JP2009094684A - Electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic apparatus for preventing suspension of drive that may be caused by drop of voltage. <P>SOLUTION: A capacitor 25, a current limiting circuit 19, and a current limiting circuit 20 are connected to the power stage of a power amplifier 24. A CPU 21 supervises voltage of the capacitor 25 to compensate for gain of the power amplifier 24 in accordance with a voltage value. Moreover, when speakers for a plurality of channels are used, reproduction mode can be switched, for example, for stereophonic reproduction and monaural reproduction in accordance with the voltage value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic device that can instantaneously consume a large amount of power while having a small amount of power supply.

  Conventionally, portable USB devices that are driven by bus power are known. However, USB bus power can only supply a current of 100 mA (at most about 500 mA), and a USB device that consumes a large current is generally connected to an AC adapter.

Thus, for example, Japanese Patent Application Laid-Open No. H10-228561 discloses a device that is supplied with power from two USB cables using a conversion cable between a DC connector and a USB connector.
JP-A-2005-141732

  However, the power supply method disclosed in Patent Document 1 is not used within the USB standard and does not guarantee stable operation. Further, in a device such as a power amplifier that requires a current of about several A instantaneously, the supply amount is still insufficient. Thus, when the supply amount is insufficient, there is a problem that the voltage of the power amplifier is lowered and the entire apparatus is suddenly stopped.

  Therefore, an object of the present invention is to provide an electronic device that can prevent a drive stop due to a voltage drop.

  The electronic apparatus according to the present invention includes a power input unit that receives power supply, a main drive circuit that is driven by current supply from the power input unit, and gain correction of the main drive circuit according to a voltage value of the main drive circuit And a control unit for performing the above.

  In this configuration, gain correction is performed according to the voltage value of the main drive circuit. That is, when the voltage value is low, the gain is set small, and the power consumption is suppressed. This prevents a sudden stop of the main drive circuit.

  According to another aspect of the present invention, there is provided an electronic device that emits sound by inputting a power input unit that receives a current supply, a power amplifier that is driven by a current supply from the power input unit, and an audio signal amplified by the power amplifier A plurality of speaker units, and a control unit that changes a supply mode of an audio signal to the power amplifier and the speaker unit according to a voltage value of the power amplifier.

  In this configuration, the audio signal supply mode is changed according to the voltage value of the power amplifier. For example, monaural reproduction (one-channel reproduction) is performed when the voltage drop is large, and stereo reproduction is performed when the voltage drop is small.

  In addition, the present invention further includes a power storage circuit connected to a front stage of the main drive circuit, wherein the control unit performs gain correction of the main drive circuit according to a voltage value of the power storage circuit. To do.

  In this configuration, a power storage circuit (capacitor) is connected to the previous stage of the main drive circuit, and power is stored. When the main drive circuit consumes more power than the supply current value, current is supplied from the storage circuit. Here, the control unit performs gain correction of the main drive circuit according to the voltage value of the power storage circuit. That is, when the voltage value drops, the gain is set to be small, and the power consumption is suppressed. This prevents a sudden stop of the main drive circuit due to a voltage drop.

  Further, according to the present invention, the main drive circuit is a power amplifier, and the control unit corrects the gain of the power amplifier in accordance with a drop in the voltage value of the power storage circuit or the main drive circuit. Features.

  In this configuration, the gain of the power amplifier is corrected. That is, when the voltage of the power storage circuit drops, the sound emission volume is reduced to reduce the power consumption and prevent sudden stop.

  Further, the electronic device of the present invention includes a power storage circuit connected to a power stage of the power amplifier, and the control unit outputs an audio signal to the power amplifier and the speaker unit according to a voltage value of the power storage circuit. The supply mode is changed.

  In this configuration, the audio signal supply mode is changed according to the voltage value of the power storage circuit. For example, monaural reproduction (one-channel reproduction) is performed when the voltage drop is large, and stereo reproduction is performed when the voltage drop is small.

  Further, according to the present invention, the control unit further performs phase control of audio signals supplied to the plurality of speaker units when the voltage value of the power storage circuit or the power amplifier is at or near the upper limit, and releases the phase. A process of setting a virtual sound source in the sound space is performed.

  In this configuration, when the voltage value is at or near the upper limit (that is, the maximum charging state), the phase of the audio signal is controlled using a plurality of speaker units, and reproduction is performed to set a virtual sound source.

  According to the present invention, it is possible to prevent the drive from being stopped due to a voltage drop.

