JP3457596B2 - USB compatible speaker drive system - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a USB (Universa
l Serial Bus) The present invention relates to a USB-compatible speaker driving system capable of driving a speaker by connecting to a port.

FIG. 4 is a circuit diagram showing an example of a conventional USB compatible speaker drive system. U shown in the figure
The SB-compatible speaker drive system 1 includes an upstream USB port 3a from a USB port 2a provided in the personal computer main body 2 via a USB cable 3.
It is a system for decoding and reproducing the audio signal supplied to the. A USB interface circuit 4 is connected to the USB port 3a, and the four USB outputs from the USB interface circuit 4 are the downstream side USB.
It is sent to the port 4a and supplied to a keyboard, a mouse and the like. In addition, the USB interface circuit 4 shown in this example is configured such that one system of USB output is passed through the decoding processing circuit 5 and the volume control circuit 6 to the speaker drive amplifier 7 for the left and right channels.
It is supplied to L and 7R. Speaker drive amplifier 7L, 7
Both R are non-inverting amplifiers, and the speaker drive amplifiers 7L and 7R drive the left and right channel speakers 8L and 8R. The audio signal output from the USB interface circuit 4 is supplied to the decoding processing circuit 5 as serial data composed of a differential signal, and is decoded in the decoding processing circuit 5 into analog audio signals of the left and right channels. The decoded left and right channel audio signals are
After being subjected to volume control in the volume control circuit 6, they are supplied to the left and right channel speaker drive amplifiers 7L and 7R, respectively. The speakers 8L and 8R are the speaker drive amplifier 7
The audio signal of the corresponding channel amplified by L and 7R is supplied to reproduce the audio.

As is well known, the USB is an interface standard that enables the personal computer main body 2 and peripheral devices to be connected with the same connector. Since this interface standard transmits serial data as a differential signal, the USB cable 3 serving as a transmission line has a pair of signal lines (D +, D-) and a pair of power supply lines (Vcc, GND).
Take a core wire structure. In addition, an upstream side connector called a series A and a downstream side connector called a series B are connected to both ends of the USB cable 3 having the four-core structure so that they can be distinguished from each other by the difference in the shapes of A and B. It has become. In addition, these connectors are hot-pluggable so that they can be plugged in and unplugged while the power of the personal computer main body 2 is turned on, and the signal pins (D
The pin length of the power supply pin (Vcc, GND) is slightly longer than that of +, D-). Therefore, the power supply pin is first connected at the time of connection, and the power supply pin is disconnected at the time of disconnection so that power is always supplied to the device when the signal pin is connected.

The USB-compatible speaker driving system 1 has a USB interface circuit 4 and a decoding processing circuit 5.
Are simply connected by a pair of signal lines (D +, D-), and USB bus power (DC5V, 0.
1A) is not used. Therefore, a dedicated power source 9 is prepared as a power source for the speaker driving amplifiers 7L and 7R, and the speaker driving amplifiers 7L and 7R are operated by obtaining the power supplied from the dedicated power source 9.

[0005]

The conventional USB compatible speaker driving system 1 described above uses, for example, 80 dB / m by the speakers 8L and 8R having a voice coil impedance of 8Ω.
It is configured to obtain a sound pressure of a certain degree. Therefore, the speaker drive amplifiers 7L and 7R are required to output 1.0 W × 2 (when 8Ω is loaded).
As a dedicated power source 9 to be the operating power source of DC6V, 0.2
A 6A output was needed. In other words, the maximum amplifier output is 0.2 when viewed as an amplifier operating power supply.
W (16Ω load) or 0.12W (8Ω load) had the USB bus power which is the supply limit.
It is extremely impossible to drive the speakers 8L and 8R having a sound pressure of about 80 dB / m, and it is impossible to assume that the bus power that can be taken out from the USB port 2a will be used as a substitute for the dedicated power source 9. In other words, the USB port 2a is insufficient as a power feeding port for this type of application,
The idea of using it only for signal transmission was dominant.

