JP3446039B2 - Power supply for power amplifier and power amplifier using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for a power amplifier (power amplifier circuit) and a power amplifier driven by this power supply.

[0002]

2. Description of the Related Art FIG. 6 shows a switching power supply 10 as a conventional power supply for a power amplifier, and this switching power supply 10
FIG. 3 is a circuit diagram of a power amplifier 20 driven by a drive voltage given by and a speaker 30 driven by the power amplifier 20. The switching power supply 10 is an AC filter / rectifying / smoothing unit 102 that AC filters and rectifies and smoothes an AC power supplied from a pair of input terminals 101.
And a converter transformer 103 in which an input voltage generated by the AC filter / rectifying / smoothing circuit 102 into a direct current is applied to the primary winding 103a, and this converter transformer 10
3 a switching transistor 104 as a switching element connected to the other end side, and a converter transformer 10
3 is connected between both ends of the secondary winding 103b,
The voltage induced between both ends of 03b is the DC drive voltage + Vc
Rectifying and smoothing circuit 105 for converting to c-Vcc and outputting.
And a control circuit 106 that detects the magnitude of one driving voltage + Vcc and controls the on / off operation of the switching transistor 104 in response to this detection signal. In the switching power supply 10, the AC filter rectifying / smoothing circuit 102, the converter transformer 103, the switching transistor 104, and the rectifying / smoothing circuit 105 generate driving voltages + Vcc and −Vcc for driving the power amplifier 20. The control circuit 106 controls the driving voltage + Vc based on the detection signal corresponding to the magnitude of the driving voltage.
c, -Vcc are controlled to be constant. Since the operation of the switching power supply 10 is well known, its detailed description is omitted.

The power amplifier 20 includes a drive voltage receiving unit 201 to which a drive voltage + Vcc is applied and a drive voltage -Vcc.
And a drive voltage receiving unit 202 to which the input signal is given, and an audio signal as an input signal given to the input unit is amplified and output as an output signal from the output unit. In the power amplifier 20, specifically, the emitter and the base of each of the npn transistor and the pnp transistor are connected in common, the drive voltages + Vcc and -Vcc are supplied to the collectors of each, and the connected base is an audio signal. Is configured as an input section of the power amplifier 20 and the commonly connected emitter serves as an output section of the amplified audio signal. The audio signal is applied to the input section of the power amplifier 20 via the input terminal 203. . The audio signal thus amplified by the power amplifier 20 is converted into audio by the speaker 30 and output.

[0004]

In the power amplifier 20 driven by the switching power supply 10 described above, the power amplifier 20 shown in FIG.
As shown in, the audio signal input to the input section is amplified within the range of the drive voltage + Vcc, -Vcc and output as an amplified audio signal. Therefore, the electric power in the area surrounded by the diagonal line in the figure is well known. Is converted to heat as loss power. Generally, in order to prevent the power amplifier 20 composed of transistors from being destroyed by such heat generation, a heat sink is attached. In this case, even if the level of the amplified audio signal changes, the levels of the drive voltages + Vcc and -Vcc are constant due to the above-described operation of the switching power supply 10. Therefore, when the level of the amplified audio signal is small, the area of the shaded area becomes very large,
Since the amount of heat generation also increases accordingly, the size of the heat dissipation plate becomes large in consideration of such amount of heat generation. This leads to an increase in the size and weight of equipment incorporating such a device, and a large power loss, resulting in extremely inefficiency. In addition, it is necessary to incorporate a high-priced power amplifier 20 with high heat resistance. There were various problems such as

[0005]

In the power supply for power amplifier of the present invention, the generating means for generating the drive voltage for driving the power amplifier, and the detection signal corresponding to the magnitude of the drive voltage are used to generate the drive voltage. In a power amplifier power supply having a control means for controlling a drive voltage, an output signal from the power amplifier is supplied to the control means instead of the detection signal, and the control means changes the level of the output signal. The above-mentioned problem is solved by controlling the generation means so that the level of the drive voltage follows the above.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the present invention, a switching power supply is applied as a power amplifier power supply in the embodiment, but the present invention is not limited to this. Of course, the present invention is not limited to the switching power supply of the type shown in the embodiment. Further, in the present invention, an audio signal is applied as the input signal to the power amplifier in the embodiment, but the input signal is not limited to the audio signal. Further, in the present invention, in the embodiment, the power amplifier is described as being applied to the type driven by positive and negative drive voltages + Vcc and −Vcc, but is not necessarily limited to the type driven by positive and negative drive voltages. However, it may be of a type driven by either one of the drive voltages.

