JP2009117981A - Control apparatus of electrostatic type transducer, control method of electrostatic type transducer, and ultrasonic speaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control apparatus of an electrostatic type transducer for obtaining the identical output characteristic at the next driving time even when the electrostatic type transducer is driven using the maximum value. <P>SOLUTION: The control apparatus of the electrostatic type transducer is constituted by including: a vibration film where an electrode film is formed on a dielectric material film; and a fixed electrode arranged in the side of the surface of the dielectric material film of the vibration film to generate an electrostatic force between the fixed electrode and the vibration film by impressing a voltage therebetween. The control apparatus is characterized by including: a means for impressing a DC bias voltage in which a signal wave is superimposed between the vibration film and the fixed electrode when the electrostatic type transducer is driven; and a means for impressing a DC bias voltage for erasing residual polarization between the vibration film and fixed electrode in order to cancel the residual polarization of the dielectric material film generated by impressing the DC bias voltage when driving the electrostatic type transducer is completed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an electrostatic transducer that vibrates a vibrating membrane with an electrostatic force, and in particular, it is stabilized each time by canceling residual polarization that occurs when a DC bias voltage is applied to the vibrating membrane of an electrostatic transducer. In particular, the present invention relates to a control device for an electrostatic transducer, a control method for an electrostatic transducer, and an ultrasonic speaker capable of obtaining highly efficient output characteristics.

  An electrostatic transducer is a device composed of a vibration film having an electrode film and a fixed electrode facing the vibration film. As an example of the application of the electrostatic transducer, there is a small-sized and wide-band electrostatic microphone for an input device, and an electrostatic speaker that can obtain a clear sound quality in a mid-high range for an output device.

  In recent years, electrostatic transducers have been tried to be used as ultrasonic speakers that can provide a very sharp directional sound as compared to spherical wave speakers. Here, an ultrasonic speaker is an audible sound with a differential frequency component (self-demodulated sound) having a very strong directivity due to the parametric array effect when a signal obtained by modulating an ultrasonic wave with an audio signal is emitted by an ultrasonic transducer. Are to be released. Since the self-demodulated sound emitted from the ultrasonic speaker is very directional, it is used for the purpose of transmitting audio information only to a specific location.

  The vibration film of the electrostatic transducer has a structure in which a metal thin film is formed on a polymer film (dielectric) by vapor deposition or the like. The vibrating membrane and the fixed electrode face each other, a high DC voltage is applied between the fixed electrodes, and the voltage is changed by a signal voltage to vibrate the vibrating membrane.

  For example, there is a conventional electrostatic transducer (see Patent Document 1). In this conventional electrostatic transducer, a polymer film such as PET (polyethylene terephthalate resin) or aramid is used as the dielectric of the vibration film of the electrostatic transducer. In order to obtain a self-demodulated sound having a large sound pressure with an ultrasonic speaker, it is necessary to output a strong ultrasonic wave of at least 120 dB or more. In order to output an ultrasonic wave of 120 dB or more in a conventional electrostatic transducer, it is necessary to apply a DC bias of about several hundred volts to the vibrating membrane and to apply an AC signal voltage to the fixed electrode.

Here, when the value of the signal voltage is constant, the sound pressure level of the ultrasonic wave increases as the value of the DC bias applied to the vibrating membrane increases, and saturates at a certain sound pressure level. For convenience, the value of the DC bias at this time is _{V 1.} The saturation sound pressure level described above depends on the magnitude of the signal voltage applied to the fixed electrode, but when the signal voltage is constant, the electrostatic transducer is the largest sound pressure level when driven at the saturation sound pressure level. Is obtained. Since an electrostatic force is difficult to obtain a larger force than a piezoelectric force or the like, it is important to obtain a larger force by applying a large DC bias.

  However, when a large DC bias is applied to the electrostatic transducer of the prior art, the polymer film of the vibrating membrane is polarized, and this polarization remains even when the DC bias applied voltage is set to 0 (hereinafter referred to as this). This causes a problem that the same output characteristics cannot be obtained when driven under the same conditions.

  Details will be described below. FIG. 18A shows a characteristic diagram of the voltage due to the remanent polarization of the polymer film-applied DC bias. FIG. 18B shows an example of the characteristics of the output sound pressure level of the electrostatic transducer and the applied DC bias when the signal voltage is constant.

  As shown in FIG. 18A, when the DC bias applied to the polymer film exceeds Va (determined by the type and film thickness of the polymer film), even if the DC bias is returned to 0, the residual polarization It can be seen that an electric potential is generated. The magnitude of the remanent polarization depends on the magnitude of the applied DC bias.

Here, it is considered that the DC bias is increased to V ₁ in order to drive the electrostatic transducer with the maximum output value. At this time, the sound pressure level increases as shown by curve 1 in FIG. However once lowered DC bias lower than V ₁ value, due to the influence of the residual polarization of the diaphragm, the sound pressure level will follow a trajectory of the curve 2 in FIG. 18 (B). Therefore, even when the same DC bias V ₁ is applied, only a sound pressure value A ₁ lower than the saturation sound pressure level can be obtained.

Further, consider a case where the value of the DC bias is increased from V ₁ to V ₁ ′ on the curve 2 and the sound pressure level is output to the saturation level. In this case, the sound pressure level reaches the saturation level. However, since a larger remanent polarization occurs, once the DC bias is lowered to a value lower than V ₁ ′, the sound pressure level follows the locus of curve 3 in FIG. Accordingly, even if the DC bias is driven as V ₁ or V ₁ ′, the sound pressure level can be obtained only at a value lower than the saturation level.

  As described above, when the electrostatic transducer is driven at the maximum or close to the output value, there is a problem that a larger DC bias is required to obtain an equivalent output characteristic at the next and subsequent driving.

Further, as a method of not directly applying a DC bias to the vibrating membrane of the electrostatic transducer, there is a method of using an electret film as the dielectric of the vibrating membrane. An electret film is a film in which an electrostatic charge is permanently charged on the surface of the polymer film by corona discharge or the like. Although it is conceivable that the above problems can be solved by using an electret film, it cannot be changed to the desired DC bias value in a timely manner, and when a large alternating voltage is applied to the fixed electrode, charge loss occurs and the performance deteriorates over time. Problems occur. In particular, when an electrostatic transducer is used as an output device, a large alternating-current signal voltage is applied during driving. Therefore, a DC bias is often directly applied to the diaphragm without using an electret film in terms of stability. .
JP 2007-88680 A

  As described above, when the electrostatic transducer is driven at the maximum or close to the output value, there is a problem that a larger DC bias is required in order to obtain an equivalent output characteristic at the next and subsequent driving.

  The present invention has been made to solve such a problem, and the object thereof is the same under the same driving conditions during the next and subsequent driving even when the electrostatic transducer is driven at the maximum or near input / output value. It is an object to provide a control device for an electrostatic transducer, a control method for an electrostatic transducer, and an ultrasonic speaker that can obtain the output characteristics of the same.

The present invention has been made to solve the above-described problems, and an electrostatic transducer control device according to the present invention includes a vibration film in which an electrode film is formed on a dielectric film, and the dielectric film of the vibration film. A fixed electrode disposed on the surface side of the substrate, and configured to apply a voltage between the fixed electrode and the vibrating membrane to generate an electrostatic force between the fixed electrode and the vibrating membrane. A control device for an electrostatic transducer, wherein when the electrostatic transducer is driven, means for applying a DC bias voltage on which a signal wave is superimposed between the vibrating membrane and the fixed electrode; At the end of driving of the type transducer, in order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage, the DC bias voltage for residual polarization elimination is applied between the vibration film and the fixed electrode. Do Characterized in that it comprises a stage, a.
In the electrostatic transducer control device of the present invention having the above-described configuration, in the pull-type electrostatic transducer in which the fixed electrode is arranged on one surface side of the vibration membrane, the vibration membrane is fixed when the electrostatic transducer is driven. Since a DC bias is applied between the electrodes, remanent polarization occurs in the dielectric film of the vibration film. For this reason, a DC bias voltage for canceling this residual polarization is applied at the end of driving of the electrostatic transducer.
As a result, even when the pull-type electric transducer is driven at the maximum or an input / output value close to it, the same output characteristics can be obtained under the same driving conditions during the subsequent driving.

In addition, the electrostatic transducer control device of the present invention includes a signal wave generating unit that generates a signal wave, a signal wave amplitude adjusting unit that adjusts the amplitude of the signal wave, and a positive or negative DC polarity. A DC bias supply unit for supplying a bias; a bias voltage compensation unit for adjusting an output voltage of the DC bias supply unit; an output of the signal wave amplitude adjustment unit and a fixed electrode of the electrostatic transducer; and A wiring pattern A connecting the output of the DC bias supply unit and the vibration film of the electrostatic transducer, connecting the output of the signal wave amplitude adjusting unit and the vibration film of the electrostatic transducer, and supplying the DC bias A switch unit for switching between the output of the unit and the wiring pattern B for connecting the fixed electrode of the electrostatic transducer, and a power switch for switching on / off of the power source of the apparatus. A control unit that controls the switching of the wiring pattern A and the wiring pattern B in the switch unit, and a control unit that controls the adjustment of the output voltage of the DC bias supply unit in the bias voltage adjusting unit. And
The electrostatic transducer control device of the present invention having the above-described configuration is configured to switch between the wiring pattern A and the wiring pattern B as a wiring pattern for applying a voltage to the fixed electrode and the vibration film of the electrostatic transducer. Yes. The wiring pattern A is a wiring pattern in which the output terminal of the signal wave amplitude adjustment unit and the fixed electrode of the electrostatic transducer are wired, and the output terminal of the DC bias supply unit and the vibration film of the electrostatic transducer are wired. The wiring pattern B is a wiring pattern in which the output terminal of the signal wave amplitude adjusting unit and the vibrating membrane of the electrostatic transducer are wired, and the output terminal of the DC bias supply unit and the fixed electrode of the electrostatic transducer are wired. . For example, the wiring pattern A is used when the electrostatic transducer is driven, and the wiring pattern B is selected when the electrostatic transducer is driven. Further, the DC bias voltage is adjusted according to the wiring pattern A and the wiring pattern B.
Thereby, at the end of driving of the electrostatic transducer, a DC bias voltage having a polarity opposite to that at the time of driving can be applied to the dielectric film of the vibration film, and the residual polarization of the dielectric film is canceled (0 or To a value close to 0). For this reason, even when the pull-type electric transducer is driven at the maximum or an input / output value close to it, the same output characteristics can be obtained under the same driving conditions during the subsequent driving.

Also, the electrostatic transducer control device of the present invention selects the wiring pattern A when the electrostatic transducer is driven, and selects the wiring pattern B when the electrostatic transducer is driven, so that the residual polarization is selected. Or the wiring pattern B is selected when the electrostatic transducer is driven, and the wiring pattern A is selected when the electrostatic transducer is driven to erase the residual polarization. It is characterized by that.
In the electrostatic transducer control device of the present invention configured as described above, the output terminal of the signal wave amplitude adjustment unit and the fixed electrode of the electrostatic transducer are wired, and the output terminal of the DC bias supply unit and the electrostatic transducer A wiring pattern A for wiring the vibration film is provided. In addition, a wiring pattern B is provided for wiring the output terminal of the signal wave amplitude adjusting unit and the vibration film of the electrostatic transducer, and wiring the output terminal of the DC bias supply unit and the fixed electrode of the electrostatic transducer. The wiring pattern A is selected when the electrostatic transducer is driven, and the wiring pattern B is selected when the electrostatic transducer is driven. Alternatively, the wiring pattern B is selected when the electrostatic transducer is driven, and the wiring pattern A is selected when the electrostatic transducer is driven.
As a result, the combination of the wiring pattern at the time of driving the electrostatic transducer and the wiring pattern at the end of driving can be selected from two types, and the residual polarization of the dielectric film can be canceled (0 or close to 0). Value).

The electrostatic transducer control device according to the present invention includes a signal wave generating unit that generates a signal wave, a signal wave amplitude adjusting unit that adjusts the amplitude of the signal wave, and three output terminals of positive, negative, and ground. A DC bias supply unit that arbitrarily selects and supplies a positive or negative DC bias according to the connection method of the three output terminals, a bias voltage adjustment unit that adjusts the output voltage of the DC bias, and the DC bias A switch unit for switching the wiring of the three output terminals of the supply unit to a wiring pattern a for short-circuiting the negative and the ground, a wiring pattern b for short-circuiting the positive and the ground, and a power switch unit for switching on / off the power of the device The wiring pattern a is selected in the switch unit according to the state of the power switch unit, and the positive output of the DC bias supply unit is connected to the diaphragm. And, the wiring pattern A that connects the output of the signal wave amplitude adjusting unit and the fixed electrode, the wiring pattern b is selected in the switch unit, and the negative output of the DC bias supply unit is connected to the diaphragm And control for switching the output of the signal wave amplitude adjustment unit and the wiring pattern B connecting the fixed electrode, and a control unit for controlling adjustment of the output voltage of the DC bias supply unit in the bias voltage adjustment unit, It is characterized by providing.
In the electrostatic transducer control device of the present invention having the above-described configuration, a DC bias voltage in which a signal wave is superimposed is applied between the fixed electrode of the electrostatic transducer and the vibrating membrane. The DC bias supply unit that supplies the DC bias voltage is a power source that supplies a positive or negative DC bias according to a method of connecting output terminals. In general, there are three output terminals of such a DC power source: a positive electrode, a negative electrode, and a ground. When a positive DC bias is to be supplied, the DC bias positive output terminal is connected to one end of the load, and the DC bias negative and ground terminals are both connected to the other terminal of the load. Conversely, when it is desired to supply a negative DC bias, the negative output terminal of the DC bias is connected to one end of the load, and both the positive and ground terminals of the DC bias are connected to the other terminal of the load. Then, when driving the electrostatic transducer, for example, the wiring pattern A is selected. In this wiring pattern A, a positive DC bias is supplied from the DC bias supply unit, the positive output of the DC bias supply unit is connected to the vibration film, and the output of the signal wave amplitude adjustment unit is connected to the fixed electrode. To do. At the end of driving of the electrostatic transducer, the wiring pattern B is selected. In this wiring pattern B, a negative DC bias is supplied from the DC bias supply unit, the negative output of the DC bias supply unit is connected to the vibration film, and the output of the signal wave amplitude adjustment unit is connected to the fixed electrode. To do.
Thereby, at the end of driving of the electrostatic transducer, a DC bias voltage having a polarity opposite to that at the time of driving can be applied to the dielectric film of the vibration film, and the residual polarization of the dielectric film is canceled (0 or To a value close to 0). For this reason, even when the pull-type electric transducer is driven at the maximum or an input / output value close to it, the same output characteristics can be obtained under the same driving conditions during the subsequent driving.