On the other hand, in order to break such an idea,
Some research has been done to replace the power supply dedicated to the amplifier with USB bus power, and as a part of the technology for using USB bus power, a high-efficiency speaker (87- Development of 90 dB / W) was also in progress. However, the high-efficiency speakers that have been prototyped to date often offset the cost reduction effect associated with the removal of the dedicated power supply because the manufacturing cost was extremely high or miniaturization was extremely difficult. In addition, because it cannot be shared with a product that combines only an amplifier and a speaker that does not have a USB hub function, it has not been put into practical use.

Furthermore, in the above-described conventional USB speaker drive system 1, a pair of speaker drive amplifiers 7L and 7R, both of which are non-inverting amplifiers, are used for the speaker 8L,
8R was driven, and the speaker driving amplifiers 7L and 7R were driven in phase with each other. Therefore, the peak currents flowing through the speaker drive amplifiers 7L and 7R are generated not to cancel each other but to have the same polarity,
Speaker drive amplifiers 7L, 7 consumed by the dedicated power source 9
The operating current for R has a remarkable tendency that the amplitude fluctuates up and down. For this reason, it was impossible for the tentative plan to supply power to the speaker drive amplifiers 7L and 7R via the USB port 2a while leaving the excessive current consumption eliminated in the dedicated power supply 9.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to supply power to a speaker driving amplifier via a USB port so that the speaker can be driven without relying on a dedicated power source. is there.

[0009]

In order to achieve the above object, the present invention provides a power source supplied via a USB port.
Speaker drive amplifier that operates more efficiently, and the speaker drive amplifier
Equipped with a high-efficiency stereo speaker driven by a pump
The speaker drive amplifier is one of the stereo signals.
Non-inverting amplifier for non-inverting amplification of channel audio signal
And the audio signal of the other channel of the stereo signal
And an inverting amplifier that performs inverting amplification.
The Tereo speaker is connected to the output terminal of the non-inverting amplifier.
Pole terminals are connected to connect the audio signal of the one channel
The first high-efficiency speaker for reproduction and the output of the inverting amplifier
The negative terminal is connected to the input terminal and the other channel
Consists of a second high-efficiency speaker that reproduces audio signals
It is characterized by being

Further , the first and second high efficiency speakers
Has a voice coil impedance of 16Ω or more.
The feature is that a square tensile film is used for the diaphragm.
And

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows the USB of the present invention.
2A and 2B are vertical cross-sectional views and front views of the speaker shown in FIG. 1, respectively, and FIG. 3 is a USB-compatible speaker of the present invention. It is a circuit block diagram which shows other embodiment of a drive system.

The USB compatible speaker drive system 11 shown in FIG. 1 uses the bus power supplied via the USB port 12a attached to the personal computer main body 12 as U.
It takes in via the SB cable 13, operates a pair of left and right speaker drive amplifiers 17L and 17R, and
The audio signal taken in through the SB port cable 13 is amplified by the speaker drive amplifiers 17L and 17R to drive the speakers 18L and 18R.
That is, the USB compatible speaker drive system 11 shown in the present embodiment outputs the audio signal and the power source transmitted via the USB cable 13 to the upstream side USB.
It is taken into the USB interface circuit 14 via the port 13a and output to the downstream side USB port 14a, while being supplied to the speaker drive amplifiers 17L and 17R via the decoding processing circuit 15 and the volume control circuit 16. U
From the USB port 12a to the US via the SB cable 13
The bus power supplied to the B port 13a is DC5V,
Although it is 0.5 A, the USB interface circuit 14 divides the bus power into 5 systems, DC 5 V and 0.1 A, so that the maximum current consumption is 0.1 A or less in the speaker drive amplifiers 17L and 17R. To use. Also,
The speakers 18L and 18R are also the speaker driving amplifier 17
87 so that it can be driven sufficiently by the maximum output of L and 17R
A high-efficiency type of ~ 90 dB / W is used.

