Method and apparatus for modulating signal using multi-class modulation circuitry

Abstract

An example apparatus includes class D amplifier circuitry (130) having a first input, a second input, a third input, and an output, the first input of the class D amplifier circuitry (130) being coupled to the output of the class D amplifier circuitry (130); and class AB amplifier circuitry (140) having a first input, a second input, a third input, and an output, the first input of the class AB amplifier circuitry (140) being coupled to the first input of the class D amplifier circuitry (130) and the output of the class D amplifier circuitry (130), the second and third inputs of the class AB amplifier circuitry (140) are coupled to the second and third inputs of the class D amplifier circuitry (130) and the output of the class AB amplifier circuitry (140).

Description

[0001] This specification generally relates to modulation circuitry, and more specifically, to methods and apparatuses for modulating a signal using multi-class modulation circuitry. BACKGROUND

[0002] Electronic systems utilize amplifier circuitry for a wide range of operations. One example use of amplifier circuitry is signal modulation. In modulation circuitry, amplifier circuitry generates a switching signal to control power stage circuitry that modulates an input signal for supply to a load. By controlling the power stage circuitry, the amplifier circuitry generates a relatively high-power modulated signal based on a relatively low-power input signal. Such modulation circuitry allows electronic systems to generate relatively complex signals from relatively less complex signals. SUMMARY

[0003] For methods and apparatuses for modulating a signal using multi-class modulation circuitry, an example apparatus includes class-D amplifier circuitry having a first input, a second input, a third input, and an output, the first input of the class-D amplifier circuitry coupled to the output of the class-D amplifier circuitry; and class-AB amplifier circuitry having a first input, a second input, a third input, and an output, the first input of the class-AB amplifier circuitry coupled to the first input of the class-D amplifier circuitry and the output of the class-D amplifier circuitry, the second and third inputs of the class-AB amplifier circuitry coupled to the second and third inputs of the class-D amplifier circuitry and the output of the class-AB amplifier circuitry. BRIEF DESCRIPTION OF DRAWINGS

[0004] Figure 1 is a block diagram of an example audio system including example multi-class modulation circuitry implementing a single-inductor (1L) modulation technique to generate a modulated signal.

[0005] Figure 2 is a block diagram of an example of the multi-class modulation circuitry of Figure 1 including example class-D amplifier circuitry and example class-AB amplifier circuitry.

[0006] Figure 3A and 3B is a schematic diagram of an example of the class-D amplifier circuitry of Figure 2 including example feed-forward circuitry.

[0007] Figure 4 is a schematic diagram of an example of the class-AB amplifier circuitry of Figure 2

[0008] Figure 5 is a schematic diagram of an example input stage coupled to​Figure 1 and 2 a multi-class modulation circuit system of FIGS. 1A

[0009] Figure 6 is Figure 1 and 2 a timing diagram of example operations of a multi-class modulation circuit system of FIGS. 1A

[0010] Figure 7 is Figure 2 , 3A and 3B.

[0011] Figure 8 is Figure 1 and 2 a plot of example total harmonic distortion (THD) across multiple frequencies of a multi-class modulation circuit system of FIGS. 1A

[0012] Figure 9 is Figure 1 and 2 a plot of example THD across multiple power values of a multi-class modulation circuit system of FIGS. 1A

[0013] Figure 10 is Figure 1 and 2 a plot of example THD across multiple power values of a multi-class modulation circuit system of FIGS. 1A Figure 3B with and without feed-forward circuitry of FIG. 1A

[0014] Figure 11A and 11B formations representing example operations that can be performed to implement 1L modulation and / or more generally Figure 1 and 2 a flowchart of example operations of a multi-class modulation circuit system of FIGS. 1A

[0015] The same reference numbers or other reference indicators in the drawings represent the same or similar features (functionally and / or structurally). DETAILED DESCRIPTION

[0016] The drawings are not necessarily to scale. In general, the same reference numbers in the drawings indicate the same or similar components or parts throughout the drawings. Although the drawings illustrate areas as having clean lines and boundaries, some or all of these lines and / or boundaries can be idealized. In fact, the boundaries and / or lines can be unobservable, blended, and / or irregular.

