Information processing device and control method

Abstract

To adjust an output level of a voice signal according to impedance of a sound source.SOLUTION: An information processing device includes a controller and an audio system. The controller measures an output level of a test signal to be output to a sound source when detecting connection between the audio system and the sound source, and determines an output gain of a sound signal to be output from the audio system to the sound source based on the output level. An embodiment of the present application may be implemented as an information processing device or a control method.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] This application relates to an information processing apparatus and a control method, for example, control of the output level of an audio signal.

Background Art

[0002] An information processing apparatus such as a PC (Personal Computer) or a smartphone generally acquires content desired by a user using a network and makes it possible to present the acquired content. The acquired content may include audio. When presenting audio in a public place, the presented audio may propagate to the surroundings and cause discomfort to others. To avoid this, a wearable sound source such as headphones or earphones may be used when playing audio.

[0003] On the other hand, various sound sources have been popularized conventionally. The impedance varies greatly depending on the model of the sound source. For example, the average impedance of headphones is about 30 to 40 Ω, but headphones having a high impedance exceeding 100 Ω are also popular. Such differences in impedance affect the output level of the audio signal provided by the information processing apparatus. For example, even when connected to the same information processing apparatus, the higher the impedance of the headphones, the more likely the output level of the audio signal is to decrease. When the sound source serving as the audio output destination is switched, an audio playback device that enables volume adjustment has been proposed.

[0004] For example, the audio playback device described in Patent Document 1 includes a built-in speaker, an external output means capable of connecting an external audio output device, a volume operation means for a user to operate the volume of the audio signal, a volume adjustment means for adjusting the volume of the audio signal according to the user operation of the volume operation means, and when an external audio device is connected to the external output means, switching the output destination of the audio signal to the external output means, and when no external audio output device is connected to the external output means, switching to the built-in speaker, and performing different volume controls according to the output destination of the audio signal.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the audio playback device described in Patent Document 1, depending on whether an audio output device is connected to the external output means, volume adjustment is performed according to whether the output destination of the audio signal is switched to either the external output means or the built-in speaker. In volume adjustment, the acquired audio signal is amplified at an amplification rate corresponding to the volume value input by the user operation. However, it has not been fully considered that the impedance of the audio output device connected to the external output means is diverse.

Means for Solving the Problems

[0007] This application has been made to solve the above problems, and an information processing apparatus according to one aspect of this application includes a controller and an audio system. When the controller detects the connection between the audio system and the sound source, the controller measures the output level of the test signal output to the sound source, and determines the output gain of the audio signal output from the audio system to the sound source based on the output level.

[0008] In the above information processing apparatus, the controller may determine the output gain based on the impedance of the sound source corresponding to the output level, the rated power consumption of the sound source, and the internal resistance of the audio system.

[0009] In the above information processing apparatus, the controller may determine the maximum voltage of the audio signal based on the impedance of the sound source, the maximum power consumption of the sound source, and the internal resistance.

[0010] In the information processing apparatus described above, the test signal may have a frequency component higher than the audible band.

[0011] The information processing apparatus includes a rectifying element that rectifies the test signal and outputs a rectified signal, and a low-pass filter that extracts a low-pass signal from the rectified signal. The controller may measure the output level of the low-pass signal.

[0012] In the information processing apparatus described above, the low-pass filter includes a resistance element and a storage element in parallel with the controller. The controller detects the output level after a lapse of a predetermined time from the output of the test signal, and the predetermined time may be longer than the product of the resistance value of the resistance element and the capacitance of the storage element.

[0013] A control method according to another aspect of the present application is a control method for an information processing apparatus including a controller and an audio system. When the controller detects a connection between the audio system and a sound source, the controller measures an output level of a test signal output to the sound source, and determines an output gain of an audio signal output from the audio system to the sound source based on the output level.

Advantages of the Invention

[0014] According to the embodiment of the present application, the output level of the audio signal can be adjusted according to the impedance of the sound source.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present application will be described with reference to the drawings. First, an overview of the information processing apparatus 1 according to this embodiment will be described. FIG. 1 is a perspective view showing an example of the external configuration of the information processing apparatus 1 according to this embodiment. In the example of FIG. 1, the information processing apparatus 1 is configured as a notebook personal computer (notebook PC: Personal Computer).

[0017] The information processing apparatus 1 includes a first housing 101 and a second housing 105, which are coupled using hinge mechanisms 121a and 121b. The hinge mechanisms 121a and 121b are fixed to one side of the first housing 101 and the second housing 105, respectively. One of the first housing 101 and the second housing 105 is rotatable relative to the other with one side of the first housing 101 and the second housing 105 as a rotation axis. That is, the angle θ (referred to as the "opening angle" in this application) formed between the main surface of the first housing 101 and the main surface of the second housing 105 is variable.

