CN115942197A - Direct current detection circuit, audio amplifier and electronic equipment - Google Patents
Direct current detection circuit, audio amplifier and electronic equipment Download PDFInfo
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Abstract
The invention provides a direct current detection circuit, an audio amplifier and electronic equipment, wherein the direct current detection circuit comprises a processing unit and a detection unit; the processing unit is used for receiving the first pulse width modulation signal and the second pulse width modulation signal, carrying out level transfer and logic operation on the first pulse width modulation signal and the second pulse width modulation signal and outputting a third signal; the detection unit is used for receiving the third signal and detecting whether the duty ratio of the third signal is larger than a first preset threshold value or not so as to determine whether the direct-current voltage in the signal output to the loudspeaker by the audio amplifier exceeds a second preset threshold value or not. Because the third signal is not affected by other parameters except the duty ratio of the first pulse width modulation signal and the second pulse width modulation signal, such as the temperature of the environment where the audio amplifier is located and other parameters such as the modulation mode, the direct current voltage output by the audio amplifier can be detected more accurately, and the loudspeaker is prevented from being overheated or damaged.
Description
Technical Field
The invention relates to the technical field of audio signal processing, in particular to a direct current detection circuit, an audio amplifier and electronic equipment.
Background
A speaker is an electroacoustic transducer, and is widely used in various electronic devices such as smart phones, tablet computers, and smart televisions because it can convert an electric signal into an acoustic signal. The speaker is usually driven by the pwm signal output from the audio amplifier, but since the speaker is very sensitive to dc voltage, if the audio amplifier fails and outputs dc voltage to the speaker, the speaker will overheat or be damaged.
Disclosure of Invention
The invention provides a direct current detection circuit, an audio amplifier and electronic equipment, which are used for detecting direct current voltage output to a loudspeaker by the audio amplifier so as to avoid overheating or damage of the loudspeaker.
In a first aspect, the present invention provides a dc detection circuit, which is applied to an audio amplifier, two output terminals of the audio amplifier respectively output a first pulse width modulation signal and a second pulse width modulation signal, so as to drive a speaker to operate through the first pulse width modulation signal and the second pulse width modulation signal, and the dc detection circuit includes a processing unit and a detection unit; the processing unit is used for receiving the first pulse width modulation signal and the second pulse width modulation signal, performing level shift and logic operation on the first pulse width modulation signal and the second pulse width modulation signal, and outputting a third signal; the detection unit is used for receiving the third signal and detecting whether the duty ratio of the third signal is greater than a first preset threshold value or not so as to determine whether the direct-current voltage in the signal output to the loudspeaker by the audio amplifier exceeds a second preset threshold value or not; the fact that the duty ratio of the third signal is larger than the first preset threshold value indicates that the duty ratio difference value between the first pulse width modulation signal and the second pulse width modulation signal is larger than a third preset threshold value, and the fact that the duty ratio difference value is larger than the third preset threshold value indicates that the direct-current voltage in the signal output by the audio amplifier exceeds a second preset threshold value.
In some optional examples, the processing unit comprises a level shift module and a logic module; the level shifting module is used for receiving the first pulse width modulation signal and the second pulse width modulation signal and shifting the level of the first pulse width modulation signal and the level of the second pulse width modulation signal from a first level value to a second level value, wherein the second level value is smaller than the first level value; the logic module is configured to perform logic operation on the first pulse width modulation signal and the second pulse width modulation signal after the level shift to obtain the third signal.
In some optional examples, the logic module comprises a nand gate; alternatively, the logic module comprises an exclusive or gate.
