JPH0317465Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a preset tuner with a manual tuning function.

(Prior art and its problems) Figure 2 shows an example of a conventional preset tuner, in which 1 is an antenna, 2 is a high frequency amplifier circuit, 3 is a tuning circuit, _D1 is a tuning coil _L1 , and a capacitor C ₁ is a tuning varicap diode for selecting a desired frequency; 4 is a local oscillation circuit; D ₂ is a local oscillation coil L ₂ ; together with capacitor C ₂ , a local oscillator varicap is used to vary the oscillation frequency of the local oscillator 5. A cap diode, 6 is a mixing circuit that mixes the tuned frequency with the local oscillation frequency and converts the frequency, 7 is an intermediate frequency amplification circuit, 8 is a detection circuit, 9 is a
The stereo signal from the FM detection output is separated into a left channel signal and a right channel signal, respectively.
Output to left and right channel output terminals LO and RO
This is an FM stereo demodulation circuit.

Reference numeral 10 designates a control voltage preset circuit for adjusting the control voltage applied to the tuning varicap diode D ₁ and the local oscillator varicap diode D ₂ to a voltage corresponding to the receiving frequency. It consists of fixed resistors VR ₁ to VR ₆ , and by dividing the reference voltage Vref by these semi-fixed resistors, a control voltage corresponding to each receiving frequency is set.

_VRM is a variable resistor for manual tuning, and is designed to be able to vary the control voltage applied to the varicap diode in order to continuously vary the receiving frequency within the receiving frequency band.

11 are semi-fixed resistors VR ₁ to VR ₆ of the preset circuit and variable resistors VR _M for manual channel selection so as to be controllable.
This is a preset switch group consisting of preset switches _S'M , _S'1 to _S'6 for selectively connecting the tuning varicap diode _D1 and the local oscillator varicap diode _D2 .

These preset switches are all mechanically related, and are used in the preset switches of ordinary preset type tuners, where pressing one of the switches restores the previously pressed switch. be. By selectively operating these preset switches, the receiving frequency can be switched to a station corresponding to the control voltage set by the selected semi-fixed resistor or variable resistor.

Looking at the connection relationship of each preset switch _S'M , _S'1 to _S'6 , each switch has a fixed contact _S'Ma , S'1 _-a to
S′ _6-a , S′ _Mb , S′ _1-b ~ S′ _6-b , and common contact S′ _Mc
，
Consists of S′ _1-c to S′ _6-c , with upper fixed contact
S′ _Ma , S′ _1-a to S′ _6-a are opened at the non-operating side contacts,
The lower fixed contacts S′ _Mb , S′ _1-b to S′ _6-b are variable resistors for manual channel selection VR _M and preset semi-fixed resistors, respectively.
Connected to the mover of VR ₁ to VR ₆ , and also a common contact
S' _Mc , S' _1-c to S' _6-c are connected to the cathodes of the tuning varicap diode D ₁ and the local oscillator varicap diode D ₂ , respectively.

Therefore, each preset switch S′ _M , S′ ₁ ~
By operating _S'6 , the movable element of the semi-fixed resistor for preset or variable resistor for manual tuning corresponding to the operated switch is connected to the cathode of the variable cap diode for tuning and local oscillation, and the switch is connected to the cathode of the variable cap diode for tuning and local oscillation. A control voltage is applied, and a receiving frequency can be set according to the control voltage.

The above shows the configuration of a conventional preset tuner. Generally, the switches used in a preset switch are mechanically related to each other, and operating one switch will cause the other switches that have already been operated to be activated. is returned to the non-operating position, and each switch is always selectively set one by one to the operating position.

However, if the pressure on the switch is insufficient and shallow, even if a switch that has already been pressed returns, the pressed switch will not be locked in the operating position, and all switches may become inoperable. When all the preset switches return to their non-operated positions, the tuning and local variable cap diodes D ₁ and D ₂ are disconnected from any of the preset semi-fixed resistors and variable resistors, and the receiving frequency is As a result, inter-office noise and the like are outputted to the tuner output, causing extreme discomfort to the user.

(Purpose of the invention) It is an object of the present invention to solve the above-mentioned problems and to prevent the received frequency from becoming unstable and noise from being output even if all the preset switches of the tuner are in the non-operating position.

