A Class D audio power amplifier short-circuit detection circuit and power amplifier

Abstract

The invention discloses a novel short-circuit detection circuit and power amplifier of a class D audio power amplifier. The short-circuit detection circuit is connected to the output end of the class D audio power amplifier, and the short-circuit detection circuit is connected to the class D audio power amplifier; the short-circuit detection circuit includes a high-pass filter, an amplifier U2A, and a rectifier D1. The high-pass filter includes a capacitor C1 and an inductor L1. One end of the capacitor C1 is connected to the output end of the class D audio power amplifier, and the other end is connected to one end of the inductor L1; the common point of the capacitor C1 and the inductor L1 is connected to the reverse input end of the amplifier U2A through a resistor R3, the same-direction input end of the amplifier U2A is grounded, and the output end of the amplifier U2A is connected to the rectifier D1. The current after the rectifier D1 outputs is used as a detection value VDEC and returned to the reverse input end of the comparator U1A. The invention has a reasonable structure and can be applied to the class D audio power amplifier. When the short circuit occurs at any time, the driving circuit can be turned off in time.

Description

Technical Field

[0001] The present invention relates to the technical field of short-circuit detection of a class D audio power amplifier, and in particular to a short-circuit detection circuit of a class D audio power amplifier and a power amplifier. Background Art

[0002] The working principle of the traditional protection circuit of Class D audio power amplifier is as follows Figure 1 As shown in the figure, the basic working principle of Class D amplifier is PWM modulation. After the carrier frequency is determined (for example, 400KHz), the pulse width determines the size of the signal. As the input signal of the amplifier increases, the positive pulse width increases. When the signal is small, the positive pulse width is small. Regardless of whether the amplifier has a signal input, the carrier frequency (400KHz) always exists. Working principle: R3 and R4 in the figure are both current detection resistors. The working principles of R3 and R4 are the same. Now only R3 is analyzed: the voltage on R3 increases as the current flowing through R3 increases. When POUT is short-circuited to the ground, the current is the largest and the voltage reaches the maximum value. Through the comparator, when the voltage exceeds the reference voltage of the comparator, the state of the comparator flips. The drive circuit is controlled by this flip amount to stop the drive circuit from working, thereby playing a protective role.

[0003] The protection circuit detection method of traditional audio power amplifiers is stable and feasible, and has been used for Class AB power amplifiers and Class D amplifiers. However, it also has obvious disadvantages:

[0004] (1) Only when the input signal reaches a certain value can a short circuit generate a voltage sufficient to cause the comparator to flip.

[0005] (2) If the input signal is relatively small, the comparator may not flip.

[0006] (3) The integrating effect of capacitors C1 and C2 will delay the change of this voltage.

[0007] (4) During power amplification, R3 and R4 need to withstand currents ranging from several amperes to tens of amperes (i.e., sufficiently large currents), so high-power resistors are required.

[0008] When the power amplifier does not have sufficient input voltage, if a short circuit occurs, the comparator will not flip, the power tube will continue to work, and the heat will increase significantly until it is damaged. Summary of the invention

[0009] In view of at least one defect of the protection circuit detection of the traditional audio power amplifier in the background technology, the purpose of the present invention is to provide a short-circuit detection circuit and a power amplifier of a Class D audio power amplifier, which can promptly shut down the driving circuit when a short circuit occurs at any time.

[0010] The present invention is achieved through the following technical solutions:

[0011] A short-circuit detection circuit for a class D audio power amplifier, the short-circuit detection circuit is connected to the output end of the class D audio power amplifier, and the short-circuit detection circuit is connected to the driving controller of the class D audio power amplifier through a comparator U1A; the short-circuit detection circuit includes a high-pass filter, an amplifier U2A, and a rectifier D1;

[0012] The high-pass filter includes a capacitor C1 and an inductor L1, one end of the capacitor C1 is connected to the output end of the class D audio power amplifier, the other end of the capacitor C1 is connected to one end of the inductor L1, and the other end of the inductor L1 is grounded; the common point of the capacitor C1 and the inductor L1 is connected to the reverse input end of the amplifier U2A through a resistor R3, the same-direction input end of the amplifier U2A is grounded, the output end of the amplifier U2A is connected to the rectifier D1, and the current output by the rectifier D1 is used as the detection value VDEC and returned to the reverse input end of the comparator U1A;

[0013] It also includes a capacitor C2 and a resistor R4, and both the capacitor C2 and the resistor R4 are connected in parallel with the amplifier U2A.

