JPH10209776A - Power amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power amplifier by which power consumption is reduced and a distortion factor of an output signal within a full output range is improved. SOLUTION: An input signal is amplified by a nonlinear amplifier circuit 10, from which positive and negative output half-wave signals, whose output DC voltage is set to a ground level, are produced. The positive output half wave signal is amplified by output amplifier circuits 11, 13 and the negative output half-wave signal is amplified by output amplifier circuits 12, 14. When the input signal is higher than a reference voltage Vref2, a load 8 is BTL-driven by the output amplifier circuits 11, 12 and a load 9 is BTL-driven by the output amplifier circuits 13, 14. When the input signal is lower than the Vref2, the loads 8, 9 are connected directly, and the loads 8, 9 are BTL-driven by the output amplifier circuits 11, 14 as asingle load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power amplifying device suitable for use in an electric vehicle.

[0002]

2. Description of the Related Art Heretofore, a power amplifying device aimed at reducing power loss has been proposed.
As disclosed in Japanese Patent Publication No. 18830, there has been a technique in which a drive type for a load is changed according to an input signal level. FIG. 4 shows such a conventional power amplifying device.

In FIG. 2, when the input audio signal is within the window of the window comparator 1, the switching signals from the window comparator 1 bring the movable terminals of the switching circuits 2 and 3 into the state shown in the figure. The input audio signal is amplified by the non-inverted output amplifier circuit 4 and the inverted output amplifier circuit 7, and then supplied to loads 8 and 9. Also,
Since the input terminal of the non-inverting amplifier 6 is grounded, the output signal becomes Vcc / 2. Therefore, the output terminals of the non-inverting and inverting output amplifier circuits 4 and 7 are AC grounded, and the load 8
And 9 are driven in a single-ended manner by the output signals of the non-inverting and inverting output amplifier circuits 4 and 7.

When the input audio signal is out of the window, the movable terminals of the switching circuits 2 and 3 are reversed by the switching signal of the window comparator 1 as shown in the figure.
Therefore, the non-inverted and inverted output amplifier circuits 4 and 5 amplify the input audio signal and drive the load 8 by BTL, and the non-inverted and inverted output amplifier circuits 6 and 7
TL drive is performed.

Therefore, when the input audio signal is small, the circuit of FIG. 4 is in the form of a single-ended amplifier, and when the input audio signal is large, it is in the form of a BTL amplifier. As shown in FIG. 5B, the power consumption of the single-ended amplifier circuit (dotted line C) is smaller than that of the BTL amplifier circuit (solid line D). Therefore, when the input audio signal is small, the power consumption is relatively small. Become.

[0006]

Problems to be solved by the invention As shown in FIG.
The relationship between the output power of the single-ended amplifier circuit (dotted line A) and the output power of the BTL amplifier circuit (solid line B) and the distortion factor is as follows.
The amplifier circuit can maintain a good distortion factor up to a higher output side than the single-ended amplifier circuit. FIG. 5B shows the relationship between the output power and the power consumption of the single-ended amplifier circuit and the BTL amplifier circuit. The single-ended amplifier circuit reduces power consumption only on the lower output side than the BTL amplifier circuit. Is done. 5 (b) and FIG. 5 (b), in a region X where the power consumption is to be reduced by changing to a single-ended amplifier circuit, the distortion rate of the output signal of the single-ended amplifier circuit is lower. Getting worse. That is, the circuit of FIG. 4 has a problem that the distortion rate of the output signal is deteriorated when a single-ended amplifier circuit is used.

[0007]

According to the present invention, there are provided first to fourth aspects.
An output amplifier circuit, first and second loads each having one end connected to the first and fourth output amplifier circuits, and a non-linear addition circuit for non-linearly adding output signals of the first to fourth output amplifier circuits, A non-linear amplifier circuit, which amplifies an input signal to generate an input signal of the first to fourth output amplifier circuits and controls an output DC voltage in accordance with an output signal of the non-linear addition circuit; Connecting the output terminals of the second and third output amplifier circuits to the other ends of the first and second loads in accordance with the level of at least one output signal of the first to fourth output amplifier circuits. And a switching circuit for selectively switching between the two.

The switching circuit connects the first and second loads in series when at least one of the input signal and the output signal of the output amplifier circuit is smaller than a first reference signal. When the signal is higher than the reference signal, the second output amplifier circuit is connected to the other end of the first load, and the third output amplifier circuit is connected to the other end of the second load.
The switching circuit further includes a third load inserted between the first and second loads, and the switching circuit includes an output terminal of the second output amplifier circuit, the other end of the first load, and a third load. First switching means for selectively switching connection to one end; output terminal of the third output amplifier circuit; and second switching means for selectively switching connection to the other ends of the second and third loads. It is characterized by comprising.

