Power amplifier protection circuit and electronic equipment

Abstract

The utility model discloses a power amplifier protection circuit and electronic equipment, and the power amplifier protection circuit comprises an audio input end, an audio output end, a power amplifier circuit, a first resistor, a second resistor, a third resistor, a current sampling circuit, and a threshold comparison circuit. The first resistor is connected between the negative input end of the power amplifier circuit and the grounding end of the power amplifier protection circuit, the second resistor is connected between the output end of the power amplifier circuit and the audio output end, and the third resistor is connected between the negative input end of the power amplifier circuit and the output end of the power amplifier circuit; the first end of the current sampling circuit is connected with the first end of the second resistor, the second end of the current sampling circuit is connected with the second end of the second resistor, the third end of the current sampling circuit is connected with the first end of the threshold comparison circuit, and the second end of the threshold comparison circuit is connected with the negative input end of the power amplifier circuit.

Description

Technical Field

[0001] The utility model relates to the technical field of circuit design, and more specifically, to a power amplifier protection circuit and an electronic device. Background Art

[0002] Class D amplifier refers to Class D audio power amplifier (sometimes also called digital amplifier). An amplifier that drives a speaker by controlling the ON / OFF of a switch unit is called a Class D amplifier.

[0003] If the power amplifier is connected to a low-impedance speaker or the output circuit is short-circuited, the output current of the amplifier will be too large, which may burn out electronic components such as MOS tubes inside the power amplifier, causing the electronic equipment to fail to play audio normally. Utility Model Content

[0004] One purpose of the utility model is to provide a power amplifier protection circuit and an electronic device.

[0005] According to one aspect of the utility model, a power amplifier protection circuit is provided, comprising an audio input terminal, an audio output terminal, a power amplifier circuit, a first resistor, a second resistor, a third resistor, a current sampling circuit, and a threshold comparison circuit.

[0006] The positive input terminal of the power amplifier circuit is connected to the audio input terminal, the first resistor is connected between the negative input terminal of the power amplifier circuit and the ground terminal of the power amplifier protection circuit, the second resistor is connected between the output terminal of the power amplifier circuit and the audio output terminal, and the third resistor is connected between the negative input terminal of the power amplifier circuit and the output terminal of the power amplifier circuit;

[0007] The first end of the current sampling circuit is connected to the first end of the second resistor, the second end of the current sampling circuit is connected to the second end of the second resistor, the third end of the current sampling circuit is connected to the first end of the threshold comparison circuit, and the second end of the threshold comparison circuit is connected to the negative input end of the power amplifier circuit.

[0008] Optionally, the power amplifier protection circuit further includes a gain adjustment circuit, a first end of the gain adjustment circuit is connected to a third end of the current sampling circuit, and a second end of the gain adjustment circuit is connected to a first end of the threshold comparison circuit.

[0009] Optionally, the current sampling circuit includes a first operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor.

[0010] A first end of the second resistor is connected to the output end of the power amplifier circuit, and a second end of the second resistor is connected to the audio output end;

[0011] The fourth resistor is connected between the inverting input terminal of the first operational amplifier and the first end of the second resistor, the fifth resistor is connected between the non-inverting input terminal of the first operational amplifier and the second end of the second resistor, the sixth resistor is connected between the inverting input terminal of the first operational amplifier and the output terminal of the first operational amplifier, and the seventh resistor is connected between the non-inverting input terminal of the first operational amplifier and the ground terminal.

[0012] Optionally, the gain adjustment circuit includes a second operational amplifier, an eighth resistor, a ninth resistor and a tenth resistor, the eighth resistor is connected between the third terminal of the current sampling circuit and the inverting input terminal of the second operational amplifier, the ninth resistor is connected between the non-inverting input terminal of the second operational amplifier and the ground terminal, the tenth resistor is connected between the inverting input terminal of the second operational amplifier and the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the first terminal of the threshold comparison circuit.

[0013] Optionally, the threshold comparison circuit includes an eleventh resistor, a twelfth resistor, and a first transistor, the eleventh resistor and the twelfth resistor are connected in series between the positive power supply terminal and the ground terminal of the power amplifier protection circuit, the first electrode of the first transistor is connected to a first potential point, the second electrode of the first transistor is connected to the second end of the gain adjustment circuit, and the third electrode of the first transistor is connected to the negative input terminal of the power amplifier circuit; the first potential point is the potential point between the eleventh resistor and the twelfth resistor.

[0014] Optionally, the power amplifier protection circuit further includes a DC detection circuit, a first end of the DC detection circuit is connected to the audio output end, and a second end of the DC detection circuit is connected to a third end of the gain adjustment circuit.

