Electronic device, method, and program

Abstract

To prevent a product from being shut down by an adapter overcurrent protection function while preventing a speaker from being damaged due to the flow of a large current.SOLUTION: The electronic device includes a current detection circuit that detects a current supplied from the adapter, and a processing unit that processes a signal. When a current equal to or greater than a first threshold value from the current detection circuit is continuously detected for a first time, the processing unit clips the signal and outputs a clipped signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electronic device, a method, and a program. [Background technology]

[0002] An overcurrent protection circuit built into an adapter can stop the power supply, causing the electronic device to shut down. For example, Patent Document 1 describes a specific configuration of this type of electronic device. The electronic device described in Patent Document 1 stops the power supply on the line when a large current is supplied from the power supply to the amplifier. This prevents the adapter's overcurrent protection circuit from activating even when the amplifier is overpowered, preventing a sudden shutdown. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-286546 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration described in Patent Document 1, the power supply to the amplifier is stopped, which causes problems such as interruption of the sound output from the speaker.

[0005] In view of the above circumstances, an embodiment of the present disclosure aims to provide an electronic device, method, and program suitable for preventing product shutdown due to an adapter overcurrent protection function while preventing damage to speakers due to large current flow. [Means for solving the problem]

[0006] An electronic device according to an embodiment of the present disclosure includes a current detection circuit that detects a current supplied from an adapter, and a processing unit that processes a signal. When the processing unit detects a current equal to or greater than a first threshold from the current detection circuit for a first period of time, the processing unit clips the signal and outputs the clipped signal. [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, an electronic device, method, and program are provided that are suitable for preventing a product shutdown due to an adapter overcurrent protection function while preventing damage to speakers due to a large current flow. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram illustrating a schematic configuration of an electronic musical instrument according to an embodiment of the present disclosure. [Figure 2] 10 is a graph showing an example of the operation of a clipper in an electronic musical instrument according to an embodiment of the present disclosure. [Figure 3] 1 is a block diagram illustrating a configuration of an electronic musical instrument according to an embodiment of the present disclosure. [Figure 4] 10 is a flowchart of a clip process executed by an electronic musical instrument according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a diagram supplementing the explanation of the flowchart shown in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following description relates to an electronic device, a method, and a program according to an embodiment of the present disclosure. Common or corresponding elements are denoted by the same or similar reference numerals, and redundant descriptions will be appropriately simplified or omitted.

[0010] The electronic musical instrument 1 shown in Fig. 1 is an example of an electronic device and also an example of a computer. The electronic musical instrument 1 is, for example, an electronic piano. The electronic musical instrument 1 may be an electronic keyboard instrument other than an electronic piano (for example, an electronic keyboard), or may be another type of electronic musical instrument, such as an electronic percussion instrument, an electronic wind instrument, or an electronic string instrument.

[0011] The electronic musical instrument 1 operates on power supplied from an AC adapter 2. The AC adapter 2 has a built-in overcurrent protection circuit. When the AC adapter 2 outputs a current equal to or greater than a specified value (e.g., 2.6 A) for a specified period of time (e.g., 70 ms), the overcurrent protection circuit is activated. This causes the AC adapter 2 to stop supplying power to the electronic musical instrument 1. Note that the various numerical values ​​shown in this embodiment are merely examples, and are determined based on, for example, product specifications and design concepts. These numerical values ​​can be changed as appropriate.

[0012] As shown schematically in FIG. 1, the electronic musical instrument 1 includes a current sense amplifier 10, a peak hold circuit 20, a sound source LSI (Large Scale Integration) 30, a class D amplifier 40, and a speaker SP.

[0013] The current sense amplifier 10 is installed on a power supply path from the AC adapter 2 to the class-D amplifier 40. The current sense amplifier 10 measures a drop voltage across a shunt resistor as a value indicating the current consumption of the class-D amplifier 40. In other words, the current sense amplifier 10 is an example of a current detection circuit that detects the current supplied from the AC adapter 2.

