Semiconductor device and electronic apparatus

Abstract

To provide a semiconductor device capable of outputting high-quality sound to a sound output device having a narrow frequency band capable of outputting sound.SOLUTION: A semiconductor device includes: a sound data reading circuit that reads sound data from a memory; a first pulse width modulation signal generation circuit that generates a first pulse width modulation signal whose pulse width changes based on the sound data; and a second pulse width modulation signal generation circuit that generates a second pulse width modulation signal whose pulse width changes based on the sound data. The first pulse width modulation signal is a signal for causing a first sound output device including a first piezoelectric element and a first diaphragm to output sound, and the second pulse width modulation signal is a signal for causing a second sound output device including a second piezoelectric element and a second diaphragm and having a higher resonance frequency than the first sound output device to output sound.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device and an electronic device. [Background technology]

[0002] Patent Document 1 describes a circuit device in which a PWM signal output circuit outputs a PWM signal to a sound output device based on pseudo sound data using harmonics that belong to a frequency band that the sound output device can output, out of multiple harmonics of a fundamental tone that belong to a frequency band lower than the lower limit of the frequency band that the sound output device can output. According to the circuit device described in Patent Document 1, low-frequency sounds that the sound output device cannot actually output are pseudo-output by using the harmonics, thereby enabling high-quality audio reproduction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-072465 Summary of the Invention [Problem to be solved by the invention]

[0004] In the circuit device described in Patent Document 1, low-band sound is output in a pseudo manner, but the low-band sound is not actually output, so there is room for improvement in order to reproduce high-quality audio. [Means for solving the problem]

[0005] One aspect of the semiconductor device according to the present invention is a sound data reading circuit for reading sound data from the memory; a first pulse width modulation signal generating circuit that generates a first pulse width modulation signal whose pulse width changes based on the sound data; a second pulse width modulation signal generating circuit that generates a second pulse width modulation signal whose pulse width changes based on the sound data; Equipped with the first pulse width modulation signal is a signal for causing a first sound output device including a first piezoelectric element and a first diaphragm to output a sound; The second pulse width modulation signal is a signal for causing a second sound output device, which includes a second piezoelectric element and a second diaphragm and has a higher resonance frequency than the first sound output device, to output sound.

[0006] One aspect of the electronic device according to the present invention is One aspect of the semiconductor device; the first sound output device; the second sound output device; Equipped with. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing an example of the configuration of a semiconductor device and a sound reproducing device according to a first embodiment; [Figure 2] FIG. 2 is a diagram showing a configuration example of a booster circuit. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. 10 is a diagram showing an example of the relationship between the characteristics of a human voice and the sound reproduction characteristics of a sound output device. [Figure 6] FIG. 10 is a diagram showing an example of a pulse width modulated signal. [Figure 7] FIG. 10 is a diagram showing an example of the configuration of a semiconductor device and a sound reproducing device according to a second embodiment. [Figure 8] 10A and 10B are diagrams showing configuration examples of a semiconductor device and a sound reproducing device according to modified examples; [Figure 9] 10A and 10B are diagrams showing configuration examples of a semiconductor device and a sound reproducing device according to other modified examples; [Figure 10] FIG. 1 is a functional block diagram showing a configuration example of an electronic device using the semiconductor device according to a first embodiment. [Figure 11] FIG. 10 is a functional block diagram showing a configuration example of an electronic device using the semiconductor device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that the embodiments described below do not unduly limit the content of the present invention as defined in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0009] 1. Semiconductor device and sound reproduction device 1-1. First embodiment Fig. 1 is a diagram showing an example of the configuration of a semiconductor device 2 and a sound reproducing device 1 according to a first embodiment. As shown in Fig. 1, the sound reproducing device 1 includes a semiconductor device 2, an MCU 3, an external memory 4, n boost circuits 6-1 to 6-n, and n sound output devices 7-1 to 7-n. MCU is an abbreviation for Micro Controller Unit. n is an integer of 2 or greater.

[0010] 1, the semiconductor device 2 is connected to an MCU 3, an external memory 4, and n boost circuits 6-1 to 6-n, and includes a control circuit 10, a sound data reading circuit 20, a memory 30, a memory interface circuit 40, and n pulse width modulation signal generating circuits 50-1 to 50-n. The semiconductor device 2 may be a one-chip semiconductor integrated circuit device, or may be composed of semiconductor integrated circuit devices on multiple chips, or may be at least partially composed of electronic components other than semiconductor integrated circuit devices.

[0011] The memory 30 is a memory built into the semiconductor device 2 and stores multiple pieces of sound data. The memory 30 is a semiconductor memory such as a nonvolatile memory or RAM. RAM is an abbreviation for Random Access Memory. If the memory 30 is a nonvolatile memory, multiple pieces of sound data may be written to the memory 30 in advance.

