KR100334889B1 - Multi-combination linear power amplifier - Google Patents

Abstract

The present invention relates to a multiple coupled linear output amplifier suitable for an audio power amplifier by combining two or more analog and switching power amplifiers.

The present invention is characterized by sharing the sophistication of the waveform and the output power by connecting in a predominant relationship so as to control an amplifier having a large power and a relatively large distortion, based on an analog amplifier having a small power but a low distortion. In addition, the outputs of each amplifier are connected to each other through an inductor, and have a structure in which a positive feedback loop and an input signal passing through multiple negative feedback loops and differential circuits are connected to the input terminals of each amplifier. And maximum efficiency can be achieved at the same time.

Description

Multi-combination linear power amplifier

FIELD OF THE INVENTION The present invention relates to linear power amplifiers and, more particularly, to multiple linear output amplifiers combining two or more analog power amplifiers to be suitable for application to audio power amplifiers.

In general, audio power amplifiers occupy most of the linear heavy amplifiers classified into class A, B, AB, etc. according to the structure of the output stage, and recently, switching power amplifiers classified into class D have been proposed.

These power amplifiers tend to conflict with each other in terms of efficiency and distortion. In more detail, the difference is worsened in the order of class A → AB → B → D from the viewpoint of distortion and in the order of D → B → AB → A from the viewpoint of efficiency.

Considering that a class A amplifier with distortion of class A would be the most desirable form if it had an efficiency of class D, attempts have been made to combine analog and digital switching amplifiers. As described above, in the case of implementing a new amplifier by combining two or more types of analog amplifiers, various differences are shown as described with reference to FIGS. 1A to 1C according to the coupling method.

First, FIG. 1A illustrates a configuration in which two analog power amplifiers A1 and A2 are simply connected in parallel, and are used to increase power gain. In such a configuration, if the balance of two amplifiers A1 and A2 connected in parallel is harmonized, a power gain of about twice can be obtained. However, a linear amplifier constructed according to the coupling scheme shown in FIG. There is no advantage other than the augmentation effect, but rather a slight imbalance between the two amplifiers, there is a problem that excessive current flows between the two amplifiers.

FIG. 1B is a configuration for improving the problem of the linear amplifier shown in FIG. 1A. The first analog power amplifier A1 is used as a main amplifier, and the second amplifier A2 is a sub amplifier serving as an auxiliary. Leads to. As shown, the output current io1 of the first analog power amplifier A1 is detected at the current detection node SN1 and input to the second analog power amplifier A2, which is a sub amplifier, whereby the first analog power amplifier The output power io2 of A1 is adjusted.

However, the configuration illustrated in FIG. 1B is difficult to design a feedback loop around the second analog amplifier A2, and has a problem in that oscillation due to instability cannot be solved.

FIG. 1C is an improvement of the coupling scheme of the master-slave relationship illustrated in FIG. 1B. The output current io1 of the analog power amplifier A1 as the main amplifier is sensed at the current detection node SN1 to provide a switching power amplifier SA3. An inductor L1 is inserted to supply an input and generate an output current io2 from the amplifier SA3, and to filter a pulse width modulation output waveform of the amplifier SA3. It is a form.

However, the configuration in which the amplifier SA3 and the amplifier A1 are combined in this way can improve the efficiency and the sound quality at the same time when used in the audio power amplifier, but the load Zo according to the magnitude of the inductance component of the inductor L1. There is a problem in that switching noise and ripple current cannot be prevented from occurring at the final output io of.

Therefore, the present invention has been proposed to solve the above-mentioned problems of the prior art, and the present invention is to provide a multi-coupled linear power amplifier with low distortion and high efficiency by combining two or more analog power amplifiers. According to the present invention for achieving the above object, a multiple-coupled linear power amplifier comprises: a first amplifier A1 as a main amplifier to which an input signal source Vin is connected; A second amplifier as a sub amplifier connected in parallel to the output terminal of the first amplifier A1 and to which an output current io1 detected at the current detection node SN1 of the first amplifier A1 is applied as an input; A2); An inductor (L1) connected between the current detection node (SN1) of the first amplifier (A1) and the output terminal of the second amplifier (A2); The output of the second amplifier A2 is connected to the point where the output terminal of the first amplifier A1 is connected to the load Zo via the current detection terminal SN1 through the inductor L1, The feedback loop loop 1 formed by the second amplifier A2, the inductor L1 and the current detection node SN1 of the first amplifier A1 acts as a negative feedback loop.

