JP2008244777A - Tuning circuit, and electronic device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in the conventional tuning circuit in which a frequency characteristic of an output voltage is a single peak characteristic and which is weak against noise having a frequency component close to a received frequency. <P>SOLUTION: A tuning circuit is connected in parallel to an antenna, and configured of a tuner section and a filter section connected in parallel. A filter circuit has a predetermined resonant frequency. With such the configuration, the frequency characteristic of the output voltage is not a single peak characteristic, but has a minimum value in the resonant frequency of the filter section. It is possible to suppress sensitivity to a particular noise, while keeping the output voltage relative to the frequency of a desired signal. As a result, the proportion of noise included in the output voltage can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a tuning circuit for receiving a predetermined radio wave including various information using an antenna, and an electronic apparatus having the tuning circuit.

Tuning circuits for receiving predetermined radio waves containing various information and electronic devices equipped with such tuning circuits are widely distributed, and radios, radios, mobile phones, radio wave correction watches, etc. are widely known. .
Among them, for example, a radio correction clock is a clock having a function of receiving a standard radio wave (eg, 40 kHz radio wave) including time information and date information and correcting a time error. The standard time signal can be received arbitrarily by the user and automatically, so it is always accurate compared to a quartz watch that always produces errors due to temperature differences or the presence or absence of vibration. In recent years, it has been rapidly spreading as a watch that can be displayed and can save time and effort.

Generally, a tuning circuit is configured by an antenna and a tuning unit connected in parallel, and various techniques have been proposed for the configuration (see, for example, Patent Document 1).
The prior art disclosed in Patent Document 1 will be described with reference to FIGS. FIG. 13 is a diagram obtained by simplifying the prior art disclosed in Patent Document 1 within a range in which the gist thereof does not change. In FIG. 13, 1 is an antenna and 2 is a tuning unit. In this tuning circuit, the voltage appearing at both ends of the antenna 1 is taken out as an output. This voltage is called an output voltage Vout.

FIG. 14 is a diagram schematically illustrating frequency characteristics of the conventional tuning circuit disclosed in Patent Document 1. In FIG. In FIG. 14, the horizontal axis indicates the frequency, and the vertical axis indicates the amplitude of the output voltage Vout of the tuning circuit at each frequency when a radio wave having a certain intensity is received.
The output voltage Vout exhibits a unimodal characteristic that is maximized when the reception frequency is equal to the frequency f1 and decreases as the reception frequency goes away from the resonance frequency. At this time, the frequency f1 is the resonance frequency of the antenna 1 and the tuning unit 2, and is determined by the constants of the antenna 1 and the tuning unit 2. The frequency f3 will be described later.

  As can be seen from the frequency characteristics shown in FIG. 14, the tuning circuit has frequency selectivity. That is, by adjusting the frequency f1 to the frequency to be received, the frequency to be received is output as a large output voltage, and other frequencies hardly appear in the output voltage. Hereinafter, a radio wave having a frequency desired to be received is called a signal radio wave, and an output voltage Vout generated thereby is called a signal voltage. Further, a radio wave having a frequency that is not desired to be received other than a signal radio wave is called a noise radio wave, and output power Vout generated thereby is called a noise voltage.

Here, the reason for having the frequency selectivity will be described with reference to FIG. FIG. 14 shows the frequencies f1 and f3. The characteristic shown in FIG. 14 has the same intensity as the signal radio wave with a certain intensity and the frequency f1, but the frequency is superimposed with a noise radio wave having a frequency f3 close to the frequency f1. It is an example.
When such a radio wave is received, the output voltage Vout of the tuning circuit is a voltage in which a noise voltage having an amplitude v3 and a frequency f3 is superimposed on a voltage signal having an amplitude v1 and a frequency f1.
However, since the amplitude v3 is sufficiently smaller than the amplitude v1, the output voltage Vout is almost equal to the signal voltage. That is, in the output voltage Vout, the ratio of the noise voltage to the signal voltage can be suppressed small.

Japanese Patent Laid-Open No. 2003-234642 (2nd page, FIG. 2)

The prior art shown in Patent Document 1 gives the tuning circuit frequency selectivity and has the effect of suppressing the ratio of the noise voltage in the output voltage Vout to a small value. It has been found that there is a problem that it is vulnerable to noise having a frequency component close to. The problem is particularly noticeable when the frequency selectivity is low.
That is, when the frequency selectivity is insufficient, noise having a frequency component close to the frequency to be received is output as the output voltage Vout.

