JPH09214265A - Power amplifier circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of sound interruption even if abnormality occurs in a power amplifier by connecting the output sides of first and second switching means to a second and first switching means-side on the opposite side, connecting a plural loads in series and connecting a third switching means to the middle point of the loads. SOLUTION: The output sides of the first and second switching means 7 and 8 are connected to the fixed contact point (c) of the second and first switching means 8 and 7 on the opposite side. The third switching means 10 whose one end is connected to reference potential is connected to the connection middle point of the first and second speakers 9A and 9B connected in series. When abnormality occurs in the first power amplifier 3, the first and second speakers 9A and 9B are connected in parallel to the second power amplifier 4, a load impedance viewed from the second power amplifier 4 is made 1/2, and driving power is doubled and the circuit is driven. Thus, the sound of output which is almost equal to that at normal time can be emitted. Then, the sense of incongruity is not given to a viewer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio power amplifier circuit, and more particularly to a power amplifier circuit suitable for use in concerts and the like.

[0002]

2. Description of the Related Art Two sets of SEPPs have been conventionally used as high-power audio power amplifier circuits that can be used in concerts and the like.
(Single Ended Push-Pull) circuit by an OTL (Output Transformer)
ess) configured to drive in reverse phase BTL (B
Since the balanced transform power amplifier circuit has a current-voltage utilization factor that is twice that of a normal SEPP circuit, it is widely used for obtaining a large output at a low voltage and for obtaining a high power.

FIG. 3 shows the configuration of such a BTL power amplification circuit. An input signal whose sound quality is adjusted by analog-converting data such as a compact disc (CD) as the sound source 2 is a BTL power amplification circuit. It is supplied to the first and second power amplifiers 3 and 4 which form the circuit. The first and second power amplifiers 3 and 4 are configured to drive in opposite phases.

The output terminals of the first and second power amplifiers 3 and 4 are connected to a relay having, for example, a single throw single pole type movable contact piece as the first and second switching means 7 and 8, and And the output ends of the second switching means 7 and 8 are speakers 9 as a load via output terminals T1 and T2.
It is connected to the. Although a monaural structure is shown in FIG. 3, two sets of left and right L and R speakers are arranged in a stereo structure.
It is configured to be driven by a pair of BTL amplifier circuits.

Further, in this BTL amplifier circuit, the first
Alternatively, and / or when an abnormality occurs in the second power amplifiers 3 and 4, the abnormality detection circuit 5 detects the abnormality, and based on this detection signal, the first and second switching means 7 and 8 via the switching control circuit 6. Is turned off, and a protection circuit for protecting the speaker from burning is installed.

However, in such a BTL power amplifier circuit, if the first or / and the second power amplifier 3 or 4 becomes abnormal during a concert or performance, the performance will be completely lost.
There was a problem that no sound was produced after being cut off from. In order to solve such a problem, Japanese Unexamined Patent Publication No. 2-86202 discloses that, even if one of the first and second power amplifiers is abnormal during the performance, the other power amplifier is replaced as shown in FIG. There is disclosed a power amplifier circuit configured so that the performance is not interrupted by using the power amplifier circuit.

This power amplifier circuit will be briefly described with reference to FIG. 4, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and duplicate description will be omitted. The input signal from the sound source 2 is supplied to the input circuit 11 which constitutes the BTL power amplification circuit 14. The input circuit 11 has a built-in phase inversion circuit that inverts the phase of the input signal, and outputs the anti-phase input signal to the first and second power amplifiers 3 and 4 to output the first and second switching means 7.
And 8 and output terminals T1 and T2 to the speaker 9.

First and second switching means 7 and 8
The electrode of the switch is a single throw bipolar type, and when the movable contact piece a is in contact with the fixed contact b, the first and second power amplifiers 3
When the movable contact pieces a of the first and second switching means 7 and 8 are in contact with the fixed contact c, the speaker 9 is connected to the ground (reference) potential. The first and second switching means 7 and 8 are controlled by the first and second protection circuits 12 and 13 to move the movable contact piece a of the switch to the fixed contact b or c side. Control switching.

The outputs of the first and second power amplifiers 3 and 4 are supplied to the input sides of the first and second protection circuits 12 and 13 and the muting circuit connected to the input terminals T3 and T4. The power-on timing signal is supplied to detect the abnormality of the first and second power amplifiers 3 and 4 and the abnormality of the power source, and at the time of detecting these abnormality, one of the switching means 7 or 8 is driven to drive the speaker terminal. Is dropped to the reference potential and the performance is continued by only one of the power amplifiers to prevent the interruption of the sound during the performance.