[0014] The working principle is:

[0015] From the principle of Class D power amplifier, we can see that: "regardless of whether there is a signal input to the amplifier, the carrier frequency (400KHz) always exists." From actual product testing, the value of this 400KHz output from the power output terminal is greater than 0.8V (RMS). Using this ever-present carrier frequency (400KHz), as long as there is a short circuit, this frequency becomes "0". 0.8V (RMS) is also "0".

[0016] The present invention includes a high-pass filter, an amplifier U2A, and a rectifier D1. The high-pass filter is used to separate the switching carrier signal from the output end of the class D audio power amplifier, that is, 400KHz is separated; the separated switching filter signal is amplified by the amplifier U2A to amplify the carrier frequency signal, which is to meet the needs of the class D power amplifier with a different carrier frequency signal, and the signal is amplified to be rectified, with an amplification factor of -R4 / R3; the carrier frequency signal is then converted into a direct current through the rectifier D1;

[0017] Based on the output POUT of the class D audio power amplifier, when there is no short circuit to the ground GND, the detection value VDEC must be a relatively fixed value; and it is greater than the reference voltage VREF; at this time, the comparator U1A is in a steady state.

[0018] When the output POUT of the class D audio power amplifier is short-circuited to the ground GND, the output of the amplifier U2A is 0; the detection value VDEC is 0; and it is less than the reference voltage VREF. At this time, the comparator U1A flips, and the driving controller turns off the MOS tubes Q1 and Q2 in the class D audio power amplifier, which plays a role in protecting the MOS tubes Q1 and Q2.

[0019] The invention has a simple and reasonable structure and can be applied to a class D audio power amplifier and can turn off the driving circuit in time when the amplifier is short-circuited at any time.

[0020] As a further preferred solution, a capacitor C3 is further included, one end of which is connected to the output end of the rectifier D1 and the other end is grounded; one of the functions of the capacitor C3 is to filter the rectified signal, and the other function is to maintain the DC voltage.

[0021] As a further preferred solution, the capacity of the capacitor C3 is 0.1 uF.

[0022] As a further preferred solution, a resistor R5 is further included, the resistor R5 is connected in parallel with the capacitor C3, one end of the resistor R5 is connected to the output end of the rectifier D1, and the other end is grounded; the function of the resistor R5 is to discharge the voltage on the capacitor C3. The value of the resistor R5 determines the cycle of repeated startup of the class D power amplifier.

[0023] As a further preferred solution, the resistance of the resistor R5 is 1KΩ.

[0024] As a further preferred solution, the non-inverting input terminal of the comparator U1A is connected to the reference voltage VREF, and the output terminal of the comparator U1A is connected to the drive controller.

[0025] As a further preferred solution, the cut-off frequency of the high-pass filter is 106KHz, which basically meets the carrier frequency of all class D power amplifiers; the inductance of the inductor L1 is 1.5uH, and the capacity of the capacitor C1 is 1uF.

[0026] As a further preferred solution, the resistance value of the resistor R3 is 10KΩ, and the resistance value of the resistor R4 is 20KΩ.

[0027] As a further preferred solution, the model of the amplifier U2A is LM311.

[0028] On the other hand, the present invention further provides a class D audio power amplifier, the class D audio power amplifier includes a drive controller, a resistor R1, a resistor R2, a MOS tube Q1, a MOS tube Q2, a comparator U1A, and also includes a short-circuit detection circuit of a class D audio power amplifier according to any one of claims 1 to 9, one end of the drive controller is connected to the resistor R1, the resistor R1 is connected to the G pole of the MOS tube Q1, the D pole of the MOS tube Q1 is connected to the positive pole of the power supply, and the S pole of the MOS tube Q1 is connected to the D pole of the MOS tube Q2, the other end of the drive controller is connected to the resistor R2, the resistor R2 is connected to the G pole of the MOS tube Q2, the S pole of the MOS tube Q2 is connected to the negative pole of the power supply, and the common end of the D pole of the MOS tube Q2 and the S pole of the MOS tube Q1 outputs a switching carrier signal;

[0029] The short-circuit detection circuit of the class D audio power amplifier is connected to the output end of the class D audio power amplifier, the output end of the short-circuit detection circuit of the class D audio power amplifier is connected to the reverse input end of the comparator U1A, the non-inverting input end of the comparator U1A is connected to the reference voltage VREF, and the output end of the comparator U1A is connected to the drive controller.

