Common-mode voltage control circuit and D-type power amplifier chip

Abstract

The invention provides a common-mode voltage control circuit and a D-type power amplifier chip, and the common-mode voltage control circuit comprises a voltage detection unit which is used for obtaining voltage information; the resistance providing unit is used for providing resistance values of different gears as source negative feedback resistance; and the logic control unit is connected to the voltage detection unit and the resistance providing unit and used for determining the resistance value of the resistance providing unit based on the voltage information. According to the common-mode voltage control circuit and the D-type power amplifier chip provided by the invention, the resistance providing unit can provide resistance values of different gears as source negative feedback resistance, and by increasing the resistance value of the resistance providing unit, the noise of the common-mode voltage control circuit and the D-type power amplifier chip can be reduced, and the signal-to-noise ratio can be improved.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a common-mode voltage control circuit and a class D power amplifier chip. Background Art

[0002] The input and output stages of a normal-voltage power amplifier are powered by the same supply voltage (VDD). The input and output common-mode voltages are typically designed to be VDD / 2, eliminating common-mode voltage level shift issues and eliminating the need for an additional common-mode voltage control circuit. However, in high-voltage Class-D power amplifier circuit design, to reduce system power consumption, minimize chip area, and minimize circuit design complexity, the pre-integrator loop and post-driver output stage typically utilize different supply voltages. The pre-integrator loop is powered by a relatively low analog supply (AVDD), while the post-driver output stage is powered by a high-voltage power supply (PVDD). To ensure circuit performance, a common-mode voltage control circuit (IB_VCM) is required. However, the output current noise of this common-mode voltage control circuit will enter the Class-D power amplifier, so reducing the noise of this common-mode voltage control circuit is necessary to optimize the noise of the Class-D power amplifier chip. Summary of the Invention

[0003] Based on this, it is necessary to provide a common-mode voltage control circuit and a Class D power amplifier chip to address the problems in the above background technology, which can at least reduce the current noise of the common-mode voltage control circuit and the Class D power amplifier chip and improve the signal-to-noise ratio.

[0004] To achieve the above-mentioned and other related objectives, one aspect of the present application provides a common-mode voltage control circuit for a class D power amplifier, the common-mode voltage control circuit comprising:

[0005] A voltage detection unit, used to obtain voltage information;

[0006] A resistance providing unit, used for providing resistance values ​​of different gears as source negative feedback resistors;

[0007] The logic control unit is connected to the voltage detection unit and the resistance providing unit, and is used to determine the resistance value of the resistance providing unit based on the voltage information.

[0008] In one embodiment, the common mode voltage control circuit further includes:

[0009] An audio signal detection unit, configured to obtain audio signal information;

[0010] The logic control unit is connected to the audio signal detection unit, and is further configured to determine a resistance value of the resistance providing unit based on audio signal information.

[0011] In one embodiment, the resistance providing unit includes a plurality of resistors connected in series and one or more switching devices for short-circuiting part of the resistors to form resistance values ​​of different levels.

[0012] In one embodiment, a branch of the resistance providing unit includes N resistors connected in series and N-1 switching devices, wherein the first ends of the N-1 switching devices are all connected to the first end of the first resistor, and the second ends of the N-1 switching devices are respectively connected to the second ends of the first N-1 resistors connected in series to form N levels of resistance values.

[0013] In one embodiment, the common mode voltage control circuit includes a power-on voltage detection mode,

[0014] When in the power-on voltage detection mode, the logic control unit obtains the power-on power supply voltage and voltage duration. When the voltage duration exceeds a preset time, the power-on power supply voltage is determined, and the resistance value of the resistance providing unit is determined based on the comparison between the power-on power supply voltage and the voltage threshold.

[0015] In one embodiment, the common mode voltage control circuit includes a voltage variation detection mode,

[0016] When in voltage change detection mode, the logic control unit obtains the power supply voltage and the direction of power supply voltage change.

[0017] When the power supply voltage changes from a low voltage to a high voltage, the resistance providing unit switches the resistance value gear without delay based on the power supply voltage exceeding the voltage threshold;

[0018] When the power supply voltage changes from a high voltage to a low voltage, the resistance providing unit delays switching the resistance value gear based on the power supply voltage exceeding the voltage threshold.