  Hereinafter, the electronic apparatus according to the present embodiment will be described. The electronic device of this embodiment is a portable speaker device that is driven by bus power by USB connection, self-power by AC adapter connection, or both bus power and self-power.

  FIG. 1 is a block diagram showing a power circuit configuration of the speaker device according to the present embodiment. As shown in the figure, the speaker device 1 includes a USB power input circuit 11, an AC adapter power input circuit 12, a regulator (LDO) 13, a switch (HSSW) 14, a switch (SW) 15, a switch (SW) 16, a DC A DC converter (DC-DC) 17, a regulator (LDO) 18, a current limiting circuit 19, a current limiting circuit 20, a CPU 21, a digital circuit 22, an analog circuit 23, a power amplifier 24, and a capacitor 25 are provided.

  The CPU 21 is a control unit that comprehensively controls the speaker device 1. The digital circuit 22 and the analog circuit 23 are circuits that perform various audio processes. The audio signal processed by the digital circuit 22 and the analog circuit 23 is amplified by the power amplifier 24 and emitted to the outside.

  The USB power input circuit 11 is an interface that receives power supply from an information processing apparatus (host) such as a PC, and receives power supply of 100 mA or 500 mA. The speaker device 1 performs bus power driving by supplying current input from the USB power input circuit 11 to the CPU 21, the digital circuit 22, and the analog circuit 23. When a USB device is connected to a host, it first receives a power supply of 100 mA, and if a subsequent negotiation is established, it can receive a power supply of 500 mA.

  The AC adapter power input circuit 12 is an interface that receives power supply from the AC adapter, and receives power supply of about 700 mA, for example. The speaker device 1 performs self-power drive by supplying current input from the AC adapter power input circuit 12 to the CPU 21, digital circuit 22, and analog circuit 23.

  The LDO 13 is turned on / off in conjunction with the power supply input, and is turned on when power is supplied from the USB power supply input circuit 11 to stabilize the output voltage to 3.3V. When power is supplied from the AC adapter power input circuit 12, the power is turned off.

  The HSSW 14 is a switch circuit controlled by the CPU 21 and is turned on when bus power driving is performed, and turned off in other cases.

  The SW 15 is a switch circuit controlled by the CPU 21 and is turned on when performing bus power driving.

  The SW 16 is turned on when power is supplied from the AC adapter power input circuit 12.

  The DC-DC converter 17 performs transformation, and transforms the supply voltage to the digital circuit 22 and the CPU 21 from 5V to 3.3V.

  The LDO 18 is always turned on and stabilizes the supply voltage to the analog circuit 23 to 3.3V.

  The current limiting circuit 19 and the current limiting circuit 20 are circuits that limit the amount of current supplied to the power amplifier 24 and the capacitor 25. The current limiting circuit 19 limits the output current to 100 mA, and the current limiting circuit 20 limits the output current to 150 mA.

  The capacitor 25 is an electric double layer capacitor having a very large capacitance (for example, several tens of μF or more). Since the capacitor 25 has a very large capacitance, the CPU 21 and the like cannot be operated if all the supply current from the USB power input circuit 11 and the AC adapter power input circuit 12 is consumed for charging. Therefore, in order to protect various circuits of the speaker device, a current limiting circuit 19 and a current limiting circuit 20 are provided to limit the current.

  In this embodiment, since the voltage is stored in the capacitor 25, when the speaker device emits sound that instantaneously consumes about several watts, power can be supplied from the capacitor 25 to the power amplifier 24. is there. The speaker device 1 according to the present embodiment performs stable power supply while accumulating voltage in a large-capacitance capacitor 25, depending on the form of power supply from the USB power input circuit 11 and the AC adapter power input circuit 12. LDO13, HSSW14, SW15, and SW16 are switched on and off. In addition, when the sound is continuously emitted and the power amplifier 24 continuously consumes power, the voltage of the capacitor 25 drops, and the voltage may be lower than the driving limit value (for example, 2.7 V or lower). . Therefore, in this embodiment, various operations are performed in order to suppress the voltage drop.

  First, FIG. 2 is a diagram showing a state switching list. As shown in the figure, the speaker device 1 switches six states. First, in a state where no power is supplied from the USB power input circuit 11 and the AC adapter power input circuit 12, that is, in a state where nothing is connected to the speaker device 1, the CPU 21 does not drive, and of course various switches remain off. Yes (state 1).