[0012] The external memory 4 stores multiple pieces of sound data. The external memory 4 is a semiconductor memory such as a nonvolatile memory or a RAM. If the external memory 4 is a nonvolatile memory, the multiple pieces of sound data may be written in advance to the external memory 4. The memory interface circuit 40 is an interface circuit that reads data from the external memory 4.

[0013] The various sound data stored in the memory 30 or the external memory 4 may be, for example, voice data such as warnings or guidance, or sound data such as melodies.

[0014] The sound data reading circuit 20 reads sound data from the memory 30 and outputs the read sound data as sound data SD to the pulse width modulation signal generating circuits 50-1 to 50-n in common. Alternatively, the sound data reading circuit 20 reads sound data from the external memory 4 via the memory interface circuit 40 and outputs the read sound data as sound data SD to the pulse width modulation signal generating circuits 50-1 to 50-n in common. Specifically, the sound data reading circuit 20 transmits a read command to the external memory 4 via the memory interface circuit 40, and the external memory 4 outputs the sound data specified by the read command. Then, the sound data reading circuit 20 The circuit 20 acquires the sound data output from the external memory 4 via the memory interface circuit 40 and outputs the acquired sound data as sound data SD to the pulse width modulation signal generation circuits 50-1 to 50-n in common. The sound data SD is data of a predetermined number of bits whose value changes in time series at a sampling period.

[0015] The control circuit 10 controls the sound data reading circuit 20. Specifically, the control circuit 10 communicates with an MCU 3 external to the semiconductor device 2 and outputs a command CMD to the sound data reading circuit 20 in accordance with instructions from the MCU 3. For example, the control circuit 10 outputs a command CMD to the sound data reading circuit 20 to instruct it to read specific sound data from memory 30. The sound data reading circuit 20 then reads the sound data specified by the command CMD from memory 30 and outputs the read sound data as sound data SD to all of the pulse-width modulation signal generation circuits 50-1 to 50-n. Alternatively, the control circuit 10 outputs a command CMD to the sound data reading circuit 20 to instruct it to read specific sound data from external memory 4. The sound data reading circuit 20 then reads the sound data specified by the command CMD from external memory 4 via the memory interface circuit 40 and outputs the read sound data as sound data SD to all of the pulse-width modulation signal generation circuits 50-1 to 50-n.

[0016] The pulse-width modulation signal generation circuit 50-i generates pulse-width modulation signals DOPi and DONi, whose pulse widths change, based on sound data SD. For example, the pulse-width modulation signal generation circuit 50-1 generates pulse-width modulation signals DOP1 and DON1 based on sound data SD, and the pulse-width modulation signal generation circuit 50-2 generates pulse-width modulation signals DOP2 and DON2 based on sound data SD. The pulse-width modulation signals DOPi and DONi are each digital signals. For example, the pulse-width modulation signals DOPi and DONi have inverted logical levels. For example, the pulse-width modulation signal generation circuit 50-i may generate the pulse-width modulation signals DOPi and DONi based on table information that defines the correspondence between the value of a predetermined number of bits of data input as sound data SD and the logical values ​​of a predetermined number of bits of the pulse-width modulation signals DOPi and DONi. The table information is stored in advance, for example, in a nonvolatile memory (not shown). The pulse width modulation signals DOPi and DONi are signals whose duty ratio changes with each sampling period of the sound data SD. The duty ratio is the ratio between high and low levels. In the following, "pulse width modulation" will be abbreviated as "PWM."

[0017] The PWM signals DOPi and DONi are input to a boost circuit 6-i provided outside the semiconductor device 2. The boost circuit 6-i boosts the PWM signals DOPi and DONi to generate drive signals DOXPi and DOXNi, and outputs the drive signals DOXPi and DOXNi to the sound output device 7-i. For example, the boost circuit 6-i boosts the PWM signals DOP1 and DON1 to generate drive signals DOXP1 and DOXN1 that drive the sound output device 7-1, and the boost circuit 6-2 boosts the PWM signals DOP2 and DON2 to generate drive signals DOXP2 and DOXN2 that drive the sound output device 7-2.

[0018] Fig. 2 is a diagram showing an example of the configuration of the boost circuit 6-i. As shown in Fig. 2, the boost circuit 6-i includes N-channel MOSFETs 61 and 62 and resistors 63, 64, and 65. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor.

[0019] The MOSFET 61 has a drain connected to the node N1, a source connected to the ground node, and a gate to which the PWM signal DOPi is input from the PWM signal generating circuit 50-i. The MOSFET 62 has a drain connected to the node N2, a source connected to the ground node, and a gate to which the PWM signal DONi is input from the PWM signal generating circuit 50-i.