[0017] Electronic systems utilize amplifier circuitry for a wide range of operations. One example use of amplifier circuitry is signal modulation. Signal modulation is a process or operations that transforms one or more signals into one or more modulated signals. The one or more modulated signals are modulated to represent the original one or more signals. Modulator circuitry can precondition signals to traverse different environments and / or to be supplied to particular loads. In some examples, modulation circuitry generates modulated signals representing original signals using multiple signal generation techniques. Some modulation circuitry uses amplifier circuitry to generate switching signals that control power stage circuitry. The power stage circuitry generates modulated signals based on the switching signals. The modulated signals can be supplied to a load. By controlling the power stage circuitry, the amplifier circuitry generates relatively high power modulated signals based on relatively low power input signals. Such modulation circuitry allows electronic systems to generate relatively complex signals from relatively less complex signals.

[0018] One example of modulation circuitry utilizes class-AB amplifier circuitry to supply signals to a load. Class-AB amplifier circuitry utilizes sinusoidal waveforms to control transistors of power stage circuitry. In some class-AB amplifier circuitry, a first transistor is driven with a positive amplitude and a second transistor is driven with a negative amplitude. The first and second transistors generate an output of the class-AB amplifier circuitry at a shared terminal. In such examples, the output of the class-AB amplifier circuitry is an amplified version of the input signal. The output of the class-AB amplifier circuitry is a linear output. Such linear outputs have relatively high electromagnetic interference (EMI) immunity and can drive loads without requiring inductive-capacitive (LC) filter circuitry. However, driving the transistors of the class-AB amplifier circuitry to generate a linear output has relatively low power efficiency compared to alternative modulation methods.

[0019] Another example of modulation circuitry utilizes class-D amplifier circuitry to supply signals to a load. Class-D amplifier circuitry utilizes square waveforms to control transistors of power stage circuitry. Class-D amplifier circuitry generates square waveforms by comparing sinusoidal waveforms to triangular waveforms. Such comparisons can be referred to as pulse width modulation (PWM). Class-D amplifier circuitry varies a duty cycle of the square waveforms based on an amplitude of the sinusoidal waveforms. The square waveforms have a first logic state (e.g., logic one, logic high, logic zero, logic low) that enables a first transistor and a second logic state that enables a second transistor. The first and second transistors generate an output of the class-D amplifier circuitry at a shared terminal. LC filter circuitry averages the output of the class-D amplifier circuitry to construct the sinusoidal waveforms. In response to driving the transistors using logic states, class-D amplifier circuitry has relatively high efficiency compared to class-AB amplifier circuitry. However, the square waveform output of class-D amplifier circuitry requires large LC filter circuitry and is more susceptible to EMI.

[0020] In some implementations, such as an audio device, multiple amplifier circuitry is used to drive a load in a differential manner. In some examples, the audio device can include two instances of AB class amplifier circuitry to supply a differential audio signal to a speaker. In such examples, both instances of AB class amplifier circuitry drive multiple transistors in a linear mode of operation. Increasing the number of transistors driven in a linear mode of operation reduces the power efficiency of the device. In another example, the audio device can include two instances of class-D amplifier circuitry to supply a differential audio signal to a speaker. In such examples, each instance of class-D amplifier circuitry requires an inductor to filter a square wave output. This requirement for multiple inductors increases the size of the system-on-chip (SoC) of the circuitry.

[0021] Examples described herein include methods and apparatuses that modulate a signal using multi-class modulation circuitry. In some described examples, the multi-class modulation circuitry implements a single-inductor (1L) modulation technique. The 1L modulation generates an asymmetric differential output using a first amplifier circuitry and a second amplifier circuitry. The first amplifier circuitry is a class-D amplifier circuitry that generates a square wave as a first output by modulating a differential input signal. The class-D amplifier circuitry uses a multi-order modulator circuitry to generate the first output to generate an error signal. The second amplifier circuitry is an AB class amplifier circuitry that generates a second output by modulating the differential input signal in a linear manner. In some described examples, the AB class amplifier circuitry has a relatively high gain that saturates the second output signal. In such examples, in response to the AB class amplifier circuitry operating in a saturated mode of operation, the second signal is non-linear and resembles a square wave. In the saturated mode of operation, the AB class amplifier circuitry clips the second output signal to a supply voltage. In response to such clipping, the output of the AB class amplifier circuitry is non-linear. However, the AB class amplifier circuitry operates in a linear mode of operation for relatively small voltages that occur during transitions between saturated states.