(Summary of the invention) The present invention provides a tuning circuit and a local oscillation circuit that vary the tuning frequency and local oscillation frequency by varying the control voltage of the varicap diode, and a tuning circuit and a local oscillation circuit that vary the control voltage of the varicap diode. A plurality of semi-fixed resistances for preset tuning set for each receiving station, a variable resistor for manual tuning that continuously varies the control voltage of the variable cap diode within the reception band, and a variable resistor for manual tuning. In a preset tuner equipped with a plurality of preset switches that selectively switch and connect a resistor and the plurality of preset semi-fixed resistances, the preset switch has a first preset switch connected to the preset semi-fixed resistance. , a second fixed contact on the non-operating side of the switch, and a common contact, and when the preset switch is in the non-operating position, the preset switch is connected through the common contact and the second fixed contact. The preset switches are connected in series with each other to form a path connecting the variable resistor for manual tuning to the variable cap diode, and when any of the preset switches is operated, the path is cut off and the Since the preset channel selection semi-fixed resistor corresponding to the preset switch is connected to the variable cap diode through the fixed contact No. 1, all the preset switches become inoperable. The system is designed to switch to manual channel selection mode.

(Embodiment) FIG. 1 shows an embodiment of the preset tuner of the present invention, and the same reference numerals will be used to explain the same parts as in the conventional example shown in FIG.

antenna 1, high frequency amplification circuit 2, tuning circuit 3,
The basic configuration of the tuner is the same as the conventional one, consisting of a local oscillation circuit 4, a mixing circuit 6, an intermediate frequency amplification circuit 7, a detection circuit 8, an FM stereo demodulation circuit 9, and a set voltage preset circuit 11 that sets a control voltage according to each reception frequency. The same applies to the point that the reception frequency is tuned by the tuning and local varicap diodes D ₁ and D ₂ .

On the other hand, looking at the preset switch group 12 for performing the channel selection operation, the preset switches S _M ,
Consisting of S ₁ to _{S 6} , the lower fixed contacts S _Mb and S _1-b to _{S 6-b} , which are on the operating position side of each switch, are variable resistors VR _M for manual tuning and semi-fixed resistors for presetting, respectively.
Connected to movers VR ₁ to VR ₆ , switch _SM ,
The common contacts S _Mc , S _{1 -c} to _{S 5-c of S 1 to S 5 are} the upper fixed contacts S ₁ -a to S ₆ -a, which are on the non-operating position side of the adjacent switches S ₁ to S _6, respectively. are connected sequentially. In other words, the common contact S _Mc of switch S _M is
Fixed contact S _1-a of S ₁ , common contact S _1-c of switch S ₁
are sequentially connected to the fixed contact S _2-a of the switch S ₂ , and so on.

The common contact S _6-c of the last switch S ₆ is connected to the tuning and local varicap diodes D ₁ , D ₂
connected to the cathode of the manual tuning switch.
The upper fixed contact S _Ma of S _M is connected to the lower fixed contact S _Mb .

Therefore, the state in which the movable elements of each switch S _M , S ₁ to _{S 6} are all switched to the upper fixed contacts S _Ma , S _1-a to _{S 6-a} , that is, all of the problems in this invention When the preset switches S M and S 1 to S 6 are switched to the non-operating position, the preset switches S _M , S ₁ to _{S 6} are connected in series to each other via each movable element, and the variable resistor VR for manual channel selection is _M
The movable element is connected to variable cap diodes D ₁ and D ₂ for tuning and local oscillation, and a variable resistor for manual tuning.
The reception frequency is tuned according to the control voltage obtained by dividing the reference voltage Vref by _VRM .

Therefore, if all the preset switches become inoperable due to incomplete or shallow pressing of the preset switches, the manual selection mode will be selected and the received frequency may become unstable. and does not cause discomfort to the user.

In normal use, when any preset switch is pressed, the mover of the pressed switch switches from the upper fixed contact on the non-operating side to the lower fixed contact on the operating side. The semi-fixed resistance mover corresponding to the pressed switch is connected to the tuning and local varicap diodes D ₁ and D ₂ .

