JP2010141858A - Sound generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely maintain plasma of a quantity required for discharge for generating sound pressure, and to carry out discharge with low power. <P>SOLUTION: This sound generator includes a first switch, and a second switch driven by logic opposite to that of the first switch. The sound generator further includes: a transformer with the first switch and the second switch respectively connected to both ends on the primary side for outputting a high-voltage pulse to the secondary side by applying drive voltage to the center of the primary side; and discharge electrodes between which the high-voltage pulse is applied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a sound generator.
More specifically, the present invention relates to a sound generator that reliably maintains an amount of plasma necessary for discharge for generating sound pressure.

  Conventionally, there are speakers of a dynamic type or an electrostatic drive type. These dynamic type or electrostatic drive type speakers drive the mechanical vibration system of the speaker using mechanical resonance or split vibration mode when generating sound waves. For this reason, it is difficult to realize a flat frequency characteristic as well as a peculiar tone tone.

  There is an analog type plasma speaker as one that does not have the unique timbre. An analog plasma speaker does not have a mechanical vibration system. For this reason, sound quality and flat frequency response without defects can be expected. The prior art of the present invention is described in Patent Document 1.

JP-A-2-281898

  By the way, the analog type plasma speaker described in the cited document 1 has a problem that an auxiliary circuit such as a high frequency oscillation circuit is large and its power consumption is large.

  Further, although a method of DC pulse arc discharge modulated by PWM is proposed in the cited reference 1, it is necessary to continuously maintain an arc by high-speed charging / discharging, it is difficult to maintain the certainty of discharge, and the peak value There is a problem that the linearity of the sound pressure with respect to is not guaranteed.

  The present invention has been made in view of such points, and an object of the present invention is to provide a sound generator that reliably maintains an amount of plasma necessary for discharge for generating sound pressure.

  In order to solve the above-described problems, the present invention includes a first switch and a second switch that is driven by an inverse logic of the first switch. Furthermore, a first switch and a second switch are connected to both ends of the primary side, respectively, a transformer for applying a driving voltage to the center of the primary side and outputting a high voltage pulse to the secondary side, and a discharge electrode to which the high voltage pulse is applied And comprising.

  According to the above configuration, by exciting the high-frequency AC discharge by driving the switching element with a digital signal, a stable and reliable discharge can be obtained, and the power consumption can be greatly reduced.

  ADVANTAGE OF THE INVENTION According to this invention, while maintaining reliably the quantity of plasma required for the discharge for producing a sound pressure, the audio | voice generator which performs discharge with low electric power can be provided.

  Hereinafter, the best mode for carrying out the invention (hereinafter referred to as “embodiment”) will be described in the following order. The embodiments described below are preferred specific examples of the present invention. Therefore, various technically preferable limitations are attached. However, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description. For example, the numerical conditions of each parameter given in the following description are only suitable examples, and the dimensions, shapes, and arrangement relationships in the drawings used for the description are also schematic.

1. 1. First embodiment (1) Configuration of sound generation device (2) Configuration of discharge speaker (3) Operation of sound generation device 2. Second embodiment (1) Configuration of sound generator (2) Configuration of discharge speaker 3. Third embodiment (1) Configuration of voice generation device (2) Operation of voice generation device Fourth Embodiment (1) Configuration of Speech Generator (2) Operation of Speech Generator

<1. First Embodiment>
[Configuration of the sound generator 101]
FIG. 1 is a circuit diagram of a sound generator according to a first embodiment of the present invention.
The sound generator 101 includes a PWM (Pulse Width Modulation) modulation circuit 102, a switching circuit 103, a transformer 104, and a discharge body 105.

  The PWM modulation circuit 102 is a circuit that PWM modulates an input audio signal. This PWM modulation circuit 102 is connected to the switching circuit 103, and outputs a PWM-modulated audio signal (hereinafter referred to as “PWM output signal”) to the switching circuit 103. The PWM modulation circuit 102 is set so that the duty ratio of the PWM output signal output to the switching circuit 103 by the voltage dividing resistors R109 and R110 described later is 70% when the input audio signal is no signal. ing.

  The switching circuit 103 is connected to the transformer 104, and based on the PWM output signal input from the PWM modulation circuit 102, the direction of the current flowing through the transformer 104 (the primary coil 115 that constitutes the transformer 104, which will be described later). To control.