  When the speaker device 1 is connected to the host and a current of 100 mA is input from the USB power input circuit 11, power is supplied to the CPU 21 via the LDO 13, and as a result, the CPU 21 is activated (state 2). Here, the CPU 21 negotiates with the host. If the negotiation is not possible, the speaker device cannot be driven and the state is switched to state 1 again, and the power is turned off.

  If the negotiation is established, the CPU 21 assumes that the bus power drive with 500 mA input is possible, sets the HSSW 14 and SW 15 to ON, and sets the current input from the USB power input circuit 11 to the digital circuit 22, the analog circuit 23, And is supplied to the current limiting circuit 19 (state 3). Further, 5 V power is supplied to the front stage of the power amplifier 24 (+5 A).

  Here, the current limiting circuit 19 limits the output current to 100 mA and supplies it to the power amplifier 24. Further, the capacitor 25 is charged by this current. When the voltage of the capacitor 25 is boosted to about 2.7 V, sufficient power (current exceeding 100 mA) can be supplied to the power amplifier 24 even in the bus power drive. Actually, it may be driven after boosting to about 3 to 3.5 V in consideration of a margin.

  That is, the power amplifier 24 receives a current of 100 mA from the current limiting circuit 19 and amplifies the audio signal. However, depending on the amount of amplification, the power amplifier 24 may consume a current exceeding 100 mA. . Here, if the power amplifier 24 consumes a current exceeding 100 mA, the voltage of the capacitor 25 drops. However, since a current of 100 mA is constantly supplied from the current limiting circuit 19, charging is performed again when the current consumption of the power amplifier 24 is reduced. As a result, the speaker device 1 can instantaneously output several watts while being driven by the bus power, and can perform stable driving.

  Next, when the speaker device 1 is not connected to the host and only the AC adapter is connected, a current of about 700 mA is input from the AC adapter power input circuit 12. In this case, the SW 16 is turned on and power is supplied to the CPU 21. As a result, the CPU 21 is activated (state 4). The power line from the AC adapter power input circuit 12 to the DC-DC converter 17 is monitored by a detection circuit (not shown), and when current is supplied to the power line, the switch of the SW 16 is turned on. It has become.

  CPU21 turns off LDO13, HSSW14, and SW15 after starting. As a result, the current input from the AC adapter power input circuit 12 is supplied to the digital circuit 22, the analog circuit 23, and the current limiting circuit 20. In addition, 5 V power is supplied to the front stage of the power amplifier 24.

  Here, the current limiting circuit 20 limits the output current to 150 mA and supplies it to the power amplifier 24. Further, the capacitor 25 is charged by this current. Similarly to the above, when the voltage of the capacitor 25 is boosted to about several volts, sufficient power can be supplied to the power amplifier 24.

  In the self-power drive, the power amplifier 24 receives a current of 150 mA from the current limiting circuit 20 and amplifies the audio signal. However, depending on the amount of amplification, a current exceeding 150 mA may be consumed. Make up for the minute. Here, when the power amplifier 24 consumes a current exceeding 150 mA, the voltage of the capacitor 25 drops. However, since a current of 150 mA is constantly supplied from the current limiting circuit 20, charging is performed again when the current consumption of the power amplifier 24 is reduced. Thereby, the speaker device 1 can perform driving more stable than bus power driving.

  Next, when the speaker device 1 is connected to the host in a self-powered state, a current of 100 mA is input from the USB power input circuit 11. In this case, the CPU 21 negotiates with the host. If the negotiation is not possible, the self-power drive is performed with the various switches as they are (state 5).

  If the negotiation is established, the CPU 21 turns on the HSSW 14 and supplies the current input from the USB power supply input circuit 11 to the current limiting circuit 19 (state 6). As a result, a current of 100 mA is supplied from the current limiting circuit 19 to the power amplifier 24, and a current of 150 mA is supplied from the current limiting circuit 20. Therefore, a current of 250 mA is supplied to the power amplifier 24 and the capacitor 25.

  When the AC adapter is connected in the bus power drive state (state 3), the CPU 21 turns on the SW16, turns off the LDO 13 and the SW15, and switches to the state 6.

  Next, FIG. 3 is a diagram showing a voltage change of the capacitor 25. As shown in the figure, since the capacitor 25 is supplied with a current of 5 V from the USB power input circuit 11 or the AC adapter power input circuit 12, it is charged to a maximum of 5V. When the power amplifier 24 does not consume power (or is driven at 100 mA or 150 mA or less), the voltage is kept at 5 V (voltage change 1).

