JP2000341058A - Audio amplification system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the playback sound quality of the system by allowing one reference bias potential between a 1st and a 2nd reference bias potential, which is set between a power source potential and a reference potential, to follow up the other reference bias potential. SOLUTION: The power amplification of an audio signal by a preamplifier 1 and a power amplifier 2 is carried out and a speaker SP is driven, but a voltage control circuit 27 in the power amplifier 2 makes the 2nd reference bias potential VB2 in the power amplifier 2 follow up the same potential with the 1st reference bias potential VB1, and the discrepancy (VB1-VB2) of a DC component between the signal output Vo of the preamplifier 1 and the signal input Vi of the power amplifier 2 is always zero. The preamplifier 1 and power amplifier 2 stably drive the speaker SP having zero reference in the absence of a signal as they are connected directly to each other on a DC basis without interposing a coupling capacitor for DC cutoff between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio amplifier system, and more particularly to a technology effective when applied to an audio reproduction system for driving a speaker by amplifying an audio signal with a preamplifier and a power amplifier. The present invention relates to technology effective for use in car audio systems.

[0002]

2. Description of the Related Art An audio amplifier system is usually divided into a preamplifier section and a power amplifier (main amplifier) section. An audio signal preamplified to a predetermined level by a preamplifier section is amplified by a power amplifier section. And the speaker is driven by electric power. The audio amplifier system is described in detail in, for example, "Basic Transistor Amplifier Design Method" published by Radio Engineering Company.

FIG. 4 shows a configuration example of a conventional audio amplifier system.

The audio amplifier system shown in FIG.
It comprises a preamplifier 1 and a power amplifier 2. The preamplifier unit 1 includes a plurality of purine amplifier circuits 11 for preamplifying an audio signal generated by a sound source device 10 such as a CD player.

Each preamplifier circuit 11 is constituted by a differential input type DC amplifier circuit in which a predetermined voltage amplification gain is set by feedback resistors R11 and R12, and a reference bias voltage VB1 in the preamplifier unit 1 is set to a zero signal reference. To perform the DC amplification operation.

The reference bias potential VB1 is applied to the preamplifier 1
Is generated by the reference voltage generation circuit 16. The reference voltage generation circuit 16 divides the power supply voltage (Vcc-GND) by the resistors R13 and R14 to generate the power supply potential Vcc.
And a reference bias potential VB1 substantially intermediate between the reference potential GND.
Generate This reference bias potential VB1 is distributed to a plurality of preamplifier circuits 11 in the preamplifier 1 as a zero signal reference, and is also used as a zero signal reference for the rest of the preamplifier 1 as a whole.

The audio signal output (preamplifier output) Vo preamplified by the preamplifier circuit 11 is supplied from the preamplifier output terminal P11 to the audio input terminal P21 of the power amplifier section 2 via a coupling capacitance element (coupling capacitor) Cc. Is done.

The power amplifier section 2 has a pair of an input circuit 21 and an output circuit 22 for a plurality of channels. Each input circuit 21 is constituted by a differential input type DC amplifier circuit in which a predetermined voltage amplification gain is set by feedback resistors R21 and R22, and the reference bias voltage VB2 in the power amplifier unit 2 is set to a zero signal reference. Performs DC amplification operation.

The input circuit 21 has an audio input terminal P2
1 is supplied to the power supply potential Vcc and the reference potential GN.
After DC amplification using the second reference bias potential VB2 set between D, the resultant is supplied to the output circuit 22 as a drive signal.

Each output circuit 22 forms a BTL output circuit by a phase division circuit 23 and two DC power amplifier circuits 24 and 25. The output of the BTL output circuit 22 is supplied to the speaker SP via output terminals P21 and P23.
Is directly driven by electric power. In this case, the output terminal of the BTL output circuit 22 and the speaker SP are directly connected (directly connected) without a DC blocking capacitor.

The second reference bias potential VB2 is generated by a reference voltage generation circuit 26 in the power amplifier 2. The reference voltage generation circuit 26 supplies the power supply voltage (Vcc-GN
D) is divided by the resistors R23 and R24 to generate a reference bias potential VB2 substantially intermediate between the power supply potential Vcc and the reference potential GND. This reference bias potential VB2
Is distributed to the plurality of input circuits 21 in the power amplifier unit 2 as a zero signal reference, and is also used as a zero signal reference for the other power amplifier units 2 as a whole.