[0018] On the main surface of the first housing 101, a display 103 is arranged, occupying most of it. On the main surface of the second housing 105, a keyboard 107, a touchpad 109, and a power button 113 are arranged. With such an arrangement, the information processing apparatus 1 is used with the first housing 101 and the second housing 105 open. The open state means a state in which one of the main surface of the first housing 101 and the main surface of the second housing 105 is open without being shielded by the other. In the open state, the opening angle θ is typically in the range of 90° to 180°.

[0019] On the side surface of the second housing 105, an audio terminal 124a is installed. The audio terminal 124a is detachably connected to the input / output terminal of the audio device by an external force. The audio terminal 124a has a shape that can be fitted to the input / output terminal of the audio device, and in a state where it is fitted to the input / output terminal, the audio signal of the information processing apparatus 1 can be input / output. In the example of FIG. 1, the audio terminal 124a has an audio jack. The audio device is a headphone 44h and is provided with an audio plug as an input / output terminal. The audio plug is inserted into the cavity of the audio terminal 124a, and an audio signal is input / output between the audio plug and the audio terminal 124a.

[0020] The audio device includes a sound source 44 (FIG. 2). The sound source 44 generates sound according to the audio signal input to itself. The sound source 44 includes an electroacoustic transducer (for example, a speaker) that generates mechanical vibration according to an audio signal that is an electrical signal. The audio device may include a sound receiving element (for example, a microphone) that receives sound arriving at itself. The audio device may include the sound receiving element separately from the sound source 44, or the sound receiving element may be shared as the sound source 44. The sound source 44 may be one, or two or more. The sound source 44 may be configured as a wearable device that is worn in contact with or close to each ear. As the sound source 44 wearable on the human body, headphones 44h and earphones are typical.

[0021] Generally, the electrical impedance of the sound source 44 (which may be simply referred to as "impedance" in this application) varies greatly depending on the model. When an audio signal is output to the sound source, the output level of the audio signal provided to the sound source differs according to the impedance. The higher the impedance of the sound source 44, the more likely the output level of the audio signal from the signal source is to decrease. As will be described later, when the information processing apparatus 1 detects the connection to the sound source, it measures the impedance of the sound source 44. The information processing apparatus 1 determines that the higher the measured impedance, the higher the output level of the audio signal. This reduces the volume difference between models regardless of the impedance of the sound source 44.

[0022] Next, a hardware configuration example of the information processing apparatus 1 according to the present embodiment will be described. FIG. 2 is a schematic block diagram showing a hardware configuration example of the information processing apparatus 1 according to the present embodiment. The information processing apparatus 1 includes a CPU 11, a main memory 12, a GPU (Graphic Processing Unit) 13, a display 103, a PCH (Platform Controller Hub) 21, a BIOS (Basic Input Output System) memory 22, an auxiliary storage device 23, a USB (Universal Serial Bus) connector 24, a WLAN (Wireless Local Area Network) card 25, an audio system 26, an EC (Embedded Controller) 31, an input device 32, a power supply circuit 33, a battery 34, and a processing circuit 36.

[0023] The CPU 11 is a processor that forms the core of the system devices provided in the information processing apparatus 1. The CPU 11 is a processor capable of executing various arithmetic processes instructed by instructions described in various programs. The CPU 11 executes processes instructed by various programs such as, for example, an OS (Operating System), BIOS, firmware, and application programs (referred to as "apps" in this application). The CPU 11 executes the OS and provides functions such as resource management, execution management of various programs, input / output control, and file management in the computer system that forms the core of the information processing apparatus 1, i.e., the host system. Note that executing the processing instructed by the instructions (commands) described in a program may be referred to as "executing the program" or "running the program."

[0024] The main memory 12 is a writable memory that is used as a loading area for the execution program of the processor or as a working area for writing the processing data of the execution program. The main memory 12 is composed of, for example, a plurality of DRAM (Dynamic Random Access Memory) chips. The execution program includes the OS, various drivers for operating hardware such as peripheral devices, various services / utilities, applications, etc.

[0025] The GPU 13 is a processor that mainly executes real-time image processing. The GPU 13 processes the drawing commands from the CPU 11 and writes the drawing information obtained by the processing into a video memory (not shown). The GPU 13 reads the drawing information from the video memory and outputs it as display data showing the drawing information to the display 103 via the CPU 11 (image processing). The drawing information notified to the display 103 constitutes the display screen.

[0026] The CPU 11 executes the graphics driver on the OS to control the operation of the GPU 13 and realizes the image processing instructed by the OS, applications, and other programs. The number of GPUs 13 is not limited to one and may be a plurality. The GPU 13 may share some processing with the CPU 11 and execute parallel arithmetic processing other than image processing. The CPU 11, the main memory 12, and the PCH 21 form the computer system that is the core of the information processing apparatus 1, i.e., the host system. In other words, the computer system of the information processing apparatus 1 is configured to include system devices as hardware and software such as the OS, schedule tasks, etc.

