Audio amplifier, electronic equipment and overcurrent protection method

Abstract

The invention relates to an audio amplifier, electronic equipment and an overcurrent protection method, and belongs to the field of electronic circuits. The audio amplifier comprises a power amplifier circuit and an overcurrent protection circuit, and the overcurrent protection circuit is connected with the power amplifier circuit. The power amplifier circuit comprises an amplifier, a gate driver and a power tube which are connected in sequence, and the gate driver is used for driving the power tube; and the overcurrent protection circuit is used for detecting the output current of the power tube, and limiting the output current of the power tube when the output current of the power tube exceeds a first threshold value and is not greater than a second threshold value. When the output current of the power tube exceeds the first threshold value and is not greater than the second threshold value, measures are taken in advance to limit the output current of the power tube, and the power tube is prevented from being closed as much as possible, so that the problem of audio interruption caused by instantaneous output of high power by a power amplifier chip can be improved, and the hearing experience of a user can be improved.

Description

Technical Field

[0001] The present application belongs to the field of electronic circuits, and specifically relates to an audio amplifier, an electronic device and an overcurrent protection method. Background Art

[0002] Power amplifier chips (power amplifier chips) often encounter abnormal situations during operation, such as output short circuit, which can easily cause the power tube to burn out due to overcurrent, so an overcurrent protection circuit needs to be set. The protection principle of the overcurrent protection circuit is: when it is detected that the current flowing through the power tube exceeds a certain threshold (the limit current value that the chip can withstand), the power tube will be turned off to protect the power amplifier chip. Summary of the invention

[0003] In view of this, the purpose of the present application is to provide an audio amplifier, an electronic device and an overcurrent protection method to improve the problem of audio interruption caused by the instantaneous high power output of the power amplifier chip.

[0004] The embodiment of the present application is implemented as follows:

[0005] In a first aspect, an embodiment of the present application provides an audio amplifier, comprising: a power amplifier circuit and an overcurrent protection circuit, the power amplifier circuit being connected to the power amplifier circuit; the power amplifier circuit comprising an amplifier, a gate drive and a power tube connected in sequence, wherein the gate drive is used to drive the power tube; the overcurrent protection circuit is used to detect the output current of the power tube, and when the output current of the power tube exceeds a first threshold value and is not greater than a second threshold value, the output current of the power tube is limited.

[0006] In the above embodiment, by adding an overcurrent protection circuit inside the audio amplifier, when it is detected that the output current of the power tube exceeds the first threshold and is not greater than the second threshold, measures can be taken in advance to limit the output current of the power tube before the output current exceeds the second threshold, and the power tube can be avoided from being directly shut down as much as possible, thereby improving the problem of audio interruption caused by the instantaneous high power output of the power amplifier chip, thereby improving the user's listening experience.

[0007] In combination with a possible implementation manner of the embodiment of the first aspect, the current limiting protection measure adopted for limiting the output current of the power tube includes one of the following: (i) controlling the gate drive to limit the output current of the power tube; (ii) controlling the amplifier to reduce the gain to reduce the output current of the power tube; (iii) controlling the gate drive to limit the output current of the power tube, if the output current of the power tube exceeds the first threshold value for a duration exceeding the first target duration after limiting the output current of the power tube, controlling the amplifier to reduce the gain to reduce the output current of the power tube.

[0008] In the above embodiment, one of the above-mentioned multiple current limiting protection measures can be selectively adopted to limit the output current of the power tube, which can achieve its purpose while increasing the flexibility of the scheme. At the same time, since the (i) method directly controls the gate drive to limit the output current of the power tube, it is beneficial to improve the response timeliness of the circuit; the (ii) method mainly reduces the gain of the amplifier, thereby reducing the signal amplitude of the output signal, and can also reduce the output current of the power tube, providing another option for limiting the output current of the power tube; the (iii) method adopts dual measures to limit the output current of the power tube, which can maximize the avoidance of the output current of the power tube exceeding the second threshold, thereby maximizing the avoidance of shutting down the power tube.

[0009] In combination with a possible implementation manner of the embodiment of the first aspect, controlling the gate drive to limit the output current of the power tube includes: reducing the duty cycle of the driving signal of the gate drive to limit the output current of the power tube.

[0010] In the above embodiment, the output current of the power tube can be limited by reducing the duty cycle of the gate drive signal, and directly shutting down the power tube can be avoided as much as possible.

[0011] In combination with a possible implementation manner of the embodiment of the first aspect, the overcurrent protection circuit is also used to control the gate drive to shut down the power tube if the output current of the power tube exceeds the first threshold for a duration exceeding a second target duration after taking current limiting protection measures.

[0012] In the above embodiment, after taking current limiting protection measures, if the circuit is in a state of triggering current limiting for a long time, so that the output current of the power tube exceeds a certain threshold for a long time, the power amplifier output is controlled to be shut down to reduce the risk of the power tube being burned out or damaged, thereby protecting the power amplifier chip.