[0030] The present invention can solve the problem of the traditional circuit: that is, if the class D audio power amplifier is short-circuited at any time, the driving circuit can be turned off in time. The class D audio power amplifier of the present invention can detect the short-circuit signal using the short-circuit detection circuit regardless of whether there is audio input or not, and regardless of the size of the input audio signal, and can play the greatest protective role for the MOS tube Q1 and MOS tube Q2 in the class D audio power amplifier. The damage of MOS tube Q1 and MOS tube Q2 during the production process and the user's use process is greatly reduced, which is conducive to improving the profit margin and corporate reputation of the enterprise.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] 1. The short-circuit detection circuit structure of a class D audio power amplifier of the present invention is simple and reasonable, and can be applied to the class D audio power amplifier to shut down the driving circuit in time when a short circuit occurs at any time;

[0033] 2. The present invention can solve the problem of traditional circuits: that is, if the class D audio power amplifier is short-circuited at any time, the driving circuit can be turned off in time. The class D audio power amplifier of the present invention can detect the short-circuit signal using the short-circuit detection circuit regardless of whether there is audio input or not, and regardless of the size of the input audio signal, and can play the greatest protective role for the MOS tube Q1 and MOS tube Q2 in the class D audio power amplifier. The damage of MOS tube Q1 and MOS tube Q2 during the production process and the user's use process is greatly reduced, which is conducive to improving the company's profit margin and corporate reputation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0035] Figure 1 This is a working principle diagram of a traditional protection circuit for a Class D audio power amplifier.

[0036] Figure 2 The present invention is a short-circuit detection circuit diagram of a class D audio power amplifier. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0038] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other instances, well-known structures, circuits, materials, or methods are not specifically described in order to avoid obscuring the present invention.

[0039] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] In the description of the present invention, the directions or positional relationships indicated by terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “vertical”, “horizontal”, “high”, “low”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the scope of protection of the present invention.

[0041] Example 1

[0042] like Figure 1 , Figure 2 As shown, the present invention provides a short-circuit detection circuit for a class D audio power amplifier, wherein the short-circuit detection circuit is connected to the output end of the class D audio power amplifier, and the short-circuit detection circuit is connected to the driving controller of the class D audio power amplifier through a comparator U1A; the short-circuit detection circuit includes a high-pass filter, an amplifier U2A, and a rectifier D1;

[0043] The high-pass filter includes a capacitor C1 and an inductor L1, one end of the capacitor C1 is connected to the output end of the class D audio power amplifier, the other end of the capacitor C1 is connected to one end of the inductor L1, and the other end of the inductor L1 is grounded; the common point of the capacitor C1 and the inductor L1 is connected to the reverse input end of the amplifier U2A through a resistor R3, the same-direction input end of the amplifier U2A is grounded, the output end of the amplifier U2A is connected to the rectifier D1, and the current output by the rectifier D1 is used as the detection value VDEC and returned to the reverse input end of the comparator U1A;

[0044] It also includes a capacitor C2 and a resistor R4, and both the capacitor C2 and the resistor R4 are connected in parallel with the amplifier U2A.

[0045] In this embodiment, a capacitor C3 is also included, one end of which is connected to the output end of the rectifier D1 and the other end is grounded; one of the functions of the capacitor C3 is to filter the rectified signal and another function is to maintain the DC voltage. The capacity of the capacitor C3 is 0.1uF.

[0046] In this embodiment, a resistor R5 is further included. The resistor R5 is connected in parallel with the capacitor C3. One end of the resistor R5 is connected to the output end of the rectifier D1 and the other end is grounded. The function of the resistor R5 is to discharge the voltage on the capacitor C3. The value of the resistor R5 determines the cycle of repeated startup of the class D power amplifier. The resistance value of the resistor R5 is 1KΩ.

[0047] In this embodiment, the non-inverting input terminal of the comparator U1A is connected to the reference voltage VREF, and the output terminal of the comparator U1A is connected to the driving controller.

[0048] In this embodiment, the cut-off frequency of the high-pass filter is 106KHz, which basically meets the carrier frequency of all class D amplifiers. The inductance of the inductor L1 is 1.5uH, and the capacity of the capacitor C1 is 1uF.

[0049] In this embodiment, the resistance value of the resistor R3 is 10KΩ, and the resistance value of the resistor R4 is 20KΩ.

[0050] In this embodiment, the model of the amplifier U2A is LM311.

[0051] The working principle is:

[0052] From the principle of Class D power amplifier, we can see that: "regardless of whether there is a signal input to the amplifier, the carrier frequency (400KHz) always exists." From actual product testing, the value of this 400KHz output from the power output terminal is greater than 0.8V (RMS). Using this ever-present carrier frequency (400KHz), as long as there is a short circuit, this frequency becomes "0". 0.8V (RMS) is also "0".