[0027] The display 103 displays a display screen based on the display data output from the CPU 11. The display 103 may be, for example, any of a liquid crystal display (LCD), an OLED (Organic Light Emitting Diode) display, and the like.

[0028] The PCH 21 includes one or more bus controllers and enables connection so that various data can be input and output with a plurality of devices. The bus controller may be, for example, any one of USB, Serial ATA (Advanced Technology Attachment), SPI (Serial Peripheral Interface) bus, PCI (Peripheral Component Interconnect) bus, PCI-Express bus, and LPC (Low Pin Count), or any combination thereof. The plurality of devices to be connected include, for example, the BIOS memory 22, the auxiliary storage device 23, the USB connector 24, the WLAN card 25, the audio system 26, and the EC 31.

[0029] The BIOS memory 22 stores firmware for controlling the operations of the BIOS, the EC 31, and other devices. The BIOS is firmware for performing basic input / output of system devices. In the present application, the BIOS may also include firmware defined according to the specifications defined in the UEFI (Unified Extensible Firmware Interface). The BIOS memory 22 is configured to include an electrically rewritable non-volatile memory. As such a non-volatile memory, for example, an EEPROM (Electrically Erasable Programmable Read Only Memory) and a flash ROM (Read Only Memory) can be used.

[0030] The auxiliary storage device 23 continuously stores various data. The data to be stored includes various programs, parameters, data used for various processes, and data acquired by various processes that can be executed by the CPU 11 and the GPU 13. The auxiliary storage device 23 may be, for example, either an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The auxiliary storage device 23 is configured to include various non-volatile memories. For example, flash memory is used as the non-volatile memory. The various programs may include, for example, any one of an OS, a driver, firmware, an app, etc., or any combination thereof.

[0031] The USB connector 24 is a connector for connecting various peripheral devices using USB. The WLAN card 25 can connect to a wireless (Wi-Fi) LAN or another network via a wireless LAN to wirelessly transmit and receive various data to and from devices at the connection destination.

[0032] The audio system 26 can execute the acquisition, recording, playback, and output of audio data under the control of the host system. The audio system 26 converts, for example, an analog audio signal input from a microphone (not shown) connected to itself into digital audio data (AD (Analog-to-digital) conversion). The audio system 26 reads out audio data specified from a storage medium in which the audio data has been previously stored. The audio system 26 acquires audio data specified from other devices. The storage medium serving as the acquisition source of the audio data may be a storage medium provided in the audio system 26, an auxiliary storage device 23, or another device. The audio system 26 stores the acquired audio data in a storage medium. The audio system 26 converts the acquired digital audio data into an analog audio signal (DA (Digital-to-Analog) conversion). When presenting audio, the audio system 26 outputs the converted analog audio signal to the sound source 44. The audio terminal 124a (FIG. 1) may be installed in the audio system 26.

[0033] The processing of the audio system 26, namely, acquisition, recording, playback, and output, is directed by instructions described in an application executed by the host system or other programs. The audio system 26 may include one or both of an encoder (coder) that encodes the acquired audio data using a predetermined audio encoding method and a decoder that decodes the acquired digital audio data using a predetermined audio decoding method. The encoder and the decoder may be configured as an integrated single codec. Note that the information processing apparatus 1 may have a built-in microphone and speaker (not shown), or they may be separate. The built-in speaker may also be selected by a user operation as one of the sound sources 44.

[0034] EC31 is a one-chip microcomputer that monitors and controls the status of various devices (peripheral devices, sensors, etc.) regardless of the operating state of the host system that forms the core of the information processing apparatus 1. EC31 includes a processor separate from CPU11, a RAM separate from main memory 12, as well as a ROM, multiple channels of A / D (Analog-to-Digital) input terminals, D / A (Digital-to-Analog) output terminals, a timer, and an input / output interface (not shown). EC31 executes a predetermined firmware to perform its functions.

[0035] An input device 32, a power supply circuit 33, a processing circuit 36, and other devices are wired-connected to the input / output interface of EC31. EC31 can control the operations of these devices. The input / output interface may be wirelessly connected to various devices to enable data transmission and reception. The input device 32 may be wirelessly connected to EC31 using the input / output interface. The input / output interface may implement a wireless connection using, for example, a short-range wireless communication method defined in IEEE802.15.1.

[0036] EC31 monitors the usage environment of the information processing apparatus 1 based on various electrical signals input to itself. EC31 determines whether a sound source is connected based on the potential of a signal cable connecting the audio system 26 and the sound source 44. Here, EC31 can detect, for example, the potential difference between a reference potential line (ground line) that forms part of the signal cable and the signal line, and determine whether a sound source is connected based on whether the detected potential difference is equal to or greater than a reference value of a predetermined potential difference.