[0022] The class-D amplifier circuitry includes feed-forward circuitry to address this non-ideal linearity of the second output of the AB class amplifier circuitry. In some described examples, the class-D amplifier circuitry combines the second output with the error signal to compensate for the first output of the AB class amplifier circuitry that operates linearly. The class-D amplifier circuitry compares the combined signal to a triangle waveform to generate a square waveform with a varying duty cycle. Advantageously, the multi-class modulation circuitry reduces the overall package size by using a single inductor. Advantageously, the AB class amplifier circuitry reduces the need for large filter circuitry on one output of the multi-class modulation circuitry.

[0023] Figure 1 is a block diagram of an example audio system 100. In Figure 1 example, the audio system 100 includes an example audio source 105, an example multi- class modulation circuitry 110, a first example regulation circuitry 115, a first example resistor 120, a second example resistor 125, an example class-D amplifier circuitry 130, a second example regulation circuitry 135, an example class-AB amplifier circuitry 140, an example filter circuitry 150, an example speaker 160, and an example line output 170. In some examples, such as when the filter circuitry 150 is coupled to the speaker 160, the audio system 100 produces audible noise in response to an audio signal from the audio source 105. In other examples, such as when the filter circuitry 150 is coupled to the line output 170, the audio system 100 supplies an audio signal to an external device to produce audible noise. In such examples, the line output 170 can be an auxiliary (AUX) connector, a driver circuitry, an alternative audio connector, a communication link, etc.

[0024] The audio source 105 is coupled to the amplifier circuitry 130, 140 through the regulation circuitry 115, 135. The audio source 105 supplies an input signal differential pair to the regulation circuitry 115, 135. In Figure 1 example, the input signal differential pair represents an audio signal that generates audible sound when supplied to the speaker 160. The input signal differential pair includes a positive input signal (INP) and a negative input signal (INM). In some examples, the difference between the positive input signal and the negative input signal represents the audio signal. In such examples, the audio source 105 amplifies the audio signal by half a gain to generate the positive input signal and inverts the positive input signal to generate the negative input signal. Although in Figure 1 example, the audio source 105 is shown, in some examples, the audio source 105 can be external circuitry that supplies the differential input signal.

[0025] The multi-class modulation circuitry 110 is coupled to the audio source 105 and the filter circuitry 150. In Figure 1In the example of FIG. 1, multi-class modulation circuitry 110 includes regulation circuitry 115, 135, resistors 120, 125, class-D amplifier circuitry 130, and class-AB amplifier circuitry 140. Multi-class modulation circuitry 110 modulates a differential pair of input signals from audio source 105 using 1L modulation. Multi-class modulation circuitry 110 supplies a differential pair of output signals to filter circuitry 150. The differential pair of output signals has a positive output signal (OUTP) and a negative output signal (OUTM). The positive output signal is the output of class-D amplifier circuitry 130, and the negative output signal is the output of class-AB amplifier circuitry 140. An example of multi-class modulation circuitry 110 is shown in FIG. 3. Figure 2

[0026] First regulation circuitry 115 has first and second terminals coupled to audio source 105 and second regulation circuitry 135. First regulation circuitry 115 has third and fourth terminals coupled to resistors 120, 125 and class-D amplifier circuitry 130. First regulation circuitry 115 receives a differential pair of input signals at the first and second terminals. First regulation circuitry 115 filters the differential pair of input signals. In some examples, first regulation circuitry 115 is a filter circuitry that removes signals having frequencies outside a passband frequency range. In such examples, first regulation circuitry 115 can be one or more instances of low-pass filter circuitry, band-pass filter circuitry, etc. First regulation circuitry 115 supplies the differential pair of input signals to class-D amplifier circuitry 130.