  The transformer 104 boosts the AC voltage applied based on the reference voltage Vcc and the output from the switching circuit 103. The transformer 104 is connected to the discharge body 105 and applies a boosted AC voltage (hereinafter referred to as “high voltage pulse”) to the discharge body 105. The voltage of the high voltage pulse depends on the drive voltage Vcc applied to the temporary coil 115 of the transformer 104 and the turn ratio of the temporary coil 115 and the secondary coil 117.

  The discharge body 105 generates an unequal electric field for causing discharge due to the applied high-voltage pulse. The discharge body 105 generates sound pressure using this discharge.

  Next, an example of a circuit configuration for realizing the functions of the PWM modulation circuit 102, the switching circuit 103, the transformer 104, and the discharge body 105 will be described.

  The PWM modulation circuit 102 includes a comparator 106 to which an audio signal is input from a non-inverting input terminal, a resistor, a capacitor C108, and a sawtooth wave oscillation circuit 107 that generates a sawtooth wave signal having a predetermined period.

  The inverting input terminal of the comparator 106 is connected to the sawtooth wave oscillation circuit 107 via the voltage dividing resistors R109 and R110 and the capacitor C108. The comparator 106 is connected to the switching circuit 103 in order to output a PWM output signal to the switching circuit 103.

  The switching circuit 103 includes an inverting amplifier 111, an amplifier 113, a MOS-FET 112, and a MOS-FET 114. The inverting amplifier 111 is connected to the comparator 106 of the PWM modulation circuit 102. The MOS-FET 112 has a gate connected to the inverting amplifier 111, a source grounded, and a drain connected to the transformer 104.

  The amplifier 113 is connected to the PWM modulation circuit 102. The MOS-FET 1114 has a gate connected to the inverting amplifier 111, a source grounded, and a drain connected to the transformer 104.

  The transformer 104 includes a primary coil 115, an iron core 116, and a secondary coil 117. The primary coil 115 is connected to the drain of the MOS-FET 112 at point A, and the primary coil 115 is connected to the drain of the MOS-FET 114 at point B. The secondary coil 117 is connected to the discharge body 105.

  The discharge body 105 mainly includes a needle electrode 118 and a ring electrode 119. Needle-shaped electrode 118 is connected to secondary coil 117 at point D, and ring-shaped electrode 119 is connected to secondary coil 117 at point E. The specific configuration of the discharge body 105 will be described later with reference to FIG.

[Configuration of Discharge Speaker 201]
Next, the configuration of the discharge speaker 201 including the discharge body 105 will be described with reference to FIG.
FIG. 2 is an explanatory diagram showing the discharge speaker 201.
FIG. 2A is a perspective view showing the discharge speaker 201.
FIG. 2B is a sectional view of the needle electrode 118 of the discharge speaker 201 in the axial direction.
The discharge speaker 201 includes an insulator 203 and an acoustic horn 202 in addition to the discharge body 105, that is, the needle electrode 118 and the ring electrode 119.

  A needle electrode 118 is provided on the axis of the ring electrode 119, and an insulator 203 is provided between the ring electrode 119 and the needle electrode 118. Furthermore, an acoustic horn 202 for increasing the sound pressure level is provided on the outer periphery of the ring electrode 119. As described above, the needle electrode 118 is connected to the secondary coil 117 at the point D, and the ring electrode 119 is connected to the secondary coil 117 at the point E.

[Operation of the sound generator 101]
FIG. 3 is a waveform diagram showing an audio signal input to the PWM modulation circuit 102, a sawtooth wave signal, and a PWM output signal output from the PWM. The vertical axis indicates the voltage intensity with the amplitude of all signals shown in FIG. The horizontal axis is a time axis common to all signals shown in FIG.

Hereinafter, the operation of the sound generation apparatus 101 will be described with reference to FIG.
First, the audio signal 302 is input to the non-inverting input terminal of the comparator 106 of the PWM modulation circuit 102. On the other hand, the sawtooth wave oscillation circuit 107 outputs a sawtooth wave signal 303.

  The sawtooth wave signal 303 output from the sawtooth wave oscillation circuit 107 is given a DC offset voltage by the voltage dividing resistors R109 and R110 via the capacitor C108, and then inputted to the inverting input terminal of the comparator 106.