In some optional examples, the detection unit includes a first switch tube, a second switch tube, a first current source, a second current source, a capacitor and a comparator; the control end of the first switch tube and the control end of the second switch tube are connected with the output end of the processing unit and used for receiving the third signal; the first end of the first switch tube is connected with one end of the first current source, the other end of the first current source is connected with a power supply end, the first end of the second switch tube is connected with one end of the second current source, the other end of the second current source is grounded, the second ends of the first switch tube and the second switch tube are connected with the first end of the capacitor, and the second end of the capacitor is connected with a ground end; one input end of the comparator is connected with the first end of the capacitor, and the other input end of the comparator receives a reference voltage; when the third signal is at a first level, the first switch tube is switched on, the second switch tube is switched off, so that the capacitor is charged, and when the third signal is at a second level, the first switch tube is switched off, the second switch tube is switched on, so that the capacitor is discharged; the comparator is used for detecting the actual voltage of the capacitor, comparing the actual voltage with the reference voltage and outputting a comparison result so as to determine whether the duty ratio of the third signal is greater than a first preset threshold value according to the comparison result.
In some optional examples, the first switch tube is an NMOS transistor, the second switch tube is a PMOS transistor, the first level is a low level, and the second level is a high level; or, the first switch tube is a PMOS transistor, the second switch tube is an NMOS transistor, the first level is a high level, and the second level is a low level.
In some optional examples, an output end of the detection unit is connected to the audio amplifier, and the detection unit is configured to feed back a detection result to the audio amplifier, so that the audio amplifier determines whether to stop operating according to the detection result.
In a second aspect, the present invention provides a dc detection method, applied to an audio amplifier, two output terminals of the audio amplifier respectively output a first pwm signal and a second pwm signal, so as to drive a speaker to operate by the first pwm signal and the second pwm signal, where the dc detection method includes: carrying out level transfer and logic operation on the first pulse width modulation signal and the second pulse width modulation signal to obtain a third signal; detecting whether the duty ratio of the third signal is greater than a first preset threshold value or not so as to determine whether the direct-current voltage in the signal output by the audio amplifier exceeds a second preset threshold value or not; the duty ratio of the third signal is larger than the first preset threshold value, which indicates that the duty ratio difference value between the first pulse width modulation signal and the second pulse width modulation signal is larger than a third preset threshold value, and the duty ratio difference value is larger than the third preset threshold value, which indicates that the direct current voltage in the signal output by the audio amplifier exceeds a second preset threshold value.
In a third aspect, the invention provides an audio amplifier comprising a dc detection circuit as described in any of the above.
In some alternative examples, the audio amplifier comprises a PWM modulated amplifier and the amplifier comprises a power driver stage.
In a fourth aspect, the invention provides an electronic device comprising an audio amplifier as described above.
According to the direct current detection circuit, the audio amplifier and the electronic device, the third signal is obtained by carrying out level transfer and logical operation on the first pulse width modulation signal and the second pulse width modulation signal, and the fact that the duty ratio of the third signal is larger than the first preset threshold value indicates that the duty ratio difference value of the first pulse width modulation signal and the second pulse width modulation signal is larger than the third preset threshold value, and the duty ratio difference value is larger than the third preset threshold value indicates that the direct current voltage in the signal output by the audio amplifier exceeds the second preset threshold value, therefore, whether the direct current voltage in the signal output by the audio amplifier exceeds the second preset threshold value can be determined by detecting whether the duty ratio of the third signal is larger than the first preset threshold value. The third signal is not influenced by other parameters except the duty ratio of the first pulse width modulation signal and the second pulse width modulation signal, such as the temperature of the environment where the audio amplifier is located and other parameters such as a modulation mode, and the problem that the first pulse width modulation signal and the second pulse width modulation signal cannot truly reflect the direct current voltage reaching two ends of the loudspeaker due to the dead time of the output stage of the D-type audio amplifier can be avoided, so that the direct current voltage in the signal output by the audio amplifier can be more accurately detected, and the loudspeaker is prevented from being overheated or damaged.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the background art of the present invention, the drawings required to be used in the embodiments or the background art of the present invention will be described below.
Fig. 1 is a block diagram of an audio amplifier according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an audio amplifier according to an embodiment of the present invention;
FIG. 3 is a timing diagram of a PWM signal according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a connection relationship between a dc detection circuit and an audio amplifier according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a dc detection circuit according to an embodiment of the disclosure;
FIG. 6 is a timing diagram of a third signal according to the disclosure of the present invention;
FIG. 7 is a timing diagram of another third signal according to the disclosure of the present embodiment;
FIG. 8 is a timing diagram of another third signal according to the disclosure of the present embodiment;
FIG. 9 is a schematic structural diagram of another DC detection circuit according to an embodiment of the present invention;
fig. 10 is a flowchart of a dc detection method according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.
