JPH0215404Y2 - - Google Patents

Description

[Detailed Description of the Invention] Field of the Invention The present invention is an electronic tuning receiver, in particular, a variable resistor for tuning the tuning circuit by controlling the voltage from the variable resistor for manual tuning or the preset tuning means through a manual/preset changeover switch. The present invention relates to an electronic tuning receiver that selectively applies voltage to a reactance element.

Prior Art As this type of electronic tuning receiver, a circuit as shown in FIG. 1 is conventionally known.

In Figure 1, 1 is the oscillation tuning circuit of the FM receiver, VC ₁ and VC ₂ are voltage variable reactance elements that constitute the oscillation tuning circuit 1, such as variable capacitance diodes, and R ₁ is the variable capacitance diode VC ₁ at one end. , VC ₂ is a bias resistor, C ₁ is a high frequency blocking capacitor with one end grounded, S ₁ is a manual
Preset changeover switch, D ₁ is the common contact COM and resistor of manual preset changeover switch S ₁ .
This diode is connected between the other end of _R1 and is a temperature compensation diode for compensating the temperature characteristics of the variable capacitance diodes _VC1 and _VC2 . _C2 is a noise filter capacitor connected in parallel to diode _D1 . Furthermore, the other end of resistor _R1 is a capacitor.
It is connected to the other end of C ₁ and is also connected to a high frequency amplification circuit or an antenna circuit (none of which is shown). C ₃ is a hum filter capacitor with one end connected to the common contact COM of manual preset switch S ₁ and the other end grounded.
is a transistor for discharging capacitor _C3 .
VR ₁ , R ₂ , and SVR ₁ are variable resistors and resistors for manual channel selection connected in series between the positive power supply voltage supply line 2 and ground 3, and semi-fixed resistors for correcting variations in the minimum voltage during manual channel selection. The movable terminal 4 of the manual selection variable resistor _VR1 is connected to the manual side fixed contact MAN of the manual preset changeover switch _S1 via a resistor _R3 . r ₁ is a resistance for correcting variations in variable resistor VR ₁ .
VR ₂ , VR ₃ , VR ₄ , R ₄ , R ₅ , R ₆ variable resistors and resistors for preset adjustment, r ₂ , r ₃ , r ₄ are for correcting variations in each variable resistor VR ₂ , VR ₃ , VR ₄ The series circuits 5, 6, and 7 of the preset adjustment variable resistors VR ₂ , VR ₃ , and VR ₄ and the resistors R ₄ , R ₅ , and R ₆ are connected to the power supply line 2 and the anode of the diode D ₄ , respectively. and the cathode of diode _D4 is grounded. R ₇ , R ₈ , SVR ₂ , and D ₅ are two resistors connected in series between the power voltage supply line 2 and the ground 3, a semi-fixed resistor for setting the lowest voltage during preset channel selection, and a diode. S ₂ , S ₃ , and S ₄ are multiple channel selection switches, and these channel selection switches and manual preset changeover switch S ₁ are interlocked with each other, so that only one of these switches is set to the upper side. It is configured so that And each channel selection switch _S2 ,
The ON side (upper side) fixed contacts of S ₃ and S ₄ are connected to the respective movable terminals 8, 9, and 10 of the variable resistors VR ₂ , VR ₃ , and VR ₄ for preset adjustment, and the first channel selection switch S ₂ A first voltage selection diode is connected between the common contact (point a) of the manual preset switch S1 and the preset side fixed contact PRE of the manual preset changeover switch _S1 .
D ₂ is connected. Further, a second voltage selection diode _D3 is connected between the connection point (point b) of the resistors _R7 and _R8 and the preset side fixed contact PRE of the manual preset changeover switch _S1 .

In the electronic tuning receiver of FIG. 1 constructed in this manner, the diode D ₁ is replaced by a variable capacitance diode VC ₁ ,
This is for temperature compensation of VC ₂ and is absolutely necessary for the circuit. On the other hand, the diodes _D2 to _D5 are unnecessary from the viewpoint of temperature compensation of the variable capacitance diodes _VC1 and _VC2 . However, the resistance values of variable resistors VR ₂ , VR ₃ , and VR ₄ for preset adjustment are near the lowest value.
There is a problem in that the resistance does not gradually increase from 0Ω, but suddenly jumps from 0Ω to a predetermined resistance value, and the reception frequency also jumps, so diodes D ₂ to D ₅ are required as a countermeasure.