[0015] Optionally, the DC detection circuit includes a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a clamping circuit, and a third transistor, the fifteenth resistor and the sixteenth resistor are connected in series between the audio output terminal and the ground terminal, the clamping circuit is connected between the first electrode of the third transistor and the ground terminal, the first electrode of the third transistor is also connected to a third potential point, the third electrode of the third transistor is connected to the positive power supply terminal of the power amplifier protection circuit, and the seventeenth resistor is connected between the second electrode of the third transistor and the third terminal of the gain adjustment circuit;

[0016] The third potential point is a potential point between the fifteenth resistor and the sixteenth resistor.

[0017] Optionally, the threshold comparison circuit further includes a thirteenth resistor, a fourteenth resistor, and a second transistor, the thirteenth resistor and the fourteenth resistor are connected in series between the negative power supply terminal of the power amplifier protection circuit and the ground terminal, the first electrode of the second transistor is connected to the second potential point, the second electrode of the second transistor is connected to the second end of the gain adjustment circuit, and the third electrode of the second transistor is connected to the negative input terminal of the power amplifier circuit;

[0018] The second potential point is a potential point between the thirteenth resistor and the fourteenth resistor.

[0019] Optionally, the power amplifier protection circuit further includes a nineteenth resistor, and the nineteenth resistor is connected between the second end of the threshold comparison circuit and the negative input end of the power amplifier circuit.

[0020] According to a second aspect of the present invention, an electronic device is provided, comprising a speaker and the power amplifier protection circuit according to the first aspect of the present invention, wherein the audio output terminal is connected to the speaker.

[0021] According to the embodiments of the present disclosure, when the current output by the power amplifier circuit is too large, the power amplifier protection circuit can reduce the current output by the power amplifier circuit, thereby avoiding burning out of electronic devices such as MOS tubes inside the power amplifier circuit.

[0022] Other features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute a part of the specification, illustrate embodiments of the present utility model and, together with the description, are used to explain the principles of the present utility model.

[0024] Figure 1 It is a principle block diagram of a power amplifier protection circuit according to an embodiment of the utility model;

[0025] Figure 2 It is a principle block diagram of a power amplifier protection circuit according to an embodiment of the utility model;

[0026] Figure 3 is a circuit schematic diagram of a power amplifier protection circuit according to an embodiment of the utility model;

[0027] Figure 4 It is a circuit principle diagram of a power amplifier protection circuit according to an embodiment of the utility model. DETAILED DESCRIPTION

[0028] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0029] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present invention, its application, or uses.

[0030] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0031] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0032] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] The present disclosure provides a power amplifier protection circuit. Figure 1 The figure is a principle block diagram of a power amplifier protection circuit according to an embodiment of the utility model.

[0034] according to Figure 1 As shown, the power amplifier protection circuit 1000 may include an audio input terminal Vin, an audio output terminal Vout, a power amplifier circuit 1100 , a first resistor R1 , a second resistor R2 , a third resistor R3 , a current sampling circuit 1200 , and a threshold comparison circuit 1300 .

[0035] The positive input terminal of the power amplifier circuit 1100 is connected to the audio input terminal Vin, the first resistor R1 is connected between the negative input terminal of the power amplifier circuit 1100 and the ground terminal GND of the power amplifier protection circuit 1000, the second resistor R2 is connected between the output terminal of the power amplifier circuit 1100 and the audio output terminal Vout, and the third resistor R3 is connected between the negative input terminal of the power amplifier circuit 1100 and the output terminal of the power amplifier circuit 1100.

[0036] A first end of the current sampling circuit 1200 is connected to a first end of the second resistor R2, a second end of the current sampling circuit 1200 is connected to a second end of the second resistor R2, a third end of the current sampling circuit 1200 is connected to a first end of the threshold comparison circuit 1300, and a second end of the threshold comparison circuit 1300 is connected to a negative input end of the power amplifier circuit 1100.

[0037] The power amplifier circuit 1100 in this embodiment may be any circuit structure capable of realizing a power amplification function, which is not limited here.

[0038] In this embodiment, the current sampling circuit 1200 can be based on the voltage difference across the second resistor R2, and the magnitude of the output voltage can represent the magnitude of the current flowing through the second resistor R2. Specifically, the voltage output by the current sampling circuit 1200 and the current flowing through the second resistor R2 can have a positive linear relationship or a negative linear relationship.

[0039] In one embodiment, there is a positive linear relationship between the voltage output by the current sampling circuit 1200 and the current flowing through the second resistor R2. When the current output by the power amplifier circuit is too large, the voltage output by the current sampling circuit 1200 is also too large. When the voltage output by the current sampling circuit 1200 is greater than or equal to the corresponding threshold comparison voltage, the threshold comparison circuit 1300 outputs a positive feedback voltage to the negative input terminal of the power amplifier circuit 1100; when the voltage output by the current sampling circuit 1200 is less than the corresponding threshold comparison voltage, the threshold comparison circuit 1300 does not output a voltage.