As shown in fig. 1, fig. 1 is a block diagram of an audio amplifier according to an embodiment of the present invention, where the audio amplifier is a class D amplifier, and the audio amplifier includes a signal modulation module 10, a driving module 20, a power amplification module 30, and a low-pass filtering module 40.
The signal Modulation module 10 is mainly configured to convert an audio signal of an analog quantity into a Pulse Width Modulation (PWM) signal of a digital quantity. Generally, the signal modulation module 10 is implemented based on a comparator, wherein the audio signal is used as one input signal of the comparator, the other input signal of the comparator is a triangular wave signal with n (n > 1) times the frequency of the audio signal, the comparator compares the audio signal with the triangular wave signal, if the amplitude of the audio signal is higher than that of the triangular wave signal at a certain moment, the comparator outputs a high level, and conversely outputs a low level, the duration of the high level and the low level is determined by the time generated by the difference between the two, and based on this, the continuous audio signal is modulated into a continuous pulse width modulation signal.
The driving module 20 is closely matched with the power amplification module 30, generally, the power amplification module 30 is composed of a high-power MOS transistor, and the driving module 20 controls the on-off state of the MOS transistor in the power amplification module 30 based on the obtained pulse width modulation signal, so that the power amplification module 30 outputs a signal matched with the pulse width modulation signal obtained in the previous step on the premise of realizing power amplification. Since the signal output by the power amplification module 30 includes both the audio signal and the carrier signal, in order to restore the required audio signal, the audio amplifier needs to further include a low pass filter 40 to filter the carrier signal through the low pass filter 40.
As shown in fig. 2, fig. 2 is a schematic diagram of a specific structure of an audio amplifier according to an embodiment of the present invention, where the audio amplifier includes two output terminals, and drives a speaker 50 to operate through two pulse width modulation signals output by the two output terminals, such as a first pulse width modulation signal PWMN and a second pulse width modulation signal PWMP.
As shown in fig. 3, fig. 3 is a timing diagram of a pwm signal according to an embodiment of the disclosure, in a normal case, duty ratios of the first pwm signal PWMN and the second pwm signal PWMP are the same and are both less than 100%, such as both equal to 30%, 40%, 50%, or 60%, however, in a case of an internal failure of the audio amplifier, the duty ratios of the first pwm signal PWMN and the second pwm signal PWMP may be different, at this time, the duty ratios of the first pwm signal PWMN and the second pwm signal PWMP have a certain difference, and the larger the difference is, the larger the amplitude of the dc voltage output to the speaker by the audio amplifier is, and the larger the amplitude of the dc voltage is, which may cause the speaker to overheat or damage.
Based on this, the embodiment of the invention discloses a direct current detection circuit, which is used for detecting whether the difference value of the duty ratios of a first pulse width modulation signal and a second pulse width modulation signal output by an audio amplifier is larger than a preset threshold value or not, so as to send out a fault prompt or control the audio amplifier to stop working according to the detection result, and avoid the overheating or damage of a loudspeaker.
As an optional implementation of the disclosure, an embodiment of the present invention provides a direct current detection circuit, where the direct current detection circuit is applied to an audio amplifier, and is configured to detect whether a difference between duty ratios of a first pulse width modulation signal and a second pulse width modulation signal output by the audio amplifier is greater than a preset threshold.
As shown in fig. 4, fig. 4 is a schematic diagram illustrating a connection relationship between a dc detection circuit and an audio amplifier according to an embodiment of the present invention, two output terminals of the audio amplifier respectively output a first pwm signal PWMN and a second pwm signal PWMP, so as to drive a speaker 50 to operate by the first pwm signal PWMN and the second pwm signal PWMP. It should be understood that fig. 4 only illustrates an audio amplifier, and the structure of the audio amplifier in the embodiment of the present invention is not limited to that shown in fig. 4.