  Here, when the power amplifier 24 consumes power, current is supplied from the capacitor 25 and the voltage of the capacitor 25 drops (voltage change 2). When the sound emission is stopped and the power consumption of the power amplifier 24 is eliminated, the capacitor 25 is again supplied with current and charged (voltage change 3).

  Since the power consumption increases as the amplification amount of the power amplifier 24 increases (the volume of the emitted sound increases), the inclination of the voltage drop of the capacitor 25 increases, and the inclination of the voltage drop decreases as the amplification amount decreases. For example, if the sound is emitted at a volume smaller than that in the case of the voltage change 2, the slope of the voltage drop becomes small (voltage change 4). On the other hand, when no sound is emitted, the current supply amount to the capacitor 25 does not change at 100 mA or 150 mA, and the step-up gradient does not change (voltage change 5).

  If the voltage decreases without changing the power consumption, the current consumption increases. Therefore, if the voltage becomes lower than a predetermined value (for example, 2.7 V), current cannot be supplied to the power amplifier 24, and the output of the power amplifier 24 is reduced. (No sound is emitted). Actually, even if the output of the power amplifier 24 is reduced, the power is supplied to the CPU 21 from the USB power input circuit 11 or the AC adapter power input circuit 12, so that the entire speaker device 1 does not go down.

  In the present embodiment, the following processing is performed to prevent the output of the power amplifier 24 from being reduced.

(1) Gain Correction FIG. 4 is a diagram showing the concept of gain correction according to the voltage of the capacitor 25, and FIG. 5 is a block diagram showing a processing system of the speaker device 1. The speaker device 1 includes a signal processing circuit 200 and a speaker 100 (speakers 100A and 100B) as a processing system, and audio information input from the USB interface (I / F) 101 is subjected to signal processing as a digital audio signal. Input to the circuit 200. The signal processing circuit 200 includes the digital circuit 22 and the analog circuit 23 described above, performs level correction and phase control on the input digital audio signal, and outputs the analog audio signal to the power amplifier 24. The analog audio signal amplified by the power amplifier 24 is emitted from the speaker 100. Note that the speaker device 1 actually processes two-channel audio signals and emits different sounds from the speakers 100A and 100B (performs stereo reproduction), but in FIG. Therefore, a one-channel processing system is shown.

  The signal processing circuit 200, the power amplifier 24, and the capacitor 25 are connected to the CPU 21, and the CPU 21 controls the processing mode of the signal processing circuit 200 and the gain of the power amplifier 24. Further, the voltage of the capacitor 25 is managed by the CPU 21. As shown in FIG. 4, the CPU 21 does not perform gain correction (± 0 dB) when the voltage of the capacitor 25 is 4.5 to 5V. Since the voltage of the capacitor 25 is sufficiently high, the sound is emitted as it is with the gain defined by the power amplifier 24 without performing gain correction.

  When the voltage of the capacitor 25 is 4 to 4.5 V, the CPU 21 corrects the gain of the power amplifier 24 by −3 dB. By performing the gain correction of −3 dB, the volume is reduced and the power consumption of the power amplifier 24 is reduced. Therefore, the slope of the voltage drop is reduced. The CPU 21 performs gain correction of −6 dB when the voltage of the capacitor 25 is 3.5 to 4V, and performs gain correction of −12 dB when the voltage of the capacitor 25 is 3 to 3.5V. As the voltage value decreases, the gain correction amount increases and the volume decreases, so that the slope of the voltage drop further decreases. Therefore, the voltage drop is suppressed. If the voltage is 3V or less, mute is performed to correct power consumption to zero. When the voltage becomes 3V or less, mute is continued until the voltage is restored to a certain level (for example, 3.5V). When mute is performed, the power consumption becomes zero, and the voltage value immediately recovers. However, when the sound is emitted, there is a possibility that it becomes 3 V or less again. For this reason, the operations of mute, mute release, and mute are repeated. Therefore, the muting is canceled at, for example, 3.5 V or more in consideration of a certain margin.

  As described above, since the gain of the power amplifier 24 is corrected according to the voltage value of the capacitor 25, the output of the power amplifier 24 can be prevented from being lowered.