[0014] The peak hold circuit 20 detects the peak value of the value measured by the current sense amplifier 10. Specifically, the peak hold circuit 20 holds the peak value of the drop voltage that indicates the current consumption in the class-D amplifier 40, and outputs this peak value to the ADIN terminal of the sound source LSI 30. The peak hold circuit 20 is included in a current detection circuit that detects the current supplied from the AC adapter 2.

[0015] The tone generator LSI 30 obtains, from the peak value input to the ADIN terminal, a value indicating the current consumption in the class-D amplifier 40. This value indicating the current consumption is an example of a value indicating the power supplied to the amplifier unit.

[0016] The sound source LSI 30 includes a media player and sound source module (not shown). The media player has built-in codecs compatible with various formats. The media player can play audio data in various formats. The played audio data is amplified by a class D amplifier 40 and output from a speaker SP. The audio data may be built into the electronic musical instrument 1, or may be input from an external device connected via a wired or wireless connection.

[0017] The tone generator module may include a DSP 34. In this case, the tone generator module processes, for example, various events (such as note-on, auto-off, and control change) in response to performance operations on the electronic musical instrument 1 or MIDI (Musical Instrument Digital Interface) data input from an external device. When a note-on event in response to a key press is input, for example, the tone generator module reads out the corresponding waveform data. The tone generator module generates digital musical sound data (such as I 2 The musical sound signal generated by the tone generator module is converted into an analog signal, amplified by a class D amplifier 40, and output from a speaker SP.

[0018] In the following, for convenience of explanation, audio data played back by a media player and digital musical sound data generated by a sound source module may be collectively referred to as "musical sound signals."

[0019] The tone generator LSI 30 includes a clipper CL for preventing circuit damage (e.g., damage to the speaker SP) when a large current flows through the electronic musical instrument 1. The clipper CL and other functional blocks within the tone generator LSI 30 are implemented, for example, by software programs. Some of the functional blocks of the tone generator LSI 30 may also be implemented by hardware such as dedicated logic circuits.

[0020] In an electronic piano, for example, there are cases where a high-level attack sound is produced momentarily, where multiple musical tones corresponding to multiple key presses are produced simultaneously at high volume, or where audio data recorded at a high level is played back, and in these cases, a large current flows, which can cause problems such as damage to the speaker SP.

[0021] If the clipper CL is turned on to clip the peaks of the musical signal to prevent damage to the speaker SP due to a large current, the musical signal will be distorted and the sound quality of the output sound from the speaker SP will deteriorate. In this case, for example, the tone of a piano cannot be reproduced well. From the viewpoint of preventing deterioration in sound quality, clipping of the musical signal should be avoided. From the viewpoint of protecting the speaker SP, clipping of high-level musical signal is necessary. It is desirable to prevent deterioration in sound quality while protecting the speaker SP.

[0022] Therefore, when the current sense amplifier 10 detects a current equal to or greater than the first threshold for a first continuous period of time, the tone generator LSI 30 according to this embodiment turns on the clipper CL to clip the musical sound signal, and outputs the clipped musical sound signal to the class-D amplifier 40. In other words, the tone generator LSI 30 does not clip the musical sound signal until the current sense amplifier 10 detects a current equal to or greater than the first threshold for a first continuous period of time. In other words, the tone generator LSI 30 does not clip the musical sound signal until the activation condition of the overcurrent protection circuit of the AC adapter 2 is satisfied (i.e., while it is guaranteed that no circuit damage or the like will occur). Therefore, for example, an attack sound with a momentary high level is not clipped. Even when multiple musical sounds are instantaneously generated at a high volume, the clipper CL is not turned on, and the musical sounds are not clipped. For example, even in a song with strong intonation, the tone of a piano can be reproduced with high quality and excellent sound. The tone is not limited to a piano tone.

[0023] The first threshold is, for example, 2.5 A. The first time period is, for example, 50 ms. Therefore, before the activation condition of the overcurrent protection circuit of the AC adapter 2 is satisfied, the clipper CL turns on and the musical tone signal is clipped. This prevents damage to the speaker SP and also prevents a sudden shutdown of the electronic musical instrument 1 due to the activation of the overcurrent protection circuit of the AC adapter 2.