As shown in fig. 5, fig. 5 is a schematic structural diagram of a dc detection circuit according to an embodiment of the present invention, where the dc detection circuit includes a processing unit 51 and a detection unit 52. Wherein, two input terminals of the processing unit 51 are respectively connected with two output terminals of the audio amplifier, and an input terminal of the detecting unit 52 is connected with an output terminal of the processing unit 51.
The processing unit 51 is configured to receive the first pulse width modulation signal PWMN and the second pulse width modulation signal PWMP, perform level shift and logic operation on the first pulse width modulation signal PWMN and the second pulse width modulation signal PWMP, and output a third signal V3. The detecting unit 52 is configured to receive the third signal V3, and detect whether a duty ratio of the third signal is greater than a first preset threshold, so as to determine whether a dc voltage in a signal output by the audio amplifier exceeds a second preset threshold; the fact that the duty ratio of the third signal is larger than a first preset threshold value indicates that the duty ratio difference value of the first pulse width modulation signal and the second pulse width modulation signal is larger than a third preset threshold value, and the fact that the duty ratio difference value is larger than the third preset threshold value indicates that the direct-current voltage in the signal output by the audio amplifier exceeds the second preset threshold value.
In some embodiments of the present invention, the processing unit includes a level shift module for receiving the first and second pwm signals and shifting levels of the first and second pwm signals PWMN and PWMP from a first level value to a second level value, the second level value being smaller than the first level value, such as shifting high levels of the first and second pwm signals from 30V to 5V or 1.8V, wherein low levels of the first and second pwm signals are maintained at 0V, and a logic module. The logic module is used for carrying out logic operation on the first pulse width modulation signal and the second pulse width modulation signal after the level shift to obtain a third signal.
In some embodiments of the present invention, the logic module includes a nand gate, and in other embodiments, the logic module includes an xor gate, but the present invention is not limited thereto, and in other embodiments, the logic module may further include other logic gates or combinations of logic gates, which are not described herein again.
When the logic module is a nand gate, one timing diagram of the third signal is shown in fig. 6, and when the logic module is an xor gate, the other timing diagram of the third signal is shown in fig. 7, after the first pwm signal PWMN and the second pwm signal PWMP are logically operated, the output third signal V3 has a certain duty ratio, and when the difference between the duty ratios of the first pwm signal PWMN and the second pwm signal PWMP is constant, the duty ratio of the third signal V3 is also constant.
However, when the duty ratio difference between the first pwm signal PWMN and the second pwm signal PWMP is large, the duty ratio of the third signal V3 is also large. As shown in fig. 8, fig. 8 is a timing diagram of another third signal disclosed in the embodiment of the present invention, when the duty cycle of the second pwm signal PWMP is increased, the difference between the duty cycles of the first pwm signal PWMN and the second pwm signal PWMP is also increased, and when the logic module is a nand gate, the duty cycle of the third signal V3 is also increased.
Based on this, in the embodiment of the present invention, it is only necessary to determine whether the duty ratio of the third signal V3 is greater than the first preset threshold, that is, it may be determined that the first preset threshold represents that the difference between the duty ratios of the first pulse width modulation signal PWMN and the second pulse width modulation signal PWMP is greater than the third preset threshold, that is, it may be determined whether the dc voltage in the signal output to the speaker by the audio amplifier exceeds the second preset threshold, because the third signal V3 is not affected by other parameters except the duty ratios of the first pulse width modulation signal PWMN and the second pulse width modulation signal PWMP, such as the temperature of the environment where the audio amplifier is located and the modulation mode, and it may also avoid the problem that the first pulse width modulation signal and the second pulse width modulation signal cannot truly reflect the dc voltage reaching the two ends of the speaker because of the dead time of the output stage of the class D audio amplifier, and therefore, the dc voltage output by the audio amplifier may be detected more accurately, and overheating or damage of the speaker may be avoided. The dead time is set to prevent the PMOS transistor and the NMOS transistor of the output stage from being simultaneously turned on.