[0020] Resistor 63 has one end connected to a power supply node and the other end connected to node N1. The power supply node is a node to which a power supply voltage VCC is supplied. Resistor 64 has one end connected to the power supply node and the other end connected to node N2. Resistor 65 has one end connected to node N1 and outputs a drive signal DOXPi from the other end. Also, node N2 outputs a drive signal DOXNi.

[0021] In the boost circuit 6-i configured as described above, when the PWM signal DOPi is at a high level voltage and the PWM signal DONi is at a low level voltage, the MOSFET 61 turns on, causing the drive signal DOXPi to go to a low level voltage, and the MOSFET 62 turns off, causing the drive signal DOXNi to go to a high level voltage. Also, when the PWM signal DOPi is at a low level voltage and the PWM signal DONi is at a high level voltage, the MOSFET 61 turns off, causing the drive signal DOXPi to go to a high level voltage, and the MOSFET 62 turns on, causing the drive signal DOXNi to go to a low level voltage. That is, one of the drive signals DOXPi and DOXNi goes to a high level and the other goes to a low level. Here, the high-level voltage of the drive signals DOXPi and DOXNi is the power supply voltage VCC, and the low-level voltage of the drive signals DOXPi and DOXNi is the ground voltage (0 V). Therefore, one of the drive signals DOXPi and DOXNi goes to the power supply voltage VCC, and the other goes to 0 V.

[0022] As will be described in detail later, the sound output device 7-i includes a piezoelectric element 71, and generates sound by deforming the piezoelectric element 71 with drive signals DOXPi and DOXNi. Therefore, the other end of the resistor 65 from which the drive signal DOXPi is output and the node N2 from which the drive signal DOXNi is output are connected to one end and the other end of the piezoelectric element 71 of the sound output device 7-i, respectively. One end of the drive signals DOXPi and DOXNi becomes the power supply voltage VCC, and the other end becomes 0 V, so that a potential difference equivalent to the power supply voltage VCC occurs across the piezoelectric element 71. In order to sufficiently deform the piezoelectric element 71, the power supply voltage VCC is set to, for example, several tens of volts.

[0023] Returning to the explanation of FIG. 1, the sound output devices 7-1 to 7-n are devices that output sounds. Specifically, the sound output device 7-i outputs sounds corresponding to the input drive signals DOXPi and DOXNi, where i is an integer between 1 and n. The sounds output from the sound output device 7-i may be voice or sounds other than voice. The sound output device 7-i can output various types of information such as warnings and guidance as voice or sound. The sound output devices 7-1 to 7-n have different resonance frequencies and therefore different sizes, but may have the same basic structure.

[0024] 3 and 4 are diagrams illustrating an example of the structure of the sound output device 7-i. FIG. 3 is a perspective view of the sound output device 7-i, and FIG. 4 is a cross-sectional view of the sound output device 7-i. As illustrated in FIGS. 3 and 4, the sound output device 7-i includes a piezoelectric element 71 and a diaphragm 72. The diaphragm 72 is a disk-shaped metal plate having a first surface 72a and a second surface 72b. The piezoelectric element 71 has a first surface 71a and a second surface 71b and is disk-shaped with a smaller diameter than the diaphragm 72. A wiring 74 is bonded to the first surface 71a of the piezoelectric element 71 by a conductive bonding member 76, and the second surface 71b of the piezoelectric element 71 is bonded to the first surface 72a of the diaphragm 72 by a conductive bonding member 78. A wiring 75 is bonded to the first surface 72a of the diaphragm 72 by a conductive bonding member 77. The bonding members 76, 77, and 78 are, for example, solder.

[0025] 3 and 4, the sound output device 7-i may include a housing 73 that houses a piezoelectric element 71 and a diaphragm 72. Wirings 74 and 75 extend from the inside to the outside of the housing 73. Drive signals DOXPi and DOXNi are transmitted through the wirings 74 and 75, respectively. Therefore, the drive signals DOXPi and DOXNi transmitted through the wirings 74 and the bonding member 76 are transmitted to the first surface 71a of the piezoelectric element 71. 2. Since the drive signals DOXPi and DOXNi are in opposite phases, the piezoelectric element 71 is deformed, and the diaphragm 72 vibrates in response to the deformation of the piezoelectric element 71.

[0026] The vibration of diaphragm 72 causes the surrounding air to vibrate, generating sound. However, because the sound generated by the vibration of diaphragm 72 is small, it is amplified by resonance in housing 73. In other words, housing 73 functions as a resonance box. The amplified sound propagates to the outside through opening 73a of housing 73. To enhance the resonance effect, the resonant frequency of diaphragm 72 and the resonant frequency of housing 73 are designed to match. Note that the larger the diaphragm 72 and housing 73 are, the lower the resonant frequency, and the smaller the diaphragm 72 and housing 73 are, the higher the resonant frequency.