Also, the electrostatic transducer control device of the present invention selects the wiring pattern A when the electrostatic transducer is driven, and selects the wiring pattern B when the electrostatic transducer is driven, so that the residual polarization is selected. Or the wiring pattern B is selected when the electrostatic transducer is driven, and the wiring pattern A is selected when the electrostatic transducer is driven to erase the residual polarization. It is characterized by that.
The electrostatic transducer control device of the present invention having the above-described configuration includes the wiring pattern A that connects the positive output of the DC bias supply unit to the vibrating membrane and connects the output of the signal wave amplitude adjusting unit and the fixed electrode. . Further, a wiring pattern B is provided that connects the negative output of the DC bias supply unit to the vibrating membrane and connects the output of the signal wave amplitude adjusting unit and the fixed electrode. The wiring pattern A is selected when the electrostatic transducer is driven, and the wiring pattern B is selected when the electrostatic transducer is driven. Alternatively, the wiring pattern B is selected when the electrostatic transducer is driven, and the wiring pattern A is selected when the electrostatic transducer is driven.
As a result, the combination of the wiring pattern at the time of driving the electrostatic transducer and the wiring pattern at the end of driving can be selected from two types, and the residual polarization of the dielectric film can be canceled (0 or close to 0). Value).

The electrostatic transducer control device according to the present invention includes a signal wave generating unit that generates a signal wave, a signal wave amplitude adjusting unit that adjusts the amplitude of the signal wave, and a first DC bias that supplies a positive DC bias. A DC bias supply unit; a first bias voltage adjustment unit that adjusts an output voltage of the first DC bias supply unit; a second DC bias supply unit that supplies a negative DC bias; and the second DC bias A second bias voltage adjusting unit that adjusts an output voltage of the bias supply unit; a switch unit that selects one of the output terminals of the first DC bias supply unit and the second DC bias supply unit; According to the state of the power switch unit that switches power on and off, and the state of the power switch unit, the switch unit selects the output terminal of the first DC bias supply unit, and the selected first A wiring pattern A for connecting the output of the C bias supply unit to the diaphragm and the output of the signal wave amplitude adjustment unit to the fixed electrode, and an output terminal of the second DC bias supply unit in the switch unit Selecting and selecting the wiring pattern B that connects the output of the selected second DC bias supply unit to the vibrating membrane and connects the output of the signal wave amplitude adjustment unit to the fixed electrode; A control unit that controls adjustment of output voltages of the first DC bias supply unit and the second DC bias supply unit in the first bias voltage adjustment unit and the second bias voltage adjustment unit. .
In the electrostatic transducer control device of the present invention having the above-described configuration, a DC bias voltage in which a signal wave is superimposed is applied between the fixed electrode of the electrostatic transducer and the vibrating membrane. The DC bias supply unit that supplies the DC bias voltage includes a first DC bias supply unit that supplies a positive DC bias, and a second DC bias supply unit that supplies a negative DC bias. The wiring pattern A is selected when the electrostatic transducer is driven, and the wiring pattern B is selected when the electrostatic transducer is driven. In the wiring pattern A, the first DC bias supply unit (positive output) is selected, the output of the first DC bias supply unit is connected to the vibrating membrane, and the output of the signal wave amplitude adjustment unit is used as the fixed electrode. Connect with. In the wiring pattern B, the second DC bias supply unit (negative output) is selected, the output of the second DC bias supply unit is connected to the vibration film, and the output of the signal wave amplitude adjustment unit is fixed. Connect with electrodes.
Thereby, at the end of driving of the electrostatic transducer, a DC bias voltage having a polarity opposite to that at the time of driving can be applied to the dielectric film of the vibration film, and the residual polarization of the dielectric film is canceled (0 or To a value close to 0). For this reason, even when the pull-type electric transducer is driven at the maximum or an input / output value close to it, the same output characteristics can be obtained under the same driving conditions during the subsequent driving.

Also, the electrostatic transducer control device of the present invention selects the wiring pattern A when the electrostatic transducer is driven, and selects the wiring pattern B when the electrostatic transducer is driven, so that the residual polarization is selected. Or the wiring pattern B is selected when the electrostatic transducer is driven, and the wiring pattern A is selected when the electrostatic transducer is driven to erase the residual polarization. It is characterized by that.
In the electrostatic transducer control device of the present invention configured as described above, the output of the first DC bias supply unit (positive output) is connected to the vibrating membrane, and the output of the signal wave amplitude adjusting unit is connected to the fixed electrode. The wiring pattern A is provided. In addition, a wiring pattern B is provided that connects the output of the second DC bias supply unit (negative output) to the vibrating membrane and connects the output of the signal wave amplitude adjustment unit to the fixed electrode. The wiring pattern A is selected when the electrostatic transducer is driven, and the wiring pattern B is selected when the electrostatic transducer is driven. Alternatively, the wiring pattern B is selected when the electrostatic transducer is driven, and the wiring pattern A is selected when the electrostatic transducer is driven.
As a result, the combination of the wiring pattern at the time of driving the electrostatic transducer and the wiring pattern at the end of driving can be selected from two types, and the residual polarization of the dielectric film can be canceled (0 or close to 0). Value).

In the electrostatic transducer control device according to the present invention, the signal wave generated by the signal wave generator is a modulated wave obtained by modulating a carrier wave in an ultrasonic frequency band with a signal wave in an audible frequency band, The electrostatic transducer is an electrostatic ultrasonic transducer that emits ultrasonic waves.
In the electrostatic transducer control device of the present invention having the above-described configuration, the dielectric film is an electrostatic ultrasonic transducer driven by a modulated wave obtained by modulating a carrier wave in the ultrasonic frequency band with a signal wave in the audible frequency band. It is possible to cancel the residual polarization generated in
As a result, even when the pull-type electrostatic ultrasonic transducer is driven at the maximum or an input / output value close to it, the same output characteristics can be obtained under the same driving conditions during the subsequent driving.

The electrostatic transducer control device according to the present invention includes a vibration film configured by sandwiching an electrode film between a first dielectric film and a second dielectric film, and a surface of the first dielectric film. A first fixed electrode disposed on a side of the second dielectric film, and a second fixed electrode disposed on a surface side of the second dielectric film, wherein the first fixed electrode, the second fixed electrode, A voltage is applied between the vibrating membranes to generate an electrostatic force between the first fixed electrode and the vibrating membrane and between the second fixed electrode and the vibrating membrane. An electrostatic transducer control device that applies a first signal wave superimposed on a DC bias voltage between the vibrating membrane and the first fixed electrode when the electrostatic transducer is driven. And a DC bias voltage superimposed between the vibrating membrane and the second fixed electrode. In order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage at the end of driving of the electrostatic transducer and the means for applying the second signal wave whose phase is inverted from the signal wave of 1 Applying a DC bias voltage for eliminating residual polarization of the dielectric film between the vibrating film and the first fixed electrode and between the vibrating film and the second fixed electrode; It is characterized by providing.
In the electrostatic transducer control device of the present invention having the above-described configuration, in the push-pull type electrostatic transducer in which the fixed electrodes are arranged on both sides of the vibration membrane, the vibration membrane and the fixed electrode are driven when the electrostatic transducer is driven. Since a DC bias is applied between the two, a residual polarization occurs in the dielectric film of the vibration film. For this reason, a DC bias voltage for canceling this residual polarization is supplied at the end of driving of the electrostatic transducer.
As a result, even when the push-pull type electric transducer is driven at the maximum or near input / output value, the same output characteristics can be obtained under the same driving conditions at the next and subsequent driving.

The electrostatic transducer control device of the present invention generates a signal wave generation unit that generates a signal wave and a signal whose phase is inverted with respect to the signal wave based on the output signal of the signal wave generation unit. And a signal wave amplitude adjusting unit that simultaneously adjusts the amplitude of the output of the signal wave generating unit and the output signal of the phase inverting unit and outputs the respective signals as a signal wave output A and a signal wave output B, A DC bias supply unit that supplies a positive or negative DC bias, a bias voltage adjustment unit that adjusts an output voltage of the DC bias supply unit, the signal wave output A, and the first fixed electrode A wiring pattern A1 that connects the signal wave output B and the second fixed electrode, and connects the output of the DC bias supply unit and the vibration film of the electrostatic transducer, and the signal wave output A And the second fixed electrode, the signal wave output B and the first fixed electrode are connected, and the output of the DC bias supply unit and the vibration film of the electrostatic transducer are connected. A2, the signal wave output A and the vibrating membrane of the electrostatic transducer are connected, the signal wave output B and the second fixed electrode are connected, and the output of the DC bias supply unit and the first A wiring pattern B for connecting a fixed electrode, a signal wave output A and the first fixed electrode, a signal wave output B and a vibration film of the electrostatic transducer, and the DC bias. A switch unit that switches between an output of the supply unit and a wiring pattern C that connects the second fixed electrode; a power switch unit that switches on and off the power of the apparatus; and A control of switching the over emissions A1, A2, B and C, characterized in that it comprises a control unit for controlling the adjustment of the DC bias supply unit of the output voltage at the bias voltage adjusting unit.
In the electrostatic transducer control device of the present invention having the above-described configuration, when the electrostatic transducer is driven, a DC bias voltage is applied to the vibrating membrane, and the first fixed electrode disposed on both sides of the vibrating membrane and Signal waves whose phases are inverted from each other are applied to the second fixed electrode. The switch unit includes a wiring pattern A1, a wiring pattern A2, and a wiring pattern as wiring patterns for applying a voltage (DC bias and signal wave) to the vibration film, the first fixed electrode, and the second fixed electrode. B and wiring pattern C can be switched. The wiring pattern A1 connects the signal wave output A and the first fixed electrode, connects the signal wave output B and the second fixed electric plate, and outputs the DC bias supply unit and the vibration film of the electrostatic transducer. Is a wiring pattern for connecting the two. The wiring pattern A2 connects the signal wave output A and the second fixed electrode, connects the signal wave output B and the first fixed electrode, and connects the output of the DC bias supply unit and the vibration film of the electrostatic transducer. This is a wiring pattern to be connected. The wiring pattern B connects the signal wave output A and the diaphragm of the electrostatic transducer, connects the signal wave output B and the second fixed electrode plate, and outputs the DC bias supply unit and the first fixed electrode. Is a line pattern for connecting. The wiring pattern C connects the signal wave output A and the first fixed electrode, connects the signal wave output B and the vibration film of the electrostatic transducer, and connects the output of the DC bias supply unit and the second fixed electrode. This is a wiring pattern to be connected. In the switch portion, three wiring patterns A1, B, and C or three wiring patterns A2, B, and C can be selected. Then, for example, the wiring pattern A1 is selected when the electrostatic transducer is driven, the wiring pattern B is first selected, and then the wiring pattern C is selected when the electrostatic transducer is driven.
As a result, at the end of driving of the electrostatic transducer, a DC bias voltage having a polarity opposite to that at the time of driving can be applied to the dielectric film (two dielectric films) of the vibration film, and the dielectric film remains. Polarization can be canceled (or returned to 0 or a value close to 0). For this reason, even when the push-pull type electric transducer is driven at the maximum or an input / output value close thereto, the same output characteristics can be obtained under the same driving conditions during the subsequent driving.