1A is a circuit diagram of a prior art in which two analog power amplifiers are connected in parallel;

1B is a circuit diagram of a prior art in which two power amplifiers are connected in a predominant relationship;

1C is a circuit diagram of a prior art in which analog amplifier A1 and switching amplifier SA3 are coupled in a predominant relationship;

2A is a circuit diagram of a multi-coupled linear power amplifier of the present invention in which two analog amplifiers A1 and A2 are coupled in a predominant relationship using an inductor L1,

FIG. 2B is a board diagram illustrating the characteristics of loop 1 of the circuit shown in FIG. 2A;

3 is a circuit diagram of a multi-coupled linear power amplifier of the present invention in which two analog amplifiers A1 and A2 are combined in a feedforward and a feedback manner;

4 is a circuit diagram of a multiple-coupled linear power amplifier in which a loop 2 is formed by adding a switching amplifier SA3 and an inductor L2 in FIG.

FIG. 5 is a circuit diagram of a multi-coupled linear power amplifier in which a feedforward is added to the circuit of FIG. 4, and FIG. 6A shows a differential positive feedback loop proportional to the output current io in the basic configuration of FIG. Circuit diagram of a multi-coupled linear power amplifier formed around the

6B is a circuit diagram of a multiple-coupled linear power amplifier in which a differential positive feedback loop is formed in the basic configuration of FIG. 3 in proportion to the output current io2 of the second analog power amplifier.

6C is a circuit diagram of a multiple-coupled linear power amplifier in which a differential winding loop is formed around a second analog power amplifier by winding a secondary winding around an inductor L1 in the basic configuration of FIG.

7 is a circuit diagram of a multiple-coupled linear power amplifier in which a differential positive feedback loop is added to an input of a switching power amplifier in the structure of FIG.

8A is a circuit diagram illustrating the structure of a basic analog amplifier;

8B is a circuit diagram showing the basic structure of a switching amplifier using pulse width modulation (PWM);

8C is a circuit diagram showing the basic structure of a switching amplifier using hysteresis;

9 illustrates one specific circuit of an analog amplifier,

10 is a circuit diagram illustrating a connection diagram configuration of an amplifier corresponding to the structure of FIG. 3;

FIG. 11 is a circuit diagram of a circuit configured to detect an output current of a second analog power amplifier using a transformer in FIG. 10 and to connect the differential signal to the input of the second analog power amplifier through a capacitor.

Explanation of symbols on the main parts of the drawings

A2: Analog Power Amplifier SA3: Switching Power Amplifier

SN1 ~ SN5: Current Sensing Node L1, L2: Inductor

CP: Comparator T1: Transformer

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2A shows a circuit diagram of a multiple-coupled preceding power amplifier constructed in accordance with a first embodiment of the present invention. The first embodiment of the present invention is a first analog power amplifier A1 which is a main amplifier, a second analog power amplifier A2 which is a sub amplifier connected in parallel to the output terminal of the first amplifier A1, and a second amplifier. The inductor L1 is connected between the output terminal of A2 and the output terminal of the first amplifier A1, and the load Zo is connected to the connection point between the output terminal of the first amplifier A1 and the inductor L1. Has a configuration. At this time, the output current io1 detected at the transfer detection node SN1 of the first amplifier A1 is supplied to the input terminal of the second amplifier A2.

In the configuration shown in FIG. 2A, the output current io2 of the second amplifier A2 serves as a dependent current source controlled in proportion to the output current io1 of the first amplifier A1.

That is, the output voltage Vo applied across the load Zo is generated by the final output current io, where io, io1, and io2 have a relationship of Equation (1). Therefore, the gain of the second amplifier A2 is sufficiently large, and the gain T of the first feedback loop loop 1 in which the second amplifier A2 and the inductor L1 are formed through the current detection node SN1 is Large enough in the audible frequency band | T | 1 has a relationship of | io2 | | io1 | Condition is true. Therefore, the first amplifier A1 can supply a large load current io at its output terminal only by supplying a small current. Therefore, if the first feedback loop is well designed, the first amplifier A1 is responsible for the sophisticated waveform amplification even with a small power, and the second amplifier A2 is responsible for most of the output although it is less accurate. It is possible to operate with.

On the other hand, Figure 2b is a board diagram illustrating the characteristics of the feedback loop (loop 1) in the linear amplifier illustrated in Figure 2a, the loop gain (T) is a function of the frequency (ω), excitation The slope that varies from -3dB frequency ω ₁ to unity gain frequency ω ₂ is formed at -20dB / decade under the influence of the inductance component of inductor L1.