[0027] First regulation circuitry 115 receives a differential pair of output signals of amplifier circuitry 130, 140. Components of first regulation circuitry 115 (shown in FIG. 3 and described below) combine the filtered differential pair of input signals and the differential pair of output signals. First regulation circuitry 115 supplies the combined signals to class-D amplifier circuitry 130. In some examples, the combination of signals by components of first regulation circuitry 115 can be internal to class-D amplifier circuitry 130. In such examples, first regulation circuitry 115 can be removed and / or replaced with alternative circuitry. Figure 1 In the example of FIG. 1, first regulation circuitry 115 is shown. However, multi-class modulation circuitry 110 can be modified to remove and / or include alternative circuitry in place of first regulation circuitry 115. For example, first regulation circuitry 115 can be shown as filter circuitry, replaced with summing resistors, and / or removed altogether.

[0028] ​The first resistor 120 has a first terminal coupled to the first regulation circuitry 115 and the class-D amplifier circuitry 130 and a second terminal coupled to the class-D amplifier circuitry 130 and the filter circuitry 150. The first resistor 120 couples an input of the class-D amplifier circuitry 130 to the positive output signal. The first resistor 120 stabilizes timing of a loop formed between the input and the output of the class-D amplifier circuitry 130. In some examples, the first resistor 120 can be described and / or referred to as a feedback resistor.

[0029] The second resistor 125 has a first terminal coupled to the first regulation circuitry 115 and the class-D amplifier circuitry 130 and a second terminal coupled to the amplifier circuitry 130, 140 and the filter circuitry 150. The second resistor 125 couples an output of the class-AB amplifier circuitry 140 to an input of the amplifier circuitry 130, 140. The second resistor 125 stabilizes timing of a loop formed between the input and the output of the class-AB amplifier circuitry 140. In some examples, the second resistor 125 can be described and / or referred to as a feedback resistor.

[0030] In some examples, one or both of the resistors 120, 125 can be variable resistors. In such examples, the resistances of the resistors 120, 125 are adjusted to be substantially the same. For example, the resistances of the resistors 120, 125 can be within one percent of each other to improve the total harmonic distortion (THD) of the multi-class modulator circuitry 110. Advantageously, reducing the difference between the resistances of the resistors 120, 125 improves the THD of the differential output signal.

[0031] The class-D amplifier circuitry 130 has first and second inputs coupled to the audio source 105 through the regulation circuitry 115. Also, the first and second inputs of the class-D amplifier circuitry 130 are coupled to the outputs of the amplifier circuitry 130, 140 through the resistors 120, 125. The class-D amplifier circuitry 130 has a third input coupled to an output of the class-AB amplifier circuitry 140. The class-D amplifier circuitry 130 receives an input signal differential pair from the audio source 105. In some examples, the class-D amplifier circuitry 130 receives a filtered signal in response to the first regulation circuitry 115 filtering the input signal differential pair. The class-D amplifier circuitry 130 receives an output signal differential pair. In some examples, the class-D amplifier circuitry 130 receives a combined signal containing contributions from both the input signal differential pair and the output signal differential pair. In such examples, the class-D amplifier circuitry 130 also receives the negative output signal.

[0032] Class-D amplifier circuitry 130 amplifies and / or filters the input signal differential pair and the output signal differential pair to reduce noise, increase efficiency, improve total harmonic distortion, etc. In some examples, class-D amplifier circuitry 130 implements a multi-order transfer function with modulation circuitry (shown in Figure 2 and 3B ). In such examples, the modulation circuitry generates the output signal based on a difference between the input signal differential pair and the output signal differential pair. Class-D amplifier circuitry 130 can include circuitry for compensating the positive output signal for linear operation of class-AB amplifier circuitry 140. Such circuitry is shown in Figure 2 , 3A , and 3B. Class-D amplifier circuitry 130 generates a square wave waveform representing the input signal differential pair, feedback of the output signal differential pair, and / or a compensation signal using PWM. Class-D amplifier circuitry 130 generates the positive output signal based on the square wave waveform.