In some embodiments of the present invention, the detecting unit 52 controls charging and discharging of the capacitor through the third signal V3 to detect the duty ratio of the third signal V3, which is not limited to this, and in other embodiments, the duty ratio of the third signal V3 may also be detected through a timer or a counter, which is not described herein again.
As shown in fig. 9, fig. 9 is a schematic structural diagram of another dc detection circuit disclosed in the embodiment of the present invention, and the detection unit 52 includes a first switch tube K1, a second switch tube K2, a first current source I1, a second current source I2, a capacitor C, and a comparator AP.
The control end of the first switching tube K1 and the control end of the second switching tube K2 are connected to the output end of the processing unit 51, and are configured to receive a third signal V3; the first end of a first switch tube K1 is connected with one end of a first current source I1, the other end of the first current source I1 is connected with a power supply end VDD, the first end of a second switch tube K2 is connected with one end of a second current source I2, the other end of the second current source I2 is grounded, the second end of the first switch tube K1 and the second end of the second switch tube K2 are connected with the first end of a capacitor C, and the second end of the capacitor C is connected with a ground end GND; one input terminal of the comparator AP is connected to the first terminal of the capacitor C, and the other input terminal of the comparator AP receives the reference voltage Vref. It is to be understood that "connected" in the embodiments of the present invention may be directly connected or indirectly connected through other electronic components, and therefore, the detailed description thereof is omitted here.
Under the condition that the third signal V3 is at the first level, the first switch tube K1 is connected, the second switch tube K2 is disconnected, the first current source I1, the first switch tube K1 and the capacitor C form a charging path, so that the capacitor C is charged, under the condition that the third signal V3 is at the second level, the first switch tube K1 is disconnected, the second switch tube K2 is connected, the second switch tube K2, the second current source I2 and the capacitor C form a discharging path, so that the capacitor C is discharged. The comparator AP is configured to detect an actual voltage V1 of the capacitor C, compare the actual voltage V1 with a reference voltage Vref, and output a comparison result Vout, so as to determine whether a duty cycle of the third signal V3 is greater than a first preset threshold according to the comparison result Vout.
In some embodiments of the present invention, the first switch transistor K1 may be an NMOS transistor, the second switch transistor K2 may be a PMOS transistor, the first level may be a low level signal, and the second level may be a high level signal. Of course, the invention is not limited thereto, and in other embodiments, the first switch transistor K1 may be a PMOS transistor, the second switch transistor K2 may be an NMOS transistor, the first level may be a high level signal, and the second level may be a low level signal. Of course, the first switch tube K1 and the second switch tube K2 may also be other switches, for example, the first switch tube K1 and the second switch tube K2 are complementary switches, and the description thereof is omitted here.
The first current source I1 and the second current source I2 can provide stable charging and discharging current for the capacitor C, so that the charging and discharging electric quantity of the capacitor C is only influenced by the duty ratio of the third signal V3, and the accuracy of duty ratio detection of the third signal V3 can be further ensured.
Assuming that the duration of the first level is T1 and the duration of the second level is T2, the duty ratio D = T1/(T1 + T2) of the third signal V3, and the charging duration and the discharging duration of the capacitor C in each charging and discharging cycle are T1 and T2, respectively. Under the condition that the duty ratios of the first pwm signal PWMN and the second pwm signal PWMP are the same, that is, under the condition that the difference between the duty ratios of the first pwm signal PWMN and the second pwm signal PWMP is 0, the duty ratio of the third signal V3 is not changed, so that the actual voltage V1 of the capacitor C is smaller than the capacitor voltage corresponding to the first preset threshold, and the reference voltage Vref is greater than or equal to the capacitor voltage corresponding to the first preset threshold, so that the comparison result of the comparator AP is kept unchanged, such as the comparison result Vout is kept at a high level, however, under the condition that the difference between the duty ratios of the first pwm signal PWMN and the second pwm signal PWMP is increased, the duty ratio of the third signal V3 is also increased, so that the actual voltage V1 of the capacitor C is also increased, and if the actual voltage V1 of the capacitor C is greater than the reference voltage Vref, the comparison result of the comparator AP is inverted, such as the comparison result Vout is inverted to a low level.
