TWI713302B - Audio amplifier structure and method with power feedback - Google Patents

Abstract

The present invention is an audio amplifier architecture and method with power feedback, including a power amplifier unit, a speaker, a current sensing unit, a voltage sensing unit, and a multiplication unit. The power amplifier unit has an input side and an output side , The input side inputs an audio voltage signal; and the speaker is electrically connected to the output side of the power amplifier unit; and the current sensing unit is electrically connected to the output side of the power amplifier unit and senses the output current of the power amplifier unit and converts it into a current control Voltage signal; and the voltage sensing unit is electrically connected to the output side of the power amplifier unit, and senses the output voltage of the power amplifier unit to form an output sensed voltage signal; and the multiplication unit obtains the current control voltage and outputs the sensed voltage multiplied by the voltage , And the output side of the multiplying unit is electrically connected to the input side of the power amplifier unit to form a closed-loop power feedback structure; thereby, the output quality of the amplifier and the speaker can be improved.

Description

Audio amplifier structure and method with power feedback

The present invention relates to an audio amplifier structure and method with power feedback, and mainly refers to a structure and method for controlling the output power of the amplifier by power feedback and improving the output quality of the speaker.

Please refer to Figure 7 for a conventional audio amplifier circuit structure, with a power amplifier 1', a speaker 2'arranged on the output side of the amplifier 1', and the input side of the power amplifier 1'is connected to a negative feedback resistor R2 and a resistor R1 is grounded. The audio voltage Vin is input from the positive terminal of the power amplifier 1'. The output voltage of the power amplifier 1'is VO=Vin*(R2/R1+1), so the output power of the power amplifier 1'PO=(VO) ² /ZL.

However, the DC impedance ZL of the speaker 2'is not a fixed value, generally about 4~16Ω, and its AC impedance in the audio range of 20~20KHZ shows a non-linear change as shown in Figure 8, so the conventional power amplifier 1' In practice, as shown in Figure 9, under the same input audio voltage Vin, the different DC impedance ZL of the speaker 2'will not cause the output voltage VO to be different, but as shown in Figure 10, the impedance ZL change will directly cause the same The output power PO of the power amplifier 1'is different under the signal level of the input audio voltage Vin signal. This phenomenon will cause damage to the amplifier with insufficient maximum power capacity, and the inherently uneven frequency/impedance characteristics of the speaker 2'will cause replay of music Distortion and poor output quality are missing.

Therefore, although high-quality speakers can improve the output sound quality, it is still difficult to overcome the lack of output distortion caused by the frequency/impedance characteristics of the speakers.

The object of the present invention is to provide a structure and method for controlling the output power of the amplifier by power feedback and improving the output quality of the speaker.

The architecture of the present invention includes a power amplifying unit, a speaker, a current sensing unit, a voltage sensing unit, and a multiplication unit; the power amplifying unit can be a class A, AB, D, and G amplifier, which can be Single-ended amplification or bridge connection (BTL) architecture with an input side and an output side. The input side inputs audio voltage signals; the speaker is electrically connected to the output side of the power amplifier unit; and the current sensing unit is electrically connected to the power amplifier The output side of the unit senses the output current of the power amplifying unit and converts it into a current control voltage signal; and the voltage sensing unit is electrically connected to the output side of the power amplifying unit, and senses the output voltage of the power amplifying unit to form an output sensing voltage Signal; and the input side of the multiplication unit is electrically connected to the current control voltage signal and the output sense voltage signal, and the current control voltage and the output sense voltage are multiplied by the voltage, and the output side of the multiplication unit is electrically connected to the power amplifier unit input And form a closed-loop power feedback architecture.

The method of the audio amplifier with power feedback of the present invention includes: setting a power amplifying unit which outputs to a speaker; capturing the output current signal output by the power amplifying unit to the speaker; capturing the voltage signal output by the power amplifying unit; The current signal and the voltage signal are multiplied to obtain the output power level signal and then fed back to the input side of the power amplifier to form a feedback closed loop structure, and the output of the power amplifier unit maintains a constant output power.