Figure 1 shows the case where the preset switch _S1 is pressed, and the movable element connects the common contact S1 _-c and the lower fixed contact S1 _-b to set the preset semi-fixed switch. Switches S ₂ to _{S 6} with adjacent resistors VR ₁
It is connected to the tuning and local varicap diodes D ₁ and D ₂ via , and the reception frequency corresponds to the set control voltage.

In other words, when one of the preset switches is operated, the path connecting that switch and the corresponding semi-fixed resistor or variable resistor for manual tuning to the variable cap diode is the common contact point of each preset switch mentioned above and their This is a path in which the upper fixed contacts of the switches adjacent to the switch are connected in series in sequence, and by pressing either preset switch, the switch to the left of that switch is disconnected from the above path, and the operated switch is disconnected from the above path. can be seen as being prioritized. In other words, the priority of each preset switch is higher as it is located further to the right in FIG. 1, that is, closer to the varicap diodes D ₁ and D ₂ . Therefore, contrary to the above, even if multiple preset switches are pressed at the same time, the above-mentioned paths are separated by operating the switch closest to the tuning and local variable cap diodes. , switches located to the left of this are irrelevant and the receiving frequency will not become undefined. When all the preset switches are activated at the same time, only the preset switch _S6 is relevant, and the positions of the other switches are irrelevant.

Therefore, with the preset tuner of the present invention, the received frequency never becomes unstable, regardless of the operating state of the preset switch.

Additionally, regarding the case where multiple preset switches are operated at the same time, in the conventional example shown in Figure 2, all semi-fixed resistors or variable resistors corresponding to the operated switches are connected in parallel to the variable cap diode. However, according to the present invention, no matter how many times the preset switch is pressed, Since only the preset switch closest to the varicap diode is always selected, there is no problem not only in terms of receiving frequency but also in terms of current capacity.

(Effects of the invention) According to the preset tuner of the present invention, all the preset switches are connected in series with each other when they are in the non-operated state, and the varicap diodes for tuning and local oscillation of the tuning circuit and local oscillator circuit are manually connected. Since a path is formed to connect the variable resistor for channel selection, even if all the preset switches return to their non-operated positions due to insufficient pressing of the preset switches, manual switching is possible. Since it enters the tuning mode and the received frequency does not become unstable, it does not cause discomfort to the user, and all preset switches, which have traditionally been a problem with preset tuners, are not operated. It is possible to solve the problem that the receiving frequency becomes unstable when the receiver reaches a certain position.

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram showing one embodiment of a preset type tuner of the present invention, and FIG. 2 is a circuit connection diagram showing an example of a conventional preset type tuner. Explanation of symbols, 3... Tuning circuit, 4... Local oscillation circuit, 10... Control voltage preset circuit, 12...
...Preset switch group, D ₁ ... Varicap diode for tuning, D ₂ ... Varicap diode for local oscillation, S _M , S ₁ to _{S 6} ... Preset switch, VR _M ... Variable for manual tuning Resistance, VR ₁ ~ VR ₆ ...
...Semi-fixed resistor for preset.

Claims (1)

[Scope of utility model registration request] A tuning circuit and a local oscillation circuit configured to vary the tuning frequency and local oscillation frequency by varying the control voltage of the varicap diode, and a plurality of circuits for setting the control voltage of the varicap diode for each receiving station. a semi-fixed resistor for preset tuning; a variable resistor for manual tuning that continuously varies the control voltage of the varicap diode within the receiving frequency band; the variable resistor for manual tuning and the plurality of preset tuning resistors; In a preset type tuner equipped with a plurality of preset switches that selectively switch and connect a semi-fixed resistor for presetting, the preset switch has a first fixed contact connected to a semi-fixed resistor for presetting, and a non-fixed contact of the switch. The preset switch has a second fixed contact on the operating side and a common contact, and when the preset switch is in a non-operating position, the preset switch is connected in series with each other via the common contact and the second fixed contact. connected to form a path connecting the variable resistor for manual tuning to the variable cap diode,
When any preset switch is operated, the path is cut off, and a semi-fixed resistor for preset tuning corresponding to that preset switch is connected to the variable cap diode via the first fixed contact. A preset tuner that is characterized by the following.