  The voltages of the audio signal 302 and the sawtooth wave signal 303 input to the comparator 106 are compared. Based on the comparison result, the PWM output signal 304 is output from the comparator 106 to the inverting amplifier 111 and the amplifier 113. That is, when the voltage of the audio signal 302 is higher than that of the sawtooth wave signal 303, “1” is output to the amplifier 113 and the inverting amplifier 111, and conversely, when the voltage of the audio signal 302 is lower than that of the sawtooth wave signal 303. “0” is output to the amplifier 113 and the inverting amplifier 111.

  The inverting amplifier 111 amplifies the voltage of the PWM output signal 304 and further converts it into a signal having a phase opposite to that of the PWM output signal 304 (hereinafter referred to as “inverted amplified PWM output signal”). Then, the inverting amplification PWM output signal is applied from the inverting amplifier 111 to the gate of the MOS-FET 112. Then, under the control of the MOS-FET 112, a current in the A direction from the point B flows to the primary coil 115 during the period when the inverted amplification PWM output signal is “1”. At this time, the magnitude of the current flowing through the primary coil 115 is a substantially constant value. Note that the current caused by the MOS-FET 112 does not flow through the primary coil 115 while the inverted amplification signal is “0”.

  On the other hand, the amplifier 113 generates an amplified PWM output signal by amplifying the voltage of the PWM output signal 304. The amplified PWM output signal is applied from the amplifier 113 to the gate of the MOS-FET 114. Then, under the control of the MOS-FET 114, a current in the B direction from the point A flows to the primary coil 115 during the period when the amplified PWM output signal is “1”. At this time, the magnitude of the current flowing through the primary coil 115 is constant. Note that the current caused by the MOS-FET 114 does not flow through the primary coil 115 during the period when the inverted amplification signal is “0”.

  Assuming that the direction from point A to point B is the positive direction and the direction from point B to point A is the negative direction, current that reverses positive and negative in the same cycle as the PWM output signal 304 (hereinafter referred to as “pulse current”) is obtained. It flows through the primary coil 115.

  Then, an induced electromotive force (hereinafter referred to as “high voltage pulse”) due to the pulse current flowing in the primary coil 115 is generated in the secondary coil 117. The high-pressure pulse is applied to the needle electrode 118 through the point D and applied to the electrode through the point E.

  The high voltage pulse has the same cycle as the pulse current, and the polarity is reversed in the same cycle as the pulse current. The period of the high voltage pulse applied to the needle electrode 118 and the ring electrode 119 is equal to the period of the pulse current, but the high voltage pulse applied to the needle electrode 118 is the same as the high voltage pulse applied to the ring electrode 119. It is in an antiphase relationship. That is, when the high voltage pulse applied to the needle electrode 118 is “positive”, the high voltage pulse applied to the ring electrode 119 is “negative”. On the other hand, when the high voltage pulse applied to the needle electrode 118 is “negative”, the high voltage pulse applied to the ring electrode 119 is “positive”. That is, the potential difference between the needle electrode 118 and the ring electrode 119 is alternately switched between positive and negative at the same period as the pulse current.

  As a result, an electric field is generated between the needle-shaped electrode 118 and the ring-shaped electrode 119 so as to alternate between positive and negative with the same period as the pulse current. When the high-pressure pulse applied to the needle-shaped electrode 118 is negative and the high-pressure pulse applied to the ring-shaped electrode 119 is positive, positive ions in the atmosphere are attracted to the needle-shaped electrode 118. Therefore, the needle-shaped electrode The electric field strength only near 118 increases locally. On the other hand, when the high-pressure pulse applied to the needle-shaped electrode 118 is positive and the high-pressure pulse applied to the ring-shaped electrode 119 is negative, positive ions in the atmosphere are attracted to the ring-shaped electrode 119. Are dispersed without concentrating in the vicinity of the needle electrode 118.

  When the electric field is dispersed without being concentrated in the vicinity of the needle electrode 118, the discharge plasma is extended. Then, the air around the plasma rapidly expands upon receiving heat energy, and the pushed-out surrounding air becomes dense and a positive sound pressure is generated. This sound pressure is determined by the pulse width and peak value of the PWM output signal 304 output from the PWM modulation circuit 102.

  As described above, in the present embodiment, the audio signal 302 is converted into the PWM output signal 304, and the positive and negative voltages applied to the needle electrode 118 and the ring electrode 119 are alternately switched based on the PWM output signal 304. I did it. As a result, the electrons on the needle electrode 118 and the ring electrode 119 move violently, and these electrodes themselves generate heat and promote the emission of electrons. As a result, there is an effect that it is possible to reliably maintain an amount of plasma necessary for discharge for generating sound pressure.

