JPH10284948A - Power amplifier use power supply and power amplifier using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the size of a heat sink small by reducing a power loss in the power amplifier so as to decrease a generated heat due to the power loss and to promote small size and light weight and a high efficiency for a device to which the power amplifier is assembled. SOLUTION: The system using the power amplifier 20 is provided with a drive voltage generating means 103,... for the power amplifier 20 and a control means 106 that controls a drive voltage based on a detection signal corresponding to the drive voltage, an audio signal from the power amplifier 20 is supplied to the control means 106 in place of the detection signal and the control means 106 controls the generating means 103,... so that the level of the drive voltage traces a level change in the audio signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power supply for a power amplifier (power amplification circuit) and a power amplifier driven by the power supply.

[0002]

2. Description of the Related Art FIG. 6 shows a switching power supply 10 as a power supply for a conventional power amplifier,
FIG. 2 is a circuit diagram of a power amplifier 20 driven by a driving voltage given from the power amplifier 20 and a speaker 30 driven by the power amplifier 20. The switching power supply 10 includes an AC filter / rectifying / smoothing unit 102 that performs AC filtering and rectifies and smoothes AC power supplied from a pair of input terminals 101.
And a converter transformer 103 in which an input voltage converted to DC by the AC filter / rectifier / smoothing circuit 102 is supplied to a primary winding 103a.
3, a switching transistor 104 as a switching element connected to the other end, and a converter transformer 10
3 is connected between both ends of the secondary winding 103b.
03b is applied to the DC drive voltage + Vc
rectifying / 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 the 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 drive voltages + Vcc and -Vcc for driving the power amplifier 20. The control circuit 106 generates the driving voltage + Vc based on a detection signal corresponding to the magnitude of the driving voltage.
c and -Vcc are controlled to be constant. Since the operation of the switching power supply 10 is well known, a detailed description thereof will be omitted.

A power amplifier 20 includes a driving voltage receiving section 201 to which a driving voltage + Vcc is applied, and a driving voltage −Vcc.
And a drive voltage receiving unit 202 to which the audio signal as an input signal supplied to the input unit is amplified and output from the output unit as an output signal. Specifically, in the power amplifier 20, the emitter and the base of each of the npn transistor and the pnp transistor are connected in common, the driving voltages + Vcc and -Vcc are supplied to the respective collectors, and the base connected in common is the audio signal. And an emitter connected in common is configured as an output section for an amplified audio signal, and the audio signal is supplied to an input section of the power amplifier 20 via an input terminal 203. . The audio signal amplified by the power amplifier 20 in this manner 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, FIG.
As shown by, the audio signal input to the input unit is amplified within the range of the driving voltages + Vcc and -Vcc and output as an amplified audio signal. Is converted to heat as power loss. Generally, a heat sink is attached to prevent the power amplifier 20 composed of a transistor from being destroyed by such heat generation. In this case, even if the level of the amplified audio signal changes, the levels of the driving voltages + Vcc and -Vcc are kept constant by 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 hatched area becomes very large,
Since the heat value increases accordingly, the size of the heat radiating plate increases in anticipation of such heat value. This leads to an increase in the size and weight of the equipment in which such a device is incorporated. In addition, the power loss is so large that the efficiency becomes extremely inefficient. There were various issues such as

[0005]

In the power supply for a power amplifier according to the present invention, a generating means for generating a driving voltage for driving the power amplifier, and a detecting signal corresponding to the magnitude of the driving voltage are used. An output signal from the power amplifier is supplied to the control means in place of the detection signal, and the control means controls a level change 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 control voltage.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In the present invention, a switching power supply is used 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 used as an input signal to a power amplifier in the embodiment, but the input signal is not limited to an audio signal. In the present invention, the power amplifier is described in the embodiment as applied to a type driven by positive and negative drive voltages + Vcc and -Vcc, but is not necessarily limited to a type driven by positive and negative drive voltages. Instead, it may be of a type driven by any one of the driving voltages.

FIG. 1 is a circuit diagram of a switching power supply, a power amplifier driven by supplying driving voltages + Vcc and -Vcc from the switching power supply, and a speaker for converting an amplified audio signal from the power amplifier into a sound and outputting the sound. The same reference numerals are given to the portions corresponding to those in FIG. Note that the portions related to the same reference numerals have already been described in detail with reference to FIG.

[0009] Switching power supply 1 in the present embodiment
0, an AC filter / rectifying / smoothing circuit 102, a converter transformer 103, a switching transistor 104, and a rectifying / smoothing circuit 105 are used as generating means for generating drive voltages + Vcc and -Vcc for driving the power amplifier 20. And the driving voltage + V
control circuit 10 as control means for controlling cc, -Vcc.
6.

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

The power amplifier 20 has np as shown in FIG.
The emitter and the base of each of the n-transistor 203 and the pnp transistor 204 have a push-pull connection configuration in which they are commonly connected.
04 drive voltage + Vcc, -Vcc
Are individually supplied, a commonly connected base is used as an input unit for an audio signal, and a commonly connected emitter is used as an output unit for an amplified audio signal. The audio signal is applied to the common connection base of each of the transistors 203 and 204 as the input unit of the power amplifier 20 via the input terminal 203, and the amplified audio signal is supplied to each of the transistors 203 and 204 as the output unit of the power amplifier 20. The signal is output to the speaker 30 from the common connection emitter.