In addition, the electrostatic transducer control device of the present invention selects the wiring pattern A1 when the electrostatic transducer is driven, and selects the wiring pattern B and the wiring pattern C when the electrostatic transducer is driven. Select to erase the remanent polarization, or select the wiring pattern A2 when the electrostatic transducer is driven, and select the wiring pattern B and the wiring pattern C when the electrostatic transducer is driven The remnant polarization is erased.
In the electrostatic transducer control device of the present invention having the above-described configuration, the wiring pattern A1, the wiring pattern A2, the wiring pattern B, and the wiring pattern C can be switched. The wiring pattern A1 connects the signal wave output A and the first fixed electrode, connects the signal wave output B and the second fixed electric plate, and outputs the DC bias supply unit and the vibration film of the electrostatic transducer. Is a wiring pattern for connecting the two. The wiring pattern A2 connects the signal wave output A and the second fixed electrode, connects the signal wave output B and the first fixed electrode, and connects the output of the DC bias supply unit and the vibration film of the electrostatic transducer. This is a wiring pattern to be connected. The wiring pattern B connects the signal wave output A and the diaphragm of the electrostatic transducer, connects the signal wave output B and the second fixed electrode plate, and outputs the DC bias supply unit and the first fixed electrode. Is a line pattern for connecting. The wiring pattern C connects the signal wave output A and the first fixed electrode, connects the signal wave output B and the vibration film of the electrostatic transducer, and connects the output of the DC bias supply unit and the second fixed electrode. This is a wiring pattern to be connected. Then, the wiring pattern A1 is selected at the time of driving the electrostatic transducer, and the wiring pattern B and the wiring pattern C are selected at the end of driving of the electrostatic transducer to eliminate the residual polarization. Alternatively, the wiring pattern A2 is selected when the electrostatic transducer is driven, and the wiring pattern B and the wiring pattern C are selected when the driving of the electrostatic transducer is finished to eliminate the residual polarization.
As a result, the combination of the wiring pattern at the time of driving the electrostatic transducer and the wiring pattern at the end of driving can be selected from two types, and the residual polarization of the dielectric film can be canceled (0 or close to 0). Value).

The electrostatic transducer control device of the present invention generates a signal wave generation unit that generates a signal wave and a signal whose phase is inverted with respect to the signal wave based on the output signal of the signal wave generation unit. And a signal wave amplitude adjusting unit that simultaneously adjusts the amplitude of the output of the signal wave generating unit and the output signal of the phase inverting unit and outputs the respective signals as a signal wave output A and a signal wave output B, A DC bias supply unit having three output terminals of positive, negative, and ground, and selectively supplying positive or negative DC bias according to a method of connecting the three output terminals, and an output voltage of the DC bias A switch for switching the wiring of the three output terminals of the bias voltage adjusting unit to be adjusted and the DC bias supply unit to a wiring pattern a that short-circuits the negative and ground and a wiring pattern b that short-circuits the positive and ground. Unit, a power switch unit for switching on / off the power of the device, and selecting the wiring pattern a in the switch unit according to the state of the power switch unit and the positive output of the DC bias supply unit and the A wiring pattern A for connecting a vibration film, connecting the signal wave output A and the first fixed electrode, and connecting the signal wave output B and the second fixed electrode; and the wiring pattern in the switch section. b is selected, the negative output of the DC bias supply unit is connected to the diaphragm, the signal wave output A is connected to the first fixed electrode, and the signal wave output B is connected to the second fixed electrode. A control unit that switches between the wiring patterns B that connect the electrodes, and a control unit that controls adjustment of the output voltage of the DC bias supply unit in the bias voltage adjustment unit. And butterflies.
In the electrostatic transducer control device of the present invention having the above-described configuration, when the electrostatic transducer is driven, a DC bias voltage is applied to the vibrating membrane, and the first fixed electrode disposed on both sides of the vibrating membrane Signal waves whose phases are inverted from each other are applied to the second fixed electrode. The DC bias supply unit that supplies the DC bias voltage is a power source that supplies a positive or negative DC bias according to a method of connecting output terminals. In general, there are three output terminals of such a DC power source: a positive electrode, a negative electrode, and a ground. When a positive DC bias is to be supplied, the DC bias positive output terminal is connected to one end of the load, and the DC bias negative and ground terminals are both connected to the other terminal of the load. Conversely, when it is desired to supply a negative DC bias, the negative output terminal of the DC bias is connected to one end of the load, and both the positive and ground terminals of the DC bias are connected to the other terminal of the load. Then, when driving the electrostatic transducer, for example, the wiring pattern A is selected. In this wiring pattern A, a positive DC bias is supplied from the DC bias supply unit, the positive output of the DC bias supply unit is connected to the vibration film, and the signal wave output A and the first fixed electrode are connected. At the same time, the signal wave output B and the second fixed electrode are connected. At the end of driving of the electrostatic transducer, the wiring pattern B is selected. In this wiring pattern B, a negative DC bias is supplied from the DC bias supply unit, the negative output of the DC bias supply unit is connected to the vibration film, and the signal wave output A and the first fixed electrode are connected. In addition, the signal wave output B and the second fixed electrode are connected.
Thereby, at the end of driving of the electrostatic transducer, a DC bias voltage having a polarity opposite to that at the time of driving can be applied to the dielectric film of the vibration film, and the residual polarization of the dielectric film is canceled (0 or To a value close to 0). For this reason, even when the push-pull type electric transducer is driven at the maximum or an input / output value close thereto, the same output characteristics can be obtained under the same driving conditions during the subsequent driving.

Also, the electrostatic transducer control device of the present invention selects the wiring pattern A when the electrostatic transducer is driven, and selects the wiring pattern B when the electrostatic transducer is driven, so that the residual polarization is selected. Or the wiring pattern B is selected when the electrostatic transducer is driven, and the wiring pattern A is selected when the electrostatic transducer is driven to erase the residual polarization. It is characterized by that.
In the electrostatic transducer control device of the present invention configured as described above, the positive output terminal of the DC bias supply unit is connected to the vibrating membrane, the signal wave output A and the first fixed electrode are connected, and the signal wave output A wiring pattern A for connecting B and the second fixed electrode is provided. Further, a wiring pattern B for connecting the negative output terminal of the DC bias supply unit to the vibrating membrane, connecting the signal wave output A and the first fixed electrode, and connecting the signal wave output B and the second fixed electrode is provided. Prepare. Then, the wiring pattern A is selected at the time of driving the electrostatic transducer, and the wiring pattern B is selected at the end of the driving of the electrostatic transducer to eliminate the residual polarization. Alternatively, the wiring pattern B is selected at the time of driving the electrostatic transducer, and the wiring pattern B and the wiring pattern C are selected at the end of driving of the electrostatic transducer to eliminate residual polarization.
As a result, the combination of the wiring pattern at the time of driving the electrostatic transducer and the wiring pattern at the end of driving can be selected from two types, and the residual polarization of the dielectric film can be canceled (0 or close to 0). Value).

The electrostatic transducer control device of the present invention generates a signal wave generation unit that generates a signal wave and a signal whose phase is inverted with respect to the signal wave based on the output signal of the signal wave generation unit. And a signal wave amplitude adjusting unit that simultaneously adjusts the amplitude of the output of the signal wave generating unit and the output signal of the phase inverting unit and outputs the respective signals as a signal wave output A and a signal wave output B, A first DC bias supply unit that supplies a positive DC bias; a first bias voltage adjustment unit that adjusts an output voltage of the first DC bias supply unit; and a second DC bias supply unit that supplies a negative DC bias A DC bias supply unit; a second bias voltage adjustment unit that adjusts an output voltage of the second DC bias supply unit; and one of the first DC bias supply unit and the second DC bias supply unit. Output terminal A switch unit for selecting, a power switch unit for switching on / off of the power of the device, and an output terminal of the first DC bias supply unit in the switch unit according to the state of the power switch unit; and The output of the selected first DC bias supply unit is connected to the diaphragm, and the signal wave output A is connected to the first fixed electrode, and the signal wave output B and the second fixed electrode are connected. The output terminal of the second DC bias supply unit is selected in the wiring pattern A and the switch unit, the output of the selected second DC bias supply unit is connected to the vibrating membrane, and the signal wave output A is Control for selecting a wiring pattern B that is connected to the first fixed electrode and connects the signal wave output B to the second fixed electrode, and the first bias voltage adjusting unit and the second bias voltage adjusting unit. Characterized in that it comprises a control unit for controlling the adjustment of the first DC bias supply unit and the second DC bias supply unit of the output voltage at the voltage adjusting unit.
In the electrostatic transducer control device of the present invention having the above-described configuration, when the electrostatic transducer is driven, a DC bias voltage is applied to the vibrating membrane, and the first fixed electrode disposed on both sides of the vibrating membrane and Signal waves whose phases are inverted from each other are applied to the second fixed electrode. The DC bias supply unit that supplies the DC bias voltage includes a first DC bias supply unit that supplies a positive DC bias, and a second DC bias supply unit that supplies a negative DC bias. The wiring pattern A is selected when the electrostatic transducer is driven, and the wiring pattern B is selected when the electrostatic transducer is driven. In this wiring pattern A, the first DC bias supply unit (positive output) is selected, the output of the first DC bias supply unit is connected to the vibrating membrane, and the signal wave output A and the first fixed electrode are connected. The signal wave output B and the second fixed electrode are connected together with the connection. In the wiring pattern B, the second DC bias supply unit (negative output) is selected, the output of the second DC bias supply unit is connected to the vibration film, and the signal wave output A and the first fixed electrode are connected. And the signal wave output B and the second fixed electrode are connected.
Thereby, at the end of driving of the electrostatic transducer, a DC bias voltage having a polarity opposite to that at the time of driving can be applied to the dielectric film of the vibration film, and the residual polarization of the dielectric film is canceled (0 or To a value close to 0). For this reason, even when the push-pull type electric transducer is driven at the maximum or an input / output value close thereto, the same output characteristics can be obtained under the same driving conditions during the subsequent driving.

Also, the electrostatic transducer control device of the present invention selects the wiring pattern A when the electrostatic transducer is driven, and selects the wiring pattern B when the electrostatic transducer is driven, so that the residual polarization is selected. Or the wiring pattern B is selected when the electrostatic transducer is driven, and the wiring pattern A is selected when the electrostatic transducer is driven to erase the residual polarization. It is characterized by that.
In the electrostatic transducer control device of the present invention configured as described above, the output of the first DC bias supply unit (positive output) is connected to the vibrating membrane, and the signal wave output A and the first fixed electrode are connected. And a wiring pattern A for connecting the signal wave output B and the second fixed electrode. In addition, the output of the second DC bias supply unit (negative output) is connected to the vibrating membrane, and the signal wave output A and the first fixed electrode are connected, and the signal wave output B and the second fixed electrode are connected. Wiring pattern B to be provided. The wiring pattern A is selected when the electrostatic transducer is driven, and the wiring pattern B is selected when the electrostatic transducer is driven. Alternatively, the wiring pattern B is selected when the electrostatic transducer is driven, and the wiring pattern A is selected when the electrostatic transducer is driven.
As a result, the combination of the wiring pattern at the time of driving the electrostatic transducer and the wiring pattern at the end of driving can be selected from two types, and the residual polarization of the dielectric film can be canceled (0 or close to 0). Value).

In the electrostatic transducer control device according to the present invention, the signal wave generated by the signal wave generator is a modulated wave obtained by modulating a carrier wave in an ultrasonic frequency band with a signal wave in an audible frequency band, The electrostatic transducer is an electrostatic ultrasonic transducer that emits ultrasonic waves.
In the electrostatic transducer control device of the present invention having the above-described configuration, in a push-pull electrostatic ultrasonic transducer driven by a modulated wave obtained by modulating a carrier wave in an ultrasonic frequency band with a signal wave in an audible frequency band. The residual polarization generated in the dielectric film can be canceled.
As a result, even when the push-pull type electrostatic ultrasonic transducer is driven at the maximum or an input / output value close thereto, an equivalent output characteristic can be obtained under the same driving conditions during the subsequent driving.

According to another aspect of the present invention, there is provided a method for controlling an electrostatic transducer, comprising: a vibration film having an electrode film formed on a dielectric film; and a fixed electrode disposed on a surface side of the dielectric film of the vibration film, A method for controlling an electrostatic transducer configured to generate an electrostatic force between a fixed electrode and the diaphragm by applying a voltage between the fixed electrode and the diaphragm. By applying a DC bias voltage in which a signal wave is superimposed between the vibrating membrane and the fixed electrode when driving the electric transducer, and by applying the DC bias voltage at the end of driving the electrostatic transducer Applying a DC bias voltage for erasing the residual polarization between the vibration film and the fixed electrode in order to cancel the generated residual polarization of the dielectric film.
In the electrostatic transducer control method of the present invention including the above procedure, in the pull-type electrostatic transducer in which the fixed electrode is disposed on one surface side of the vibration membrane, the vibration membrane is fixed when the electrostatic transducer is driven. Since a DC bias is applied between the electrodes, remanent polarization occurs in the dielectric film of the vibration film. For this reason, a DC bias voltage for canceling this residual polarization is applied at the end of driving of the electrostatic transducer.
As a result, even when the pull-type electric transducer is driven at the maximum or an input / output value close to it, the same output characteristics can be obtained under the same driving conditions during the subsequent driving.