The configuration illustrated in FIG. 2A can ensure the safety of the amplifiers, thus designing the first amplifier A1 with a low distortion and sophisticated structure, and designing the second amplifier A2 with high output high efficiency so that these two amplifiers are inductors. By combining the main and slave through (L1), it is possible to construct a new type of multi-coupled linear power amplifier that satisfies both precision and high efficiency at the same time. As such, a structure in which two analog amplifiers are combined is the technical spirit of the present invention.

However, although the configuration of the amplifier of FIG. 2A is not a problem in principle, there is a problem that it is difficult to guarantee reliable operation due to the characteristics of the nonlinear amplifier for the dynamic input large input signal.

FIG. 3 shows the basic configuration of a more stable multi-coupled linear power amplifier by adding additional components to the configuration of the amplifier illustrated in FIG. 2A. The amplifier according to the second embodiment of the invention illustrated in FIG. 3 is in parallel with a first analog amplifier A1 as a main amplifier provided with an input voltage from a signal source Vin and with an output terminal of the first amplifier A1. The second analog amplifier A2 as a sub-amplifier connected to the inductor, the inductor L1 connected between the output terminal of the first amplifier A1 and the output terminal of the second amplifier A2, and the first amplifier A1. The first attenuator 10 for adjusting gain by multiplying the first coupling coefficient a1 by the output current io1 detected at the current detection node SN1 of the < RTI ID = 0.0 > 1, < / RTI > and the second coupling coefficient a2 to the input signal Vin. A second attenuator 20 for multiplying the gain by multiplying) and an adder 15 for summing the outputs of the first and second attenuators 10 and 20 and providing them as inputs to the second amplifier A2. According to the above-described configuration, the negative feedback loop loop 1 is formed by the current amplifier node SN1 of the second amplifier A2, the inductor L1, and the first amplifier A1.

According to the amplifier of FIG. 3, even when a large signal is suddenly applied to the input Vin, the output current io of the load Zo can be controlled more stably than in the case of FIG. 2A, which depends only on the feedback loop 1. It is possible to overcome the nonlinearity of the large signal of the loop (loop 1). In such a structure, it is easy to design a feedback loop 1 including the second amplifier A2, the inductor L1, and the first attenuator 10, and there is an advantage in that the stability of the feedback circuit can be easily improved.

That is, in FIG. 2A, if the gain of the feedback loop loop 1 is not large enough, | io1 | The condition of | io2 | cannot be satisfied. In other words, in order to design | io1 | small enough, the loop gain must be designed large, and as the loop gain increases, the factor of instability increases.

On the other hand, the fact that the output signal (Vout) should be in the form of a constant gain as a function of the input signal (Vin), it is already known that by adding a feed forward path to the input of the second amplifier (A2) Can solve unstable factors.

A path for adding the input signal Vin to the input of the second amplifier A2 of FIG. 3 by multiplying the second coupling coefficient a2 of the second attenuator 20 performs this role, thereby designing a feedback loop. Ease of use and linearity and stable operation are guaranteed even with instantaneous changes and magnitudes in the input signal.

4 to 7 illustrate various other forms of embodiments that complement and evolve the basic configuration of FIG. 3. The amplifier of the embodiment illustrated in FIG. 4 is based on the configuration of FIG. 3 and the second amplifier A2. Output current io2 is detected at the second current detection node SN2 to control the output current io3 of the switching power amplifier SA3, and a second inductor L2 is provided at the output terminal of the amplifier SA3. It is connected to the second node SN2 of the second amplifier A2, and another feedback loop loop 2 is formed through the second node SN2. According to this configuration, the current io flowing through the load Zo is expressed by the following expression (2). Here, the output current of each power amplifier is | io1 | | io2 | | io3 | If it is controlled to have a relation of, it is a structure that produces a higher output.

In this form, even if the amplifier forming the feedback loop loop 2 is the switching power amplifier SA3, the switching ripple generated therefrom is absorbed at the output of the second amplifier A2 and thus hardly appears at the final output Vout. A clean waveform can be obtained. Therefore, the efficiency of the multiple coupling amplifier as a whole depends on the switching power amplifier SA3, and the precision of the final output waveform is assumed by the first amplifier A1 and the second amplifier A2 serves as an intermediate buffer. Done.

