Amplitude limiting circuit for input signal of power amplifier

Abstract

The utility model discloses a power amplifier input signal amplitude limiting circuit, which comprises an input attenuation control circuit, an input buffer circuit, a rectifying circuit, a filtering current limiting circuit and an optocoupler feedback circuit, the output end of the input attenuation control circuit is connected with the input end of the input buffer circuit and the first input end of the optocoupler feedback circuit, the output end of the input buffer circuit is connected with the input end of the rectifying circuit and further connected with an external power amplifier, and the output end of the rectifying circuit is connected with the input end of the filtering current limiting circuit. The output end of the filtering current limiting circuit is connected with the second input end of the optocoupler feedback circuit. According to the utility model, the input signal can be limited within a certain range, so that the amplitude of the signal input to the power amplifier is maintained within an allowable range, the stability and safety of the external power amplifier are improved, and the effect of limiting the signal amplitude of the input signal is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of power amplifier circuits, in particular to a power amplifier input signal amplitude limiting circuit. Background Art

[0002] At present, the power amplifier has a certain range requirement for the signal amplitude (voltage value) of the input signal source (general audio source), that is, only the signal source within a certain voltage range is allowed to be input. When the signal amplitude of the input signal source exceeds the allowed signal amplitude, the power amplifier will have problems such as clipping distortion on the signal source, which will lead to overcurrent problems of the power amplifier. What's worse, the power amplifier outputs too large a signal amplitude and cannot match the maximum working range of the subsequent speaker, which will cause the power amplifier to be damaged and the speaker to burn, causing property losses to users and bringing certain safety hazards. For this reason, it is necessary to limit the signal amplitude (i.e., amplitude) of the input signal (i.e., signal source) of the power amplifier after it is input to the power amplifier to keep the signal amplitude of the input signal within the allowed range, thereby protecting the power amplifier and the subsequent speakers, speakers and other playback devices connected to the power amplifier, so as to maintain the signal amplitude document of the power amplifier output, thereby protecting the power amplifier and the subsequent playback devices from being damaged by the excessive input signal amplitude. Utility Model Content

[0003] In view of the deficiencies in the prior art, the purpose of the utility model is to provide a power amplifier input signal amplitude limiting circuit, which can solve the problems described in the background technology.

[0004] The technical solution for achieving the purpose of the utility model is: a power amplifier input signal amplitude limiting circuit, including an input attenuation control circuit, an input buffer circuit, a rectifier circuit, a filter current limiting circuit and an optocoupler feedback circuit, the input end of the input attenuation control circuit is used to connect to an external signal source, the output end of the input attenuation control circuit is respectively connected to the input end of the input buffer circuit and the first input end of the optocoupler feedback circuit, the output end of the input buffer circuit is connected to the input end of the rectifier circuit, and is also connected to an external power amplifier, the output end of the rectifier circuit is connected to the input end of the filter current limiting circuit, and the output end of the filter current limiting circuit is connected to the second input end of the optocoupler feedback circuit.

[0005] Furthermore, the input attenuation control circuit includes a capacitor C1 and a resistor R1 connected in series, one end of the capacitor C1 serves as an output end of the input attenuation control circuit, and one end of the resistor R1 serves as an output end of the input attenuation control circuit.

[0006] Furthermore, the buffer circuit includes a voltage follower U1, the positive input end of the voltage follower U1 is connected to one end of the resistor R1, the reverse input end of the voltage follower is connected to the output end of the voltage follower, and the output end of the voltage follower is respectively connected to the input end of the power amplifier and the rectifier circuit.

[0007] Furthermore, the rectifier circuit includes an inverting amplifier U2, a resistor R4, a resistor R5, a diode D1 and a diode D2, one end of the resistor R4 is connected to the output end of the voltage follower U1 of the buffer circuit, the other end of the resistor R4 is respectively connected to the inverting input end of the inverting amplifier U2, the positive electrode of the diode D1, and one end of the resistor R5, the forward input end of the inverting amplifier U2 is grounded, the negative electrode of the diode D1 is connected to the output end of the inverting amplifier U2 and then to the positive electrode of the diode D2, and the other end of the resistor R5 is connected to the negative electrode of the diode D2 and serves as the output end of the rectifier circuit.