[0027] In the sound output device 7-i having such a structure, the period at which the diaphragm 72 vibrates changes according to the pulse period of the drive signals DOXPi and DOXNi, and it is possible to output sound in a narrow frequency band including the resonance frequency. However, the sound output device 7-i cannot output sound including components in the range of 100 Hz to several kHz, such as human voice. Therefore, in this embodiment, n sound output devices 7-1 to 7-n, each having a different resonance frequency, output sounds in different frequency bands, and these sounds mix together in space to reproduce a sound including various components in a wide frequency band.

[0028] For example, taking the case of n=2 as an example, FIG. 5 shows an example of the relationship between the characteristics of human voice and the sound output characteristics of sound output devices 7-1 and 7-2. In FIG. 5, the horizontal axis is frequency (Hz) and the vertical axis is sound pressure (dB). HV is the characteristics of human voice, G1 is the sound output characteristic of sound output device 7-1, and G2 is the sound output characteristic of sound output device 7-2. As shown by HV in FIG. 5, human voice contains various components in a wide frequency band. On the other hand, sound output device 7-1 has a resonance frequency of around 2 kHz, and a high sound pressure region exists in a frequency band of approximately 1500 Hz to 3 kHz. Furthermore, sound output device 7-2 has a resonance frequency of around 4 kHz, and a high sound pressure region exists in a frequency band of approximately 3 kHz to 5 kHz. In other words, the resonance frequency of sound output device 7-2 is higher than the resonance frequency of sound output device 7-1, and the frequency band that sound output device 7-2 can output is higher than the frequency band that sound output device 7-1 can output. Therefore, in this embodiment, the semiconductor device 2 generates PWM signals DOP1 and DON1 based on the sound data SD to cause the sound output device 7-1 to output a low-frequency sound, and also generates PWM signals DOP2 and DON2 based on the sound data SD to cause the sound output device 7-2 to output a high-frequency sound.

[0029] 6 is a diagram showing an example of PWM signals DOP1, DON1 and PWM signals DOP2, DON2. As shown in FIG. 6, the high level of the PWM signals DOP1, DON1 is the power supply voltage VDD of the semiconductor device 2, and the low level is the ground voltage VSS of the semiconductor device 2. Similarly, the high level of the PWM signals DOP2, DON2 is the power supply voltage VDD, and the low level is the ground voltage VSS. In other words, the voltage amplitude of the PWM signals DOP1, DON1 is equal to the voltage amplitude of the PWM signals DOP2, DON2.

[0030] Furthermore, the pulse period T2 of the PWM signals DOP2 and DON2 for causing the sound output device 7-2 to output a high-frequency sound is shorter than the pulse period T1 of the PWM signals DOP1 and DON1 for causing the sound output device 7-1 to output a low-frequency sound. Specifically, the average value of the pulse periods T2 of the PWM signals DOP2 and DON2 is smaller than the average value of the pulse periods T1 of the PWM signals DOP1 and DON1. The pulse period T1 is the time from when the PWM signals DOP1 and DON1 change from low level to high level until the next change from low level to high level, and the pulse period T2 is the time from when the PWM signals DOP2 and DON2 change from low level to high level until the next change from low level to high level. It is the time from when the signal changes from low level to high level again.

[0031] In particular, as shown in HV in FIG. 5, peak frequency components contained in human voices are called formants, and reproducing formants as much as possible makes them easier to hear. Low frequencies below 1 kHz contain fewer formants and have smaller noise components than high frequencies. However, low frequencies below 1 kHz are far from the resonant frequency of the sound output device 7-1, resulting in low sound pressure, as shown by G1 in FIG. 5. Therefore, by minimizing the number of switching times of the PWM signals DOP1 and DON1 during the sampling period Ts of the sound data SD to just one, losses are reduced and sound pressure is maximized. By matching the pulse period T1 of the PWM signals DOP1 and DON1 with the sampling period Ts in this way, sound pressure is prioritized over sound quality for low-frequency sounds output by the sound output device 7-1. In other words, the PWM signals DOP1 and DON1 may be signals whose pulse widths vary but whose pulse period T1 is constant. First table information for generating such PWM signals DOP1 and DON1 is created in advance, and the PWM signal generating circuit 50-1 generates the PWM signals DOP1 and DON1 based on the first table information.

