TWI809710B - Driving circuit of loudspeaker and method for generating current sampling signal of loudspeaker - Google Patents

Abstract

A driving circuit of a loudspeaker includes a periodic signal generation circuit, a signal processing circuit, a class-D amplifier circuit, a current sensing circuit, and a sample and hold circuit. The periodic signal generation circuit is arranged to generate a periodic signal and a control signal. The signal processing circuit is coupled to the periodic signal generation circuit, and is arranged to generate a pre-driving signal. The class-D amplifier circuit is coupled to the signal processing circuit, and is arranged to drive the loudspeaker according to the pre-driving signal. The current sensing circuit is coupled to the class-D amplifier circuit, and is arranged to generate a current sensing signal. The sample and hold circuit is coupled to the periodic signal generation circuit and the current sensing circuit, and is arranged to sample and hold the current sensing signal according to the control signal, to generate a current sampling signal.

Description

Driving circuit applied to loudspeaker and method for generating current sampling signal of loudspeaker

The present invention relates to current sampling, and especially to a driving circuit of a loudspeaker and a related method for generating a current sampling signal of the loudspeaker.

A loudspeaker is a device with a voice coil that moves a diaphragm and converts electrical signals into audio signals. When the temperature of the voice coil is too high or the displacement of the diaphragm is too large, the speaker may be damaged. For a typical class D amplifier, it is used to drive the speaker to achieve the effect of playing music. However, in order to avoid If the speaker is damaged, a smart amplifier may additionally need to detect the condition of the speaker (such as obtaining a signal of the current flowing through the speaker) to determine the operating environment (such as temperature) of the speaker.

For example, a plurality of current sensing resistors (such as two current sensing resistors) can be added to the class D amplifier coupled to the speaker to measure the current flowing through the speaker. One current sensing architecture couples the current sensing resistor across the speaker, and the other current sensing architecture couples the current sensing resistor to ground. Compared with the former, the current sensing architecture that couples the current sensing resistor to ground has a better noise floor. However, if the current sensing resistor is not matching (such as current sensing The resistance value of the resistor is different), this architecture may have poor second-order harmonic distortion (second-order harmonic distortion), in addition, the mismatch of the current sense resistor may cause DC offset (DC offset) problems Therefore, there is a great need for a novel driving circuit with this structure applied to a loudspeaker and a related method for generating a current sampling signal of the loudspeaker.

Therefore, one object of the present invention is to provide a driving circuit applied to a speaker and a related method for generating a current sampling signal of the speaker, so as to solve the above-mentioned problems.

According to an embodiment of the present invention, a driving circuit applied to a speaker is provided. The driving circuit may include a period signal generating circuit, a signal processing circuit, a class D amplifier circuit, a current sensing circuit and a sample and hold circuit. The periodic signal generating circuit can be used to generate a periodic signal and a control signal, wherein the control signal is used to indicate the occurrence timing of a specific extreme value of the periodic signal. The signal processing circuit can be coupled to the periodic signal generating circuit, and can be used to receive a first audio input signal, a second audio input signal and the periodic signal, and to process according to the first audio input signal, the second audio input signal and the periodic signal A pre-drive signal is generated, wherein the second audio input signal is an inverse signal of the first audio input signal. The class D amplifier circuit can be coupled to the signal processing circuit and can be used to drive the speaker according to the pre-drive signal. The current sensing circuit can be coupled to the class D amplifier circuit, and can be used to sense a driving current of the speaker to generate a current sensing signal. The sample and hold circuit can be coupled to the period signal generating circuit and the current sensing circuit, and can be used to sample and hold the current sensing signal according to the control signal, so as to generate a current sampling signal of the speaker.

According to an embodiment of the present invention, a method for generating a current sampling signal of a speaker is provided. The method may include: generating a periodic signal and a control signal, wherein the control signal is used to indicate the occurrence timing of a specific extreme value of the periodic signal; according to a first audio input signal, a second audio input signal and the periodic signal to generate a pre-drive signal, wherein the second audio input signal is an inverse signal of the first audio input signal; a class D amplifier circuit is used to drive the speaker according to the pre-drive signal; a drive current of the speaker is sensed to generate a a current sensing signal; and sampling and holding the current sensing signal according to the control signal to generate a current sampling signal.