[0024] One possible method is to prevent damage to the speaker SP by lowering the gain of the class-D amplifier 40 when a large current is detected. However, if this method is adopted, the volume will drop suddenly when a large current is detected and the gain is lowered. This may result in, for example, the performance sound sounding unnatural to the ear. In contrast, in this embodiment, the gain of the class-D amplifier 40 is not lowered even when a large current is detected. Therefore, a sudden drop in volume due to the gain being lowered does not occur. Since the sense of volume is maintained even when a large current is detected, the performance sound does not sound unnatural.

[0025] In an electronic piano, it is rare for the performance sound to continue at a high volume. Therefore, it is rare for the activation condition of the clipper CL (current equal to or greater than the first threshold value continuing for a first period of time) to be met. However, there is a possibility that the performance sound will continue at a high volume, for example, when playing the electronic musical instrument 1 while playing audio data input from an external device through the speaker SP of the electronic musical instrument 1. Therefore, in this embodiment, degradation of sound quality is substantially avoided while damage to the speaker SP is also prevented when playing the electronic piano.

[0026] It should be noted that any reference to an element using a designation such as "first," "second," etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations are used for convenience to distinguish between two or more elements. Thus, reference to a first and a second element does not imply, for example, that only two elements are employed, that the first element must precede the second element, etc.

[0027] An example of the operation of the clipper CL will be explained using the graph in Figure 2. The vertical axis of Figure 2 represents the current (unit: A) detected using the current sense amplifier 10. The horizontal axis of Figure 2 represents time (unit: ms). The scale of the time axis has been changed as appropriate. For example, the 50 ms from time T1 to time T2 is shown as long in the figure, while the 300 ms from time T3 to time T4 and the 1000 ms from time T5 to time T6 are shown as short in the figure. In Figure 2, the "clipper operation period PD" represents the period from when the clipper CL is turned on to when it is turned off.

[0028] In the example of Fig. 2, at time T2, a current of 2.5 A (an example of a first threshold) or more is detected continuously for 50 ms (an example of a first time period). Therefore, at time T2, the clipper CL is turned on and the musical sound signal is clipped. The clip value is, for example, -9.28 dB. One advantage of clipping the musical sound signal is that it prevents damage to the speaker SP.

[0029] It is conceivable to immediately turn off the clipper CL when the current drops. Here, for example, when playing a fast piece of music with large changes in intonation, the current detected by the current sense amplifier 10 may fluctuate significantly. In this case, there is a risk that the clipper CL will be turned on and off frequently in accordance with the fluctuations in the current. This will cause noticeable switching noise due to the frequent on / off of the clipper CL. Switching noise is an abnormal sound that occurs when a distorted sound caused by clipping the musical sound signal alternates with a state in which the musical sound signal is not clipped (a state in which there is no distortion due to clipping).

[0030] Therefore, the tone generator LSI 30 according to this embodiment releases clipping of the musical sound signal (turns off the clipper CL) when the current sense amplifier 10 detects a current equal to or less than the second threshold for a second consecutive time while the musical sound signal is being clipped. The second threshold is lower than the first threshold, e.g., 1.5 A. The second time is longer than the first time, e.g., 1000 ms. Therefore, for example, during the 300 ms period from time T3 to time T4, the clipper CL is not turned off even though the current momentarily falls below 1.5 A (an example of the second threshold).

[0031] At time T6, the clipper CL is turned off only when a current of 1.5 A (an example of the second threshold) or less is detected continuously for 1000 ms (an example of the second time period). By setting the clip release condition in this way, it is possible to prevent the clipper CL from being turned on and off frequently, thereby suppressing, for example, the occurrence of clip noise. Additionally, it is desirable to set the second time period longer than the first time period in order to prevent the clipper CL from being turned on and off frequently.