[0032] On the other hand, since many formants are high-frequency components above 1 kHz, reproducing high-frequency components can reproduce sounds closer to human speech. Because frequencies above 1 kHz are close to the resonant frequency of the sound output device 7-2, the sound pressure is high, as shown by G2 in FIG. 5. However, noise components are easily superimposed in the high-frequency band. To reduce the high-frequency noise components, the PWM signals DOP2 and DON2 are signals whose pulse width and pulse period T2 change and are switched multiple times during the sampling period Ts of the sound data SD. In this way, sound pressure is ensured for the high-frequency sounds output by the sound output device 7-2. Therefore, by making the pulse period T2 of the PWM signals DOP2 and DON2 shorter than the sampling period Ts, sound quality is prioritized over sound pressure. Furthermore, as shown in FIG. 6, the pulse-width modulated signals DOP2 and DON2 may have waveforms symmetrical around half the pulse period T1 of the pulse-width modulated signals DOP1 and DON1. This suppresses sudden changes in the sound pressure output by the sound output device 7-2, thereby suppressing harmonic distortion. Second table information for generating PWM signals DOP2 and DON2 that reduce such noise components and harmonic distortion is created in advance, and the PWM signal generation circuit 50-2 generates the PWM signals DOP2 and DON2 based on the second table information.

[0033] In addition, in order to prevent aliasing noise from being superimposed on the PWM signals DOP1, DON1 and PWM signals DOP2, DON2, band-pass filtering or low-pass filtering is incorporated into the first table information and second table information for the sound data SD. By incorporating noise reduction processing or filtering processing into the table information in this way, a filter circuit or a sigma-delta modulation circuit for reducing noise is not required in the upstream stage of the PWM signal generation circuits 50-1 to 50-n, thereby reducing the circuit scale of the semiconductor device 2. Furthermore, since a sigma-delta modulation circuit that operates with a high-frequency clock signal is not required, the power consumption of the semiconductor device 2 is reduced.

[0034] When the semiconductor device 2 outputs the PWM signals DOP1, DON1 and DOP2, DON2 during the same period, the low-frequency sound output by the sound output device 7-1 and the high-frequency sound output by the sound output device 7-2 are mixed in space, reproducing a sound containing various components across a wide frequency band contained in the sound data SD. That is, as shown in FIG. 5, the two sound output devices 7-1 and 7-2 function as pseudo speakers having sound output characteristics that combine the sound output characteristics G1 and G2. Therefore, the sound reproduction device 1 including the semiconductor device 2 and the sound output devices 7-1 and 7-2 can reproduce sound data such as human voice data and melody data. Furthermore, the sound reproduction device 1 can reproduce sound data in various languages ​​with different frequency bands.

[0035] The PWM signals DOP1 and DON1 are an example of a "first pulse width modulation signal," and the PWM signals DOP2 and DON2 are an example of a "second pulse width modulation signal." The PWM signal generation circuit 50-1 is an example of a "first pulse width modulation signal generation circuit," and the PWM signal generation circuit 50-2 is an example of a "second pulse width modulation signal generation circuit." The sound output device 7-1 is an example of a "first sound output device," and the sound output device 7-2 is an example of a "second sound output device." The piezoelectric element 71 of the sound output device 7-1 is an example of a "first piezoelectric element," and the piezoelectric element 71 of the sound output device 7-2 is an example of a "second piezoelectric element." The diaphragm 72 of the sound output device 7-1 is an example of a "first diaphragm," and the diaphragm 72 of the sound output device 7-2 is an example of a "second diaphragm." Furthermore, the boost circuit 6-1 is an example of a “first boost circuit,” and the boost circuit 6-2 is an example of a “second boost circuit.” Furthermore, the drive signals DOXP1 and DOXN1 are an example of a “first drive signal,” and the drive signals DOXP2 and DOXN2 are an example of a “second drive signal.”

[0036] As described above, in the semiconductor device 2 and sound reproducing device 1 of the first embodiment, the PWM signals DOP1, DON1 to DOPn, and DONn are used to cause the sound output devices 7-1 to 7-n, which have different resonant frequencies, to output sounds of different frequencies, thereby widening the overall outputtable frequency band. Furthermore, in the semiconductor device 2 and sound reproducing device 1 of the first embodiment, PWM signals DOP1, DON1 to DOPn, and DONn that are optimal for the sound output characteristics of each of the sound output devices 7-1 to 7-n can be generated based on a single sound data SD. Therefore, the semiconductor device 2 and sound reproducing device 1 of the first embodiment can cause the n sound output devices 7-1 to 7-n, each of which has a narrow outputtable frequency band, to output high-quality sound.

[0037] 1-2. Second embodiment Hereinafter, for the semiconductor device 2 and sound reproduction device 1 of the second embodiment, the same symbols will be used for configurations that are similar to those of the first embodiment, and explanations that are similar to those of the first embodiment will be omitted or simplified, with the main focus being on the differences from the first embodiment.

[0038] Fig. 7 is a diagram showing an example of the configuration of a semiconductor device 2 and a sound reproducing device 1 according to the second embodiment. As shown in Fig. 7, the sound reproducing device 1 according to the second embodiment includes a semiconductor device 2, an MCU 3, an external memory 4, n boost circuits 6-1 to 6-n, and n sound output devices 7-1 to 7-n, similar to the first embodiment. The configurations and functions of the semiconductor device 2, the MCU 3, the external memory 4, and the boost circuits 6-1 to 6-n are the same as those of the first embodiment, and therefore description thereof will be omitted.

