JP2003198281A - Audio signal amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an audio signal amplifier using a D-class amplifier, capable of preventing the problem of the radiation being generated from a long metal wiring, leading to a loudspeaker. <P>SOLUTION: The audio signal amplifier is provided with an PWM (pulse width modulation) circuit 32 for converting an analog signal from digital equipment into a pulsed analog electrical signal, an electrical-to-optical transducer circuit for converting the pulsed analog electrical signal into an optical signal, an optical fiber cable 34 for transmitting the optical signal, an optical-to- electrical transducer circuit 36 for converting the optical signal from the cable 34 into a pulsed analog electrical signal, a driver 37 in a D class mode upon receiving the signal from the circuit 36, and an LPF (low-pass filter) 38 for converting the signal from the driver 37 into an analog signal. The output of the LPF 38 is used as the input of the loudspeaker. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an audio signal amplifier. In particular, the present invention relates to an audio signal amplifier having a D class amplifier function that operates in the D class.

[0002]

2. Description of the Related Art D-class amplifiers are being used in audio equipment as amplifiers capable of outputting a large output with a small loss. It is suitable for small equipment because it does not require a large radiator even if the output is large.

FIG. 7 shows the configuration of a conventional audio signal amplifier using a D class amplifier. The amplifier 1 receives the analog signal from the analog signal input terminal 2 and
An LPF (low pass signal) is passed through a drive circuit 4 for driving a pulsed analog electric signal PWM-converted by an M (pulse width modulation) circuit 3 in a D class operation.
The filter 5 removes high frequency components. A long metal wiring cable 8 electrically connects between the LPF 5 and the speaker 11 to drive the speaker 11 in the speaker box 12. Reference numeral 7 is a ground terminal of the amplifier 1, 6 is a cable connection terminal, and 9 and 10 are speaker drive terminals.

[0004]

However, in the conventional audio signal amplifier using the D class amplifier,
The high frequency component of the PWM (pulse width modulation) pulse is L
Since it is not sufficiently attenuated by the PF (low pass filter) 5, there is a problem that radiation occurs from a long metal wiring leading to the speaker. Therefore, it is an object of the present invention to provide an audio signal amplifying apparatus using a D class amplifier capable of preventing such a problem that radiation occurs from a long metal wiring leading to a speaker.

[0005]

In order to achieve the above object, in the present invention, an electro-optical converting means for converting a pulsed analog electrical signal into an optical signal, an optical transmitting means for transmitting the optical signal, and the optical signal Photoelectric conversion means for converting the optical signal from the transmission means into a pulsed analog electric signal, drive means for receiving the pulsed analog electric signal from the photoelectric conversion means and operating in D class, and pulse from the drive means An audio signal amplifier having means for converting an analog electric signal into an analog signal. As a result, the speaker cable can be connected by an optical cable as a light and inexpensive optical transmission means, and radiation can be prevented from occurring from a long metal wiring leading to the speaker. Furthermore, the influence of external contact resistance can be eliminated as compared with the case of using a metal cable.

Further, if a means for converting an analog signal into a pulsed analog electric signal is provided before the electro-optical converting means, even for an input from a digital device having no pulsed analog signal such as PWM. The audio signal amplification device can be used.

Further, if the electro-optical converting means for converting the pulsed analog electric signal into the optical signal is mounted in the light emitting side connector of the light transmitting means, a part of the separated devices can be integrated and the audio signal amplification. The device can be connected easily.

If means for converting the analog signal into a pulsed analog electric signal and electro-optical conversion means for converting the pulsed analog electric signal into an optical signal are mounted in the light emitting side connector of the light transmitting means. , The input from a digital device having no PWM circuit (pulse width modulation circuit) can be dealt with, and a part of the separated devices can be integrated to simplify the connection of the audio signal amplifying device.

Photoelectric conversion means for converting the optical signal from the optical transmission means into a pulsed analog electric signal,
Drive means for receiving a pulsed analog electric signal from the photoelectric conversion means and operating in the D class; and analogizing means for converting the pulsed analog electric signal from the drive means into an analog signal, If it is mounted in the light-receiving side connector, a part of the separated devices can be put together and the connection of the audio signal amplifying device can be simplified.

Photoelectric conversion means for converting the optical signal from the optical transmission means into a pulsed analog electric signal,
Drive means for receiving a pulsed analog electric signal from the photoelectric conversion means to operate in the D class; analogizing means for converting the pulsed analog electric signal from the drive means into an analog signal; and a speaker connected to the analog converting means. , A power source means is housed in a speaker housing means, the photoelectric conversion means is provided with a photoelectric conversion element and a direct current component detecting means, and the power source means is turned on / off by a direct current component detected by the direct current component detecting means. If the switch means is provided, the audio signal amplification device can be easily handled.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit block diagram showing the connection between the audio signal amplifier 50 of the first embodiment according to the present invention and a conventional digital device. Conventional digital device 1
3 demodulates the digital signal from the storage element 14 with the demodulator 15, and the delta sigma (ΔΣ) modulator (circuit)
Digital / analog conversion is performed at 16. LPF (low
The pass filter 17 removes the high frequency component of the analog signal and outputs it.

