CN205490435U - power amplifier - Google Patents

Abstract

The utility model discloses a power amplifying device, which comprises a pre-amplifier stage, wherein a pre-amplifier and a bass strengthening control circuit connected with the pre-amplifier in a feedback way are arranged in the pre-amplifier stage; the power amplifier stage is internally provided with an audio power output stage and a dynamic power supply voltage change-over switch, the audio power output stage is electrically connected with the pre-amplifier stage, and one input end of the dynamic power supply voltage change-over switch is connected with a smaller fixed power supply voltage; a power supply circuit connected with the other input end of the dynamic power supply voltage switch for providing a dynamic power supply voltage larger than the fixed power supply voltage to the power amplifier stage when the pre-amplifier stage enhances the bass audio signal; therefore, the utility model discloses can realize that the bass reinforces the effect and reduce circuit size, keep the surplus and the dynamic range of output simultaneously, and then reach the efficiency that improves product practicality and reliability by a wide margin.

Description

power amplifier

technical field

The utility model relates to a power amplifier, in particular to an audio frequency power amplifier with the functions of bass enhancement and dynamic power range control (boomer and dynamic power range control).

Background technique

In the field of Audio Power Amplifier (Audio Power Amplifier) technology, a variety of circuit topologies have been developed so far, including: Class A, Class B, Class AB, Class D, Class G, etc., taking Class D audio amplifier as an example , as shown in Figure 1, it has a comparison circuit 11, and the two input ends of the comparison circuit 11 respectively receive an analog audio signal 111 and a triangular wave signal 112, so that a pulse width can be obtained at the output end of the comparison circuit 11 Modulation signal, the pulse width modulation signal is sent to a drive and output stage 12 for driving and controlling the power crystal in the drive and output stage 12 to obtain an amplified pulse width modulation signal, and finally, the The amplified PWM signal passes through a low-pass filter 13 to filter out the high-frequency carrier, and then the amplified audio signal can be recovered and output by a speaker 2 .

Although the existing audio power amplifiers can realize the function of amplifying audio signals, they still face the following technical problems: First, for the currently popular miniaturized audio products, such as portable Bluetooth speakers, due to the size of the speaker unit However, due to the limitations of the environment, users often can only make a trade-off between the convenience of carrying and the shocking effect of hearing. Therefore, it is necessary to develop a small audio amplifier that can also have the function of subwoofer enhancement; secondly, with the The problem with the aforementioned bass-enhanced audio amplifier is that when the level of the bass audio is dynamically increased so that it exceeds the supply voltage of the power output stage, the amplified audio output signal will be clipped, resulting in Saturation distortion causes the speaker to crack or pop, seriously affecting the listening experience. Therefore, how to make the audio power amplifier dynamically adjust the power supply voltage to keep enough headroom when strengthening the bass level, so as to maintain a sufficient output dynamic range (dynamic range), has become a very urgent and urgent task. Practical technical issues.

Utility model content

In view of the fact that it is difficult for existing audio power amplifiers to take into account the design goals of miniaturization and enhanced bass effect at the same time, the purpose of this utility model is to develop a power amplifier that can keep the overall circuit integrated and achieve bass enhancement effect at the same time .

Another purpose of the present utility model is to develop a power amplifying device capable of realizing dynamic power range control function while strengthening bass.

In order to achieve the above object, the utility model provides a power amplification device, which includes: a preamplifier stage, a preamplifier and a bass amplifier connected to the preamplifier in a feedback mode. Strengthen the control circuit, the bass strengthening control circuit is provided with a first feedback resistor and an active capacitance multiplication circuit connected in parallel with the first feedback resistor; a power amplifier stage, the power amplifier stage is provided with an audio power output stage and A dynamic power supply voltage switching switch, the audio power output stage is electrically connected to the preamplifier stage, the dynamic power supply voltage switching switch has a first power supply voltage input terminal, a second power supply voltage input terminal and a power supply voltage output terminal, The first power supply voltage input terminal is connected to a smaller fixed power supply voltage, and the power supply voltage output terminal is connected to the audio power output stage; a power supply circuit, the power supply circuit is provided with an amplitude and phase detection circuit, a drive A circuit and a power output stage of a power supply, the drive circuit includes a reference voltage control circuit, an error amplifier bandwidth control circuit and a voltage divider circuit, the error amplifier bandwidth control circuit has a first input terminal, a second input terminal and an output terminal, and the amplitude and The phase detection circuit is electrically connected to the second input end of the preamplifier stage, the reference voltage control circuit and the error amplifier bandwidth control circuit, and the reference voltage control circuit is also electrically connected to the first input end of the error amplifier bandwidth control circuit. , and the output terminal of the error amplifier bandwidth control circuit is electrically connected to the input terminal of the power output stage, and the voltage divider circuit is respectively connected to the output terminal of the power supply output stage and the second terminal of the error amplifier bandwidth control circuit in a feedback mode. The input terminal and the output terminal of the power output stage are also electrically connected to the second power supply voltage input terminal of the dynamic power supply voltage switching switch for generating a dynamic power supply voltage greater than the fixed power supply voltage.