Based on this, whether the duty ratio of the third signal V3 is greater than a first preset threshold may be determined according to the comparison result of the comparator AP, and further, whether the duty ratio difference between the first pulse width modulation signal PWMN and the second pulse width modulation signal PWMP is greater than a third preset threshold may be determined according to whether the duty ratio of the third signal V3 is greater than the first preset threshold, and further, whether the dc voltage in the signal output to the speaker by the audio amplifier exceeds a second preset threshold may be determined according to whether the duty ratio difference is greater than the third preset threshold, where if the dc voltage exceeds the second preset threshold, the speaker may be overheated or damaged.
Assuming that the power supply voltage of the audio amplifier is PVDD and the difference between the duty ratios of the first pwm signal PWMN and the second pwm signal PWMP is Δ D, the dc voltage V is DC PVDD Δ D. Wherein, the charging capacity of the capacitor C is (PVDD × Δ D × T)/k, and when the dc voltage is equal to the second preset threshold V2, the discharging capacity of the capacitor C is (V2 × k × T)/k, and it is known from the charge-discharge balance that (PVDD × Δ D × T)/k = (V2 × k × T)/k, and thus, V DC = V2. Wherein, T represents time, and k represents the resistance coefficient of the circuit where the capacitor C is located.
In the embodiment of the present invention, the duty ratio of the third signal V3 is detected by controlling the charging and discharging of the capacitor C by the third signal V3, instead of controlling the charging and discharging of the capacitor C by the first pulse width modulation signal PWMN and/or the second pulse width modulation signal PWMP, so as to detect the duty ratio of the first pulse width modulation signal PWMN and/or the second pulse width modulation signal PWMP, which can avoid the detection result from being influenced by parameters such as the voltage value of the first pulse width modulation signal PWMN and/or the second pulse width modulation signal PWMP, the ambient temperature of the audio amplifier, the modulation mode, and the like, not only can improve the detection accuracy, but also can reduce the ripple of the capacitor C, and further can adopt the capacitor C with a very small capacitance, thereby reducing the area and the cost of the dc detection circuit.
In some embodiments of the present invention, the output end of the comparator AP may be connected to the processor, and the processor controls the alarm to issue a fault alert after detecting that the output signal of the comparator AP changes, so as to remind a worker to control the audio amplifier to stop working, or the processor directly controls the audio amplifier to stop working. Of course, the invention is not limited to this, and in other embodiments, the output terminal of the comparator AP may be directly connected to the audio amplifier to feed back the output signal of the comparator AP to the audio amplifier, so that the audio amplifier determines whether to stop operating according to the output signal.
As an optional implementation of the disclosure, an embodiment of the present invention provides a dc detection method, where the dc detection method is applied to an audio amplifier, and is configured to detect whether a pulse width modulation signal output by the audio amplifier is a dc voltage signal, and referring to fig. 4, two output ends of the audio amplifier respectively output a first pulse width modulation signal and a second pulse width modulation signal, so as to drive a speaker to work through the first pulse width modulation signal and the second pulse width modulation signal, as shown in fig. 10, where fig. 10 is a flowchart of a dc detection method disclosed in the embodiment of the present invention, where the dc detection method includes:
s110: carrying out level transfer and logic operation on the first pulse width modulation signal and the second pulse width modulation signal to obtain a third signal;
s111: and detecting whether the duty ratio of the third signal is greater than a first preset threshold value or not so as to determine whether the direct current voltage in the signal output by the audio amplifier exceeds a second preset threshold value or not.
The fact that the duty ratio of the third signal is larger than a first preset threshold value indicates that the duty ratio difference value of the first pulse width modulation signal and the second pulse width modulation signal is larger than a third preset threshold value, and the fact that the duty ratio difference value is larger than the third preset threshold value indicates that the direct-current voltage in the signal output by the audio amplifier exceeds the second preset threshold value.
