JPH11274863A - Switching amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching amplifier reducing spurious radio wave radia tion and improving power converting efficiency. SOLUTION: Concerning the switching amplifier for comparing an input signal S1 with a reference signal S3 and outputting a sound from a speaker based on a pulse width modulating signal outputted as a result, this amplifier has a signal working part 11 for inputting the input signal S1 from the outside and being capable of cutting off the high frequency component of this input signal S1, reference signal oscillating part 13 capable of changing the oscillation frequency of the reference signal S3, comparator 14 for comparing the input signal S1 with the reference signal S3 and outputting a signal S4 as a result, modulation part 15 for outputting a pulse width modulate signal S5 based on the result signal S4 and output part 16 for extracting only an audio signal component from the pulse width modulate signal S5 and outputting it to a speaker 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a switching amplifier, and more particularly to a switching amplifier for reproducing music in a vehicle.

[0002]

2. Description of the Related Art In recent years, various devices have been devised in response to demands for miniaturization and weight reduction of audio equipment mounted on, for example, passenger cars. On the other hand, in particular, the power supply output is limited in audio equipment for vehicles (for example, 12
V) Therefore, higher efficiency of audio equipment is required. FIG. 4 is a system diagram showing an example of a switching amplifier used in a conventional on-vehicle audio device. The switching amplifier 1 will be described with reference to FIG.

The switching amplifier 1 shown in FIG. 4 comprises a sawtooth wave oscillating section 3, a comparator 4, a modulating section 5, an output section 6, a speaker 7, and the like. The sawtooth oscillating unit 3 is connected to the comparator 4, and the comparator 4 is connected to the modulation unit 5. The modulation section 5 is connected to the output section 6, and the output section 6 controls the output of the speaker 7. The comparator 4 receives the input signal S
And the reference saw wave sent from the saw wave oscillator 3
The result of the comparison is sent to the modulator 5. The modulation unit 5 sends a pulse width modulation signal to the output unit 6 based on the comparison result. The output unit 6 outputs a speaker 7 according to the pulse modulation signal.
, And the speaker 7 outputs music to the outside.

[0004]

The switching amplifier 1 described above has the property that, when the oscillation frequency of the reference sawtooth wave is set higher for the signal being reproduced, the distortion factor of the reproduced signal can be reduced. ing. On the other hand, in the audio equipment mounted on a vehicle, the oscillation frequency of the reference sawtooth wave is set to the highest frequency that can be reproduced as sound, so the oscillation frequency of the reference sawtooth wave is set to a very high frequency. However, when the reference sawtooth wave is set at a high frequency, the unnecessary radiation level radiated from the audio device 1 is increased, and distortion (rounding) of the pulse modulation signal at the output unit 6 in which the angle is taken occurs. As a result, there is a problem that the reactive power of the audio device is increased and the power conversion efficiency is deteriorated.

Accordingly, an object of the present invention is to provide a switching amplifier which solves the above-mentioned problems, reduces unnecessary radiation, and improves power conversion efficiency.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a switching system for comparing an input signal with a reference signal and outputting sound from a speaker based on a pulse width modulation signal output as a result. In the amplifier, a signal processing unit capable of receiving an input signal from the outside and cutting off a high-frequency component of the input signal, and a reference signal oscillating unit capable of outputting a reference signal and changing an oscillation frequency of the reference signal And a comparator that is connected to the signal processing unit and the reference signal oscillation unit, compares the input signal with the reference signal, and outputs a result signal, and is connected to the comparator and output from the comparator. A modulation unit that generates a pulse width modulation signal based on the resulting signal, and an output unit that is connected to the modulation unit, extracts only a sound signal component from the pulse width modulation signal, and outputs the sound signal component to a speaker. The switching amplifier that is achieved.

According to the present invention, it is possible to change the processing conditions of the signal processing unit to which the input signal is input and to change the frequency of the sawtooth wave output to the comparator. Thus, the frequency band of the sound output from the speaker can be changed according to the user's selection, and the audio device can be efficiently controlled.