[0019] In one embodiment, when the power supply voltage changes from a low voltage to a high voltage, the resistance value provided by the resistance providing unit decreases; when the power supply voltage changes from a high voltage to a low voltage, the resistance value provided by the resistance providing unit increases.

[0020] In one embodiment, the common mode voltage control circuit includes an audio signal detection mode. When in the audio signal detection mode, the logic control unit obtains the audio signal amplitude. Based on the audio signal amplitude being less than the amplitude threshold, the resistance value provided by the resistance providing unit increases.

[0021] In one embodiment, the resistance value of the resistance providing unit is inversely proportional to the noise generated by the common mode voltage control circuit. When the resistance value of the resistance providing unit increases, the noise generated by the common mode voltage control circuit decreases.

[0022] One aspect of the present application provides a class D power amplifier chip, comprising any of the common-mode voltage control circuits described above.

[0023] According to the common-mode voltage control circuit and class D power amplifier chip provided by the present invention, the resistance providing unit can provide resistance values ​​of different gears as the source negative feedback resistor. By increasing the resistance value of the resistance providing unit, the noise of the common-mode voltage control circuit and the class D power amplifier chip can be reduced, and the signal-to-noise ratio can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to better describe and illustrate the embodiments and / or examples of the applications disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered to limit the scope of the disclosed applications, the presently described embodiments and / or examples, and any of the best modes currently understood for these applications.

[0025] Figure 1 A schematic diagram of the structure of a Class D power amplifier provided in the prior art;

[0026] Figure 2 Schematic diagram of the structure of a class D power amplifier chip including a common-mode voltage control circuit provided in one embodiment;

[0027] Figure 3 This is a structural schematic diagram of a resistance providing unit provided in one embodiment;

[0028] Figure 4 1. A diagram showing the corresponding relationship between the power-on power supply voltage, the threshold voltage, and the source negative feedback resistance in a power-on voltage detection mode provided in one embodiment;

[0029] Figure 5 FIG. 1 is a diagram showing the corresponding relationship between the power supply voltage and the threshold voltage, the hysteresis voltage, and the source negative feedback resistance in a voltage change detection mode provided in one embodiment.

[0030] Description of reference numerals:

[0031] 200, common-mode voltage control circuit; 210, voltage detection unit; 220, resistance providing unit; 221, power stage power supply voltage detector; 230, logic control unit; 240, audio signal detection unit; 241, audio signal receiver; 242, audio signal amplitude detector; 300, Class D power amplifier; 310, integrator; 320, pulse width modulator; 330, driver; 400, speaker. DETAILED DESCRIPTION

[0032] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the relevant listed items.

[0034] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present application. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0035] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present application in a schematic manner. Although the illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation, the type, quantity and proportion of each component in actual implementation can be changed at will, and the component layout type may also be more complicated.

[0036] Reference Figure 1 As shown in the figure, in a Class D power amplifier, the front-stage integrator loop is powered by a relatively low analog power supply (AVDD), while the post-driver output stage circuit is powered by a high-voltage power supply (PVDD). To ensure circuit performance, the common-mode voltage is typically designed to be half of the corresponding power supply: AVDD / 2 for the input common-mode voltage and PVDD / 2 for the output common-mode voltage. Consequently, the common-mode voltage at the differential input terminals VIP and VIN is AVDD / 2, and the common-mode voltage at the output terminals OUTP and OUTN is PVDD / 2. The output terminals OUTP and OUTN are fed back to the feedback nodes INP and INN through feedback resistors RF, serving as the differential input signals for the operational amplifier AMP. Therefore, the operational amplifier AMP requires a common-mode voltage control circuit (IB_VCM) in the analog power supply (AVDD) voltage domain to lock the common-mode voltage of its differential input nodes INP and INN to AVDD / 2.

[0037] The common-mode voltage control circuit (IB_VCM) is actually a voltage-controlled current source. It controls the output current by comparing the common-mode voltage at the input of the operational amplifier AMP with the set value VC. This voltage drop across the feedback resistor RF and the input resistor RIN stabilizes the input common-mode voltage of the operational amplifier AMP. The output current noise of the common-mode voltage control circuit (IB_VCM) directly reaches the output through the feedback resistor RF. Therefore, minimizing the noise generated by the common-mode voltage control circuit (IB_VCM) is crucial for optimizing the noise of Class D power amplifiers.