[0037] When EC31 determines that the sound source 44 is connected, it measures the impedance of the sound source 44. Here, EC31 causes the audio system 26 to output a test signal to the sound source 44. At this time, EC31 measures the output level obtained by passing through the processing circuit 36 from the test signal output from the audio terminal 124a to the sound source 44. EC31 can calculate the impedance of the sound source 44 based on the measured output level and the internal impedance of the audio system 26. EC31 notifies the calculated impedance to the host system. The host system determines the gain of the audio signal output from the audio system 26 to the sound source 44 so that it becomes higher as the impedance notified from EC31 is higher. Therefore, the higher the impedance of the sound source 44, the higher the output level of the audio signal.

[0038] The input device 32 detects the user's operation and outputs an operation signal generated according to the detected operation to EC31. As the input device 32, for example, the keyboard 107 and the touch pad 109 are applicable. The input device 32 may further include a touch sensor. The touch sensor may overlap with the display 103 forming the display unit and be configured as a touch panel.

[0039] The power supply circuit 33 supplies the power required for the operation of each device provided in the information processing apparatus 1 according to the control of EC31. The devices to which power is supplied include not only system devices but also peripheral devices. Also, peripheral devices connected to the USB connector 24 can also be power supply destinations. The operating voltage of the devices may be different for each individual device. Among various devices, there may be devices that require multiple levels of voltage. The multiple levels of voltage may include a reference voltage in addition to the operating voltage.

[0040] The power supply circuit 33 includes a converter that converts the voltage of the power supplied to itself, and a power feeder that supplies the power with the converted voltage to the battery 34. When power is supplied from an AC adapter (not shown), the power feeder supplies the power remaining without being consumed in each device to the battery 34. When power is not supplied from the AC adapter, or when the power supplied from the AC adapter is insufficient for the power consumption consumed in each device, the power discharged from the battery 34 is supplied to each device as operating power.

[0041] As the converter, for example, one or a plurality of DC / DC converters are used. The plurality of DC / DC converters may be selectively used according to the voltage after conversion. Also, a first type of converter, which is a part of the plurality of DC / DC converters, may be connected to a device whose operating state may differ according to the system device or the operating mode of the system device. The first type of converter may control the power supplied based on the operating mode notified from the EC31. Another part of the plurality of DC / DC converters, a second type of converter, may be connected to a device that operates regardless of the operating mode of the system device. The second type of converter may be able to constantly supply a certain amount of power. Examples of devices that operate regardless of the operating mode of the system device include the EC31, the processing circuit 36, and the sound source 44.

[0042] The battery 34 stores the power supplied from the power supply circuit 33 based on the control of the power supply circuit 33. The battery 34 discharges a part of the stored power to the power supply circuit 33. As the battery 34, a secondary battery is used. The secondary battery is a storage battery that can be charged and discharged. The secondary battery is, for example, a lithium-ion battery. The AC adapter converts the AC power supplied from an external power source into DC power with a constant voltage and supplies the converted power to the power supply circuit 33. The AC adapter includes a mounting tool that is detachable from the housing of the information processing apparatus 1 including the power supply circuit 33. The mounting tool includes an interface capable of transmitting both power and data according to a predetermined standard. As the predetermined standard, for example, USB Type-C can be used.

[0043] The processing circuit 36 is connected between the audio system 26 and the EC 31 and includes a rectifying element that rectifies a test signal input from the audio system 26 and a low-pass circuit that extracts a low-frequency component of the rectified test signal. The processing circuit 36 outputs an output signal output from the low-pass circuit to the EC 31. The EC 31 can detect the potential of the output signal input from the processing circuit 36 as the output level of the test signal supplied to the sound source 44.

[0044] Next, a method for adjusting the output level of the audio signal will be described in more detail. FIG. 3 is a schematic block diagram showing an example of a hardware configuration related to the adjustment of the output level according to the present embodiment. In the example of FIG. 3, the codec 26c is built into the audio system 26. As an example of the sound source 44, headphones 44h are used, and it is assumed that they are detachable from the audio terminal 124a. When the headphones 44h are connected to the audio terminal 124a, the speakers corresponding to each ear of the headphones 44h are electrically connected to the codec 26c using the signal cables of the audio channels corresponding to those ears. The codec 26c is connected to the CPU 11 and operates according to the control of the CPU 11. The codec 26c is connected to the CPU 11, for example, according to the HDA (High Definition Audio) standard. The codec 26c converts the digital audio data input from the CPU 11 into an analog audio signal. The analog audio signal is sent to the audio terminal 124a using one set of signal cables for each individual audio channel. One set of signal cables includes two conductors. One of the two conductors is connected to the reference potential point (GND) and functions as the reference potential line, and the other conductor functions as the signal line that transmits the substantial audio signal. The audio signal represents the audio waveform by the time change of the potential. Note that in FIG. 3, R1 indicates the internal resistance of the audio system 26. The audio system 26 may include an amplifier (not shown) that amplifies the audio signal and may be able to adjust the volume. Generally, the higher the amplification rate of the audio signal by the amplifier, the smaller the internal resistance R1.