The electrostatic transducer control method of the present invention includes a vibrating film configured by sandwiching an electrode film between a first dielectric film and a second dielectric film, and a surface of the first dielectric film. A first fixed electrode disposed on a side of the second dielectric film, and a second fixed electrode disposed on a surface side of the second dielectric film, the first fixed electrode, the second fixed electrode, and the vibration An electrostatic force is configured to generate an electrostatic force between the first fixed electrode and the vibrating membrane and between the second fixed electrode and the vibrating membrane by applying a voltage between the membranes. A method for controlling an electric transducer, wherein a first signal wave is applied to a DC bias voltage superimposed between the vibrating membrane and the first fixed electrode when the electrostatic transducer is driven. , And superimposed on a DC bias voltage between the vibrating membrane and the second fixed electrode. In order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage at the end of driving of the electrostatic transducer and the procedure of applying the second signal wave whose phase is inverted from the signal wave of Applying a DC bias voltage for eliminating residual polarization of the dielectric film between the vibrating film and the first fixed electrode and between the vibrating film and the second fixed electrode; It is characterized by including.
In the method for controlling an electrostatic transducer according to the present invention including the above procedure, in the push-pull electrostatic transducer in which fixed electrodes are arranged on both sides of the vibrating membrane, the vibrating membrane and the fixed electrode are driven when the electrostatic transducer is driven. Since a DC bias is applied between the two, a residual polarization occurs in the dielectric film of the vibration film. For this reason, a DC bias voltage for canceling this residual polarization is applied at the end of driving of the electrostatic transducer.
As a result, even when the push-pull type electric transducer is driven at the maximum or near input / output value, the same output characteristics can be obtained under the same driving conditions at the next and subsequent driving.

The ultrasonic speaker according to the present invention modulates a carrier wave in an ultrasonic frequency band with a signal wave output from a signal generation source that generates a signal wave in an audible frequency band, and drives an electrostatic transducer with the modulated wave. An ultrasonic speaker that reproduces a signal sound in an audible frequency band, and an electrostatic transducer includes a vibration film in which an electrode film is formed on a dielectric film, and a surface of the vibration film on the surface of the dielectric film. A DC bias in which a signal wave is superimposed between the vibrating membrane and the fixed electrode when the electrostatic transducer is driven. Means for applying a voltage, and at the end of driving of the electrostatic transducer, in order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage, the vibrating membrane and the fixed Characterized in that it comprises, means for applying a DC bias voltage for the residual polarization canceling between the poles.
In the ultrasonic speaker of the present invention configured as described above, an ultrasonic speaker that modulates a carrier wave (carrier wave) in the ultrasonic frequency band with a signal wave in the audible frequency band and drives a pull-type electrostatic transducer with the modulated wave. The apparatus for controlling an electrostatic transducer according to the present invention is used. In this electrostatic transducer control device, in order to cancel the residual polarization of the dielectric film that occurs when the electrostatic transducer is driven, a DC bias voltage for residual polarization elimination is applied at the end of the driving of the electrostatic transducer.
Accordingly, even when an ultrasonic speaker using a pull-type electric transducer is driven at the maximum or near input / output value, an equivalent output characteristic can be obtained under the same driving condition at the next and subsequent driving. For this reason, in an ultrasonic speaker using a pull-type electrostatic transducer, the vibrating membrane can be vibrated with high efficiency, so that a high sound pressure can be obtained. Therefore, it is possible to realize an ultrasonic speaker that can generate an acoustic signal having a sound pressure level sufficient to obtain the parametric array effect.

The ultrasonic speaker according to the present invention modulates a carrier wave in an ultrasonic frequency band with a signal wave output from a signal source that generates a signal wave in an audible frequency band, and drives an electrostatic transducer with the modulated wave. An ultrasonic speaker that reproduces a signal sound in an audible frequency band, wherein the electrostatic transducer includes a vibration film configured by sandwiching an electrode film between a first dielectric film and a second dielectric film; A first fixed electrode disposed on the surface side of the first dielectric film; and a second fixed electrode disposed on the surface side of the second dielectric film; and the electrostatic transducer When the electrostatic transducer is driven, the control device applies a first signal wave superimposed on a DC bias voltage between the vibrating membrane and the first fixed electrode, and the vibrating membrane Between the first fixed electrode and the second fixed electrode Means for applying a second signal wave having a phase inverted from that of the first signal wave superimposed on the bias voltage, and the dielectric generated by the application of the DC bias voltage at the end of driving of the electrostatic transducer In order to cancel the residual polarization of the film, a DC for eliminating residual polarization of the dielectric film is provided between the vibration film and the first fixed electrode and between the vibration film and the second fixed electrode. Means for applying a bias voltage.
In the ultrasonic speaker of the present invention having the above-described configuration, an ultrasonic wave that modulates a carrier wave (carrier wave) in the ultrasonic frequency band with a signal wave in the audible frequency band and drives a push-pull electrostatic transducer with the modulated wave. In the speaker, the electrostatic transducer control device of the present invention is used. In this electrostatic transducer control device, in order to cancel the residual polarization of the dielectric film that occurs when the electrostatic transducer is driven, a DC bias voltage for residual polarization elimination is applied at the end of the driving of the electrostatic transducer.
As a result, even when an ultrasonic speaker using a push-pull type electric transducer is driven at the maximum or near input / output value, the same output characteristics can be obtained under the same driving conditions during the next and subsequent driving. . For this reason, in an ultrasonic speaker using a push-pull type electrostatic transducer, the vibrating membrane can be vibrated with high efficiency, so that a high sound pressure can be obtained. Therefore, it is possible to realize an ultrasonic speaker that can generate an acoustic signal having a sound pressure level sufficient to obtain the parametric array effect.

When the electrostatic transducer is driven, since a DC bias voltage is applied to the vibration film, residual polarization occurs in the dielectric film of the vibration film. The magnitude of this remanent polarization is determined by the type of dielectric (dielectric constant, film thickness, etc.). In the electrostatic transducer control device of the present invention, a DC bias voltage necessary for setting the residual polarization of the dielectric film to 0 (zero) or a value close thereto is applied at the end of driving of the electrostatic transducer. Configured. The electrostatic transducer control device of the present invention is configured to be applied to a pull-type electrostatic transducer and a push-pull electrostatic transducer.
Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Description of pull-type and push-pull type electrostatic transducers]
As described above, when the electrostatic transducer is driven at the maximum or close to the output value, there is a problem that a larger DC bias is required in order to obtain an equivalent output characteristic at the next and subsequent driving. .

  Therefore, in the present invention, even when the electrostatic transducer is driven at the maximum or close to the input / output value, it is possible to control the electrostatic transducer that can obtain the same output characteristics under the same driving conditions at the next and subsequent driving. An example of an apparatus is shown.

  Moreover, as a typical system of the electrostatic transducer, there are a pull type and a push-pull type. Therefore, in the embodiment of the present invention, an example in which a pull type and a push-pull type are used as an electrostatic transducer will be described. Hereinafter, the structure and driving principle of pull-type and push-pull electrostatic transducers will be briefly described.

FIG. 1A shows a schematic configuration diagram of a pull-type electrostatic transducer.
When a voltage is applied to two electrodes that are parallel to each other, an electrostatic attractive force acts on the electrodes. Here, one of the two electrodes is made of an electrode (hereinafter referred to as a fixed electrode) 11 formed of a metal or the like, and a polymer film (hereinafter referred to as a vibrating membrane) in which a metal (electrode film) is formed by vapor deposition or the like. Consider replacing it with 21).

  In this case, by applying a DC bias voltage (DC bias voltage) to one of the electrodes and applying a signal voltage (AC signal voltage) to the other electrode, the vibration film 31 has a magnitude of electrostatic attraction. Oscillates in response to the change of the signal voltage. At this time, it is possible to output the vibration of the vibration film 31 as a sound wave by opening the through-hole 22 as an air hole in the fixed electrode 21.

  More specifically, the configuration of the electrostatic transducer described above is configured as shown in FIG. 1B, for example. As shown in FIG. 1B, the vibration film 31 is formed by depositing an electrode film 31A made of an aluminum thin film or the like on the dielectric film 31B. The vibration film 31 and the fixed electrode 21 constitute a pull-type electrostatic transducer with the support member 23 interposed therebetween.

  Then, a DC bias voltage (hereinafter, also simply referred to as “DC bias”) is applied to the electrode film 31 </ b> A of the vibration film 31 by the variable voltage DC bias power supply 32. An AC signal (AC drive voltage) from the AC signal source 33 is applied between the electrode film 31 </ b> A of the vibration film 31 and the fixed electrode 21 so as to be superimposed on the DC bias. (Note that a DC bias may be applied to the fixed electrode 21 and an AC signal may be applied to the vibration film 31.)

  Then, the electrostatic force changes (strong and weak) due to the change in the voltage of the AC signal, and the vibrating membrane 31 vibrates due to the balance between the elastic restoring force of the vibrating membrane 31 and the electrostatic force. Then, the sound wave generated by the vibration in the vibration film 31 passes through the through hole 22 of the fixed electrode 21.

  As described above, the electrostatic transducer shown in FIG. 1 is a pull-type electrostatic transducer because the vibrating membrane 31 receives an electrostatic attractive force from one direction and vibrates with an electrostatic attractive force and an elastic restoring force. Called.

  The AC signal output from the AC signal source 33 may be an audio frequency band signal, or a modulated wave signal obtained by modulating a carrier wave in the ultrasonic frequency band with a signal wave in the audio frequency band. Also good. When the signal applied to the electrostatic transducer is a signal in the ultrasonic frequency band, the electrostatic transducer emits a sound wave in the ultrasonic frequency band, and is also referred to as a pull-type electrostatic ultrasonic transducer.

FIG. 2 shows a schematic diagram of a push-pull electrostatic transducer.
As shown in FIG. 2A, two electrodes 21A and 21B having air holes are prepared and installed in parallel to each other. In the meantime, the vibration film 31 in which the polymer film (dielectric film) is formed on both surfaces of the metal thin film (electrode film) is sandwiched. By applying a DC bias to the metal thin film (electrode film 31A) of the vibration film 31 and applying signal voltages whose phases are inverted to each other to the two fixed electrodes 21A and 21B, static vibration is generated between the vibration film and each electrode. Electrosuction force and electrostatic repulsion force work simultaneously. Further, the electrostatic attractive force and the electrostatic repulsive force change to an electrostatic repulsive force and an electrostatic attractive force, respectively, when the polarity of the signal voltage is reversed. Therefore, the vibrating membrane vibrates according to the change in the polarity of the signal voltage, and it is possible to output sound waves from the air hole of the fixed electrode.

  More specifically, the configuration of the electrostatic transducer described above is configured as shown in FIG. 2B, for example. As shown in FIG. 2B, the fixed electrode A 21 A and the fixed electrode B 21 B are arranged via the support member 23 so as to sandwich the vibration film 31. In addition, the through hole 22A of the fixed electrode A21A and the through hole 22B of the fixed electrode B21B are arranged at a pair.

  The variable voltage DC bias power supply 32 is a power supply for applying a DC bias to the electrode film 31 </ b> A of the vibration film 31. The AC signal sources 33A and 33B output an AC signal (AC drive signal) for vibrating the vibration film 31. The AC signal source 33A outputs an AC signal applied to the fixed electrode A21A, and the AC signal source 33B outputs an AC signal applied to the fixed electrode B21B.

  With the above-described configuration, AC signals having the same amplitude and the phases inverted from each other are applied to the fixed electrode A21A and the fixed electrode B21B. Further, a DC bias is applied to the electrode film 31A by a DC bias power source 32.

  In this way, by applying a DC bias to the electrode film 31A and applying AC signals whose phases are reversed to the fixed electrode A21A and the fixed electrode 21B, the electrostatic attraction force and electrostatic repulsion are applied to the vibration film 31. Forces act simultaneously in the same direction. Each time the polarity of the AC signal is reversed, the direction in which the electrostatic attractive force and the electrostatic repulsive force are applied changes, so that the vibration film 31 is driven by push-pull. As a result, the sound wave generated in the vibration film 31 is released to the outside through the through holes 22A and 12B provided in the fixed electrode A21A and the fixed electrode B21B.

  As described above, the electrostatic transducer shown in FIG. 2 is called a push-pull electrostatic transducer because the vibration film 31 is push-pull driven by the electro-attraction force and the electrostatic repulsion force.

  The AC signal output from the AC signal sources 33A and 33B may be an audible frequency band signal, or a modulated wave signal obtained by modulating an ultrasonic frequency band carrier wave with an audible frequency band signal wave. There may be. When the signal applied to the electrostatic transducer is a signal in the ultrasonic frequency band, the electrostatic transducer emits a sound wave in the ultrasonic frequency band, and is also referred to as a push-pull electrostatic ultrasonic transducer.

[First Embodiment]
FIG. 3 is a diagram showing the configuration of the electrostatic transducer control device according to the first embodiment of the present invention, and is a configuration example of the DC bias control device in the pull-type electrostatic transducer described above. .

  The electrostatic transducer control device shown in FIG. 3 includes a signal wave generation unit 101 that generates a signal wave, a signal wave amplitude adjustment unit 102 that adjusts the amplitude of the signal wave, and a positive or negative DC polarity. A DC bias supply unit 103 that supplies a bias and a bias voltage adjustment unit 104 that adjusts an output voltage of the DC bias supply unit are provided.

  In addition, a switch unit 105 that switches between the wiring pattern A and the wiring pattern B is provided. Here, the wiring pattern A connects the output of the signal wave amplitude adjusting unit 102 and the fixed electrode 21 of the electrostatic transducer, and connects the output of the DC bias supply unit 103 and the vibrating membrane of the electrostatic transducer. It is. The wiring pattern B is a wiring pattern that connects the output of the signal wave amplitude adjustment unit 102 and the vibration film 31 of the electrostatic transducer, and connects the output of the DC bias supply unit 103 and the fixed electrode 21 of the electrostatic transducer. .