Still further, the first and second switching means are configured to connect the first to third loads in series when at least one of the input signal and the output signal of the output amplifier circuit is smaller than a second reference signal. Connecting to connect the second output amplifier circuit to the other end of the first load when between the second reference signal and a higher third reference signal;
The third output amplifying circuit is connected to the other end of the second load, and when the third output signal is higher than the third reference signal, the output end of the second output amplifying circuit, the other end of the first load, and the third load. One end is connected, and the output end of the third output amplifier circuit is connected to the other ends of the second and third loads.

Further, a selecting circuit for selecting the highest level output signal from the output signals of the first to fourth output amplifying circuits, and the first to fourth output circuits based on the output signal of the selecting circuit. And a regulator for generating a power supply voltage of the amplifier circuit. According to the present invention,
The output terminals of the second and third output amplifier circuits are selectively connected to the first and second loads, respectively, according to the level of the input signal. In particular, if the input signal level is lower than the reference signal, the first and second loads are directly connected, the first and second loads are regarded as one load, and the first and fourth output amplifier circuits are connected to the first and fourth outputs. When the input signal level is higher than the reference signal, the second and third loads are applied to the first and second loads.
The output terminals of the output amplifier circuits are respectively connected, the first and second output amplifier circuits drive the first load by BTL, and the third and fourth output amplifier circuits drive the second load by BTL. Therefore,
Even if the connection of the first to fourth output amplifier circuits is changed with respect to the load, the first and second loads are always driven by the BTL.

[0011]

FIG. 1 is a diagram showing an embodiment of the present invention. Numeral 10 denotes a non-linear amplifier circuit for amplifying an input signal and generating a DC voltage close to the ground.
Amplifies the positive and negative output signals of the non-linear amplifier circuit 10, respectively, and an output amplifier circuit BTL-connected to the load 8;
Reference numerals 13 and 14 amplify the positive and negative output signals of the nonlinear amplifier circuit 10, respectively, and BTL-connected output amplifier circuits to the load 9, and 15 a nonlinear addition circuit for nonlinearly adding the output signals of the output amplifier circuits 11 to 14. , 16 compare the output signal of the non-linear addition circuit 15 with the reference voltage Vref1,
The output signal corresponding to the difference is sent to the common terminal C of the nonlinear amplifier circuit.
, A comparison circuit 17 for comparing the level of an input signal serving as a switching signal generation circuit with a reference voltage Vref2, and 18 and 19 according to an output signal of the comparison circuit 17, A switching circuit for switching the connection between 13 and the loads 8 and 9, a selection circuit 20 for selecting the highest output signal among the output signals of the output amplifier circuits 11 to 14, and a switching circuit 21 in accordance with the output signal of the selection circuit 20. , A switching regulator for generating the power supply voltage VD of the output amplifier circuits 11 to 14.

In FIG. 1, an input signal is applied to a comparison circuit 17 and compared with a reference voltage Vref2. When the input signal is higher than the reference voltage Vref2, the movable terminals of the switching circuits 18 and 19 are brought into the illustrated state in accordance with the output signal a of the comparison circuit 17, and the output amplifier circuits 11 and 12 are connected to the load 8; Are connected to output amplifier circuits 13 and 14. In such a connection state, the input signal is amplified by the nonlinear amplifier circuit 10, and output half-wave signals b and c having opposite phases to each other are generated from the positive and negative output terminals as shown in FIG. The output half-wave signal b is amplified by the output amplifier circuits 11 and 13, and the output half-wave signal c is amplified by the output amplifier circuits 12 and 14. The load 8 is BTL-driven by the output signals d and e of the output amplifier circuits 11 and 12, and the load 9 is BTL-driven by the output signals f and g of the output amplifier circuits 13 and 14.

When the input signal is lower than the reference voltage Vref2, the switching circuit 1
The movable terminals 8 and 19 are in the opposite state to those shown in the figure, and the load 8
And 9 are directly connected, and output amplifier circuits 11 and 14 are connected to loads 8 and 9, respectively. In this state, the output signals b and c of the nonlinear amplifier 10 are amplified by the output amplifiers 11 and 14, respectively. Output amplification circuits 11 and 1
4 are supplied to loads 8 and 9, respectively, and the loads 8 and 9 serve as BTL as one load for a set of BTL amplifier circuits composed of output amplifier circuits 11 and 14.
Driven.

Even if the input signal is lower or higher than the reference voltage Vref2, that is, even if the connection state between the loads 8 and 9 and the output amplifier circuits 12 and 13 is changed, the load is always driven by the BTL. In the case of the BTL drive, as shown in FIG. 5A, a good distortion rate can be maintained up to a large output power. Therefore, even if the connection between the load and the output amplifier circuit is switched, deterioration of the distortion factor can be prevented.

