JPS6234291B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic tuning tuner that performs tuning by changing the voltage supplied to a variable cap used in radio receivers, television receivers, etc., and is particularly designed to be easy to use. be.

Conventionally, in radio receivers, television receivers, etc. that use electronically tuned tuners that use varicaps, the variable range of the tuning frequency due to the varicap is narrow, so the reception band must be switched (switching the coil of the tuning circuit, etc.) to achieve a predetermined value. It is possible to receive the following bands. For example, in a radio receiver, functions are switched between the SW band, AM band, and FM band, and in a television receiver, functions are switched between high and low bands of the VHF band.

In this case, in a conventional radio receiver or television receiver using an electronically tuned tuner using a varicap, in order to select a desired broadcasting station, the function is first switched to select the desired band. Next, the desired broadcasting station was selected by changing the tuning voltage. That is, in the conventional electronically tuned tuner, function switching was required in addition to supplying a tuning voltage, making the tuning operation that much more complicated.

In view of this point, the present invention is designed to simplify the tuning operation of an electronically tuned tuner using a varicap as described above.

Hereinafter, one embodiment of the electronic tuning tuner of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a radio receiver capable of receiving FM and AM bands. In Figure 1, 1 is an antenna, 2 is a high frequency amplification circuit, and 3
is a high frequency tuning circuit, 4 is a mixing circuit, 5 is a local oscillation circuit, 6 is an intermediate frequency amplification circuit, 7 is a detection circuit, 8
9 indicates an audio signal amplification circuit, and 9 indicates a speaker. The high frequency amplification circuit 2, high frequency tuning circuit 3, mixing circuit 4, local oscillation circuit 5, etc. constitute an electronic tuning tuner using a varicap. That is, the high frequency tuning circuit 3 connects the output side of the high frequency amplifying circuit 2 to ground via a series circuit of a DC blocking capacitor 3a and a varicap 3b constituting a variable capacitance element.
The connection point of the capacitor 3c for DC blocking, the connection switch 3d, and the AM band coil 3AM are grounded through a series circuit, and the connection of the capacitor 3c and the connection switch 3d is connected to the connection switch 3e and
Ground through the series circuit of FM band coil 3FM. In this case, when receiving the AM band, turn on the connection switch 3d, and configure the AM band tuning circuit with the varicap 3b and coil 3AM, and when receiving the FM band, turn on the connection switch 3e, and set the varicap 3b to the coil 3AM. The coil 3FM constitutes an FM band tuning circuit. Further, 5a indicates an oscillator constituting the local oscillation circuit 5, and a tuning circuit for determining the oscillation frequency of this oscillator 5a is composed of a variable cap 5b constituting a variable capacitance element and an AM band coil 5AM or
It is configured with FM band coil 5FM. That is, when receiving the AM band, the connection switch 5d is turned on, and the variable cap 5b and coil 5AM constitute a tuning circuit for obtaining a local oscillation signal for receiving the AM band, and when receiving the FM band, the connection switch 5e is turned on. With Varicap 5b and Coil 5FM as
A tuning circuit is configured to obtain a local oscillation signal for FM band reception. 5c and 5f are DC blocking capacitors, respectively.

Reference numeral 10 denotes a tuning voltage generating circuit, and this tuning voltage generating circuit 10 is constructed to generate a sawtooth wave voltage as shown in FIG. 2A. In this case, up button 1
When 0V is kept on, the output voltage of this channel selection voltage generation circuit 10 gradually increases, and after reaching the maximum voltage V _M of this sawtooth wave voltage, this output voltage instantly changes to the sawtooth wave voltage. When the down _button 10D continues to be turned on, the output voltage of the channel selection voltage generation circuit 10 gradually decreases, and this output voltage becomes a sawtooth voltage. After reaching the minimum voltage V _O of the wave voltage,
This output voltage is instantaneously the maximum voltage of the sawtooth voltage V
_M , and this voltage is made to gradually decrease again.