FIG. 5 is a modified embodiment of the configuration of FIG. 4. The output current io2 detected at the second current detection node SN2 of the second amplifier A2 is multiplied by the third coupling coefficient b1 to adjust gain. Gain adjustment by the third attenuator 30, the fourth attenuator 40 which multiplies the input signal Vin by the fourth coupling coefficient b2, and adjusts the gain, and the third and fourth attenuators 30 and 40. And an adder 25 for adding the k values to the input of the switching power amplifier SA3. Accordingly, even if a large input signal is applied to the multiple coupling amplifier of FIG. 5 within a short time, an output signal that overcomes the nonlinearity of the feedback loop can be followed. FIG. 6A shows the load Zo in the basic configuration of FIG. 3. A derivative / k product circuit 35 which detects the flowing output current io at the current detection node SN3 between the inductor L1 and the load Zo, differentiates it d / dt and adjusts it by k times Further, it is characterized in that the output of the derivative / k product circuit 35 is configured to be added by the adder 15 is applied to the input terminal of the second amplifier (A2). This configuration forms another differential loop, that is, a feedback loop (loop 3). This feedback loop has different characteristics from the feedback loops (loop 1 and loop 2).

First, the feedback loops (loop 1 and loop 2) are negative feedback loops, while the feedback loop (loop 3) is a positive feedback loop. Second, since the feedback loop (loop 3) is fed back through the derivative / k product circuit 35, the low frequency component is less affected, and the higher the frequency, the greater the influence. At this time, the feedback loop loop 3 serves to compensate for the characteristics of the inductor L1. That is, since the characteristic of the inductor L1 has the effect of attenuating the high frequency signal, there is a problem of delaying the response speed when a fast response of the high frequency component is required in the audio frequency band.

The purpose of the feedback loop (loop 3) is to compensate for this problem through the derivative / k product circuit 35. In addition, considering the fact that the required current is required differently according to the load (Zo) state, by differentially applying a value proportional to the magnitude of the load current, the current is detected to actively adapt and cope with the change in the load condition. The output current io is detected and fed back at the node SN3.

FIG. 6B shows the feedback loop loop 3 shown in FIG. 6A, the inductor L1 current (or the output current io2 of the second amplifier A2), the second amplifier A2, the first inductor L1, and It is substantially the same as the multiple-coupled linear power amplifier of FIG. 6A except that it is configured to detect at the current detection node SN4 which is a contact with the differential / k product circuit 35. That is, under the condition of | io2 || io1 | Considering that the amplifier is operated, the amplifiers of FIGS. 6A and 6B have no significant difference in terms of operation, and both of them act to speed up the response characteristic of the high frequency component and cancel the delay effect of the inductor L1.

6C differs from the configuration of the amplifier of FIG. 6B by detecting a signal from the secondary winding of the inductor L1 and feeding it back to the input of the second amplifier A2. That is, since the voltage across the inductor L1 is proportional to the derivative value of the output current io2 of the second amplifier A2, the secondary winding voltage Vl2 of the inductor L1 is also proportional to the derivative value. Becomes Therefore, when the output current io2 of the second amplifier A2 is multiplied by the coupling coefficient a3, the value of the attenuator 50 that adjusts the gain is added by the adder 15 and fed back to the input of the second amplifier A2. Differential positive feedback loop is formed.

FIG. 7 is another embodiment of FIG. 4, in which the differential loop illustrated in FIG. 6A is added to the configuration of FIG. 5. In more detail, another differential loop is formed by adding a differential circuit 35 that detects the output current io around the amplifier SA3, differentiates it (d / dt), and adjusts it by k times. do. In this configuration, it is possible to detect and differentially feedback the current of the inductor L1, but the feedback of the inductor L2 current causes a problem due to the ripple of the switching amplifier SA3.

8 to 11 illustrate a circuit for concretely realizing a multiple-coupled linear power amplifier of various configurations as described above.

8 illustrates a basic structure of an analog amplifier and a digital switching amplifier.

FIG. 8A shows a basic analog amplifier A. FIG. 8B shows an input signal Vin of the positive terminal of the comparator CP by applying a triangular wave V _SG to the negative terminal of the comparator CP. Is a basic structure of a digital switching amplifier which obtains a pulse width modulated (PWM) waveform output (Vout) in proportion to), and FIG. 8C shows positive feedback (R3, R4) so that the comparator CP has hysteresis. By comparing the output Vout by filtering (R1, R2, C1), the output waveform Vout proportional to the input signal Vin is obtained.

FIG. 9 illustrates one specific form of the analog power amplifier, and FIG. 10 is a circuit diagram specifically illustrating the configuration of the amplifier of FIG. 3.

In FIG. 10, currents flowing through the transistors QA1 and QB1 to the power transistors QA and QB of the output terminal of the first amplifier A1 are detected, and the detected currents are again generated by the transistors QA2 and QB2. 2 is applied to the input of the amplifier A2. 10 and 3, a1 = RA / RA1 = RB / RB1 and a2 = 1, and the voltage gain Av of the first amplifier A1 is designed to have a value of Av = 1 + R2 / R1. Corresponds to one circuit.