Further, the output current signal of the present invention is converted into a current control voltage signal; and the output voltage of the power amplifying unit is converted into an output sensed voltage signal by voltage division; A multiplication unit is included. The current control voltage signal and the output sensed voltage signal are input to the multiplication unit for multiplication, and the multiplication unit outputs the product to be fed back to the input side of the power amplification unit.

When the present invention is implemented, the impedance variation of the speaker will not cause the output power of the power amplifier unit to be different under the same input audio voltage Vin signal level, so the inherently uneven frequency/impedance characteristics of the speaker can be improved, and the output distortion can be reduced A better original sound quality is obtained, and the input audio voltage signal level of the present invention is locked by the feedback circuit to obtain an accurate output power. The power amplifier unit will not be damaged due to the change of speaker impedance, and it can have a better service life.

1: Power amplifier unit

2: speaker

3: Current sensing unit

31: Gain device

A1: Amplifier

4: Voltage sensing unit

5: Multiplication unit

P1~P4: amplifier

R1~R27: resistance

T1~T3: current sensing transformer

1’: Power amplifier

2’: Speaker

Figure 1 is a block diagram of the audio power amplifier of the present invention.

FIG. 2 is a schematic diagram of the circuit structure of the first embodiment of the audio power amplifier of the present invention.

Figure 3 is a schematic diagram of output power versus speaker impedance of the first embodiment of the audio power amplifier of the present invention.

Figure 4 is a schematic diagram of output voltage versus speaker impedance of the first embodiment of the audio power amplifier of the present invention.

Fig. 5 is a schematic diagram of the circuit of the second embodiment of the audio power amplifier of the present invention.

Fig. 6 is a circuit diagram of the third embodiment of the audio power amplifier of the present invention.

Figure 7 is a schematic diagram of the conventional audio power amplifier architecture.

Figure 8 is a schematic diagram of the speaker frequency versus impedance characteristic of the conventional audio power amplifier architecture.

Figure 9 is a schematic diagram of the output voltage versus speaker resistance of the conventional audio power amplifier architecture.

Figure 10 is a schematic diagram of output power versus speaker impedance of the conventional audio power amplifier circuit architecture.

Please refer to Figure 1. The present invention includes a power amplifying unit 1, a loudspeaker 2, a current sensing unit 3, a voltage sensing unit 4, and a multiplying unit 5. The power amplifying unit 1 can be of type A, type AB, Class D and Class G amplifiers can be single-ended amplification or bridge connection (BTL) architecture, with an input side and an output side. The positive input of the input side inputs the audio voltage Vin signal.

The speaker 2 is electrically connected to the output side of the power amplifier unit 1.

The current sensing unit 3 is electrically connected to the output side of the power amplifying unit 1, and senses the output current of the power amplifying unit 1 and then converts it into a current control voltage signal.

The voltage sensing unit 4 is electrically connected to the output side of the power amplifying unit 1 and senses the output voltage of the power amplifying unit 1 to form an output sensed voltage signal.

The input side of the multiplication unit 5 is electrically connected to the current control voltage signal of the current sensing unit 3 and the output sensing voltage signal sensed by the voltage sensing unit 4, and obtains the current control voltage and the output sensing voltage multiplied by the voltage, and the multiplication The output side of the unit 5 is electrically connected to the negative input terminal of the input side of the power amplifying unit 1 and forms a closed loop power feedback structure.

Please refer to Figure 2 which is a schematic diagram of the circuit architecture of the first embodiment of the present invention. The power amplifying unit 1 has an amplifier A1, and the positive input terminal of the amplifier A1 inputs an audio voltage Vin signal, and the output is connected to a speaker 2. The speaker 2 has an impedance ZL, and The current sensing unit 3 has a current sensing resistor R5 that is much smaller than the impedance ZL of the speaker 2 and a gain device 31, and outputs to the multiplication unit 5; and the voltage sensing unit 4 has voltage divider resistors R3, R4 electrically connected to the amplifier A1 On the output side, the output sensing voltage is generated and input to the multiplication unit 5, and the multiplication unit 5 is output to the negative input terminal of the amplifier A1.

The input audio voltage Vin signal of the present invention is amplified by the amplifier A1 by AV times. The rear speaker 2 has an output power PO of (Vin*AV) ² /ZL. The output power PO can be a linear function of the input voltage Vin under a fixed load condition PO=F(Vin), so the level of the input voltage Vin can reflect the output power PO.

