JPH0555691U - An audio device that drives a speaker by PWM amplifying a digital audio signal - Google Patents

Abstract

(57) [Abstract] [Purpose] Shorten the distance between the power amplifier and the speaker to shorten the output line from the power amplifier, and perform high-efficiency power amplification with less heat generation due to higher output, and to perform complicated digital An audio device that does not require a speaker, but can fully demonstrate the advantages of digitizing audio signals and driving the speaker. A receiver 2 as an interface for receiving a digital audio signal from a source 11, a PWM converter 3 for converting a digital signal output from the receiver 2 into a PWM signal, and the PWM signal is amplified by class D amplification. The class D amplifier 4 is provided, and the output power from the class D amplifier 4 is passed through the LPF 5 to flow only the power component into the speaker 6 to drive the speaker 6.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention is an acoustic device for driving a speaker by PWM amplifying a digital audio signal used in an in-vehicle active speaker device, a PA active speaker device, a system active speaker device, a TV active speaker device, and the like.

[0002]

[Prior Art]

 In order to realize an audio device that is resistant to noise, it is desirable to process the digital audio signal as close as possible to the speaker drive section. However, since the signal reproduced by the speaker must be analog, the digital signal must be converted to an analog signal at some point. Therefore, a conventional audio device that converts a digital signal into an analog signal and drives a speaker has the following configuration.

First, as shown in FIG. 4, a digital signal is output from a source 11 such as a CD (compact disc) or a DAT (digital audio tape). This digital signal includes a sync signal, audio signal, user data bit, channel status bit, validity flag, and parity bit. The receiver 2, which is an interface between the source 11 and the audio amplifier 31, is a receiving unit for synchronizing the digital signal output from the source 11 with the inside of the audio amplifier 31, and normally outputs a 16-bit digital signal. . A DA (digital / analog converter) 21 converts a digital signal into an analog signal. The power amplifier 22 power-amplifies the analog signal converted by the DA 21 and drives the speaker 6. The audio amplifier 31 is provided with an equalizer, tone control, various kinds of filters and the like. An analog signal from the audio amplifier 31 to the speaker 6 becomes an analog signal and is connected by a lead wire.

Next, as shown in FIG. 5, the amplifier is separated into an audio preamplifier 32 and a speaker built-in amplifier 33. The digital signal from the source 11 is received by the receiver 2, and the receiver 2 outputs the digital signal to the DSP 23 at the next stage. The DSP 23 is a digital signal processing device, and digitally performs the processing such as tone control, loudness, and equalizer, which has been performed by analog until now. The transmitter 9 is a transmitter of a digital voice signal which outputs the input signal from the DSP 23 as a signal for transmission. The audio preamplifier 32 is provided with an equalizer, tone control, various filters and the like. The speaker built-in amplifier 33 includes a receiver 2, a DA 21, and a power amplifier 22. Therefore, it is not necessary to wire the lead wire for the speaker 6 with a thick cable as in the conventional case.

Further, as shown in FIG. 6, it is intended to directly drive a speaker with a digital signal. The digital signal is received by the receiver 2 and converted from a digital signal to an analog signal by the DA (digital / analog converter) 24, and the output is multi-bit. The output from the D-A 24 is amplified by the switches 26 _{1 to} 26n corresponding to each bit. The switches 26 _{1 to} 26 n are connected to the + power source or the −power source in accordance with the bit information. The digital speaker 25 is wound with 7 voices of 8 bits and 15 voice coils of 27 bits _{1 to} 27 _n-1 for 16 bits. That is, the number of voice coils corresponding to the number of bits is prepared. If it is 16 bits and 7 F FF, current flows in all voice coils in the positive direction, and if it is 8000, current flows in the negative direction, and the digital speaker 25 swings to its maximum amplitude. If the digital signal is 0000, no current flows in any voice coil.

[0006]

[Problems to be solved by the device]

 However, in the conventional example shown in FIG. 4, from the audio amplifier 31 to the speaker 6 are power-amplified analog signals, which are generally more resistant to noise and the like than the case of a small signal, but when the wiring is lengthened, etc. There are various problems to be considered such as the diameter of the lead wire, the weight, and the voltage drop. Next, in the conventional example shown in FIG. 5, in order to increase the output, there is a mechanical problem such as increasing the size of a heat sink as a heat countermeasure. Particularly in the case of a car, if the speaker built-in amplifier 33 is attached to the car door, it is necessary to close the speaker built-in amplifier 33 for waterproofing, which causes a problem of heat countermeasures. Further, in the conventional example shown in FIG. 6, it is necessary to prepare the number of voice coils corresponding to the bits, and there are many technical problems in achieving high accuracy. In other words, if the turns ratio corresponding to the bit is not accurate, it will not be acoustically linear, the number of voice coils will be large, and the structural and electrical accuracy of the boil coil will be difficult to obtain. There are many problems. As described above, in the conventional example, the merit of digitizing the audio signal and driving the speaker is not fully utilized.

The present invention has been made in view of such a point, and it is not necessary to lengthen the output line from the power amplifier 22, and it is also necessary to increase the size of a heat sink or the like for higher output. Furthermore, PWM amplification of the digital audio signal is performed, which does not require a digital speaker that prepares the number of windings corresponding to the bits, and the advantages of digitizing the audio signal and driving the speaker are fully exerted. It is an object of the present invention to provide an audio device that drives a speaker.

[0008]

[Means for Solving the Problems]

 In order to solve the above problems, an audio device for PWM driving a digital audio signal of the present invention to drive a speaker includes a receiver 2 as an interface for receiving the digital audio signal and a digital signal converted into a PWM signal. The PWM converter 3 and the class D amplifier 4 that amplifies the PWM signal by the class D amplification are provided, and are characterized by high efficiency and reduced external noise.