Further, in the USB compatible speaker drive system 11 shown in this embodiment, the speaker drive amplifier 17L for amplifying the audio signal of one channel (here, the left channel) is constituted by a non-inverting amplifier, and the other channel ( Here, the speaker drive amplifier 17R for amplifying the audio signal of the right channel) is composed of an inverting amplifier. For this reason, the speaker drive amplifiers 17L and 17R operate in opposite phases to each other. For example, unlike the case of in-phase drive, the peak currents do not overlap each other and the consumption current does not fluctuate significantly. By canceling out the currents with each other, it is possible to suppress the current consumption associated with driving the speaker. However, the speaker drive amplifier 17
Since the amplification polarities of L and 17R are different, the speaker 18L,
Care must be taken to connect the 18R to the correct polarity. That is, the output terminal of the speaker driving amplifier 17L including a non-inverting amplifier is connected to the positive terminal of the speaker 18L, and the speaker driving amplifier 17R including an inverting amplifier is connected.
Attention should be paid to the connection polarity of the speaker cable such that the output terminal of is connected to the negative terminal of the speaker 18R.

By the way, the speaker drive amplifiers 17L, 1
There are various possible combinations of the 7R and the speakers 18L and 18R. Specifically, for example, the speakers 18L and 18R have a voice coil impedance of 16Ω and an efficiency of 87.
When using the one of dB / W, the speaker drive amplifier 17
By using 2 × 0.2 W (with a load of 16 Ω) output as L and 17R, the required power can be sufficiently covered by the USB bus power allocated to each system.
For example, the speaker drive amplifier 17L (17R) is driven by the power supply voltage Vcc (= 5V) to the SEPP (Single Ended Push-Pu).
ll) When operated, the average current flowing through the speaker 18L (18R) having a load resistance r (= 16Ω) is Vcc / 2π.
r (≈0.05 A), which is 0.1 A even when the left and right channels are combined. That is, the speaker drive amplifier 17
Even if the current limiting circuit is not provided in front of L and 17R, for example, an excessive current exceeding the specified upper limit flows out from the USB port 12a and the personal computer main body 12 side is forced to stop power supply. In addition, the speaker drive amplifiers 17L and 17R can be used with peace of mind without worrying that the operation is abruptly stopped.

As the speakers 18L and 18R, the voice coil impedance is 32Ω and the efficiency is 90 dB /.
When the W amplifier is used, the speaker drive amplifiers 17L, 1
As 7R, a 2 × 0.1 W (with 32Ω load) output may be used, and in this case also, the required power can be sufficiently covered by the USB bus power. Incidentally, the speaker drive amplifier 17L (17R) is SEPPed with the power supply voltage of 5V.
When operated, the speaker 18L (1
8R) has an average current of about 0.025A,
It is 0.05A even when the left and right channels are combined. Therefore,
Even if the current limiting circuit is not provided in front of the speaker driving amplifiers 17L and 17R, an excessive current exceeding the specified upper limit flows out from the USB port 12a, and the personal computer main body 12 side is forced to stop the power supply. There is no such thing.

As is apparent from the above-mentioned specific examples, it is preferable that the speakers 18L and 18R to be used have a voice coil impedance of 16Ω or more, are highly efficient, and can be manufactured at low cost. Therefore, as the speakers 18L and 18R satisfying these conditions, the newly designed and developed structure shown in FIGS. 2A and 2B is used here. Illustrated speakers 18L, 18R
Is a vibrating membrane 22 in a rectangular shape called a tensed diaphragm.
The four sides of the vibrating membrane 22 are supported by a supporting frame 23 having a rectangular frame shape.
The central portion of the back surface of the is driven by the vibrator 24 to generate a sound. The vibrating membrane 22 is, for example, PEN (polyethylene naphthalate), PET (polyethylene terephthalate), a metal vapor-deposited material thereof, or a material such as carbon fiber is formed into a square-shaped membrane having a size covering the front surface of the support frame 23. Use one. That is,
The vibrating membrane 22 is made of a synthetic resin material suitable for membrane processing or a synthetic fiber material having a high tensile strength so that stable vibration characteristics can be maintained over a long period of time. When a film material having high tensile rigidity such as vapor-deposited PEN or PET is used, stable vibration characteristics with little deterioration over time can be constantly maintained. In the present embodiment, the heat-shrinkable rectangular vibrating film 22.
The upper and lower sides and the left and right sides of the diaphragm are fixed to the support frame 23 by adhesion, and after fixing the adhesive, heat is applied to the entire vibrating membrane 22 to apply tensile tension in the vertical and horizontal directions.