[0045] EC31 has two audio signal terminals. The signal line connected to one of the audio signal terminals HP_DET has a pull-up resistor R pIt is electrically connected to the reference potential line and one end of switch 124s. The other end of switch 124s is electrically connected to the other end of the reference potential line. Switch 124s is a mechanical switch and is built-in or adjacent to audio terminal 124a. When the audio plug is inserted into audio terminal 124a, the contacts of switch 124s touch both ends and short-circuit (switch ON). In this state, when the audio plug is detached from audio terminal 124a, the contacts of switch 124s separate from both ends and are insulated (switch OFF). Therefore, EC31 monitors (monitors) the potential of the audio signal terminal HP_DET and the signal line. EC31 determines whether the measured potential is below a predetermined detection threshold when no audio signal is output to the headphones 44h. EC31 can determine that the headphones 44h are connected to the audio terminal 124a when the absolute value of the potential difference is below the detection threshold. EC31 can determine that the headphones 44h have been detached from the audio terminal 124a when the absolute value of the potential difference exceeds the reference value. When the headphones 44h are not connected, the potential at the audio signal terminal HP_DET is significantly higher than the reference potential.

[0046] When EC31 determines that the headphones 44h are connected, it notifies the CPU11 of the connection to the headphones 44h. When the CPU11 is notified of the connection to the headphones 44h from the EC31, it outputs an audio signal with known characteristics as a test signal for each audio channel to the audio system 26. The test signal output from the codec 26c is attenuated by the internal resistance R1 and supplied to the headphones 44h via the audio terminal 124a and also supplied to the EC31 via the processing circuit 36.

[0047] In EC31, the amplitude V1 and frequency f1 of the output voltage of the test signal are preset. As the frequency f1, an audio signal having a frequency component higher than the audible frequency (typically, 20 Hz to 20 kHz), for example, 20.5 kHz, may be applied. The test signal may be a sine wave of the frequency. Thereby, even if a voice based on the test signal is presented to the user wearing the headphones 44h, the presented voice is not perceived. Strictly speaking, an impedance difference occurs between an audio signal having a frequency component of the audible frequency and a test signal having a higher frequency component. However, the frequency dependence of the impedance is not as significant as the dependence due to the structure of the sound source.

[0048] The processing circuit 36 includes a rectifying element and a low-pass filter (LPF). The rectifying element rectifies the test signal input from the audio system 26 and outputs the rectified signal obtained by rectification to the low-pass filter. The low-pass filter has a low-pass characteristic of passing more of the lower-frequency components among the frequency components of the rectified signal input from the rectifying element, and outputs the rectified signal after passing as a low-pass signal to EC31. The low-pass characteristic can also be regarded as temporal smoothing. The low-pass characteristic may be set so that mainly the DC component of the rectified test signal remains in the low-pass signal. EC31 measures the potential V_DET of the test signal input from the processing circuit 36. The measured potential V_DET corresponds to the output level V2 of the test signal output from the audio system 26. In the example of FIG. 3, the test signal is input to the input terminal of the analog-to-digital converter (ADC) provided in EC31 and converted into a digital signal. A potential V_DET indicating a real value transmitted by the converted digital signal is obtained.

[0049] EC31 can estimate the impedance R of the headphones 44h based on the measured output level V2, the internal resistance R1 of the preset audio system 26, and the output voltage V1. L The impedance R Lis obtained by multiplying the internal resistance R1 by the ratio V2 / (V1 - V2) of the output level V2 to the output voltage V1. This relationship is such that the ratio of the output voltage V1 to the output level V2 is equivalent to the ratio of the combined total impedance R1 + R of the internal resistance R1 and the impedance R L and the impedance R L and the impedance R L and the impedance R.

[0050] EC31 notifies the calculated impedance R L to the CPU11. A setting table showing the relationship between the impedance of the sound source and the output gain corresponding to the adjusted output voltage is preset in the CPU11. The CPU11 refers to the setting table, determines the output gain corresponding to the impedance R L notified from the EC31, and sets the determined output gain in the audio system 26. The output gain corresponds to the ratio of the output voltage of the audio signal to be output to a predetermined reference output voltage (hereinafter referred to as "reference output voltage") in the codec 26c. The audio system 26 multiplies the signal value of each sample forming the audio signal converted by DA conversion by the set output gain. The audio system 26 outputs the audio signal including the multiplication value obtained by the multiplication as the volume-adjusted audio signal to the audio terminal 124a.