Referring to fig. 5, after receiving the first pwm signal PWMN and the second pwm signal PWMP, the processing unit 51 performs level shift and logic operation on the first pwm signal PWMN and the second pwm signal PWMP to obtain and output a third signal V3. The detecting unit 52 receives the third signal V3, detects whether the duty ratio of the third signal V3 is greater than a first preset threshold, and then determines whether the difference between the duty ratios of the first pwm signal PWMN and the second pwm signal PWMP is greater than a third preset threshold according to whether the duty ratio of the third signal V3 is greater than the first preset threshold, and then determines whether the dc voltage in the signal output from the audio amplifier to the speaker exceeds a second preset threshold according to whether the difference between the duty ratios is greater than the third preset threshold, so as to avoid overheating or damage of the speaker.
Referring to fig. 9, after the processing unit 51 outputs the third signal V3, if the third signal V3 is at the first level, the first switch tube K1 is turned on, the second switch tube K2 is turned off, the first switch tube K1 and the capacitor C form a charging path to charge the capacitor C, and if the third signal V3 is at the second level, the first switch tube K1 is turned off, the second switch tube K2 is turned on, the second switch tube K2 and the capacitor C form a discharging path to discharge the capacitor C.
Under the condition that the third signal V3 is at the first level, the first switch tube K1 is connected, the second switch tube K2 is disconnected, the first current source I1, the first switch tube K1 and the capacitor C form a charging path, so that the capacitor C is charged, under the condition that the third signal V3 is at the second level, the first switch tube K1 is disconnected, the second switch tube K2 is connected, the second switch tube K2, the second current source I2 and the capacitor C form a discharging path, so that the capacitor C is discharged. The comparator AP is configured to detect an actual voltage V1 of the capacitor C, compare the actual voltage V1 with a reference voltage Vref, and output a comparison result Vout, so as to determine whether a duty ratio of the third signal V3 is greater than a first preset threshold according to the comparison result Vout.
As an optional implementation of the disclosure, an embodiment of the present invention provides an audio amplifier, where the audio amplifier includes the dc detection circuit provided in any one of the above embodiments. The audio amplifier includes a class D amplifier. Optionally, the audio amplifier comprises a PWM modulated amplifier and the amplifier comprises a power driver stage.
As an alternative implementation of the disclosure, an embodiment of the present invention provides an electronic device, which includes the above audio amplifier.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above examples only express several embodiments of the present specification, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present description, which falls within the scope of protection of the present description. Therefore, the protection scope of the patent in the specification shall be subject to the appended claims.
Claims (10)
1. A direct current detection circuit is applied to an audio amplifier, two output ends of the audio amplifier respectively output a first pulse width modulation signal and a second pulse width modulation signal so as to drive a loudspeaker to work through the first pulse width modulation signal and the second pulse width modulation signal, and the direct current detection circuit comprises a processing unit and a detection unit;
the processing unit is used for receiving the first pulse width modulation signal and the second pulse width modulation signal, performing level shift and logic operation on the first pulse width modulation signal and the second pulse width modulation signal, and outputting a third signal;
the detection unit is used for receiving the third signal and detecting whether the duty ratio of the third signal is greater than a first preset threshold value or not so as to determine whether the direct-current voltage in the signal output by the audio amplifier exceeds a second preset threshold value or not; the duty ratio of the third signal is larger than the first preset threshold value, which indicates that the duty ratio difference value between the first pulse width modulation signal and the second pulse width modulation signal is larger than a third preset threshold value, and the duty ratio difference value is larger than the third preset threshold value, which indicates that the direct current voltage in the signal output by the audio amplifier exceeds a second preset threshold value.
2. The direct current detection circuit of claim 1, wherein the processing unit comprises a level shift module and a logic module;
the level shifting module is used for receiving the first pulse width modulation signal and the second pulse width modulation signal and shifting the level of the first pulse width modulation signal and the level of the second pulse width modulation signal from a first level value to a second level value, wherein the second level value is smaller than the first level value;
the logic module is configured to perform logic operation on the first pulse width modulation signal and the second pulse width modulation signal after the level shift to obtain the third signal.
3. The dc detection circuit of claim 2, wherein the logic module comprises a nand gate; alternatively, the logic module comprises an exclusive or gate.