  In addition, a power switch unit 106 that switches on and off the power of the DC bias control device is provided. In addition, the switch unit 105 has a control unit 107 that controls the wiring patterns A and B to be switched and also controls the adjustment of the output voltage of the DC bias supply unit 103 in the bias voltage adjustment unit 104. Further, as the electrostatic transducer, the pull-type electrostatic transducer 11 shown in FIG. 1 is provided.

  In the DC bias control device shown in FIG. 3, a signal voltage is generated from the signal wave generation unit 101, and the amplitude of the signal wave amplitude adjustment unit 102 is adjusted. Next, the DC bias supply unit 103 is a power source that supplies a positive or negative DC bias. In the first embodiment of the present invention, a positive DC bias can be supplied. The bias voltage adjustment unit 104 is an adjustment unit for adjusting the output voltage of the DC bias supply unit 103.

  In the configuration shown in FIG. 3, the bias voltage adjustment unit 104 is configured to be able to adjust the output voltage of the DC bias supply unit 103 based on a signal from the control unit 107 described later.

  The switch unit 105 is a part for switching the wiring pattern between the output from the signal wave amplitude adjusting unit 102 and the output from the DC bias supply unit 103 and the fixed electrode 21 and the vibration film 31 of the electrostatic transducer.

  In the first embodiment, the wiring pattern A and the wiring pattern B are provided as the wiring patterns to be switched. As described above, the wiring pattern A is wired to the output terminal of the signal wave amplitude adjustment unit 102 and the fixed electrode 21 of the electrostatic transducer, and the output terminal of the DC bias supply unit 103 and the vibration film 31 of the electrostatic transducer. This is a wiring pattern for wiring. The wiring pattern B is a wiring pattern in which the output terminal of the signal wave amplitude adjusting unit 102 and the vibration film 31 of the electrostatic transducer are wired, and the output terminal of the DC bias supply unit 103 and the fixed electrode 21 of the electrostatic transducer are wired. It is.

  The switch unit 105 is configured so that the wiring pattern A and the wiring pattern B can be selected. Since a large voltage is applied to the switch unit 105, a high voltage relay switch or the like is used (of course, a high voltage power semiconductor element or the like may be used).

  The power switch unit 106 is an on / off switch for controlling whether power is supplied to the system that drives the electrostatic transducer. In the first embodiment, in particular, when the power switch unit 106 is turned from on to off, the power supply is stopped after the DC bias control sequence described later is completed.

  The control unit 107 controls switching of the wiring patterns A and B prepared by the switch unit 105 according to the state of the power switch unit 106, and adjusts the output voltage of the DC bias supply unit 103 in the bias voltage adjustment unit 104. It is a control part for controlling.

FIG. 4 shows a control sequence of the control unit 107 in this embodiment.
Here, there are two typical methods for driving the pull-type electrostatic speaker. The first method is a method in which a DC bias is applied to the vibrating membrane and a signal voltage is applied to the fixed electrode to cause an electrostatic force (attraction) to vibrate, thereby vibrating the vibrating membrane. As a second method, there is a method in which a DC bias is applied to the fixed electrode and a signal voltage is applied to the vibration film to cause an electrostatic force (attraction) to vibrate, thereby vibrating the vibration film. In the first embodiment of the present invention, the electrostatic transducer is driven by the configuration using the first method described above.

  As shown in FIG. 4, when the power switch unit 106 is turned on (power switch ON), the control unit 107 outputs a high ('1') as a 1-bit digital signal to the switch unit 105. Based on the signal, the switch unit 105 switches to the pattern A wiring. In this wiring pattern A, a DC bias is applied to the vibration film 31.

Here, it is considered that the DC bias applied to the vibration film 31 is increased from 0 when the amplitude value of the signal voltage applied to the fixed electrode 21 is constant. At this time, the output sound pressure level of the electrostatic transducer increases, but saturates at a certain sound pressure level. The voltage value of the DC bias at this time is V _1.

As described above, the output level of the electrostatic transducer is maximized when the DC bias is set to V ₁ volt. By applying a voltage of V ₁ volt, the dielectric of the diaphragm is shown in FIG. The remanent polarization occurs in the relationship shown in FIG. Due to this remanent polarization, when the electrostatic transducer drive system is once shut down and then turned on again, the output level obtained will be small even if a DC bias of the same magnitude as the previous drive is applied. There is a problem that it ends up. A voltage (determined by the type of dielectric) necessary to cancel the residual polarization of the dielectric of the electrode film generated when V ₁ volt is applied is defined as V ₂ .

As described above, the control unit 107 sets the wiring pattern to A in the switch unit 105, and then applies an analog or digital signal voltage to the bias voltage adjustment unit 104 so as to increase the positive DC bias from 0 to V ₁ volt. Output.

Further, as shown in FIG. 4, when the power switch unit 106 is turned from on to off (power switch OFF), the control unit 107 adjusts the bias voltage adjustment unit so as to lower the DC bias from V ₁ to 0 volts. 104 is controlled.

Thereafter, low ('0') is output to the switch unit 105 as a 1-bit digital signal, and the wiring pattern is switched to B. Thereafter, the control unit 107 outputs an analog or digital signal voltage to the bias voltage adjustment unit 104 so that the DC bias is changed from 0 to a positive V ₂ volts. Here, since both the DC biases V ₁ and V ₂ are supplied from the DC bias supply unit 103, both have positive polarity in the example shown in FIG. However, since the wiring pattern is switched from A to the wiring pattern B, V ₁ and V ₂ apply electric fields in opposite directions to the dielectric of the vibrating membrane.

  Therefore, after the above operation is performed, the residual polarization of the dielectric film 31B of the vibration film 31 is canceled by returning the DC bias output to 0, and returns to 0 or a state close thereto. The control unit 107 finally controls the switch unit 105 to return the wiring pattern to A, and completely turns off the system power.

  By using such an electrostatic transducer control device, it is possible to stably obtain the maximum output value by applying the same DC bias each time the electrostatic transducer is driven.

  Further, in the first embodiment, the example shown in FIG. 4 is shown as an example of the control sequence of the DC bias, but the pattern of FIG.

  The control sequence shown in FIG. 5 only reverses the order of the wiring pattern A and the wiring pattern B shown in FIG.

  Further, even when the DC bias supply unit 103 supplies a negative output voltage, it is possible to cope with the same concept.

[Second Embodiment]
FIG. 6 is a diagram showing the configuration of the electrostatic transducer control apparatus according to the second embodiment of the present invention, and is a configuration example of the DC bias control apparatus in the pull-type electrostatic transducer described above. .

  The electrostatic transducer control device shown in FIG. 6 includes a signal wave generating unit 201 that generates a signal wave and a signal wave amplitude adjusting unit 202 that adjusts the amplitude of the signal wave. The DC bias supply unit 203 has three output terminals of positive, negative, and ground, and selectively supplies positive or negative DC bias according to the connection method of the three output terminals, and an output voltage of the DC bias. And a bias voltage adjustment unit 204 for adjustment.

  In addition, the DC bias supply unit 203 includes a switch unit 205 that switches the wirings of the three output terminals to a wiring pattern A that short-circuits negative and ground and a wiring pattern B that short-circuits positive and ground. In addition, a power switch unit 206 that switches on / off the power of the electrostatic transducer control device, and a control unit 207 that switches the wiring pattern A and the wiring pattern B in the switch unit 205 according to the state of the power switch unit 206, have. The control unit 207 also has a function of controlling adjustment of the output voltage of the DC bias supply unit 203 in the bias voltage adjustment unit 204. Further, as the electrostatic transducer, the pull-type electrostatic transducer 11 shown in FIG. 1 is provided.

  The signal wave generator 201 is a signal source for generating sound waves from the pull-type electrostatic transducer 11. As an example of the signal wave generating unit 201, an oscillator is used when outputting a single sine wave, and a CD player is used when outputting a voice or music signal.

  The amplitude of the signal voltage generated from the signal wave generating unit 201 is adjusted by the signal wave amplitude adjusting unit 202. In general, since the value of the output voltage obtained from a CD player or the like is small, the output signal is amplified by an amplifier that can arbitrarily change the amplification factor. Therefore, an example of the signal wave amplitude adjusting unit 202 is an amplifier.

  Next, the DC bias supply unit 203 is a power source that supplies a positive or negative DC bias depending on a method of connecting output terminals. In general, there are three output terminals of such a DC power source: a positive electrode, a negative electrode, and a ground. When a positive DC bias is to be supplied, the DC bias positive output terminal is connected to one end of the load, and the DC bias negative and ground terminals are both connected to the other terminal of the load. Conversely, when it is desired to supply a negative DC bias, the negative output terminal of the DC bias is connected to one end of the load, and both the positive and ground terminals of the DC bias are connected to the other terminal of the load.

  The bias voltage adjustment unit 204 is an adjustment unit for adjusting the output voltage of the DC bias supply unit 203. Examples of the bias voltage adjustment unit 204 include a trimmer that is manually adjusted and a configuration that controls output based on the magnitude of a voltage supplied from the outside. In the configuration example shown in FIG. 6, the bias voltage adjustment unit 204 is configured to be able to adjust the output voltage of the DC bias supply unit 203 based on a signal from the control unit 207 described later.

  The switch unit 205 is a part that switches the wiring patterns of the three output terminals of the DC bias supply unit 203 described above so that the polarity of the DC bias output from the DC bias supply unit 203 can be selected.

  In the configuration example shown in FIG. 6, two output terminals of the DC bias supply unit 203 include two wiring patterns, a wiring pattern A that short-circuits negative and ground, and a wiring pattern B that short-circuits positive and ground. Can be selected. In addition, since a large voltage is applied to the switch unit 205, for example, a high breakdown voltage relay switch can be used (of course, a high breakdown voltage power semiconductor element can also be used).

  The power switch unit 206 is an on / off switch for controlling whether power is supplied to the system that drives the electrostatic transducer. In the example shown in FIG. 6, when the power switch unit 206 is turned from on to off, the power supply is stopped after the DC bias control sequence described later is completed.

  The control unit 207 controls switching of the wiring patterns A and B prepared by the switch unit 205 according to the state of the power switch unit 206, and adjusts the output voltage of the DC bias supply unit 203 in the bias voltage adjustment unit 204. It is a control part for controlling.

FIG. 7 shows a control sequence of the control unit 207 in the second embodiment of the present invention.
Here, as a typical method for driving a pull-type electrostatic speaker, a DC bias is applied to the vibration membrane, and a signal voltage is applied to the fixed electrode to apply an electrostatic force (attraction) to vibrate the vibration membrane. Method (hereinafter referred to as method 1), and a method in which a DC bias is applied to the fixed electrode and a signal voltage is applied to the vibrating membrane to apply an electrostatic force (attraction) to vibrate the vibrating membrane (hereinafter referred to as a method). 2).

  In the second embodiment of the present invention, the electrostatic transducer is driven by the method 1 described above.

  As shown in FIG. 7, when the power switch unit 206 is turned on (power switch ON), the control unit 207 outputs high (“1”) to the switch unit 205 as a 1-bit digital signal. Based on the signal, the switch unit 205 switches to the pattern A wiring. Further, the DC bias positive output terminal is wired to the diaphragm, and the DC bias negative output is wired to the system ground.

Here, the DC biases V ₁ and V ₂ applied to the vibration film are defined under the same conditions as in the first embodiment. That is, it is considered that the DC bias applied to the vibrating membrane is increased from 0 when the amplitude value of the signal voltage applied to the fixed electrode is constant. At this time, the output sound pressure level of the electrostatic transducer increases, but saturates at a certain sound pressure level. The voltage value of the DC bias at this time is V _1. As described above, the output level of the electrostatic transducer is maximized when the DC bias is set to V ₁ volt. By applying a voltage of V ₁ volt, the dielectric of the diaphragm is shown in FIG. The remanent polarization occurs in the relationship shown in FIG. Due to this remanent polarization, when the electrostatic transducer drive system is once shut down and then turned on again, the output level obtained will be small even if a DC bias of the same magnitude as the previous drive is applied. There is a problem that it ends up.

Therefore, a voltage (determined by the type of dielectric) necessary to cancel the residual polarization of the dielectric of the electrode film generated when V ₁ volt is applied is defined as V ₂ .

As described above, the control unit 207 outputs an analog or digital signal voltage to the bias voltage adjustment unit so that the positive DC bias is increased from 0 to V ₁ volt after the switch unit 205 sets the wiring pattern to A. To do.

In addition, as shown in FIG. 7, when the power switch unit is switched from on to off (power switch off), the control unit 207 controls the bias voltage adjustment unit so as to lower the DC bias from V ₁ to 0 volts. To do.

Thereafter, low ('0') is output to the switch unit 205 as a 1-bit digital signal, and the wiring pattern is switched to B. Further, the negative output terminal of the DC bias is wired to the diaphragm, and the positive output of the DC bias is wired to the system ground. Thereafter, the control unit 207 outputs an analog or digital signal voltage to the bias voltage adjusting unit 204 so that the DC bias is changed from 0 to negative V ₂ volts. Further, by returning the output of the DC bias to 0, the residual polarization of the dielectric material of the vibration film is canceled and returns to 0 or a state close thereto. The control unit 207 finally controls the switch unit 205 to return the wiring pattern to A, and completely turns off the system power.

  Thus, by using the electrostatic transducer control device of the present invention, it is possible to stably obtain the maximum output value by applying the same DC bias every time the electrostatic transducer is driven. Become.

