JP2003070090A - Audio power amplifier output control device - Google Patents

Abstract

(57) [Problem] To amplify an abnormal oscillation of an audio power amplifier without adversely affecting, for example, the phase and frequency characteristics of an audio audible band when amplifying an audio signal up to a frequency of about 100 kHz. An audio power amplifier output control device that amplifies an input signal to a predetermined power level to drive a speaker, comprising: a switch for turning on and off an audio power amplifier and a speaker; Oscillation detection means 12 for detecting an oscillation frequency component included in the output speaker drive signal;
A switch control means for controlling on / off of the switch means on the basis of an output from the oscillation detection means, and when the audio power amplifier is in abnormal oscillation, the switch is turned on (open).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output control device for an audio power amplifier, and more particularly to an output control device for an audio power amplifier suitable for handling audio signals up to 100 kHz band.

[0002]

2. Description of the Related Art An audio power amplifier is known as a power amplifier which receives a signal voltage which has been sufficiently amplified by a low level amplifier in advance as an input signal and amplifies the signal voltage mainly to a power level required for driving a speaker. Has been.

Due to recent advances in digital technology, SA
With the advent of CDs (super audio discs) and DVDs (digital video discs), reproduction of audio signals near the 100 kHz band is required in order to capture particularly high frequency sounds.

[0004]

When dealing with such high frequency signals, the audio power amplifier may cause abnormal oscillation due to itself or an external factor.

Oscillation is a fatal drawback in audio power amplifiers. Particularly, in the case of headphones, since the speaker unit is placed close to the ears, a situation in which listening cannot be endured occurs. In addition, with regard to the speaker, a situation occurs in which the tweeter or the like is destroyed.

Therefore, conventionally, assuming all external factors, a phase compensation circuit, a high frequency cut circuit and the like are adopted to cope with abnormal oscillation of the audio power amplifier.

However, in these conventional methods, the phase and frequency characteristics of the audio audible band are also changed, which causes another problem that the sound quality is deteriorated.

The present invention has been made to solve the above problems, and its purpose is to adversely affect the phase and frequency characteristics of the audio audible band when amplifying an audio signal up to near 100 kHz, for example. It is another object of the present invention to provide an output control device for an audio power amplifier, which can deal with abnormal oscillation of the audio power amplifier.

[0009]

In order to achieve the above object, the present invention provides an audio power amplifier output control apparatus for amplifying an input signal to a predetermined power level to drive a speaker. Switch means for turning on and off between the speaker, and oscillation detecting means for detecting an oscillation frequency component included in the speaker drive signal output from the audio power amplifier,
And a switch control means for on / off controlling the switch means based on the output from the oscillation detecting means.

According to this structure, if the audio power amplifier oscillates abnormally, the oscillation frequency component of the abnormal oscillation is detected by the oscillation detecting means, and the switch controlling means turns off (open) the switching means. , The speaker drive signal is cut off.

In the present invention, the oscillation detecting means preferably comprises a high-pass filter that passes only the oscillation frequency component (for example, 600 kHz or more), and a rectifying circuit that converts the output of the high-pass filter into a DC voltage. According to this, the presence or absence of abnormal oscillation can be monitored by the voltage value output from the rectifier circuit. The oscillation detecting means may be a frequency counter.

The switch control means preferably has a predetermined delay time in order to prevent switch chattering. That is, when the oscillation frequency component disappears and the switch means is switched from off to on, the switch means may be switched from off to on after a lapse of a predetermined delay time from the time when the oscillation frequency component disappears.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to FIG.

According to this output control device, an output signal (speaker drive signal) of the audio power amplifier 10 is provided between the audio power amplifier 10 and a speaker (not shown).
A switch 11 for turning on and off is provided. Switch 1
1 may be a semiconductor switch, a relay switch, or the like that is commonly used.