In an embodiment of the present invention, the preamplifier is a fully differential amplifier.

In an embodiment of the present invention, the bass enhancement control circuit is provided with a second feedback resistor connected in series with the active capacitance multiplication circuit, and the resistance value of the second feedback resistor is smaller than that of the first feedback resistor resistance.

In one embodiment of the present invention, the power amplifying device further includes a driving output stage, the driving output stage is arranged between the preamplifying stage and the power amplifying stage, and the driving output stage is connected to the preamplifying stage and the power amplifying stage respectively. amplifier stage connected.

In one embodiment of the present invention, a dead time control circuit and a voltage level shift circuit electrically connected with the dead time control circuit are arranged in the driving output stage, the dead time control circuit and the voltage level shift circuit The bit circuit is electrically connected with the preamplifier in the preamplifier stage and the audio power output stage in the power amplifying stage respectively.

Through the above-mentioned structure, the utility model can realize the subwoofer enhancement effect and reduce the circuit size while maintaining the output margin and dynamic range, thereby greatly improving the practicability and reliability of the product.

Description of drawings

FIG. 1 is a schematic block diagram of an existing class-D amplifier architecture;

Fig. 2 is a schematic block diagram of the structure of the utility model;

Fig. 3 is a schematic diagram of a more specific embodiment of the preamplifier stage in the utility model;

Fig. 4 is a schematic diagram of the action of the utility model.

Explanation of reference signs: 11-comparison circuit; 111-audio signal; 112-triangular wave signal; 12-drive and output stage; 13-low-pass filter; 2-speaker; 3-preamp stage; 31-preamplifier ; 32-Bass enhancement control circuit; 321-Active capacitance multiplication circuit; 4-Power amplification stage; 41-Audio power output stage; 42-Dynamic power supply voltage switching switch; 421-First power supply voltage output terminal; 422-Second 423-power supply voltage output terminal; 5-drive output stage; 51-dead time control circuit; 52-voltage level shift circuit; 6-power supply circuit; 61-amplitude and phase detection circuit; 62 -drive circuit; 63-power output stage of power supply; 631-input terminal; 632-output terminal; 64-reference voltage control circuit; 65-error amplifier bandwidth control circuit; 651-first input terminal; 652-second input terminal; 653-output terminal; 66-voltage divider circuit; 7-speaker; R _{f1 -first} feedback resistor; R _{f2 -second} feedback resistor; R _{IN -input} resistor.

detailed description

The following embodiments can be specifically applied to various existing power amplifiers such as class A, class B, class AB, class D, etc., which are not limited by the present invention.

As shown in Figure 2, the utility model provides a power amplification device, which includes:

A preamplifier stage 3, which is provided with a preamplifier 31 and a bass reinforcement control circuit 32 connected with the preamplifier 31 in a feedback mode, as shown in Figure 3, which discloses the A more specific embodiment of the preamplifier stage 3, especially the bass reinforcement control circuit 32 therein, in this embodiment, the preamplifier 31 preferably adopts a fully differential amplifier (fully differential amplifier) with dual output terminals ), this kind of amplifier has better anti-noise performance, and is suitable for applications that have higher requirements for sound quality, and because a fully differential amplifier is used here, so the number of the bass enhancement control circuit 32 is 2, More specifically, the bass enhancement control circuit 32 is provided with a first feedback resistor R _f1 and an active capacitance multiplication circuit 321 connected in parallel with the first feedback resistor R _f1 , this configuration can produce a low-pass filter-like As a result, as long as the ratio between the first feedback resistor R _f1 and the input resistor R _IN of the preamplifier 31 is properly set, the preamplifier 31 can have a larger gain for low-frequency audio signals, thereby To achieve the purpose of bass boost, in addition, the bass boost control circuit 32 may further be provided with a second feedback resistor R _f2 connected in series with the active capacitance multiplication circuit 321, and the second feedback resistor R The resistance value of _f2 is smaller than the first feedback resistance R _f1 , so that the same bass reinforcement effect can be achieved. In addition, in other feasible embodiments, the preamplifier 31 can also use other types of amplifiers, such as single-ended output (single ended output) differential amplifier, now only need to use a bass enhancement control circuit 32;

It should be noted that when the feedback capacitor is selected for the preamplifier 31, in order to make the preamplifier 31 have better low-frequency response characteristics, in order to realize the real subwoofer reinforcement effect (audio signal that can be received by the human ear The frequency range is about 20-20kHz, generally the audio signal in the range of 50-250Hz can be regarded as a subwoofer), usually a large enough capacitor must be used, such as a capacitor of nF level, but such a large capacitor is difficult It is integrated with the preamplifier 31 in a single IC chip, which can only be set in the form of discrete components, thus greatly increasing the size of the circuit board and unable to meet the miniaturization requirements of portable audio products. In this regard, the utility model The active capacitance multiplier circuit 321 is used as the feedback capacitor of the preamplifier 31, and the active capacitance multiplier circuit 321 is actually an active capacitance multiplier (active capacitance multiplier) containing active components (such as amplifiers or transistors). ), which configures a smaller capacitor in the circuit, and adjusts and controls the ratio of different resistors in the circuit at the same time, so that the entire circuit can be equivalent to a larger capacitor. The specific circuit structure of the active capacitance multiplier circuit 321 is now There is technology, so it will not be described in detail here. In this way, the utility model only needs to adopt the capacitance whose actual value only reaches the pF level in the active capacitance multiplication circuit 321, and the effect of the nF level capacitance can be equivalent, thereby The utility model can integrate the active capacitance multiplication circuit 321 and the preamplifier 31 into the same IC chip, so as to greatly reduce the volume of the circuit, and then the utility model can simultaneously achieve the effects of bass reinforcement and circuit size reduction ;

A power amplifier stage 4, an audio power output stage 41 is arranged in the power amplifier stage 4, and the audio power output stage 41 is electrically connected with the preamplifier stage 3, and is used for amplifying and outputting the audio signal through the preamplifier stage 3 Perform power amplification, so that the power amplification stage 4 can transmit the amplified audio signal to a loudspeaker 7 for audio output, just like the general power output stage, the audio power output stage 41 is usually provided with a power crystal as The energy transfer element (passelement), and the remaining specific structures in the audio power output stage 41 are well known to those skilled in the art, and will not be repeated here. In addition, a dynamic power supply voltage can also be provided in the power amplifier stage 4 Switch 42, the dynamic supply voltage switch 42 has a first supply voltage input terminal 421, a second supply voltage input terminal 422 and a supply voltage output terminal 423, wherein the first supply voltage input terminal 421 is connected to a relatively A small fixed power supply voltage, such as Vdd, the power supply voltage output terminal 423 is connected to the audio power output stage 41 to transmit the power supply voltage required by the audio power output stage 41;