[0040] In another embodiment, there is a negative linear relationship between the voltage output by the current sampling circuit 1200 and the current flowing through the second resistor R2. When the current output by the power amplifier circuit is too large, the voltage output by the current sampling circuit 1200 is too small. When the voltage output by the current sampling circuit 1200 is less than or equal to the corresponding threshold comparison voltage, the threshold comparison circuit 1300 outputs a negative feedback voltage to the negative input terminal of the power amplifier circuit 1100. When the voltage output by the current sampling circuit 1200 is greater than the corresponding threshold comparison voltage, the threshold comparison circuit 1300 does not output a voltage.

[0041] When the threshold comparison circuit 1300 does not output a voltage, the input signal of the power amplifier circuit 1100 is an audio signal input through the audio input terminal Vin. The power amplifier circuit 1100, the first resistor R1 and the third resistor R3 constitute a common-mode amplifier circuit that can amplify the audio signal.

[0042] When the threshold comparison circuit 1300 outputs a positive feedback voltage to the negative input terminal of the power amplifier circuit 1100, the positive feedback voltage is inverted and amplified by the power amplifier circuit 1100, and the voltage at the output terminal of the power amplifier circuit 1100 drops, which can reduce the current output by the output terminal of the power amplifier circuit 1100, thereby avoiding burning out the MOS tube inside the power amplifier circuit 1100.

[0043] According to the embodiments of the present disclosure, when the current output by the power amplifier circuit is too large, the power amplifier protection circuit can reduce the current output by the power amplifier circuit, thereby avoiding burning out of electronic devices such as MOS tubes inside the power amplifier circuit.

[0044] In one embodiment of the present disclosure, Figure 2 As shown, the power amplifier protection circuit 1000 further includes a gain adjustment circuit 1400 , a first end of the gain adjustment circuit 1400 is connected to the third end of the current sampling circuit 1200 , and a second end of the gain adjustment circuit 1400 is connected to the first end of the threshold comparison circuit 1300 .

[0045] In this embodiment, the gain adjustment circuit 1400 can adjust the gain of the voltage output by the current sampling circuit 1200. Specifically, the gain of the gain adjustment circuit 1400 can be a positive number or a negative number.

[0046] In an embodiment where the gain of the gain adjustment circuit 1400 is a negative number, if there is a positive linear relationship between the voltage output by the current sampling circuit 1200 and the current flowing through the second resistor R2, when the current output by the power amplifier circuit is too large, the voltage output by the current sampling circuit 1200 is too large, and the voltage output by the gain adjustment circuit 1400 is too small. When the voltage output by the gain adjustment circuit 1400 is less than or equal to the corresponding threshold comparison voltage, the threshold comparison circuit 1300 outputs a positive feedback voltage to the negative input terminal of the power amplifier circuit 1100; when the voltage output by the gain adjustment circuit 1400 is greater than the corresponding threshold comparison voltage, the threshold comparison circuit 1300 does not output a voltage.

[0047] In one embodiment of the present disclosure, Figure 3 and Figure 4 As shown, the current sampling circuit 1200 may include a first operational amplifier A1, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7.

[0048] In an embodiment in which the first end of the second resistor R2 is connected to the output end of the power amplifier circuit 1100 and the second end of the second resistor R2 is connected to the audio output end Vout, the fourth resistor R4 may be connected between the inverting input end of the first operational amplifier A1 and the first end of the second resistor R2, the fifth resistor R5 may be connected between the non-inverting input end of the first operational amplifier A1 and the second end of the second resistor R2, the sixth resistor R6 may be connected between the inverting input end of the first operational amplifier A1 and the output end of the first operational amplifier A1, and the seventh resistor R7 may be connected between the non-inverting input end of the first operational amplifier A1 and the ground terminal GND.

[0049] In one embodiment, the fourth resistor R4 and the fifth resistor R5 have the same resistance value, and the sixth resistor R6 and the seventh resistor R7 also have the same resistance value.

[0050] When the audio output terminal Vout is not short-circuited with the positive power supply terminal VCC, the direction of the current flowing through the second resistor R2 can be as follows: Figure 3 and Figure 4 The direction indicated by the arrow is the same, and the voltage across the second resistor R2 is V1, wherein V1 is the difference between the voltage at the first end of the second resistor R2 and the voltage at the second end of the second resistor R2. Figure 3 and Figure 4 The current sampling circuit 1200 shown processes the voltage V1 across the second resistor R2. The voltage V2 output by the current sampling circuit 1200 can be expressed by the following formula:

[0051]

[0052] Wherein, R4 is the resistance value of the fourth resistor R4 and the fifth resistor R5, and R6 is the resistance value of the sixth resistor R6 and the seventh resistor R7.