The amplifier A1 has a very high closed-loop gain, generally greater than 80dB, so negative feedback must be added to stabilize the gain and increase the bandwidth. When the level of Vin changes, the change is amplified by the amplifier A1 to make the speaker 2 appear amplified The voltage is changed and the current IO of the output voltage VO/ZL is generated, and the output power PO of the speaker 2 is VO*IO=VO ² /ZL.

The voltage dividing resistors R3 and R4 of the voltage sensing unit 4 are connected to the output voltage VO of the power amplifying unit 1, and the resistor R4 generates the output sensing voltage M1, set A=R4/(R3+R4), the M1=A*VO , And the M1 is input to the input side of the multiplication unit 5; and the resistor R5 of the current sensing unit 3 is connected in series with the speaker 2 to obtain a voltage signal that reflects the output current IO. The voltage signal is amplified by the gain device 31 by G times to generate a current control voltage Signal M2.

Set B=R5*G; the M2=B*IO=B*VO/ZL, the current control voltage signal M2 is input to the input side of the multiplication unit 5, and the output of the multiplication unit 5 MO=M1*M2, the MO is The product of the output sensing voltage M1 formed by the output voltage VO and the current control voltage M2 formed by the response output current IO is reflected, and the power level is obtained and then fed back to the negative input of the amplifier A1 to form a closed loop control power amplification system.

Please refer to Figure 2~Figure 4 together, because the positive and negative input voltages of the amplifier A1 of the closed-loop power amplifier system are the same. Vin=MO; the MO=(A*VO)*(B*VO/ZL)=A* B(VO ² /ZL); Set A*B=S; the MO=S*(VO ² /ZL)=Vin, so when the same audio voltage Vin signal is input but the impedance ZL of the speaker 2 changes, the output voltage VO must correspond to changes such that MO=S*(VO1/ZL1)=S*(VO2/ZL2)=S*(VO3/ZL3), the conversion characteristics of the closed-loop power amplifier system will meet the output power PO=F(Vin) The function relationship of the output power PO=VO1 ² /ZL1=VO2 ² /ZL2=VO3 ² /ZL3……VON ² /ZLN, can have a constant output power PO=K*Vin, the output power PO and the speaker 2 impedance ZL In the working range of the amplifier system, it is no longer related to the impedance ZL of the speaker 2, so it will not cause distortion of the output power variation.

Please refer to Figure 5 of the second embodiment of the present invention. The second embodiment mainly has a power amplifier unit 1, a speaker 2, a current sensing unit 3, a voltage sensing unit 4, and a multiplying unit 5. Unit 1 is mainly composed of resistors R6, R7, and amplifier P1. Its positive input terminal is connected to the audio voltage Vin signal and has a power amplification ratio; and the current sensing electrical unit 3 mainly has a current sensing transformer T1 and resistor R8 to connect power The output side of the amplifier P1 of the amplifying unit 1, and senses the output current of the amplifier P1 and obtains the current control voltage signal and inputs it to the multiplication unit 5; and the voltage sensing unit 4 is connected to the output side of the power amplifying unit 1, and has a voltage divider resistor R9, R10 obtains the output sensed voltage signal and inputs it to the multiplication unit 5; and the multiplication unit 5 has a multiplier U1, the output of the multiplier U1 is fed back to the negative input terminal of the input side of the amplifier P1, and the current control voltage signal and output sense The measured voltage signal is multiplied by the multiplier U1 to obtain the response output power information and fed back to the amplifier P1, so that the amplifier P1 can respond to the impedance change of the speaker 2 to maintain a constant output power.