[0038] In view of the above problems, the present invention provides a common mode voltage control circuit 200, such as Figure 2 As shown, for a class D power amplifier 300, the common mode voltage control circuit 200 includes:

[0039] A voltage detection unit 210 is used to obtain voltage information;

[0040] The resistance providing unit 220 is used to provide resistance values ​​of different gears as source negative feedback resistors;

[0041] The logic control unit 230 is connected to the voltage detection unit 210 and the resistance providing unit 220 , and is configured to determine a resistance value of the resistance providing unit based on the voltage information.

[0042] In one embodiment, Figure 2 As shown, the common-mode voltage control circuit 200 also includes: an audio signal detection unit 240 for obtaining audio signal information; further, the logic control unit 230 is connected to the audio signal detection unit 240, and the logic control unit is also used to determine the resistance value of the resistance providing unit based on the audio signal information.

[0043] Exemplarily, the resistance providing unit 220 includes a plurality of resistors connected in series and one or more switching devices for short-circuiting part of the resistors to form resistance values ​​of different levels.

[0044] In one embodiment, the resistance providing unit 220 includes at least two branches, each branch includes at least one MOS transistor, the gate of each branch MOS transistor is connected to the power stage power supply voltage detector 221, and the source of each branch MOS transistor is connected to N series resistors and N-1 switching devices, wherein the first ends of the N-1 switching devices are connected to the first end of the first resistor, and the second ends of the N-1 switching devices are respectively connected to the second ends of the first N-1 series resistors to form N levels of resistance value. Specifically, referring to Figure 3As shown, the resistance providing unit 220 includes a first branch and a second branch arranged in parallel, the gate of the MOS transistor of the first branch is connected to the power stage power supply voltage detector 221, the source of the MOS transistor of the first branch is connected to five resistors (R1, R2, R3, R4 and R5) connected in series, and four switching devices (S1, S2, S3 and S4) are arranged on the first branch. Specifically, the first end of the switching device S1 is connected to the first end of the resistor R1, and the second end of the switching device S1 is connected to the second end of the resistor R1. When the switching device S1 is closed, the resistor R1 is short-circuited; the first end of the switching device S2 is connected to the first end of the resistor R1, and the second end of the switching device S2 is connected to the second end of the resistor R2. When the switch device S2 is closed, the resistors R1 and R2 are short-circuited; the first end of the switching device S3 is connected to the first end of the resistor R1, and the second end of the switching device S3 is connected to the second end of the resistor R3. When the switch device S3 is closed, the resistors R1, R2 and R3 are short-circuited; the first end of the switching device S4 is connected to the first end of the resistor R1, and the second end of the switching device S4 is connected to the second end of the resistor R4. When the switch device S4 is closed, the resistors R1, R2, R3 and R4 are short-circuited. Similarly, the gate of the second branch MOS transistor is connected to the power stage power supply voltage detector 221, the source of the second branch MOS transistor is connected to five resistors connected in series (R6, R7, R8, R9 and R10), and four switching devices (S5, S6, S7 and S8) are provided on the second branch. Specifically, the first end of switch device S5 is connected to the first end of resistor R6, and the second end of switch device S5 is connected to the second end of resistor R6. When switch device S5 is closed, resistor R6 is short-circuited. The first end of switch device S6 is connected to the first end of resistor R6, and the second end of switch device S6 is connected to the second end of resistor R7. When switch device S6 is closed, resistors R6 and R7 are short-circuited. The first end of switch device S7 is connected to the first end of resistor R6, and the second end of switch device S7 is connected to the second end of resistor R8. When switch device S7 is closed, resistors R6, R7, and R8 are short-circuited. The first end of switch device S8 is connected to the first end of resistor R6, and the second end of switch device S8 is connected to the second end of resistor R9. When switch device S8 is closed, resistors R6, R7, R8, and R9 are short-circuited. It should be noted that only a portion of the five resistors on each branch can be short-circuited, for example, one, two, three, or four resistors, but not all five resistors.

[0045] In one embodiment, the resistance values ​​of the resistors in the resistor providing unit 220 can be the same or different. When the resistance values ​​of the resistors are the same, the resistance difference between adjacent gears is the same, and the resistance change is uniform when the gears are continuously switched; when the resistance values ​​of the resistors are different, the resistance difference between adjacent gears is different, and the resistance change is uneven when the gears are continuously switched. In addition, the resistance values ​​of some resistors can also be made the same, for example, the resistance values ​​of the first N-1 resistors (for example, R1, R2, R3, R4) that can be short-circuited by the switching device are the same, and the resistance value of the Nth resistor (for example, R5) that cannot be short-circuited by the switching device is different from the resistance values ​​of the first N-1 resistors (for example, R1, R2, R3, R4). It should be noted that the resistance values ​​of the resistors in the resistor providing unit 220 can be set separately as needed and are not limited here.