[0008] Furthermore, the filtering current limiting circuit includes a resistor R6, a resistor R7, a polarity capacitor EC1 and a voltage regulator ZD1. The resistor R6 and the polarity capacitor EC1 are connected in parallel to form a first parallel branch. One end of the resistor R6 is connected to the negative electrode of the polarity capacitor EC1 to form a first end of the first parallel branch. The first end of the first parallel branch is grounded. The other end of the resistor R6 is connected to the positive electrode of the polarity capacitor EC1 to form a second end of the first parallel branch. The second end of the first parallel branch serves as an input end of the filtering current limiting circuit. The second end of the first parallel branch is respectively connected to one end of the resistor R7 and the output end of the rectifier circuit. The other end of the resistor R7 serves as an output end of the filtering current limiting circuit. The other end of the resistor R7 is connected in series with the voltage regulator ZD1 and then grounded. The other end of the resistor R7 is also connected to the optocoupler feedback circuit as an output end.

[0009] Furthermore, the optocoupler feedback circuit includes a capacitor C2, a resistor R2 and an optocoupler U3. The capacitor C2 and the resistor R2 are connected in parallel to form a second parallel branch. One end of the second parallel branch is connected to the second pin of the optocoupler U3 and then grounded. The other end of the second parallel branch serves as the output end of the optocoupler feedback circuit and is connected to the resistor R1 as one end of the output end of the input attenuation control circuit. The other end of the second parallel branch is also connected to the third pin of the optocoupler U3. The second pin and the third pin are the two ends of the internal resistor of the optocoupler U3. The first pin of the optocoupler U3 is grounded. The fourth pin of the optocoupler U3 is connected to the other end of the resistor R7. The first pin and the fourth pin of the optocoupler U3 are the two ends of the light-emitting diode inside the optocoupler U3. The fourth pin is the positive electrode of the light-emitting diode, and the first pin is the negative electrode of the light-emitting diode.

[0010] The beneficial effects of the utility model are as follows: the utility model can limit the input signal within a certain range, so as to maintain the signal amplitude input to the power amplifier within the allowable range, improve the stability and safety of the external power amplifier, and play a role in limiting the signal amplitude of the input signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a circuit diagram of the utility model;

[0012] Figure 2 is a circuit diagram of an input attenuation control circuit;

[0013] Figure 3 is a circuit diagram of an input buffer circuit;

[0014] Figure 4 is a circuit diagram of a rectifier circuit;

[0015] Figure 5 is a circuit diagram of a filter current limiting circuit;

[0016] Figure 6 This is the circuit diagram of the optocoupler feedback circuit. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and specific implementation plans:

[0018] like Figure 1-Figure 6 As shown, a power amplifier input signal amplitude limiting circuit includes an input attenuation control circuit, an input buffer circuit, a rectifier circuit, a filter current limiting circuit and an optocoupler feedback circuit. The input end of the input attenuation control circuit is used to connect to an external signal source, such as a sound source. The output end of the input attenuation control circuit is respectively connected to the input end of the input buffer circuit and the first input end of the optocoupler feedback circuit. The output end of the input buffer circuit is connected to the input end of the rectifier circuit and is also connected to an external power amplifier. The power amplifier is connected to a speaker. The output end of the rectifier circuit is connected to the input end of the filter current limiting circuit. The output end of the filter current limiting circuit is connected to the second input end of the optocoupler feedback circuit.

[0019] The input attenuation control circuit is used to attenuate the signal amplitude of the input signal source so that the signal amplitude of the input signal source is within the allowable range after attenuation.

[0020] The buffer circuit is a buffer circuit based on a voltage follower, which is used to buffer the output voltage of the attenuation control circuit to the buffer circuit and then output it, and to isolate and impedance match the input attenuation control circuit from the rectifier circuit and the power amplifier.