[0053] It is understandable that the current sampling circuit 1200 may also be implemented by other circuit structures, which will not be described in detail here.

[0054] The current sampling circuit of this embodiment can sample the current flowing through the second resistor.

[0055] In one embodiment of the present disclosure, Figure 3 and Figure 4 As shown, the gain adjustment circuit 1400 includes a second operational amplifier A2, an eighth resistor R8, a ninth resistor R9 and a tenth resistor R10, the eighth resistor R8 is connected between the third terminal of the current sampling circuit 1200 and the inverting input terminal of the second operational amplifier A2, the ninth resistor R9 is connected between the non-inverting input terminal of the second operational amplifier A2 and the ground terminal GND, the tenth resistor R10 is connected between the inverting input terminal of the second operational amplifier A2 and the output terminal of the second operational amplifier A2, and the output terminal of the second operational amplifier A2 is connected to the first terminal of the threshold comparison circuit 1300.

[0056] In this embodiment, the gain adjustment circuit 1400 performs gain adjustment on the voltage V2 output by the current sampling circuit 1200, so that the voltage V3 output by the gain adjustment circuit 1400 can be expressed by the following formula:

[0057]

[0058] Wherein, R10 is the resistance value of the tenth resistor R10, and R8 is the resistance value of the eighth resistor R8.

[0059] In one embodiment of the present disclosure, Figure 3 and Figure 4As shown, the threshold comparison circuit 1300 includes an eleventh resistor R11, a twelfth resistor R12, and a first transistor Q1. The eleventh resistor R11 and the twelfth resistor R12 are connected in series between the positive power supply terminal VCC and the ground terminal GND of the power amplifier protection circuit. The first electrode of the first transistor Q1 is connected to the first potential point P1, the second electrode of the first transistor Q1 is connected to the second end of the gain adjustment circuit 1400, and the third electrode of the first transistor Q1 is connected to the negative input terminal of the power amplifier circuit 1100. Among them, the first potential point P1 is the potential point between the eleventh resistor R11 and the twelfth resistor R12.

[0060] In an example, the first transistor Q1 can be a PNP transistor, the first electrode of the first transistor Q1 is the base of the PNP transistor, the second electrode of the first transistor Q1 is the emitter of the PNP transistor, and the third electrode of the first transistor Q1 is the collector of the PNP transistor.

[0061] The positive power supply terminal VCC is connected to the ground terminal GND through the eleventh resistor R11 and the twelfth resistor R12. At this time, a threshold comparison voltage V41 is formed, which can be specifically expressed as:

[0062]

[0063] Wherein, R11 is the resistance value of the eleventh resistor R11, R12 is the resistance value of the twelfth resistor R12, VCC is the voltage of the positive power supply terminal VCC, and Ube is the voltage from the first electrode to the second electrode of the transistor.

[0064] When the voltage V3 of the input threshold comparison circuit 1300 is less than the threshold comparison voltage V41, the first transistor Q1 is disconnected and the threshold comparison circuit 1300 does not output a voltage; when the voltage V3 of the input threshold comparison circuit 1300 is greater than the threshold comparison voltage V41, the first transistor Q1 is turned on, and the threshold comparison circuit 1300 outputs a positive feedback voltage to the negative input terminal of the power amplifier circuit 1100 through the third electrode of the first transistor Q1. After the positive feedback voltage is inverted and amplified by the power amplifier circuit 1100, the voltage at the output terminal of the power amplifier circuit 1100 drops, which can reduce the current output by the output terminal of the power amplifier circuit 1100, thereby avoiding burning out the MOS tube inside the power amplifier circuit 1100.

[0065] In one embodiment of the present disclosure, in order to avoid connecting the audio output terminal Vout to the positive power supply terminal VCC of the power amplifier protection circuit 1000, thereby causing a short circuit between the audio output terminal Vout and the positive power supply terminal VCC, as shown in FIG. Figure 2 As shown, the power amplifier protection circuit 1000 further includes a DC detection circuit 1500, a first end of the DC detection circuit 1500 is connected to the audio output terminal Vout, and a second end of the DC detection circuit 1500 is connected to the third end of the gain adjustment circuit.

[0066] The third terminal of the gain adjustment circuit 1400 may be the inverting input terminal of the second operational amplifier A2.

[0067] The DC detection circuit 1500 does not output voltage when it is not detected that the audio output terminal Vout is connected to DC power. When it is detected that the audio output terminal Vout is connected to DC power, the DC detection circuit 1500 outputs a fault voltage V5 to the inverting input terminal of the second operational amplifier A2 of the gain adjustment circuit 1400.

[0068] The gain adjustment circuit 1400 may mix the received fault voltage V5 and the voltage V2 output by the current sampling circuit 1200 and then perform gain adjustment.