When the input signal is low, the loads 8 and 9 are connected in series. If the value of the loads 8 and 9 is RL, the value of the load is 2 · RL. Larger than the value of. In general, in a power amplifying device, when the value of a load increases for the same output signal, the current flowing through the load decreases, and power consumption can be reduced. That is, when the input signal is low, the loads 8 and 9
Can be reduced, so that power consumption can be reduced. Therefore, the circuit of FIG. 1 can achieve both a reduction in power consumption and a favorable distortion factor.

The output signals d to g of the output amplifier circuits 11 to 14 are nonlinearly added by a nonlinear addition circuit 15. The nonlinear addition circuit 15 operates as an addition circuit when the levels of the output signals d and g are equal to or lower than a predetermined level, and operates as a clamp circuit when the levels of the output signals d to g are equal to or higher than the predetermined level. The output signal of the non-linear addition circuit 15 is applied to the negative input terminal of the differential amplification circuit 16,
This is compared with the reference voltage Vref1 of the positive input terminal. The differential amplifier circuit 16 generates an output signal corresponding to the difference between the output signal of the nonlinear addition circuit 15 and the reference voltage Vref1, and is applied to the common terminal C of the nonlinear amplification circuit 10. The output DC voltage of the nonlinear amplifier circuit 10 is controlled by the input signal of the common terminal C, and the output DC voltage of the nonlinear amplifier circuit 10 is set to a level close to the ground as shown in FIG. Therefore, as shown in FIG. 3, the output signals d to g of the output amplifier circuits 11 to 14 are output.
Is a half-wave output signal.

As described above, since the DC output voltage is always controlled to a constant value, the DC output voltage does not change even if the power supply voltage Vcc changes. Therefore, even if the power supply voltage Vcc fluctuates, the level of the input signal and the output signal of the output amplifier circuit correspond to 1: 1. Therefore, the load connection can be switched at a predetermined level regardless of the fluctuation of the power supply voltage Vcc. Done. Further, since the input signal and the output signal of the output amplifier circuit correspond to 1: 1 regardless of the power supply voltage Vcc, switching can be performed using a circuit having a simple circuit configuration such as a comparison circuit.

On the other hand, the output signals d to g of the output amplifier circuits 11 to 14 are applied to the selection circuit 20, and the highest output signal is selected. The switching regulator 21 performs a switching operation in response to the output signal of the selection circuit 20, and the switching regulator 21 applies the power supply voltage VD following the output signals of the output amplifier circuits 11 to 14 to the output amplifier circuits 11 to 14. As described above, the power consumption is further reduced by causing the power supply voltage VD to follow the output signals d to g.

FIG. 2 is a diagram showing another embodiment.
2 compares the input signal with reference voltages Vref3 and Vref,
A switching signal generating circuit for selectively generating a switching signal h, 23
Is a load, 24 is a switching circuit for switching the connection between the loads 8 and 23 and the output terminal of the output amplifier circuit 12 according to the switching signal h, and 25 is the output of the loads 9 and 23 and the output of the output amplifier circuit 13 according to the switching signal h. This is a switching circuit for switching the connection with the end. Note that the reference voltage Vref3 is lower than the reference voltage Vref4.

In FIG. 2, the input signal is a reference voltage Vre
When it is lower than f3, the switching signal h of the switching signal generation circuit 22 is output.
Thus, the switching circuits 24 and 25 are switched so that the loads 8, 9 and 23 are connected in series. Therefore, the loads 8, 9 and 23 are BTL-driven by a set of BTL amplifier circuits composed of the output amplifier circuits 11 and 14. Therefore, similarly to FIG. 1, when the input signal is low, the current flowing through the loads 8, 9 and 23 decreases, and the power consumption can be reduced.

When the input signal is between the reference voltages Vref3 and Vref4, the switching signal h connects the load 8 to the output terminal of the output amplifier circuit 12, and connects the load 9 to the output terminal of the output amplifier circuit 13. Is switched to be connected. Therefore, both ends of the load 23 are open. Therefore, the load 8 is BTL-driven by the output signals d and e of the output amplifier circuits 11 and 12, and the load 9 is driven by the output amplifier circuits 13 and 1.
BTL driving is performed by the output signals f and g.

When the input signal is higher than the reference voltage Vref4, the loads 8 and 23 are connected to the output terminals of the output amplifier circuit 12, and the loads 9 and 23 are connected to the output terminals of the output amplifier circuit 13. Therefore, the load 8 is BTL driven by the output signals d and e, and the load 9 is BT driven by the output signals f and g.
At the same time, the load 23 is driven BTL by the output signals e and f of the output amplifier circuits 12 and 13.
Since the loads 23 are individually driven in addition to the BTL driving of the loads 8 and 9, the output can be increased.