[0013] In combination with a possible implementation manner of the embodiment of the first aspect, the overcurrent protection circuit is further used to control the gate drive to shut down the power tube when the output current of the power tube is greater than a second threshold.

[0014] In the above embodiment, when the output current of the power tube is greater than the second threshold, the gate drive is directly controlled to shut down the power tube to protect the power amplifier chip and solve the problem of excessive output power exceeding the chip threshold setting and burning the chip.

[0015] In combination with a possible implementation manner of the embodiment of the first aspect, the overcurrent protection circuit includes: a current detection device, a controller, and the controller is connected to the current detection device; the current detection device is used to detect the output current of the power tube; the controller is used to take the current limiting protection measure to limit the output current of the power tube when the output current of the power tube exceeds a first threshold value, and after taking the current limiting protection measure, if the output current of the power tube exceeds the first threshold value for a duration exceeding a second target duration, or if the output current of the power tube is greater than the second threshold value, then control the gate drive to shut down the power tube.

[0016] In the above embodiment, a current detection device is provided to detect the output current of the power tube, and a controller is used to determine the relationship between the output current and the first threshold value and the second threshold value. When the output current of the power tube exceeds the first threshold value, a current limiting protection measure is taken to limit the output current of the power tube, so that the probability of the output current exceeding the second threshold value can be reduced, and the power tube can be directly closed as much as possible, thereby improving the problem of audio interruption caused by the instantaneous high power output of the power amplifier chip, thereby improving the user's listening experience; and after the current limiting protection measure is taken, if the output current of the power tube exceeds the first threshold value for a duration exceeding the second target duration, or if the output current of the power tube is greater than the second threshold value, the gate drive is controlled to close the power tube, so that the power amplifier chip can be protected and the problem of excessive output power exceeding the chip threshold setting and burning the chip can be solved; at the same time, since the current detection device does not need to determine the relationship between the output current and the first threshold value and the second threshold value, only one current detection device needs to be provided, and this can simplify the circuit design.

[0017] In combination with a possible implementation manner of the embodiment of the first aspect, the overcurrent protection circuit includes: a first current detection unit, a second current detection unit and a controller, the controller being connected to the first current detection unit and the second current detection unit respectively; the first current detection unit is used to detect the output current of the power tube, and output a first indication signal when the output current of the power tube exceeds the first threshold value; the second current detection unit is used to detect the output current of the power tube, and output a second indication signal when the output current of the power tube exceeds the second threshold value; the controller is used to take the current limiting protection measure to limit the output current of the power tube when receiving the first indication signal; and if the duration of receiving the first indication signal after taking the current limiting protection measure exceeds the second target duration, or if the second indication signal is received, control the gate drive to shut down the power tube.

[0018] In the above embodiment, the first current detection unit and the second current detection unit are used to determine the relationship between the first threshold value and the second threshold value, so that the controller does not need to determine the relationship between the first threshold value and the second threshold value. It only needs to take current limiting protection measures to limit the output current of the power tube when the first indication signal is received, and if the duration of the first indication signal received after the current limiting protection measures are taken exceeds the second target duration, or if the second indication signal is received, the gate drive is controlled to shut down the power tube, which can protect the power amplifier chip and solve the problem of excessive output power exceeding the chip threshold setting and burning the chip; at the same time, since the controller does not need to determine the relationship between the output current of the power tube and the first threshold value and the second threshold value, the control logic and design difficulty of the controller can also be reduced.

[0019] In combination with a possible implementation manner of the embodiment of the first aspect, the controller includes: a current limiting control unit, a gain control unit, an overcurrent protection control unit, and a logic judgment unit; the current limiting control unit is connected to the first current detection unit, and the logic judgment unit is respectively connected to the current limiting control unit, the overcurrent protection control unit, the gain control unit and the second current detection unit; the current limiting control unit is used to control the gate drive to limit the output current of the power tube and send a third indication signal when receiving the first indication signal; the gain control unit is used to control the gain of the amplifier; the logic judgment unit is used to determine whether the third indication signal is received, whether the duration of the third indication signal exceeds the second target duration, and whether the second indication signal is received; when the third indication signal is received, the gain control unit is used to control the amplifier to reduce the gain; and if the duration of the third indication signal exceeds the second target duration, or if the second indication signal is received, the overcurrent protection control unit is used to control the gate drive to turn off the power tube.

[0020] In the above embodiment, a controller including a current limiting control unit, a gain control unit, an overcurrent protection control unit, and a logic judgment unit structure is used, so that the various functions of the controller are divided into different control units, so that each unit is responsible for a part of the function. This can not only simplify the structure of each control unit, but also improve the efficiency, so that when the current limiting control unit receives the first indication signal, it immediately controls the gate drive to limit the output current of the power tube to improve the timeliness of the circuit, and sends a third indication signal to the logic judgment unit. The logic judgment unit determines whether the third indication signal is received, whether the duration of the third indication signal exceeds the second target duration, and whether the second indication signal is received. When the third indication signal is received, the gain control unit controls the amplifier to reduce the gain to further reduce the output current of the power tube; and if the duration of the third indication signal exceeds the second target duration, or if the second indication signal is received, the overcurrent protection control unit controls the gate drive to turn off the power tube to protect the power amplifier chip, so as to solve the problem of excessive output power exceeding the chip threshold setting and burning the chip.