Such a situation will be described with reference to the drawings. FIG. 15 is a diagram schematically showing changes in the frequency characteristics of the output voltage Vout, and shows the frequency characteristics of the output voltage Vout.
In FIG. 15, the horizontal axis indicates the frequency, and the vertical axis indicates the amplitude of the output voltage Vout of the tuning circuit at each frequency when a radio wave having a certain intensity is received.
In FIG. 15, 52a indicates the frequency characteristic when the frequency selectivity is good, and 52b indicates the frequency characteristic when the frequency selectivity is bad. The frequency characteristic 52b has a smaller peak slope than the frequency characteristic 52a. That is, the output voltage Vout is generated even for radio waves other than the target frequency, and therefore it can be said that the frequency selectivity is poor.

  The frequency characteristic of the output voltage Vout of the tuning circuit varies depending on the constant between the antenna and the capacitance. In the example shown in FIG. 13, this is a constant with the capacitance of the capacitor mounted on the tuning unit 2 connected in parallel with the antenna 1. For example, when the resistance component of the antenna is large, the frequency characteristic of the output voltage Vout is the frequency characteristic 52b shown in FIG.

  The influence of the decrease in frequency selectivity on the output voltage Vout of the tuning circuit will be described by taking as an example a case where a radio wave in which a noise radio wave is superimposed on a signal radio wave to be received is received. Consider a case where a radio wave in which a noise radio wave having the same intensity and frequency f4 is superimposed on a signal radio wave having a certain intensity and frequency f1 is received.

In the tuning circuit having the frequency characteristic 52a, the output voltage Vout output from the tuning circuit is superimposed on the signal voltage having the amplitude v1 and the frequency f1 by the noise voltage having the amplitude v4 and the frequency f4. Will do.
On the other hand, in the tuning circuit having the frequency characteristic 52b, when receiving a radio wave in which a noise radio wave having the same intensity and the frequency f4 is superimposed on a signal radio wave having a certain intensity and the frequency f1, The output voltage Vout output from is superposed on a signal voltage having an amplitude of v1 ′ and a frequency of f1, and a noise voltage having an amplitude of v4 ′ and a frequency of f4. That is, since the frequency selectivity is deteriorated, the signal voltage is reduced while the noise voltage is increased in the output voltage Vout of the tuning circuit.

  As described above, particularly in a tuning circuit with poor frequency selectivity, when a noise source having a frequency component close to the frequency of a signal to be received exists, the ratio of the noise voltage to the output voltage Vout increases. In general, since frequency selectivity is restricted by the size of the antenna to be used and the arrangement of peripheral components, it is often difficult to obtain sufficient frequency selectivity. As a result, a noise radio wave having a frequency close to the frequency of the signal radio wave causes a decrease in reception sensitivity.

An example of such a noise radio wave having a specific frequency causing a decrease in reception sensitivity is a radio wave correction watch. In general, not only the radio-controlled clock, but the original clock (basic clock) of the clock is 32768 Hz. This 32768 Hz is the so-called 3
This frequency is abbreviated as 2 kHz. In the following description, the original frequency of the timepiece is simply referred to as 32 kHz.
On the other hand, the frequency of so-called standard radio waves received by the radio-controlled timepiece varies depending on the transmitting station, but is between 40 kHz and 80 kHz and is a frequency relatively close to 32 kHz.

  Since the 32 kHz original oscillation radiates a 32 kHz noise radio wave, the tuning circuit receives a 32 kHz noise radio wave in addition to the signal radio wave, and as a result, the output voltage Vout of the tuning circuit is converted into the signal voltage as the original clock signal. This is a voltage in which a noise voltage of 32 kHz, which is a vibration, is superimposed, causing a decrease in reception sensitivity.

  The present invention solves the above-described problems, and the object of the present invention is to prevent a decrease in reception sensitivity of a predetermined radio wave even in an environment where a noise radio wave having a specific frequency component is radiated. A tuning circuit is provided. Another object is to provide an electronic device using such a tuning circuit.

  In order to solve the above problems, the tuning circuit of the present invention employs the following configuration.