FIG. 11 illustrates the configuration of the multi-coupled linear power amplifier in FIG. 6B in detail, and further illustrates a differential positive feedback loop 3 as compared to FIG. 10.

Here, the current transformer T1 is used as a means for detecting the output current of the second amplifier A2 (or the current flowing through the inductor L1) io2, and is connected to the secondary winding of the transformer T1. The voltage across the resistor R3 is converted to the current value differentiated by the capacitors C1 and C2 and then passed through the transistors QA3 and QB3 and QA2 and QB2 to the second amplifier A2. Applied to negative (-) input terminal. Here, when the feedback loop is considered in consideration of the polarity of the transformer T1, it can be seen that a positive feedback loop is configured.

In the above manner, other multiple coupling structures in which multiple analog amplifiers and multiple switching amplifiers are combined can be configured without difficulty, but all detailed descriptions will be omitted since they are similar.

As described above, the multi-coupled linear power amplifier according to the present invention is in a variety of methods for combining multiple analog amplifiers or digital switching amplifiers in a multi-structure, the output of each amplifier is connected to one through an inductor, It consists of a feed-forward structure in which the positive feedback loop and the input signal passing through the negative feedback loop and the differential circuit are connected to the input terminal of each amplifier, thereby achieving the minimum distortion and the maximum efficiency at the same time.

Claims (9)

In a multiple coupled linear power amplifier, A first amplifier A1 as a main amplifier to which an input signal source Vin is connected; A second amplifier as a sub amplifier connected in parallel to the output terminal of the first amplifier A1 and to which an output current io1 detected at the current detection node SN1 of the first amplifier A1 is applied as an input; A2); An inductor (L1) connected between the current detection node (SN1) of the first amplifier (A1) and the output terminal of the second amplifier (A2); The output of the second amplifier A2 is connected to the point where the output terminal of the first amplifier A1 is connected to the load Zo via the current detection terminal SN1 through the inductor L1, Multiple coupling, characterized in that the feedback loop loop 1 formed by the second amplifier A2, the inductor L1 and the current detection node SN1 of the first amplifier A1 acts as a negative feedback loop. Linear power amplifier. The method of claim 1, The value obtained by multiplying the output current io1 detected at the current detection terminal SN1 of the first amplifier A1 by the first coefficient a1 and the input signal Vin by the second coefficient a2 The summation is configured to be input to the input terminal of the second amplifier (A2). The method of claim 2, A value obtained by multiplying an output current io2 detected at the current detection node SN2 of the second amplifier A2 by a third coefficient b1 and connected in parallel to an output terminal of the second amplifier A2; A third amplifier SA3, which is obtained by multiplying the input signal Vin by the fourth coefficient b2 and applied as an input; A second inductor (L2) connected between the current detection node (SN2) of the second amplifier (A2) and the output terminal of the third amplifier (SA3); A second negative feedback loop loop2 is formed in which the output of the third amplifier SA3 is fed back to the input thereof through the second inductor L2 and the second current detection node SN2. Combined linear power amplifier. The method of claim 2, A derivative connected in parallel with the second amplifier A2 and the first inductor L1 to differentiate (d / dt) the load current io detected at the current detection node SN3 at the load Zo side. Further includes a circuit, The signal differentiald by the differential circuit (d / dt) is added to the input terminal of the second amplifier (A2) by adding the value multiplied by the first coefficient (a1) and the value multiplied by the second coefficient (a2). As a result, a third feedback loop (loop 3) formed by the differential circuit is formed, and the third feedback loop is a positive feedback loop. The method of claim 2, A differential circuit connected in parallel to the output terminal of the second amplifier A2 and differentiating (d / dt) the output current io2 detected at the current detection node SN4 of the second amplifier A2 Include, The signal differentiald by the differential circuit (d / dt) is added to the input terminal of the second amplifier (A2) by adding the value multiplied by the first coefficient (a1) and the value multiplied by the second coefficient (a2). As a result, a third feedback loop (loop 3) formed by the differentiator is formed, and the third feedback loop is a positive feedback loop. The method according to claim 4 or 5, And the feedback loop is formed in such a way that the signal differentiated by the differential circuit is scaled and provided to the input terminal of the second amplifier (A2). 6. The current detection node SN2 according to claim 4 or 5, which detects the load current io and the output current io2 of the second amplifier A2 to form the feedback loop by the differentiator. SN3) are each a transformer (T1). delete 8. The multiple coupling of claim 7, wherein the transformer T1 is formed by winding a secondary winding around the first inductor L1, and forms the positive feedback loop with a voltage appearing on the secondary winding. Linear power amplifier.