[0021] In combination with a possible implementation manner of the first aspect, the logic judgment unit is also used to control the amplifier to increase the gain through the gain control unit if the logic judgment unit has not received the third indication signal for a duration exceeding a third target duration after reducing the gain of the amplifier.

[0022] In the above embodiment, after reducing the gain of the amplifier, if the output current of the power tube is less than the first threshold (the third indication signal is not received), the gain control unit controls the amplifier to increase the gain to restore to the initial gain before the current limiting protection measures are taken, so as to improve the user's listening experience.

[0023] In a second aspect, an embodiment of the present application further provides an electronic device, comprising: an audio amplifier provided in the embodiment of the second aspect above and / or in combination with any possible implementation of the embodiment of the second aspect above.

[0024] In a third aspect, an embodiment of the present application also provides an overcurrent protection method, which is applied to an overcurrent protection circuit in an audio amplifier. The audio amplifier also includes a power amplifier circuit, which includes an amplifier, a gate drive, and a power tube connected in sequence. The method includes: detecting the output current of the power tube; when the output current of the power tube exceeds a first threshold and is not greater than a second threshold, limiting the output current of the power tube.

[0025] In combination with a possible implementation manner of the third aspect, the output current of the power tube is limited, including: taking current limiting protection measures to limit the output current of the power tube, wherein the current limiting protection measures include one of the following: (i) controlling the gate drive to limit the output current of the power tube; (ii) controlling the amplifier to reduce the gain to reduce the output current of the power tube; (iii) controlling the gate drive to limit the output current of the power tube, if the output current of the power tube exceeds the first threshold value after limiting the output current of the power tube and the duration exceeds the first target duration, controlling the amplifier to reduce the gain to reduce the output current of the power tube.

[0026] Other features and advantages of the present application will be described in the following description. The purpose and other advantages of the present application can be realized and obtained through the structures specifically pointed out in the written description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings. The above and other purposes, features and advantages of the present application will be more clearly shown in the drawings.

[0028] Figure 1 A structural schematic diagram of an audio amplifier provided in an embodiment of the present application is shown.

[0029] Figure 2 A schematic diagram showing the connection between a power amplifier circuit and a speaker provided in an embodiment of the present application is shown.

[0030] Figure 3 A connection diagram of a first overcurrent protection circuit and a power amplifier circuit provided in an embodiment of the present application is shown.

[0031] Figure 4 A connection diagram of a second overcurrent protection circuit and a power amplifier circuit provided in an embodiment of the present application is shown.

[0032] Figure 5a A schematic diagram of the structure of a third overcurrent protection circuit and a power amplifier circuit provided in an embodiment of the present application is shown.

[0033] Figure 5b A schematic structural diagram of a fourth overcurrent protection circuit and a power amplifier circuit provided in an embodiment of the present application is shown.

[0034] Figure 6 A schematic diagram showing the principle of a gain control unit provided in an embodiment of the present application controlling the gain of an amplifier.

[0035] Figure 7 A schematic diagram showing the principle of a current limiting control unit provided in an embodiment of the present application controlling a power tube through gate driving is shown.

[0036] Figure 8 A schematic diagram showing the principle of an overcurrent protection control unit provided in an embodiment of the present application controlling a power tube through gate drive.

[0037] Fig. 9 A flow chart of an overcurrent protection method provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following embodiments can be used as examples to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the scope of protection of the present application. It will be appreciated by those skilled in the art that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other.

[0039] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. At the same time, in the description of this application, relational terms such as "first", "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0040] Furthermore, the term "and / or" in this application is merely a term used to describe the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0041] In the description of the embodiments of the present application, unless otherwise clearly specified or limited, the technical term "connection" may refer to a direct connection or an indirect connection through an intermediate medium.

[0042] In the design of power amplifier circuits, in order to prevent the output from shorting each other or shorting to the power supply or ground and other abnormal working conditions, resulting in large currents that burn out the power amplifier chip, overcurrent protection is required. The embodiment of the present application provides an audio amplifier and an overcurrent protection method for an audio amplifier, which can prevent the problem of damage to the power amplifier chip caused by excessive input signal amplitude or short circuit current.

[0043] The overcurrent protection scheme proposed in this application detects that the output current of the power amplifier chip reaches a first threshold value (such as an overcurrent threshold value) and is less than a second threshold value (such as a limit threshold value), and turns on the current limiting protection measure to limit the output current of the power amplifier. If the circuit is in a state of triggering current limiting for a long time, the power amplifier output is turned off to protect the power amplifier chip. The problem of audio interruption caused by the instantaneous high power output of the power amplifier chip can be improved, thereby improving the user's listening experience; at the same time, it can also prevent the continuous high current in the short-circuit scenario from damaging the power amplifier chip to protect the abnormal application of the power amplifier.