[0046] In one embodiment, the resistance value of the resistor providing unit 220 is inversely proportional to the noise generated by the common-mode voltage control circuit 200: when the resistance value of the resistor providing unit increases, the noise generated by the common-mode voltage control circuit 200 decreases; when the resistance value of the resistor providing unit decreases, the noise generated by the common-mode voltage control circuit 200 increases. Therefore, to reduce the noise generated by the common-mode voltage control circuit 200, the resistance value of the resistor providing unit 220 needs to be increased. However, when the source degeneration resistance value is too large, a large voltage drop will be generated across the degeneration resistor when the power supply voltage is high. If this voltage drop forces the current source into the linear region, the common-mode voltage control circuit 200 (IB_VCM) will be unable to lock the common-mode voltage near the reference voltage. Therefore, the source degeneration resistance value should be increased while avoiding the voltage drop that forces the current source into the linear region.

[0047] In one embodiment, referring to Figure 3 As shown, the power stage supply voltage detector 221 detects the voltage value of PVDD and outputs a corresponding bias voltage Vb, which controls the current source to generate corresponding currents IA and IB, locking the common-mode voltage at AVDD / 2. The noise generated by the common-mode voltage control circuit 200 (IB_VCM) is mainly the thermal noise of the current source:

[0048] (Equation 1)

[0049] in, represents the noise of the common mode voltage control circuit 200, represents the transconductance of the current source, and Rs represents the source negative feedback resistor.

[0050] Therefore, to further reduce current source noise, the source degeneration resistor Rs can be increased. However, as the power stage supply voltage increases, the current in the current source increases. Therefore, if the source degeneration resistor Rs is too large, a large voltage drop will be generated across the degeneration resistor when the power supply voltage is high. If this voltage drop forces the current source into the linear region, the common-mode voltage control circuit 200 (IB_VCM) will be unable to lock the common-mode voltage near the reference voltage. Therefore, there is an upper limit to the value of the source degeneration resistor.

[0051] In one embodiment, the voltage detection unit 210 includes but is not limited to a voltage signal receiver, a digital-to-analog converter (DAC), a voltage information detector, etc. The voltage information acquired by the voltage detection unit 210 includes but is not limited to the power-on power supply voltage, voltage duration, power supply voltage, power supply voltage change direction, change duration, etc.

[0052] In one embodiment, the common-mode voltage control circuit 200 includes multiple different modes. Depending on the selected mode, the logic control unit 230 obtains different information and determines the resistance value of the resistance providing unit 220 based on the obtained information. The multiple different modes include, but are not limited to, a power-on voltage detection mode, a voltage change detection mode, and an audio signal detection mode.

[0053] Exemplarily, when the common-mode voltage control circuit 200 is in the power-on voltage detection mode, the logic control unit 230 obtains the power-on power supply voltage and the voltage duration. When the voltage duration exceeds a preset time, the power-on power supply voltage is determined, and the resistance value of the resistance providing unit is determined based on the comparison between the power-on power supply voltage and the voltage threshold.

[0054] In one embodiment, when the common-mode voltage control circuit 200 is in the power-on voltage detection mode, the voltage information obtained by the logic control unit 230 from the voltage detection unit 210 includes but is not limited to the power-on power supply voltage and voltage duration. Since the power supply voltage is unstable during the chip power-on process, there may be a large error in using the voltage at any time obtained by the voltage detection unit 210 as the power-on power supply voltage. Therefore, the voltage detection unit 210 also needs to obtain the voltage duration. When the duration of a certain voltage value exceeds a preset time, the voltage value is used as the power-on power supply voltage V 上电 The preset duration of the voltage can be set as needed, such as 1ms, 2ms or 5ms.