Here, the output terminal P11 of the preamplifier 1
The input terminal P21 of the power amplifier unit 2 is isolated from the input terminal P21 by a coupling capacitance element Cc. As a result, the DC component mismatch dV (=) between the output signal (Vo) of the preamplifier 1 and the input signal (Vi) of the power amplifier 2 is obtained.
Even if VB1−VB2) is present, it can be ignored and both amplifier sections 1 and 2 can be connected. That is, the preamplifier unit 1 and the power amplifier unit 2 can operate independently of each other in a DC manner with the interposition of the coupling capacitance element Cc.

This means that the amplifier sections 1 and 2 can be independently configured as separate semiconductor integrated circuits, and that the degree of freedom of combination between the preamplifier section 1 and the power amplifier section 2 can be obtained. Brings the convenience of being able to construct an audio amplifier system in any combination.

[0014]

However, it has been clarified by the present inventors that the above-described technology has the following problems.

That is, in the above-described audio amplifier system, it is necessary to presuppose that the coupling capacitance element Cc interposed between the preamplifier 1 and the power amplifier 2 reliably cuts off the direct current.

However, it is difficult to say that there is no danger of DC leakage or short-circuiting due to aging deterioration or manufacturing problems as a practical problem. When such a leak or a short circuit occurs, the power amplifier unit 2 that amplifies the audio signal with DC power and drives the speaker SP outputs a DC component that leaks through the coupling capacitive element Cc and inputs the signal even when there is no signal. (DV) is amplified by DC power and supplied to the speaker SP. As a result, there is a possibility that more serious problems such as burning of the speaker SP may occur.

Also, the use of the coupling capacitance element Cc increases the parts cost of the audio amplifier system, and has been a negative factor that prevents the system from being downsized.

Further, the presence of the coupling capacitive element Cc also affects the frequency transfer characteristics (particularly in a low frequency range) and the phase characteristics of the audio signal, and this is the reproduction which is most important as an audio amplifier system. It was also a factor that hindered improvement in sound quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide an audio amplifier system comprising a preamplifier section and a power amplifier section. Another object of the present invention is to provide a technology that enables reproduction sound quality, which is regarded as particularly important in an audio amplifier system.

The above and other objects and features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0021]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, a preamplifier section for performing pre-amplification of an audio signal with the first reference bias potential set between the power supply potential and the reference potential as a zero signal reference, and a second amplifier set between the power supply potential and the reference potential. An audio amplifier system configured by connecting a power amplifier unit for amplifying the power of an audio signal with the reference bias potential of zero as a zero signal reference, and directly applying the signal output of the preamplifier unit to the signal input of the power amplifier unit Together with the first or second
And a voltage control circuit for causing one of the reference bias potentials to follow the same potential as the other reference bias potential (first invention).

In the above-mentioned means, a power amplifier section is constituted by using a BTL output circuit for driving a speaker by the outputs of a pair of DC power amplifiers which are driven complementarily (second invention).

Further, a voltage control circuit for generating a second reference bias potential following the same potential as the first reference bias potential is provided in the preamplifier (third invention).

Further, a voltage control circuit for generating the first reference bias potential following the same potential as the second reference bias potential is provided in the power amplifier section (fourth invention).

Further, a circuit for a plurality of channels is built in each of the preamplifier section and the power amplifier section, and the circuits of each channel are operated based on a common reference bias potential as a zero signal reference (fifth embodiment). invention).

According to the above-described means, no direct current connection is required between the pre-amplifier and the power amplifier, and no direct current connection is required. It is possible to stably drive the power of the speaker with the time as the zero reference.

[0028] Thus, it is possible to reliably avoid the possibility of occurrence of troubles such as speaker burnout, to reduce the cost of parts of the system and to reduce the size thereof, and to improve the reproduction sound quality which is particularly important in an audio amplifier system. Is achieved.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of an audio amplifier system to which the technique of the present invention is applied.

The audio amplifier system shown in FIG.
It comprises a preamplifier 1 and a power amplifier 2. Although not particularly limited, both amplifier sections 1 and 2 are formed as independent semiconductor integrated circuit devices.

The preamplifier 1 is provided with a plurality of channels of pudding amplifier circuits 11 for preamplifying audio signals generated by a sound source device 10 such as a CD player.

Each of the preamplifier circuits 11 is constituted by a differential input type DC amplifying circuit in which a predetermined voltage amplification gain is set by feedback resistors R11 and R12, and the reference bias voltage VB1 in the preamplifier 1 is set to a zero signal reference. To perform the DC amplification operation.