[0010]

According to the conventional structure shown in FIG. 4, the protection circuit operates when an abnormality occurs in the BTL power amplifier circuit for some reason or when the output current becomes larger than the allowable value. Then, the speaker terminal of one of the power amplifiers is dropped to the ground potential, and the other power amplifier that is operating normally is driven, so that the adverse effect of interrupting the reproduced sound during performance can be eliminated.

However, what has been driven and reproduced by the first and second power amplifiers up to now is suddenly output and reproduced with about half of the output level and 1/4 of the power output. It gives a feeling of strangeness to the person who is listening to the performance. Especially at concerts and the like, there is a problem that the abnormality of the loudspeaker is immediately known to the audience.

The present invention is intended to provide a power amplifier circuit which solves the above-mentioned problems, and its problem is that the power amplifier is designed so as not to cause sound interruption and not to make the viewer feel abnormal. To get the circuit.

[0013]

The power amplifier circuit according to the present invention, as an example of which is shown in FIG. 1, outputs the first and second power amplifiers 3 and 4 which output input signals in opposite phases. In the power amplifier circuit 1 configured to drive the loads 9A and 9B having substantially equal characteristics, which are connected in series to the sides via the first and second switching means 7 and 8, respectively. Loads 9A and 9B in which the respective output sides of the switching means 7 and 8 are connected to the fixed contacts c on the opposite side of the second and first switching means 8 and 7 and are connected in series.
The third switching means 10, one end of which is connected to the reference potential, is connected to the connection middle point of.

According to the power amplifier circuit of the present invention, for example, when an abnormality occurs in the first power amplifier 3, the first and second speakers 9A and 9B are connected in parallel to the second power amplifier 4. Since the load impedance viewed from the second power amplifier 4 is halved and the driving current is doubled for driving, it is possible to emit a sound having an output substantially equal to that in a normal state, so that the audience does not feel discomfort. You can play.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the power amplifier circuit 1 of the present invention will be described in detail below with reference to the system diagram of FIG. In the present example, the portions corresponding to those in FIG. 3 and FIG.

In FIG. 1, as a sound source 2, an input signal whose sound quality is adjusted by analog-converting data of a CD or the like is input to first and second power amplifiers 3 and 4 of BTL configuration which are driven in opposite phases. To be done. First and second power amplifier 3
The outputs of 4 and 4 are connected in series to the output terminals T1 and T2 via the fixed contacts b and the movable contact pieces a of the first and second switching means 7 and 8 and have two loads 9A and 9B having substantially equal impedances. Is connected to the speaker.

The third switching means 10 comprising, for example, a single-pole single-throw switch, one end of which is connected to the ground (reference) potential at the connection midpoint of the speakers 9A and 9B connected in series.
Is connected.

First and second switching means 7 and 8
Is a single throw double pole type switch, for example, and is composed of another fixed contact c.
Are connected to the movable contact pieces a of the switching means 8 and 7 on the opposite sides.

When an abnormality occurs in the first and second power amplifiers 3 and 4, the first and second abnormality detection circuits 5 and 5'are respectively the first and second switching control circuits 6 and 6 '. Via the first and second switching means 7 and 8
The movable contact piece a is controlled to be switched to the fixed contact c side so that the movable contact piece a
Are switched to the switching means 8 and 7 on the opposite side, and the first and second protection circuits 12 and 13 are configured to switch and control the third switching means 10.

The operation of this example with the above configuration will be described. First, when both the first and second power amplifiers 3 and 4 are operating normally, the first and second abnormality detection circuits 5 and 5 ′ have not detected an abnormality in the power amplification system path. The first and second switching control circuits 6 and 6'are in a non-operating state, and the movable contact piece a of the switching means 7 is in contact with the fixed contact b side. These switching means can normally be switching elements such as relays or transistors.

Further, the third switching means 10 is controlled by the first or second switching control circuit 6 or 6'so that it is kept in the normally open state, so that it is set to 2 during normal operation.
The two speakers 9A and 9B are connected in series and are driven by the first and second power amplifiers 2 and 3.

Therefore, the input signal from the sound source 2 is operated in reverse phase by the first and second power amplifiers 2 and 3, and the speakers 9A and 9B are BTL driven.

Next, when an abnormality occurs in the first power amplifier 3, the first abnormality detection circuit 5 detects the abnormality and outputs an abnormality signal to the first switching control circuit 6. Therefore, switching control is performed based on the control signal of the first switching control circuit 6 so that the movable contact piece a of the first switching means 7 is connected to the movable contact piece a of the second switching means 8 on the opposite side. At the same time, the midpoint of connection between the speakers 9A and 9B is grounded.