[0055] In one embodiment, referring to Figure 4 As shown, when obtaining the power supply voltage V 上电 After that, the power supply voltage V 上电Compare with the voltage threshold. The number of voltage thresholds can be determined based on the number of resistance value levels. The number of resistance value levels is typically greater than the number of voltage thresholds. When the resistance value includes five levels, a maximum of four voltage thresholds (e.g., V1, V2, V3, and V4) can be set. The four voltage thresholds can divide the voltage into five voltage intervals, and the five voltage intervals correspond one-to-one to the five levels of the resistance providing unit 220. Furthermore, fewer voltage thresholds can be set as needed. For example, when only one voltage threshold is set, the resistance providing unit 220 only provides two levels of resistance.

[0056] Reference Figure 4 As shown, when V 上电 <V1, the logic control unit 230 controls all the switch devices in the resistance providing unit 220 to be turned on, and the resistance providing unit 220 provides the maximum resistance value RA as the source negative feedback resistor. 上电 <V2, the logic control unit 230 controls the switch devices S1 and S5 in the resistance providing unit 220 to be closed, and the resistance providing unit 220 provides the resistance value RB as the source negative feedback resistor. 上电 <V3, the logic control unit 230 controls the switch devices S2 and S6 in the resistance providing unit 220 to be closed, and the resistance providing unit 220 provides a resistance value RC as a source negative feedback resistor. 上电 < V4, the logic control unit 230 controls the switch devices S3 and S7 in the resistance providing unit 220 to be closed, and the resistance providing unit 220 provides the resistance value RD as the source negative feedback resistor. 上电 >V4, the logic control unit 230 controls the switch devices S4 and S8 in the resistance providing unit 220 to be closed, and the resistance providing unit 220 provides the minimum resistance value RE as the source negative feedback resistor.

[0057] According to the common-mode voltage control circuit 200 provided by the present invention, when the power-on power supply voltage is smaller, the resistance value of the source negative feedback resistor provided by the resistance providing unit 220 is larger, which can reduce the noise generated by the common-mode voltage control circuit 200 (IB_VCM) and improve the signal-to-noise ratio.

[0058] Exemplarily, when the common-mode voltage control circuit 200 is in voltage change detection mode, the logic control unit obtains the power supply voltage and the direction of power supply voltage change: when the power supply voltage changes from a low voltage to a high voltage, based on the power supply voltage exceeding a voltage threshold, the resistance providing unit switches the resistance value gear without delay; when the power supply voltage changes from a high voltage to a low voltage, based on the power supply voltage exceeding a voltage threshold, the resistance providing unit switches the resistance value gear with a delay. Furthermore, when the power supply voltage changes from a low voltage to a high voltage, the resistance value provided by the resistance providing unit decreases; when the power supply voltage changes from a high voltage to a low voltage, the resistance value provided by the resistance providing unit increases.

[0059] In one embodiment, when the common-mode voltage control circuit 200 is in voltage change detection mode, the voltage information obtained by the logic control unit 230 from the voltage detection unit 210 includes, but is not limited to, the power supply voltage and the direction of the power supply voltage change. Specifically, the direction of the power supply voltage change includes the power supply voltage changing from a low voltage to a high voltage or from a high voltage to a low voltage. When the power supply voltage is high, if the source degeneration resistance is too large, the current source will enter the linear region, making it impossible for the common-mode voltage control circuit 200 to clamp the input common-mode voltage. Therefore, when the power supply voltage changes from a low voltage to a high voltage, the resistance providing unit 220 should switch the resistance value range without delay to quickly reduce the resistance value and prevent the current source from entering the linear region. Delayless switching means that the resistance value range switching time is less than a preset time, for example, less than 2ms or even less than 1ms. When the power supply voltage changes from a high voltage to a low voltage, the power supply voltage is unstable. If the voltage value is increased rapidly, the power supply voltage may remain high while the source degeneration resistance is also increased to a large value, causing the current source to enter the linear region. Therefore, when the power supply voltage changes from a high voltage to a low voltage, the resistance providing unit 220 should be delayed in switching the resistance value to avoid a rapid increase in the resistance value, thereby preventing the current source from entering the linear region.

[0060] In one embodiment, when the common-mode voltage control circuit 200 is in the voltage change detection mode and the power supply voltage changes from a high voltage to a low voltage, the voltage information obtained by the logic control unit 230 from the voltage detection unit 210 also includes the change duration. The logic control unit 230 obtains the current voltage V from the voltage detection unit 210. 当前 , then the current voltage V 当前 and hysteresis voltage V hys When the current voltage V 当前 Lower than the hysteresis voltage V hys The time (i.e., the duration of the change) exceeds the delay time T dealy After that, the resistance providing unit 220 switches the resistance value gear, so that the resistance providing unit 220 switches the resistance value gear with delay. Delay time T dealyIt can be set as needed, such as 2ms, 3ms, 5ms, etc.