[0053] The present invention includes a high-pass filter, an amplifier U2A, and a rectifier D1. The high-pass filter is used to separate the switching carrier signal from the output end of the class D audio power amplifier, that is, 400KHz is separated; the separated switching filter signal is amplified by the amplifier U2A to amplify the carrier frequency signal, which is to meet the needs of the class D power amplifier with a different carrier frequency signal, and the signal is amplified to be rectified, with an amplification factor of -R4 / R3; the carrier frequency signal is then converted into a direct current through the rectifier D1;

[0054] Based on the output POUT of the class D audio power amplifier, when there is no short circuit to the ground GND, the detection value VDEC must be a relatively fixed value; and it is greater than the reference voltage VREF; at this time, the comparator U1A is in a steady state.

[0055] When the output POUT of the class D audio power amplifier is short-circuited to the ground GND, the output of the amplifier U2A is 0; the detection value VDEC is 0; and it is less than the reference voltage VREF. At this time, the comparator U1A flips, and the driving controller turns off the MOS tubes Q1 and Q2 in the class D audio power amplifier, which plays a role in protecting the MOS tubes Q1 and Q2.

[0056] The invention has a simple and reasonable structure and can be applied to a class D audio power amplifier and can turn off the driving circuit in time when the amplifier is short-circuited at any time.

[0057] Example 2

[0058] like Figure 1 , Figure 2As shown, the difference between this embodiment and embodiment 1 is that this embodiment provides a class D audio power amplifier, the class D audio power amplifier includes a drive controller, a resistor R1, a resistor R2, a MOS tube Q1, a MOS tube Q2, a comparator U1A, and also includes a short-circuit detection circuit of a class D audio power amplifier described in embodiment 1, one end of the drive controller is connected to the resistor R1, the resistor R1 is connected to the G pole of the MOS tube Q1, the D pole of the MOS tube Q1 is connected to the positive pole of the power supply, and the S pole of the MOS tube Q1 is connected to the D pole of the MOS tube Q2, the other end of the drive controller is connected to the resistor R2, the resistor R2 is connected to the G pole of the MOS tube Q2, the S pole of the MOS tube Q2 is connected to the negative pole of the power supply, and the common end of the D pole of the MOS tube Q2 and the S pole of the MOS tube Q1 outputs a switching carrier signal;

[0059] The short-circuit detection circuit of a Class D audio power amplifier described in Example 1 is connected to the output end of the Class D audio power amplifier, the output end of the short-circuit detection circuit of a Class D audio power amplifier described in Example 1 is connected to the reverse input end of the comparator U1A, the non-inverting input end of the comparator U1A is connected to the reference voltage VREF, and the output end of the comparator U1A is connected to the drive controller.

[0060] Among them, the MOS tube Q1 and the MOS tube Q2 are both P-channel MOS tubes.

[0061] The working principle of the traditional protection circuit of Class D audio power amplifier is as follows Figure 1 As shown, the basic working principle of the Class D power amplifier is PWM modulation. After the carrier frequency is determined (for example, 400KHz), the pulse width determines the size of the signal. As the input signal of the power amplifier increases, the positive pulse width increases, and when the signal is small, the positive pulse width is small. Regardless of whether the power amplifier has a signal input, the carrier frequency (400KHz) always exists. Working principle: R3 and R4 in the figure are current detection resistors. The working principles of R3 and R4 are the same. Now only R3 is analyzed: the voltage on R3 increases as the current flowing through R3 increases. When POUT is short-circuited to the ground, the current is the largest and the voltage reaches the maximum value. Through the comparator, when the voltage exceeds the reference voltage of the comparator, the state of the comparator flips. The amount of this flip is used to control the drive circuit to stop the drive circuit from working, thereby playing a protective role. The protection circuit detection method of the traditional audio power amplifier is stable and feasible, and has been used for class AB power amplifiers and class D amplifiers. However, there are also obvious disadvantages:

[0062] (1) Only when the input signal reaches a certain value can a short circuit generate a voltage sufficient to cause the comparator to flip.

[0063] (2) If the input signal is relatively small, the comparator may not flip.

[0064] (3) The integrating effect of capacitors C1 and C2 will delay the change of this voltage.

[0065] (4) During power amplification, R3 and R4 need to withstand currents ranging from several amperes to tens of amperes (i.e., sufficiently large currents), so high-power resistors are required.

[0066] When the power amplifier does not have sufficient input voltage, if a short circuit occurs, the comparator will not flip, the power tube will continue to work, and the heat will increase significantly until it is damaged.