The aforementioned arrangement of directly connecting the power amplifier stage 4 behind the preamplifier stage 3 can be applied to linear power amplifiers such as class A, class B, and class AB. However, the utility model can further include a drive output stage 5, which drives The output stage 5 is arranged between the preamplifier stage 3 and the power amplifier stage 4, and the drive output stage 5 is connected with the preamplifier stage 3 and the power amplifier stage 4 respectively, and a dead time control is provided in the drive output stage 5 (dead time control) circuit 51 and a voltage level shift (level shift) circuit 52 electrically connected with the dead time control circuit 51, the dead time control circuit 51 and the voltage level shift circuit 52 are respectively connected with the front The preamplifier 31 in the amplification stage 3 and the audio power output stage 41 in the power amplification stage 4 are electrically connected, and the power supply voltage output terminal 423 in the dynamic power supply voltage switching switch 42 is also connected to the voltage level shift circuit 52 connected to transmit the power supply voltage required by the voltage level shift circuit 52, wherein the dead time control circuit 51 is used to avoid high side (high side) and low side (low side) in the audio power output stage 41 ) power crystals are turned on at the same time to cause a short circuit of the power supply, so that the voltage level shift circuit 52 is used to increase the voltage level of the audio signal to smoothly drive the high-side power crystals, thereby, the utility model can also be applied to Further, if a control circuit for switching the enabled (enabled) state of the drive output stage 5 is further configured for a switching-type power amplifier such as a class D amplifier, the utility model can be further applied to a mixed linear power amplifier. In the power amplifier circuit architecture of the amplifier and the switching power amplifier, the application range and versatility of the present utility model can be greatly improved;

A power supply circuit 6, the power supply circuit 6 is specifically a kind of adaptive boost power converter (adaptive boost power converter), for when the preamplifier stage 3 enhances the bass audio signal, the power amplifier stage 4 Provide a dynamic power supply voltage greater than the fixed power supply voltage, so that the power supply voltage of the power amplifier stage 4 can maintain a certain margin (headroom), so as to maintain a sufficient output dynamic range. In this embodiment, the power supply circuit 6 An amplitude and phase detection circuit 61, a drive circuit 62 and a power output stage 63 are provided inside, wherein the drive circuit 62 includes a reference voltage control circuit 64, an error amplifier bandwidth control circuit 65 and a voltage divider circuit 66. The error amplifier The bandwidth control circuit 65 is generally composed of an error amplifier (ErrorAmplifier) and a necessary feedback compensation circuit. The feedback compensation circuit is generally composed of components such as capacitors and resistors to regulate the bandwidth (Bandwidth) and transient response (transient) of the error amplifier. response) and stability, so that the error amplifier can achieve a better balance between the response speed of the load change and the stability of the system, the error amplifier bandwidth control circuit 65 has a first input terminal 651, a second input terminal 652 and output terminal 653, the amplitude and phase detection circuit 61 are electrically connected to the second input terminal 652 of the bass enhancement control circuit 32 in the preamplifier stage 3, the reference voltage control circuit 64 and the error amplifier bandwidth control circuit 65 respectively connected, the reference voltage control circuit 64 is also electrically connected to the first input terminal 651 of the error amplifier bandwidth control circuit 65, and the output terminal 653 of the error amplifier bandwidth control circuit 65 is electrically connected to the input terminal 631 of the power output stage 63 connected, the voltage divider circuit 66 is respectively connected to the output end 632 of the power output stage 63 and the second input end 652 of the error amplifier bandwidth control circuit 65 in a feedback mode, and the output end 632 of the power output stage 63 is also connected to the second input end 652 of the error amplifier bandwidth control circuit 65. The second power supply voltage input terminal 422 of the dynamic power supply voltage switching switch 42 is electrically connected;

Wherein, the amplitude and phase detection circuit 61 is used to detect the amplitude (amplitude) and phase (phase) of the audio signal amplified by the preamplifier stage 3, and transmit the detected amplitude signal and phase signal to the The reference voltage control circuit 64 and the error amplifier bandwidth control circuit 65, the reference voltage control circuit 64 can generate a corresponding reference voltage (Reference Voltage, V _REF ) signal according to the amplitude signal, and then transmit the reference voltage signal to the error amplifier The first input terminal 651 of the amplifier bandwidth control circuit 65, the feedback compensation circuit inside the error amplifier bandwidth control circuit 65 can generate and determine the bandwidth and instantaneous response characteristics of the error amplifier according to the phase signal, the error amplifier bandwidth control circuit The output terminal 653 of 65 will generate a corresponding pulse width control signal according to the signal at the input terminal and send it to the power supply output stage 63, so that the dynamic power supply voltage can be generated at the output terminal 632 of the power supply output stage 63 and sent to the dynamic power supply Voltage switch 42;