[0061] In one embodiment, referring to Figure 5 As shown, when obtaining the current voltage V 当前 If the power supply voltage changes from low voltage to high voltage, refer to Figure 5 As shown by the red curve on the right, the current voltage V 当前 Compared with the threshold voltage (such as V1, V2, V3 and V4), when the current voltage V 当前 When it is greater than or less than the threshold voltage, it means the current voltage V 当前 Still changes within the 5 voltage intervals divided by the 4 threshold voltages, at this time the resistance value of the resistance providing unit 220 remains unchanged. 当前 When the threshold voltage is reached, that is, the current voltage V 当前 Equal to the threshold voltage, for example V 当前 =V1,V 当前 =V2、V 当前 =V3 or V 当前 =V4, which means the current voltage V 当前 The resistance value of the resistance providing unit 220 changes accordingly. Specifically, V 当前 =V1, the resistance value of the resistance providing unit 220 decreases from RA to RB without delay, V 当前 = V2, the resistance value of the resistance providing unit 220 is reduced from RB to RC without delay, V 当前 = V3, the resistance value of the resistance providing unit 220 decreases from RC to RD without delay, V 当前 =V4, the resistance value of the resistance providing unit 220 decreases from RD to RE without delay.

[0062] In one embodiment, referring to Figure 5 As shown, when obtaining the current voltage V 当前 If the power supply voltage changes from high voltage to low voltage, refer to Figure 5 As shown by the blue curve on the left, the current voltage V 当前 The hysteresis voltage (V hys ) is compared, where the hysteresis voltage is less than the corresponding threshold voltage. 当前 When it is greater than the threshold voltage or less than the hysteresis voltage, it means the current voltage V 当前 Still changes within the 5 voltage intervals divided by the 4 threshold voltages, at this time the resistance value of the resistance providing unit 220 remains unchanged. 当前 When the threshold voltage is reached, that is, the current voltage V当前 Equal to the threshold voltage, for example V 当前 =V1,V 当前 =V2、V 当前 =V3 or V 当前 =V4, which means the current voltage V 当前 The cross-interval change begins, but the resistance value of the resistance providing unit 220 remains unchanged. 当前 Exceeds the hysteresis voltage (i.e. the current voltage V 当前 equal to or less than the hysteresis voltage) and the change duration T 变化 Exceeding the delay time T dealy (i.e., the duration of the change T 变化 Greater than or equal to the delay time T dealy ), the resistance value of the resistance providing unit 220 changes accordingly. Specifically, V 当前 ≤ V hys4 And T 变化 ≥T dealy When the resistance value of the resistance providing unit 220 increases from RE to RD, V 当前 ≤ V hys3 And T 变化 ≥T dealy When the resistance value of the resistance providing unit 220 increases from RD to RC, V 当前 ≤ V hys2 And T 变化 ≥T dealy When the resistance value of the resistance providing unit 220 increases from RC to RB, V 当前 ≤ V hys1 And T 变化 ≥T dealy , the resistance value of the resistance providing unit 220 increases from RB to RA.

[0063] Exemplarily, when the common mode voltage control circuit 200 is in the audio signal detection mode, the logic control unit 230 obtains the audio signal amplitude, and based on the audio signal amplitude being less than the amplitude threshold, the resistance value provided by the resistance providing unit 220 increases.

[0064] In one embodiment, referring to Figure 2As shown, the audio signal detection unit 240 includes, but is not limited to, an audio signal receiver 241, an audio signal amplitude detector 242, and an analog-to-digital converter (ADC). The logic control unit 230 is connected to the audio signal amplitude detector 242. The audio signal acquired by the logic control unit 230 includes, but is not limited to, the audio signal amplitude. When the audio signal amplitude is less than a preset amplitude, it indicates that the output audio signal is relatively low. In this case, the noise generated by the common-mode voltage control circuit 200 significantly interferes with the audio signal. Therefore, it is necessary to increase the resistance value provided by the resistance providing unit 220 to reduce the noise generated by the common-mode voltage control circuit 200. At the same time, the current source should be prevented from entering the linear region. Therefore, the resistance value provided by the resistance providing unit 220 can be increased as much as possible within the upper limit of the selected value of the source negative feedback resistor.