According to another embodiment of the present invention, a driving circuit applied to a speaker is provided. The driving circuit may include a period signal generating circuit, a signal processing circuit, a class D amplifier circuit, a current sensing circuit, a logic control circuit and a sample and hold circuit. The periodic signal generating circuit can be used to generate a periodic signal. The signal processing circuit can be coupled to the period signal generating circuit, and can be used to receive a first audio signal, a second audio input signal and the period signal, and generate a signal according to the first audio signal, the second audio input signal and the period signal The pre-drive signal, wherein the second audio input signal is an inverse signal of the first audio input signal. The class D amplifier circuit can be coupled to the signal processing circuit and can be used to drive the speaker according to the pre-drive signal. The current sensing circuit can be coupled to the class D amplifier circuit, and can be used to sense a driving current of the speaker to generate a current sensing signal. The logic control circuit can be coupled to the signal processing circuit, and can be used to generate a control signal according to the pre-drive signal. The sample and hold circuit can be coupled to the current sensing circuit and the logic control circuit, and can be used to sample and hold the current sensing signal according to the control signal to generate a first current sampling signal.

According to another embodiment of the present invention, a method for generating a first current sampling signal of a speaker is provided. The method may include: generating a periodic signal; generating a pre-drive signal according to a first audio signal, a second audio input signal and the periodic signal, wherein the second audio input signal is an inversion of the first audio input signal signal; drive the speaker according to the pre-drive signal by a class D amplifier circuit; sense a driving current of the speaker to generate a current sensing signal; generate a control signal according to the pre-drive signal; and sample and hold according to the control signal The current sensing signal is used to generate a second current sampling signal. In addition, the method may further include: calculating the second current sampling signal to generate the first current sampling signal.

One of the advantages of the present invention is that by sampling and holding the current sensing signal at the time point when the triangular wave signal has a peak value according to the control signal, the second-order harmonic distortion can be improved and the problem of DC bias can be avoided, wherein the peak value of the triangular wave signal is corresponds to a time period, and during this time period, current flows through the speaker and all current sense resistors at the same time. In addition, according to the control signal, the current sensing signal can be sampled and held only during the period when the current flows through the speaker and all the current sensing resistors at the same time, so as to generate a first current sampling signal, and then, the first current sampling signal can be performed The average value is calculated to generate a second current sampling signal of the loudspeaker, so that the second order harmonic distortion can also be improved and the DC bias problem can also be avoided.

FIG. 1 is a schematic diagram of a driving circuit 10 applied to a speaker 11 according to an embodiment of the present invention. The driving circuit 10 may include a periodic signal generating circuit (such as a triangle wave (triangle wave) generating circuit 100), a signal processing circuit 102, a class-D amplifier (class-D amplifier) circuit 104, a current sensing circuit 105, and a sample and hold (sample and hold) circuit 106, it should be noted that the triangular wave generating circuit 100 is only used for illustration, and the present invention is not limited thereto, in fact, any other type of periodic signal (such as a sawtooth wave (sawtooth wave) signal ) will fall into the scope of the present invention. The triangular wave generating circuit 100 can be used to generate the triangular wave signal TRI and the control signal CS, wherein the control signal CS can be used to indicate the occurrence timing of a specific extreme value (eg a peak value) of the triangular wave signal TRI.

The signal processing circuit 102 can be coupled to the triangular wave generating circuit 100, and can be used to receive two audio input signals A_IN and And the triangle wave signal TRI, and according to the two audio input signals A_IN and and the triangular wave signal TRI to generate the pre-drive signal PDRV, wherein the pre-drive signal PDRV includes the first switch pre-drive signal F_SW and the second switch pre-drive signal S_SW, and the audio input signal It is an inverse signal of the audio input signal A_IN (that is, the audio input signal The phase difference with the audio input signal A_IN is equal to 180 degrees). The signal processing circuit 102 can include two comparator circuits 108 and 110 and two pre-driver circuits 112 and 114. The comparator circuit 108 can be coupled to the triangular wave generating circuit 100 and can be used for The audio input signal A_IN is compared with the triangular wave signal TRI to generate a first comparator result signal F_COM. The comparator circuit 110 can be coupled to the triangular wave generating circuit 100 and can be used to compare the audio input signal Comparing with the triangular wave signal TRI to generate the second comparator result signal S_COM, the pre-driver circuit 112 can be coupled to the comparator circuit 108, and can be used to generate the first switch pre-drive signal F_SW according to the first comparator result signal F_COM The pre-driver circuit 114 can be coupled to the comparator circuit 110 and can be used to generate the second switch pre-drive signal S_SW according to the second comparator result signal S_COM.

The loudspeaker 11 is used as a load of the class D amplifier circuit 104. The class D amplifier circuit 104 can be coupled to the signal processing circuit 102 and can be used to switch according to the pre-drive signal PDRV (that is, the first switch pre-drive signal F_SW and the first switch pre-drive signal F_SW and the second Two switch pre-drive signals S_SW) to drive the speaker 11, the class D amplifier circuit 104 may include four switch circuits 116, 118, 120 and 122, the switch circuit 116 has a power coupled to a first reference voltage (such as the power supply voltage VDD) A first end of the switch circuit 118 has a first end coupled to the first reference voltage (such as a power supply voltage VDD), wherein the speaker 11 is coupled to a second end of the switch circuit 116 and a second end of the switch circuit 118 between a second end. The switch circuit 120 has a first end coupled to the second end of the switch circuit 116, and the switch circuit 122 has a first end coupled to the second end of the switch circuit 118. In addition, the first switch pre-drive signal F_SW can be used to One of the switch circuit 116 and the switch circuit 120 is conducted, and the second switch pre-driving signal S_SW can be used to conduct one of the switch circuit 118 and the switch circuit 122 .