[0044] Combine the following Figure 1 The audio amplifier (power amplifier chip with overcurrent protection) provided in the embodiment of the present application is described. The audio amplifier includes: a power amplifier circuit (power amplifier chip) and an overcurrent protection circuit, and the overcurrent protection circuit is connected to the power amplifier circuit. The present application protects the audio amplifier or the power amplifier circuit by adding an overcurrent protection circuit in the audio amplifier.

[0045] The power amplifier circuit includes an amplifier, a gate driver, and a power tube connected in sequence; the gate driver is used to drive the power tube. The amplifier is used to amplify the power of the input signal and use the amplified signal as the input signal of the gate driver. The gate driver drives the power tube according to the amplified signal inputted by itself and adjusts the output current of the power tube.

[0046] The power amplifier circuit may be, but is not limited to, a Class C1ASD power amplifier with a full-bridge output. In a possible implementation, the connection diagram of the power amplifier circuit and the speaker is as follows: Figure 2 As shown, the power amplifier circuit includes a ClASSD circuit, a gate driver, and a power tube. Among them, the ClASSD circuit includes an AMP amplification and a CMP comparison circuit. The gate driver generates a PWM (Pulse Width Modulation) signal for controlling the power tube according to the output signal of the ClASSD circuit, such as PWM_P_UP, PWM_P_DN, PWM_N_UP, and PWM_N_DN. PWM_P_UP and PWM_N_UP are used to control the P tube, and PWM_P_DN and PWM_N_DN are used to control the N tube. In some embodiments, the power amplifier circuit may also include an LC filter circuit for filtering the output current of the power tube and loading the filtered current onto both ends of the load speaker.

[0047] The input differential signals VIP and VIN are amplified by AMP (amplifier) ​​and compared by CMP (comparator) to output PWM (Pulse Width Modulation) signals. The PWM signals are output through the driver stage as differential signals VOP and VON, which are loaded to both ends of the load speaker. If the internal circuit works abnormally, or the output terminals VOP and VON are shorted to each other, shorted to the power supply, or shorted to the ground, the power tube HSD or LSD of the power amplifier circuit will output a large current. If the large current is continuously output, exceeding the limit that the circuit can withstand, the circuit will be damaged or burned, or the electrical performance will fail. Therefore, an overcurrent protection circuit needs to be designed.

[0048] The overcurrent protection circuit is used to detect the output current of the power tube, and when the output current of the power tube exceeds the first threshold value and is not greater than the second threshold value, the output current of the power tube is limited. When the output current of the power tube exceeds the first threshold value and is not greater than the second threshold value, the output current of the power tube can be limited through path 1 and / or path 2. Path 1 is the path connecting the controller to the gate drive, and path 2 is the path connecting the controller to the amplifier.

[0049] In an embodiment of the present application, when the output current of the power tube exceeds the first threshold value and is not greater than the second threshold value, measures can be taken in advance to limit the output current of the power tube before the output current exceeds the second threshold value, and directly shutting down the power tube can be avoided as much as possible. This can improve the problem of audio interruption caused by the instantaneous high power output of the power amplifier chip, thereby improving the user's listening experience.

[0050] For an audio amplifier, if the overcurrent protection is triggered to shut down the amplifier due to excessive output power or other short-term abnormalities, causing a sudden interruption of sound, it will seriously affect the human ear's listening experience. Therefore, the overcurrent protection scheme provided in this application, when it is detected that the output current of the power tube exceeds a certain threshold, the amplifier chip will not suddenly shut down, but will first enter a current limiting state to limit the output current within the range that the chip can withstand, and the amplifier continues to work. In the audio amplifier of this application, in the normal music playback scenario, if a short-term high-power and high-current situation occurs, the amplifier chip can gently skip it instead of shutting down directly, emitting a loud blast or interrupting the sound.

[0051] Among them, the first threshold is smaller than the second threshold. In some embodiments, the first threshold can be regarded as the overcurrent threshold of the circuit (i.e., the threshold that requires current limiting protection), and the second threshold can be regarded as the limit threshold of the circuit (i.e., the limit current value that the circuit can withstand. If the current value exceeds this limit, the circuit is prone to overcurrent and burnout).

[0052] In some possible implementations, the overcurrent protection circuit is also used to control the gate drive to shut down the power tube if the output current of the power tube exceeds the first threshold for a duration exceeding a second target duration (configurable) after the current limiting protection measure is taken. In the embodiment of the present application, after the current limiting protection measure is turned on to limit the output current of the power amplifier, if the circuit is in a state of triggering current limiting for a long time, so that the output current of the power tube exceeds a certain threshold for a long time, the power amplifier output is controlled to be shut down to protect the power amplifier chip.

[0053] In some possible implementations, the overcurrent protection circuit is also used to control the gate drive to turn off the power tube when the output current of the power tube is greater than the second threshold. In the embodiment of the present application, when the output current of the power tube is greater than the second threshold, the gate drive is directly controlled to turn off the power tube to protect the power amplifier chip and solve the problem of excessive output power exceeding the chip threshold setting and burning the chip.