In other words, when the first channel is selected during preset tuning (when each switch is set to the position shown in Figure 1), the voltage at the common contact (point a) of the first channel selection switch _S2 is preset adjusted. determined by variable resistor VR ₂ , resistor R ₄ , and diode D ₄ for variable resistor VR ₂
When the movable terminal 8 of is set to the lowest position,
A voltage determined by the ratio of the volume VR ₂ and the resistor R ₄ appears at point a. If you adjust the resistors R ₇ and R ₈ and the semi-fixed resistor SVR ₂ for setting the minimum voltage so that the voltage at the connection point (point b) is higher than the voltage at point a, the diode D ₂ will be in the OFF state. becomes. (However, the ON voltage of diode D ₂ = ON voltage of diode D ₃
Voltage). Therefore, the variable capacitance diode of tuned circuit 1
The voltage set by the resistors R ₇ and R ₈ and _{the semi-fixed resistor SVR 2 for} setting the lowest voltage is applied to VC 1 and VC ₂ , and the preset volume (VR ₂ )
It is unrelated to the resistance value of Next, when the movable terminal 8 of the preset variable resistor VR ₂ is gradually moved higher, from the point where (voltage at point a ≧ voltage at point b), the resistors R ₇ and R ₈ and the semi-fixed resistor SVR ₂ becomes irrelevant, and the voltage adjusted by the preset variable resistor VR ₂ is applied to the variable capacitance diodes VC ₁ and VC ₂ .

In this way, the preset variable resistor VR ₂ ,
Although frequency jumps near the lowest positions of VR ₃ and VR ₄ are prevented, the first and second voltage selection diodes D ₂ ,
Since the temperature drift changes by inserting D ₃ , diodes D ₄ and D ₅ are additionally required for compensation.

Note that during manual channel selection, the voltage adjusted by the manual adjustment variable resistor VR ₁ is applied to the variable capacitance diodes VC ₁ and VC ₂ .

In addition, the variable resistor VR ₁ for manual channel selection also has a discontinuity point near the lowest position, but the ones that are generally commercially available as variable resistors for manual channel selection are
There is no problem because the movable terminal is restricted from moving completely to the lowest position. Also, although there are discontinuities in variable resistors even near the highest position, this is a problem because the frequency change in response to a voltage change near the highest position of the variable resistor is much smaller than that near the lowest position of the variable resistor. Not.

Also, when switching the channel from a high frequency channel to a low frequency channel using the channel selection switch, _the capacitor _C3 for the hum filter must be discharged. If it is not provided, the impedance of the discharge path of capacitor C ₃ will be quite high, so even if you operate the channel selection switch to switch from a high frequency channel to a low frequency channel, capacitor C ₃ will be difficult to discharge. It is difficult to settle on the desired voltage. Therefore, in the circuit shown in Figure 1, a transistor Q is provided for forced discharge, and the moment the channel selection switch is operated, a control signal is applied to the base of the transistor Q to turn on the transistor Q, forcing the capacitor _C3 . I am trying to make it discharge.

Problems with the conventional technology The circuit shown in Figure 1 uses five diodes for temperature compensation and frequency jump countermeasures.
This method not only requires a large number of parts, which increases costs, but also has the disadvantage that temperature compensation errors due to variations between parts become large. Further, in the circuit shown in FIG. 1, a transistor for forced discharge must be used, and the capacitor for the hum filter is also limited to a capacitance as small as possible.

Purpose of the invention The purpose of the present invention is to provide an electronically tuned receiver that reduces the number of parts and eliminates the above-mentioned drawbacks.

Embodiment of the Invention FIG. 2 is a circuit diagram showing an embodiment of the electronic tuning receiver of the invention. In FIG. 2, the same parts as in FIG. 1 are designated by the same numbers as in FIG.