It should be noted that the modulation (modulation) method of the class D amplifier circuit 104 is BD modulation, that is to say, there are four directions of current flowing through the speaker 11 in the class D amplifier circuit 104, according to the first switch pre-drive signal F_SW and the second switch pre-drive signal S_SW can obtain the four switch timings a, b, c and d of the four switch circuits 116, 118, 120 and 122, assuming a node between the switch circuit 116 and the switch circuit 120 The voltage of VOUTA is VOUTA, and the voltage of a node between the switch circuit 118 and the switch circuit 122 is VOUTB.

For the positive half cycle of the audio input signal A_IN, in the switching sequence a, the first switch pre-drive signal F_SW can be used to turn on the switch circuit 116, and the second switch pre-drive signal S_SW can be used to turn on the switch circuit. 122 (that is, the voltage VOUTA is a high level, and the voltage VOUTB is a low level); in the switching sequence b, the first switch pre-drive signal F_SW can be used to turn on the switch circuit 116, and the second switch pre-drive signal S_SW can be used to turn on the switch The circuit 118 (that is, the voltage VOUTA and the voltage VOUTB are both at a high level); in the switching sequence c, the first switch pre-drive signal F_SW can be used to turn on the switch circuit 116 , and the second switch pre-drive signal S_SW can be used to turn on the switch circuit 122 (that is, the voltage VOUTA is at a high level, and the voltage VOUTB is at a low level); and in the switching sequence d, the first switch pre-driving signal F_SW can be used to turn on the switch circuit 120, and the second switch pre-driving signal S_SW can be used to turn on the switch The circuit 122 (that is, the voltage VOUTA and the voltage VOUTB are both low).

For the negative half cycle of the audio input signal A_IN, in the switching sequence a, the first switch pre-drive signal F_SW can be used to turn on the switch circuit 120, and the second switch pre-drive signal S_SW can be used to turn on the switch circuit. 118 (that is, the voltage VOUTA is a low level, and the voltage VOUTB is a high level); in the switching sequence b, the first switch pre-drive signal F_SW can be used to turn on the switch circuit 116, and the second switch pre-drive signal S_SW can be used to turn on the switch The circuit 118 (that is, the voltage VOUTA and the voltage VOUTB are both at a high level); in the switching sequence c, the first switch pre-drive signal F_SW can be used to turn on the switch circuit 120 , and the second switch pre-drive signal S_SW can be used to turn on the switch circuit 118 (that is, the voltage VOUTA is at a low level, and the voltage VOUTB is at a high level); and in the switching sequence d, the first switch pre-driving signal F_SW can be used to turn on the switch circuit 120, and the second switch pre-driving signal S_SW can be used to turn on the switch The circuit 122 (that is, the voltage VOUTA and the voltage VOUTB are both low).

The current sensing circuit 105 can be coupled to the class D amplifier circuit 104 and can be used to sense the driving current of the speaker 11 to generate a current sensing signal Isen. The current sensing circuit 105 can include two current sensing resistors 124 and 126 , wherein the current sensing resistor 124 can be coupled between a second terminal of the switch circuit 120 and a second reference voltage (such as ground voltage GND), and the current sensing resistor 126 can be coupled to a first terminal of the switch circuit 122 between the two terminals and the second reference voltage (such as ground voltage GND).

In view of the above, in the switching sequence a, for the positive half cycle of the audio input signal A_IN, the current will sequentially flow through the switch circuit 116, the speaker 11, the switch circuit 122 and the current sensing resistor 126, therefore, the current The sensing signal Isen is generated according to the current sensing resistor 124. For the negative half cycle of the audio input signal A_IN, the current flows through the switch circuit 118, the speaker 11, the switch circuit 120 and the current sensing resistor 124 in sequence, Therefore, the current sensing signal Isen is generated according to the current sensing resistor 124, however, if the current sensing resistor 124 and the current sensing resistor 126 are not matching (matching) (for example, the resistance value of the current sensing resistor 124 and the current sensing If the resistance value of the measuring resistor 126 is different), the current sensing signal Isen generated by the current sensing circuit 105 may be different. In the switching sequence b, for the positive half cycle or the negative half cycle of the audio input signal A_IN, the current will sequentially flow through the switch circuit 116, the speaker 11, and the switch circuit 118 (that is, the current will not flow through the current sensing resistor 124 or the current sensing resistor 126 ), therefore, in the switching sequence b, the current sensing signal Isen is equal to 0. The current direction in the switching sequence c is the same as the current direction in the switching sequence a, and for the sake of brevity, similar content will not be described in detail here.