[0065] The present invention also provides a class D power amplifier chip, referring to Figure 2 As shown, the Class D power amplifier chip includes at least a common-mode voltage control circuit 200 and a Class D power amplifier 300. The Class D power amplifier 300 includes an integrator 310, a pulse width modulator (PWM) 320, and a driver 330. A power supply voltage is connected to the driver 330 to power the driver, which is then connected to the speaker 400 to drive the speaker. The resistance providing unit 220 of the common-mode voltage control circuit 200 is connected to the integrator 310 to provide resistance values ​​of different levels. An audio signal receiver 241 is connected to the integrator 310 to provide an audio signal.

[0066] According to the common-mode voltage control circuit and class D power amplifier chip provided by the present invention, the resistance providing unit can provide resistance values ​​of different gears as the source negative feedback resistor. By increasing the resistance value of the resistance providing unit, the noise of the common-mode voltage control circuit and the class D power amplifier chip can be reduced, and the signal-to-noise ratio can be improved.

[0067] Please note that the above embodiments are for illustrative purposes only and are not intended to limit the present application.

[0068] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0069] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements are all within the scope of protection of the present application.

Claims

1. A common mode voltage control circuit, characterized in that: For a class D power amplifier, the common-mode voltage control circuit comprises: A voltage detection unit, used to obtain voltage information; A resistance providing unit, used for providing resistance values ​​of different gears as source negative feedback resistors; A logic control unit is connected to the voltage detection unit and the resistance providing unit, and is used to determine the resistance value of the resistance providing unit based on the voltage information.

2. The common mode voltage control circuit according to claim 1, wherein: Also includes: An audio signal detection unit, configured to obtain audio signal information; The logic control unit is connected to the audio signal detection unit, and the logic control unit is further configured to determine a resistance value of the resistance providing unit based on the audio signal information.

3. The common mode voltage control circuit according to claim 1, wherein: The resistance providing unit includes a plurality of resistors connected in series and one or more switching devices for short-circuiting part of the resistors to form resistance values ​​of different levels.

4. The common mode voltage control circuit according to claim 3, wherein: One branch of the resistance providing unit includes N resistors connected in series and N-1 switching devices, wherein the first ends of the N-1 switching devices are all connected to the first end of the first resistor, and the second ends of the N-1 switching devices are respectively connected to the second ends of the first N-1 resistors connected in series to form N levels of resistance values.

5. The common mode voltage control circuit according to claim 1, wherein: Including power-on voltage detection mode, When in the power-on voltage detection mode, the logic control unit obtains the power-on power supply voltage and voltage duration, and when the voltage duration exceeds a preset time, determines the power-on power supply voltage, and determines the resistance value of the resistance providing unit based on the comparison between the power-on power supply voltage and the voltage threshold.

6. The common mode voltage control circuit according to claim 1, wherein: Including voltage change detection mode, When in voltage change detection mode, the logic control unit obtains the power supply voltage and the direction of power supply voltage change. When the power supply voltage changes from a low voltage to a high voltage, the resistance providing unit switches the resistance value gear without delay based on the power supply voltage exceeding the voltage threshold; When the power supply voltage changes from a high voltage to a low voltage, the resistance providing unit delays switching the resistance value gear based on the power supply voltage exceeding a voltage threshold.

7. The common mode voltage control circuit according to claim 6, wherein: When the power supply voltage changes from a low voltage to a high voltage, the resistance value provided by the resistance providing unit decreases; when the power supply voltage changes from a high voltage to a low voltage, the resistance value provided by the resistance providing unit increases.

8. The common mode voltage control circuit according to claim 2, wherein: Including audio signal detection mode, When in the audio signal detection mode, the logic control unit obtains the audio signal amplitude, and based on the audio signal amplitude being less than the amplitude threshold, the resistance value provided by the resistance providing unit increases.

9. The common mode voltage control circuit according to claim 1, wherein: The resistance value of the resistance providing unit is inversely proportional to the noise generated by the common mode voltage control circuit. When the resistance value of the resistance providing unit increases, the noise generated by the common mode voltage control circuit decreases.

10. A class D power amplifier chip, characterized in that: The common-mode voltage control circuit comprises the common-mode voltage control circuit according to any one of claims 1 to 9.

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