(2) Switching playback mode Next, switching playback mode will be described. The switching of the reproduction mode means that when the speaker device 1 has a two-channel speaker unit as shown in FIG. 5, stereo reproduction, monaural reproduction (one-channel reproduction), or two speaker units are performed. This is an operation for switching between performing reproduction of setting a virtual sound source by controlling the phase of an audio signal.

  That is, when the voltage drop of the capacitor 25 is small, the CPU 21 performs the reproduction in which the signal processing circuit 200 is set to perform phase control and the virtual sound source is set. Further, when the voltage drops to some extent, the CPU 21 sets the signal processing circuit 200 not to perform phase control, and switches to normal stereo reproduction. When the voltage further drops, the operation of switching to monaural playback is performed by cutting off the audio signal supply to one of the speakers (or muting one of the channels). When setting a virtual sound source by phase control, a gain of about twice is required to ensure the same sound pressure as in normal stereo reproduction. Therefore, the slope of the voltage drop becomes the largest. On the other hand, since the speaker driving power for one channel is sufficient for monaural reproduction, the slope of the voltage drop is the smallest. Therefore, the reproduction mode is switched as described above according to the voltage value to prevent the output of the power amplifier 24 from being lowered.

  Further, the playback mode may be switched according to the form of power supply from the USB power input circuit 11 and the AC adapter power input circuit 12. For example, monaural reproduction is performed when bus power driving is performed, stereo reproduction is performed when self power driving is performed, and reproduction in which a virtual sound source is set is performed when driving by both bus power and self power.

  Note that the playback mode may be switched while performing gain correction.

  In the present embodiment, the speaker device is shown as an electronic device. However, the present invention can be applied to any device that performs bus power driving by USB connection and self-power driving by an AC adapter.

  In this embodiment, an example in which the current supply mode is switched between bus power driving and self-power driving has been described. However, this configuration is not essential, and general current supply is performed (the current supply switching function is not provided). ) Applicable to normal equipment. For example, in the case of a device that has a built-in battery and operates only with the battery, the power supply voltage decreases as the usage time elapses. If the power supply voltage decreases, the power amplifier output will be saturated at a smaller signal level, or the drive will be stopped, but by using the technique disclosed in this embodiment, it can be used for a longer time. Become.

  In this embodiment, the gain correction and the reproduction mode are switched according to the voltage value of the capacitor. However, the gain correction and the reproduction mode may be switched according to the voltage value of the power amplifier.

It is a block diagram which shows the power supply circuit structure of the speaker apparatus which concerns on this embodiment. It is a figure which shows a state switching list. FIG. 6 is a diagram illustrating a voltage change of a capacitor 25. It is a figure which shows the concept of the gain control according to the voltage of the capacitor | condenser 25. FIG. 3 is a block diagram showing a processing system of the speaker device 1. FIG.

Explanation of symbols

1-speaker device 11-USB power input circuit 12-AC adapter power input circuit 13-regulator (LDO)
14-switch (HSSW)
15-switch (SW)
16-switch (SW)
17-DC-DC converter (DC-DC)
18-Regulator (LDO)
19-current limiting circuit 20-current limiting circuit 21-CPU
22-Digital circuit 23-Analog circuit 24-Power amplifier 25-Capacitor

Claims (6)

A power input section for receiving power supply;
A main drive circuit driven by current supply from the power input unit;
A control unit that performs gain correction of the main drive circuit according to a voltage value of the main drive circuit;
With electronic equipment. A power input section that receives a current supply;
A power amplifier driven by current supply from the power input unit;
A plurality of speaker units for inputting sound signals amplified by the power amplifier and emitting sound;
In accordance with the voltage value of the power amplifier, a control unit that changes the supply mode of the audio signal to the power amplifier and the speaker unit;
With electronic equipment. A power storage circuit connected to the previous stage of the main drive circuit,
The electronic device according to claim 1, wherein the control unit performs gain correction of the main drive circuit in accordance with a voltage value of the power storage circuit. The main drive circuit is a power amplifier,
The electronic device according to claim 3, wherein the control unit corrects a gain of the power amplifier according to a drop in a voltage value of the power storage circuit. A power storage circuit connected to the power stage of the power amplifier,
The electronic device according to claim 2, wherein the control unit changes a supply mode of an audio signal to the power amplifier and the speaker unit according to a voltage value of the power storage circuit.   The control unit performs phase control of an audio signal supplied to the plurality of speaker units when the voltage value of the power storage circuit or the power amplifier is at or near an upper limit, and sets a virtual sound source in a sound emission space The electronic device according to claim 5, which performs processing.

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