JPH0621731A - Power amplifier utilizing sigmadelta modulation and speaker system - Google Patents

Abstract

PURPOSE:To facilitate the circuit integration and adoption of a low voltage power supply by binarizing an analog input signal with a SIGMADELTA modulator provided to an analog signal input section and amplifying the power of the signal with a class D amplifier so as to attain MOS structure. CONSTITUTION:A SIGMADELTA modulator 1 and a class D amplifier 2 constitute a power amplifier utilizing SIGMADELTA modulation. An analog input signal is subjected to SIGMADELTAmodulation by the modulator 1 and a 1-bit digital signal is outputted, the power is amplified by the class D amplifier 2 and one-bit digital power is outputted. Then the signal is demodulated into an analog signal by a low pass filter(LPF) 3 and an analog power is supplied to a load 4. Then the LPF 3 is omitted by providing the characteristic of the LPF to the load 4, and when a speaker is adopted for the load 4, the speaker system is realized with excellent performance. Since the modulator 1 is realized by MOSD structure, the modulator is suitable for circuit integration and since the class D amplifier 2 requires no heat sink, the size is made small and the cost is reduced and the amplifier copes easily with a low voltage power supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifying device using .SIGMA..DELTA. Modulation used for sound amplification or the like.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional PWM (Pulse Width Modu
3 is a block diagram for explaining the operation principle of the amplifier. Analog input signal is PAM by sampling 31
(PulseAmplitude Modulation), then hold 3
Retained PAM by 2. The held PAM and the comparison wave generated by the comparison wave generation 34 are compared by the comparison 33 and PW
M is output. This PWM signal is the switching element 5
The power is amplified by the signal, is demodulated to the original analog by the low-pass filter 3, and is supplied to the load 4. 6 is the PW of FIG.
It is a waveform diagram until M output. Analog input signal A is PA
It is converted to M, is held PAM, and is compared with the comparison wave S. When the held PAM is larger than the comparison wave S, the output becomes high level, and the PWM output as shown in the figure is obtained.

[0003]

However, the conventional PWM
Although the amplifier uses a method such as sampling, it is basically an analog operation, so the accuracy of the comparison wave and the comparator easily affect the overall performance. There was a problem that it was difficult to make something like this. Further, from the viewpoint of each function, it is difficult to form a MOS structure, and the cost is high in the case of an IC, which is not an advantageous method. Further, there is a problem that it is not possible to easily realize a low-voltage power supply, which has been attracting attention in recent years.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power amplification device that solves the above problems. Another object of the present invention is to provide a speaker system that solves the above problems.

[0005]

In order to solve the above-mentioned problems, a power amplification device using ΣΔ modulation according to the present invention is provided with a ΣΔ modulator in an analog signal input section, and outputs from this ΣΔ modulator. It is characterized in that an analog signal is converted into a binarized power signal and amplified by using the binarized signal as the input signal of the class D amplifier. In order to solve the above-mentioned problems, the speaker system according to the present invention is
It is characterized by including the power amplification device.

[0006]

The analog signal input section of the power amplifier has a ΣΔ modulator, and the ΣΔ modulator binarizes the analog input signal. The class D amplifier power-amplifies the binarized signal. As a result, the MOS structure and the IC can be easily formed, and the low voltage power supply can be easily applied.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The power amplification device using ΣΔ modulation according to the present invention does not amplify the PWM modulation output by the class D amplifier, but amplifies the ΣΔ modulated output. Figure 3
FIG. 4 is a block diagram for explaining an outline of a ΣΔ modulator used in the present invention. With this, the same function is realized. The analog input signal is divided by the clock pulse, and the waveform which is integrated by the integrator 11 and has a step shape is input to the comparator 13 via the integrator 12. This input waveform is compared with a reference value by the comparator 13 and binarized. 1 bit D / A delayed by the delay circuit 14
It is input to the converter 15. Up to this 1-bit D / A conversion, it is sensuously analog. A similar signal is output by integrating in the integrator 16, and is added as a minus in the adder 12 to reduce the amount of information. These are compared, and 1-bit digital output is made as a 1-bit ON / OFF signal. This is a so-called PWM signal.