On the other hand, in the switching sequence d, for the positive half cycle or the negative half cycle of the audio input signal A_IN, the current will sequentially flow through the current sensing resistor 124, the switch circuit 120, the speaker 11, the switch circuit 122 and The current sensing resistor 126 (in Figure 1, the current direction is marked with a dotted line), and the current sensing signal Isen is generated according to the current sensing resistor 124 and the current sensing resistor 126, regardless of the current sensing resistor 124 and the current Whether the sensing resistors 126 match (that is, whether the resistance values of the current sensing resistor 124 and the current sensing resistor 126 are the same), the current sensing signal Isen generated by the current sensing circuit 105 will be the same. In addition, it should be noted that the four switch circuits 116, 118, 120, and 122 have a switching timing d at the timing of the peak value of the triangular wave signal TRI. Therefore, the sampling and holding circuit 106 can be coupled to the triangular wave generating circuit 100 and The current sensing circuit 105 can be used to sample and hold the current sensing signal Isen at the time point when the triangular wave signal TRI has a peak value according to the control signal CS, so as to generate the current sampling signal Isam of the speaker 11. In this way, the current sensing can be improved Second-order harmonic distortion (second-order harmonic distortion) and DC offset (DC offset) caused by the mismatch between the resistor 124 and the current sensing resistor 126 .

FIG. 2 is a schematic diagram of related signals of the driving circuit 10 shown in FIG. 1 according to an embodiment of the present invention. In this embodiment, the triangular wave signal TRI can be combined with the audio input signal A_IN and the corresponding audio input signal The positive half-periods are compared to generate four switching sequences a, b, c, and d, wherein the four switching sequences a, b, c, and d correspond to the four periods A, B, c, and D, respectively. In addition, as shown in FIG. 2, the peak value of the triangular wave signal TRI corresponds to the period D (in the period D, the voltage VOUTA and the voltage VOUTB are both at low levels), and the time point when the triangular wave signal TRI has a peak value can be determined according to the control signal CS. The current sensing signal Isen is sampled and held to generate the current sampling signal Isam. For the sake of brevity, similar content in this embodiment will not be described in detail here.

FIG. 3 is a flowchart of a method for generating a current sampling signal of a loudspeaker according to an embodiment of the present invention. If the same result can be obtained, the steps do not have to be executed sequentially according to the flow shown in FIG. 3. For example, the method shown in FIG. 3 can be implemented by the driving circuit 10 shown in FIG. 1 accomplish.

In step S300 , the triangular wave signal TRI and the control signal CS are generated, wherein the control signal CS is used to indicate the occurrence timing of the peak value of the triangular wave signal TRI.

In step S302, according to the audio input signal A_IN, the audio input signal And the triangular wave signal TRI to generate the pre-drive signal PDRV, where the audio input signal It is an inverse signal of the audio input signal A_IN.

In step S304 , the speaker 11 is driven by the class D amplifier circuit 104 according to the pre-driving signal PDRV.

In step S306 , the driving current of the speaker 11 is sensed to generate a current sensing signal Isen.

In step S308 , the current sensing signal Isen is sampled and held according to the control signal CS to generate the current sampling signal Isam of the speaker 11 .

Since those skilled in the art can easily understand the operation of each step shown in FIG. 3 through the content of the driving circuit 10 shown in FIG. 1 in the above specification, for the sake of brevity, similar content in this embodiment is not omitted here. Repeat.

FIG. 4 is a schematic diagram of a driving circuit 40 applied to a speaker 41 according to another embodiment of the present invention. The drive circuit 40 may include a periodic signal generation circuit (such as a triangular wave generation circuit 400), a signal processing circuit 402, a class D amplifier circuit 404, a logic control circuit 406, a sample and hold circuit 408, and a calculation circuit (such as an average circuit 410), It should be noted that the triangular wave generating circuit 400 and the averaging circuit 410 are only used for illustration, and the present invention is not limited thereto. In fact, any other type of periodic signal (such as a sawtooth wave signal) and any other type of calculation circuit All will fall into the category of the present invention.

