tuning tuner, 18...Bias voltage control circuit, 19-22...Channel selection holding circuit, 26...VHF tuner, 28...
...vHF tuner, 30...High and low band switching control circuit, 38.41...Transistor with reverse switch operation.

Claims (1)

[Scope of utility model registration request] V with a voltage-responsive variable capacitance diode as a tuning element
An electronic tuning tuner consisting of an HF tuner and a UHF tuner, a bias voltage control circuit for supplying a tuning voltage to a voltage responsive variable capacitance diode of the electronic tuning tuner, and a bias voltage control circuit that takes two different states and outputs a tuning instruction signal. a plurality of channel selection and holding circuits each having a memory function that drives and holds the bias voltage control circuit so as to generate a predetermined voltage, which is set to the negative state in response to an applied voltage; Multiple band preset switches of the 1-circuit 3-contact type connected to each other,
A power supply of the same polarity must be switched and applied to either the VHF tuner or the UHF tuner (semiconductor switch elements are provided in the power supply path to the VHF tuner and the power supply path to the UHF tuner, respectively, and these semiconductor switch elements are A VHF/UHF switching control circuit connected to one specific contact of the band preset switch so as to perform mutually opposite switch operations using a common control signal, and a VHF tuner connected to the other contact of each of the band preset switches. A channel selection device for an electronic tuner consisting of a high and low band switching control circuit that supplies high band and low band switching voltages.