Method and Configuration of Sound Generation of Electronic Device

Abstract

The electronic sound-generating arrangement includes a magnetic vibrator (101) including a first part (203) and a second part (204) provided with permanent magnets and at least one induction coil (205). The arrangement further includes a piezoelectric vibrator (102) including a piezoelectric material and adapted to generate audible vibrations resulting from deformation of the material by applying a second electric signal to the material. The magnetic vibrator (101) and the piezoelectric vibrator (102) have a common audio amplifier (103). The first and second electric signals are applied to the magnetic vibrator (101) and the piezoelectric vibrator (102) from a same audio output (104).

Description

Technical Field

[0001] The present invention relates to an electroacoustic transducer that converts an electrical signal into an audible sound. Specifically, the present invention proposes how such a transducer can be realized in a small portable electronic device so that its sound quality is good and the requirements set for the audio amplifier of the device are reasonable.

Background Art

[0002] In portable electronic devices such as smartphones, tablet computers, and laptops, small electromagnetic speakers are generally used for sound emission. In addition to actual speakers, magnetic vibrators are known, which have two parts, both of which include one or more permanent magnets and induction coils. One of the two parts of the magnetic vibrator is fixed to some frame parts inside the device, and the other is fixed to a cover part, such as a display, that functions as an elastic surface for transmitting the vibration generated by the magnetic vibrator to the surrounding air. The vibration is generated by supplying an electrical signal to the induction coil, and its changing magnetic field, together with the magnetic field of the permanent magnet, generates a force that displaces the parts of the magnetic vibrator relative to each other. The magnetic vibrator in the meaning intended in this specification is known from the applicant's prior patent applications such as Finnish Patent Application Publication No. 20195599, European Patent Application Publication No. 3603110, European Patent Application Publication No. 3222055, Finnish Patent Application Publication No. 20215101, Finnish Patent Application Publication No. 20205298, and Finnish Patent Application Publication No. 20175942.

[0003] In addition to those listed above, one known method of sound emission in electronic devices is a piezoelectric vibrator. In a piezoelectric vibrator, a metal piece coated with a piezoelectric material is fixed to a cover part of the device, for example, inside a display. An electrical signal supplied to the piezoelectric material causes a rapid and reversible deformation in the material, whereby the cover part vibrates as a whole and functions as an acoustic element. The metal piece functions as a mechanical support for the piezoelectric material, which is very fragile.

[0004] In known sound emission solution means, it has been found to be difficult to achieve an appropriate combination of favorable characteristics such as small size, excellent efficiency at all audible frequencies, and low-cost control electronics. For example, an audio amplifier that drives a piezoelectric vibrator often has difficult requirements for control electronics because it has to generate a relatively high voltage. The prior art document, Finnish Patent Application Publication No. 20195599A1, discloses a two-component magnetic vibrator having a permanent magnet and a coil for the sound emission of an electronic device. Another prior art document, US Patent Application Publication No. 2020 / 233629A1, discloses a display device in which a sound generating device includes first, second, third, and fourth vibrators. Another prior art document, US Patent Application Publication No. 2019 / 0334076A1, discloses a hybrid actuator capable of reproducing both vibration signals and audio signals. Another prior art document, International Publication No. 97 / 09842A2 pamphlet, discloses an acoustic device in which a laterally extending member has a distribution of resonance modes of natural flexural wave vibrations of the member over a parameter-dependent region.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

[0006] An object of the present invention is to be able to produce sound in an electronic device so that the efficiency at all audible frequencies is improved. Another object of the present invention is that components of the electronic device mainly required for sound production are adapted to a small space and the manufacturing cost is reduced. [Means for Solving the Problems]

[0007] The object of the present invention is achieved by driving a piezoelectric vibrator and a magnetic vibrator using a common audio amplifier.

[0008] In one aspect of the present invention, a sound-producing configuration of an electronic device is provided. The configuration includes a magnetic vibrator including a first component and a second component provided with a permanent magnet, and at least one induction coil that generates vibrations of an audible frequency between the first component and the second component by supplying a first electrical signal. The configuration includes a piezoelectric vibrator including a piezoelectric material and generating vibrations of an audible frequency resulting from deformation of the material by supplying a second electrical signal to the material, and an audio amplifier that is common to the magnetic vibrator and the piezoelectric vibrator and has an audio output for supplying the first electrical signal and the second electrical signal to the magnetic vibrator and the piezoelectric vibrator.