More specifically, the vibrating membrane 22 is made by cutting a film material such as PET having a heat shrinkage property in a specific uniaxial direction, and the two opposite sides of the film material are 0 ° to 90 ° (however). The film material is cut so as to obtain the vibrating membrane 22 having upper and lower sides and left and right sides that are parallel to two orthogonal orthogonal axes that are obliquely intersected at an oblique angle. Since the vibrating membrane 22 obtained by cutting has the heat shrinking direction substantially in the diagonal direction, the upper and lower sides and the left and right sides of the vibrating membrane 22 are adhered and fixed to the support frame 23, and then the flat panel heater, the warm air blower, or the infrared heater. The vibrating membrane 22 is heated using the above.
As a result, the vibrating membrane 22 tries to contract in the diagonal direction, and therefore, as a biaxial component force of the tensile tension in the diagonal direction,
A tensile tension is applied in the vertical direction and the horizontal direction, and the vibrating membrane 22 is strained.

The difference in acoustic characteristics based on the difference in shape between the square diaphragm 22 and the circular diaphragm (not shown) is clear. That is, since the distance from the point sound source to the peripheral portion varies depending on the azimuth, the square-shaped diaphragm 22 has a single shape like a circular diaphragm in which the distance from the point sound source to the peripheral portion is the same in all directions. It does not exhibit a resonance characteristic that it resonates remarkably at frequencies, and has a large number of resonance frequencies. Therefore, the rectangular vibration film 22 is
It has a sufficiently wide reproduction frequency band compared to a circular diaphragm. By intentionally shifting the heat shrinkage direction of the film material from the diagonal direction of the vibrating film 22, the vertical tensile tension applied to the upper and lower sides and the lateral tensile tension applied to the left and right sides are made independent of each other. The advantages derived from the film shape, such as freely realizing desired frequency characteristics in this manner, can be effectively utilized for the acoustic effect.

The vibrator 24 has a voice coil 25, one end of which is in contact with the center of the back surface of the vibrating membrane 22 via a piston plate 25a, and an inverted E-shape coaxially arranged on the other end of the voice coil 25. Volcano-shaped yoke 2 with a circular cross section
6, an annular magnet 27 sandwiched in the middle of the annular portion of the yoke 26, and a damper 28 connecting the side surface of the voice coil 25 and the end portion of the yoke 26. The vibration exciter 24 has a structure in which high efficiency is thoroughly achieved by strengthening the magnetic force, minimizing the magnetic gap, reducing the friction of the damper, and the like, and the vibration coil 24 is arranged along the yoke 26 in the voice coil 25 in the magnetic field formed by the annular magnet 27. When a voice current is applied, the voice coil 25 vibrates in the axial direction by the Fleming force generated in the voice coil 25, and the piston plate 25a
Is driven in the front-back direction.

Further, the piston plate 25a is not adhered to the vibrating membrane 22, but is simply brought into contact with the central portion of the back surface of the vibrating membrane 22. Therefore, the vibrator 24 needs to be separately held on the back surface side of the vibrating membrane 22. Therefore, in the present embodiment, the stay rod 29 is bridged between the central portions of the left and right sides of the support frame 23, and the vibrator 24 is fixed to the central portion of the stay rod 29. Thus, the vibrator 24 is pressed and held at the center of the back surface of the vibrating membrane 22. A skew adjusting mechanism (not shown) for adjusting the swinging angle of the vibrator 24 with respect to the stay rod 29 is incorporated in the central portion of the stay rod 29 so that the axis of the voice coil 25 can be adjusted orthogonally to the vibrating membrane 22. is there. Support frame 23
After the assembling of the vibrating membrane 22 with respect to the above, the both ends of the stay rod 29, to which the vibrator 24 is fixed in the central portion, are screwed and fixed to the rear surface of the support frame 23. In that case, the piston plate 25a at the tip of the voice coil 25 of the vibrator 24 contacts the center of the back surface of the vibrating membrane 22, but since the vibrating membrane 22 itself is pulled vertically and horizontally, the portion where the piston plate 25a abuts. It is assembled so as to be brought into contact with the vibrating membrane 22 with a pressing force that causes a displacement of about 1/2 of the maximum amplitude. Moreover, since the swing angle of the vibrator 24 with respect to the stay rod 29 can be freely adjusted by the skew adjustment mechanism, an adjustment jig (not shown) or the like is used to move the piston plate 25a in a direction perpendicular to the vibrating membrane 22. Can be adjusted to vibrate.