Further, this output control device has an oscillation detecting means 12 connected to the output side of the audio power amplifier 10.
And a controller 13 as a switch control means for receiving the output of the oscillation detection means 12 and controlling the on / off of the switch 11.

In this embodiment, the oscillation detecting means 12
Is a high-pass filter (high-frequency pass filter) 12
1 and a rectifier circuit 122 that rectifies the high-frequency signal that has passed through the filter 121 and returns it to a DC voltage.

The high-pass filter 121 detects a high-frequency signal component contained in the output signal of the audio power amplifier 10 when the audio power amplifier 10 abnormally oscillates. In this embodiment, the pass frequency band is 600 kHz or more. A frequency counter may be used instead of the high pass filter 121.

When the audio power amplifier 10 is operating normally and no high frequency signal component is detected by the high pass filter 121, the controller 13 turns on (closes) the switch 11.

On the other hand, when the audio power amplifier 10 abnormally oscillates or high frequency noise enters due to an external factor, those high frequency signal components pass through the high pass filter 121 and the rectifying circuit 122 of the next stage. Is rectified by the controller 13 as a DC voltage.
Given to.

The controller 13 has its DC voltage Va.
Is compared with a preset reference voltage Vs, and when the result is Va> Vs (or Va ≧ Vs), the switch 11 is turned off (open).

When the abnormal oscillation of the audio power amplifier 10 is stopped or high frequency noise disappears, Va <Vs
When (or Va ≦ Vs), the controller 13 turns on the switch 11.

In this case, in order to prevent the chattering of the switch 11, the controller 13 turns on the switch 11 after a predetermined time elapses after Va <Vs, for example. That is, the controller 13 has a predetermined delay time when the switch 11 is turned from off to on.

While the switch 11 is off, the sound output from the speaker is cut off. However, abnormal oscillation of the audio power amplifier 10 and external high frequency noise are often not maintained for a long time. It does not cause much trouble.

[0024]

As described above, according to the present invention,
By providing the switch means between the audio power amplifier and the speaker and detecting the abnormal oscillation of the audio power amplifier by the oscillation detecting means to turn off (open) the switch means, for example, up to about 100 kHz band. When amplifying the audio signal of, the abnormal oscillation of the audio power amplifier can be dealt with without adversely affecting the phase / frequency characteristics of the audio audible band.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an audio power amplifier output control device according to the present invention.

[Explanation of symbols]

10 audio power amplifier 11 switch 12 Oscillation detection means 121 High-pass filter 122 Rectifier circuit 13 Controller (switch control means)

Continued front page    F-term (reference) 5D020 AC01                 5J092 AA02 AA41 CA54 CA61 FA18                       HA38 KA46 KA51 KA63 MA20                       SA05 TA01 VL08                 5J500 AA02 AA41 AC54 AC61 AF18                       AH38 AK46 AK51 AK63 AM20                       AS05 AT01 LV08

Claims (4)

[Claims] 1. An output control device for an audio power amplifier which amplifies an input signal to a predetermined power level to drive a speaker, and switch means for turning on / off between the audio power amplifier and the speaker, and the audio power. An oscillation detecting means for detecting an oscillation frequency component included in the speaker drive signal output from the amplifier, and a switch control means for controlling ON / OFF of the switch means based on the output from the oscillation detecting means are provided. Output control device for audio power amplifier. 2. The output of the audio power amplifier according to claim 1, wherein the oscillation detection means includes a high-pass filter that passes only the oscillation frequency component and a rectifier circuit that converts the output of the high-pass filter into a DC voltage. Control device. 3. The output control device for an audio power amplifier according to claim 1, wherein the oscillation detecting means comprises a frequency counter. 4. The switch control means turns off the switch means after a predetermined delay time elapses from the time when the oscillation frequency component disappears when the oscillation frequency component disappears and the switch means is switched from off to on. The output control device of the audio power amplifier according to claim 1, wherein the output control device is switched from ON to ON.