Of course, since the second power amplifier 4 side is operating normally, the movable contact piece a of the second switching means 8 is still connected to the fixed contact b side, and the second power amplifier 4 is connected to the second power amplifier 4 side. The input signal supplied from the sound source 2 is the fixed contact b of the second switching means 8 → the second switching means 8
Of the movable contact piece a → the fixed contact point c of the first switching means 7
→ Movable contact piece a of the first switching means 7 → Output terminal T
1 → first speaker 9A → third switching means 10
-> Ground (reference) potential-> The sound of the first speaker 9A is emitted by the normal second power amplifier 4 via the path of the ground potential of the sound source 2.

On the other hand, the input signal amplified by the second power amplifier 4 is fixed contact b of the second switching means 8 → second
Movable contact a of the switching means 8 → output terminal T2 → second speaker 9B → third switching means 10 → ground
The second speaker 9B is caused to emit sound by the normal second power amplifier 4 via the path of (reference) potential → ground potential of the sound source 2.

That is, the first and second speakers 9A and 9
B is connected in parallel to the second power amplifier 4, and the load impedance viewed from the second power amplifier 4 is halved and the drive current is doubled to drive. Since the sound can be emitted, it is possible to end the performance without making the audience feel uncomfortable.

When the second power amplifier 4 is abnormal, the second abnormality detecting circuit 5'detects an abnormality in the same manner as described above.
Abnormal voltage is output to the switching control circuit 6'of
The switching control circuit 6'of switches the movable contact piece a of the second switching means 8 to the fixed contact c side, and
Controlling the switching means 10 of the first power amplifier 3
The first and second speakers 9A and 9B are connected in parallel to the system path to drive the first and second speakers, respectively.

In each of the above-mentioned embodiments, the single type power amplifying circuit has been described. However, as a stereo power amplifying circuit, as shown in FIG. 2, two left and right power amplifying circuits 1L and 1R are provided for the stereo sound sources 2 and 2 '. Can be driven in parallel. In FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals and duplicate description is omitted, but first and second speakers 9A and 9B
The left and right speakers 9L and 9R may be respectively configured as one set.

According to the power amplifier circuit of the present invention, not only can the power amplifier and the speaker be prevented from being damaged when one of the BTL-configured power amplifiers is abnormal, but also when one of the power amplifiers is abnormal. The present invention has the effect that the other power amplifier can be driven without interruption of the sound, and the reproduction output is not lowered and can be played with the same output as in the normal state.

[0030]

According to the power amplifier circuit of the present invention, the BTL
Even if there is an abnormality in one of the power amplifiers in the configuration, not only does the playback output from the speaker be cut off and no sound breaks occur, but it is also possible to output a playback sound with approximately the same output as in the normal state, making the audience feel uncomfortable. A power amplification circuit that does not feel can be obtained.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a power amplifier circuit of the present invention.

FIG. 2 is a system diagram showing another embodiment of the power amplifier circuit of the present invention.

FIG. 3 is a system diagram of a conventional power amplifier circuit.

FIG. 4 is another system diagram of a conventional power amplifier circuit.

[Explanation of symbols]

 1 Power amplification circuit 2, 2'Sound source 3,4 First and second power amplifier 5,5 'First and second abnormality detection circuit 6,6' First and second switching control circuit 7,8th 1st and 2nd switching means 9A, 9B 1st and 2nd speaker (load) 10 3rd switching means 11 Input circuit 12, 13 1st and 2nd protection circuit 14 BTL

Claims (2)

[Claims] 1. A power amplifier circuit configured to drive a load on the output sides of first and second power amplifiers that output input signals in opposite phases to each other via first and second switching means, respectively. Where the output sides of the first and second switching means are respectively connected to the opposite second and first switching means sides, and the plurality of loads are connected in series and the plurality of connected loads are connected. A power amplifier circuit comprising a third switching means, one end of which is connected to a reference potential, connected to the middle point. 2. A speaker connected in series and having substantially equal characteristics is connected to the output end of a BTL amplifier circuit as a first load and a second load, and when an abnormality occurs in one of the amplifiers, the output end of the amplifier. The first or second load connected to is disconnected and the midpoint of the first and second loads connected in series is connected to a reference potential, and the first is disconnected from the output terminal of the amplifier in which the abnormality has occurred. A power amplifier circuit characterized in that a second load is connected to an output terminal of a normal amplifier to connect the first and second loads in parallel.