  In this embodiment, the current is always passed through the transformer 104 in both the “1” period and the “0” period of the PWM signal. By configuring the switching circuit 103 in this way, it is possible to always supply a constant power to the discharge body 105 regardless of the waveform of the input signal. As a result, stable discharge driving is realized.

  In the present embodiment, switching drive is performed by a PWM output signal. Thereby, low power consumption can be realized.

  In the present embodiment, when the audio signal input to the PWM modulation circuit is non-signal, the duty ratio of the PWM output signal output from the PWM modulation circuit is set to 70%, for example. Therefore, the time during which the needle electrode side is positive is longer than when the duty ratio of the PWM output signal is 50%. As a result, since the electric field is dispersed for a longer time, the plasma can be stably maintained.

  Moreover, since this embodiment does not have a mechanical vibration system with a large mass, it does not have a resonance point. Therefore, a flat frequency response can be realized up to a high frequency range.

  In the present embodiment, it is not necessary to DA convert the digital audio signal when performing PWM modulation.

  In this embodiment, the hardware configuration is very simple. This has the effect that it can be manufactured at a lower cost.

<2. Second embodiment>
[Configuration of Audio Generating Device 401]
FIG. 4 is a circuit diagram of the sound generator 401 according to the second embodiment of the present invention.
The sound generator 401 is configured by switching circuits 402a to 402n, transformers 403a to 403n, and discharges instead of the set of the switching circuit 103, the transformer 104, and the discharge body 105 that constitute the sound generator 101 of the first embodiment. A body 404 is provided. In this sound generator 401, the same reference numerals are given to the common parts with the sound generator 101 of the first embodiment, and the description thereof is omitted.

  Each switching circuit 402a-n of this sound generator 401 is the same as the switching circuit 103 of the sound generator 101 of the first embodiment. Each switching circuit 402a-n is connected in parallel with the PWM modulation circuit 102, and a PWM output signal 304 output from the PWM modulation circuit 102 is used in common by each switching circuit 402a-n. Moreover, each switching circuit 402a-n is each connected with the primary side of each transformer 403a-n.

  Since each transformer 403a-n is the same as the transformer 104 of the audio | voice generator 101 of 1st embodiment, description is abbreviate | omitted.

  The discharge body 404 includes the same number of needle electrodes 405a to 405n as the transformers 403a to 403n and one ring electrode 406. Each needle electrode 405a-n is connected to one end of the secondary side of the transformer 403a-n, respectively. The ring electrode 406 is connected to the other end of the secondary side of the transformers 403a to 403n.

[Configuration of Discharge Speaker 501]
Next, a specific configuration of the discharge speaker 501 will be described with reference to FIG.
FIG. 5 is an explanatory diagram showing the discharge speaker 501.
FIG. 5A is a cross-sectional view of the discharge speaker 501.
FIG. 5B is an enlarged view of the discharge body 404 portion of the discharge speaker 501.

  The discharge speaker 501 includes an insulator 502 and an acoustic horn 503 in addition to the discharge body 402, that is, the needle electrodes 405a to 405n and the ring electrode 406.

  On the concentric circle centering on the axis of the ring electrode 406, the needle electrodes 405a to 405n are provided at almost equal intervals, and the insulator 502 is provided between the ring electrode 406 and the needle electrode 405. Yes. Furthermore, an acoustic horn 503 for increasing the sound pressure level is provided on the outer periphery of the ring electrode 406.

  Note that the sound generation device 401 is a combination of a plurality of sound generation devices 101 and operates in the same manner as the sound generation device 101 when partially viewed. Therefore, the description of the operation of the sound generator 401 is omitted.

  As described above, in this embodiment, similarly to the first embodiment described above, it is possible to reliably maintain an amount of plasma necessary for discharge for generating sound pressure.

  Furthermore, in this embodiment, a plurality of needle-like electrodes are provided inside the ring-like electrode. Thereby, the sound pressure level can be improved.

<3. Third Embodiment>
[Configuration of Audio Generating Device 601]
FIG. 6 is a circuit diagram of a sound generator 601 according to the third embodiment of the present invention.
The sound generation device 601 includes a ΔΣ modulation circuit 602 and a plurality of delay elements 603a to 603n instead of the PWM modulation circuit 102 constituting the sound generation device 401 of the second embodiment. In this sound generator 601, common parts to the sound generators 101 and 401 of the first or second embodiment are denoted by the same reference numerals and description thereof is omitted.