  Although the example of the control sequence of the DC bias is shown in FIG. 7, the pattern shown in FIG. 8 can be considered based on the same concept.

  The control sequence shown in FIG. 8 is the same as the control sequence shown in FIG. 7 except that the polarity of the DC bias voltage applied to the vibrating membrane is reversed, and the control operation and effect are the same. Therefore, the description is omitted.

[Third Embodiment]
FIG. 9 is a diagram showing the configuration of the electrostatic transducer control device according to the third embodiment of the present invention, and is a configuration example of the DC bias control device in the pull-type electrostatic transducer described above. .

  The DC bias control device shown in FIG. 9 includes a signal wave generating unit 301 that generates a signal wave and a signal wave amplitude adjusting unit 302 that adjusts the amplitude of the signal wave. In addition, a DC bias (+) supply unit A303 that supplies a positive DC bias and a bias voltage adjustment unit A304 that adjusts an output voltage of the DC bias (+) supply unit A303 are included. In addition, a DC bias (−) supply unit B305 that supplies a negative DC bias and a bias voltage adjustment unit B306 that adjusts the output voltage of the DC bias (−) supply unit B305 are provided. In addition, it has a switch unit 307 for selecting one of the output terminals of the DC bias supply unit A or B, and a power switch unit 308 for switching on / off the power supply of the apparatus.

  In addition, the switch unit 307 includes a control unit 309 that selects one of the output terminals of the DC bias supply unit A or B in accordance with the state of the power switch unit 308. The control unit 309 has a function of controlling adjustment of output voltages of the DC bias supply units A and B in the bias voltage adjustment units A and B. The electrostatic transducer 11 is the pull-type electrostatic transducer 11 shown in FIG.

  The first DC bias supply unit described above corresponds to the DC bias (+) supply unit 303, and the second DC bias supply unit corresponds to the DC bias (−) supply unit 305. The first bias voltage adjusting unit corresponds to the bias voltage adjusting unit 304, and the second bias voltage adjusting unit corresponds to the bias voltage adjusting unit 306.

  In the DC bias control device shown in FIG. 9, a signal voltage is generated from the signal wave generation unit 301, and the amplitude is adjusted by the signal wave amplitude adjustment unit 302. Next, the DC bias supply units A303 and B305 are power supplies that supply positive and negative DC biases, respectively. The bias voltage adjustment units A304 and B306 are units for adjusting the output voltages of the DC bias supply units A303 and B305, respectively.

  In the third embodiment, the bias voltage adjustment units A304 and B306 are configured to be able to adjust the output voltages of the DC bias supply units A303 and B305, respectively, based on a control signal from the control unit 309 described later. .

  The switch unit 307 is a part that switches the wiring pattern so that one of the output terminals of the DC bias (+) supply unit A303 or the DC bias (−) supply unit B305 can be selected. In the example illustrated in FIG. 9, the case where the output terminal of the positive DC bias (+) supply unit A303 is selected is the wiring pattern A, and the case where the output terminal of the negative DC bias (−) supply unit B305 is selected is the wiring pattern. B. In addition, since a large voltage is applied to the switch unit 307, for example, a high breakdown voltage relay switch can be used (of course, a high breakdown voltage power semiconductor element can also be used).

  The power switch unit 308 is an on / off switch for controlling whether power is supplied to the system that drives the electrostatic transducer. In the third embodiment of the present invention, particularly when the power switch unit 308 is turned from on to off, the power supply is stopped after the DC bias control sequence described later is completed.

  The control unit 309 controls the switching of the wiring pattern A and the wiring pattern B prepared by the switch unit 307 according to the state of the power switch unit 308. Further, the control unit controls the adjustment of the output voltage of the DC bias (+) supply unit A303 in the bias voltage adjustment unit A304 and the adjustment of the output voltage of the DC bias (−) supply unit B305 in the bias voltage adjustment unit B306. .

FIG. 10 shows a control sequence of the control unit 309 in the third embodiment.
As described in the first embodiment, there are a plurality of methods for driving the pull-type electrostatic speaker. In the third embodiment of the present invention, an electrostatic transducer is applied by a method of applying an electrostatic force (attraction) by applying a DC bias to the vibrating membrane and applying a signal voltage to the fixed electrode, and vibrating the vibrating membrane. It shall be driven.

  As shown in FIG. 10, when the power switch unit 308 is turned on (power switch ON), the control unit 309 outputs high (“1”) as a 1-bit digital signal to the switch unit 307. Based on this signal, the switch unit 307 switches to the pattern A wiring. For example, as the wiring pattern A, the output signal from the DC bias (+) supply unit A303 is wired to the vibration film 31, and the ground from the DC bias (+) supply unit A303 is wired to the system ground. Further, the output signal of the signal wave amplitude adjustment unit 302 is wired to the fixed electrode 21.

Here, the DC biases V ₁ and V ₂ applied to the vibration film are defined under the same conditions as in the first embodiment.
The control unit 309 sets the wiring pattern to A in the switch unit 307 as described above, and then applies an analog or digital signal voltage to the bias voltage adjustment unit 304 so as to increase the positive DC bias from 0 to V ₁ volt. Output.

As shown in FIG. 10, when the power switch unit is turned from on to off (power switch OFF), the control unit 309 controls the bias voltage adjustment unit 304 to lower the DC bias from V ₁ to 0 volts. Control. Thereafter, low ('0') is output to the switch unit 307 as a 1-bit digital signal, and the wiring pattern is switched to B. With this wiring pattern B, the output signal from the DC bias (−) supply unit B305 is wired to the vibration film 31, and the ground from the DC bias (−) supply unit B305 is wired to the system ground.

Thereafter, the control unit 309 outputs an analog or digital signal voltage to the bias voltage adjustment unit 306 so that the DC bias is changed from 0 to negative V ₂ volts. Further, by returning the output of the DC bias (−) supply unit B305 to 0, the residual polarization of the dielectric of the vibration film 31 is canceled and returns to a state of 0 or a value close thereto. Finally, the control unit 309 controls the switch unit 307 to return the wiring pattern to A, and completely turns off the system power.

  By using such a DC bias control method and control device, it is possible to stably obtain the maximum output value by applying the same DC bias each time the electrostatic transducer is driven.

  In the third embodiment, the DC bias control sequence shown in FIG. 10 is used. However, the control sequence pattern shown in FIG. 11 can be used in the same manner.

  The control sequence shown in FIG. 11 is the same as the control sequence shown in FIG. 10 except that the polarity of the DC bias voltage applied to the vibrating membrane 31 is reversed, and the control operation and effect are the same. Therefore, the description is omitted.

[Fourth Embodiment]
FIG. 12 is a diagram showing the configuration of the electrostatic transducer control device according to the fourth embodiment of the present invention, and is a configuration example of the DC bias control device in the push-pull electrostatic transducer described above. is there.

  The DC bias control device shown in FIG. 12 has a signal wave generator 401 that generates a signal wave and a phase inversion that generates a signal whose phase is inverted with respect to the signal wave based on the output signal of the signal wave generator 401. Part 402.

  In addition, it has a signal wave amplitude adjusting unit 403 that simultaneously adjusts the amplitude of the output of the signal wave generating unit 401 and the output signal of the phase inverting unit. The signal wave amplitude adjustment unit 403 is configured to be capable of simultaneously amplifying or attenuating two input signals. Here, an output obtained by adjusting the amplitude of the signal from the signal wave generator 401 is referred to as a signal wave output A, and an output obtained by adjusting the amplitude of the signal from the phase inverter 402 is referred to as a signal wave output B.

  In addition, the electrostatic transducer control device includes a DC bias supply unit 404 that supplies a positive or negative DC bias of one polarity, and a bias voltage adjustment unit 405 that adjusts the output voltage of the DC bias supply unit 404. Have.

  A switch unit 406 is also provided. The switch unit 406 has a function of switching between the wiring pattern A1, the wiring pattern A2, the wiring pattern B, and the wiring pattern C.

  The wiring pattern A1 connects the signal wave output A and the fixed electrode A, connects the signal wave output B and the fixed electric plate B, and connects the output of the DC bias supply unit 404 and the vibration film 31 of the electrostatic transducer. This is a wiring pattern.

  The wiring pattern A2 connects the signal wave output A and the fixed electrode B, connects the signal wave output B and the fixed electrode A, and connects the output of the DC bias supply unit 404 and the vibration film 31 of the electrostatic transducer. It is a wiring pattern.

  The wiring pattern B connects the signal wave output A and the vibrating membrane 31 of the electrostatic transducer, connects the signal wave output B and the fixed plate B, and connects the output of the DC bias supply unit 404 and the fixed electrode A. This is a wiring pattern.

  The wiring pattern C connects the signal wave output A and the fixed electrode A, connects the signal wave output B and the vibration film 31 of the electrostatic transducer, and connects the output of the DC bias supply unit 404 and the fixed electrode B. It is a wiring pattern.

  Further, the control device shown in FIG. 12 includes a power switch unit 407 that switches on and off of the power. The control unit 408 controls the switching of the wiring patterns A1, A2, B, and C in the switch unit and the adjustment of the output voltage of the DC bias supply unit 404 in the bias voltage adjustment unit 405. The push-pull type electrostatic transducer 12 shown in FIG. 2 is provided.

  The first fixed electrode described above corresponds to the fixed electrode A21A, and the second fixed electrode corresponds to the fixed electrode B21B.

  In the DC bias control apparatus shown in FIG. 12, the output generated from the signal wave generator 401 is branched in two directions, one is input to the signal wave amplitude adjuster 403, and the other is input to the phase inverter 402. .

  The signal wave whose amplitude is adjusted by the signal wave amplitude adjusting unit 403 and its phase-inverted signal wave are respectively input to the two fixed electrodes of the push-pull type electrostatic transducer.

  Next, the DC bias supply unit 404 is a power supply that supplies either positive or negative DC bias. In the example shown in FIG. 12, it is assumed that a positive DC bias can be supplied. The bias voltage adjustment unit 405 is an adjustment unit for adjusting the output voltage of the DC bias supply unit 404. In the example shown in FIG. 12, the bias voltage adjustment unit 405 is configured to be able to adjust the output voltage of the DC bias supply unit 404 based on a signal from the control unit 408 described later.

  The switch unit 406 includes two outputs from the signal wave amplitude adjustment unit 403 (signal voltages whose phases are inverted from each other), an output from the DC bias supply unit 404, two fixed electrodes of the electrostatic transducer, and a vibrating membrane. This is a part for switching the wiring pattern.

  In the fourth embodiment of the present invention, three wiring patterns A1, B, and C described above or three wiring patterns A2, B, and C can be selected as wiring patterns to be switched by the switch unit 406. Constitute.

  In the example illustrated in FIG. 12, it is assumed that three wiring patterns A1, B, and C can be selected by the switch unit 406. In addition, since a large voltage is applied to the switch unit 406, for example, a high breakdown voltage relay switch can be used (of course, a high breakdown voltage power semiconductor element can also be used).

  The power switch unit 407 is an on / off switch for controlling whether power is supplied to the system that drives the electrostatic transducer. In the example shown in FIG. 12, particularly when the power switch unit 407 is turned from on to off, the power supply is stopped after the DC bias control sequence described later is completed.

  The control unit 408 controls switching of the wiring patterns A1, B, and C prepared by the switch unit 406 according to the state of the power switch unit 407, and the output voltage of the DC bias supply unit 404 in the bias voltage adjustment unit 405. It is a control part for controlling adjustment of.

FIG. 13 shows an example of a control sequence of the control unit 408 in the fourth embodiment.
As shown in FIG. 13, when the power switch unit 407 is turned on (power switch ON), the control unit 408 outputs ('01') as a 2-bit digital signal to the switch unit 406, and the signal Based on this, the switch unit 406 switches to the wiring of the wiring pattern A1. In the wiring pattern A1, a DC bias is applied to the vibration film 31.

Here, the DC biases V ₁ and V ₂ applied to the vibration film 31 are defined under the same conditions as in the first embodiment. After the control unit 408 has a wiring pattern and A1 switch unit 406 as described above, a positive DC bias to rise from 0 to V ₁ volt, an analog or digital signal voltage to the bias voltage adjusting unit 405 Output.

As shown in FIG. 13, when the power switch unit 407 is turned from on to off (power switch OFF), the control unit 408 controls the bias voltage adjustment unit 405 so as to lower the DC bias from V ₁ to 0 volts. To control.

Thereafter, ('10') is output to the switch unit 406 as a 1-bit digital signal, and the wiring pattern is switched to B. Thereafter, the control unit 408 outputs an analog or digital signal voltage to the bias voltage adjustment unit 405 so that the DC bias is changed from 0 to a positive V ₂ volts. In the wiring pattern B, a DC bias is applied to the fixed electrode A.

Here, since both the DC biases V ₁ and V ₂ are supplied from the DC bias supply unit 404, both have positive polarity in the fourth embodiment. However, since the switching of the wiring pattern from A1 to B, V ₁ and V ₂ will be applying an electric field in the opposite directions with respect to the dielectric film on the side that is between the fixed electrode A and the vibrating film 31 . Therefore, after the above operation is performed, the residual polarization of the dielectric film on the side between the vibration film 31 and the fixed electrode A is canceled by returning the output of the DC bias to 0, and it becomes 0 or a state close thereto. Return.