[0067] Therefore, the present invention can solve the problem of the traditional circuit: that is, when the class D audio power amplifier is short-circuited at any time, the driving circuit can be turned off in time. The class D audio power amplifier of the present invention can detect the short-circuit signal using the short-circuit detection circuit regardless of whether there is audio input or not, and regardless of the size of the input audio signal, and can play the greatest protective role for the MOS tube Q1 and MOS tube Q2 in the class D audio power amplifier. The damage of MOS tube Q1 and MOS tube Q2 during the production process and the user's use process is greatly reduced, which is conducive to improving the profit margin and corporate reputation of the enterprise.

[0068] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A short-circuit detection circuit for a class D audio power amplifier, characterized in that: The short-circuit detection circuit is connected to the output end of the class-D audio power amplifier, and the short-circuit detection circuit is connected to the driving controller of the class-D audio power amplifier through the comparator U1A; the short-circuit detection circuit includes a high-pass filter, an amplifier U2A, and a rectifier D1; The high-pass filter includes a capacitor C1 and an inductor L1, one end of the capacitor C1 is connected to the output end of the class D audio power amplifier, the other end of the capacitor C1 is connected to one end of the inductor L1, and the other end of the inductor L1 is grounded; the common point of the capacitor C1 and the inductor L1 is connected to the reverse input end of the amplifier U2A through a resistor R3, the same-direction input end of the amplifier U2A is grounded, the output end of the amplifier U2A is connected to the rectifier D1, and the current output by the rectifier D1 is used as the detection value VDEC and returned to the reverse input end of the comparator U1A; It also includes a capacitor C2 and a resistor R4, and both the capacitor C2 and the resistor R4 are connected in parallel with the amplifier U2A.

2. A short-circuit detection circuit for a class D audio power amplifier according to claim 1, characterized in that: The capacitor C3 is also included, one end of the capacitor C3 is connected to the output end of the rectifier D1, and the other end is grounded.

3. The short-circuit detection circuit of a class D audio power amplifier according to claim 2, characterized in that: The capacity of the capacitor C3 is 0.1uF.

4. The short-circuit detection circuit of a class D audio power amplifier according to claim 2, characterized in that: The resistor R5 is also included. The resistor R5 is connected in parallel with the capacitor C3. One end of the resistor R5 is connected to the output end of the rectifier D1, and the other end is grounded.

5. The short-circuit detection circuit of a class D audio power amplifier according to claim 4, characterized in that: The resistance value of the resistor R5 is 1KΩ.

6. The short-circuit detection circuit of a class D audio power amplifier according to claim 1, characterized in that: The non-inverting input terminal of the comparator U1A is connected to the reference voltage VREF, and the output terminal of the comparator U1A is connected to the driving controller.

7. The short-circuit detection circuit of a class D audio power amplifier according to claim 1, characterized in that: The cut-off frequency of the high-pass filter is 106KHz; the inductance of the inductor L1 is 1.5uH, and the capacity of the capacitor C1 is 1uF.

8. The short-circuit detection circuit of a class D audio power amplifier according to claim 1, characterized in that: The resistance value of the resistor R3 is 10KΩ, and the resistance value of the resistor R4 is 20KΩ.

9. The short-circuit detection circuit of a class D audio power amplifier according to claim 1, characterized in that: The model of the amplifier U2A is LM311.

10. A class D audio power amplifier, characterized in that: The class D audio power amplifier includes a driving controller, a resistor R1, a resistor R2, a MOS tube Q1, a MOS tube Q2, and a comparator U1A, and also includes a short-circuit detection circuit of a class D audio power amplifier according to any one of claims 1 to 9, wherein one end of the driving controller is connected to the resistor R1, the resistor R1 is connected to the G pole of the MOS tube Q1, the D pole of the MOS tube Q1 is connected to the positive pole of the power supply, and the S pole of the MOS tube Q1 is connected to the D pole of the MOS tube Q2, and the other end of the driving controller is connected to the resistor R2, the resistor R2 is connected to the G pole of the MOS tube Q2, and the S pole of the MOS tube Q2 is connected to the negative pole of the power supply, and the common end of the D pole of the MOS tube Q2 and the S pole of the MOS tube Q1 outputs a switching carrier signal; The short-circuit detection circuit of the class D audio power amplifier is connected to the output end of the class D audio power amplifier, the output end of the short-circuit detection circuit of the class D audio power amplifier is connected to the reverse input end of the comparator U1A, the same-direction input end of the comparator U1A is connected to the reference voltage VREF, and the output end of the comparator U1A is connected to the drive controller.

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