[0054] In one implementation, Figure 3 As shown, the overcurrent protection circuit includes: a current detection device and a controller, and the controller is connected to the current detection device. In this implementation, the controller needs to compare the output current of the power tube with the first threshold and the second threshold.

[0055] The current detection device is used to detect the output current of the power tube and send the detected output current to the controller. The current detection device may include a current detection circuit for detecting the output current of the power tube. It may be a current detection circuit commonly used in the current market for detecting current.

[0056] The controller is used to take current limiting protection measures to limit the output current of the power tube when the output current of the power tube exceeds a first threshold value, and after taking the current limiting protection measures, if the output current of the power tube exceeds the first threshold value for a duration exceeding a second target duration, or if the output current of the power tube is greater than a second threshold value, then control the gate drive to shut down the power tube.

[0057] In one implementation, Figure 4 As shown, the overcurrent protection circuit includes: a first current detection unit, a second current detection unit and a controller, and the controller is connected to the first current detection unit and the second current detection unit respectively. In this embodiment, the controller does not need to compare the output current of the power tube with the first threshold value and the second threshold value.

[0058] The first current detection unit is used to detect the output current of the power tube, and when the output current of the power tube exceeds the first threshold, a first indication signal is output, such as represented by OC_L. In this embodiment, the first current detection unit includes a current detection device and a logic judgment device, and the current detection device is used to detect the output current of the power tube. The logic judgment device is used to judge whether the output current of the power tube exceeds the first threshold, and output the first indication signal when the output current of the power tube exceeds the first threshold.

[0059] The second current detection unit is used to detect the output current of the power tube, and when the output current of the power tube exceeds the second threshold, a second indication signal is output, such as represented by OC_H. In this embodiment, the second current detection unit includes a current detection device and a logic judgment device, and the current detection device is used to detect the output current of the power tube. The logic judgment device is used to judge whether the output current of the power tube exceeds the second threshold, and when the output current of the power tube exceeds the second threshold, the second indication signal is output.

[0060] The controller is used to take current limiting protection measures to limit the output current of the power tube when receiving the first indication signal; and if the duration of receiving the first indication signal after taking the current limiting protection measures exceeds the second target duration, or if the second indication signal is received, control the gate drive to turn off the power tube. The current limiting protection measures used to limit the output current of the power tube include one of the following:

[0061] (i) Control the gate drive to limit the output current of the power tube;

[0062] (ii) controlling the amplifier to reduce the gain to reduce the output current of the power tube;

[0063] (iii) controlling the gate drive to limit the output current of the power tube. If the output current of the power tube exceeds the first threshold value for a duration exceeding a first target duration (configurable) after limiting the output current of the power tube, controlling the amplifier to reduce the gain to reduce the output current of the power tube.

[0064] The above-mentioned current limiting of the output current of the power tube may include: controlling the gate drive to limit the output current of the power tube, or controlling the amplifier to reduce the gain to reduce the output current of the power tube. The current limiting in the present application may be limiting or reducing the current. For example, in the above-mentioned scenario (i), the current limiting may be equal to limiting the current. In the scenario (ii), the current limiting may be considered as reducing the current.

[0065] In some possible implementations, the overcurrent protection circuit is also used to control the amplifier to increase the gain after taking the current limiting protection measure to reduce the amplifier gain, if the duration of the output current of the power tube being less than the first threshold value exceeds the third target duration (configurable), so as to restore to the initial gain before the current limiting protection measure is taken. At this time, the controller is also used to control the amplifier to increase the gain after taking the current limiting protection measure to reduce the amplifier gain, if the duration of the output current of the power tube being less than the first threshold value exceeds the third target duration, so as to restore to the initial gain before the current limiting protection measure is taken.

[0066] The above current limiting protection measure (iii) includes the current limiting protection measures of (i) and (ii). The following example only uses the current limiting protection measure shown in (iii) to limit the output current of the power tube as an example.

[0067] In one implementation, the controller may be a programmable logic device, such as a PLC (Programmable Logic Controller) controller, or other programmable logic devices.

[0068] In one implementation, Figure 5a , Figure 5b As shown, the controller may include: a current limiting control unit, a gain control unit, an overcurrent protection control unit, and a logic judgment unit. In different implementations, the connection modes and functions of the current limiting control unit, the gain control unit, the overcurrent protection control unit, and the logic judgment unit are different.

[0069] It is understood that in some embodiments, Figure 5a , Figure 5b The current limiting control unit, gain control unit, overcurrent protection control unit, and logic judgment unit shown can be combined with each other. For example, the overcurrent protection control unit and the current limiting control unit can be combined into one unit; or, the current limiting control unit, gain control unit, and overcurrent protection control unit can be combined into one unit; or, the gain control unit and the logic judgment unit are combined into one unit, the overcurrent protection control unit and the current limiting control unit can be combined into one unit, and even the above-mentioned current limiting control unit, gain control unit, overcurrent protection control unit, and logic judgment unit can be combined into one unit, etc.