  The ΔΣ modulation circuit 602 is a circuit that performs ΔΣ modulation on an input audio signal 302 in a predetermined sampling section and converts the audio signal 302 into a 1-bit stream signal. In addition, the ΔΣ modulation circuit 602 is connected to a plurality of delay elements 603, outputs this 1-bit stream signal to each delay element 603, and uses a plurality of sampling clocks used for determining a sampling period of ΔΣ modulation. To the delay element 603.

  Each delay element 603a-n outputs a 1-bit stream signal to each switching circuit 402a-n at a predetermined timing by the same number of bits as the sampling interval based on the sampling clock input from the ΔΣ modulation circuit 602. Note that the switching circuits 402a to 402n, the transformers 403a to 403n, and the discharge bodies 404 are as described above, and thus description thereof is omitted.

[Operation of the sound generator 601]
Next, the operation of the sound generator 601 will be described.
First, the audio signal 302 is input to the ΔΣ modulation circuit 602. Then, the audio signal 302 input to the ΔΣ modulation circuit 602 is ΔΣ modulated in a sampling period based on the sampling clock, converted into a 1-bit stream signal, and output to each delay element 603a-n. At this time, the sampling clock is also output to each delay element 603a-n.

  The 1-bit stream signal input to the first delay element 603a is output to the first switching circuit 402a by the same number of bits as in the sampling period. The 1-bit stream signal input to the second delay element 603b is output from the second bit of the 1-bit stream signal to the second switching circuit 402b by the same number of bits as the sampling period. The 1-bit stream signal input to the third delay element 603 is output from the third bit of the 1-bit stream signal to the third switching circuit 402c by the same number of bits as the sampling interval. That is, the 1-bit stream signal input to the n-th delay element 603n is output from the n-th bit of the 1-bit stream signal to the n-th switching circuit 402n by the same number of bits as the sampling period.

  Although the 1-bit stream signals input to the switching circuits 402a to 402n are different, the switching circuits 402a to 402n, the transformers 403a to 403n, and the discharge body 404 operate in the same manner. In the following, only the operations relating to the switching circuit 402a, the transformer 403a, and the discharge body 404 will be described, and descriptions of the operations relating to the switching circuits 402b to n and the transformers 403b to n will be omitted. Further, when the switching circuit 402, the transformer 403, and the discharge body 404 are viewed as a single unit, they are the same as those described in the description of the first embodiment.

  The 1-bit stream signal input from the first delay element 603a to the first switching circuit 402a controls the magnitude and direction of the current flowing through the transformer 403a and causes a pulse current to flow through the primary side of the transformer 403a. .

  Then, an induced electromotive force caused by the pulse current flowing on the primary side of the transformer 403a, that is, a high voltage pulse is generated on the secondary side of the transformer 403. The high-voltage pulse is applied to the needle electrode 405a and the ring electrode 406, respectively.

  The high voltage pulse has the same cycle as the pulse current, and the polarity is reversed in the same cycle as the pulse current. The cycle of the high voltage pulse applied to the needle electrode 405a and the ring electrode 406 is equal to the cycle of the pulse current, but the high voltage pulse applied to the needle electrode 405a is the same as the high voltage pulse applied to the ring electrode 406. It is in an antiphase relationship. That is, when the high voltage pulse applied to the needle electrode 405a is “positive”, the high voltage pulse applied to the ring electrode 406 is “negative”. On the other hand, when the high voltage pulse applied to the needle electrode 405a is “negative”, the high voltage pulse applied to the ring electrode 406 is “positive”. That is, the potential difference between the needle electrode 405a and the ring electrode 406 alternates between positive and negative at the same cycle as the pulse current.

Due to such a voltage, an electric field is generated between the needle-like electrode 405a and the ring-like electrode 406 in which positive and negative are alternately switched in the same cycle as the pulse current. A discharge due to this electric field is generated between the needle electrode 405a and the ring electrode 406, and a sound pressure corresponding to the discharge is generated. At this time, an electric field corresponding to the 1-bit stream signal input to each switching circuit 402a-n is generated between the needle-like electrodes 405a-n and the ring-like electrode 406, and due to corona discharge caused by this electric field. Sound pressure is generated. Then, the sound pressures generated from the discharge body 404 are synthesized in the space, and a predetermined sound wave is generated.
In other words, the adder portion of the moving average filter used for analogizing the ΔΣ modulation signal is a plurality of needle-like electrodes 405a, 405b. . . 405n corresponds to the space surrounding them.