The difference between the driving circuit 10 shown in FIG. 1 and the driving circuit 40 shown in FIG. 4 is that the driving circuit 40 further includes a logic control circuit 406 and an averaging circuit 410, and the triangular wave generating circuit 402 is used to generate the triangular wave signal TRI, There is no accompanying signal used to indicate the occurrence timing of a specific extreme value of a periodic signal (such as the peak value of the triangular wave signal TRI). The logic control circuit 406 can be coupled to the signal processing circuit 402, and can be used to generate the control signal CS' according to the pre-drive signal PDRV (ie, the first switch pre-drive signal F_SW and the second switch pre-drive signal S_SW). The sample and hold circuit 408 can be coupled to the current sensing circuit 405 and the logic control circuit 406, and can be used to sample and hold the current sensing signal Isen according to the control signal CS' to generate the first current sampling signal F_Isam. In this embodiment, the first current sampling signal F_Isam is a collection of continuous sampling values of the current sensing signal Isen. The averaging circuit 410 can be coupled to the sample and hold circuit 408 and can be used to average the first current sampling signal F_Isam. The values are calculated to generate the second current sampling signal S_Isam of the speaker 41. For the sake of brevity, the similar content in this embodiment will not be repeated here.

It should be noted that the logic control circuit 406 can be used to generate the control signal CS′ according to the first logic value L1 and the second logic value L2, wherein the first logic value L1 can be generated according to the first switch pre-driving signal F_SW, and can be The second logic value L2 is generated according to the second switch pre-driving signal S_SW. For example, the logic control circuit 406 can be a NOR gate circuit, wherein the NOR gate circuit has a first input terminal coupled to the pre-driver circuit 416 and a first input terminal coupled to the pre-driver circuit 418. Two input terminals and an output terminal coupled to the sample-and-hold circuit 408 are used to receive the first logic value L1 and the second logic value L2 to generate the control signal CS′, but the invention is not limited thereto.

When the switch circuit 420 is turned on according to the first switch pre-drive signal F_SW (that is, the voltage VOUTA is at a high level), the first logic value L1 is equal to 1; and when the switch circuit 424 is turned on according to the first switch pre-drive signal F_SW ( That is, when the voltage VOUTA is at a low level), the first logic value L1 is equal to 0. On the other hand, when the switch circuit 422 is turned on according to the second switch pre-drive signal S_SW (that is, the voltage VOUTB is at a high level), the second logic value L2 is equal to 1; and when the switch circuit 422 is turned on according to the second switch pre-drive signal S_SW When the switch circuit 426 (that is, the voltage VOUTB is at a low level), the second logic value L2 is equal to 0. The control signal CS' can be used to control the sample and hold circuit 408 to turn on the switch circuit 424 and the switch circuit 426 (that is, the voltage VOUTA and the voltage VOUTB) only when the first switch pre-drive signal F_SW and the second switch pre-drive signal S_SW are used to turn on the switch circuit 424 and the switch circuit 426 respectively. Both are low level, and the first logic value L1 and the second logic value L2 are both 0) to sample and hold the current sensing signal Isen, that is to say, only when the control signal CS' is equal to 1 (that is, for When the first logical value L1 (L1=0) and the second logical value L2 (L2=0) perform a NOT-OR (NOR) operation and a result is equal to 1), the current sense is sampled and held by the sample and hold circuit 408 The signal Isen is measured to generate a first current sampling signal F_Isam.

FIG. 5 is a schematic diagram of related signals of the driving circuit 40 shown in FIG. 4 according to an embodiment of the present invention. The triangular wave signal TRI can be connected with the audio input signal A_IN and the corresponding audio input signal The positive half cycle of the first logic value L1 and the second logic value L2 are compared, and the logic combination of the first logic value L1 and the second logic value L2 (ie 10, 11, 10, and 00) corresponds to the four periods A, B, C, and D, respectively. In the period A, the voltage VOUTA is at a high level and the voltage VOUTB is at a low level (that is, the logical combination of the first logic value L1 and the second logic value L2 is 10); in the period B, both the voltage VOUTA and the voltage VOUTB are at a high level level (that is, the logic combination of the first logic value L1 and the second logic value L2 is 11); in period C, the voltage VOUTA is high and the voltage VOUTB is low (that is, the first logic value L1 and the second logic The logic combination of the value L2 is 10); and in the period D, both the voltage VOUTA and the voltage VOUTB are at a low level (that is, the logic combination of the first logic value L1 and the second logic value L2 is 00). In addition, as shown in FIG. 5 , the current sensing signal Isen is only sampled and held in the period D according to the control signal CS′. For the sake of brevity, the similar content in this embodiment will not be repeated here.

FIG. 6 is a flowchart of a method for generating a current sampling signal of a speaker according to another embodiment of the present invention. If the same result can be obtained, the steps do not have to be executed sequentially according to the flow shown in FIG. 6. For example, the method shown in FIG. 6 can be implemented by the driving circuit 40 shown in FIG. 4 accomplish.

In step S600, a triangular wave signal TRI is generated.

In step S602, according to the audio input signal A_IN, the audio input signal And the triangular wave signal TRI to generate the pre-drive signal PDRV, where the audio input signal It is an inverse signal of the audio input signal A_IN.

In step S604 , the speaker 41 is driven by the class D amplifier circuit 404 according to the pre-drive signal PDRV.