The output voltage of this channel selection voltage generation circuit 10 is supplied to the variable caps 3b and 5b, respectively, so that the capacitance values of each are changed. Also, in this case, the voltage is between the minimum voltage V _O and the maximum voltage V _M of the sawtooth wave voltage.
It is configured so that it can receive the entire AM band and FM band.

In this example, the output terminal of the channel selection voltage generating circuit 10 is connected to the trigger terminal T of the J-K flip-flop circuit 12 via a differentiator circuit consisting of a capacitor 11a and a resistor 11b, and a series circuit of a diode 11c. At the same time, the output terminal of this channel selection voltage generating circuit 10 is connected to the trigger terminal T of the JK flip-flop circuit 12 via an inverter circuit 13, a differentiator circuit consisting of a capacitor 11d and a resistor 11e, and a series circuit of a diode 11f. The J terminal and K terminal of this J-K flip-flop circuit 12 are respectively connected to a power supply terminal +B. Therefore, in this JK flip-flop circuit 12, each time a trigger signal is supplied to the trigger terminal T, the high level signal "1" and the low level signal "0" at the output terminal Q and the inverted output terminal are inverted, respectively.

The output terminal Q of this J-K flip-flop circuit 12 is connected via a resistor 14 to the base of a PNP transistor 15 constituting a switching element, and the emitter of this transistor 15 is connected to a power supply terminal +B to which a positive DC voltage is supplied. The signal obtained at the collector of this transistor 15 is supplied to the connection switches 3e and 5e as an on/off control signal, and the signal obtained at the FM switching signal output terminal 16 derived from the collector of this transistor 15 is used to output a signal. Change the system, display, etc.

In addition, the inverting output terminal of the J-K flip-flop circuit 12 is connected via a resistor 17 to the base of a pnp transistor 18 constituting a switching element, and the emitter of this transistor 18 is connected to the power supply terminal +B. The signal obtained at the collector is supplied to the connection switches 3d and 5d as an on/off control signal. In this case, when the inverted output terminal has a low level signal "0", the transistor 18 is turned on, and the connection switches 3d and 5 are turned on.
d is turned on and enters the AM band reception state,
Further, when the output terminal Q is a low level signal "0", the transistor 15 is turned on, the connection switches 3e and 5e are turned on, and a signal is obtained at the FM switching signal output terminal 16, so that the FM band reception state is established.