As shown in FIG. 3, the control circuit 106 outputs the output of the power amplifier 20, that is, the two transistors 203,
An input section 106a to which an amplified audio signal is input from a common connection emitter 204;
, A current limiting resistor 106c, a shunt regulator 106d,
Voltage dividing resistors 106e and 106f, photocoupler 106g,
It has a triangular wave oscillator 106h and a comparator 106i. When the level of the amplified audio signal supplied to the input unit 106a changes, the control circuit 106 changes the divided voltage at the connection between the voltage dividing resistors 106e and 106f in response to the change.
As a result, the continuity of the photocoupler 106g changes.
The light emission amount of the light emitting diode PD changes, and the conduction of the light receiving transistor RT changes following the change in the light emission amount. Here, the triangular wave oscillator 106h is connected to the non-inverting terminal + of the comparator 106i, and the light receiving transistor RT is connected to the inverting terminal-of the comparator 106i. And the level of each amplified audio signal output from the light receiving transistor RT, and outputs a comparison output. Therefore, as this comparison output, a pulse train having an on / off duty that follows the level change of the amplified audio signal is output,
The switching transistor 104 is driven on and off 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 becomes conductive and the other transistor 204 becomes nonconductive, and the level of the audio signal becomes −. When the voltage is on the Vcc side, one transistor 203 is turned off and the other transistor 204 is turned off.
Conducts. The driving voltages + Vcc and -Vcc for driving the power amplifier 20 are such that the level of the audio signal is + Vc so that the power loss in the power amplifier 20 is minimized.
Regardless of c-side or -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 audio signal is on the + Vcc side and the audio signal is on the -Vcc side, the offset voltage is applied on the + Vcc side when the switching power supply normally operates.

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 unit. However, as shown in FIG. The audio signal to be input, that is, the audio signal input to the input unit of the power amplifier 20 may be used as it is.

In the above-described embodiment, the case where the level change of the audio signal is relatively low and the frequency is relatively low, and the level change of the individual audio signal follows, but the level of the audio signal is low. Even if the driving 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 driving voltage is made to follow the peak change of the audio signal as the level change. No problem.

The inventors of the present invention have proposed a conventional power supply for a power amplifier (eg, drive voltage + Vcc = 30 V, a sine wave peak of the power amplifier output of 20 V, a cycle of 2 ms), and the above-described embodiment under the same conditions. According to a comparison with a power amplifier power supply (for example, power amplifier output +5 V), the present embodiment has a power loss of about one third of the conventional power loss.

[0016]

As described above, in the power supply for a power amplifier according to any one of the first to third aspects of the present invention, the level of the drive voltage can be controlled following the level of the input signal or output signal to the power amplifier. As a result, the power loss in the power amplifier has been reduced to a small extent, and the amount of heat generated due to the power loss has been reduced, thereby enabling the heat sink to be downsized. Can be achieved.

According to the power amplifier of the present invention, the input signal is amplified by being driven by the drive voltage supplied from the power amplifier power supply according to any one of claims 1 to 3, while the input signal is amplified. This is a power amplifier that drives a loudspeaker with an output signal related to the amplification of the power amplifier.

[Brief description of the 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 of FIG.

FIG. 3 is a specific circuit diagram of the control circuit of FIG. 1;

FIG. 4 is a waveform diagram of an audio signal and a drive voltage for explaining power loss in a power amplifier by the switching power supply of FIG. 1;

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.

7 is a waveform chart of an audio signal and a drive voltage for explaining power loss in a power amplifier by the switching power supply of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Switching power supply 20 Power amplifier 30 Speaker 101 Input terminal 102 AC filter / rectification smoothing circuit 103 Converter transformer 104 Switching transistor 105 Rectification smoothing circuit 106 Control circuit

Claims (4)

[Claims] 1. A power amplifier for a power amplifier, comprising: generating means for generating a driving voltage for driving a power amplifier; and control means for controlling the driving voltage based on a detection signal corresponding to the magnitude of the driving voltage. In the power supply, an output signal from the power amplifier is supplied to the control means in place of the detection signal, and the control means follows the level change of the output signal so that the level of the drive voltage follows. A power supply for a power amplifier, which controls the generation unit. 2. A power amplifier for a power amplifier, comprising: generating means for generating a drive voltage for driving a power amplifier; and control means for controlling the drive voltage based on a detection signal corresponding to the magnitude of the drive voltage. In the power supply, an input signal to the power amplifier is supplied to the control means instead of the detection signal, and the control means follows the level change of the input signal so that the level of the drive voltage follows. A power supply for a power amplifier, which controls the generation unit. 3. The converter according to claim 1, wherein said generating means includes a converter transformer having a DC voltage applied to one end of a primary winding, a switching element connected to the other end of the primary winding of the converter transformer, and both ends of a secondary winding of the converter transformer. A switching rectifying / smoothing unit for converting a voltage induced between the rectifying and smoothing units into the driving voltage, wherein the control unit controls an on / off operation of the switching element in response to an input of the output signal or the input signal; The power supply for a power amplifier according to claim 1, wherein the power supply is configured as a power supply. 4. The amplifying device according to claim 1, wherein the amplifying circuit is driven by the driving voltage supplied from the power supply for a power amplifier according to claim 1 to amplify the input signal. Power amplifier that drives speakers.