Further, another acoustic device for driving a speaker by PWM amplifying a digital audio signal of the present invention is a receiver 2 as an interface for receiving the digital audio signal, and a PWM converter 3 for converting the digital signal into the PWM signal. And a class D amplifier 4 for amplifying a PWM signal by class D amplification, and a speaker 6 is built in.

[0010]

[Action]

 The digital signal from the source 11 is received by the receiver 2 which is an interface between the source 11 and the audio amplifier 31, and is normally output as a 16-bit digital signal. A ΣΔ type, ΔΣ type, or other one-chip PWM converter 3 converts a digital signal into a PWM signal. The class D amplifier 4 amplifies the PWM signal by switching the power device in a pulse shape. After that, only the power component is flown into the speaker 6 through the LPF 5 to drive the speaker 6.

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings of FIGS. First, a first embodiment is shown in FIG. The receiver 2, which is an interface, is a receiving unit for synchronizing the digital signal output from the source 11 with the inside, and normally outputs a 16-bit digital signal. The PWM converter 3 is a one-chip converter such as a ΣΔ type or a ΔΣ type that converts a digital signal into a PWM signal. The PWM signal is used in the D-class amplification section 4 to switch the power device in a pulse shape to amplify the power device. It directly repeats on / off and drives only the power component into the speaker 6 through the LPF 5 to drive the speaker 6. Since the PWM output is obtained in this way, the speaker itself is driven in combination with the class D amplification.

A second embodiment is shown in FIG. An analog signal from the source 7, that is, the output of the tape, FM, AM and the analog signal output of CD, DAT, etc. is converted into a digital signal by an AD (analog / digital converter) 8. A signal for transmission is sent out from the converted signal by a transmitter 9 which is a transmitter of a digital audio signal. The rest is almost the same as the first embodiment of FIG. The PWM amplifier 10 has the functions of the PWM converter 3, the class D amplifier 4 and the LPF 5, and drives only the power component into the speaker 6 to drive the speaker 6. A DSP 23 that performs processing such as tone control, loudness, and equalizer can be installed at a position between the AD 8 and the transmitter 9 or a position between the receiver 2 and the PWM amplification unit 10.

A third embodiment is shown in FIG. A digital signal is output from the source 11 such as CD or DAT. A transmitter 9 which is a transmitter of this digital voice signal sends out a signal for transmission. The rest is almost the same as the first embodiment of FIG. The PWM amplifying unit 10 has the functions of the PWM converter 3, the class D amplifying unit 4 and the LPF 5, and drives only the power component into the speaker 6 to drive the speaker 6. Note that the DSP 23 that performs processing such as tone control, loudness, and equalizer can be installed at a position between the source 11 and the transmitter 9 or a position between the receiver 2 and the PWM amplification section 10. The degree of freedom increases.

[0014]

[Effect of the device]

 As described above, the audio device for PWM-amplifying the digital audio signal according to the present invention and driving the speaker is a receiver 2 as an interface for receiving the digital audio signal, and converts the digital signal into a PWM signal. A PWM converter 3 and a class D amplifier 4 that amplifies the PWM signal by class D amplification are provided. Further, another audio device of the present invention PWM-amplifies a digital audio signal to drive a speaker. A receiver 2 as an interface for receiving, a PWM converter 3 for converting a digital signal into a PWM signal, a class D amplifier 4 for amplifying the PWM signal by class D amplification, and a speaker 6 are built in. As a result, the part that is the conventional analog signal is greatly reduced, and the sound reproduction device is highly resistant to noise and highly efficient. Can be realized. Further, since it is a digital audio signal before it is converted into a PWM signal, the digital signal processing device may be placed at any position in FIG. 2 and FIG. 3, and the degree of freedom in device development is increased. Since the amplifying section also uses the switching operation, it is efficient and reduces structural problems such as heat sinks.

[Brief description of drawings]

FIG. 1 is a speaker driving system using PWM amplification according to a first embodiment of the present invention.

FIG. 2 is a speaker driving system using PWM amplification according to a second embodiment of the present invention.

FIG. 3 is a speaker driving system using PWM amplification according to a third embodiment of the present invention.

FIG. 4 is a schematic block diagram of an audio amplifier in a conventional example.

FIG. 5 is a schematic block diagram of an audio preamplifier and a speaker built-in amplifier in a conventional example.

FIG. 6 is a schematic explanatory diagram of a digital speaker system in a conventional example.

[Explanation of symbols]

 2 receiver 3 PWM converter 4 class D amplifier 5 LPF 6 speaker 7 source 8 AD 9 transmitter 10 PWM amplifier 11 source 21 DA 22 power amplifier 23 DSP 24 D-A 25 digital speaker 26 switch 27 voice coil 31 audio amplifier 32 audio Preamplifier 33 Speaker built-in amplifier 34 Digital speaker system

Claims (3)

[Scope of utility model registration request] 1. A receiver (2) as an interface for receiving a digital audio signal, a PWM converter (3) for converting a digital signal into a PWM signal, and a class D amplifier section (4) for amplifying the PWM signal by class D amplification. )
An acoustic device for driving a speaker (6) by PWM-amplifying a digital audio signal, which is characterized by high efficiency and reduced external noise. 2. The PW for digital audio signal according to claim 1, wherein the speaker (6) is built in.
An audio device that drives a speaker by amplifying M. 3. The acoustic device according to claim 1, further comprising a digital signal processing device, for PWM amplification of a digital audio signal to drive a speaker.