In the circuit shown in FIG. 2, the manual preset changeover switch is composed of two circuits consisting of a first circuit _S'1 and a second circuit _S''1 which are interlocked so that they are always set to the same side. and the first circuit S′ ₁
In this case, the fixed contact MAN on the manual side is connected to the movable terminal 4 of the variable resistor VR ₁ for manual station via the resistor R ₃ , and the fixed contact PRE on the preset side is connected to the common contact (point a) of the channel selection switch S ₂ . The common contact COM is connected to the anode of the first diode _D6 and one end of the first hum filter capacitor _C4 , respectively. On the other hand, in the second circuit _S''1 of the manual preset changeover switch, the common contact COM is connected to the connection point (point b) of resistors _R7 and _R8 connected in series to the semi-fixed resistor _SVR2 , and the preset side is fixed. The contact (PRE) is the second diode D ₇
capacitor for the anode and second hum filter
Each is connected to one end of _C5 , and the fixed contact MAN on the manual side serves as an idle contact. Further, the cathodes of the first and second diodes D ₆ and D ₇ are connected to the voltage variable capacitance diodes VC ₁ and VC ₂ via the resistor R ₁ ,
The other ends of the first and second hum filter capacitors C ₄ and C ₅ are grounded. The manual preset changeover switches S' ₁ and S'' ₁ are linked with the channel selection switches S ₂ to _S4 , and either one of the channel selection switches S ₂ to S ₄ or the manual preset changeover switch S' _{1 is} operated. , S″ ₁ is configured so that only 1 is set on the upper side.

In the circuit shown in Figure 2, only the first and second diodes D ₆ and D ₇ are used as diodes for temperature compensation and frequency jump countermeasures. Next, the operation of the circuit shown in Figure 2 will be explained. .

In the circuit shown in Figure 2, the manual preset changeover switches S' ₁ and S'' ₁ are connected to the fixed contacts on the manual side.
When set to the MAN side (manual tuning), the first diode _D6 is used to compensate for the temperature of the variable capacitance diodes _VC1 and _VC2 of the tuning circuit 1.

On the other hand, manual preset selector switch S′ ₁ ,
When S″ ₁ is set to the preset side fixed contact PRE side (when selecting a preset station), the first diode
Either D ₆ or second diode D ₇ turns ON, and the voltage adjusted by the preset adjustment variable resistor of the selected channel or the set voltage is tuned by the minimum voltage setting semi-fixed resistor SVR ₂ . circuit 1
is applied to the variable capacitance diodes VC ₁ and VC ₂ .
At this time, the one of the first diode D ₆ and the second diode D ₇ that is turned on serves also as temperature compensation for the variable capacitance diodes VC ₁ and VC ₂ .

In this way, in the circuit shown in Figure 2, during manual tuning, the first diode _D6 is used as a variable capacitance diode.
It performs temperature compensation for VC ₁ and VC ₂ , and also selects the voltage to be applied to the variable capacitance diodes VC 1 and VC 2 using the first and second diodes D ₆ and D ₇ during preset tuning, and selects the voltage to be applied to the variable capacitance diodes VC _{1 and} VC _2. , and VC ₂ temperature compensation. Therefore, while the number of diodes used for temperature compensation and measures against frequency jumps was five in the conventional circuit of FIG. 1, it can be reduced to two in the circuit of FIG. Also, when switching channels, one of the resistors is connected in parallel to the hum filter capacitors C ₄ and C ₅ via a switch, and when switching from a high frequency channel to a low frequency channel, the capacitors C ₄ and C ₅ is discharged through this resistor. Therefore, the forced discharge means, e.g.
Discharge transistor Q used in the conventional circuit shown in the figure
is no longer necessary, and the hum filter capacitor _C4 ,
It is also possible to use _C5 with a larger capacitance value than that used in conventional circuits [for example, the first
In the conventional circuit shown in the figure, only a capacitor of about 3.3 μF can be used as the capacitor _C3 , but in the circuit of FIG. 2, a capacitor of about 10 μF can be used as the capacitors _C4 and _C5 . It is also effective against hum, which is a common problem in receivers.