[0021] The rectifier circuit is used to convert the alternating current output by the buffer circuit into direct current. The rectifier circuit also includes a filter capacitor, which is used to remove the pulsating voltage in the rectified direct current point to make the rectified direct current voltage more stable.

[0022] The filter current limiting circuit is used to filter and limit the DC power output by the rectifier circuit, so as to remove the residual AC component in the DC power and achieve a protective effect by current limiting.

[0023] The optocoupler feedback circuit is used to establish an inversely proportional relationship between the signal amplitude of the input signal of the input attenuation control circuit and the signal amplitude input to the input buffer circuit after output, that is, the larger the signal amplitude of the input signal, the smaller the signal amplitude of the output signal, and conversely, the smaller the signal amplitude of the input signal, the larger the signal amplitude of the output signal.

[0024] The input attenuation control circuit includes a capacitor C1 and a resistor R1 connected in series. One end of the capacitor C1 serves as the output end of the input attenuation control circuit, thereby being connected to an external signal source. One end of the resistor R1 serves as the output end of the input attenuation control circuit, thereby being connected to the input end of the input buffer circuit and the first input end of the optocoupler feedback circuit.

[0025] In the input attenuation control circuit, capacitor C1 and resistor R1 attenuate the signal input from the external signal source and filter out the high-frequency components, and attenuate the high voltage of the input signal to a low voltage, thereby protecting the subsequent circuit.

[0026] The buffer circuit includes a voltage follower U1, wherein the positive input terminal of the voltage follower U1 is connected to one end of the resistor R1, the reverse input terminal of the voltage follower is connected to the output terminal of the voltage follower, and the output terminal of the voltage follower is respectively connected to the input terminal of the power amplifier and the rectifier circuit. The two power supply terminals of the voltage follower are respectively connected to a +12V voltage and a -12V voltage.

[0027] The rectifier circuit includes an inverting amplifier U2, a resistor R4, a resistor R5, a diode D1 and a diode D2. One end of the resistor R4 is connected to the output end of the voltage follower U1 of the buffer circuit, thereby realizing the connection between the rectifier circuit and the buffer circuit. The other end of the resistor R4 is respectively connected to the inverting input end of the inverting amplifier U2, the positive electrode of the diode D1, and one end of the resistor R5. The positive input end of the inverting amplifier U2 is grounded. The negative electrode of the diode D1 is connected to the output end of the inverting amplifier U2 and then to the positive electrode of the diode D2. The other end of the resistor R5 is connected to the negative electrode of the diode D2 and then serves as the output end of the rectifier circuit.

[0028] The rectification effect of the rectifier circuit utilizes the unidirectional conductivity of the diode. When the alternating current passes through the rectifier circuit, the positive half-cycle of the alternating current can pass through the diode D1, while the negative half-cycle is cut off and cannot pass through the diode D1. The alternating current in the negative half-cycle will pass through the negative electrode of the reverse operational amplifier U2 and be output in reverse, thereby converting the negative half-cycle into a positive half-cycle and then output to the next stage through the diode D2.

[0029] The filtering and current limiting circuit includes a resistor R6, a resistor R7, a polarity capacitor EC1 and a voltage regulator ZD1. The resistor R6 and the polarity capacitor EC1 are connected in parallel to form a first parallel branch. One end of the resistor R6 is connected to the negative electrode of the polarity capacitor EC1 to form a first end of the first parallel branch. The first end of the first parallel branch is grounded. The other end of the resistor R6 is connected to the positive electrode of the polarity capacitor EC1 to form a second end of the first parallel branch. The second end of the first parallel branch serves as an input end of the filtering and current limiting circuit. The second end of the first parallel branch is respectively connected to one end of the resistor R7 and the output end of the rectifier circuit. The other end of the resistor R7 serves as an output end of the filtering and current limiting circuit. The other end of the resistor R7 is connected in series with the voltage regulator ZD1 and then grounded. The other end of the resistor R7 is also connected to the optocoupler feedback circuit as an output end.