[0069] In the case of a short circuit between the audio output terminal Vout and the positive power supply terminal VCC, the direction of the current flowing through the second resistor R2 may be as follows: Figure 3 and Figure 4 The direction is opposite to that shown by the arrow in the middle. The voltage across the second resistor R2 is V1, where V1 is the difference between the voltage at the first end of the second resistor R2 and the voltage at the second end of the second resistor R2. Figure 3 and Figure 4 The current sampling circuit 1200 shown processes the voltage V1 across the second resistor R2. The voltage V2 output by the current sampling circuit 1200 can be expressed by the following formula:

[0070]

[0071] Wherein, R4 is the resistance value of the fourth resistor R4 and the fifth resistor R5, and R6 is the resistance value of the sixth resistor R6 and the seventh resistor R7.

[0072] In one embodiment of the present disclosure, Figure 3 and Figure 4 As shown, the DC detection circuit 1500 includes a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, a clamping circuit 1510, and a third transistor Q3. The fifteenth resistor R15 and the sixteenth resistor R16 are connected in series between the audio output terminal Vout and the ground terminal GND. The clamping circuit 1510 is connected between the first electrode of the third transistor Q3 and the ground terminal GND. The first electrode of the third transistor Q3 is also connected to the third potential point P3. The third electrode of the third transistor Q3 is connected to the positive power supply terminal VCC of the power amplifier protection circuit. The seventeenth resistor R17 is connected between the second electrode of the third transistor Q3 and the third terminal of the gain adjustment circuit 1400. Among them, the third potential point P3 is the potential point between the fifteenth resistor R15 and the sixteenth resistor R16.

[0073] The third terminal of the gain adjustment circuit 1400 may be the inverting input terminal of the second operational amplifier A2.

[0074] In an example, the third transistor Q3 may be an NPN transistor, the first electrode of the third transistor Q3 is the base of the NPN transistor, the second electrode of the third transistor Q3 is the emitter of the NPN transistor, and the third electrode of the third transistor Q3 is the collector of the NPN transistor.

[0075] When there is no short circuit between the audio output terminal Vout and the positive power supply terminal VCC, only the AC audio signal flows through the audio output terminal Vout, and the AC audio signal does not contain a DC component. The third transistor Q3 is turned off.

[0076] In the case of a short circuit between the audio output terminal Vout and the positive power supply terminal VCC, the clamp circuit 1510 can be such that the voltage of the first electrode of the third transistor Q3 does not exceed the clamp voltage. When the voltage of the third potential point P3 is less than or equal to the clamp voltage, the clamp circuit 1510 does not work. When the voltage of the first electrode of the third transistor Q3 is greater than the voltage from the first electrode to the second electrode of the third transistor Q3, the third transistor Q3 is turned on.

[0077] When the third transistor Q3 is turned off, the DC detection circuit 1500 does not output a voltage. When the third transistor Q3 is turned on, the DC detection circuit 1500 outputs a fifth voltage V5, wherein the fifth voltage V5 can be expressed as:

[0078] V5=V6-Ube

[0079] Wherein, V6 represents the first electrode voltage of the third transistor Q3, and Ube represents the voltage from the first electrode to the second electrode of the transistor. After the voltage of the direct current connected to the audio output terminal Vout is divided by the fifteenth resistor R15 and the sixteenth resistor R16, when the voltage of the third potential point P3 is less than or equal to the clamping voltage, the first electrode voltage of the third transistor Q3 is equal to the voltage of the third potential point P3, and when the voltage of the third potential point P3 is greater than the clamping voltage, the first electrode voltage of the third transistor Q3 is equal to the clamping voltage.

[0080] In one embodiment, Figure 4 As shown, the clamping circuit 1510 may include a first diode D1 and a second diode D2 connected in series between the first electrode of the third transistor Q3 and the ground terminal GND, the anode of the first diode D1 is connected to the first electrode of the third transistor Q3, the cathode of the first diode D1 is connected to the anode of the second diode D2, and the cathode of the second diode D2 is connected to the ground terminal GND.

[0081] In this embodiment, the maximum value of the fifth voltage V5 may be approximately 0.7V.

[0082] Furthermore, the gain adjustment circuit 1400 may mix the received fault voltage V5 and the voltage V2 output by the current sampling circuit 1200 and then perform gain adjustment, so that the voltage V3 output by the gain adjustment circuit 1400 may be expressed by the following formula:

[0083]

[0084] Wherein, R10 is the resistance value of the tenth resistor R10, and R17 is the resistance value of the seventeenth resistor.