In step S606 , the driving current of the speaker 41 is sensed to generate a current sensing signal Isen.

In step S608, the control signal CS' is generated according to the pre-drive signal PDRV.

In step S610, the current sensing signal Isen is sampled and held according to the control signal CS' to generate a first current sampling signal F_Isam.

In step S612 , the second current sampling signal S_Isam of the speaker 41 is generated by performing average calculation on the first current sampling signal F_Isam.

Since those skilled in the art can easily understand the operation of each step shown in FIG. 6 through the contents of the driving circuit 40 shown in FIG. Repeat.

FIG. 7 is a frequency-domain analysis of a sensing voltage signal V_AB, a sampling voltage signal V_ABS generated by the driving circuit 10 shown in FIG. 1 , and a voltage signal VAB_LP generated by a low-pass filter. Assume that the voltage at a node between the switch circuit 120 and the current sensing resistor 124 is the sensing voltage VSENSEA, and the voltage at a node between the switching circuit 122 and the current sensing resistor 126 is the sensing voltage VSENSEB. The sensing voltage signal V_AB is a voltage difference between the sensing voltage VSENSEA and the sensing voltage VSENSEB. In addition, the sensing voltage signal V_AB is matched between the current sensing resistor 124 and the current sensing resistor 126 (ie, the current sensing resistor 124 has the same resistance value as the current sensing resistor 126).

The sampling voltage signal V_ABS can be generated by the driving circuit 10 shown in FIG. 1 and can correspond to the current sampling signal Isam. The current sensing circuit 105 shown in FIG. 1 can be modified to be coupled to a low-pass filter instead of the sample and hold circuit 106, so that the current sensing circuit can be sensed by directly low-pass filtering The signal Isen is used to generate the voltage signal VAB_LP. It should be noted that the sampling voltage signal V_ABS and the voltage signal VAB_LP are mismatched between the current sensing resistor 124 and the current sensing resistor 126 (that is, the resistance value of the current sensing resistor 124 and the resistance value of the current sensing resistor 126 are different. ; For example, the resistance value of the current sensing resistor 124 is 0.1 ohm (ohm), and the resistance value of the current sensing resistor 126 is 0.2 ohm). As shown in FIG. 7, since the current sensing resistor 124 and the current sensing resistor 126 are matched, the sensing voltage signal V_AB has better second-order harmonic distortion at 2000 hertz (Hz). On the other hand, due to the resistance mismatch, the voltage signal VAB_LP has poor second-order harmonic distortion at 2000 Hz, however, despite the resistor mismatch, the sampled voltage signal V_ABS still has good second-order harmonic distortion at 2000 Hz, therefore, this The drive circuit 10 provided by the invention can improve the problem of second-order harmonic distortion. The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

10, 40: Drive circuit 11, 41: Speaker 100, 400: Triangular wave generation circuit 102, 402: Signal processing circuit 104, 404: Class D amplifier circuit 105, 405: Current sensing circuit 106, 408: Sample and hold circuit 108, 110, 412, 414: Comparator circuit 112, 114, 416, 418: Pre-driver circuit 116, 11 8,120,122,420,422,424,426 : switch circuit 124, 126, 428, 430: current sense resistor CS, CS': control signal A_IN, : Audio input signal F_COM: First comparator result signal S_COM: Second comparator result signal F_SW: First switch pre-drive signal S_SW: Second switch pre-drive signal PDRV: Pre-drive signal VDD: Power supply voltage VOUTA, VOUTB: Voltage GND: ground voltage Isen: current sensing signal Isam: current sampling signal A, B, C, D: period S300~S308, S600~S612 406: logic control circuit 410: average circuit L1: first logic value L2: second Logical value F_Isam: first current sampling signal S_Isam: second current sampling signal V_AB: sensing voltage signal VAB_LP: voltage signal V_ABS: sampling voltage signal

FIG. 1 is a schematic diagram of a driving circuit applied to a speaker according to an embodiment of the present invention. FIG. 2 is a schematic diagram of related signals of the driving circuit shown in FIG. 1 according to an embodiment of the present invention. FIG. 3 is a flowchart of a method for generating a current sampling signal of a loudspeaker according to an embodiment of the present invention. FIG. 4 is a schematic diagram of a driving circuit applied to a speaker according to another embodiment of the present invention. FIG. 5 is a schematic diagram of related signals of the driving circuit shown in FIG. 4 according to an embodiment of the present invention. FIG. 6 is a flowchart of a method for generating a current sampling signal of a speaker according to another embodiment of the present invention. FIG. 7 is a frequency domain analysis of a sensing voltage signal, a sampling voltage signal generated by the driving circuit shown in FIG. 1 , and a voltage signal generated by a low-pass filter.