Speakers 18L and 18R having the above structure
When a voice current is applied to the voice coil 25, a Fleming force corresponding to the magnitude of the current and the number of coil turns is generated, and the vibrating membrane 22 is driven by the piston plate 25a in the front-back direction to generate sound pressure. To do. In this case, the vibrating membrane 22 itself is given tension and is tense, and vibrates with a slight pressing driving force, so that sufficient sound pressure can be generated only by supplying a minute driving current. Therefore, for example, in the case of the vibrating membrane 22 having an area of about A4 size, the output signal of the headphone output port can be directly energized and driven to the voice coil 25 without passing through the amplifier. From the experimental results, it is known that the sound pressure improving effect of the vibrating membrane 22 to which the tensile tension is applied exceeds several dB, and the sound pressure improving effect of about several dB accompanying the combined use of the high-sensitivity vibrator 24 is shown. Together, speaker 1
It is also known that the sound pressure can be improved by about 10 dB or more in the entire 8L and 18R.

Specifically, in the case of the conventional free-edge type flat speaker, it is driven through a speaker drive amplifier of about 1.2 W output for amplifying the headphone output.
Speakers 18L and 18R that drive the plate-sized diaphragm with tension applied to the diaphragm 22 can be driven by speaker drive amplifiers 17L and 17R with an output of about 0.2 W, and the reproduced sound obtained is It has been confirmed that sound pressure, frequency characteristics, and distortion rate are the same. That is,
A large driving force is not required to drive the speakers 18L and 18R, and the speaker drive amplifiers 17L and 17R that operate with the bus power supplied via the USB port 12a and the USB interface circuit 14 can sufficiently support the driving force. Thus, the USB compatible speaker drive system 11 shown in the present embodiment can supply both the audio signal and the power source to the speaker drive amplifiers 17L and 17R via the USB port 12a, and as described above, the dedicated power source 9 and the like are not used at all. It is unnecessary.

As described above, the USB speaker drive system 11 has speaker drive amplifiers 17L and 17L which are operated by the power source supplied through the USB port 12a.
Since R and the high-efficiency speakers 18L and 18R driven by the speaker drive amplifiers 17L and 17R are provided, it is possible to supply power to the speaker drive amplifiers 17L and 17R via the USB standard interface. That is, for example, 87 to 90d are applied to the speaker drive amplifiers 17L and 17R whose maximum current consumption is 0.1 A or less, even though the USB bus power is limited to DC 5 V and 0.1 A separately supplied from the USB interface circuit 14.
By using a combination of high-efficiency speakers 18L and 18R of about B / W, sufficient sound reproduction is possible, which eliminates the need for the dedicated power source 9 for the speaker drive amplifiers 17L and 17R, and abolishes the dedicated power source 9. It is possible to cut down the manufacturing cost involved. Further, for example, a USB port 12 provided in the portable personal computer main body 12 or the like
By connecting to a and using it, it can be used without being influenced by the power supply environment of the place of use, and it is very easy to reproduce the sound at the destination. Furthermore, even when the system is shipped overseas, there is no fear of being overwhelmed by various safety standards related to the power source in accordance with the domestic legislation of the destination, so quick response is possible. Thus, the speaker drive system is presented as one of the peripheral devices such as the personal computer main body 12 and the convenience as a hot plug that can be freely inserted and removed while the personal computer main body 12 is turned on is also provided. It is possible to meet a wide range of needs with extremely high versatility.