[0085] On this basis, if Figure 3 and Figure 4 As shown, the threshold comparison circuit 1300 further includes a thirteenth resistor R13, a fourteenth resistor R14, and a second transistor Q2. The thirteenth resistor R13 and the fourteenth resistor R14 are connected in series between the negative power supply terminal VEE and the ground terminal GND of the power amplifier protection circuit. The first electrode of the second transistor Q2 is connected to the second potential point P2, the second electrode of the second transistor Q2 is connected to the second end of the gain adjustment circuit 1400, and the third electrode of the second transistor Q2 is connected to the negative input terminal of the power amplifier circuit 1100. The second potential point P2 is a potential point between the thirteenth resistor R13 and the fourteenth resistor R14.

[0086] In an example, the second transistor Q2 may be an NPN transistor, the first electrode of the second transistor Q2 is the base of the NPN transistor, the second electrode of the second transistor Q2 is the emitter of the NPN transistor, and the third electrode of the second transistor Q2 is the collector of the NPN transistor.

[0087] The negative power supply terminal VEE is connected to the ground terminal GND through the thirteenth resistor R13 and the fourteenth resistor R14. At this time, a threshold comparison voltage V42 is formed, which can be specifically expressed as:

[0088]

[0089] Wherein, R13 is the resistance value of the thirteenth resistor R13, R14 is the resistance value of the fourteenth resistor R14, VEE is the voltage of the negative power supply terminal VEE, and Ube is the voltage from the first electrode to the second electrode of the transistor.

[0090] When the voltage V3 of the input threshold comparison circuit 1300 is greater than the threshold comparison voltage V42, the second transistor Q2 is disconnected and the threshold comparison circuit 1300 does not output a voltage; when the voltage V3 of the input threshold comparison circuit 1300 is less than the threshold comparison voltage V42, the second transistor Q2 is turned on, and the threshold comparison circuit 1300 outputs a negative feedback voltage to the negative input terminal of the power amplifier circuit 1100 through the third electrode of the second transistor Q2. After the negative feedback voltage is inverted and amplified by the power amplifier circuit 1100, the voltage at the output terminal of the power amplifier circuit 1100 rises to resist the external voltage and limit the current input to the power amplifier circuit 1100, thereby avoiding burning out the MOS tube inside the power amplifier circuit 1100.

[0091] Through the embodiments of the present disclosure, in the event of a short circuit between the audio output terminal and the positive power supply terminal, the power amplifier protection circuit increases the output voltage to resist the external voltage and limits the current input to the power amplifier circuit, thereby avoiding burning out electronic devices such as MOS tubes inside the power amplifier circuit.

[0092] In one embodiment of the present disclosure, Figure 3 and Figure 4 As shown, the power amplifier protection circuit 1000 further includes an eighteenth resistor R18 and a first capacitor C1, and the eighteenth resistor R18 and the first capacitor C1 are connected in parallel between the second end of the gain adjustment circuit 1400 and the first end of the threshold comparison circuit 1300.

[0093] The first capacitor C1 can play an accelerating role.

[0094] In one embodiment of the present disclosure, Figure 3 and Figure 4 As shown, the power amplifier protection circuit 1000 further includes a nineteenth resistor R19 , which is connected between the second end of the threshold comparison circuit 1300 and the negative input end of the power amplifier circuit 1100 .

[0095] In one embodiment of the present disclosure, Figure 2 As shown, the power amplifier protection circuit 1000 may further include a filter circuit 1600 , and the filter circuit 1600 may be connected between the output end of the power amplifier circuit 1100 and the second resistor R2 .

[0096] Specifically, the filter circuit 1600 can be any one or more of an LC filter circuit, an RC filter circuit, and an LC filter circuit in any form, which is not limited here.

[0097] In this embodiment, the power amplifier protection circuit is implemented by discrete electronic devices, which can reduce the hardware cost of the power amplifier protection circuit.

[0098] Below Figure 4Taking the circuit structure shown as an example, the working principle of the power amplifier protection circuit 1000 of this embodiment is described.

[0099] When there is no short circuit between the audio output terminal Vout and the positive power supply terminal VCC, only the AC audio signal flows through the audio output terminal Vout, and the AC audio signal does not contain a DC component, and the third transistor Q3 is turned off.

[0100] The direction of the current flowing through the second resistor R2 can be as follows: Figure 4 The direction indicated by the arrow is the same, the voltage across the second resistor R2 is V1, wherein V1 is the difference between the voltage across the first end of the second resistor R2 and the voltage across the second end of the second resistor R2. The voltage V1 across the second resistor R2 is processed by the current sampling circuit 1200, and the voltage V2 output by the current sampling circuit 1200 can be expressed by the following formula:

[0101]

[0102] Wherein, R4 is the resistance value of the fourth resistor R4 and the fifth resistor R5, and R6 is the resistance value of the sixth resistor R6 and the seventh resistor R7.