[0032] The specific configuration of the electronic musical instrument 1 will be described with reference to Fig. 3. As shown in Fig. 3, the electronic musical instrument 1 includes a current sense amplifier 10, a peak hold circuit 20, a tone generator LSI 30, a class-D amplifier 40, a power supply circuit 50, a RAM (Random Access Memory) 52, a flash ROM (Read Only Memory) 54, a keyboard 60, a key scanner 62, an LCD (Liquid Crystal Display) 64, an LCD controller 66, a control 68, a USB (Universal Serial Bus) interface 70, an external input interface 72, an external output interface 74, and a speaker SP.

[0033] The power supply circuit 50 generates power to be supplied to each part of the electronic musical instrument 1 from the power supplied by the AC adapter 2, and supplies the generated power to each part.

[0034] The tone generator LSI 30 is an example of a processing unit that processes signals. More specifically, the tone generator LSI 30 includes a CPU (Central Processing Unit) 32 that controls each unit of the electronic musical instrument 1, and a DSP (Digital Signal Processor) 34 that is an example of a processing unit. The CPU 32 reads out programs and data stored in a flash ROM 54 and uses the RAM 52 as a work area to comprehensively control the electronic musical instrument 1. The CPU 32 controls parameter settings such as volume, for example, in the I / O. 2 It also processes the signal by outputting it to the class D amplifier 40 in C format.

[0035] The RAM 52 temporarily stores data and programs, and stores programs and data (such as waveform data) read from the flash ROM 54, as well as other data required for communication.

[0036] The flash ROM 54 is a non-volatile semiconductor memory such as a flash memory, an EPROM (Erasable Programmable ROM), or an EEPROM (Electrically Erasable Programmable ROM).

[0037] The keyboard 60 has a plurality of white keys and black keys as performance controls. Each key is associated with a different pitch. The electronic musical instrument 1 produces musical tones in response to the depression of the keys on the keyboard 60.

[0038] The key scanner 62 monitors key presses and key releases on the keyboard 60. For example, when the key scanner 62 detects a key press by the user, it outputs a key press event to the sound source LSI 30. The key press event includes information about the pitch of the key related to the key press (key number). The key number is also called a key number, MIDI key, or note number.

[0039] In this embodiment, a separate means is provided for measuring the key pressing speed (velocity), and the velocity measured by this means is also included in the key pressing event. For example, multiple contact switches are provided for each key. The velocity is measured based on the difference in the time that each contact switch remains conductive when the key is pressed. Velocity can be considered a value that indicates the strength of the key pressing operation, and also a value that indicates the loudness (volume) of the musical sound.

[0040] The LCD 64 is driven by an LCD controller 66. When the LCD controller 66 drives the LCD 64 in accordance with a control signal from the CPU 32, a screen corresponding to the control signal is displayed on the LCD 64. The LCD 64 may be replaced with a display device such as an organic EL (Electro Luminescence) display.

[0041] The controls 68 include various controls for operating the electronic musical instrument 1, such as knobs (such as a main volume knob), buttons, and pedals. The USB interface 70 is, for example, an interface for transmitting and receiving MIDI data (MIDI messages) to and from an external MIDI device. The external input interface 72 is, for example, an audio interface to which an external device such as a microphone is connected. The external output interface 74 is, for example, an audio interface to which an external device such as a speaker with a built-in amplifier or headphones is connected.

[0042] FIG. 3 shows only one example of the configuration of the electronic musical instrument 1. For example, the speaker SP may be external. The electronic musical instrument 1 may also include other elements not shown in FIG. 3 (for example, a switch panel, a touch device, etc.). The electronic musical instrument 1 may also be configured without including some of the elements shown in FIG. 3. In this way, there is a degree of freedom in the design of the configuration of the electronic musical instrument 1, and various embodiments are possible.

[0043] The clipping process for musical tone signals will be described with reference to Figures 4 and 5. The flowchart shown in Figure 4 is executed by the DSP 34, which is an example of a processing unit, at a predetermined cycle (for example, 22.6 μs cycle) from when the system of the electronic musical instrument 1 is started until it is stopped.