Further, the left channel audio signal is amplified by the speaker driving amplifier 17L composed of a non-inverting amplifier, and the right channel audio signal is amplified by the speaker driving amplifier 17R composed of an inverting amplifier. Can be performed by a pair of amplifiers that operate in opposite phases to each other, and the peak currents in the opposite phases cancel each other out, so that it is possible to suppress current consumption associated with speaker driving. Further, polarity management is required for connection between the speaker drive amplifiers 17L and 17R and the speakers 18L and 18R, but the output terminal of the speaker drive amplifier 17L is connected to the positive terminal of the corresponding speaker 18L to output the speaker drive amplifier 17R. The desired polarity can be easily managed by simply connecting the speaker cable accordingly, such as connecting the terminal to the negative terminal of the corresponding speaker 18R.

Further, speaker driving amplifiers 17L, 17R
Since the audio signal supplied via the USB port 12a is amplified, the power supply and the audio signal supplied via the USB port 12a are supplied to the speaker drive amplifiers 17L and 17R, so that a complicated cable It is possible to provide a speaker drive system that can perform good audio reproduction without connection and can use the personal computer main body 12 equipped with a CD player as if it were a line input.

In the above embodiment, both the signal and the power supply are supplied to the speaker driving system via the USB port 12a. However, as in the USB compatible speaker driving system 31 shown in FIG. The audio signal may be supplied from the USB port 12a attached to the personal computer main body 12 or the like, and the audio signal may be supplied from the external output terminal 12b attached to the personal computer main body 12. The USB compatible speaker driving system 31 shown in the present embodiment has been abolished because the decoding processing circuit 15 is unnecessary, and the external output terminal 12b attached to the personal computer main body 12 is connected to the external input terminal 32a by the audio cable 32. Then, the stereo audio signal input from the external input terminal 32a is directly input to the volume control circuit 1
It leads to 4. The external output terminal 12b attached to the main body 12 of the personal computer is an output terminal in a broad sense other than USB that outputs a sound signal to the outside, and here, an earphone output terminal is also included.

In the above embodiment, the left channel speaker drive amplifier 17L is composed of an inverting amplifier,
The speaker driving amplifier 17R for the right channel can be configured by a non-inverting amplifier, and in that case, the corresponding speaker 18
It is advisable to reverse the connection polarity for L and 18R.

[0028]

As described above, according to the present invention,
Since a speaker drive amplifier that operates by a power supply supplied through a USB port and a high efficiency speaker that is driven by this speaker drive amplifier are provided,
Power can be supplied to the speaker drive amplifier through the B standard interface, and even if the USB bus power is limited to DC5V and 0.1A, the maximum current consumption is 0.1A or less for the speaker drive amplifier. 90
By using a high efficiency speaker of about dB / W in combination, sufficient sound reproduction is possible, which eliminates the need for a dedicated power source for the speaker drive amplifier, and can reduce the manufacturing cost due to the elimination of the dedicated power source. Yes, and U provided in, for example, a portable personal computer main body
By connecting to the SB port, it can be used without being affected by the power environment of the place where it is used, and it is very easy to reproduce audio on the road, and also considers shipping the system overseas. Even if you do so, there is no fear of being overwhelmed by various safety standards related to the power supply according to the domestic legislation of the destination, so quick response is possible, thus driving the speaker as one of the peripheral devices such as the personal computer body. The system can be presented and the convenience as a hot plug that can be plugged in and unplugged while the power of the personal computer is turned on can be provided at the same time. It has excellent effects such as being able to respond to.

Further, the speaker drive amplifier is the U
Since the audio signal supplied via the SB port is amplified, by supplying the power and audio signal supplied via the USB port to the speaker drive amplifier,
Good audio reproduction is possible without a complicated cable connection, and it is possible to provide a speaker drive system in which a personal computer main body equipped with a CD player can be used as if it were a line input.