That is, when the input is small, the power consumption can be reduced by connecting the loads in series, and when the input is large, the output can be further increased by driving three loads with four output amplifier circuits. Can be measured. still,
At the time of a large input, the output amplifier circuits 12 and 13 are configured to drive two loads, respectively.
Set larger.

In FIG. 1, the input signal is applied to the positive input terminal of the comparison circuit 17. However, the present invention is not limited to this, and the output signal of at least one of the output amplifier circuits 11 to 14 is applied to the positive input terminal of the comparison circuit 17. Is applied, the connection between the loads 8 and 9 and the output amplifier circuits 12 and 13 can be switched. Similarly, in FIG.
Using at least one output signal of the output amplifier circuits 11 to 14, the loads 8, 9 and 23 and the output amplifier circuit 12 are used.
And 13 can be switched.

[0025]

According to the present invention, when the input signal is higher than the reference signal, two separate loads are respectively driven by BTL, and when the input signal is lower than the reference signal, the two loads are one load. By performing the BTL driving, the load is always driven by the BTL regardless of the level of the input signal, so that the distortion of the output signal of the output amplifier circuit can be improved from low output to high output. At the time of small input, two loads
Since the number of loads increases the value of the load, the current flowing to the load for the same input signal decreases,
Power consumption can be reduced.

Loads are further connected in series between the above two loads, and when the input is small, the three loads are set to one and the BTL drive is performed. When the input is medium, the two loads are respectively connected to the BTL as described above. Drive, and when large input, three loads are individually BTL
Since the driving is performed, not only the distortion factor can be improved and the power consumption can be reduced, but also the output can be increased when the input is large. Also,
By changing the power supply voltage of the output amplifier circuit so as to follow the output signal of the output amplifier circuit, it is possible to further reduce power consumption.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

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

FIG. 3 is a waveform chart showing output waveforms of the respective circuits of FIGS. 1 and 2.

FIG. 4 is a block diagram showing a conventional example.

FIG. 5 is a characteristic diagram showing a relationship between output power, distortion factor, and power consumption.

[Explanation of symbols]

 8, 9, 23 Load 10 Non-linear amplification circuit 11, 12, 13, 14 Output amplification circuit 15 Non-linear addition circuit 16 Differential amplification circuit 17 Comparison circuit 18, 19, 24, 25 Switching circuit 20 Selection circuit 21 Switching regulator 22 Switching signal Generator circuit

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Takayuki Taira 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (5)

[Claims] 1. A first to a fourth output amplifying circuit, a first and a second load having one ends connected to the first and a fourth output amplifying circuits, respectively, and an output of the first to the fourth output amplifying circuits. A non-linear addition circuit for non-linear addition of signals; an input signal is amplified to generate input signals of the first to fourth output amplifier circuits; and an output DC voltage is controlled according to an output signal of the non-linear addition circuit. A non-linear amplifier circuit; an output terminal of the second and third output amplifier circuits according to a level of the input signal or at least one output signal of the first to fourth output amplifier circuits; And a switching circuit for selectively switching connection with the other end of the second load. 2. The switching circuit, comprising: connecting a first and a second load in series when at least one of the input signal and the output signal of the output amplifier circuit is smaller than a first reference signal; 2. The electric power according to claim 1, wherein the second output amplifier circuit is connected to the other end of the first load and the third output amplifier circuit is connected to the other end of the second load when the signal is higher than the reference signal. Amplifying device. 3. The switching circuit further includes a third load inserted between the first and second loads, wherein the switching circuit includes an output terminal of the second output amplifying circuit, another end of the first load, and a third terminal. First to selectively switch connection with one end of three loads
2. The switching device according to claim 1, further comprising a switching unit, and an output terminal of the third output amplifying circuit, and a second switching unit that selectively switches connection between the other end of the second and third loads. Power amplification device. 4. The first and second switching means, wherein when at least one of the input signal or the output signal of the output amplifier circuit is smaller than a second reference signal, the first and third loads are connected in series. When the signal is between the second reference signal and a third reference signal higher than the second reference signal, the second output amplifier circuit is connected to the other end of the first load, and the third output amplifier circuit is connected to the third load signal. The second output amplifier circuit is connected to the other end of the second load, the other end of the first load, and the other end of the third load, and is connected to the other end of the third load when higher than the third reference signal. An output terminal of the three-output amplifier circuit;
4. The power amplifying device according to claim 3, wherein the power amplifying device is connected to the other end of the third load. 5. A selection circuit for selecting an output signal of the highest level from among output signals of the first to fourth output amplification circuits, and the first to fourth output amplification circuits based on an output signal of the selection circuit. 4. The power amplifying device according to claim 1, further comprising a regulator for generating a power supply voltage of the circuit.