  As described above, in this embodiment, the audio signal is converted into a 1-bit stream signal, and the positive and negative voltages applied to the needle electrode and the ring electrode are alternately switched based on the 1-bit stream signal. . As a result, electrons on the needle-like electrode and the ring-like electrode move violently, and these electrodes themselves generate heat and promote the emission of electrons. As a result, there is an effect similar to that of the first embodiment in which it is possible to reliably maintain an amount of plasma necessary for discharge for generating sound pressure.

  In the present embodiment, a 1-bit stream signal representing the power spectral density of the audio signal output from the ΔΣ modulator is output from each sound discharger to the space via each delay element. Thereby, when the sound pressure generated in each sound circuit is synthesized in space, the effect of the low-pass filter is obtained. That is, there is an effect that high frequency noise outside the audible band can be reduced.

<4. Fourth Embodiment>
[Configuration of Audio Generator 701]
FIG. 7 is a circuit diagram of a sound generator 701 according to the fourth embodiment of the present invention.
The voice generation device 701 is provided with an n-bit ΔΣ modulation circuit 702 and a unicode encoding conversion circuit 703 instead of the PWM modulation circuit 102 constituting the voice generation device 401 of the second embodiment. . In this sound generation device 701, common parts to the sound generation devices 101, 401, 601 of the first, second, or third embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The n-bit ΔΣ modulation circuit 702 is a circuit that performs ΔΣ modulation on an input audio signal 302 in a predetermined sampling period and converts the audio signal 302 into an n-bit binary code. Further, the n-bit ΔΣ modulation circuit 702 is connected to the unicode encoding circuit 703, and outputs this n-bit binary code to the unicode encoding circuit 703.

The unicode encoding circuit 703 is a circuit that converts an n-bit binary code into a unicode code. The unicode encoding circuit 703 unicodes the n-bit binary code input from the n-bit ΔΣ modulation circuit 703 to generate a 2 ⁿ −1 bit unicode. The unicode code circuit 703 is connected in parallel to the switching circuits 402a to 402n, and outputs the 2 ⁿ −1 bit unicode code to the switching circuits 402a to ⁿ bit by bit. ^{Specifically,} outputs 1 bit of the ² n -1 bit unary code to the switching circuit ^402a, and outputs the second bit of the ² n -1 bit unary code to the switching circuit ^{402b, 2} n -1 bits The nth bit of the unicode is output to the switching circuit 402n. Therefore, the switching circuit 402 is provided by the number of bits of 2 ⁿ −1 bit unicode. Note that the switching circuits 402a to 402n, the transformers 403a to 403n, and the discharge bodies 404 are as described above, and thus description thereof is omitted.

[Operation of the sound generator 601]
Next, the operation of the sound generator 601 will be described.
First, the audio signal 302 is input to the n-bit ΔΣ modulation circuit 702. Then, the audio signal 302 input to the ΔΣ modulation circuit 602 is ΔΣ modulated in the sampling period based on the sampling clock, converted into an n-bit binary code, and output to the single encoding conversion circuit 703.

The n-bit binary code input to the conversion code 703 is converted to a 2 ⁿ −1 bit unicode code and output to the switching circuits 403a- ⁿ . Specifically, the first bit of the 2 ⁿ -1 bit unicode code is output to the switching circuit 403a, and the second bit of the 2 ⁿ -1 bit unicode code is output to the switching circuit 403b and 2 ⁿ -1 bits. The nth bit of the unicode is output to the switching circuit 403n.

Each of the switching circuits 402a to 402n operates the transformers 403a to 403n and the discharge body 404 based on the input 2 ⁿ −1 bit unicode. In the following, only the operations relating to the switching circuit 402a, the transformer 403a, and the discharge body 404 will be described, and descriptions of the operations relating to the switching circuits 402b to n and the transformers 403b to n will be omitted. Further, when the switching circuit 402, the transformer 403, and the discharge body 404 are viewed as a single unit, they are the same as those described in the description of the first embodiment.

The first bit of the 2 ⁿ −1 bit unicode code input from the single encoding 703 to the first switching circuit 402a controls the magnitude and direction of the current flowing through the transformer 403a to control the primary of the transformer 403a. Apply a pulse current to the side.