The reference bias potential VB1 is
Is generated by the reference voltage generation circuit 16. The reference voltage generation circuit 16 divides the power supply voltage (Vcc-GND) by the resistors R13 and R14 to generate the power supply potential Vcc.
And a reference bias potential VB1 substantially intermediate between the reference potential GND.
Generate This reference bias potential VB1 is distributed to a plurality of preamplifier circuits 11 in the preamplifier 1 as a zero signal reference, and is also used as a zero signal reference for the rest of the preamplifier 1 as a whole.

In the power amplifier section 2, pairs of an input circuit 21 and an output circuit 22 are formed for a plurality of channels. At the same time, a voltage control circuit that generates the reference bias potential VB2 of the power amplifier unit 2 by following the same potential as the reference bias potential VB1 of the preamplifier unit 1 introduced from the preamplifier unit 1 via the terminals P31 and P32. 27 are provided.

Each input circuit 21 has a feedback resistor R2
It is configured by a differential input type DC amplifier circuit in which a predetermined voltage amplification gain is set by 1 and R22, and performs a DC amplification operation using a reference bias voltage VB2 in the power amplifier unit 2 as a zero signal reference.

The input circuit 21 converts the signal (Vi) supplied to the audio input terminal P21 into a reference bias potential VB2 set between the power supply potential Vcc and the reference potential GND.
After that, the signal is supplied to the output circuit 22 as a drive signal.

Each output circuit 22 forms a BTL output circuit by the phase dividing circuit 23 and the two DC power amplifier circuits 24 and 25. The output of the BTL output circuit 22 directly drives the speaker SP via the terminals P22 and P23. The output terminal of the BTL output circuit 22 and the speaker SP are directly connected without a DC blocking capacitor.

The voltage control circuit 27 is a voltage follower circuit (voltage follower) configured to operate the output of the DC differential amplifier circuit having a sufficiently large naked gain as a voltage amplifier circuit having zero gain by all negative feedback. The high-impedance input receives the reference bias potential VB1 of the preamplifier 1 introduced from the preamplifier 1 via the terminals P31 and P32, converts the same to a low impedance potential at the same potential, and outputs the same. The impedance-converted potential VB1 is used as a reference bias potential VB2 (= VB1) in the power amplifier 2.

The reference bias potential VB2 is distributed to a plurality of input circuits 21 in the power amplifier unit 2 as a zero signal reference, and is also used as a zero signal reference in the other power amplifier units 2 as a whole. That is, the voltage control circuit 27 is connected to the reference voltage generation circuit 2 in the power amplifier unit 2.
6 is formed.

The output terminal P11 of the preamplifier unit 1 and the input terminal P21 of the power amplifier unit 2 are directly connected without any intervening coupling capacitance element.

Next, the operation of the audio amplifier system configured as described above will be described.

The audio signal output (preamplifier output) Vo pre-amplified by the preamplifier 11 is directly supplied from the preamplifier output terminal P11 to the audio input terminal P21 of the power amplifier 2. At this time, the reference bias potential VB1 of the preamplifier 1 is also input to the voltage control circuit 27 in the power amplifier 2 via the terminals P31 and P32.

The voltage control circuit 27 generates a reference bias potential VB2 (= VB1) that follows the same potential as the reference bias potential VB1 on the preamplifier section 1 side.

Each input circuit 21 in the power amplifier unit 2
A DC amplification operation is performed using the reference bias potential VB2 as a zero signal reference to drive the output circuit 22. Then, the output circuit 22 amplifies the output signal of the input circuit 21 by DC power and drives the speaker SP.

As described above, the power of the audio signal is amplified by the preamplifier 1 and the power amplifier 2 to drive the speaker SP.
It should be noted that the reference bias potential VB2 in the power amplifier 2 is changed to the reference bias potential VB1 in the preamplifier 1 by the voltage control circuit 27 in the power amplifier 2.
And the DC component mismatch dV (= VB1-VB2) between the output signal (Vo) of the preamplifier 1 and the input signal (Vi) of the power amplifier 2 is always zero. It is to become. That is, the difference between the zero signal levels becomes zero.

Therefore, the preamplifier unit 1 and the power amplifier unit 2 can be connected directly to each other in a DC state without any signal, without intervening a coupling capacitance element for blocking DC. The power drive of the speaker SP based on the zero reference can be stably performed.

As described above, since the preamplifier unit 1 and the power amplifier unit 2 can be directly connected without using a coupling capacitance element, it is possible to reliably avoid problems such as loudspeaker burnout and the like, and to reduce system components. This makes it possible to reduce the cost and size, and also to improve the reproduction sound quality which is particularly important in an audio amplifier system.