[0009] In one embodiment, the configuration includes a first component and a second component of the electronic device, and the first component is an outer cover of the electronic device or a part of the outer cover. Therefore, the first component of the magnetic vibrator may be fixed to the first component of the electronic device, and the second component of the magnetic vibrator may be fixed to the second component of the electronic device. This provides the advantage that the components of the electronic device can be utilized for participating in sound emission even when they have other purposes simultaneously.

[0010] In one embodiment, the piezoelectric vibrator is fixed to the first component of the electronic device or another part of the outer cover of the electronic device. This provides the advantage that a part of the outer cover of the electronic device can participate in the generation of sound components resulting from the deformation of the piezoelectric vibrator.

[0011] In one embodiment, the piezoelectric vibrator is fixed to the first component of the electronic device in the same manner as the first component of the magnetic vibrator. Thereby, the first electrical signal and the second electrical signal may be supplied to the magnetic vibrator and the piezoelectric vibrator from the audio output with opposite polarities, and the polarity is determined according to the direction in which a specific polarity of the electrical signal displaces the first component of the electronic device under the action of the magnetic vibrator on one hand and under the action of the piezoelectric vibrator on the other hand. This provides the advantage that the phase difference existing in the vibrations generated by different vibrators and resulting from the capacitive and inductive properties of the vibrators does not significantly affect sound emission.

[0012] In one embodiment, the first electrical signal and the second electrical signal are supplied from the audio output to the magnetic vibrator and the piezoelectric vibrator without performing frequency division filtering therebetween. This provides the advantage that the connection becomes relatively simple and the manufacturing cost is reduced.

[0013] In one embodiment, the configuration includes a filter bank configured to supply a lower frequency signal component from the audio output to the magnetic vibrator than a frequency signal component supplied from the audio output to the piezoelectric vibrator. This provides the advantage that the frequency characteristics of different types of vibrators can be utilized to the maximum extent possible.

[0014] In one embodiment, the configuration includes a limiting impedance connected between the audio output and the piezoelectric vibrator. This provides the advantage that the output of the audio amplifier is more appropriately protected against low impedance values present at some frequencies of the piezoelectric vibrator.

[0015] In one embodiment, the limiting impedance is a resistor or a coil. This provides the advantage that the protection of the audio output can be achieved with a low-cost technology having well-known characteristics.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0017] Figure 1 schematically shows the sound - generating configuration of an electronic device. This configuration first includes a magneto - oscillator 101. This term is intended to mean an electro - acoustic transducer that includes a first part and a second part provided with a permanent magnet and at least one induction coil, as described above. The purpose of the magneto - oscillator 101 is to generate vibrations in the audible frequency range when an electrical signal is supplied to its induction coil. In this specification, the electrical signal supplied to the induction coil of the magneto - oscillator 101 is called the first electrical signal. Since the magneto - oscillator mainly appears as an inductance in the rest of the electrical circuit, the corresponding drawing symbol is used in Figure 1. Regarding its more specific structure, the magneto - oscillator 101 may represent any type of magneto - oscillator described, for example, in Finnish Patent Application Publication No. 20195599, European Patent Application Publication No. 3603110, European Patent Application Publication No. 3222055, Finnish Patent Application Publication No. 20215101, Finnish Patent Application Publication No. 20205298, and Finnish Patent Application Publication No. 20175942 of the same applicant.

[0018] This configuration further includes a piezoelectric oscillator 102. The piezoelectric oscillator, in a known manner of its own, includes a piezoelectric material and generates vibrations in the audible frequency range resulting from the deformation of the material by supplying an electrical signal to the material. In this specification, the electrical signal supplied to the piezoelectric oscillator is called the second electrical signal. Since the piezoelectric oscillator mainly appears as a capacitance in the rest of the electrical circuit, a drawing symbol derived from the capacitor symbol is used in Figure 1.

[0019] In addition to the oscillators 101 and 102, this configuration includes an audio amplifier 103. The audio amplifier 103 is common to the magneto - oscillator 101 and the piezoelectric oscillator 102. In other words, the above - mentioned first electrical signal and second electrical signal are supplied to the magneto - oscillator 101 and the piezoelectric oscillator 102 from the same audio output 104 of the audio amplifier 103.