A tuning circuit having an antenna for receiving a radio wave of a predetermined frequency, and a tuning unit that is connected in parallel with the antenna and includes a capacitive means for tuning to a predetermined frequency,
A filter unit that resonates at another frequency different from the predetermined frequency is provided in parallel with the tuning unit, and the filter unit includes an induction circuit and a capacitor circuit connected in series.

  The inductive circuit is characterized in that the inductive element alone is configured or the inductive element and the capacitive element are connected in parallel.

  The capacitor circuit is characterized by being configured with only a capacitor element or configured by connecting a capacitor element and an inductive element in parallel.

  The capacitive means of the tuning unit includes a plurality of capacitive elements connected in parallel and includes a selection means for selecting these capacitive elements, and one or more capacitive elements are selected by the operation of the selection means, whereby the capacitive means It is characterized in that the capacitance value of the can be changed.

  In order to solve the above problems, an electronic device using the tuning circuit of the present invention employs the following configuration.

  Motor means having a drive coil for rotationally driving the structure using the tuning circuit described above is provided, switching means is provided between the drive coil and the tuning circuit, and the switching means is such that the motor means is operating. It is characterized by switching control so that the drive coil is used as an induction circuit when there is not.

The tuning circuit of the present invention includes a tuning unit connected in parallel to the antenna and a filter unit connected in parallel to the tuning unit. The filter unit connects the induction circuit and the capacitive circuit in series.
With such a configuration, the ratio of the noise voltage in the output voltage Vout can be reduced, and reception sensitivity can be improved.

Further, when an electronic device is configured using such a tuning circuit, for example, if it is a radio wave correction watch, when the motor means for driving the hands is not operating, the drive coil constituting the motor means Can be used as a filter circuit.
By adopting such a configuration, even if a noise radio wave having a specific frequency component is radiated in or near the electronic device, it does not cause a decrease in the reception sensitivity of the predetermined radio wave. An electronic device whose sensitivity does not decrease can be obtained.

  Hereinafter, embodiments of a tuning circuit of the present invention will be described with reference to the drawings. In the following description, the same constituent elements are denoted by the same reference numerals, and the description thereof is omitted or simplified.

[Description of Tuning Circuit Configuration and Characteristics: FIGS. 1 and 2]
In the embodiment of the present invention, the case where the tuning circuit of the present invention is applied as a tuning circuit of a radio-controlled timepiece will be described with reference to FIGS.
FIG. 1 shows a circuit diagram of a tuning circuit of the present invention. In FIG. 1, 1 is an antenna, 2 is a tuning unit, and 3 is a filter unit. Reference numeral 4 denotes grounding (GND level, for example, 0 V). Vout is the output voltage of the tuning circuit of the present invention. The tuning circuit of the present invention includes a tuning unit 2 and a filter unit 3 and is connected to the antenna 1 in parallel.

  The antenna 1 is for receiving a predetermined radio wave (for example, a standard radio wave) in combination with a receiving circuit (not shown). Although not particularly limited, an electric wire is wound around an antenna core such as ferrite, and a coil is attached. A bar antenna to be formed can be used. When standard radio waves are linked to the antenna core, an induced voltage is generated in the coil. A standard radio wave is received by this induced voltage.

  FIG. 2 is a characteristic diagram schematically showing the characteristics of the tuning circuit of the present invention, and shows the frequency characteristics of the output voltage Vout of the tuning circuit. In FIG. 2, the horizontal axis indicates the frequency, and the vertical axis indicates the amplitude of the output voltage Vout at each frequency when a radio wave having a certain intensity is received.

  The output voltage Vout becomes minimum at the frequency f2, and increases as the distance from the frequency f2 increases. It becomes maximum at the frequency f1, and becomes smaller as the frequency f1 is increased. Due to this characteristic, the ratio of the noise voltage in the output voltage Vout can be reduced by using the tuning circuit of the present invention.

  That is, when receiving a radio wave in which a noise radio wave having the same intensity and the frequency f2 is superimposed on a signal radio wave having a certain intensity and the frequency f1, the output voltage Vout has an amplitude v2 and a signal voltage having the amplitude f1 and the frequency f1. Thus, a voltage with a noise voltage of frequency f2 superimposed thereon is obtained. However, as can be seen from FIG. 2, the amplitude v2 is much smaller than the amplitude v1, and as a result, the output voltage Vout is almost equal to the signal voltage.