4. The direct current detection circuit according to claim 1, wherein the detection unit comprises a first switch tube, a second switch tube, a first current source, a second current source, a capacitor and a comparator;
the control end of the first switch tube and the control end of the second switch tube are connected with the output end of the processing unit and used for receiving the third signal; the first end of the first switch tube is connected with one end of the first current source, the other end of the first current source is connected with a power supply end, the first end of the second switch tube is connected with one end of the second current source, the other end of the second current source is grounded, the second ends of the first switch tube and the second switch tube are connected with the first end of the capacitor, and the second end of the capacitor is connected with a ground end; one input end of the comparator is connected with the first end of the capacitor, and the other input end of the comparator receives a reference voltage;
when the third signal is at a first level, the first switch tube is turned on, the second switch tube is turned off, and the capacitor is charged; the comparator is used for detecting the actual voltage of the capacitor, comparing the actual voltage with the reference voltage and outputting a comparison result so as to determine whether the duty ratio of the third signal is greater than a first preset threshold value according to the comparison result.
5. The DC detection circuit of claim 4, wherein the first switch transistor is an NMOS transistor, the second switch transistor is a PMOS transistor, the first level is a low level, and the second level is a high level; alternatively, the first and second electrodes may be,
the first switch tube is a PMOS transistor, the second switch tube is an NMOS transistor, the first level is a high level, and the second level is a low level.
6. The direct current detection circuit according to claim 1, wherein an output terminal of the detection unit is connected to the audio amplifier, and the detection unit is configured to feed back a detection result to the audio amplifier, so that the audio amplifier determines whether to stop operating according to the detection result.
7. A dc detection method applied to an audio amplifier, wherein two output terminals of the audio amplifier respectively output a first pwm signal and a second pwm signal to drive a speaker to operate according to the first pwm signal and the second pwm signal, the dc detection method comprising:
carrying out level shift and logic operation on the first pulse width modulation signal and the second pulse width modulation signal to obtain a third signal;
detecting whether the duty ratio of the third signal is greater than a first preset threshold value or not so as to determine whether the direct-current voltage in the signal output by the audio amplifier exceeds a second preset threshold value or not;
the fact that the duty ratio of the third signal is larger than the first preset threshold value indicates that the duty ratio difference value between the first pulse width modulation signal and the second pulse width modulation signal is larger than a third preset threshold value, and the fact that the duty ratio difference value is larger than the third preset threshold value indicates that the direct-current voltage in the signal output by the audio amplifier exceeds a second preset threshold value.
8. An audio amplifier comprising the direct current detection circuit according to any one of claims 1 to 6.
9. The audio amplifier of claim 8, wherein the audio amplifier comprises a PWM modulated amplifier and the amplifier comprises a power driver stage.
10. An electronic device, characterized in that it comprises an audio amplifier according to claim 8 or 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211699959.XA CN115942197A (en) | 2022-12-28 | 2022-12-28 | Direct current detection circuit, audio amplifier and electronic equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211699959.XA CN115942197A (en) | 2022-12-28 | 2022-12-28 | Direct current detection circuit, audio amplifier and electronic equipment |
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| Publication Number | Publication Date |
|---|---|
| CN115942197A true CN115942197A (en) | 2023-04-07 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211699959.XA Pending CN115942197A (en) | 2022-12-28 | 2022-12-28 | Direct current detection circuit, audio amplifier and electronic equipment |
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| Country | Link |
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| CN (1) | CN115942197A (en) |
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2022
- 2022-12-28 CN CN202211699959.XA patent/CN115942197A/en active Pending
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Address after: Room 402, Building 27, No. 158 Jinfeng Road, Suzhou High tech Zone, Suzhou City, Jiangsu Province, 215163 Applicant after: Shanghai Qinqian Semiconductor Technology Co.,Ltd. Address before: Floor 1-3, No. 24, Lane 315, Fenggu Road, Xuhui District, Shanghai, 200040 Applicant before: Shanghai Xinling Semiconductor Technology Co.,Ltd. |