Further, the speaker drive amplifier is the U
Since the configuration is such that the audio signal supplied via the external output terminal other than the SB port is amplified, only the power is supplied from the USB port attached to the personal computer body or the like, and the audio signal is, for example, the personal computer body or audio equipment. It is possible to supply from an external output terminal such as the above, and thereby it is possible to provide various connection modes.

The present invention according to claim 4 has a structure in which the audio signal of one channel is amplified by the non-inverting amplifier and the audio signal of the other channel is amplified by the inverting amplifier. Driving can be performed by a pair of amplifiers that operate in opposite phase to each other, so that peak currents do not overlap and current consumption fluctuates significantly as in the case of in-phase driving. By canceling each other out, it is possible to suppress the current consumption that accompanies speaker drive, and polarity management is required for the connection between the speaker drive amplifier and the speaker, but the output terminal of the non-inverting amplifier is Connect the speaker terminal to the positive terminal and connect the output terminal of the inverting amplifier to the negative terminal of the corresponding speaker. An effect equal the desired polarity management alone can easily be connected accordingly Bull.

Further, since the non-inverting amplifier and the inverting amplifier respectively amplify the corresponding channel audio signal of the stereo signal supplied via the USB port, the power supply and the audio signal supplied via the USB port are provided. By supplying to the speaker drive amplifier, good audio reproduction is possible without complicated cable connection, and it is possible to provide a speaker drive system in which a personal computer main body equipped with a CD player can be used as if it were line input. Produce an effect.

Furthermore, since the non-inverting amplifier and the inverting amplifier respectively amplify corresponding channel audio signals of stereo signals supplied via the external output terminals other than the USB port, only the power source of the personal computer is required. The audio signal can be supplied from an external output terminal of a personal computer main body or an audio device, for example, and thus various connection modes can be provided.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a USB-compatible speaker driving system of the present invention.

2A and 2B are a vertical cross-sectional view and a front view of the speaker shown in FIG. 1, respectively.

FIG. 3 is a circuit configuration diagram showing another embodiment of the USB-compatible speaker driving system of the present invention.

FIG. 4 is a circuit configuration diagram showing an example of a conventional USB-compatible speaker driving system.

[Explanation of symbols] 11,31 USB speaker drive system 12 Personal computer body 12a USB port 12b External output terminal 13 USB cable 14 USB interface circuit 15 Decoding processing circuit 16 Volume control circuit 17L, 17R speaker drive amplifier 18L, 18R speaker 32 audio cable

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-11-27776 (JP, A) JP-A-2-188100 (JP, A) JP-A-10-51888 (JP, A) JP-A-7- 111698 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04R 3/00 310 G06F 1/18 H03F 3/181 H03F 3/68

Claims (4)

(57) [Claims] 1. A speaker drive amplifier which operates by power supplied through the USB port, Bei a high efficiency stereo speakers driven by the speaker drive amplifier
However, the speaker drive amplifier is one channel for stereo signals.
A non-inverting amplifier that non-inverts the audio signal of the channel
The audio signal of the other channel of the stereo signal is inverted and increased.
A high efficiency stereo speaker of the non-inverting amplifier.
The positive terminal is connected to the output terminal, and the one channel
A high-efficiency speaker for reproducing the audio signal of
The negative terminal is connected to the output terminal of the amplifier and the other
Second high-efficiency speaker for reproducing channel audio signal
A speaker driving system for USB, which is composed of: 2. The first and second high efficiency speakers,
Voice coil impedance must be 16Ω or more
The USB speaker drive system according to claim 1, wherein
Stem. 3. The first and second high efficiency speakers,
It is characterized by using a square tensile film for the diaphragm.
A speaker driving system for USB according to claim 1 or 2.
Mu. 4. The non-inverting amplifier and the inverting amplifier are
Connect the USB port or other external output terminal
Sound of the corresponding channel of the stereo signal supplied via
4. A voice signal according to claim 1, wherein the voice signal is amplified.
A USB speaker-driving system according to any one of the above.