[0051] The maximum output voltage may be described in the setting table in association with the impedance. In that case, the CPU11 refers to the setting table and the impedance R notified from the EC31 LFurther specify the maximum output voltage corresponding thereto. The CPU 11 determines an output gain corresponding to the default output voltage specified as described above, and sets the determined output gain in the audio system 26. On the other hand, the CPU 11 sets the specified maximum voltage in the audio system 26. The audio system 26 adjusts the amplitude of the audio signal so that the voltage value indicating the audio signal after volume adjustment does not exceed the set maximum voltage. The audio system 26 outputs the audio signal after amplitude adjustment to the audio terminal 124a. Thereby, supply of an audio signal with power exceeding the maximum output voltage to the headphones 44h is avoided.

[0052] Note that the power consumption P by the audio signal supplied to the headphones 44h and the output voltage U from the codec 26c have the relationship expressed by Equation (1). According to Equation (1), the output voltage U is equal to the multiplication value obtained by multiplying the sum of the internal resistance R1 of the audio system 26 and the impedance R L of the headphones 44h by the square root of the ratio of the power consumption P to the impedance R L Here, the audio terminal 124a can also be regarded as an output point that divides the voltage of the audio signal output from the codec 26c in the ratio of the internal resistance R1 and the impedance R L The square root of the ratio of the power consumption P to the impedance R L corresponds to the current I supplied to the headphones 44h. The default output voltage corresponds to the voltage value U calculated using Equation (1) with respect to the rated power consumption P of the headphones 44h.

[0053] The default output gain is calculated by dividing the default output voltage U corresponding to the impedance R L of the headphones 44h by the reference output voltage corresponding to the reference impedance. As described above, the impedance R L is determined based on the output voltage V1 of the test signal, the measured output level V2, and the internal resistance R1 of the audio system 26. The default output gain is determined by the impedance R LIt is determined based on the rated power consumption P of the headphones 44h and the internal resistance R1 of the audio system 26. The maximum voltage corresponds to the voltage value U calculated using Equation (1) for the maximum power consumption P allowed for the headphones 44h. That is, the maximum voltage is determined by the impedance R determined by the measured output level V2. L It is determined based on the maximum power consumption P of the headphones 44h and the internal resistance R1 of the audio system 26.

[0054] [Number]

[0055] FIG. 4 is a diagram showing an example of the setting table according to the present embodiment. The setting table shown in FIG. 4 has a set of output level V_DET (unit: V), impedance R L (unit: Ω), maximum output voltage V max (V), and register value, and is configured to include these for each output level V_DET. This output level V_DET corresponds to the above output level V2. Under a certain internal resistance R1 and output voltage V1, as the output level V_DET increases, the impedance R L increases, and the increase rate of the impedance R L with respect to the increase in the output level V_DET also increases. Also, as the output level V_DET increases, the maximum output voltage V max , and the output gain G also increase respectively. As the output level V_DET increases, the increase rate of the output gain G with respect to the increase in the output level V_DET also tends to increase, but it is not as significant as the increase rate of the impedance R L . The maximum output voltage V max is approximately proportional to the output gain G.

[0056] FIG. 5 shows an example of setting impedance and maximum output voltage for each model of the headphones 44h. Four models of headphones with different structures were used as measurement targets. The output level of the test signal and the headphone output (power consumption) were made constant as V1 and P, respectively, regardless of the model. Also, the internal resistance R1 of the audio system 26 was made constant. The measured impedance R L,1 ~R L,4 varies greatly depending on the model. A difference of more than 10 times occurred between the minimum value R L,1 and the maximum R L,4 . In the example of FIG. 5, the detection threshold varies for each model, but the detection threshold may be a common constant value regardless of the model.

[0057] Note that the rated power consumption may be common regardless of the model of the headphones 44h as described above, or may vary depending on the model. The maximum output voltage may vary depending on the model of the headphones 44h as described above, or may be common regardless of the model. When one or both of the rated power consumption and the maximum output voltage vary depending on the model, a preset table may be set for each model in the CPU 11 or the audio system 26. When the headphones 44h are connected to the audio system 26, the headphones may output a notification signal indicating the model information indicating their own model to the EC 31, and the EC 31 may notify the CPU 11 of the model information indicated by the notification signal. The CPU 11 can select the setting table corresponding to the notified model information and determine the output gain and the maximum output voltage using the selected setting table.

[0058] Next, an example of volume control according to the present embodiment will be described. FIG. 6 is a flowchart illustrating the volume control according to the present embodiment. (Step S102) The EC 31 monitors the voltage of the audio signal output from the audio terminal 124a, and determines whether the headphones 44h are connected based on the voltage. When it is determined that the headphones are connected (Step S102 Headphone detection YES), the process proceeds to the process of Step S104. When it is determined that the headphones are not connected (Step S102 Headphone detection NO), the process of Step S102 is repeated. (Step S104) The CPU 11 outputs a test signal having a frequency higher than the audible band from the codec 26c provided in the audio system 26 to the audio terminal 124a.