FIG. 2 shows a second embodiment of the present invention.

In the audio amplifier system shown in FIG. 2, the voltage control circuit 27 for generating the reference bias potential VB2 in the power amplifier unit 2 is replaced by a preamplifier unit. 1.

In this case, the voltage control circuit 27 generates a reference bias potential VB2 (= VB1) that follows the same potential as the reference bias potential VB1 in the preamplifier 1, and supplies the same to the power amplifier 2. .

In the second embodiment, as in the first embodiment, the preamplifier 1 and the power amplifier 2
Can be directly connected without using a coupling capacitance element, thereby reliably avoiding problems such as speaker burnout, enabling a reduction in system component costs and downsizing, and particularly in an audio amplifier system. The effect of improving the reproduction sound quality which is regarded as important can be obtained.

In the second embodiment, the power amplifier 2
Is generated on the preamplifier 1 side, the output Vo of the preamplifier 1 is branched to the inputs Vi of a plurality of power amplifiers 2.
It is particularly advantageous.

FIG. 3 shows a third embodiment of the audio amplifier system according to the present invention.

In the system shown in FIG. 2, a voltage control circuit 27 for generating a reference bias potential VB1 in the preamplifier 1 is provided in the power amplifier 1 in contrast to the case of FIG.

In this case, the voltage control circuit 27 generates a reference bias potential VB1 (= VB2) that follows the same potential as the reference bias potential VB2 in the power amplifier section 2 and supplies it to the preamplifier section 1.

In the power amplifier section 2, the power supply voltage (Vc
c-GND) by the resistors R23 and R24, the power supply potential Vcc and the reference potential GND are obtained.
, A reference bias potential VB2 that is approximately intermediate between the two. The reference bias potential VB2 is distributed to a plurality of input circuits 21 in the power amplifier unit 2 as a zero signal reference, and is also current-amplified by the voltage control circuit 27 so that the preamplifier 1
Side is supplied as a zero signal reference.

Also in this case, the same effect as in the first embodiment can be obtained by setting the DC component mismatch (dV) between the two amplifier sections 1 and 2 to zero.

In this embodiment, since the reference bias potential VB1 of the preamplifier 1 is generated by the power amplifier 2, the output Vo of the plurality of preamplifiers 1 is selectively applied to the input Vi of the power amplifier 2. This is particularly advantageous for systems that are connected simultaneously.

Further, in this embodiment, the output dynamic range of the power amplifier unit 2 is automatically set so that the reference bias potential VB1 on the preamplifier unit 1 follows the reference bias potential VB2 on the power amplifier unit 2 side. Is set to maximize the reference bias potential VB2 on the preamplifier section 1 side.
1 also has the advantage that it is automatically set so that its output dynamic range is maximized.

As described above, in the first aspect of the present invention, the pre-amplification of the audio signal is performed with the first reference bias potential (VB1) set between the power supply potential and the reference potential as a zero signal reference. A preamplifier (1) and a second reference bias potential (V) set between the power supply potential and the reference potential.
In an audio amplifier system configured by connecting a power amplifier section (1) for performing power amplification of an audio signal with B2) as a zero signal reference, the signal output of the preamplifier section is directly applied to the signal input of the power amplifier section. In addition, a voltage control circuit (7) is provided for causing one of the first and second reference bias potentials to follow the same potential as the other reference bias potential, thereby ensuring the occurrence of problems such as speaker burnout. In addition to this, it is possible to reduce the cost of parts of the system and reduce the size of the system, and it is also possible to obtain the effect of improving the reproduction sound quality which is regarded particularly important in the audio amplifier system.

According to a second aspect of the present invention, in the first aspect, a power amplifier section is constituted by using a BTL output circuit (22) for driving a speaker by an output of a pair of DC power amplifiers driven in a complementary manner. As a result, in addition to the above-described effects, an effect is obtained that the speaker can be directly driven by electric power without any intervening coupling capacitance element.

According to a third aspect of the present invention, in the first or second aspect, a voltage control circuit for generating a second reference bias potential following the same potential as the first reference bias potential is provided in the preamplifier section. With this configuration, in addition to the above-described effects, an effect is obtained that is particularly advantageous when the output of the preamplifier is branched to the inputs of a plurality of power amplifiers.