[0039] As shown in FIG. 7, in the second embodiment, similarly to the first embodiment, the sound output devices 7-1 to 7-n each have a piezoelectric element 71 and a diaphragm 72, but the sound output devices 7-1 to 7-n are housed in a single housing 73A. The sound output device 7-i is supplied with drive signals DOXPi and DOXNi, where i is an integer between 1 and n. Taking the case where n=2 as an example, the sound output devices 7-1 and 7-2 each have the piezoelectric element 71 and the diaphragm 72 shown in FIGS. 3 and 4, but do not have a housing 73 and are housed in a single housing 73A. Drive signals DOXP1 and DOXN1 are supplied to one end and the other of the piezoelectric element 71 of the sound output device 7-1 housed in the housing 73A, respectively, and drive signals DOXP2 and DOXN2 are supplied to one end and the other of the piezoelectric element 71 of the sound output device 7-2 housed in the housing 73A, respectively.

[0040] The resonant frequency of the housing 73A may be different from the resonant frequency of any of the sound output devices 7-1 to 7-n, or may be matched to the resonant frequency of any of the sound output devices 7-1 to 7-n. In the former case, the resonant frequency of the housing 73A is matched to a frequency at which sound pressure is low in the sound output characteristics obtained by combining the sound output characteristics of the sound output devices 7-1 to 7-n, thereby outputting clear sound over a wider frequency band. In the latter case, the resonant frequency of the housing 73A is matched to a frequency at which sound pressure is low in the sound output characteristics obtained by combining the sound output characteristics of the sound output devices 7-1 to 7-n. The sound is output with the sound of the

[0041] Additionally, the semiconductor device 2 and sound reproducing device 1 of the second embodiment have the same effects as the semiconductor device 2 and sound reproducing device 1 of the first embodiment.

[0042] 1-3. Variations In the first embodiment described above, the boost circuits 6-1 to 6-n are provided outside the semiconductor device 2, but the semiconductor device 2 may include the boost circuits 6-1 to 6-n as shown in Fig. 8. Similarly, in the second embodiment described above, the boost circuits 6-1 to 6-n are provided outside the semiconductor device 2, but the semiconductor device 2 may include the boost circuits 6-1 to 6-n as shown in Fig. 9.

[0043] Furthermore, in each of the above embodiments, the PWM signal DOPi and the drive signal DOXPi are signals of opposite phase, and the PWM signal DONi and the drive signal DOXNi are signals of opposite phase, but the PWM signal DOPi and the drive signal DOXPi may be signals of the same phase, and the PWM signal DONi and the drive signal DOXNi may be signals of the same phase.

[0044] 2.Electronic equipment Fig. 10 is a functional block diagram showing a configuration example of an electronic device using the semiconductor device 2 of the first embodiment described above. Fig. 11 is a functional block diagram showing a configuration example of an electronic device using the semiconductor device 2 of the second embodiment described above. In Fig. 10, the same components as in Fig. 1 are assigned the same reference numerals. Similarly, in Fig. 11, the same components as in Fig. 7 are assigned the same reference numerals.

[0045] 10 and 11, the electronic device 100 of this embodiment includes a semiconductor device 2, an MCU 3, an external memory 4, n boost circuits 6-1 to 6-n, n sound output devices 7-1 to 7-n, a sensor 110, an operation unit 120, a storage unit 130, and a display unit 140. Note that the electronic device 100 of this embodiment may be configured such that some of the components shown in FIG. 10 or 11 are omitted or modified, or other components are added.

[0046] The external memory 4 stores various sound data such as voice data for warnings and guidance, and sound data such as melodies. The same various sound data is also stored in the internal memory 30 of the semiconductor device 2 shown in FIG.

[0047] The MCU 3 performs control processing of each unit of the electronic device 100 and various data processing. For example, the MCU 3 transmits various commands to the semiconductor device 2 to control the operation of the semiconductor device 2. The MCU 3 also performs various processes in response to detection signals from the sensor 110, various processes in response to operation signals from the operation unit 120, and processing to transmit display signals for displaying various information on the display unit 140.

[0048] The sensor 110 is, for example, an acceleration sensor, an angular velocity sensor, a speed sensor, a pressure sensor, a temperature sensor, or any other sensor, and outputs a detection signal to the MCU 3 .

[0049] The operation unit 120 is an input device configured with operation keys, button switches, etc., and outputs an operation signal to the MCU 3 in response to an operation by a user.

[0050] The storage unit 130 stores programs, data, etc. for performing various calculation processes and control processes by the MCU 3. The storage unit 130 is realized by, for example, a hard disk, a flexible disk, an MO, an MT, various types of memory, a CD-ROM, or a DVD-ROM.