Since the present invention is configured as described above, now J.
The inverted output terminal of the -K flip-flop circuit 12 is at a low level "0" as shown in FIG. 2D, the transistor 18 is on, the connection switches 3d and 5d are on, and the AM band is being received. Assume that the output voltage of the channel selection voltage generating circuit 10 is V _AM , which is supplied to the variable caps 3b and 5b, respectively, and a predetermined AM broadcast is being received. In this case, press UP button 1 to receive other broadcasts.
When 0V is kept on, the output voltage of the channel selection voltage generation circuit 10 gradually increases along the slope of the sawtooth wave voltage for channel selection, as shown by arrow a in FIG. 2A, for example, and this voltage increases. After the sawtooth wave voltage for tuning reaches the maximum voltage V _M , that is, after reaching the maximum voltage for AM band tuning, the output voltage of the tuning voltage generation circuit 10 is as shown in FIG. 2A. decreases instantaneously to become the minimum voltage V _O of the sawtooth wave voltage for channel selection, and this output voltage gradually rises again along the slope of the sawtooth wave voltage as shown by arrow b. In this case, at the point where the output voltage drops instantaneously, a trigger signal as shown in FIG. The voltages at the output terminal Q and the inverted output terminal of the JK flip-flop circuit 12 are inverted as shown in FIG. 2C and D, and the output terminal Q becomes a low level signal "0". At this time, the transistor 15 is turned on and the transistor 18 is turned off, so the connection switches 3e and 5e are turned on, and a signal is also obtained at the FM switching signal output terminal 16, which is used to switch the signal system, display, etc. When the FM band reception state is reached and the desired broadcast station is received, if the up button 10V is turned off, the desired broadcast station can be continued to be received. The tuning voltage from the tuning voltage generation circuit 10 at this time is V _FM
Suppose it was. Thereafter, the down button 10D is turned on based on the reception state of this FM band, and when this state is continued, the output voltage of the tuning voltage generation circuit 10 becomes a sawtooth waveform for tuning, as shown by arrow c in FIG. 2A, for example. The voltage gradually decreases along the slope of the voltage, and after this voltage becomes the minimum voltage V _O of the sawtooth wave voltage for tuning, that is, the minimum voltage for FM band tuning, the voltage shown in Fig. 2A appears. As shown, this tuning voltage generation circuit 1
The output voltage of 0 instantaneously rises to the maximum voltage V _M of the sawtooth wave voltage for channel selection, and this output voltage gradually decreases again along the slope of the sawtooth wave voltage as shown by arrow d. In this case, at the point where the output voltage rises instantaneously, a trigger signal as shown in FIG. The voltages supplied to the terminal T, the output terminal Q and the inverted output terminal of this JK flip-flop circuit 12 are inverted as shown in FIG. 2C and D, and the inverted output terminal becomes a low level "0". At this time, the transistor 18 is turned on and the transistor 15 is turned off, so the connection switches 3d and 5d are turned on, respectively.When the desired broadcast station is received, if the down button 10D is turned off,
It is possible to continue receiving the desired broadcast station.
The channel selection voltage from the channel selection voltage generation circuit 10 at this time is assumed to be V _AM . Selection of other desired broadcast stations can be performed in the same manner as described above.

As described above, according to the present invention, for example, in a radio receiver capable of receiving AM band and FM band, a steep change point of the tuning voltage from the tuning voltage generation circuit 10 is detected and the reception band is i.e. AM
Since the band and FM band are automatically switched, there is no need for a band switching operation compared to the conventional method, which has the advantage of improving usability.

FIG. 3 shows a channel selection voltage generating circuit 10 which manually generates a sawtooth wave voltage. In FIG. 3, for example, a part of a circular resistor 10a is cut out, one end of this cutout is grounded, and the other end is connected to a power supply terminal +B to which a positive DC voltage is supplied.
A slider 10b is provided, one end of which is pivotally supported at the center of the circular resistor 10a, and the other end of which slides on the circular resistor 10a.
In order to obtain a higher channel selection voltage. By using such a variable resistor as shown in FIG. 3, a sawtooth wave voltage as shown in FIG. 2A can be obtained.

In the above embodiment, the radio receiver's AM
Although the example of switching between bands and FM bands has been described, it goes without saying that it can also be used for switching between other bands, such as switching between high and low bands of the VHF band of a television receiver.

Moreover, the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations may be adopted without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the electronic tuning tuner of the present invention, FIG. 2 is a diagram for explaining the present invention, and FIG. 3 is a block diagram showing another example of the tuning voltage generating circuit. . 2 is a high frequency amplifier circuit, 3 is a high frequency tuning circuit, 4
5 is a mixing circuit, 5 is a local oscillation circuit, 3b and 5b are variable caps, 3d, 3e, 5d and 5e are connection switches, 3AM, 3FM, 5AM and 5
FM is a coil respectively, 10 is a tuning voltage generation circuit, 1
1a, 11d and 11b, 11e are capacitors and resistors respectively forming a differential circuit, 12 is J-K
It is a flip-flop circuit.

Claims (1)

[Claims] 1. In an electronic tuning tuner that performs tuning by supplying a sawtooth voltage to the variable cap, it is possible to automatically switch the receiving band by detecting a steep change point in the sawtooth voltage. Features an electronic tuning tuner.