JPH05275944A - Power amplifier and voice generator - Google Patents

Abstract

PURPOSE:To provide a power amplifier and a voice generator which can prevent such a defective case where the deterioration of output and the increase of the output distortion are caused by a faulty power amplifier part serving as the load of another power amplifier part and therefore can assure a safe operation when plural power amplifier parts are used in parallel with each other. CONSTITUTION:The power amplifier parts 2 and 8 where the same input signals are supplied are provided together with the primary coils 31 and 33, and a secondary coil 32. The outputs of the parts 2 and 8 are inputted to the coils 31 and 32 and then the synthetic output is acquired at the coil 32 by an output transformer 3. In such a constitution of a power amplifier, the switch means R2 and R12 which are turned on and off in response to the presence or absence of conduction of the power supply to the parts 2 and 8 are provided between each cold side of both coils 31 and 33 and a reference potential point. Thus it is possible to prevent such a case where the part 2 functions as the load of the part 8 and causes the deterioration of output and the output distortion even though the power supply of the part 2 is cut off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier and a voice generator, and more particularly to a power amplifier used in commercial and emergency broadcasting facilities and a voice generator using the power amplifier.

[0002]

2. Description of the Related Art In broadcasting facilities for business use and emergency use, a large output power amplifier is required in order to supply audio signals and the like to a large number of speakers arranged in a building.

For this reason, in the conventional broadcasting equipment, one amplifier is configured by connecting two or more power amplifiers in parallel as shown in FIG. 3, or a plurality of speaker loads are connected by connecting the amplifiers in parallel. The whole system was configured to be compatible with.

In the example of one amplifier shown in FIG. 3, an audio signal is input to the terminal 1, and the audio signal is supplied to the amplifying unit 2 while being supplied to the other amplifying unit 8. Amplifier 2
Is composed of a driver 21 that amplifies an audio signal and an output transistor 22 whose output is a base input, and a DC voltage is supplied from the power supply rectifier circuit 6 to the collectors of the driver 21 and the transistor 22. A reverse voltage absorbing diode 23 is connected between the collector and emitter of the transistor 22. The emitter of the transistor 22 is connected to one end of the primary coil 31 of the output transformer 3, and the other end of the primary coil 31 is connected to the reference potential point via the fuse 4.

The same applies to the amplification section 8, which is composed of a driver 81 and an output transistor 82.
And the collector of the transistor 82 has a power supply rectifying circuit 10
DC voltage is supplied from. A reverse voltage absorbing diode 83 is connected between the collector and emitter of the transistor 82. The emitter of the transistor 82 is connected to one end of the other primary coil 33 of the output transformer 3,
The other end of the primary coil 33 is connected to a reference potential point via a fuse 9.

Audio outputs obtained at both ends of the secondary coil 32 of the output transformer 3 are output to output terminals T and T ', and a plurality of speakers 5 connected in parallel to the output terminals T and T'.
1, ..., 5n are supplied at the same time.

The power supply rectifier circuit 6 supplies an AC voltage (100 V) from a commercial AC power supply to a primary coil of a power transformer 63 through a power switch 61 and a power fuse 62, and converts the voltage from the secondary coil of the AC coil. The voltage is rectified and smoothed by the full-wave rectifier circuit 64 and the smoothing capacitor 65 to obtain a DC voltage (for example, 24V).

Similarly, the power supply rectifying circuit 10
An AC voltage (100V) from a commercial AC power supply is supplied to a primary coil of a power transformer 103 through a power switch 101 and a power fuse 102, and an AC voltage converted from the secondary coil is converted into a full-wave rectifier circuit 104 and a smoothing capacitor. It is rectified and smoothed by 105, and a DC voltage (for example, 2
4V).

Further, an emergency power supply circuit 7 is connected in parallel to the output terminal of the power supply rectification circuit 6. This emergency power supply circuit 7 is provided with a DC voltage (for example, 24 VDC) from a DC power supply such as a battery.
V) is output through the reverse voltage blocking diode 71. Similarly, in the power supply rectifying circuit 10, an emergency power supply circuit 11 is connected in parallel to the output terminal of the circuit 10. Similarly, the emergency power supply circuit 11 outputs a DC voltage (for example, 24 V) from a DC power supply such as a battery through the reverse voltage blocking diode 111. The power switches 61 and 101 are adapted to be turned on in conjunction with each other, and normally these switches are turned on.