[0008]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 shows a system diagram of a preferred embodiment of the switching amplifier of the present invention. The switching amplifier 10 will be described in detail with reference to FIG. The switching amplifier 10 of FIG.
1, switching section 12, reference signal oscillation section 13, comparator 1
4, a modulator 15, an output unit 16, a speaker 17, and the like.

The switching unit 12 is, for example, a button or a switch which can be operated by a user, and is, for example, an operation unit for driving a vehicle-mounted subwoofer. The switching unit 12 is connected to the signal processing unit 11 and the reference signal oscillating unit 13, and the operations of the signal processing unit 11 and the reference signal oscillating unit 13 are controlled according to the operation status of the switching unit 12. The signal processing unit 11 has a built-in low-pass filtering circuit, and can cut off high-frequency components of the input signal S1 such as a music signal. The operation of the signal processing unit 11 is controlled by the switching unit 12, and the signal processing unit 11
Operates, the processing signal S2 is sent to the comparator 14 by passing only the low frequency component of the input signal S1.

The reference signal oscillating section 13 is connected to the comparator 14 and sends the comparator 14 a sawtooth wave having a predetermined frequency. The reference signal oscillator 13 has a function of switching the oscillation frequency of the sawtooth wave. The change of the oscillation frequency of the reference signal oscillating unit 13 is controlled by the switching unit 12, and the reference signal oscillating unit 13 changes the oscillation frequency based on the signal sent from the switching unit 12 to change the sawtooth wave S3.
To the comparator 14.

The comparator 14 is, for example, a comparator, and is connected to the signal processing section 11 and the sawtooth oscillating section 13 as described above. The comparator 14 receives the input signal S
1 and the sawtooth wave S3 are compared with each other, and the result signal S4 is sent to the modulation section 15. The modulation unit 15 outputs the result signal S
3 to generate a pulse width modulation waveform. The pulse width modulation waveform S5 is a voltage necessary for driving an output transistor described later. The modulation unit 15 is connected to the output unit 16, and the output unit 16 has a plurality of output transistors and a carrier removal filter. The output unit 16 removes a carrier component from the pulse width modulation waveform S5 by a carrier removal filter, and outputs only a sound signal to the speaker 17.

Next, the operation of the switching amplifier 10 will be described in detail with reference to FIG. The input signal S1
Is a music signal, for example, having a frequency band of 20 Hz to 20 kHz. In the following operation, for example, when the user wants to use the low-frequency subwoofer as the speaker 17, the switching unit 12 is turned off.
When N is set, and the user wants to use the mid-high range speaker, the switching unit is turned off. First, the switching unit 12
Is in the OFF state, the signal processing unit 11 does not operate, and the signal processing unit 11 sends the high frequency component of the input signal S1 to the comparator 14 without interruption.

On the other hand, the reference signal oscillating section 13 receives the input signal S1.
In order to perform pulse width modulation with sufficient performance on a high frequency band (for example, 20 kHz), the frequency is, for example, 250 kHz.
The z saw wave S3 is sent to the comparator 14. And the comparator 14
Compares the input level of the input signal S1 with the input level of the sawtooth wave S3 and sends a result signal S4 to the modulation unit 15, and the modulator 15 processes the result signal S4 into a pulse width modulation signal. The output unit 16 receiving the pulse width modulation signal S5 outputs the signal S5
Is sent to the speaker 17 and the speaker 17 outputs music. FIG. 2 shows the pulse width modulation signal S5 at the output unit 16 at this time. In FIG. 2, when switching is performed at a high frequency, the rising edge P1 and the falling edge P2 of the pulse width modulation signal S5 are rounded, and reactive power is generated at a portion where the waveforms overlap.

Next, when the user turns on the switching unit 12 when using the subwoofer, the switching unit 12
Operates the signal processing unit 11. First, the signal processing unit 11
Cuts off the high-frequency component of the input signal S1 by a low-pass filter circuit, and sends a processed signal S2 composed of only frequency components of 200 Hz or less to the comparator 14, for example, of the music signal. on the other hand,
The reference signal oscillator 13 sets the frequency of the oscillating sawtooth wave S3 to 50.
The frequency is changed to kHz and sent to the comparator 14.