[0051] The display unit 140 is a display device configured with an LCD or the like, and displays various information based on input display signals. LCD is an abbreviation for Liquid Crystal Display. The display unit 140 may be provided with a touch panel that functions as the operation unit 120.

[0052] The semiconductor device 2 generates PWM signals DOP1, DON1 to DOPn, and DONn based on various commands sent from the MCU 3 and outputs them to the boost circuits 6-1 to 6-n, respectively. The boost circuits 6-1 to 6-n boost the PWM signals DOP1, DON1 to DOPn, and DONn to generate drive signals DOXP1, DOXN1 to DOXPn, and DOXNn, respectively, and output them to the sound output devices 7-1 to 7-n, respectively. The sound output devices 7-1 to 7-n output sounds corresponding to the drive signals DOXP1, DOXN1 to DOXPn, and DOXNn, respectively.

[0053] For example, the MCU 3 may transmit a command to the semiconductor device 2 to instruct the semiconductor device 2 to play an attention-calling sound based on a detection signal from the sensor 110. Furthermore, for example, the MCU 3 may transmit a command to the semiconductor device 2 to instruct the semiconductor device 2 to play an audio guidance based on an operation signal from the operation unit 120. Furthermore, for example, the MCU 3 may transmit a command to the semiconductor device 2 to play predetermined audio or melody data at a predetermined timing. The semiconductor device 2 reads out corresponding sound data from the external memory 4 or the internal memory 30 and generates PWM signals DOP1, DON1 to DOPn, and DONn. Then, the sounds output from the sound output devices 7-1 to 7-n based on the PWM signals DOP1, DON1 to DOPn, and DONn are mixed in space to reproduce sounds such as audio or melodies containing various components in a wide frequency band.

[0054] 10 or 11, the boost circuits 6-1 to 6-n may be built into the semiconductor device 2. That is, the electronic device 100 may include the semiconductor device 2 shown in FIG. 8 or 9. Furthermore, the electronic device 100 of FIG. 11 may not include the housing 73A, and the sound generated by the vibration of the diaphragm 72 of each of the sound output devices 7-1 to 7-n may be resonated and amplified by the housing of the electronic device 100. That is, the housing of the electronic device 100 may function as a resonance box.

[0055] The electronic device 100 may be any of a variety of electronic devices, including, for example, warning devices, various household electrical appliances such as rice cookers, induction cooking heaters, vacuum cleaners, and washing machines, electronic watches, personal computers such as mobile, laptop, and tablet computers, mobile terminals such as smartphones and mobile phones, digital cameras, inkjet ejection devices such as inkjet printers, storage area network devices such as routers and switches, local area network devices, equipment for mobile terminal base stations, televisions, video cameras, video recorders, car navigation devices, real-time clock devices, pagers, electronic organizers, electronic dictionaries, calculators, electronic game devices, game controllers, word processors, workstations, videophones, security television monitors, electronic binoculars, POS terminals, medical equipment such as electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasound diagnostic devices, and electronic endoscopes, fish finders, various measuring devices, instruments for vehicles, aircraft, ships, and the like, flight simulators, head-mounted displays, motion tracing, motion tracking, motion controllers, and pedestrian autonomous navigation devices.

[0056] The present invention is not limited to the present embodiment, and various modifications are possible within the scope of the present invention.

[0057] The above-described embodiment and modifications are merely examples, and the present invention is not limited to these. For example, the embodiments and modifications can be combined as appropriate.

[0058] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects. The present invention also includes configurations that replace non-essential parts of the configurations described in the embodiments. The present invention also includes configurations that achieve the same effects or purposes as the configurations described in the embodiments. The present invention also includes configurations that add publicly known technology to the configurations described in the embodiments.

[0059] The following can be derived from the above-described embodiment and modifications.

[0060] One aspect of the semiconductor device is a sound data reading circuit for reading sound data from the memory; a first pulse width modulation signal generating circuit that generates a first pulse width modulation signal whose pulse width changes based on the sound data; a second pulse width modulation signal generating circuit that generates a second pulse width modulation signal whose pulse width changes based on the sound data; Equipped with the first pulse width modulation signal is a signal for causing a first sound output device including a first piezoelectric element and a first diaphragm to output a sound; The second pulse width modulation signal is a signal for causing a second sound output device, which includes a second piezoelectric element and a second diaphragm and has a higher resonance frequency than the first sound output device, to output sound.

[0061] In this semiconductor device, the first and second sound output devices, which have different resonant frequencies, output sounds of different frequencies using the first pulse-width modulated signal and the second pulse-width modulated signal, thereby widening the overall outputtable frequency band. Furthermore, in this semiconductor device, a first pulse-width modulated signal optimal for the sound output characteristics of the first sound output device can be generated based on a single sound data, and a second pulse-width modulated signal optimal for the sound output characteristics of the second sound output device can be generated. Therefore, this semiconductor device can cause two sound output devices with narrow outputtable frequency bands to output high-quality sound.