Considering a state in which a DC voltage is supplied from the power supply rectifier circuits 6 and 10 to the amplifying units 2 and 8 in the above configuration, the audio signal input to the terminal 1 is amplified by the amplifying units 2 and 8. Primary coil 31 of output transformer 3, respectively
33, and the combined output of the two amplified outputs is obtained from both ends T and T'of the secondary coil 32. This secondary side output is simultaneously supplied to a plurality of speakers 51, ..., 5n connected in parallel, and is output as voice.

By the way, in the above apparatus, when a plurality of amplifying units 2 and 8 are operated in parallel in order to supply electric power to a large-capacity load, the output transistor 22 of one amplifying unit 2 and the like are operated. When an overcurrent flows through the primary side coil 31 due to the destruction, the primary side fuse 4 is blown to open the primary side so that the damage does not spread to the other amplification section 8. However, the power fuse 6
When the power supply voltage of one amplification unit 2 drops due to disconnection of 2, the primary side coil 31 cannot be opened, and the amplification unit 2 whose power supply has dropped becomes a load on the other amplification unit 8. However, there arises a problem that the output and sound quality are deteriorated, and in the worst case, the entire device is broken down.

[0012]

In the conventional device, when the power supply to one of the amplifiers is cut off due to the disconnection of the power supply fuse, the primary coil of the output transformer connected to the amplifier cannot be opened, and There is a problem that the dropped amplifier becomes a load on the other amplifier.

Therefore, the present invention is intended to solve the above problem, and even when a plurality of amplifying units are operated in parallel, safe operation can always be performed, and there is a risk that output will decrease and voice distortion will increase. It is an object of the present invention to provide a power amplifier which does not have a power amplifier and a voice generating device using the power amplifier.

[0014]

A power amplifier according to the present invention comprises a plurality of amplifying sections to which the same input signal is supplied, a plurality of primary side coils and a secondary side coil, and the plurality of primary side coils are provided. Output transformers for respectively receiving outputs from the plurality of amplifiers and obtaining a combined output in the secondary side coil, and provided between each cold side of the plurality of coils on the primary side of the output transformer and a reference potential point. And a plurality of switch means for turning on and off in accordance with the presence / absence of power supply to the plurality of amplifying units.

[0015]

In the present invention, when the power of one of the plurality of amplifiers is cut off for some reason, the cold side of the primary coil of the output transformer connected to the amplifier whose power is cut off and the reference Since the switch means placed between the potential points is turned off, the primary side of the output transformer is opened and the impedance seen from the secondary side (output side) becomes high impedance. Therefore, even if the power supply of one amplification unit is cut off, the power supply cut-off amplification unit does not become a load on the remaining amplification unit, and problems such as output reduction can be improved.

[0016]

EXAMPLES Examples will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a power amplifier and a voice generating apparatus using the power amplifier according to an embodiment of the present invention.

In FIG. 1, the same members as those in FIG. An audio signal is input to the terminal 1, and the audio signal is supplied to the amplifying unit 2 while being supplied to another amplifying unit 8. The amplifying unit 2 includes a driver 21 that amplifies an audio signal and an output transistor 22 whose output is a base input. The driver 21 and the collector of the transistor 22 are supplied with a DC voltage from the power supply rectifier circuit 6. A reverse voltage absorbing diode 23 is connected between the collector and emitter of the transistor 22. The emitter of the transistor 22 is connected to one end of the primary coil 31 of the output transformer 3, and the other end of the primary coil 31 is connected to the reference potential point via the fuse 4 and the electromagnetic relay contact R2 in series.

The same applies to the amplifying section 8, which is composed of a driver 81 and an output transistor 82.
And the collector of the transistor 82 has a power supply rectifying circuit 10
DC voltage is supplied from. A reverse voltage absorbing diode 83 is connected between the collector and emitter of the transistor 82. The emitter of the transistor 82 is connected to one end of the other primary coil 33 of the output transformer 3,
The other end of the primary coil 33 is connected to a reference potential point via a fuse 9 and an electromagnetic relay contact R12.

Audio outputs obtained at both ends of the secondary coil 32 of the output transformer 3 are output to output terminals T and T ', and a plurality of speakers 5 connected in parallel to the output terminals T and T'.
1, ..., 5n are supplied at the same time.