The audio signal amplifying apparatus 50 of the first embodiment according to the present invention comprises an amplifier 31, a speaker box 35 as a speaker accommodating means, and an optical cable 34 as a light transmitting means for connecting the both. Amplifier 3
1 receives the analog output from the digital device 13,
PWM that is a means for converting to a pulsed analog electric signal
It comprises a (pulse width modulation) circuit 32 and an electro-optical conversion circuit 33 including an electro-optical conversion element as an electro-optical conversion means for receiving the pulsed analog electric signal and converting it into an optical signal.
The speaker box 35 operates in the D class by receiving a photoelectric conversion circuit 36 including a photoelectric conversion element as photoelectric conversion means for converting an optical signal from the optical cable 34 into a pulsed analog electric signal and receiving the pulsed analog electric signal. A driver 37 as a drive means, an LPF (low pass filter) 38 which is also means for converting a pulsed analog electric signal from the driver 37 into an analog signal,
The speaker 39 connected to this is housed. Further, as shown in FIG. 3, the photoelectric conversion means 36 is provided with a DC component detection means 36b connected to the photoelectric conversion element 36a and an amplifier 36c. The power supply unit 44 is provided with a trigger circuit 40 for turning on / off the power supply unit 42 by the DC component detected by the DC component detection unit 36b, and a switch 41 operated by the trigger circuit 40. In this example, the external power supply 43 is connected to the power supply unit 42 via the switch 41.

FIG. 3 shows an example of a concrete circuit of the photoelectric conversion circuit 36. The optical signal received by the photo diode (PD) 36a is converted into an electric signal and the DC component is sent to the trigger circuit 40 through the low pass filter 36b as the DC component detecting means. The amplifier 36c amplifies the signal from the photo diode (PD) 36a and supplies its output to the driver 37.

When the power of the amplifier 31 side is turned on and an optical signal is sent to the optical cable, the switch 41 generates a direct current component in the photoelectric conversion element of the photoelectric conversion circuit configured as shown in FIG. 3, and the direct current component is turned on to turn on the speaker. The power supply unit 42 in the box 35 is turned on. Thereby, the manual power switch on the speaker box side can be omitted.

Since the driver 37 operates as a D-class amplifier, an element having a fast rise time that responds to the PWM signal is required. Up to the output of the driver 37, the pulsed analog electric signal is returned to the analog signal by the LPF 38 and drives the speaker 39. Since the driver 37 and the speaker 39 can be arranged in the vicinity, radiation is unlikely to occur, and the characteristics of the LPF 38 can be simple without taking a filter structure having multiple stages.

Further, if the voice coil of the speaker unit 39 is made by suppressing high frequency radiation, the unit may be directly driven without passing through the LPF.

FIG. 2 is a circuit block diagram showing the connection between the audio signal amplifier according to the second embodiment of the present invention and a new conventional digital device. In the conventional digital device 18, the demodulator 15 demodulates the digital signal from the storage element 14, and the delta-sigma (ΔΣ) modulator 16 performs digital-analog conversion to output.

For such a digital device, the amplifier 29 having only the electro-optical conversion circuit 33 is replaced by the amplifier 3 shown in FIG.
It can be used instead of 1. In this case, the circuit on the light receiving side may be exactly the same as that in FIG. 1, and the driver operating in the D class also operates normally.

FIG. 4 is a circuit block diagram showing a portion of an audio signal amplifying apparatus of a third embodiment according to the present invention, particularly a terminal portion on the speaker side which can be used for headphones or the like. The power supply unit 42 is a battery here and has the same basic function as the circuit in the speaker box 35 of FIG. 1, and therefore the corresponding components are denoted by the same reference numerals as in FIG. This circuit is incorporated in the headphones 51, and the headphones 51 are connected to a digital device by an optical fiber cable.

FIG. 5 is an explanatory view showing an example of a circuit mounted in the light emitting side connector 34a of the optical fiber cable 34 as the light transmitting means in the present invention. Digital device 1
PWM circuit (pulse width modulation circuit) 32 for converting the analog signal from 3 into a pulsed analog electric signal, and electro-optical conversion circuit 3 for converting the pulsed analog electric signal into an optical signal
3 are mounted in the light emitting side connector 34a of the light transmitting means. As a result, a part of the separated devices can be integrated with the optical fiber cable 34, and the connection of the audio signal amplifying device can be simplified.

FIG. 6 is an explanatory view showing an example of a circuit mounted in the light receiving side connector 34b of the optical fiber cable 34 as the light transmitting means in the present invention. A photoelectric conversion circuit 36 for converting an optical signal from an optical fiber cable 34 as an optical transmission means into a pulsed analog electric signal, a driver 37 which receives the pulsed analog electric signal from the photoelectric conversion means and operates in a D class, A low-pass filter 38, which is an analogizing means for converting the pulsed analog electric signal from the driver 37 into an analog signal, is mounted in the light-receiving side connector 34b of the light transmitting means. As a result, a part of the separated devices can be integrated with the optical fiber cable 34, and the connection of the audio signal amplifying device can be simplified.