[0062] In one aspect of the semiconductor device, the first pulse width modulated signal is a signal whose pulse width varies and whose pulse period is constant, The second pulse width modulated signal may be a signal whose pulse width and pulse period vary.

[0063] According to this semiconductor device, it is possible to generate a second pulse width modulated signal in which high frequency noise is reduced, and therefore it is possible to cause the second sound output device to output high quality sound.

[0064] In one aspect of the semiconductor device, The second pulse width modulated signal may be a signal whose waveform is symmetrical around half a pulse period of the first pulse width modulated signal.

[0065] According to this semiconductor device, abrupt changes in the sound pressure output from the second sound output device are suppressed, and therefore harmonic distortion can be suppressed.

[0066] In one aspect of the semiconductor device, The average value of the pulse period of the second pulse-width modulated signal may be smaller than the average value of the pulse period of the first pulse-width modulated signal.

[0067] In one aspect of the semiconductor device, The voltage amplitude of the first pulse width modulated signal may be equal to the voltage amplitude of the second pulse width modulated signal.

[0068] One aspect of the semiconductor device is a first boosting circuit that boosts the first pulse width modulated signal to generate a first drive signal that drives the first sound output device; a second boosting circuit that boosts the second pulse width modulated signal to generate a second drive signal that drives the second sound output device; may also be provided.

[0069] According to this semiconductor device, the sound pressure output from the two sound output devices can be increased.

[0070] In one aspect of the semiconductor device, The first sound output device and the second sound output device may be housed in a single housing.

[0071] According to this semiconductor device, by matching the resonant frequency of the housing with a frequency at which sound pressure is low, clear sound is output over a wider frequency band, or by matching the resonant frequency of the housing with the resonant frequency of the first sound output device or the second sound output device, sound at a predetermined frequency is more emphasized.

[0072] One aspect of the electronic device is One aspect of the semiconductor device; the first sound output device; the second sound output device; Equipped with. [Explanation of symbols]

[0073] 1...sound reproduction device, 2...semiconductor device, 3...MCU, 4...external memory, 6-1 to 6-n...booster circuit, 7-1 to 7-n...sound output device, 10...control circuit, 20...sound data reading circuit, 30...memory, 40...memory interface circuit, 50-1 to 50-n...pulse width modulation signal generation circuit, 61, 62...MOSFET, 63, 64, 65...resistor, 71...piezoelectric element, 71a...first surface of piezoelectric element, 71b...second surface of piezoelectric element, 72...diaphragm, 72a...first surface of diaphragm, 72b...second surface of diaphragm, 73, 73A...housing, 73a...opening, 74, 75...wiring, 76, 77, 78...joint member, 100...electronic device, 110...sensor, 120...operation unit, 130...storage unit, 140...display unit

Claims

1. a sound data reading circuit for reading sound data from the memory; a first pulse width modulation signal generating circuit that generates a first pulse width modulation signal whose pulse width changes based on the sound data; a second pulse width modulation signal generating circuit that generates a second pulse width modulation signal whose pulse width changes based on the sound data; Equipped with the first pulse width modulation signal is a signal for causing a first sound output device including a first piezoelectric element and a first diaphragm to output a sound, The semiconductor device, wherein the second pulse width modulation signal is a signal for causing a second sound output device, which includes a second piezoelectric element and a second diaphragm and has a higher resonance frequency than the first sound output device, to output sound.

2. In claim 1, the first pulse width modulated signal is a signal whose pulse width varies and whose pulse period is constant, The second pulse width modulation signal is a signal whose pulse width and pulse period change.

3. In claim 1, The semiconductor device, wherein the second pulse width modulated signal is a signal whose waveform is symmetrical around a half period of the pulse period of the first pulse width modulated signal.

4. In claim 1, The semiconductor device, wherein an average value of the pulse period of the second pulse-width modulated signal is smaller than an average value of the pulse period of the first pulse-width modulated signal.

5. In claim 1, The voltage amplitude of the first pulse width modulation signal is equal to the voltage amplitude of the second pulse width modulation signal.

6. In claim 1, a first boosting circuit that boosts the first pulse width modulated signal to generate a first drive signal that drives the first sound output device; a second boosting circuit that boosts the second pulse width modulated signal to generate a second drive signal that drives the second sound output device; A semiconductor device comprising:

7. In claim 1, The semiconductor device, wherein the first sound output device and the second sound output device are housed in a single housing.

8. A semiconductor device according to any one of claims 1 to 7, the first sound output device; the second sound output device; An electronic device comprising:

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