The power supply rectifier circuit 6 supplies an AC voltage (100 V) from a commercial AC power supply to a primary coil of a power transformer 63 through a power switch 61 and a power fuse 62, and a voltage-converted AC from the secondary coil. Obtains the voltage and rectifies it with the full-wave rectifier circuit 64 and smoothing capacitor 65.
Smoothing is performed to obtain a DC voltage (for example, 24V). Further, in this embodiment, the electromagnetic relay coil R1 is connected in parallel to both ends of the smoothing capacitor 65. The relay coil R1 and the relay contact R2 constitute one electromagnetic relay. A diode 12 for absorbing reverse voltage is connected in parallel to the electromagnetic relay coil R1.

Similarly for the power supply rectifying circuit 10,
An AC voltage (100V) from a commercial AC power supply is supplied to a primary coil of a power transformer 103 through a power switch 101 and a power fuse 102, and a voltage-converted AC voltage is obtained from the secondary coil to obtain a full-wave rectifier circuit 104. And a smoothing capacitor 105 to rectify and smooth the DC voltage (for example, 24V). Furthermore, in this embodiment,
An electromagnetic relay coil R11 is connected in parallel to both ends of the smoothing capacitor 105. The relay coil R11 and the relay contact R12 constitute another electromagnetic relay. A reverse voltage absorbing diode 13 is connected in parallel to the electromagnetic relay coil R11.

Further, an emergency power supply circuit 7 is connected in parallel to the output terminal of the power supply rectification circuit 6. This emergency power supply circuit 7 is provided with a DC voltage (for example, 24 VDC) from a DC power supply such as a battery.
V) is output through the reverse voltage blocking diode 71. Similarly, in the power supply rectifying circuit 10, an emergency power supply circuit 11 is connected in parallel to the output terminal of the circuit 10. Similarly, the emergency power supply circuit 11 outputs a DC voltage (for example, 24 V) from a DC power supply such as a battery through the reverse voltage blocking diode 111. The power switches 61 and 101 are adapted to be turned on in conjunction with each other, and normally these switches are turned on.

Considering a state in which a DC voltage is supplied from the power supply rectifier circuits 6 and 10 to the amplifiers 2 and 8 in the above configuration, the audio signal input to the terminal 1 is amplified by the amplifiers 2 and 8. Primary coil 31 of output transformer 3, respectively
33, and the combined output of the two amplified outputs is obtained from both ends T and T'of the secondary coil 32. This secondary side output is simultaneously supplied to a plurality of speakers 51, ..., 5n connected in parallel, and is output as voice.

Here, if the power supply of one amplification unit 2 is cut off for some reason (such as the disconnection of the power supply fuse 62), the cold side of the primary coil 31 of the output transformer connected to the amplification unit 2 and the reference potential point. Since the electromagnetic relay contact R2 in the gap is broken, the primary coil 31 of the output transformer is opened, and the impedance seen from the secondary side (output side) becomes high impedance. That is, the primary coil 3
It is higher than the impedance on the secondary side that appears when a rated load is connected to unit 1. As a result, the power fuse 62
When the power is cut off, the amplifying unit 2 with the power cut off does not become a load on the other amplifying unit 8.

As a modification of the embodiment described above, 2
It is conceivable that two secondary coils are provided corresponding to each of the primary coils 31 and 33, and electromagnetic relay contacts R2 and R12 are arranged between one end of these secondary coils and the reference potential point, respectively. However, in the emergency broadcasting equipment, the speakers 51, ..., 5n, which are loads, are often installed outdoors, and if an electromagnetic relay contact is brought to the secondary side of the output transformer 3 as described above. The surge voltage due to a lightning strike enters the electromagnetic relay contact on the secondary side through the outdoor speaker wiring, and eventually enters the paired electromagnetic relay coil on the power source side, which leads to the destruction of the power source side circuit.

On the other hand, as in the above-described embodiment of the present invention, the electromagnetic relay contacts R2 and R12 are arranged between the cold side of the primary side coils 31 and 33 of the output transformer and the reference potential point. Then, the surge voltage due to lightning strike is safe because it does not extend from the secondary side to the primary side due to the insulating function of the transformer.

In the above embodiment, the case where two amplifying units are used in parallel has been described, but it goes without saying that the present invention can be applied to the case where two or more amplifying units are used in parallel.