[0044] The steps of the flowcharts shown in the embodiments of the present disclosure may be reordered to the extent that they are consistent. For example, although the processes of various steps are presented in an exemplary order in the embodiments of the present disclosure, they are not limited to the presented order. Furthermore, the steps of the flowcharts shown in the embodiments of the present disclosure may be performed in parallel or in a concurrent manner to the extent that they are consistent.

[0045] 4, the DSP 34 acquires a current value a (step S101). For example, the DSP 34 converts the peak value input from the peak hold circuit 20 to the ADIN terminal T11 from an analog signal to a digital signal at a predetermined sampling rate, and acquires the average value every n cycles (e.g., every four samplings) as a value (current value a) indicating the current consumption of the class-D amplifier 40 (step S101). The number of samples used to calculate the average value is set appropriately, for example, taking into consideration suppression of variations in peak values ​​and delays associated with calculating the average value.

[0046] The DSP34 determines whether the current value a is equal to or less than a second threshold value (e.g., 1.5 A) (step S102). Here, the DSP34 includes a first counter and a second counter. The first counter is a counter used to determine whether an activation condition of the clipper CL is satisfied. The second counter is a counter used to determine whether a deactivation condition of the clipper CL is satisfied. If the current value a is equal to or less than the second threshold value (step S102: YES), the DSP34 counts up the second counter (step S103).

[0047] The DSP 34 determines whether the current value a equal to or less than the second threshold has continued for a second time (e.g., 1000 ms) (step S104). Specifically, the DSP 34 determines whether the count value of the second counter has reached a value corresponding to the second time. If the current value a equal to or less than the second threshold has continued for the second time (step S104: YES), the DSP 34 turns off the clipper CL (step S105) and ends this flowchart. If the clipper CL is already in the off state, the process of step S105 is not executed and this flowchart ends.

[0048] If the current value a is not equal to or less than the second threshold value for the second time period (step S104: NO), the DSP 34 proceeds to step S107. If the current value a exceeds the second threshold value (step S102: NO), the DSP 34 resets the second counter to zero (step S106) and proceeds to step S107.

[0049] The DSP 34 does not release the clipping of the musical sound signal until the current value a equal to or less than the second threshold value is detected for the second consecutive time. This prevents the clipper CL from being turned on and off frequently, thereby suppressing, for example, the occurrence of clipping noise. It also prevents the clipper CL from being turned on and off frequently due to hunting or the like.

[0050] The DSP 34 determines whether the current value a is equal to or greater than a first threshold value (for example, 2.5 A) (step S107). If the current value a is equal to or greater than the first threshold value (step S107: YES), the DSP 34 counts up the first counter (step S108).

[0051] The DSP34 determines whether the current value a equal to or greater than the first threshold has continued for a first time period (e.g., 50 ms) (step S109). Specifically, the DSP34 determines whether the count value of the first counter has reached a value corresponding to the first time period. If the current value a equal to or greater than the first threshold has continued for the first time period (step S109: YES), the DSP34 turns on the clipper CL (step S110) and ends this flowchart. If the clipper CL is already on, the process of step S110 is not executed and this flowchart ends.

[0052] If the current value a is not equal to or greater than the first threshold value for the first time period (step S109: NO), the DSP 34 ends this flowchart without executing the process of step S110. If the current value a is less than the first threshold value (step S107: NO), the DSP 34 resets the first counter to zero (step S111) and ends this flowchart.

[0053] The explanation of the flowchart in FIG. 4 will be supplemented with FIG. 5. In FIG. 5, the results of the processing in FIG. 4, which is executed at a cycle of 22.6 μs, are arranged on the time axis. In FIG. 5, a black circle indicates that a current value a equal to or greater than the first threshold value (2.5 A) was detected during the cycle processing. A white circle indicates that a current value a less than the first threshold value was detected during the cycle processing. In the former case, a value of 1 is obtained as the judgment result, and in the latter case, a value of 0 is obtained as the judgment result.