10: Drive circuit

11:Speaker

100: Triangular wave generation circuit

102: Signal processing circuit

104: Class D amplifier circuit

105: Current sensing circuit

106: Sample and hold circuit

108,110: Comparator circuit

112,114: Pre-driver circuit

116,118,120,122: switch circuit

124,126: current sense resistor

CS: control signal

:音頻輸入訊號 A_IN,

: Audio input signal

F_COM: first comparator result signal

S_COM: second comparator result signal

F_SW: The first switch pre-drive signal

S_SW: Second switch pre-drive signal

PDRV: Pre-drive signal

VDD: power supply voltage

VOUTA, VOUTB: voltage

GND: ground voltage

Isen: current sense signal

Isam: current sampling signal

Claims (20)

A driving circuit applied to a loudspeaker, comprising: A periodic signal generating circuit for generating a periodic signal and a control signal, wherein the control signal is used to indicate the occurrence timing of a specific extreme value of the periodic signal; A signal processing circuit, coupled to the periodic signal generating circuit, and used to receive a first audio input signal, a second audio input signal and the periodic signal, and according to the first audio input signal, the second audio input signal and the periodic signal to generate a pre-drive signal, wherein the second audio input signal is an inverse signal of the first audio input signal; a class D amplifier circuit, coupled to the signal processing circuit, and used to drive the speaker according to the pre-drive signal; a current sensing circuit, coupled to the class D amplifier circuit, and used for sensing a driving current of the speaker to generate a current sensing signal; and A sample and hold circuit is coupled to the periodic signal generating circuit and the current sensing circuit, and is used to sample and hold the current sensing signal according to the control signal, so as to generate a current sampling signal of the loudspeaker. The driving circuit described in item 1 of the scope of the patent application, wherein the periodic signal generating circuit is a triangular wave generating circuit, the periodic signal is a triangular wave signal, and the specific extreme value is a peak value of the triangular wave signal. The driving circuit as described in item 2 of the scope of the patent application, wherein the sample and hold circuit is used to sample and hold the current sensing signal at the time point when the triangular wave signal has the peak value. The driving circuit described in item 1 of the scope of the patent application, wherein the pre-driving signal includes a first switch pre-driving signal and a second switch pre-driving signal; the class D amplifier circuit includes: a first switch circuit having a first end coupled to a first reference voltage; A second switch circuit having a first terminal coupled to the first reference voltage, wherein the speaker is coupled between a second terminal of the first switch circuit and a second terminal of the second switch circuit between; a third switch circuit having a first terminal coupled to the second terminal of the first switch circuit; and a fourth switch circuit having a first terminal coupled to the second terminal of the second switch circuit; And the current sensing circuit includes: a first resistor coupled between a second end of the third switch circuit and a second reference voltage; and a second resistor coupled between a second end of the fourth switch circuit and the second reference voltage; Wherein the first switch pre-drive signal is used to turn on one of the first switch circuit and the third switch circuit; and the second switch pre-drive signal is used to turn on the second switch circuit and the fourth switch circuit one of. The driving circuit described in item 4 of the scope of the patent application, wherein at the time point when the periodic signal has the specific extreme value, the third switch is turned on by the first switch pre-drive signal and the second switch pre-drive signal respectively. A switch circuit and the fourth switch circuit. A method for generating a current sampling signal of a loudspeaker, comprising: generating a periodic signal and a control signal, wherein the control signal is used to indicate the occurrence timing of a specific extreme value of the periodic signal; generating a pre-drive signal according to a first audio input signal, a second audio input signal and the periodic signal, wherein the second audio input signal is an inverse signal of the first audio input signal; driving the speaker according to the pre-drive signal by a class D amplifier circuit; sensing a driving current of the speaker to generate a current sensing signal; and Sampling and holding the current sensing signal according to the control signal to generate the current sampling signal. The method described in item 6 of the scope of patent application, wherein the periodic signal is a triangular wave signal, and the specific extreme value is a peak value of the triangular wave signal. The method described in claim 7 of the scope of the patent application, wherein the steps of sampling and holding the current sensing signal according to the control signal include: The current sensing signal is sampled and held at the time point when the triangular wave signal has the peak value. The method described in item 1 of the scope of the patent application, wherein the pre-drive signal includes a first switch pre-drive signal and a second switch pre-drive signal; A first switch circuit with a first terminal, a second switch circuit coupled with a first terminal of the first reference voltage, a first switch circuit coupled with a second terminal of the first switch circuit A third switch circuit at one end and a fourth switch circuit having a first end coupled to a second end of the second switch circuit; the loudspeaker is coupled to the second end of the first switch circuit and between the second terminals of the second switch circuit; a first resistor is coupled between a second terminal of the third switch circuit and a second reference voltage, and a second resistor is coupled between the Between a second terminal of the fourth switch circuit and the second reference voltage; and the step of driving the speaker according to the pre-drive signal includes: turning on one of the first switch circuit and the third switch circuit according to the first switch pre-drive signal; and One of the first switch circuit and the fourth switch