[0070] exist Figure 5aIn the manner shown: the logic judgment unit is connected to the current detection device, the current limiting control unit, the gain control unit, and the overcurrent protection control unit respectively. The logic judgment unit is used to judge the magnitude relationship between the output current of the power tube and the first threshold value and the second threshold value, and when the output current of the power tube exceeds the first threshold value but is less than the second threshold value, the current limiting control unit controls the gate drive to limit the output current of the power tube, and after limiting the output current of the power tube, if the output current of the power tube still exceeds the first threshold value, the gain control unit controls the amplifier to reduce the gain, and after reducing the gain, if the output current of the power tube exceeds the first threshold value for a duration exceeding the second target duration, or if the output current of the power tube is greater than the second threshold value, the overcurrent protection control unit controls the gate drive to turn off the power tube.

[0071] In one possible implementation, the logic judgment unit is also used to control the amplifier to increase the gain through the gain control unit if the output current of the power tube is less than the first threshold value for a duration exceeding a third target duration after the gain of the amplifier is reduced, so as to restore to the initial gain before the current limiting protection measures are taken.

[0072] exist Figure 5b In the manner shown: the first current detection unit is connected to the current limiting control unit, the second current detection unit is connected to the logic judgment unit, and the logic judgment unit is respectively connected to the current limiting control unit, the overcurrent protection control unit, and the gain control unit. The current limiting control unit is used to control the gate drive to limit the output current of the power tube when receiving the first indication signal such as OC_L, and send a third indication signal such as ILMT_FLAG. The logic judgment unit is used to determine whether the third indication signal is received, whether the duration of the third indication signal exceeds the second target duration, and whether the second indication signal is received; when the third indication signal is received, the EN_AGC signal is sent to the gain control unit, and the gain control unit controls the amplifier to reduce the gain; and if the duration of the third indication signal exceeds the second target duration, or if the second indication signal is received, the OCP signal is sent to the overcurrent protection control unit, and the overcurrent protection control unit controls the gate drive to turn off the power tube.

[0073] In one embodiment, when the logic judgment unit receives the third indication signal, the gain control unit controls the amplifier to reduce the gain. In another embodiment, the gain control unit controls the amplifier to reduce the gain only when the duration of receiving the third indication signal exceeds the preset duration but is less than the second target duration.

[0074] In one possible implementation, the logic judgment unit is also used to control the amplifier to increase the gain through the gain control unit after reducing the gain of the amplifier, if the duration for which the logic judgment unit does not receive the third indication signal exceeds the third target duration, so as to restore to the initial gain before the current limiting protection measure is taken.

[0075] The first target duration, the second target duration and the third target duration mentioned above can be achieved by counting.

[0076] The function of the current limiting control unit mentioned above is to control the gate drive, which can be to control the PWM signal, so as to achieve the purpose of limiting the output current of the power tube. Among them, the PWM signal is the driving signal of the gate of the power tube. When controlling the gate drive to limit the output current of the power tube, it can be by changing the duty cycle of the PWM signal to suppress the increase of the output current of the power tube so that it fluctuates within a certain range.

[0077] The function of the overcurrent protection control unit mentioned above is to control the gate drive to shut down the power tube output immediately to protect the power amplifier chip when receiving the overcurrent protection indication signal from the logic control unit. The function of the gain control unit mentioned above is to respond to the control of the logic control unit to perform gain compression or gain release. When the logic control unit determines that gain compression or gain release is required, the gain control unit is controlled to compress or release the gain of the amplifier according to a certain rule, such as how much gain is compressed, how many times the gain is compressed, or the conditions for gain release, which can all be flexibly set. Gain compression will reduce the gain, and gain release will increase the gain.

[0078] In one implementation manner, when the current limiting control unit controls the gate drive to limit the output current of the power tube, and when the overcurrent protection control unit controls the gate drive to shut down the power tube, it may be possible to send a control signal only to the gate drive, and after receiving the control signal sent by the current limiting control unit or the overcurrent protection control unit, the PWM_CTRL in the gate drive changes the duty cycle of PWM_P_UP, PWM_P_DN, PWM_N_UP, and PWM_N_DN, thereby achieving the purpose of limiting or reducing the output current of the power tube and shutting down the power tube.

[0079] The above-mentioned overcurrent protection control unit, current limiting control unit, and gain control unit can be implemented based on logic circuits, and the above-mentioned functions of each control unit can be realized by using logic circuits. In one implementation, the logic control unit can include a counter and a comparator, the counter is used to record the duration, and the comparator is used to compare the duration recorded by the counter with the first target duration, the second target duration, and the third target duration.