  Then, an induced electromotive force caused by the pulse current flowing on the primary side of the transformer 403a, that is, a high voltage pulse is generated on the secondary side of the transformer 403. The high-voltage pulse is applied to the needle electrode 405a and the ring electrode 406, respectively.

  The high voltage pulse has the same cycle as the pulse current, and the polarity is reversed in the same cycle as the pulse current. The cycle of the high voltage pulse applied to the needle electrode 405a and the ring electrode 406 is equal to the cycle of the pulse current, but the high voltage pulse applied to the needle electrode 405a is the same as the high voltage pulse applied to the ring electrode 406. It is in an antiphase relationship. That is, when the high voltage pulse applied to the needle electrode 405a is “positive”, the high voltage pulse applied to the ring electrode 406 is “negative”. On the other hand, when the high voltage pulse applied to the needle electrode 405a is “negative”, the high voltage pulse applied to the ring electrode 406 is “positive”. That is, the potential difference between the needle electrode 405a and the ring electrode 406 alternates between positive and negative at the same cycle as the pulse current.

Due to such a voltage, an electric field is generated between the needle-like electrode 405a and the ring-like electrode 406 in which positive and negative are alternately switched in the same cycle as the pulse current. A discharge due to this electric field is generated between the needle electrode 405a and the ring electrode 406, and a sound pressure corresponding to the discharge is generated. At this time, an electric field is generated between the needle-like electrodes 405a to 405n and the ring-like electrode 406 in accordance with the 2 ⁿ -1 bit unicode code input to the switching circuits 402a to 402n. Sound pressure is generated by corona discharge. Then, the sound pressures generated from the discharge body 404 are synthesized in the space, and a predetermined sound wave is generated.

As described above, in this embodiment, the audio signal is subjected to ΔΣ modulation to be n-bit encoded, and the n-bit encoded audio signal is converted into a 2 ⁿ −1 bit unicode code. The positive and negative voltages applied to the needle electrode and the ring electrode are alternately switched based on the 2 ⁿ -1 bit unicode. As a result, electrons on the needle-like electrode and the ring-like electrode move violently, and these electrodes themselves generate heat and promote the emission of electrons. As a result, there is an effect similar to that of the first embodiment in which it is possible to reliably maintain an amount of plasma necessary for discharge for generating sound pressure. Furthermore, the effect of the low-pass filter is obtained when the sound pressure generated in each sound circuit is synthesized in space based on the 2 ⁿ −1 bit unicode. Thereby, the same effect as 3rd embodiment that the high frequency noise outside an audible band can be reduced is acquired.

  In each of the embodiments described above, a needle electrode and a ring electrode are used as electrodes that generate an unequal electric field when a voltage is applied. However, other electrodes may be used if an unequal electric field is generated by applying a voltage.

  In each of the above-described embodiments, when the distance between the electrodes is short, the entire path breaks down and arc discharge occurs. However, a so-called Tesla coil is used to generate a higher voltage and corona discharge. May be.

  Moreover, in each embodiment mentioned above, although the acoustic horn for increasing a sound pressure level was provided, the shape of a ring-shaped electrode can be extended and it can also be used as an alternative of an acoustic horn.

  In the first and second embodiments described above, when the audio signal input to the PWM modulation circuit is no signal, the duty ratio of the PWM output signal output from the PWM modulation circuit is set to 70%. However, it is not limited to 70%. If the duty ratio of the WM output signal is deviated by a predetermined value from 50%, the same effect as in the first embodiment can be obtained.

  In the first and second embodiments described above, a transformer is used, but a resonant transformer may be used instead. In this case, the discharge amplitude can be increased by bringing the carrier frequency when the PWM modulation circuit performs PWM modulation close to the resonance frequency of the resonance transformer.

  As mentioned above, although the example of each embodiment of the present invention was explained, the present invention is not limited to the above-mentioned each embodiment example, and includes other modification examples and application examples without departing from the gist of the present invention. Needless to say.