Next, (11) is output to the switch unit 406 as a 1-bit digital signal, and the wiring pattern is switched to C. Thereafter, the control unit 408 outputs an analog or digital signal voltage to the bias voltage adjustment unit 405 so that the DC bias is changed from 0 to a positive V ₂ volts. In the wiring pattern C, a DC bias is applied to the fixed electrode B.

  After performing the above operation, by returning the output of the DC bias to 0, the remanent polarization of the dielectric on the side between the vibrating membrane and the fixed electrode B is canceled, and returns to 0 or a state close thereto. The control unit 408 finally controls the switch unit 406 so as to return the wiring pattern to A1, and completely turns off the power supply of the system.

  By using such a DC bias control method and control device, it is possible to stably obtain the maximum output value by applying the same DC bias each time the push-pull type electrostatic transducer is driven. It becomes.

  Moreover, although the thing of FIG. 13 was shown as an example of the control sequence of DC bias in 4th Embodiment, the pattern of FIG. 14 can also be considered with the same view. The control sequence shown in FIG. 14 is an example in which the wiring pattern A2 when driving the electrostatic transducer is used, the wiring pattern B is first selected at the end of driving the electrostatic transducer, and then the wiring pattern C is selected. is there.

[Fifth Embodiment]
FIG. 15 is a diagram showing the configuration of the electrostatic transducer control apparatus according to the fifth embodiment of the present invention, and is a configuration example of the DC bias control apparatus in the push-pull electrostatic transducer described above. is there.

  The electrostatic transducer control device shown in FIG. 15 generates a signal wave generating unit 501 that generates a signal wave and a signal whose phase is inverted with respect to the signal wave based on the output signal of the signal wave generating unit 501. And a phase inversion unit 502.

  In addition, a signal wave amplitude adjusting unit 503 that simultaneously adjusts the amplitude of the output of the signal wave generating unit 501 and the output signal of the phase inverting unit is provided. Also, it has three output terminals of positive, negative, and ground, and a DC bias supply unit 504 that arbitrarily selects and supplies positive or negative DC bias according to the connection method of the three output terminals. In addition, a bias voltage adjustment unit 505 that adjusts the output voltage of the DC bias is provided.

  The DC bias supply unit 504 includes a switch unit 506 that switches the wiring of the three output terminals to a wiring pattern A that short-circuits negative and ground and a wiring pattern B that short-circuits positive and ground. In addition, a power switch unit 506 for switching on and off the power supply of the DC bias control device is provided.

  The control unit controls the switch unit 506 to switch the wiring patterns A and B according to the state of the power switch unit 507 and controls the adjustment of the output voltage of the DC bias supply unit 504 in the bias voltage adjustment unit 505. have. The push-pull type electrostatic transducer 12 shown in FIG.

  In the fifth embodiment, the DC bias control method shown in the second embodiment is applied to a push-pull electrostatic transducer. Here, only differences from the second embodiment will be described.

  As described above, in order to drive the push-pull type electrostatic transducer, it is necessary to apply signal voltages having inverted phases to the two fixed electrodes. Therefore, the output generated from the signal wave generation unit 501 is branched in two directions, one is input to the signal wave amplitude adjustment unit 503, and the other is input to the phase inversion unit 502.

  Here, it is assumed that the signal wave amplitude adjusting unit 503 can simultaneously amplify or attenuate two input signals. The signal wave whose amplitude is adjusted by the signal wave amplitude adjusting unit 503 and its phase-inverted signal wave are respectively input to the two fixed electrodes of the push-pull type electrostatic transducer.

  Note that the DC bias control method can be handled by the same procedure as that of the pull-type electrostatic transducer shown in the second embodiment, and a description thereof will be omitted.

[Sixth Embodiment]
FIG. 16 is a diagram showing the configuration of the electrostatic transducer control device according to the sixth embodiment of the present invention, and is a configuration example of the DC bias control device in the push-pull electrostatic transducer described above. is there.

  The electrostatic transducer control device shown in FIG. 16 generates a signal wave generation unit 601 that generates a signal wave and a signal whose phase is inverted with respect to the signal wave based on the output signal of the signal wave generation unit 601. And a phase inversion unit 602.

  In addition, a signal wave amplitude adjusting unit 603 that simultaneously adjusts the amplitude of the output of the signal wave generating unit 601 and the output signal of the phase inverting unit 602 is provided. Also, a DC bias (+) supply unit A604 that supplies a positive DC bias and a bias voltage adjustment unit A605 that adjusts the output voltage of the DC bias (+) supply unit A604 are provided.

  Further, a DC bias (−) supply unit B 606 for supplying a negative DC bias and a bias voltage adjustment unit B 607 for adjusting an output voltage of the DC bias (−) supply unit B are provided. In addition, it has a switch unit 608 that selects one of the output terminals of the DC bias supply unit A or B, and a power switch unit 609 that switches on / off the power supply of the apparatus.

  In addition, the control unit 610 controls the switch unit 608 to select one of the output terminals of the DC bias supply unit A or B according to the state of the power switch unit. The control unit 610 also has a function of controlling adjustment of output voltages of the DC bias (+) supply unit A and the DC bias (−) supply unit B in the bias voltage adjustment unit A605 and the bias voltage adjustment unit B607.

  The electrostatic transducer 12 is the push-pull electrostatic transducer 12 shown in FIG.

  The first DC bias supply unit described above corresponds to the DC bias (+) supply unit A604, and the second DC bias supply unit corresponds to the DC bias (−) supply unit B606. Further, the first bias voltage adjusting unit corresponds to the bias voltage adjusting unit A605, and the second bias voltage adjusting unit corresponds to the bias voltage adjusting unit B607.

  In the sixth embodiment, the DC bias control method shown in the third embodiment is applied to a push-pull electrostatic transducer. Here, only differences from the third embodiment will be described.

  The output generated from the signal wave generation unit 601 is branched in two directions, one is input to the signal wave amplitude adjustment unit 603, and the other is input to the phase inversion unit 602. Here, it is assumed that the signal wave amplitude adjustment unit 603 can simultaneously amplify or attenuate two input signals.

  The signal wave whose amplitude is adjusted by the signal wave amplitude adjusting unit 603 and its phase-inverted signal wave are respectively input to the two fixed electrodes A and B of the push-pull type electrostatic transducer. The DC bias control method performed in the sixth embodiment can be handled by the same procedure as that of the pull type electrostatic transducer shown in the third embodiment, and the description thereof is omitted.

[Seventh Embodiment]
As described above, attempts have recently been made to apply electrostatic transducers as ultrasonic speakers. An ultrasonic speaker emits a differential frequency component (self-demodulated sound) with very strong directivity as an audible sound by the parametric array effect when a signal obtained by modulating an ultrasonic wave with an audio signal is emitted by an ultrasonic transducer. Is.

  Therefore, in the first to sixth embodiments described above, by replacing the circuit at the subsequent stage of the signal wave generator as shown in FIG. Can also be supported.

  FIG. 17 shows a signal wave generation unit 701 that generates a signal wave, a carrier wave supply unit 702 that supplies a carrier wave in the ultrasonic band, and an output signal of the carrier wave supply unit 702 that is an output signal of the signal wave generation unit 701. And a modulation unit 703 for modulation.

  Here, various units such as amplitude modulation and frequency modulation can be considered as the modulation unit 703, but amplitude modulation is mainly used in the ultrasonic speaker system. Therefore, in the seventh embodiment, the modulation unit 703 performs the modulation. The modulation method is amplitude modulation.

  As described above, when the electrostatic transducer is driven at the maximum or close to the output value, there is a problem that a larger DC bias is required to obtain an equivalent output characteristic at the next and subsequent driving. It was.

  On the other hand, by using the electrostatic transducer control device of the present invention, even when the electrostatic transducer is driven at the maximum or close to the output value, the same output under the same driving condition at the time of the next and subsequent driving. It becomes possible to obtain characteristics. In addition, there are many other methods for driving the electrostatic transducer from the viewpoint of the structure and the electric system to be applied. However, in order to solve the common problems specified in this proposal, they are fundamental in the present invention. It is clear that it can be handled within the scope not departing from the principle and concept.

  Although the embodiments of the present invention have been described above, the electrostatic transducer control device and the ultrasonic speaker according to the present invention are not limited to the illustrated examples described above, and do not depart from the gist of the present invention. Of course, various changes can be made.

The block diagram of the pull-type electrostatic transducer used as the control object of this invention. The block diagram of the push-pull type electrostatic transducer used as the control object of this invention. The figure which shows 1st Embodiment of the control apparatus of the electrostatic transducer of this invention. The figure which shows the control sequence in 1st Embodiment. The figure which shows the other control sequence in 1st Embodiment. The figure which shows 2nd Embodiment of the control apparatus of the electrostatic transducer of this invention. The figure which shows the control sequence in 2nd Embodiment. The figure which shows the other control sequence in 2nd Embodiment. The figure which shows 3rd Embodiment of the control apparatus of the electrostatic transducer of this invention. The figure which shows the control sequence in 3rd Embodiment. The figure which shows the other control sequence in 3rd Embodiment. The figure which shows 4th Embodiment of the control apparatus of the electrostatic transducer of this invention. The figure which shows the control sequence in 4th Embodiment. The figure which shows the other control sequence in 4th Embodiment. The figure which shows 5th Embodiment of the control apparatus of the electrostatic transducer of this invention. The figure which shows 6th Embodiment of the control apparatus of the electrostatic transducer of this invention. The block diagram of the ultrasonic speaker concerning the 7th Embodiment of this invention. The figure for demonstrating the residual polarization of a dielectric material film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Pull type electrostatic transducer, 12 ... Push-pull type electrostatic transducer, 21 ... Fixed electrode, 21A ... Fixed electrode A, 21B ... Fixed electrode B, 22, 22A, 22B ... through hole, 23 ... support member, 31 ... vibrating film, 31A ... electrode film, 31B ... dielectric film, 32 ... DC bias power supply, 33, 33A, 33B: AC signal source, 101, 201, 301, 401, 501, 601 ... Signal wave generator, 102, 202, 302, 403, 503, 603 ... Signal wave amplitude adjuster, 103, 203 , 303, 305, 404, 504, 604, 606... DC bias supply unit, 104, 204, 304, 306, 405, 505, 605, 607... Bias voltage adjustment unit, 105, 205 307, 406, 506, 608 ... switch unit, 106, 206, 308, 407, 507, 609 ... power switch unit, 107, 207, 309, 408, 508, 610 ... control unit, 402, 502, 602 ... Phase inversion unit, 701 ... Signal wave generation unit, 702 ... Carrier wave supply unit, 703 ... Modulation unit

Claims (20)