[0020] Using a common audio amplifier for both the magnetic oscillator and the piezoelectric oscillator is based on the recognition that the frequency characteristics of these two types of oscillators complement each other. The response of the magnetic oscillator to an audio signal is highest at low frequencies due to the inductive nature of the magnetic oscillator as an electrical component. The input impedance of the magnetic oscillator increases as a function of frequency and becomes very high at high frequencies of several kilohertz, making it difficult to pass sufficient current to output a good high-frequency audio signal. The frequency response of the piezoelectric oscillator is the opposite, which is due to its capacitive nature as an electrical component. The typical conditions of the prior art for driving the piezoelectric oscillator at a relatively high voltage (30 V or more, and further 100 V or more) are because, at a lower voltage (10 V or less), especially low frequencies cause problems. When the audio amplifier 103 is common to the magnetic oscillator 101 and the piezoelectric oscillator 102, the low frequencies of the audio signal output by the audio amplifier are reproduced more naturally through the magnetic oscillator 101, and the high frequencies are reproduced more naturally through the piezoelectric oscillator 102. With the configuration described in this specification, it becomes possible to make the voltage amplitude of the signal at the audio output 104 of the audio amplifier 103 less than 10 V.

[0021] FIG. 2 shows an example of how the magnetic oscillator and the piezoelectric oscillator can be arranged within an electronic device. FIG. 2 shows a schematic cross-sectional view of a part of an electronic device including a first component 201 and a second component 202. The first component 201 is an outer cover of the electronic device or a part of the outer cover, such as a display, a back panel, a protective screen, etc. When the electronic device is very thin, the second component 202 may be a part on the opposite side of the outer cover. However, the second component 202 may also be an inner component of the electronic device, such as a circuit board or a support frame.

[0022] The magneto-oscillator 101 is shown on the right side of FIG. 2. Its first component 203 is fixed to the first component 201 of the electronic device, and its second component 204 is fixed to the second component 202 of the electronic device. Since the first component 203 and the second component 204 of the magneto-oscillator are clearly shown separated from each other here, the induction coil 205 is shown between them. However, this illustrated mode is only selected for the sake of clarity of the figure. In an actual magneto-oscillator, the first component and the second component may be partially inside each other, and the induction coil may be inside either one of them so as not to be visible from the outside.

[0023] In many cases, a typical example of a magneto-oscillator is that each of its first and second components includes a respective cover component made of a magnetic material, and other components of the magneto-oscillator such as a permanent magnet and an induction coil are arranged inside the cover component. In this case, the fixing to the first component 201 and the second component 202 of the electronic device as shown in FIG. 2 can be realized such that the cover component of the first component 203 of the magneto-oscillator is fixed to the first component 201 of the electronic device from its outer surface, and the cover component of the second component 204 of the magneto-oscillator is fixed to the second component 202 of the electronic device from its outer surface. Such fixing may be direct fixing (for example, fixing by an adhesive or solder), or may be fixing with a special fixing component between them.

[0024] The piezoelectric vibrator 102 is shown on the left side of FIG. 2. In the embodiment of FIG. 2, the piezoelectric vibrator 102 is fixed to the first component 201 of the electronic device in the same manner as the first component 203 of the magnetic vibrator 101. The piezoelectric vibrator 102 may be fixed to other parts of the outer cover of the electronic device. Therefore, although the piezoelectric vibrator 102 does not necessarily have to be fixed particularly to the outer cover of the electronic device, in many cases, as intended in this specification, since a part of the outer cover can be relatively easily arranged to function as a sufficiently effective elastic surface, this type of fixation always brings advantages. As intended in this specification, a typical example of the piezoelectric vibrator is that the piezoelectric vibrator is firmly fixed to only one component of the electronic device, rather than being provided between two components of the electronic device. Therefore, the deformation generated from the electrical signal in the piezoelectric material of the piezoelectric vibrator is transmitted to the deformation of that component of the electronic device to generate the desired sound.

[0025] The audio amplifier or other electronic device of the electronic device is not shown in FIG. 2. However, FIG. 2 schematically shows conductors 206 and 207, and appropriate electrical signals may be supplied from the audio output of the audio amplifier to the magnetic vibrator 101 and the piezoelectric vibrator 102 along these conductors 206 and 207. When the second component 202 of the electronic device is a circuit board, the audio amplifier may be naturally arranged at a certain location on the circuit board.