[0030] In the filtering and current limiting circuit, the resistor R6 is grounded to pull down the voltage, thereby discharging the capacitor EC1. The resistor R7 plays a current limiting role and protects the circuit. The capacitor EC1 is grounded to filter the rectifier circuit of the previous stage to remove the residual AC component. The reverse grounding of the voltage regulator ZD1 also plays a current limiting role, thereby protecting the light-emitting diode inside the optocoupler U3 in the subsequent optocoupler feedback circuit to prevent burning.

[0031] The optocoupler feedback circuit includes a capacitor C2, a resistor R2 and an optocoupler U3. The capacitor C2 and the resistor R2 are connected in parallel to form a second parallel branch. One end of the second parallel branch is connected to the second pin of the optocoupler U3 and then grounded together. The other end of the second parallel branch serves as the output end of the optocoupler feedback circuit and is connected to the resistor R1 as one end of the output end of the input attenuation control circuit, thereby realizing the connection between the input attenuation control circuit and the optocoupler feedback circuit. The other end of the second parallel branch is also connected to the third pin of the optocoupler U3. The second pin and the third pin are the two ends of the internal resistance (i.e., the on-resistance) of the optocoupler U3. The first pin of the optocoupler U3 is grounded. The fourth pin of the optocoupler U3 is connected to the other end of the resistor R7, thereby realizing the connection between the optocoupler feedback circuit and the filtering current limiting circuit. The first pin and the fourth pin of the optocoupler U3 are the two ends of the light-emitting diode inside the optocoupler U3. The fourth pin is the positive electrode of the light-emitting diode, and the first pin is the negative electrode of the light-emitting diode.

[0032] Based on the characteristics of the optocoupler U3, when the light-emitting diode of the optocoupler U3 receives the signal input by the input attenuation control circuit (defined as the pre-stage signal), it is lit. When the current stage signal is larger (the larger the signal amplitude), the light-emitting diode is brighter, so that the resistance value of the on-resistance of the optocoupler U3 is smaller, and through the voltage division with the input resistance, the signal amplitude value input to the buffer circuit by the input attenuation control circuit is smaller, thereby reducing the signal amplitude input to the external power amplifier by the input attenuation control circuit through the buffer circuit. On the contrary, when the current stage signal is smaller, the light-emitting diode is darker, the resistance value of the on-resistance is larger, and through the voltage division with the input resistance, the signal amplitude value input to the buffer circuit by the input attenuation control circuit is larger, thereby increasing the signal amplitude input to the external power amplifier by the input attenuation control circuit through the buffer circuit. Thus, the stability of the input signal of the power amplifier is maintained within a certain signal amplitude range. The second parallel branch composed of the resistor R2 and the capacitor C2 in parallel is connected in parallel at the on-resistance inside the optocoupler U3 to filter high-frequency signals and prevent the operational amplifier from being suspended.

[0033] Among them, the resistance values ​​of resistor R1, resistor R2, resistor R4, resistor R4, resistor R4, and resistor R47 are 10KΩ (ohm), 10KΩ, 10KΩ, 68KΩ, 4.7KΩ, and 10KΩ respectively.

[0034] The utility model can limit the input signal within a certain range, so that the signal amplitude input to the power amplifier is maintained within the allowable range, improves the stability and safety of the external power amplifier, and plays a role in limiting the signal amplitude of the input signal.

[0035] The embodiment disclosed in this specification is only an example of the unilateral features of the utility model, and the protection scope of the utility model is not limited to this embodiment. Any other functionally equivalent embodiments fall within the protection scope of the utility model. For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all these changes and deformations should fall within the protection scope of the claims of the utility model.