[0103] The gain adjustment circuit 1400 performs gain adjustment on the voltage V2 output by the current sampling circuit 1200, so that the voltage V3 output by the gain adjustment circuit 1400 can be expressed by the following formula:

[0104]

[0105] Wherein, R10 is the resistance value of the tenth resistor R10, and R8 is the resistance value of the eighth resistor R8.

[0106] In the case that there is no short circuit between the audio output terminal Vout and the positive power terminal VCC, the voltage V3 input to the threshold comparison circuit 1300 is greater than the threshold comparison voltage V42.

[0107] When the output current of the power amplifier circuit 1100 is normal, the voltage V3 of the input threshold comparison circuit 1300 is less than the threshold comparison voltage V41 and greater than the threshold comparison voltage V42, the first transistor Q1 and the second transistor Q2 are both disconnected, and the threshold comparison circuit 1300 does not output voltage. When the output current of the power amplifier circuit 1100 is too large, the voltage V3 of the input threshold comparison circuit 1300 is greater than the threshold comparison voltage V41, the first transistor Q1 is turned on, and the second transistor Q2 is disconnected, and the threshold comparison circuit 1300 outputs a positive feedback voltage to the negative input terminal of the power amplifier circuit 1100 through the third electrode of the first transistor Q1. After the positive feedback voltage is inverted and amplified by the power amplifier circuit 1100, the voltage at the output terminal of the power amplifier circuit 1100 drops, which can reduce the current output by the output terminal of the power amplifier circuit 1100, thereby avoiding burning out the MOS tube inside the power amplifier circuit 1100.

[0108] In the case where the audio output terminal Vout is short-circuited with the positive power supply terminal VCC, a DC signal is injected into the audio output terminal Vout, and the clamping circuit 1510 can be such that the voltage of the first electrode of the third transistor Q3 does not exceed the clamping voltage. In the case where the voltage of the first electrode of the third transistor Q3 is greater than the voltage from the first electrode to the second electrode of the third transistor Q3, the third transistor Q3 is turned on, and the DC detection circuit 1500 outputs the fifth voltage V5.

[0109] The direction of the current flowing through the second resistor R2 can be as follows: Figure 4 The direction indicated by the arrow is opposite, and the voltage across the second resistor R2 is V1, wherein V1 is the difference between the voltage across the first end of the second resistor R2 and the voltage across the second end of the second resistor R2. The voltage V1 across the second resistor R2 is processed by the current sampling circuit 1200, and the voltage V2 output by the current sampling circuit 1200 can be expressed by the following formula:

[0110]

[0111] Wherein, R4 is the resistance value of the fourth resistor R4 and the fifth resistor R5, and R6 is the resistance value of the sixth resistor R6 and the seventh resistor R7.

[0112] The gain adjustment circuit 1400 may mix the received fault voltage V5 and the voltage V2 output by the current sampling circuit 1200 and then perform gain adjustment, so that the voltage V3 output by the gain adjustment circuit 1400 may be expressed by the following formula:

[0113]

[0114] Wherein, R10 is the resistance value of the tenth resistor R10, and R17 is the resistance value of the seventeenth resistor.

[0115] When the voltage V3 of the input threshold comparison circuit 1300 is less than the threshold comparison voltage V41 and greater than the threshold comparison voltage V42, the first transistor Q1 and the second transistor Q2 are both disconnected, and the threshold comparison circuit 1300 does not output a voltage; when the voltage V3 of the input threshold comparison circuit 1300 is less than the threshold comparison voltage V42, the first transistor Q1 is disconnected and the second transistor Q2 is turned on, and the threshold comparison circuit 1300 outputs a negative feedback voltage to the negative input terminal of the power amplifier circuit 1100 through the third electrode of the second transistor Q2. After the negative feedback voltage is inverted and amplified by the power amplifier circuit 1100, the voltage at the output terminal of the power amplifier circuit 1100 rises to resist the external voltage and limit the current input to the power amplifier circuit 1100, thereby avoiding burning out the MOS tube inside the power amplifier circuit 1100.

[0116] <Electronic equipment>

[0117] The present disclosure also provides an electronic device, which may include a speaker and the power amplifier protection circuit described in any of the aforementioned embodiments, and the audio output end of the power amplifier protection circuit may be connected to the speaker.

[0118] In this embodiment, the electronic device is any electronic product with an audio playback function, for example, it can be a mobile phone, a tablet computer, a laptop computer, headphones, speakers, a virtual reality device, an augmented reality device, or a vehicle.

[0119] The above embodiments mainly focus on describing the differences from other embodiments, but it should be clear to those skilled in the art that the above embodiments can be used alone or in combination with each other as needed.