[0059] (Step S106) The EC 31 measures the output level of the test signal input from the audio terminal 124a via the processing circuit 36. The measured output level depends on the impedance of the headphones 44h. The EC 31 notifies the CPU 11 of the measured output level. (Step S108) The CPU 11 refers to the setting table, determines the maximum output voltage corresponding to the output level notified from the EC 31, and sets the determined maximum output voltage as the maximum output voltage of the audio signal output from the audio system 26.

[0060] (Step S110) The CPU 11 refers to the setting table, determines the output gain corresponding to the output level notified from the EC 31, and sets the determined output gain as the output gain in the audio system 26. (Step S112) The audio system 26 adjusts the volume of the audio signal decoded by the codec 26c based on the set output gain, and outputs the audio signal after volume adjustment to the headphones 44h via the audio terminal 124a. Then, the process of FIG. 6 ends.

[0061] Next, a configuration example of the processing circuit 36 according to the present embodiment will be described. FIG. 7 is a circuit diagram showing a configuration example of the processing circuit 36 according to the present embodiment. In FIG. 7, illustration of the reference signal line is omitted. Also, it is assumed that the headphones 44h are connected to the audio terminal 124a. The processing circuit 36 includes a rectifying element D2, resistive elements R2, R3, and a storage element C2. The rectifying element D2 and the resistive element R2 are connected in series. The resistive element R2 is connected in series with each of the resistive element R2 and the storage element C2. The resistive element R2 and the storage element C3 are parallel to each other and also parallel to the EC 31.

[0062] The rectifying element D2 rectifies the audio signal input from the audio system 26, passes the forward component with a positive potential, and blocks the reverse component with a negative potential. The rectifying element D2 outputs the forward component as a rectified audio signal to one end of the resistance element R2. The rectifying element D2 is, for example, a diode. The resistance element R2 has a rectified audio signal input from the rectifying element D2 at one end thereof. The resistance element R2 allows the input audio signal to pass through with an electrical resistance value R2, and outputs it from the other end to one end of the storage element C2, one end of the resistance element R3, and the input terminal of the EC31, respectively. An audio signal is input from the other end of the resistance element R2 to one end of each of the storage element C2 and the resistance element R3. The other ends of the storage element C2 and the resistance element R3 are electrically connected to the reference potential point. Therefore, both the storage element C2 and the resistance element R3 form an RC circuit in parallel with the EC31.

[0063] With this configuration, the processing circuit 36 functions as a low-pass filter having a low-pass characteristic with respect to the forward component obtained by the rectifying element D2. The time constant, which is the product of the capacitance C2 of the storage element and the electrical resistance value R3 of the resistance element, is set such that it is sufficiently larger than the reciprocal of the frequency of the main component of the test signal. The forward component obtained by the rectifying element D2 is smoothed over time, and mainly the DC component is supplied to the EC31.

[0064] The output level V(t) of the test signal output from the codec 26c with a constant amplitude increases with the passage of time and approaches a constant value E. As shown in FIG. 8, the output level V(t) is E(1 - e -1 / R3C2) As a result, the difference from E decays exponentially with the time constant R3C2. Fig. 9 shows the output level V(t) when E = 1V, R3 = 300 kΩ, and C2 = 100 nF. The output level V(t) is initially 0V and does not immediately reach E = 1V immediately after the output of the test signal. It becomes 0.9V when the elapsed time t from the start of the output of the test signal is 0.69 ms. Therefore, EC31 detects the output level after a time sufficiently longer than the time constant R3C2 (for example, 2.3R3C2 or more) has elapsed since the start of the output of the test signal.

[0065] In the above description, the case where the CPU 11 refers to the setting table to determine the output gain or the maximum power corresponding to the measured output level is taken as an example, but it is not limited to this. The CPU 11 may calculate the output gain or the maximum power from the output level using a preset calculation formula. Also, in the above description, the case where the CPU 11 (i.e., the host system) and the EC31 are used as the controllers for performing the volume control and their processes are shared is taken as an example, but it is not limited to this. Either the host system or the EC31 may execute the processes related to the above volume control in a lump without sharing them.

[0066] Also, in the above description, the case where the information processing apparatus 1 is configured as a notebook PC is taken as an example, but it is not limited to this. The information processing apparatus 1 may be configured as, for example, a mobile phone or a tablet terminal device. Also, a sound source different from the detachable sound source 44 using the audio terminal 124a may be built in the information processing apparatus 1. In that case, when the host system detects the connection of the sound source 44 to the audio terminal 124a, it disconnects the connection to the built-in sound source. When the host system detects the detachment of the sound source 44 from the audio terminal 124a, it reconnects to the built-in sound source.