Claims

1. A power amplifier input signal amplitude limiting circuit, characterized in that: It includes an input attenuation control circuit, an input buffer circuit, a rectifier circuit, a filter current limiting circuit and an optocoupler feedback circuit. The input end of the input attenuation control circuit is used to connect to an external signal source, the output end of the input attenuation control circuit is respectively connected to the input end of the input buffer circuit and the first input end of the optocoupler feedback circuit, the output end of the input buffer circuit is connected to the input end of the rectifier circuit, and is also connected to an external power amplifier, the output end of the rectifier circuit is connected to the input end of the filter current limiting circuit, and the output end of the filter current limiting circuit is connected to the second input end of the optocoupler feedback circuit.

2. The power amplifier input signal amplitude limiting circuit according to claim 1, characterized in that: The input attenuation control circuit comprises a capacitor C1 and a resistor R1 connected in series, one end of the capacitor C1 serves as an output end of the input attenuation control circuit, and one end of the resistor R1 serves as an output end of the input attenuation control circuit.

3. The power amplifier input signal amplitude limiting circuit according to claim 2, characterized in that: The buffer circuit includes a voltage follower U1, a positive input terminal of the voltage follower U1 is connected to one end of the resistor R1, a negative input terminal of the voltage follower is connected to an output terminal of the voltage follower, and an output terminal of the voltage follower is respectively connected to an input terminal of a power amplifier and a rectifier circuit.

4. The power amplifier input signal amplitude limiting circuit according to claim 3, characterized in that: The rectifier circuit includes an inverting amplifier U2, a resistor R4, a resistor R5, a diode D1 and a diode D2. One end of the resistor R4 is connected to the output end of the voltage follower U1 of the buffer circuit, and the other end of the resistor R4 is respectively connected to the inverting input end of the inverting amplifier U2, the positive electrode of the diode D1, and one end of the resistor R5. The positive input end of the inverting amplifier U2 is grounded, the negative electrode of the diode D1 is connected to the output end of the inverting amplifier U2 and then to the positive electrode of the diode D2. The other end of the resistor R5 is connected to the negative electrode of the diode D2 and serves as the output end of the rectifier circuit.

5. The power amplifier input signal amplitude limiting circuit according to claim 4, characterized in that: The filtering and current limiting circuit includes a resistor R6, a resistor R7, a polarity capacitor EC1 and a voltage regulator ZD1. The resistor R6 and the polarity capacitor EC1 are connected in parallel to form a first parallel branch. One end of the resistor R6 is connected to the negative electrode of the polarity capacitor EC1 to form a first end of the first parallel branch. The first end of the first parallel branch is grounded. The other end of the resistor R6 is connected to the positive electrode of the polarity capacitor EC1 to form a second end of the first parallel branch. The second end of the first parallel branch serves as an input end of the filtering and current limiting circuit. The second end of the first parallel branch is respectively connected to one end of the resistor R7 and the output end of the rectifier circuit. The other end of the resistor R7 serves as an output end of the filtering and current limiting circuit. The other end of the resistor R7 is connected in series with the voltage regulator ZD1 and then grounded. The other end of the resistor R7 is also connected to the optocoupler feedback circuit as an output end.

6. The power amplifier input signal amplitude limiting circuit according to claim 5, characterized in that: The optocoupler feedback circuit includes a capacitor C2, a resistor R2 and an optocoupler U3. The capacitor C2 and the resistor R2 are connected in parallel to form a second parallel branch. One end of the second parallel branch is connected to the second pin of the optocoupler U3 and then grounded together. The other end of the second parallel branch serves as the output end of the optocoupler feedback circuit and is connected to the resistor R1 as one end of the output end of the input attenuation control circuit. The other end of the second parallel branch is also connected to the third pin of the optocoupler U3. The second pin and the third pin are the two ends of the internal resistor of the optocoupler U3. The first pin of the optocoupler U3 is grounded. The fourth pin of the optocoupler U3 is connected to the other end of the resistor R7. The first pin and the fourth pin of the optocoupler U3 are the two ends of the light-emitting diode inside the optocoupler U3. The fourth pin is the positive electrode of the light-emitting diode, and the first pin is the negative electrode of the light-emitting diode.

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