FIG. 4 is a block diagram for explaining the outline of the second-order ΣΔ modulator used in the present invention. The description is omitted because it is basically the same as that of FIG.
This is a second-order ΣΔ-type modulator in which the number of 1's is increased to make the integration two stages. When the order is increased, theoretically, even if the sampling frequency is lowered, the same accuracy as before the order is increased can be obtained. Therefore, if the order is increased, the accuracy is improved without increasing the sampling frequency. Theoretically, doubling the sampling frequency improves the accuracy of 1 bit. However, when the sampling frequency is increased, the problem of the speed of the switching element appears. Further, if the frequency is high, high precision is required for all circuits, the circuit configuration becomes difficult, and the selection of devices is limited.

FIG. 1 is a block diagram of an embodiment of the present invention, showing the configuration of a class D amplifier utilizing ΣΔ modulation. That is, the 1-bit digital output in FIGS. 3 and 4 is demodulated into an analog signal through the low-pass filter as in the PWM modulation. In the figure, a ΣΔ modulator 1 and a class D amplifier 2 constitute a power amplification device using ΣΔ modulation according to the present invention. An analog input signal is ΣΔ modulated by a ΣΔ modulator 1 to generate a 1-bit digital signal. The output is performed, the power is amplified by the class-D amplifier 2 and 1-bit digital power is output, the analog demodulation is performed by the low-pass filter 3, and the analog power is supplied to the load 4. Further, the low-pass filter 3 can be omitted by providing the load 4 itself with the characteristics of the low-pass filter. Further, by making the load 4 a speaker, it is possible to exhibit excellent performance as a speaker system. The ΣΔ modulator 1 is suitable for IC since it is easy to form a MOS structure. Also, class D amplifier 2
Usually does not require a heat sink which is usually added to a power amplifier, and therefore has many advantages such as downsizing of shape, cost reduction, and easy handling. The low-pass filter 3 is a passive filter, and is a circuit composed of only passive elements such as LCR.

FIG. 2 is a block diagram of an embodiment of the present invention. The class D power amplifier of FIG.
Other than that, it is exactly the same as the others. In this way, by using ΣΔ modulation, MOS structure can be realized, problems in IC formation can be solved, and accuracy can be dealt with by increasing the order of the ΣΔ modulator, and the sampling frequency can be increased (oversampling). You can avoid the technical difficulties caused by increasing the ratio). As an advantage, a heat sink for a power amplifier is not required, single power supply operation is possible, and the ΣΔ modulator can be easily integrated into an IC. A wide range of applications such as speakers, underwater amplifier speakers, and commercial amplifiers can be considered.

[0011]

As described above, ΣΔ according to the present invention
A power amplification device using modulation includes a ΣΔ modulator in an analog signal input section, and a binarized signal output from the ΣΔ modulator is used as an input signal of a class D amplifier to convert the analog signal into two signals. Since the signal is converted into a power signal and amplified, the MOS structure can be realized, the IC can be easily formed, and the accuracy can be coped with by increasing the order of the ΣΔ modulator. It is not necessary to make a comparison wave and a comparison wave, and it is easy to deal with low voltage power supply.

Further, the speaker system using ΣΔ modulation according to the present invention is provided with the above-mentioned power amplifying device, so that the same effect can be exhibited.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of an embodiment of the present invention.

FIG. 3 is a block diagram for explaining an outline of a ΣΔ modulator used in the present invention.

FIG. 4 is a block diagram for explaining an outline of a second-order ΣΔ modulator used in the present invention.

FIG. 5 is a block diagram for explaining the operation principle of the PWM amplifier.

FIG. 6 is a waveform diagram for explaining the operation principle of the PWM amplifier.

[Explanation of symbols]

 1 ΣΔ modulator 2 Class D amplifier 3 Low-pass filter 4 Load 5 Switching element 11 Integrator 12 Accumulator 13 Comparator 14 Delay circuit 15 1-bit D / A converter 16 Integrator 21 Integrator 22 Accumulator 23 Comparator 24 Delay Circuit 31 Sampling 32 Holding 33 Comparison 34 Comparison wave generation A Analog input signal S Comparison wave

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[Procedure amendment]

[Submission date] February 18, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Change

[Correction content]

Title: Power amplification device and speaker system using ΣΔ modulation

Claims (2)

[Claims] 1. An analog signal input section is provided with a ΣΔ modulator, and a binarized signal which is an output from the ΣΔ modulator is D
A power amplifying device using ΣΔ modulation, which converts an analog signal into a binarized power signal and amplifies it by using it as an input signal of a class amplifier. 2. A speaker system comprising the power amplification device according to claim 1.