[Description of Filter Unit: FIGS. 3 and 4]
The configuration of the filter unit 3 constituting the tuning circuit of the present invention will be described with reference to FIGS. In FIG. 3, 31 is a first coil and 32 is a first capacitor.
FIG. 3 is a circuit diagram of the filter unit 3, in which a first coil 31 that functions as an induction circuit and a first capacitor 32 that functions as a capacitance circuit are connected in series.

FIG. 4 is a characteristic diagram schematically showing the characteristics of the filter unit 3 shown in FIG. 3 and shows frequency-impedance characteristics. In FIG. 4, the horizontal axis represents frequency and the vertical axis represents impedance.
As shown in FIG. 4, the filter unit 3 has a minimum impedance at the resonance frequency f2, and the impedance increases as the distance from the frequency f2 increases.
That is, by connecting the filter unit 3 in parallel with the tuning unit 2, the filter unit 3 short-circuits both ends of the tuning unit 2 with a low impedance at the frequency f2 of the filter unit 3 and suppresses the output voltage Vout. Work.
By connecting the filter unit 3 in parallel with the tuning unit 2 shown in FIG. 1, the characteristics shown in FIG. 2 can be obtained.

Further, since the frequency f2 shown in FIG. 2 is determined only by the constant of the filter unit 3, the frequency of the signal radio wave is set by setting the constant of the filter unit 3 so that the frequency of the noise radio wave in question and the frequency f2 coincide. The noise voltage can be kept small regardless of f1.

  As already described, in the radio-controlled timepiece, the noise radio wave of 32 kHz, which is the original frequency, has caused a decrease in reception sensitivity. However, in the embodiment of the present invention, the signal voltage is large in the output voltage Vout of the tuning circuit by having the filter unit 3 in parallel with the tuning circuit 2 and setting the resonance frequency f2 of the filter unit 3 to 32 kHz. In addition, the noise voltage can be kept low. As a result, the ratio of noise to the signal is reduced in the output voltage Vout of the tuning circuit, and reception sensitivity can be improved.

[Description of operation of tuning unit: FIG. 5]
Next, the operation of the tuning unit 2 constituting the tuning circuit of the present invention will be described with reference to FIGS. In FIG. 5, reference numerals 21a to 21d denote capacitors that are capacitive elements, and reference numerals 22a to 22d denote switch means that operate as selection means. Although the switch means is not particularly limited, a transistor switch using a transistor element can be used.

The frequency f1 shown in FIG. 2 is the resonance frequency of the antenna 1, the tuning unit 2, and the filter unit 3, and is determined by the constants of the antenna 1, tuning unit 2, and filter unit 3. If the constant of the tuning unit 2 can be changed, the received frequency can be handled. An example of the configuration is shown in FIG.
As shown in FIG. 5, the tuning unit 2 opens and closes the switch units 22 a to 22 d according to the received frequency, and selectively controls the capacitors 21 a to 21 d. Thereby, the frequency f1 can be changed.

  For example, when receiving a standard radio wave of 40 kHz, the switch means 22a is closed. When receiving a standard radio wave of 60 kHz, the switch means 22a and 22b are closed. Of course, the capacitors 21a to 21d may have different capacitance values or the same capacitance value. An appropriate selection can be made according to the frequency to be received. In this way, the switching means 22a to 22d shown in FIG. 4 is switched and the capacitors 21a to 21d are selected and the capacitance values are adjusted so that the frequency f1 matches the frequency of the radio wave to be received. Thus, a large signal voltage can be obtained as the output voltage Vout.

[Description of different examples of filter units: FIGS. 6 and 7]
The tuning unit 2 and the filter unit 3 constituting the tuning circuit of the present invention have been described above. However, the configuration of the filter unit 3 is not limited to the configuration described above, and can be changed as appropriate.
In the example described above, the filter unit 3 has been described as being configured by one coil and one capacitor. However, the configuration is not limited thereto. Next, different examples of the filter unit 3 of the tuning circuit of the present invention will be described with reference to FIGS. In FIG. 6, reference numeral 33 denotes a second coil. The same numbers are assigned to the same configurations already described.
FIG. 7 is a characteristic diagram schematically showing the characteristics of the filter unit 3 shown in FIG. 6 and shows frequency-impedance characteristics. In FIG. 6, the horizontal axis represents frequency and the vertical axis represents impedance.