[0026] The piezoelectric vibrator 102 and the magnetic vibrator 101 do not necessarily have to be arranged close to each other within the electronic device. Their positions may be selected by determining their respective optimal positions, for example, in terms of space requirements, assembly, and acoustic operation.

[0027] As shown in FIG. 2, when the first components 203 of the piezoelectric vibrator 102 and the magnetic vibrator 101 are fixed to the same first component 201 of the electronic device, it is advantageous to pay attention to the polarity of the electrical signal. Neither the capacitor-type piezoelectric vibrator 102 nor the coil-type magnetic vibrator 101 is very sensitive to the polarity of the signal, like a diode for example. However, polarity is important when considering in which direction the electrical signal causes their displacement. In the magnetic vibrator 101, a current flowing in one direction through the induction coil 205 generates a force that moves the first component 203 and the second component 204 away from each other. Similarly, a current flowing in the opposite direction through the induction coil 205 generates a force that pulls the first component 203 and the second component 204 towards each other. Similarly, in the piezoelectric vibrator 102, one polarity of the voltage causes a deformation in one direction, and the other polarity causes a deformation in the opposite direction. These movements cause corresponding displacements of the first component 201 of the electronic device, ultimately generating the desired sound.

[0028] The capacitive load and the inductive load generate opposite phase shifts in the oscillating electrical signal. This phase shift may increase due to impedance matching between the signal source and the load. In order for the displacements of the first component 201 of the electronic device caused by the magnetic vibrator 101 and the piezoelectric vibrator 102 to complement rather than cancel each other out, their fixation and wiring should be advantageously realized such that the above effect of the polarity of the electrical signal resulting from the fixation to the first component 201 of the electronic device is reversed between them. In other words, the polarity should be advantageously selected in such a way that when the electrical signal is supplied to the magnetic vibrator 101, it displaces the first component 201 of the electronic device in the outer direction, and when the electrical signal is supplied to the piezoelectric vibrator 102, it displaces the first component 201 of the electronic device in the inner direction.

[0029] The above principle can be defined as the first electrical signal and the second electrical signal being supplied from the audio output of the audio amplifier to the magneto-vibrator and the piezo-vibrator with opposite polarities. Therefore, in this specification, the polarity is determined according to the direction in which a specific polarity of the electrical signal displaces the first component of the electronic device by the action of the magneto-vibrator on the one hand and by the action of the piezo-vibrator on the other hand.

[0030] On the one hand, the capacitive nature of the piezo-vibrator, on the other hand, the inductive nature of the magneto-vibrator and the phase difference caused by them have greatly different effects on the displacement of the components of the electronic device. However, this difference depends on whether the vibrators are fixed to the same component of the electronic device, and if they are fixed to the same component, how far apart the vibrators are from each other, and what other characteristics of the structure are. Therefore, in some embodiments, it may be most advantageous to supply the first electrical signal and the second electrical signal from the audio output of the audio amplifier to the magneto-vibrator and the piezo-vibrator with the same specific polarity.

[0031] Since the frequency responses of the magneto-vibrator and the piezo-vibrator that operate in reverse may complement each other sufficiently, the first electrical signal and the second electrical signal may be supplied from the audio output 104 of the audio amplifier 103 to the magneto-vibrator 101 and the piezo-vibrator 102 without performing frequency division filtering therebetween. In this case, due to the natural characteristics of the vibrators, the propagation of signal components of different frequencies is controlled to a sufficient extent. This principle is shown in FIG. 1 above.

[0032] FIG. 3 shows another possible embodiment. This embodiment includes a filter bank 301 configured to supply a lower frequency signal component from the audio output 104 of the audio amplifier 103 to the magneto-vibrator 101 compared to the frequency signal component supplied from the audio output 104 of the audio amplifier 103 to the piezo-vibrator 102. The filter bank 301 may represent any technique that may itself be used to identify audible frequency signal components based on frequency.