According to a fourth aspect of the present invention, in the first or second aspect, a voltage control circuit for generating the first reference bias potential following the same potential as the second reference bias potential is provided in the power amplifier section. Therefore, in addition to the above effects, by setting a reference bias potential that maximizes the output dynamic range of the power amplifier section, the reference bias potential on the preamplifier section side is also
The effect is obtained that the output dynamic range is automatically set so as to maximize the output dynamic range.

According to a fifth aspect of the present invention, a circuit for a plurality of channels is incorporated in each of a preamplifier unit and a power amplifier unit, and each channel circuit operates based on a common reference bias potential as a zero signal reference. With this configuration, in addition to the above-described effects, an effect that a zero signal reference can be obtained with a minimum configuration can be obtained.

Although the invention made by the inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and can be variously modified without departing from the gist thereof. Needless to say. For example, the reference voltage generation circuit may be configured using an element other than a resistor, for example, a low voltage element such as a Zener diode or a constant voltage circuit.

In the above description, the case where the invention made by the present inventor is applied to a pre / power-separated audio amplifier system, which is a field of application as the background, has been mainly described. However, the present invention is not limited to this. For example, the present invention can be applied to a case where a preamplifier and a power amplifier are formed in the same semiconductor integrated circuit.

[0068]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

That is, in an audio amplifier system composed of a preamplifier section and a power amplifier section, it is possible to reliably avoid problems such as burnout of a speaker, to reduce the cost of parts of the system, and to reduce the size of the audio system. The effect of improving the reproduced sound quality, which is particularly important in the amplifier system, is obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an audio amplifier system to which the present invention has been applied.

FIG. 2 shows a second embodiment of the audio amplifier system according to the present invention.
FIG. 2 is a circuit diagram showing a main part of the embodiment.

FIG. 3 shows a third embodiment of the audio amplifier system according to the present invention.
FIG. 2 is a circuit diagram showing a main part of the embodiment.

FIG. 4 is a circuit diagram showing an outline of a conventional audio amplifier system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Preamplifier part 2 Power amplifier part 10 Sound source equipment 11 Pudding amplifier circuit 16 Reference voltage generation circuit 21 Input circuit 22 Output circuit 22 BTL output circuit 23 Phase division circuit 24, 25 DC power amplification circuit 26 Reference voltage generation circuit 27 Voltage control circuit SP Speaker Vcc Power supply potential GND Reference potential Vo Signal output of preamplifier section Vi Signal input of power amplifier section VB1 First reference bias voltage VB2 Second reference bias potential P11 Output terminal of preamplifier section P21 Input terminal of power amplifier section P22, P23 Power amplifier Output terminals P31, P32 Reference bias potential terminal

Continuing from the front page (72) Inventor Shoichi Hosoda 15 Asahidai, Moroyama-cho, Iruma-gun, Saitama Prefecture Inside the Hitachi Eastern Semiconductor Co., Ltd. Semiconductor Co., Ltd. F-term (reference) 5J069 AA02 AA23 AA41 CA55 CA87 CA92 CC02 FA01 FA10 HA20 HA25 HA32 KA11 KA12 KA62 MA05 MA11 SA05 SA07 TA01 TA06 5J091 AA02 AA23 AA41 CA55 CA87 CA92 FA01 FA10 HA20 HA25 MA05 SA05 TA01 TA06

Claims (5)

[Claims] A first potential set between a power supply potential and a reference potential;
A preamplifier unit for performing pre-amplification of an audio signal using the reference bias potential as a zero signal reference, and power amplification of the audio signal using a second reference bias potential set between the power supply potential and the reference potential as a zero signal reference An audio amplifier system configured by connecting to a power amplifier section, wherein a signal output of a preamplifier section is directly applied to a signal input of a power amplifier section, and one of the first and second reference bias potentials is applied to the other. An audio amplifier system comprising a voltage control circuit for causing the reference bias potential to follow the same potential as the reference bias potential. 2. The audio amplifier system according to claim 1, wherein the power amplifier section is constituted by a BTL output circuit that drives a speaker by outputs of a pair of DC power amplifiers that are driven complementarily. 3. The audio device according to claim 1, wherein a voltage control circuit for generating a second reference bias potential following the same potential as the first reference bias potential is provided in the preamplifier unit. Amplifier system. 4. The power amplifier section according to claim 1, wherein a voltage control circuit for generating the first reference bias potential following the same potential as the second reference bias potential is provided in the power amplifier section. Audio amplifier system. 5. The preamplifier section and the power amplifier section each include circuits for a plurality of channels, and the circuits of each channel operate based on a common reference bias potential as a zero signal reference. 5. The audio amplifier system according to any one of 1 to 4.