A vibration film having an electrode film formed on a dielectric film; and a fixed electrode disposed on a surface of the vibration film on the surface of the dielectric film, and applying a voltage between the fixed electrode and the vibration film. A control device for an electrostatic transducer configured to generate an electrostatic force between the fixed electrode and the vibrating membrane,
Means for applying a DC bias voltage in which a signal wave is superimposed between the vibrating membrane and the fixed electrode when the electrostatic transducer is driven;
In order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage at the end of driving of the electrostatic transducer, the DC bias voltage for canceling the residual polarization is interposed between the vibrating film and the fixed electrode. Means for applying
A control device for an electrostatic transducer, comprising: A signal wave generator for generating a signal wave;
A signal wave amplitude adjusting unit for adjusting the amplitude of the signal wave;
A DC bias supply unit for supplying a positive or negative DC bias of one polarity;
A bias voltage compensation unit for adjusting an output voltage of the DC bias supply unit;
A wiring pattern A for connecting the output of the signal wave amplitude adjusting unit and the fixed electrode of the electrostatic transducer, and connecting the output of the DC bias supply unit and the vibration film of the electrostatic transducer; and the signal wave amplitude A switch unit that switches between the output of the adjustment unit and the vibration film of the electrostatic transducer, and the wiring pattern B that connects the output of the DC bias supply unit and the fixed electrode of the electrostatic transducer;
A power switch for switching the power on and off of the device;
A control unit that switches the wiring pattern A and the wiring pattern B in the switch unit, and a control unit that controls adjustment of an output voltage of the DC bias supply unit in the bias voltage adjustment unit;
The electrostatic transducer control device according to claim 1, further comprising: Select the wiring pattern A when driving the electrostatic transducer,
Select the wiring pattern B at the end of driving of the electrostatic transducer to erase the residual polarization,
Alternatively, the wiring pattern B is selected when the electrostatic transducer is driven,
The wiring pattern A is selected at the end of driving of the electrostatic transducer to erase the residual polarization,
The electrostatic transducer control device according to claim 2. A signal wave generator for generating a signal wave;
A signal wave amplitude adjusting unit for adjusting the amplitude of the signal wave;
A DC bias supply unit having three output terminals of positive, negative, and ground, and arbitrarily selecting and supplying a positive or negative DC bias according to a method of connecting the three output terminals;
A bias voltage adjusting unit for adjusting the output voltage of the DC bias;
A switch unit for switching the wiring of the three output terminals of the DC bias supply unit to a wiring pattern a that short-circuits negative and ground, and a wiring pattern b that short-circuits positive and ground;
A power switch for switching the power on and off of the device;
According to the state of the power switch unit, the wiring unit a is selected in the switch unit, the positive output of the DC bias supply unit and the vibration film are connected, and the output of the signal wave amplitude adjustment unit The wiring pattern A that connects the fixed electrode, the wiring pattern b is selected in the switch unit, the negative output of the DC bias supply unit and the vibration film are connected, and the output of the signal wave amplitude adjustment unit And a control unit that controls the adjustment of the output voltage of the DC bias supply unit in the bias voltage adjustment unit,
The electrostatic transducer control device according to claim 1, further comprising: Select the wiring pattern A when driving the electrostatic transducer,
Select the wiring pattern B at the end of driving of the electrostatic transducer to erase the residual polarization,
Alternatively, the wiring pattern B is selected when the electrostatic transducer is driven,
The wiring pattern A is selected at the end of driving of the electrostatic transducer to erase the residual polarization,
The electrostatic transducer control device according to claim 4, wherein: A signal wave generator for generating a signal wave;
A signal wave amplitude adjusting unit for adjusting the amplitude of the signal wave;
A first DC bias supply for supplying a positive DC bias;
A first bias voltage adjustment unit for adjusting an output voltage of the first DC bias supply unit;
A second DC bias supply for supplying a negative DC bias;
A second bias voltage adjustment unit for adjusting an output voltage of the second DC bias supply unit;
A switch unit for selecting an output terminal of either the first DC bias supply unit or the second DC bias supply unit;
A power switch for switching the power on and off of the device;
According to the state of the power switch unit, the switch unit selects an output terminal of the first DC bias supply unit and connects the output of the selected first DC bias supply unit to a vibrating membrane; and The wiring pattern A for connecting the output of the signal wave amplitude adjustment unit to the fixed electrode, and the output terminal of the second DC bias supply unit selected in the switch unit and the output of the selected second DC bias supply unit In the first bias voltage adjusting unit and the second bias voltage adjusting unit, and a control for selecting the wiring pattern B for connecting the output of the signal wave amplitude adjusting unit to the fixed electrode. A control unit that controls adjustment of output voltages of the first DC bias supply unit and the second DC bias supply unit;
The electrostatic transducer control device according to claim 1, further comprising: Select the wiring pattern A when driving the electrostatic transducer,
Select the wiring pattern B at the end of driving of the electrostatic transducer to erase the residual polarization,
Alternatively, the wiring pattern B is selected when the electrostatic transducer is driven,
The wiring pattern A is selected at the end of driving of the electrostatic transducer to erase the residual polarization,
The control device for an electrostatic transducer according to claim 6. The signal wave generated by the signal wave generator is a modulated wave obtained by modulating a carrier wave in an ultrasonic frequency band with a signal wave in an audible frequency band,
The electrostatic transducer is an electrostatic ultrasonic transducer that emits ultrasonic waves;
8. The electrostatic transducer control device according to claim 1, wherein the control device is an electrostatic transducer. A vibration film configured by sandwiching an electrode film between a first dielectric film and a second dielectric film; a first fixed electrode disposed on a surface side of the first dielectric film; A second fixed electrode disposed on the surface side of the second dielectric film, and applying a voltage between the first fixed electrode, the second fixed electrode, and the vibration film, A control device for an electrostatic transducer configured to generate an electrostatic force between the fixed electrode and the vibrating membrane, and between the second fixed electrode and the vibrating membrane,
When driving the electrostatic transducer, a first signal wave is applied between the vibrating membrane and the first fixed electrode so as to be superimposed on a DC bias voltage, and the vibrating membrane and the second fixed electrode are applied. Means for applying a second signal wave having a phase reversed from that of the first signal wave superimposed on a DC bias voltage between the electrodes;
At the end of driving of the electrostatic transducer, in order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage, between the vibrating film and the first fixed electrode, and between the vibrating film and the Means for applying a DC bias voltage for erasing residual polarization of the dielectric film between the second fixed electrode;
A control device for an electrostatic transducer, comprising: A signal wave generator for generating a signal wave;
Based on the output signal of the signal wave generator, a phase inverter that generates a signal whose phase is inverted with respect to the signal wave;
A signal wave amplitude adjusting unit that simultaneously adjusts an amplitude of an output signal of the signal wave generating unit and an output signal of the phase inverting unit, and outputs each signal as a signal wave output A and a signal wave output B;
A DC bias supply unit that supplies a positive or negative DC bias of one polarity; a bias voltage adjustment unit that adjusts an output voltage of the DC bias supply unit;
The signal wave output A and the first fixed electrode are connected, the signal wave output B and the second fixed electrode are connected, and the output of the DC bias supply unit and the vibration film of the electrostatic transducer A wiring pattern A1 that connects the signal wave output A and the second fixed electrode, a signal wave output B and the first fixed electrode, and an output of the DC bias supply unit. The wiring pattern A2 for connecting the vibration film of the electrostatic transducer, the signal wave output A and the vibration film of the electrostatic transducer are connected, and the signal wave output B and the second fixed electrode are connected. And the wiring pattern B connecting the output of the DC bias supply unit and the first fixed electrode, the signal wave output A and the first fixed electrode, and the signal wave output B and the electrostatic Type transformer A switch unit for connecting the vibrating membrane Yusa, and switching between the wiring pattern C which connects the second fixed electrode and the output of the DC bias supply unit,
A power switch for switching the power on and off of the device;
A control unit that switches the wiring patterns A1, A2, B, and C in the switch unit, and a control unit that controls adjustment of an output voltage of the DC bias supply unit in the bias voltage adjustment unit;
10. The electrostatic transducer control device according to claim 9, further comprising: The wiring pattern A1 is selected when the electrostatic transducer is driven,
Selecting the wiring pattern B and the wiring pattern C at the end of driving the electrostatic transducer to erase the residual polarization,
Alternatively, the wiring pattern A2 is selected when the electrostatic transducer is driven,
The wiring pattern B and the wiring pattern C are selected at the end of driving of the electrostatic transducer, and the residual polarization is erased.
The control device for an electrostatic transducer according to claim 10. A signal wave generator for generating a signal wave;
Based on the output signal of the signal wave generator, a phase inverter that generates a signal whose phase is inverted with respect to the signal wave;
A signal wave amplitude adjusting unit that simultaneously adjusts an amplitude of an output signal of the signal wave generating unit and an output signal of the phase inverting unit, and outputs each signal as a signal wave output A and a signal wave output B;
A DC bias supply unit having three output terminals of positive, negative, and ground, and arbitrarily selecting and supplying a positive or negative DC bias according to a method of connecting the three output terminals;
A bias voltage adjusting unit for adjusting the output voltage of the DC bias;
A switch unit for switching the wiring of the three output terminals of the DC bias supply unit to a wiring pattern a that short-circuits negative and ground, and a wiring pattern b that short-circuits positive and ground;
A power switch for switching the power on and off of the device;
According to the state of the power switch unit, the switch unit selects the wiring pattern a and connects the positive output of the DC bias supply unit and the vibration film, and the signal wave output A and the first The wiring pattern A for connecting the fixed wave and the signal wave output B and the second fixed electrode, the wiring pattern b is selected in the switch section, the negative output of the DC bias supply section and the vibration Control for connecting the film and connecting the signal wave output A and the first fixed electrode and switching between the signal wave output B and the wiring pattern B connecting the second fixed electrode, and adjusting the bias voltage A control unit for controlling adjustment of an output voltage of the DC bias supply unit in the unit;
10. The electrostatic transducer control device according to claim 9, further comprising: Select the wiring pattern A when driving the electrostatic transducer,
Select the wiring pattern B at the end of driving of the electrostatic transducer to erase the residual polarization,
Alternatively, the wiring pattern B is selected when the electrostatic transducer is driven,
The wiring pattern A is selected at the end of driving of the electrostatic transducer to erase the residual polarization,
The electrostatic transducer control device according to claim 12, wherein: A signal wave generator for generating a signal wave;
Based on the output signal of the signal wave generator, a phase inverter that generates a signal whose phase is inverted with respect to the signal wave;
A signal wave amplitude adjusting unit that simultaneously adjusts an amplitude of an output signal of the signal wave generating unit and an output signal of the phase inverting unit, and outputs each signal as a signal wave output A and a signal wave output B;
A first DC bias supply for supplying a positive DC bias;
A first bias voltage adjustment unit for adjusting an output voltage of the first DC bias supply unit;
A second DC bias supply for supplying a negative DC bias;
A second bias voltage adjustment unit for adjusting an output voltage of the second DC bias supply unit;
A switch unit for selecting an output terminal of either the first DC bias supply unit or the second DC bias supply unit;
A power switch for switching the power on and off of the device;
According to the state of the power switch unit, the switch unit selects an output terminal of the first DC bias supply unit and connects the output of the selected first DC bias supply unit to a vibrating membrane; and A wiring pattern A connecting the signal wave output A to the first fixed electrode and connecting the signal wave output B and the second fixed electrode, and an output terminal of the second DC bias supply unit in the switch unit And the output of the selected second DC bias supply unit is connected to the diaphragm, the signal wave output A is connected to the first fixed electrode, and the signal wave output B is connected to the second Control for selecting the wiring pattern B connected to the fixed electrode, and the first DC bias supply unit and the second DC via in the first bias voltage adjustment unit and the second bias voltage adjustment unit A control unit for controlling the adjustment of the output voltage of the supply unit,
10. The electrostatic transducer control device according to claim 9, further comprising: Select the wiring pattern A when driving the electrostatic transducer,
Select the wiring pattern B at the end of driving of the electrostatic transducer to erase the residual polarization,
Alternatively, the wiring pattern B is selected when the electrostatic transducer is driven,
The wiring pattern A is selected at the end of driving of the electrostatic transducer to erase the residual polarization,
15. The control device for an electrostatic transducer according to claim 14, wherein: The signal wave generated by the signal wave generator is a modulated wave obtained by modulating a carrier wave in an ultrasonic frequency band with a signal wave in an audible frequency band,
The electrostatic transducer is an electrostatic ultrasonic transducer that emits ultrasonic waves;
The electrostatic transducer control device according to any one of claims 9 to 15, wherein A vibration film having an electrode film formed on a dielectric film; and a fixed electrode disposed on a surface of the vibration film on the surface of the dielectric film, and applying a voltage between the fixed electrode and the vibration film. An electrostatic transducer control method configured to generate an electrostatic force between the fixed electrode and the vibrating membrane,
Applying a DC bias voltage in which a signal wave is superimposed between the vibrating membrane and the fixed electrode when driving the electrostatic transducer;
In order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage at the end of driving of the electrostatic transducer, the DC bias voltage for canceling the residual polarization is interposed between the vibrating film and the fixed electrode. And a procedure for applying
A method for controlling an electrostatic transducer, comprising: A vibration film configured by sandwiching an electrode film between a first dielectric film and a second dielectric film, a first fixed electrode disposed on a surface side of the first dielectric film, the second A second fixed electrode disposed on the surface side of the dielectric film, and applying a voltage between the first fixed electrode, the second fixed electrode, and the vibration film, A method for controlling an electrostatic transducer configured to generate an electrostatic force between a fixed electrode and the vibrating membrane, and between the second fixed electrode and the vibrating membrane,
When driving the electrostatic transducer, a first signal wave is applied between the vibrating membrane and the first fixed electrode so as to be superimposed on a DC bias voltage, and the vibrating membrane and the second fixed electrode are applied. Applying a second signal wave having a phase reversed from that of the first signal wave superimposed on a DC bias voltage between the electrodes;
At the end of driving of the electrostatic transducer, in order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage, between the vibrating film and the first fixed electrode, and between the vibrating film and the Applying a DC bias voltage for eliminating residual polarization of the dielectric film between the second fixed electrode;
A method for controlling an electrostatic transducer, comprising: A signal wave output from a signal generation source that generates an audible frequency band is used to modulate a carrier wave in the ultrasonic frequency band, and an electrostatic transducer is driven by the modulated wave to reproduce an audible frequency band signal sound. An ultrasonic speaker that
Electrostatic transducers
A vibration film having an electrode film formed on a dielectric film;
A fixed electrode disposed on the surface of the dielectric film of the vibration film;
With
The electrostatic transducer control device includes:
Means for applying a DC bias voltage in which a signal wave is superimposed between the vibrating membrane and the fixed electrode when the electrostatic transducer is driven;
In order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage at the end of driving of the electrostatic transducer, the DC bias voltage for canceling the residual polarization is interposed between the vibrating film and the fixed electrode. Means for applying
An ultrasonic speaker comprising: A carrier wave in the ultrasonic frequency band is modulated by a signal wave output from a signal source that generates a signal wave in the audible frequency band, and an acoustic transducer is driven by the modulated wave to reproduce a signal sound in the audible frequency band. An ultrasonic speaker,
Electrostatic transducers
A vibration film configured by sandwiching an electrode film between a first dielectric film and a second dielectric film;
A first fixed electrode disposed on a surface side of the first dielectric film;
A second fixed electrode disposed on the surface side of the second dielectric film;
With
The electrostatic transducer control device includes:
When driving the electrostatic transducer, a first signal wave is applied between the vibrating membrane and the first fixed electrode so as to be superimposed on a DC bias voltage, and the vibrating membrane and the second fixed electrode are applied. Means for applying a second signal wave having a phase reversed from that of the first signal wave superimposed on a DC bias voltage between the electrodes;
At the end of driving of the electrostatic transducer, in order to cancel the residual polarization of the dielectric film caused by the application of the DC bias voltage, between the vibrating film and the first fixed electrode, and between the vibrating film and the Means for applying a DC bias voltage for erasing residual polarization of the dielectric film between the second fixed electrode;
An ultrasonic speaker comprising:

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