FIG. 1 is a circuit diagram of a switching power supply, a power amplifier driven by driving voltages + Vcc and -Vcc supplied from the switching power supply, and a speaker for converting an amplified audio signal from the power amplifier into audio and outputting the audio. Therefore, the portions corresponding to those in FIG. 6 are denoted by the same reference numerals. Note that the portions associated with the same reference numerals have already been described in detail with reference to FIG. 6, so description thereof will be omitted.

Switching power supply 1 in the present embodiment
At 0, the AC filter / rectifying / smoothing circuit 102, the converter transformer 103, the switching transistor 104, and the rectifying / smoothing circuit 105 are used as generating means for generating the drive voltages + Vcc and −Vcc for driving the power amplifier 20. Have and drive voltage + V
Control circuit 10 as a control means for controlling cc and -Vcc
Have six.

The conventional control circuit 106 has its input section connected to the output section of the rectifying and smoothing circuit 105,
Although the drive voltage + Vcc and -Vcc are controlled to be constant in response to the input of the drive voltage + Vcc which is the output of the rectifying / smoothing circuit 105, the control circuit 106 according to the present embodiment has a power amplifier at its input portion. 20 is connected to the output section of the power amplifier 20 to follow the level change of the amplified audio signal output from the output section of the power amplifier 20 and drive voltage + Vc
The on / off operation of the switching transistor 104 constituting the generating means is controlled so that the levels of c and -Vcc follow each other.

As shown in FIG. 2, the power amplifier 20 has an np
The n-transistor 203 and the pnp transistor 204 have a push-pull connection configuration in which their respective emitters and bases are commonly connected to each other.
04 Driving voltage + Vcc, -Vcc to each collector
Are separately supplied, the commonly connected bases are used as the input portion of the audio signal, and the commonly connected emitters are used as the output portion of the amplified audio signal. The audio signal is given to the common connection bases of the transistors 203 and 204 which are the input sections of the power amplifier 20 via the input terminal 203, and the amplified audio signal is supplied to the transistors 203 and 204 which are the output sections of the power amplifier 20. The common-connected emitter is adapted to output to the speaker 30.

As shown in FIG. 3, the control circuit 106 includes an output portion of the power amplifier 20, that is, the both transistors 203,
An input unit 106a to which an amplified audio signal is input from a commonly connected emitter 204 and a switching transistor 104.
An output section 106b connected to the base of the current limiting resistor 106c, a shunt regulator 106d,
Voltage dividing resistors 106e and 106f, photo coupler 106g,
It has a triangular wave oscillator 106h and a comparator 106i. Then, when the level of the amplified audio signal applied to the input section 106a changes, the control circuit 106 changes the divided voltage at the connection section of the voltage dividing resistors 106e and 106f in response to this, and thereby the shunt regulator 10 is changed.
As a result of the change in the conduction of 6d, the photocoupler 106g
The light emitting amount of the light emitting diode PD also changes, and the conduction of the light receiving transistor RT also changes following the change in the light emitting amount. Here, since the triangular wave oscillator 106h is connected to the non-inversion terminal + of the comparator 106i, and the light receiving transistor RT is connected to the inversion terminal − of the comparator 106i, the comparator 106i detects the triangular wave from the triangular wave oscillator 106h. And the levels of the amplified audio signals output from the light receiving transistor RT are compared, and the comparison output is output. Therefore, this comparison output is a pulse train having an on-off duty that follows the level change of the amplified audio signal,
The switching transistor 104 is ON / OFF driven by this pulse train. As a result, the converter transformer 103
The drive voltages + Vcc and -Vcc on the secondary side change following the level change of the amplified audio signal as shown in FIG. In FIG. 4, when the level of the audio signal input from the input terminal 203 is on the + Vcc side, in the power amplifier 20, one transistor 203 is conductive and the other transistor 204 is non-conductive, and the level of the audio signal is −. When it is on the Vcc side, one transistor 203 does not become conductive and the other transistor 204
Conducts. Then, the drive voltages + Vcc and -Vcc for driving the power amplifier 20 have a voice signal level of + Vc so that the power loss in the power amplifier 20 is minimized.
Regardless of the c side or the −Vcc side, the transistor 103,
The control circuit 106 controls the on / off operation of the switching transistor 104 so that the switching transistor 104 can be driven. When the switching power supply operates normally, an offset voltage is applied to the −Vcc side when the audio signal is on the + Vcc side, and to the + Vcc side when the audio signal is on the −Vcc side.

In the above-described embodiment, the control circuit 106 uses the amplified audio signal from the power amplifier 20 as an input signal to its input section. However, as shown in FIG. The generated audio signal, that is, the audio signal that is the input signal to the input unit of the power amplifier 20 may be used as it is.