FIG. 2 shows another embodiment of the present invention. In the embodiment of FIG. 1, the case where two primary side coils 31 and 33 are wired to one output transformer 3 has been described, but in FIG. 2, the output transformers 3 and 3 ′ are connected to the power amplifiers 12 and 13. The secondary side coils 32 and 34 of the output transformers 3 and 3'are connected to the output terminals T and T ', respectively.
Is connected in parallel with. That is, each of the output transformers 3 and 3'is connected to the power amplifiers 12 and 13 having a plurality (two in the figure) of amplification units via a plurality (two in the figure) of primary side coils. Reference numerals 2 and 2'represent an amplifying section which constitutes the power amplifier 12, and an electromagnetic relay contact R2.
, R2 'are turned on and off at the same time by the electromagnetic relay coil R1. The power amplifier 12 may have one amplification unit or more amplification units connected in parallel. Further, 14 is an emergency power supply unit, and S
Reference numerals 1 and S2 are relay contacts that are used for making emergency broadcasts during power outages. Even with this configuration, the power amplifiers 12 and 13 can obtain the same operations and effects as those in FIG. It should be noted that more power amplifiers can be connected in parallel.

In the above embodiment, a contact switch using an electromagnetic relay is used as the switch means arranged in the primary coil of the output transformer, but the present invention is not limited to this and a contactless switch such as a semiconductor switch. Needless to say, may be used.

[0030]

As described above, according to the present invention, when one amplifier unit or amplifiers are used in parallel and one amplifier unit or amplifier is stopped due to power failure, The remaining amplifiers or amplifiers are not loaded, the output drop and the output distortion increase can be reduced, and the failure of the remaining amplifiers or amplifiers can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a power amplifier and a voice generating apparatus using the power amplifier according to an embodiment of the present invention.

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

FIG. 3 is a circuit diagram showing a conventional power amplifier and a voice generator using the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Input signal terminal 2, 8 ... Power amplification part 3 ... Output transformer 5 ... Speaker 6, 10 ... Power supply rectification circuit 7, 11 ... Emergency power supply circuit 31, 33 ... Primary side coil 32 ... Secondary side coil R1 ... Electromagnetic relay Coil R2 ... Electromagnetic relay contact R11 ... Electromagnetic relay coil R12 ... Electromagnetic relay contact

Claims (3)

[Claims] 1. A plurality of amplifiers to which the same input signal is supplied, a plurality of primary side coils and a plurality of secondary side coils are provided, and outputs from the plurality of amplifiers are input to the plurality of primary side coils, respectively. The secondary side coil is provided with an output transformer for obtaining a combined output, and the primary side of the output transformer is provided between each cold side of the plurality of coils and a reference potential point to supply power to the plurality of amplifiers. A power amplifier, comprising: a plurality of switch means that are turned on and off depending on the presence or absence of the power amplifier. 2. A plurality of amplifiers to which the same input signal is supplied, a plurality of primary side coils and a plurality of secondary side coils are provided, and the outputs from the plurality of amplifiers are input to the plurality of primary side coils, respectively. The secondary side coil is provided with an output transformer for obtaining a combined output, and the primary side of the output transformer is provided between each cold side of the plurality of coils and a reference potential point to supply power to the plurality of amplifiers. A power amplifier comprising a plurality of switch means for turning on and off depending on the presence or absence; a speaker to which the output of the secondary coil of the output transformer is supplied; a commercial AC power supply is rectified to generate a predetermined DC voltage. A plurality of power supply rectification circuits which are created and used as a power supply to the plurality of amplification units; 3. A plurality of amplifiers to which the same input signal is supplied, a plurality of primary side coils and a plurality of secondary side coils are provided, and outputs from the plurality of amplifiers are input to the plurality of primary side coils respectively. The secondary side coil is provided with an output transformer for obtaining a combined output, and the primary side of the output transformer is provided between each cold side of the plurality of coils and a reference potential point to supply power to the plurality of amplifiers. A power amplifier comprising a plurality of switch means for turning on and off depending on the presence or absence; a speaker to which the output of the secondary coil of the output transformer is supplied; a commercial AC power supply is rectified to generate a predetermined DC voltage. A plurality of power supply rectifier circuits that are created and used as power supplies to the plurality of amplifier units; an emergency power supply circuit that is connected in parallel to each output terminal of the plurality of power supply rectifier circuits and supplies a DC voltage to the plurality of amplifier units And equipped with; Sound generating apparatus according to claim and.