1 is a circuit diagram showing a sound generator according to a first embodiment of the present invention. It is explanatory drawing which shows a discharge speaker. It is a wave form diagram which shows an audio | voice signal, a sawtooth wave signal, and a PWM output signal. It is a block diagram which shows the audio | voice generator which concerns on 2nd embodiment of this invention. It is explanatory drawing which shows a discharge speaker. It is a block diagram which shows the audio | voice generator which concerns on 3rd embodiment of this invention. It is a block diagram which shows the audio | voice generator which concerns on 4th embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Sound generator 102 ... PWM modulation circuit 103 ... Switching circuit 104 ... Transformer 105 ... Discharge body 106 ... Comparator 107 ... Sawtooth oscillation circuit C108 ... Capacitor 109 ... Voltage dividing resistor 110 Reference voltage resistor, 111 ... Inverting amplifier, 112 ... MOS-FET, 113 ... Amplifier, 114 ... MOS-FET, 115 ... Primary coil, 116 ... Insulating iron core, 117 ... Secondary coil, 118 ... Needle electrode, 119 DESCRIPTION OF SYMBOLS ... Ring electrode, 201 ... Discharge speaker, 202 ... Acoustic horn, 203 ... Insulator, 302 ... Audio signal, 303 ... Sawtooth wave signal, 304 ... PWM output signal, 401 ... Audio generator, 402 ... Switching circuit, 403 ... transformer, 404 ... discharger, 405 ... needle electrode, 406 ... ring electrode, 501 ... discharge speaker, 502 ... absence Body, 503 ... acoustic horn, 601 ... sound generation device, 602 ... .DELTA..SIGMA modulation circuit, 603 ... delay element, 701 ... sound generation device, 702 ... n-bit .DELTA..SIGMA modulation circuit, 703 ... unary encoding conversion circuit

Claims (9)

A first switch;
A second switch driven in reverse logic with respect to the first switch;
The first switch and the second switch are connected to both ends of the primary side, respectively, a transformer for applying a driving voltage to the center of the primary side and outputting a high voltage pulse to the secondary side;
A discharge electrode to which the high-pressure pulse is applied;
A sound generator comprising: further,
PWM modulation is performed on the input audio signal, a PWM signal obtained by binarizing the audio signal is generated, and a PWM modulation circuit connected to the first switch and the second switch is provided.
The sound generator according to claim 1. 3. The audio according to claim 2, wherein the PWM modulation circuit is provided with an offset so as to output a PWM signal in which a duty ratio is biased by a predetermined value from 50% when the input audio signal is no signal. 4. Generator. The sound generator according to claim 1, wherein the discharge electrode has a structure that forms an unequal electric field when a voltage is applied. The sound generation measure according to claim 4, wherein the discharge electrode is an electrode composed of a needle electrode and a ring electrode. The sound generator according to claim 1, wherein the discharge is a corona discharge or an arc discharge. The sound generator according to claim 1, wherein the transformer is a resonance transformer, and a carrier frequency when the sound signal is PWM-modulated by the PWM modulator matches a resonance frequency of the resonance transformer. A PWM modulation circuit that performs PWM modulation on the input audio signal;
A first switch connected to the output of the PWM modulation circuit, a second switch connected to the output of the PWM modulation circuit, driven by the inverse logic of the first switch, the first switch and the second switch A first high-voltage pulse generator comprising: a switch connected to both ends of the primary side; a transformer that outputs a high-voltage pulse to the secondary side by applying a driving voltage to the center of the primary side;
A second high voltage pulse generator having the same configuration as the first high voltage pulse generator connected to the output of the PWM modulation circuit;
A first acicular electrode connected to one end of the transformer on the secondary side of the first high voltage pulse generator; and a second needle connected to one end on the secondary side of the transformer of the second high voltage pulse generator. A sound generating device comprising: a two-needle electrode; and a discharge electrode comprising a first electrode of the first high-voltage pulse generator and a ring electrode connected to the other end of the secondary side of each transformer of the first high-voltage pulse generator . A ΔΣ modulation circuit for performing ΔΣ modulation on the input audio signal;
A first delay element connected to the output of the ΔΣ modulation circuit;
A first switch connected to the first delay element, a second switch driven by the reverse logic of the first switch, the first switch and the second switch are respectively connected to both ends of the primary side, A first high voltage pulse generator comprising a transformer that outputs a high voltage pulse to the secondary side by applying a driving voltage to the center of the primary side;
A second delay element connected to the first delay element;
A second high-voltage pulse generator having the same configuration as the first high-voltage pulse generator connected to the second delay element;
A first acicular electrode connected to one end of the transformer on the secondary side of the first high voltage pulse generator; and a second needle connected to one end on the secondary side of the transformer of the second high voltage pulse generator. A sound generating device comprising: a two-needle electrode; and a discharge electrode comprising a first electrode of the first high-voltage pulse generator and a ring electrode connected to the other end of the secondary side of each transformer of the first high-voltage pulse generator .

Images