circuit is turned on according to the second switch pre-driving signal. The method described in claim 9, wherein the third switch is turned on by the first switch pre-drive signal and the second switch pre-drive signal respectively at the time point when the periodic signal has the specific extreme value circuit and the fourth switch circuit. A driving circuit applied to a loudspeaker, comprising: A periodic signal generating circuit for generating a periodic signal; A signal processing circuit, coupled to the periodic signal generating circuit, and used to receive a first audio signal, a second audio input signal and the periodic signal, and according to the first audio signal, the second audio input signal and the periodic signal to generate a pre-drive signal, wherein the second audio input signal is an inverse signal of the first audio input signal; a class D amplifier circuit, coupled to the signal processing circuit, and used to drive the speaker according to the pre-drive signal; a current sensing circuit, coupled to the class D amplifier circuit, and used for sensing a driving current of the speaker to generate a current sensing signal; a logic control circuit, coupled to the signal processing circuit, and used to generate a control signal according to the pre-drive signal; and A sample and hold circuit, coupled to the current sensing circuit and the logic control circuit, is used to sample and hold the current sensing signal according to the control signal to generate a first current sampling signal. The drive circuit described in item 11 of the scope of the patent application also includes: A calculating circuit is coupled to the sampling and holding circuit and is used for calculating the first current sampling signal to generate a second current sampling signal of the loudspeaker. The driving circuit as described in claim 12 of the patent application, wherein the calculation circuit is an average circuit, and the calculation is an average value calculation. The drive circuit described in item 11 of the scope of the patent application, wherein the pre-drive signal includes a first switch pre-drive signal and a second switch pre-drive signal; the class D amplifier circuit includes: a first switch circuit having a first end coupled to a first reference voltage; A second switch circuit having a first terminal coupled to the first reference voltage, wherein the speaker is coupled between a second terminal of the first switch circuit and a second terminal of the second switch circuit between; a third switch circuit having a first terminal coupled to the second terminal of the first switch circuit; and a fourth switch circuit having a first terminal coupled to the second terminal of the second switch circuit; And the current sensing circuit includes: a first resistor coupled between a second end of the third switch circuit and a second reference voltage; and a second resistor coupled between a second end of the fourth switch circuit and the second reference voltage; Wherein the first switch pre-drive signal is used to turn on one of the first switch circuit and the third switch circuit; and the second switch pre-drive signal is used to turn on the second switch circuit and the fourth switch circuit one of. The drive circuit as described in item 14 of the scope of patent application, wherein the control signal is used to control the sample and hold circuit, so that the sample and hold circuit is only operated by the third switch circuit and the fourth switch circuit respectively The current sensing signal is sampled and held during a period when the first switch pre-drive signal and the second switch pre-drive signal are turned on. A method for generating a first current sampling signal of a loudspeaker, comprising: Generate a periodic signal; generating a pre-drive signal according to a first audio signal, a second audio input signal and the periodic signal, wherein the second audio input signal is an inverse signal of the first audio input signal; driving the speaker according to the pre-drive signal by a class D amplifier circuit; sensing a driving current of the speaker to generate a current sensing signal; generating a control signal according to the pre-drive signal; and Sampling and holding the current sensing signal according to the control signal to generate a second current sampling signal. The method described in item 16 of the scope of the patent application also includes: Calculate the second current sampling signal to generate the first current sampling signal. The method described in item 17 of the scope of the patent application, wherein the calculation is an average value calculation. The method as described in claim 16 of the scope of the patent application, wherein the pre-drive signal includes a first switch pre-drive signal and a second switch pre-drive signal; the class D amplifier circuit includes a device coupled to a first reference voltage A first switch circuit with a first end, a second switch circuit with a first end coupled to the first reference voltage, a first end coupled with a second end of the first switch circuit a third switch circuit and a fourth switch circuit having a first end coupled to a second end of the second switch circuit; the loudspeaker is coupled to the second end of the first switch circuit and the second end of the second switch circuit between the second terminals of the second switch circuit; a first resistor is coupled between a second terminal of the third switch circuit and a second reference voltage, and a second resistor is coupled between the first terminal Between a second terminal of the four-switch circuit and the second reference voltage; and the step of driving the speaker according to the pre-drive signal includes: turning on one of the first switch circuit and the third switch circuit according to the first switch pre-drive signal; and One of the second switch circuit and the fourth switch circuit is turned on according to the second switch pre-driving signal. The method described in claim 19 of the scope of the patent application, wherein the steps of sampling and holding the current sensing signal according to the control signal include: The current sensing signal is sampled and held only during a period when the third switch circuit and the fourth switch circuit are turned on by the first switch pre-drive signal and the second switch pre-drive signal respectively.

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