The filter unit 3 shown in FIG. 6 is obtained by adding the second coil 33 to the configuration shown in FIG. 3, and the second coil 33 is connected in parallel to the first capacitor 32.
As shown in FIG. 7, the filter unit 3 has the same impedance at the resonance frequency f2 and the impedance increases as the distance from the resonance frequency f2 increases, but at a frequency lower than the resonance frequency f2, The impedance is lower than in the example shown in FIG. As a result, noise in the low frequency range can be further reduced.

[Description of different examples of filter units: FIGS. 8 and 9]
In the example already described, the filter unit 3 has shown an example in which a coil is added, but the configuration is not limited thereto. Next, different examples of the filter unit 3 constituting the tuning circuit of the present invention will be described with reference to FIGS. In FIG. 8, reference numeral 34 denotes a second capacitor. The same numbers are assigned to the same configurations already described.
FIG. 9 is a characteristic diagram schematically showing the characteristics of the filter unit 3 shown in FIG. 8, and shows frequency-impedance characteristics. In FIG. 9, the horizontal axis represents frequency and the vertical axis represents impedance.

A filter unit 3 shown in FIG. 8 is obtained by adding a second capacitor 34 to the configuration shown in FIG. 3, and a second capacitor 34 is connected in parallel to the first coil 31.
As shown in FIG. 9, the filter unit 3 has the same impedance at the resonance frequency f2, and the impedance increases as the distance from the resonance frequency f2 increases, but at a frequency higher than the resonance frequency f2, The impedance is lower than that in the example shown in FIG. Thereby, noise in a high frequency region can be further reduced.

[Description of different examples of filter units: FIGS. 10 and 11]
In the example described above, the filter unit 3 has an example in which a capacitor and a coil are added, but the configuration is not limited thereto. Next, different examples of the filter unit 3 constituting the tuning circuit of the present invention will be described with reference to FIGS. In FIG. 10, reference numeral 35 denotes a resistor. The same numbers are assigned to the same configurations already described.
FIG. 11 is a characteristic diagram schematically showing the characteristics of the filter unit 3 shown in FIG. 10 and shows frequency-impedance characteristics. In FIG. 10, the horizontal axis represents frequency and the vertical axis represents impedance.

The filter unit 3 shown in FIG. 10 is obtained by adding a resistor 35 to the configuration shown in FIG. 2, and the resistor 35 is connected in series to the first coil 31 and the first capacitor 32.
As shown in FIG. 11, the filter unit 3 has the same minimum impedance at the resonance frequency f2, and the impedance increases as the distance from the resonance frequency f2 increases, but the frequency bandwidth cut by the filter is adjusted. can do. Of course, the resistor 35 may be a variable resistor. Thereby, the frequency bandwidth to be cut can be freely adjusted, or the frequency can be finely adjusted after the circuit is completed.

The structure of the filter part 3 demonstrated above can be used in combination with each other. For example, the resistor 35 may be connected to the configuration shown in FIGS. 6 and 8 as shown in FIG. Further, the first capacitor 32 shown in FIGS. 3, 6, 8, and 10 and the second capacitor 34 shown in FIG. 8 are connected in parallel with each other as shown in FIG. This may be selected.
In short, it can be appropriately changed according to the specifications and electrical characteristics of the circuit using the tuning circuit of the present invention.

[Description of mounting example on radio-controlled watch: Fig. 12]
Next, a case where the tuning circuit of the present invention is mounted on an electronic device will be described. The case where the electronic device is a radio wave correction watch provided with a motor driving coil will be described with reference to the drawings.
FIG. 12 is a diagram schematically showing a radio-controlled timepiece equipped with the tuning circuit of the present invention. In FIG. 12, 41 is a motor driving coil, 42 is a motor, 43 is an exterior case of a radio-controlled timepiece, and 44 is switch means that functions as switching means. The same numbers are assigned to the same configurations already described.

  The motor driving coil 41 is a component constituting the motor 42. The radio-controlled timepiece has a movement (functional parts group) (not shown) mounted on the outer case 43, and the tuning circuit of the present invention is also incorporated in this movement. The movement is also provided with a motor 42 for driving the pointer as a time notification means for notifying the time, and the motor 42 is driven by a circuit (not shown).