The working principle and beneficial effects of the present utility model are explained below: as shown in Figure 3 and Figure 4, when the audio signal belonged to the midrange or treble range, the gain produced by the preamplifier stage 3 was small, so in the power amplifier stage 4 The audio power output stage 41 does not need a large power supply voltage, so the dynamic power supply voltage switching switch 42 will switch its switching state at this time, and the audio power output stage 41 is connected to the voltage by using the fixed power supply voltage connected to the first power supply voltage input terminal 421 Level shifting circuit 52 supplies power; When the audio signal belongs to the bass or subwoofer range, the bass reinforcement control circuit 32 can make the preamplifier stage 3 produce a larger gain. At this time, the amplitude and phase in the power supply circuit 6 The detection circuit 61 will detect a larger amplitude signal, so that the reference voltage control circuit 64 can generate a larger reference voltage signal, thereby dynamically making the power supply output stage 63 generate a dynamic power supply larger than the fixed power supply voltage At this time, the dynamic power supply voltage switching switch 42 can switch its switching state again, so that the dynamic power supply voltage connected to the second power supply voltage input terminal 422 supplies power to the audio power output stage 41 and the voltage level shifting circuit 52, so As a result, when the pre-amplification stage 3 strengthens the audio signal of the bass to increase its level, the power supply circuit 6 can synchronously and dynamically boost the power supply voltage of the audio power output stage 41 to a higher level, thereby making the At this time, the power level can keep the audio signal level higher than that of the bass, avoiding the saturation distortion caused by the clipping of the audio output signal, so as to realize the dynamic power control function, so that the utility model can greatly improve the product performance and reliability effect.

Claims (5)

1. A power amplifier, characterized in that it comprises: A preamplifier stage, which is provided with a preamplifier and a bass enhancement control circuit connected with the preamplifier in a feedback mode, and the bass enhancement control circuit is provided with a first feedback resistor and a an active capacitance multiplication circuit connected in parallel with the first feedback resistor; A power amplification stage, the power amplification stage is provided with an audio power output stage and a dynamic power supply voltage switching switch, the audio power output stage is electrically connected to the preamplifier stage, and the dynamic power supply voltage switching switch has a first power supply voltage input terminal, a second power supply voltage input terminal and a power supply voltage output terminal, the first power supply voltage input terminal is connected to a smaller fixed power supply voltage, and the power supply voltage output terminal is connected to the audio power output stage; A power supply circuit, the power supply circuit is provided with an amplitude and phase detection circuit, a drive circuit and a power output stage, the drive circuit includes a reference voltage control circuit, an error amplifier bandwidth control circuit and a voltage divider circuit, the error amplifier The bandwidth control circuit has a first input terminal, a second input terminal and an output terminal, and the amplitude and phase detection circuit are respectively electrically connected to the second input terminal of the preamplifier stage, the reference voltage control circuit and the error amplifier bandwidth control circuit, The reference voltage control circuit is also electrically connected to the first input terminal of the error amplifier bandwidth control circuit, and the output terminal of the error amplifier bandwidth control circuit is electrically connected to the input terminal of the power output stage of the power supply. The output end of the power output stage of the power supply is connected with the second input end of the error amplifier bandwidth control circuit respectively, and the output end of the power output stage of the power supply is also electrically connected with the second power supply voltage input end of the dynamic power supply voltage switching switch, Used to generate a dynamic power supply voltage greater than the fixed power supply voltage. 2. The power amplifying device according to claim 1, wherein the preamplifier is a fully differential amplifier. 3. The power amplifying device according to claim 1, wherein the bass enhancement control circuit is provided with a second feedback resistor connected in series with the active capacitance multiplication circuit, and the resistance value of the second feedback resistor is less than the resistance value of the first feedback resistor. 4. The power amplifying device according to any one of claims 1 to 3, further comprising a drive output stage, the drive output stage is arranged between the preamplifier stage and the power amplifier stage, and the drive output stage The output stage is respectively connected with the pre-amplification stage and the power amplification stage. 5. The power amplifying device according to claim 4, wherein a dead time control circuit and a voltage level shift circuit electrically connected to the dead time control circuit are arranged in the driving output stage, and the dead time The control circuit and the voltage level shifting circuit are electrically connected with the preamplifier in the preamplifier stage and the audio power output stage in the power amplifier stage respectively.