[0067] As described above, the controller (e.g., host system, EC31) according to the present embodiment and the audio system 26 are provided. When detecting the connection between the audio system 26 and the sound source 44, the controller measures the output level of the test signal output to the sound source 44. The controller determines the output gain of the audio signal output from the audio system to the sound source 44 based on the measured output level. The controller can determine the output gain based on, for example, the impedance of the sound source 44 corresponding to the output level, the rated power consumption of the sound source 44, and the internal resistance of the audio system.

[0068] With this configuration, when the sound source 44 is connected to the audio system 26, the output level of the test signal output to the sound source 44 is measured. Based on the measured output level, the output gain of the audio signal output from the audio system 26 to the sound source 44 is determined. Here, the controller determines the output gain of the audio signal so that it becomes larger as the measured output level is higher. Since the output level that becomes lower as the impedance of the sound source 44 connected to the audio system 26 is higher is compensated, the difference in output level is reduced according to the type of the sound source 44.

[0069] Further, the controller may determine the maximum voltage of the audio signal based on the impedance of the sound source 44, the maximum power consumption of the sound source, and the internal resistance. The audio system 26 controls the voltage of the audio signal output from its own part so as not to exceed the maximum voltage, thereby avoiding the input of an audio signal having an excessive voltage exceeding the maximum voltage to the sound source 44. Therefore, the sound source 44 is protected.

[0070] The test signal may have a frequency component whose frequency is higher than the audible band. Even when the sound source 44 is attached and a sound based on the test signal is presented, the listener does not perceive the presented sound. Therefore, the listener can avoid the discomfort caused by the presentation of the sound based on the test signal.

[0071] The information processing apparatus 1 may include a rectifying element that rectifies a test signal and outputs a rectified signal, and a low-pass filter that extracts a low-pass signal from the rectified signal. Further, the controller may measure the output level of the low-pass signal. With this configuration, the DC component of the rectified signal obtained by rectifying the test signal is obtained as the main component, and its output level is measured. Therefore, the power of the test signal can be estimated with the output level measured by a simple configuration.

[0072] The low-pass filter may include a resistance element and a storage element in parallel with the controller. The controller may detect the output level after a predetermined time from the output of the test signal. The predetermined time shall be a value larger than the product of the resistance value of the resistance element and the capacitance of the storage element. Since the output level approximated to a constant value is detected after a sufficient time has elapsed from the start of the output of the test signal, the output level of the DC component is detected more accurately than immediately after the start of the output of the test signal.

[0073] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the above-described embodiments, and designs and the like within the scope not departing from the gist of the present invention are also included. Each configuration described in the above embodiments can be arbitrarily combined.

Description of Reference Numerals

[0074] 1... Information processing apparatus, 11... CPU, 12... Main memory, 13... GPU, 21... PCH, 22... BIOS memory, 23... Auxiliary storage device, 24... USB connector, 25... WLAN card, 26... Audio system, 26c... Codec, 31... EC, 32... Input device, 33... Power supply circuit, 34... Battery, 36... Processing circuit, 44... Sound source, 44h... Headphone, 101... First housing, 103... Display, 105... Second housing, C2... Storage element, D2... Rectifying element, R2, R3... Resistance element

Claims

1. An information processing apparatus comprising a controller and an audio system, wherein the controller, when detecting a connection between the audio system and a sound source, measures an output level of a test signal output to the sound source, and determines an output gain of an audio signal output from the audio system to the sound source based on the output level. Information processing apparatus.

2. The controller, determines the output gain based on an impedance of the sound source corresponding to the output level, a rated power consumption of the sound source, and an internal resistance of the audio system. The information processing apparatus according to claim 1.

3. The controller, determines a maximum voltage of the audio signal based on the impedance of the sound source, a maximum power consumption of the sound source, and the internal resistance. The information processing apparatus according to claim 2.

4. The test signal has a frequency component higher than an audible band. The information processing apparatus according to claim 1.

5. A rectifying element that rectifies the test signal to output a rectified signal, and a low-pass filter that extracts a low-pass signal from the rectified signal, wherein the controller, measures an output level of the low-pass signal. The information processing apparatus according to claim 4.

6. The low-pass filter, includes a resistance element and a storage element in parallel with the controller, wherein the controller, detects the output level after a lapse of a predetermined time from the start of output of the test signal, and the predetermined time is longer than a product of a resistance value of the resistance element and a capacitance of the storage element. The information processing apparatus according to claim 5.

7. A control method for an information processing apparatus including a controller and an audio system, the method comprising: when the controller detects a connection between the audio system and a sound source, measuring an output level of a test signal output to the sound source; and determining an output gain of an audio signal output from the audio system to the sound source based on the output level. Control method.

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