  The example shown in FIG. 12 shows an example in which a motor driving coil is used for an induction circuit constituting a filter circuit. That is, the motor drive coil 41 also serves as a coil (the first coil 31 in the example of FIG. 3) that is an induction circuit of the filter circuit 3 constituting the tuning circuit of the present invention.

When the standard radio wave is not received, that is, during normal operation, the switch 44 is opened, and the motor driving coil 41 is used only for hand movement.
When the standard radio wave is received, that is, when the radio wave is received, the switch means 44 is closed. The motor driving coil 41 and the first capacitor 32 are connected via the switch means 44.
Thereby, the filter part 3 as shown in FIG. 3 with which the coil and the capacitor | condenser were connected in series can be comprised.

  As a result, the tuning circuit of the present invention has frequency characteristics as shown in FIG. 2, and the output voltage Vout can obtain a large signal voltage and at the same time suppress the noise voltage to a small value.

  By inserting the filter unit in parallel with the antenna, the sensitivity to noise having a specific frequency component can be lowered, and the ratio of the noise voltage to the signal voltage of the output voltage Vout of the tuning circuit can be reduced. Therefore, it is suitable for an electronic device having a specific noise source, particularly a radio-controlled timepiece.

It is a circuit diagram of a tuning circuit of the present invention. It is a frequency characteristic of the tuning circuit of this invention. It is a circuit diagram explaining the filter part which comprises the tuning circuit of this invention. It is a frequency characteristic of the filter part which comprises the tuning circuit of this invention. It is a circuit diagram explaining the tuning part which comprises the tuning circuit of this invention. It is a circuit diagram explaining the other structural example of the filter part which comprises the tuning circuit of this invention. It is a frequency characteristic of the other structural example of the filter part which comprises the tuning circuit of this invention. It is a circuit diagram explaining another structural example of the filter part which comprises the tuning circuit of this invention. It is a frequency characteristic of another structural example of the filter part which comprises the tuning circuit of this invention. It is a circuit diagram explaining another example of composition of a filter part which constitutes a tuning circuit of the present invention. It is a frequency characteristic of another structural example of the filter part which comprises the tuning circuit of this invention. It is a figure explaining the electronic device using the tuning circuit of this invention. It is a circuit diagram explaining the prior art shown in patent document 1. FIG. It is a figure which shows the frequency characteristic explaining the prior art shown in patent document 1. FIG. It is a figure which shows the frequency characteristic explaining the prior art shown in patent document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Tuning part 3 Filter part 4 Ground 31 1st coil 32 1st capacitor 21 Tuning capacitor 21a-21d Capacitor 22a-22d Capacitance element 22a-22d Switch means which operate | move as selection means 33 2nd coil 34 2nd Capacitor 41 Motor driving coil 42 Motor 43 Exterior case 44 Switch means

Claims (5)

A tuning circuit having an antenna for receiving a radio wave of a predetermined frequency, and a tuning unit that is connected in parallel with the antenna and includes a capacitive means for tuning to the predetermined frequency,
A filter unit that resonates at another frequency different from the predetermined frequency is provided in parallel with the tuning unit,
In the tuning circuit, the inductive circuit and the capacitor circuit are connected in series in the filter unit.   2. The tuning circuit according to claim 1, wherein the inductive circuit is configured by an inductive element alone or an inductive element and a capacitive element connected in parallel.   2. The tuning circuit according to claim 1, wherein the capacitor circuit is configured by a capacitor element alone or a capacitor element and an inductive element connected in parallel. The capacitive unit of the tuning unit includes a plurality of capacitive elements connected in parallel and a selection unit that selects these capacitive elements,
4. The tuning according to claim 1, wherein the capacitance value of the capacitive means can be changed by selecting one or a plurality of capacitive elements by the operation of the selecting means. 5. circuit. Using the tuning circuit according to any one of claims 1 to 4,
Motor means comprising a drive coil for rotationally driving the structure;
A switching means is provided between the drive coil and the tuning circuit,
The electronic device according to claim 1, wherein the switching means performs switching control so that the drive coil is used as the induction circuit when the motor means is not operating.

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