[0080] Figure 5a , 5b The working principle of the overcurrent protection circuit shown is:

[0081] The first threshold OC_THR1 is set, and the second threshold OC_THR2 is set. When the power tube current is detected to be greater than OC_THR1, the current limiting control unit will limit the duty cycle of the PWM wave signal output by the gate drive, thereby achieving the purpose of limiting the output current of the power tube; at the same time, if it is detected that the power tube output current is greater than OC_THR1 for a duration exceeding the first target duration, the logic control unit controls the triggering gain control unit to compress the gain of the amplifier and reduce the amplitude of the output signal. The purpose is that when a large instantaneous signal is played, resulting in an output overcurrent, the power amplifier will not directly trigger the OC (Over Current) fault protection (turn off the power tube), but limit the output signal amplitude through current limiting or gain compression, so that the audio signal can be smoothly output without causing a large change in the sense of hearing. However, when the gain compression becomes smaller, if it is still detected that the power tube current is continuously greater than OC_THR1, it can be determined that it is in a short-circuit state at this time, and the overcurrent protection control unit controls the gate drive to turn off the power tube output to protect the power amplifier chip. If the power tube overcurrent is not detected for a long time after the gain compression, the gain control unit is automatically controlled to release the previously compressed gain and restore to the normal channel gain level. Another situation is that when the power tube current increases rapidly, even under the current limiting effect, if it is detected that the power tube current still exceeds OC_THR2, it is judged as an output short circuit, resulting in a large current and possible risk of damage. The overcurrent protection control unit will also control the gate drive to shut down the power tube output and enter the protection state.

[0082] by Figure 2 Taking the power amplifier circuit shown in FIG. 1 as an example, the gain control unit can control the gain of the amplifier by adjusting the input resistance of the amplifier. Generally, the power amplifier gain AV of the amplifier is AV = RF / RIN. The schematic diagram is shown in FIG. Figure 6 As shown, the gain adjustment of the power amplifier can be achieved by adjusting the input resistor RIN, or by adjusting the feedback resistor RF. The input resistor RIN can be a variable resistor, which can include multiple parallel input branches, each of which includes a switch and a resistor in series. The number of resistors connected to the circuit is controlled by controlling the state of the switch, thereby changing the resistance value of the resistor. The gain control unit can control the opening or closing of the switch to change the resistance value of the resistor, thereby changing the gain of the amplifier.

[0083] In a possible implementation, if the gain of the amplifier is adjusted by adjusting the feedback resistor RF of the amplifier, the feedback resistor RF may be a variable resistor, and the variable resistor may include multiple parallel feedback branches, each of which includes a switch and a resistor connected in series, and the number of resistors connected to the circuit is controlled by controlling the state of the switch, thereby changing the resistance value of the resistor. The gain control unit may control the opening or closing of the switch to change the resistance value of the resistor, thereby changing the gain of the amplifier.

[0084] by Figure 2 Taking the power amplifier circuit shown in the figure as an example, the principle of the current limiting control unit controlling the gate drive is as follows Figure 7 As shown, if the power tube HSD or LSD is detected to be overcurrent, the current limiting control unit shortens the corresponding power tube opening time or directly closes it by controlling PWM_CTRL to achieve the purpose of limiting the output current. For example: when the HSD tube at the VOP end is detected to be overcurrent, the PWM_CTRL circuit controls the PWM_P_UP signal to temporarily close the HSD tube to reduce the output current of the HSD tube until the output current is less than the first threshold, then PWM_CTRL outputs the PWM signal normally.

[0085] by Figure 2 Taking the power amplifier circuit shown in the figure as an example, the principle of the overcurrent protection control unit controlling the gate drive is as follows Figure 8 As shown, after the current limiting protection measures are taken, if the power tube HSD or LSD is continuously detected to be overcurrent, or if the output current of the power tube HSD or LSD is detected to be greater than the second threshold, the overcurrent protection control unit turns off the power tube by controlling PWM_CTRL to achieve the protection purpose.

[0086] The embodiment of the present application also provides an overcurrent protection method for the overcurrent protection circuit in the above audio amplifier. Fig. 9 The overcurrent protection method provided in the embodiment of the present application is described.

[0087] S1: Detect the output current of the power tube.

[0088] S2: When the output current of the power tube exceeds the first threshold value and is not greater than the second threshold value, the output current of the power tube is limited.

[0089] In some implementations, limiting the output current of the power tube includes: taking a current limiting protection measure to limit the output current of the power tube, wherein the current limiting protection measure includes one of the following:

[0090] (i) controlling the gate drive to limit the output current of the power tube;

[0091] (ii), controlling the amplifier to reduce the gain so as to reduce the output current of the power tube;

[0092] (iii) controlling the gate drive to limit the output current of the power tube; if the duration for which the output current of the power tube exceeds the first threshold after limiting the output current of the power tube exceeds a first target duration, controlling the amplifier to reduce the gain to reduce the output current of the power tube.

[0093] Among them, controlling the gate drive to limit the output current of the power tube may include reducing the duty cycle of the driving signal of the gate drive to limit the output current of the power tube.

[0094] The overcurrent protection method provided in the embodiment of the present application has the same implementation principle and technical effects as those of the aforementioned audio amplifier embodiment. For the sake of brief description, for matters not mentioned in the method embodiment, reference may be made to the corresponding contents in the aforementioned audio amplifier embodiment.

[0095] The embodiment of the present application also provides an electronic device, which includes the above-mentioned audio amplifier. The electronic device can be various devices or products including an audio amplifier, for example, a game console, a mobile phone, a tablet, a notebook, a vehicle-mounted device, a medical device, a manufacturing device, a communication device, etc.