It should be noted that in the above-described embodiment, the level change of the audio signal is relatively low at a relatively low frequency, and the level change of each audio signal is followed. Even when the drive voltage does not completely follow the level change of each audio signal due to a relatively high frequency that changes drastically, the level change of the drive voltage is made to follow the peak change of the audio signal as the level change. I don't mind.

It should be noted that the inventors of the present invention used the conventional power supply for power amplifier (for example, drive voltage + Vcc = 30 V, sine wave peak 20 V of power amplifier output, cycle 2 msec) and the above-described embodiment under the same conditions. According to the comparison with the power amplifier power source (for example, power amplifier output + 5V), the present embodiment has about 1/3 of the conventional power loss.

[0016]

As described above, in the power amplifier power supply according to any one of claims 1 to 4 , it is possible to control the drive voltage level of the power amplifier by following the level of the input signal or output signal to the power amplifier. As a result, the power loss in the power amplifier is reduced to a small extent and the amount of heat generated by the power loss is suppressed, which makes it possible to reduce the size of the heat sink, and to promote the reduction in size and weight of equipment incorporating the power amplifier and high efficiency. Can be promoted.

According to the power amplifier of the invention of claim 5 , the input signal is amplified while being driven by the drive voltage supplied from the power amplifier power source according to any one of claims 1 to 4. Since it is a power amplifier that drives a speaker by an output signal related to the amplification of, the power amplifier has high efficiency.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a switching power supply, a power amplifier, and a speaker according to an embodiment of the present invention.

FIG. 2 is a specific circuit diagram of the power amplifier shown in FIG.

FIG. 3 is a specific circuit diagram of the control circuit of FIG.

4A and 4B are waveform diagrams of an audio signal and a drive voltage, respectively, for explaining power loss in a power amplifier using the switching power supply of FIG.

FIG. 5 is a circuit diagram of a switching power supply, a power amplifier and a speaker according to another embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional switching power supply, power amplifier, and speaker.

7A and 7B are waveform diagrams of an audio signal and a driving voltage, respectively, for explaining power loss in a power amplifier using the switching power supply of FIG.

[Explanation of symbols]

10 Switching power supply 20 power amplifier 30 speakers 101 input terminal 102 AC filter / rectifier smoothing circuit 103 converter transformer 104 switching transistor 105 Rectifying and smoothing circuit 106 control circuit

Claims (5)

(57) [Claims] Generating means for generating a driving voltage for driving the power amplifier [1 claim ## in power amplifier power supply and control means for controlling the pre-Symbol driving voltage, said control means from said power amplifier Output signal level
Pulse with on-off duty following bell change
A column, and the generating means outputs a signal of the output signal from the power amplifier.
Pulse with on-off duty following bell change
The output signal from the power amplifier is driven on and off by the column.
A power amplifier power supply characterized by generating a drive voltage that follows changes in signal level . 2. A generating means for generating a driving voltage for driving the power amplifier, the power amplifier power supply and control means for controlling the pre-Symbol driving voltage, the control means, to said power amplifier Input signal level
Pulse train with on-off duty following change
And the generation means outputs the level of the input signal to the power amplifier.
Pulse train with on-off duty following change
Input signal from the power amplifier driven on and off by
A power amplifier power supply characterized by generating a drive voltage that follows changes in the level . 3. A power amplifier battery according to claim 1 or 2.
In the source, the control means is at least a triangular wave generating a triangular wave.
Oscillator and triangular wave from the triangular wave oscillator is input to one end
The output signal from the power amplifier at the other end
Is a comparator to which the input signal to the power amplifier is input,
And having a triangular wave from a triangular wave oscillator by the comparator.
The output signal from the power amplifier or the power amplifier
By comparing the input signal to the amplifier
Output signal from the amplifier or input signal to the power amplifier
With an on-off duty that follows the level change of
A power amplifier power supply characterized by outputting a loose train . 4. A power amplifier battery according to claim 1 or 2.
At the source, the generating means is at least from the power amplifier.
Output signal or input signal level to the power amplifier
With a pulse train that has an on-off duty that follows changes
It has a switching element for on / off driving, and the power
The input to the output signal or the power amplifier from the amplifier
A power amplifier power supply characterized by generating a drive voltage that follows changes in the signal level . 5. The power according to any one of claims 1 to 4.
-Driven by the drive voltage supplied from the amplifier power supply
To amplify the input signal while amplifying the input signal
A power amplifier for driving a speaker by the output signal.
Pump.