[0120] Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A power amplifier protection circuit, characterized in that: It includes an audio input terminal, an audio output terminal, a power amplifier circuit, a first resistor, a second resistor, a third resistor, a current sampling circuit, and a threshold comparison circuit. The positive input terminal of the power amplifier circuit is connected to the audio input terminal, the first resistor is connected between the negative input terminal of the power amplifier circuit and the ground terminal of the power amplifier protection circuit, the second resistor is connected between the output terminal of the power amplifier circuit and the audio output terminal, and the third resistor is connected between the negative input terminal of the power amplifier circuit and the output terminal of the power amplifier circuit; The first end of the current sampling circuit is connected to the first end of the second resistor, the second end of the current sampling circuit is connected to the second end of the second resistor, the third end of the current sampling circuit is connected to the first end of the threshold comparison circuit, and the second end of the threshold comparison circuit is connected to the negative input end of the power amplifier circuit.

2. The power amplifier protection circuit according to claim 1, characterized in that: The power amplifier protection circuit also includes a gain adjustment circuit, a first end of the gain adjustment circuit is connected to the third end of the current sampling circuit, and a second end of the gain adjustment circuit is connected to the first end of the threshold comparison circuit.

3. The power amplifier protection circuit according to claim 2, characterized in that: The current sampling circuit includes a first operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor. A first end of the second resistor is connected to the output end of the power amplifier circuit, and a second end of the second resistor is connected to the audio output end; The fourth resistor is connected between the inverting input terminal of the first operational amplifier and the first end of the second resistor, the fifth resistor is connected between the non-inverting input terminal of the first operational amplifier and the second end of the second resistor, the sixth resistor is connected between the inverting input terminal of the first operational amplifier and the output terminal of the first operational amplifier, and the seventh resistor is connected between the non-inverting input terminal of the first operational amplifier and the ground terminal.

4. The power amplifier protection circuit according to claim 2, characterized in that: The gain adjustment circuit includes a second operational amplifier, an eighth resistor, a ninth resistor and a tenth resistor, the eighth resistor is connected between the third terminal of the current sampling circuit and the inverting input terminal of the second operational amplifier, the ninth resistor is connected between the non-inverting input terminal of the second operational amplifier and the ground terminal, the tenth resistor is connected between the inverting input terminal of the second operational amplifier and the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the first terminal of the threshold comparison circuit.

5. The power amplifier protection circuit according to claim 2, characterized in that: The threshold comparison circuit includes an eleventh resistor, a twelfth resistor, and a first transistor, the eleventh resistor and the twelfth resistor are connected in series between the positive power supply terminal of the power amplifier protection circuit and the ground terminal, the first electrode of the first transistor is connected to the first potential point, the second electrode of the first transistor is connected to the second end of the gain adjustment circuit, and the third electrode of the first transistor is connected to the negative input terminal of the power amplifier circuit; The first potential point is a potential point between the eleventh resistor and the twelfth resistor.

6. The power amplifier protection circuit according to any one of claims 2 to 5, characterized in that: The power amplifier protection circuit also includes a DC detection circuit, a first end of the DC detection circuit is connected to the audio output end, and a second end of the DC detection circuit is connected to a third end of the gain adjustment circuit.

7. The power amplifier protection circuit according to claim 6, characterized in that: The DC detection circuit includes a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a clamping circuit, and a third transistor, the fifteenth resistor and the sixteenth resistor are connected in series between the audio output terminal and the ground terminal, the clamping circuit is connected between the first electrode of the third transistor and the ground terminal, the first electrode of the third transistor is also connected to a third potential point, the third electrode of the third transistor is connected to the positive power supply terminal of the power amplifier protection circuit, and the seventeenth resistor is connected between the second electrode of the third transistor and the third terminal of the gain adjustment circuit; The third potential point is a potential point between the fifteenth resistor and the sixteenth resistor.

8. The power amplifier protection circuit according to claim 6, characterized in that: The threshold comparison circuit further includes a thirteenth resistor, a fourteenth resistor, and a second transistor, the thirteenth resistor and the fourteenth resistor are connected in series between the negative power supply terminal of the power amplifier protection circuit and the ground terminal, the first electrode of the second transistor is connected to the second potential point, the second electrode of the second transistor is connected to the second end of the gain adjustment circuit, and the third electrode of the second transistor is connected to the negative input terminal of the power amplifier circuit; The second potential point is a potential point between the thirteenth resistor and the fourteenth resistor.

9. The power amplifier protection circuit according to claim 1, characterized in that: The power amplifier protection circuit further includes a nineteenth resistor, and the nineteenth resistor is connected between the second end of the threshold comparison circuit and the negative input end of the power amplifier circuit.

10. An electronic device, characterized in that: It comprises a speaker and a power amplifier protection circuit according to any one of claims 1 to 9, wherein the audio output end is connected to the speaker.

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