[0096] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0097] In addition, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0098] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An audio amplifier, characterized in that: include: A power amplifier circuit comprises an amplifier, a gate driver and a power tube connected in sequence, wherein the gate driver is used to drive the power tube; An overcurrent protection circuit is connected to the power amplifier circuit, and is used to detect the output current of the power tube, and when the output current of the power tube exceeds a first threshold value and is not greater than a second threshold value, the output current of the power tube is limited.

2. The audio amplifier according to claim 1, characterized in that: in, The current limiting protection measure used to limit the output current of the power tube includes one of the following: (i) controlling the gate drive to limit the output current of the power tube; (ii), controlling the amplifier to reduce the gain so as to reduce the output current of the power tube; (iii) controlling the gate drive to limit the output current of the power tube; if the duration for which the output current of the power tube exceeds the first threshold after limiting the output current of the power tube exceeds a first target duration, controlling the amplifier to reduce the gain to reduce the output current of the power tube.

3. The audio amplifier according to claim 2, characterized in that: Controlling the gate drive to limit the output current of the power tube includes: The duty cycle of the gate drive signal is reduced to limit the output current of the power tube.

4. The audio amplifier according to any one of claims 1 to 3, characterized in that: The overcurrent protection circuit is also used to control the gate drive to shut down the power tube if the output current of the power tube exceeds the first threshold for a duration exceeding a second target duration after taking current limiting protection measures.

5. The audio amplifier according to claim 4, characterized in that: The overcurrent protection circuit is further used to control the gate drive to turn off the power tube when the output current of the power tube is greater than a second threshold.

6. The audio amplifier according to claim 5, characterized in that: The overcurrent protection circuit comprises: A current detection device, used to detect the output current of the power tube; A controller is connected to the current detection device, and the controller is used to take the current limiting protection measure to limit the output current of the power tube when the output current of the power tube exceeds the first threshold value, and after taking the current limiting protection measure, if the duration of the output current of the power tube exceeding the first threshold value exceeds the second target duration, or if the output current of the power tube is greater than the second threshold value, then control the gate drive to shut down the power tube.

7. The audio amplifier according to claim 5, characterized in that: The overcurrent protection circuit comprises: A first current detection unit, used to detect the output current of the power tube, and output a first indication signal when the output current of the power tube exceeds the first threshold; A second current detection unit, used to detect the output current of the power tube, and output a second indication signal when the output current of the power tube exceeds the second threshold; A controller is connected to the first current detection unit and the second current detection unit, respectively. The controller is used to take the current limiting protection measure to limit the output current of the power tube when the first indication signal is received; and if the duration of the first indication signal received after the current limiting protection measure is taken exceeds the second target duration, or if the second indication signal is received, the gate drive is controlled to shut down the power tube.

8. The audio amplifier according to claim 7, characterized in that: The controller comprises: a current limiting control unit connected to the first current detection unit, and configured to control the gate driver to limit the output current of the power tube and send a third indication signal when receiving the first indication signal; A gain control unit, used to control the gain of the amplifier; An overcurrent protection control unit and a logic judgment unit, wherein the logic judgment unit is respectively connected to the current limiting control unit, the overcurrent protection control unit, the gain control unit and the second current detection unit; the logic judgment unit is used to judge whether the third indication signal is received, whether the duration of the third indication signal exceeds the second target duration and whether the second indication signal is received; when the third indication signal is received, the gain control unit controls the amplifier to reduce the gain; and if the duration of the third indication signal exceeds the second target duration, or if the second indication signal is received, the overcurrent protection control unit controls the gate drive to shut down the power tube.

9. The audio amplifier according to claim 8, characterized in that: The logic judgment unit is further used to control the amplifier to increase the gain through the gain control unit if the duration for which the logic judgment unit does not receive the third indication signal exceeds a third target duration after reducing the gain of the amplifier.

10. An electronic device, characterized in that: include: An audio amplifier as claimed in any one of claims 1 to 9.

11. An overcurrent protection method, characterized in that: An overcurrent protection circuit is applied to an audio amplifier, wherein the audio amplifier further comprises a power amplifier circuit, wherein the power amplifier circuit comprises an amplifier, a gate driver and a power tube connected in sequence, and the method comprises: Detecting the output current of the power tube; When the output current of the power tube exceeds the first threshold value and is not greater than the second threshold value, the output current of the power tube is limited.

12. The method according to claim 11, characterized in that The output current of the power tube is limited, including: A current limiting protection measure is taken to limit the output current of the power tube, wherein the current limiting protection measure includes one of the following: (i) controlling the gate drive to limit the output current of the power tube; (ii), controlling the amplifier to reduce the gain so as to reduce the output current of the power tube; (iii) controlling the gate drive to limit the output current of the power tube; if the duration for which the output current of the power tube exceeds the first threshold after limiting the output current of the power tube exceeds a first target duration, controlling the amplifier to reduce the gain to reduce the output current of the power tube.

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