[0033] Regardless of whether a filter bank is used, it is possible to refer to a cut-off frequency or a cut-off frequency range. The magneto-oscillator plays a major role in generating sounds at frequencies lower than the cut-off frequency or the cut-off frequency range, and the piezoelectric oscillator plays a major role in generating sounds at frequencies higher than the cut-off frequency or the cut-off frequency range. In relation to the research work of the present invention, when comparing the two configurations, both include a similar audio amplifier and a magneto-oscillator, but only one of them further includes a piezoelectric oscillator. The subjective impression of audible sound is very similar in both configurations at frequencies below 5 kHz. This is as expected. Because at frequencies lower than this frequency, the frequency response of the piezoelectric oscillator is particularly disadvantageous for a low-amplitude audio amplifier, so the piezoelectric oscillator does not participate much in sound production. At frequencies greater than 5 kHz, in the configuration including the piezoelectric oscillator, the subjective sound quality begins to improve. In the case of a test signal including frequencies greater than 10 kHz, this difference was particularly obvious. This is because when reproduced by a configuration based only on the magneto-oscillator, the high-frequency part of these test signals seems to be completely cut off (blocked) or at least attenuated to an uncomfortable degree.

[0034] How low the impedance of the piezoelectric oscillator 102 becomes at the highest frequency depends on the configuration of the piezoelectric oscillator 102. On the other hand, how much current the audio amplifier 103 can generate at the audio output 104 depends on the configuration of the audio amplifier 103. It is possible to configure the piezoelectric oscillator 102 and / or the audio amplifier 103 so that some of their specific factors function as a limiter to prevent the audio amplifier 103 from being damaged by the influence of an excessively high output current that can be dangerous especially at the highest frequency. In order to improve the reliability of this point of the configuration, it is possible to add a limiting impedance connected between the audio output 104 and the piezoelectric oscillator 102 to the configuration. This is shown in FIG. 4 where the limiting impedance 401 is shown as Z. The limiting impedance 401 may be, for example, a resistor or a coil.

[0035] The above configuration can also be used to generate a tactile effect. This means that vibrations intended to be perceived by the user's sense of touch are generated using the same vibrator that is also used to generate the desired sound. However, in typical examples of the tactile effects contemplated herein, their frequencies are only a few hundred hertz at most, even when high. Therefore, since these frequencies are too low for a piezoelectric vibrator, in practice only the magnetic vibrator participates in the generation of the tactile effect.

Claims

1. An electronic device including a first component (201) and a second component (202), and a sound generating configuration of the electronic device, wherein the first component (201) is an outer cover of the electronic device or a part of the outer cover, and the configuration includes a first component (203) provided with a permanent magnet and fixed to the first component (201) of the electronic device, and a second component (204) provided with a permanent magnet and fixed to the second component (202) of the electronic device, and at least one induction coil (205) that generates vibrations in the audible frequency range between the first component (203) and the second component (204) when a first electrical signal is supplied, including a magnetic vibrator (101); a piezoelectric vibrator (102) including a piezoelectric material and generating vibrations in the audible frequency range resulting from the deformation of the material when a second electrical signal is supplied to the material; an audio amplifier (103) common to the magnetic vibrator (101) and the piezoelectric vibrator (102), having an audio output (104) for supplying the first electrical signal and the second electrical signal to the magnetic vibrator (101) and the piezoelectric vibrator (102); the piezoelectric vibrator (102) is fixed to the first component (201) of the electronic device in the same manner as the first component (203) of the magnetic vibrator; the first electrical signal and the second electrical signal are supplied from the audio output (104) to the magnetic vibrator (101) and the piezoelectric vibrator (102) with opposite polarities, and the polarities are determined according to the direction in which a specific polarity of the electrical signal displaces the first component (201) of the electronic device under the action of the magnetic vibrator (101) on the one hand and the piezoelectric vibrator (102) on the other hand. An electronic device characterized by the above.

2. The electronic device according to claim 1, wherein the first electrical signal and the second electrical signal are supplied from the audio output (104) to the magnetic vibrator (101) and the piezoelectric vibrator (102) without performing frequency division filtering therebetween.

3. The electronic device according to claim 1, including a filter bank (301) configured to supply a lower frequency signal component from the audio output (104) to the magnetic vibrator (101) than a frequency signal component supplied from the audio output (104) to the piezoelectric vibrator (102).

4. The electronic device according to any one of claims 1 to 3, including a limiting impedance (401) connected between the audio output (104) and the piezoelectric vibrator (102).

5. The electronic device according to claim 4, wherein the limiting impedance (401) is a resistor or a coil.

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