By using the above-described structure shown in FIGS. 5 and 6 as the light emitting side connector and the light receiving side connector of the optical fiber cable 34, a part of the device further separated is integrated with the optical fiber cable 34. They can be put together and the audio signal amplifier can be connected easily. The configurations of FIGS. 5 and 6 described above can be particularly easily handled when a small speaker such as headphones is used.

[0024]

As described above, according to the present invention, the wiring connection cable of the audio signal amplifier having the D class amplifier function which operates in the D class can be an optical fiber cable, and the radiation does not occur. In addition, noise can be prevented by eliminating the influence of electrical contact resistance.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a connection between an audio signal amplifier according to a first embodiment of the present invention and a conventional digital device.

FIG. 2 is a circuit block diagram showing a connection between an audio signal amplifier according to a second embodiment of the present invention and a conventional digital device.

FIG. 3 shows an example of a specific circuit of a photoelectric conversion circuit 36 used in the present invention.

FIG. 4 is a circuit block diagram showing a portion of an audio signal amplifier according to a third embodiment of the present invention, particularly a speaker side terminal portion that can be used for headphones and the like.

FIG. 5 is an explanatory view showing an example of a circuit mounted in a light emitting side connector of an optical fiber cable as a light transmitting means in the present invention.

FIG. 6 is an explanatory diagram showing an example of a circuit mounted in a light receiving side connector of an optical fiber cable as a light transmitting means in the present invention.

FIG. 7 is a circuit block diagram showing a configuration of an audio signal amplifier using a conventional D class amplifier.

[Explanation of symbols]

13,18 Digital devices, 14 Storage elements, 1
5 demodulator, 16 delta-sigma (ΔΣ) modulator (circuit), 17 LPF (low pass filter), 29,
31 amplifier, 32 PWM (pulse width modulation) circuit, 3
3 electro-optical conversion circuit, 34 optical cable (optical fiber cable), 34a light emitting side connector, 34b light receiving side connector, 35 speaker box, 36 photoelectric conversion means (photoelectric conversion circuit), 36a photoelectric conversion element (photo diode (PD)), 36b DC component detecting means, 36c
Amplifier, 37 driver, 38 LPF (low pass
Filter), 39 speakers (speaker unit), 4
0 trigger circuit, 41 switch, 42 power supply section, 43
External power supply, 44 power supply means, 50 audio signal amplifier, 51 headphones.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5D020 AC01                 5J092 AA02 AA41 AA56 AA66 CA41                       FA20 HA19 HA25 HA29 HA38                       HA44 KA00 KA42 KA47 KA53                       KA55 KA61 KA62 KA63 TA01                 5J500 AA02 AA41 AA56 AA66 AC41                       AF20 AH19 AH25 AH29 AH38                       AH44 AK00 AK42 AK47 AK53                       AK55 AK61 AK62 AK63 AT01                 5K002 AA01 AA03 DA05 FA01 GA07

Claims (6)

[Claims] 1. An electro-optical converting means for converting a pulsed analog electrical signal into an optical signal, an optical transfer means for transferring the optical signal, and an optical signal from the optical transfer means for converting the optical signal into a pulsed analog electrical signal. Audio signal amplification including photoelectric conversion means, drive means for receiving a pulsed analog electric signal from the photoelectric conversion means to operate in D class, and means for converting the pulsed analog electric signal from the drive means into an analog signal apparatus. 2. The audio signal amplifying apparatus according to claim 1, further comprising means for converting an analog signal into a pulsed analog electric signal before the electro-optical converting means. 3. The audio signal amplifying device according to claim 1, wherein an electro-optical converting means for converting the pulsed analog electric signal into an optical signal is mounted in a light emitting side connector of the light transmitting means. 4. A means for converting the analog signal into a pulsed analog electric signal and an electro-optical conversion means for converting the pulsed analog electric signal into an optical signal are mounted in a light emitting side connector of the light transmitting means. The audio signal amplifying device according to claim 2. 5. A photoelectric conversion means for converting the optical signal from the light transmission means into a pulsed analog electric signal, and D receiving the pulsed analog electric signal from the photoelectric conversion means.
2. A drive means operating in a class and an analogizing means for converting a pulsed analog electric signal from the drive means into an analog signal are mounted in a light receiving side connector of the light transmitting means. 5. The audio signal amplification device according to any one of 4 to 4. 6. A photoelectric conversion means for converting the optical signal from the optical transmission means into a pulsed analog electric signal, and D receiving the pulsed analog electric signal from the photoelectric conversion means.
The drive means operating in the class, the analogization means for converting the pulsed analog electric signal from the drive means into an analog signal, the speaker connected thereto, and the power supply means are housed in the speaker housing means, and 2. A photoelectric conversion element and a direct current component detecting means are provided in the converting means, and a switch means for turning on / off the direct current component detected by the direct current component detecting means is provided in the power source means.
5. The audio signal amplification device according to any one of 4 to 4.