In this type of electronically tuned receiver, a widely used two-circuit multiple push switch is often used as a manual preset changeover switch and a channel selection switch that operate in conjunction with each other. When such a multiple push switch with two circuits is used, in the conventional circuit shown in FIG. 1, only the first circuit is used and the second circuit is idle. On the other hand, in the circuit shown in Fig. 2, the switches used as manual preset changeover switches are the first circuit _S'1 and the second circuit _S''1.
Both are used effectively. Therefore, when a two-circuit multiple push switch is used as a manual preset changeover switch and a channel selection switch, the circuit shown in Figure 2 is less advantageous in terms of switch cost than the conventional circuit shown in Figure 1. There's no way it will happen.

In the embodiment shown in Fig. 2, a semi-fixed resistor SVR ₂ is used to set the minimum voltage during preset channel selection, but a variable resistor or a fixed resistor may be used instead of the semi-fixed resistor. good.

Effects of the invention As described above, according to the electronically tuned receiver according to the invention, the number of diodes can be significantly reduced for temperature compensation and measures against frequency jumps, so the circuit configuration can be simplified. Furthermore, errors in temperature compensation due to variations between parts can be reduced as much as possible. Furthermore, when using a hum filter capacitor, there is no need to provide a special discharging circuit for the hum filter capacitor, and a hum filter capacitor with a relatively large capacity can be used, which is effective as a countermeasure against hum. There are advantages.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional electronic tuning receiver;
FIG. 2 is a circuit diagram showing an electronic tuning receiver according to the present invention. S′ ₁ , S″ ₁ ... First circuit and second circuit of manual preset changeover switch, VR ₁ ... Variable resistor for manual channel selection, VR ₂ , VR ₃ , VR ₄ ... Variable resistor for preset adjustment SVR ₂ ... Semi-fixed resistor for minimum voltage setting, D ₆ , D ₇ ... First and second diodes, C ₄ , C ₅ ... First and second hum filters,
VC ₁ , VC ₂ ... Variable capacitance diode, 1 ... Tuning circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) Equipped with a fixed contact on the manual side, a fixed contact on the preset side, and a common contact, the fixed contact on the manual side serves as a variable resistor for manual channel selection, and the fixed contact on the preset side serves as a switch for channel selection. a first circuit connected to the variable resistor for preset adjustment via the same, and a fixed contact on the manual side;
A second circuit comprising a fixed contact on the preset side and a common contact, the common contact being connected to a minimum voltage setting resistor during preset channel selection, and interlocking with the first circuit.
A manual having a circuit, wherein the first and second circuits are interlocked with the channel selection switch, and when the channel selection switch is set to the off side, the manual side fixed contact is set. - a preset changeover switch, a first diode whose anode is connected to the common contact of the first circuit, and whose cathode is connected to the voltage variable reactance element of the tuned circuit, and whose anode is connected to the preset side fixed contact of the second circuit; , a second diode whose cathode is connected to the connection point of the cathode of the first diode and the voltage variable reactance element, respectively,
During manual tuning, the voltage adjusted by the manual tuning variable resistor is applied to the voltage variable reactance element via the first diode, and during preset tuning, the voltage adjusted by the preset adjustment variable resistor is applied to the voltage variable reactance element through the first diode. Alternatively, the voltage set by the minimum voltage setting resistor is selectively applied to the voltage variable reactance element by the first and second diodes, and at the time of manual channel selection, the first diode is applied to the voltage variable reactance element. An electronic tuning receiver characterized in that, during preset tuning, temperature compensation of the voltage variable reactance element is performed by the first or second diode. (2) 1st manual preset switch
A first hum filter capacitor is connected between the common contact of the circuit and ground, and a fixed contact on the preset side of the second circuit of the manual preset changeover switch is connected to the ground.
2. The electronic tuning receiver according to claim 1, wherein a second hum filter capacitor is connected between the ground and the ground. (3) The electronic tuning receiver according to claim 1, wherein the voltage variable reactance element is a variable capacitance diode.