The comparator 14 in FIG. 1 compares the signal level of the processing signal S2 with the signal level of the sawtooth wave S3. As a result, for example, when the level of the processing signal S2 is high, the comparator 14
vel (for example, 12 V), and outputs a result signal S4 that becomes Low-Level (for example, 0 V) to the modulation unit 15 when the level of the processing signal S2 is low. The modulator 15 receiving the result signal S4 from the comparator 14 outputs
A pulse width modulation signal S5 necessary for driving the output transistor of the above is generated, and the output section 16 sends only the music signal component to the speaker 17 based on the signal S5 to output a sound. At this time, the pulse width modulation signal S5 output from the output unit 15 is shown in FIG. In FIG. 3, the pulse width modulation signal S5 has a low frequency, so that the pulse width modulation signal S5 has a small rounding, the overlapping portion of the pulse width modulation signal S5 is small, and the reactive power is reduced. Thereby, the power conversion efficiency can be improved. In addition, the unnecessary radiation level can be reduced by the lower frequency.

According to the above embodiment, unnecessary radiation radiated from a device under a certain use condition is reduced by automatically selecting a switching operation frequency suitable for a user use condition, and power conversion efficiency is improved. it can. Further, by reducing unnecessary radiation, interference or influence on other electronic devices can be reduced, and improving power conversion efficiency is very useful for vehicles having limited power.

By the way, the present invention is not limited to the above embodiment. In the above embodiment, the signal processing unit 11
Is ON for the low-pass filter whose cutoff frequency is fixed
Signal processing unit 11 having a function of only / OFF, but having a low-pass filter whose cutoff frequency is continuously variable
It may be. Corresponding to this, the reference signal oscillating section 13 may have an oscillating frequency continuously variable. At this time, the cutoff frequency of the signal processing unit 11 and the oscillation frequency of the reference signal oscillation unit 13 are changed by the switching unit 12.
Is controlled by In the above embodiment, the switching amplifier is described as being mounted on a vehicle. However, the switching amplifier may be used in a home audio device, a portable audio device, or the like. Further, the reference signal oscillating unit 13 oscillates a sawtooth wave as a reference signal, but may oscillate a triangular wave.

[0019]

As described above, according to the present invention,
It is possible to provide a switching amplifier that reduces unnecessary radiation waves and improves power conversion efficiency.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a preferred embodiment of a switching amplifier of the present invention.

FIG. 2 is a waveform diagram showing a pulse modulation signal in a state where a switching unit is turned off in the switching amplifier of the present invention.

FIG. 3 is a waveform diagram showing a pulse modulation signal in a state where a switching unit in the switching amplifier of the present invention is turned on.

FIG. 4 is a system diagram showing an example of a conventional switching amplifier.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Switching amplifier, 11 ... Signal processing part, 12 ... Switching part, 13 ... Reference signal oscillation part, 14 ... Comparator, 15 ... Modulation part, 16 ...
Output unit, 17 ... speaker.

Claims (3)

[Claims] A switching amplifier for comparing an input signal with a reference signal and outputting sound from a speaker based on a pulse width modulation signal output as a result of the comparison. A signal processing unit that can block high-frequency components; a reference signal oscillation unit that outputs a reference signal and can change the oscillation frequency of the reference signal; and a signal processing unit and a reference signal oscillation unit that are connected to the signal processing unit. A comparator that compares the signal sent from the signal processing unit with the reference signal and outputs a result signal; and a comparator that is connected to the comparator and that is based on the result signal output from the comparator. A modulation unit that generates a pulse width modulation signal, and an output unit that is connected to the modulation unit and extracts only a sound signal component from the pulse width modulation signal and outputs the sound signal component to a speaker. Switching amplifier. 2. The signal processing unit according to claim 1, wherein the signal processing unit is connected to a switching unit operated by a user, and the signal processing unit cuts off a high frequency component of the input signal by operating the switching unit. Switching amplifier. 3. The switching amplifier according to claim 1, wherein the reference signal oscillating unit is connected to the switching unit, and changes the frequency of the reference signal by operating the switching unit.