[0054] In the example shown in FIG. 5, at time point 11, when the current value a remains at or above 2.5 A for 50 ms (in other words, the judgment result of value 1 continues for 50 ms), the clipper CL is turned on and the musical tone signal is clipped at a clip value of −9.28 dB. This prevents damage to the speaker SP, for example. The musical tone signal is not clipped until time point T11 is reached (for example, until the activation condition of the overcurrent protection circuit of the AC adapter 2 is immediately met). This allows, for example, momentarily high-level attack sounds and multiple momentarily loud musical tones to be reproduced with high quality and without distortion. For example, even in songs with strong intonation, the piano tone can be reproduced with high quality and excellent reproduction.

[0055] For example, in a configuration in which the CPU 32 determines whether the clipper CL is on or off, there is a risk that the overcurrent protection circuit of the AC adapter 2 will activate first due to the time lag between the on determination and the clipper CL being turned on by the DSP 34. In contrast, in this embodiment, the peak value input to the ADIN terminal is input directly to the DSP 34 without going through the CPU 32, and the on / off determination of the clipper CL is performed in real time by the DSP 34. By having the DSP 34 directly determine whether the clipper CL is on or off, the time lag is reduced. The clipper CL is turned on before the overcurrent protection circuit of the AC adapter 2 activates, preventing damage to the speaker SP.

[0056] In this embodiment, since the clipping function is implemented in the DSP 34, there is no need to provide a clipping circuit in other circuits such as the class-D amplifier 40. This makes it suitable for configuring the electronic musical instrument 1 using more general-purpose electronic components.

[0057] The above is a description of exemplary embodiments of the present disclosure. The embodiments of the present disclosure are not limited to those described above, and various modifications are possible within the scope of the technical idea of ​​the present disclosure. For example, the embodiments of the present application also include appropriate combinations of embodiments explicitly shown in the specification or obvious embodiments.

[0058] In the above embodiment, the musical tone signal is clipped in the electronic musical instrument 1 to protect the speaker SP, but in another embodiment, the signal may be clipped to protect the circuit in an electronic device other than the electronic musical instrument 1. Also, in the above embodiment, the on / off state of the clipper CL is determined by detecting the current supplied from the AC adapter 2. In another embodiment, the on / off state of the clipper CL may be determined by detecting the current supplied from another type of power supply device, such as USB-PD. In other words, the configuration according to the present disclosure is not limited to the AC adapter 2, and can also be applied to preventing large currents in other types of power supply devices. [Explanation of symbols]

[0059] 1: Electronic musical instrument, 2: AC adapter, 10: Current sense amplifier, 20: Peak hold circuit, 30: Sound source LSI, 32: CPU, 34: DSP, 40: Class D amplifier, 50: Power supply circuit, CL: Clipper, SP: Speaker, T11: ADIN terminal

Claims

1. a current detection circuit that detects a current supplied from the adapter; a processing unit that processes a signal, The processing unit clipping the signal when the current detected by the current detection circuit is greater than or equal to a first threshold value for a first period of time; Outputs the clipped signal. electronic equipment.

2. The processing unit and releasing the clipping of the signal when the current detected from the current detection circuit is equal to or less than a second threshold value that is lower than the first threshold value for a second period of time during the period in which the signal is clipped. The electronic device according to claim 1 .

3. The second time period is longer than the first time period. The electronic device according to claim 2 .

4. The processing unit is a DSP (Digital Signal Processor) that processes the signal. The electronic device according to claim 1 .

5. The DSP outputs the clipped signal to an amplifier.

5. The electronic device according to claim 4.

6. the current detection circuit includes a peak hold circuit; The output from the peak hold circuit is input to the DSP, the DSP determines whether the current equal to or greater than the first threshold continues for the first period of time; 5. The electronic device according to claim 4.

7. An electronic device comprising a current detection circuit that detects a current supplied from an adapter and a processing unit that processes a signal, clipping the signal when the current detected by the current detection circuit is greater than or equal to a first threshold value for a first period of time; Outputs the clipped signal. Execute the process, method.

8. An electronic device comprising a current detection circuit that detects a current supplied from an adapter and a processing unit that processes a signal, clipping the signal when the current detected by the current detection circuit is greater than or equal to a first threshold value for a first period of time; Outputs the clipped signal. Execute the process, program.

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