Please refer to Figure 6 of the third embodiment of the present invention. The third embodiment is similar to the second embodiment with a power amplifier unit 1, a speaker 2, a current sensing unit 3, a voltage sensing unit 4, and a The multiplying unit 5 is a BTL bridge structure that can double the input voltage. The power amplifying unit 1 mainly has a non-inverting amplifier composed of resistors R13, R14, and amplifier P2, and an inverted amplifier composed of resistors R15, R16, and amplifier P3. A phase amplifier, and the positive and negative input terminals of the amplifiers P2 and P3 input audio voltage Vin+ and Vin- signals respectively; the amplifiers P2 and P3 output to the speaker 2, and the current sensing unit 3 mainly has two current sensing transformers T2, T3, and resistor R17 are electrically connected to the output sides of the amplifiers P2 and P3, respectively, and sense the output current of the amplifiers P2 and P3 to obtain a current control voltage signal and input to the multiplication unit 5; and the voltage sensing unit 4 has a voltage divider resistor R18 , R19 is connected to the output side of the amplifier P2 and the voltage divider resistors R20 and R21 are connected to the output side of the amplifier P3 to obtain the sensed voltages output by the amplifiers P2 and P3 respectively; another is composed of the amplifier P4, resistors R22, R23, R24, R25 The input side of the adder circuit inputs the aforementioned two sensing voltages respectively, and outputs the output sensing voltage having the sum of the two sensing voltages; and the multiplication unit 5 has a multiplier U2, and inputs the aforementioned current control voltage and output sensing voltage Multiplied to form a voltage reflecting the output power and then fed back to the input side of amplifiers P2 and P3, and can reflect the change in impedance of the speaker 2 to maintain a constant output power.

Therefore, based on the above, the present invention improves the speaker of the conventional audio amplifier in different audio frequencies, resulting in distortion of the sound quality and loss of the amplifier withstand large fluctuations in power, which is vulnerable to damage. The foregoing embodiments are examples of creation, and are not a limitation of this creation. All equivalent changes made in accordance with the spirit of this creation should also fall within the scope of this creation.

1: Power amplifier unit

2: speaker

3: Current sensing unit

4: Voltage sensing unit

5: Multiplication unit

Claims (10)

An audio amplifier structure with power feedback, including: a power amplifier unit with an input side and an output side, the input side inputs audio voltage signals; a speaker electrically connected to the output side of the power amplifier unit; and a current sensing The unit is electrically connected to the output side of the power amplifier unit and senses the output of the power amplifier unit to the speaker and converts the output current from the speaker into a current control voltage signal; a voltage sensing unit is electrically connected to the output side of the power amplifier unit and senses The output voltage of the power amplifier unit forms an output sensed voltage signal; a multiplication unit, the input side is electrically connected to the current control voltage signal and the output sensed voltage signal, and the current control voltage and the output sensed voltage are multiplied by the voltage, and the multiplication The output side of the unit is electrically connected to the input side of the power amplifier unit to form a closed loop power feedback structure. The audio amplifier architecture with power feedback according to claim 1, wherein the power amplifying unit can be a single-ended amplifier or a bridge connection (BTL) architecture. The audio amplifier architecture with power feedback according to claim 1, wherein the voltage sensing unit has a voltage divider resistor to generate an output sensing voltage. The audio amplifier architecture with power feedback according to claim 1, wherein the current sensing unit can have a current sensing resistor. The audio amplifier architecture with power feedback according to claim 1, wherein the current sensing unit may have at least one current sensing transformer. A method for an audio amplifier with power feedback includes: setting a power amplifying unit, the power amplifying unit inputs an audio voltage signal and outputs to a speaker; capturing the power amplifying unit to output to the speaker and the speaker to output current signals; Take the power amplifier unit to output a voltage signal; the current signal and the voltage signal are multiplied to obtain the output power level signal and then fed back to the input side of the power amplifier to form a feedback closed loop structure. The method for an audio amplifier with power feedback according to claim 6, wherein the output current signal is converted into a current control voltage signal; and the output voltage of the power amplifier unit is divided into an output sensed voltage signal; and A multiplication unit, the current control voltage signal and the output sensing voltage signal are input to the multiplication unit for multiplication, and the multiplication unit then outputs the product to the input side of the power amplification unit. The method for an audio amplifier with power feedback according to claim 6, wherein a current sensing unit is electrically connected to the power amplifier unit and the output current signal of the power amplifier is captured. The method for an audio amplifier with power feedback according to claim 8, wherein the current sensing unit has a current sensing resistor. The method for an audio amplifier with power feedback according to claim 8, wherein the current sensing unit has at least one current sensing transformer.

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