[0033] In some examples, class-D amplifier circuitry 130 uses the square wave waveform to control switching to generate the positive output signal. For example, class-D amplifier circuitry 130 can use first and second switching of FETs (shown in Figure 3A ) to generate the square wave waveform as the positive output signal. In this example, the first switching corresponds to coupling the output of class-D amplifier circuitry 130 to a logic high (e.g., logic one, supply voltage), while the second switching corresponds to coupling the output of class-D amplifier circuitry 130 to a logic low (e.g., logic zero, common potential). In the example of Figure 1 , the positive output signal of class-D amplifier circuitry 130 is a square wave waveform that at least partially represents the input signal differential pair, feedback of the output signal differential pair, and / or a compensation signal. Class-D amplifier circuitry 130 supplies the positive output signal to amplifier circuitry 130, 140 and filter circuitry 150. Examples of class-D amplifier circuitry 130 are shown in Figure 2 , 3A , and 3B.

[0034] The second conditioning circuitry 135 has first and second terminals coupled to the audio source 105 and the first conditioning circuitry 115. The second conditioning circuitry 135 has third and fourth terminals coupled to the class-AB amplifier circuitry 140. The second conditioning circuitry 135 receives an input signal differential pair at the first and second terminals. The second conditioning circuitry 135 filters the input signal differential pair. In some examples, the second conditioning circuitry 135 is a filter circuitry that removes signals having frequencies outside of a passband frequency range. In such examples, the second conditioning circuitry 135 can be a low-pass filter circuitry, a bandpass filter circuitry, etc. The second conditioning circuitry 135 supplies the differential input signal to the class-AB amplifier circuitry 140.

[0035] The class-AB amplifier circuitry 140 has first and second inputs coupled to the audio source 105 through the conditioning circuitry 135. The class-AB amplifier circuitry 140 has a third input coupled to the second resistor 125 and the amplifier circuitry 130, 140. The class-AB amplifier circuitry 140 receives an input signal differential pair from the audio source 105. In some examples, the class-AB amplifier circuitry 140 receives a filtered input signal from the second conditioning circuitry 135. The class-AB amplifier circuitry 140 receives a negative output signal as feedback.

[0036] The class-AB amplifier circuitry 140 amplifies a contribution of the input signal differential pair and / or the output signal differential pair by a gain. The gain of the class-AB amplifier circuitry 140 is a relatively large value. The class-AB amplifier circuitry 140 generates a saturated output signal in response to the relatively large gain. For example, the class-AB amplifier circuitry 140 is capable of generating an output signal having a voltage between the first supply voltage and the second supply voltage. In such examples, the class-AB amplifier circuitry 140 clips the output signal to the first supply voltage for all input voltages that, when amplified by the gain, produce a voltage greater than the first supply voltage. Such operation of the class-AB amplifier circuitry 140 can be referred to as a saturation mode. While in the saturation mode, the negative output signal of the class-AB amplifier circuitry 140 is non-linear. Advantageously, the class-AB amplifier circuitry 140 generates an output signal approximately equal to the first and second supply voltages in response to the relatively high gain. Advantageously, configuring the class-AB amplifier circuitry 140 to reduce a duration of output linearity increases power efficiency.

[0037] However, the class-AB amplifier circuitry 140 can amplify a relatively small voltage (e.g., a voltage near the common potential) with the relatively high gain without clipping the output signal. Such operation of the output of the class-AB amplifier circuitry 140 occurs during transitions between the supply voltages. During transitions between the saturation voltages, the output of the class-AB amplifier circuitry is linear. Thus, the class-AB amplifier circuitry 140 is considered to be in a linear mode of operation. The linear portion of the negative output signal of the class-AB amplifier circuitry 140 when supplied to the power stage circuitry can distort the audio signal. However, the class-AB amplifier circuitry 140 supplies the negative output signal to the class-D amplifier circuitry 130 to compensate the positive output signal for the linear portion of the negative output signal. Advantageously, the class-D amplifier circuitry 130 reduces distortion by compensating the positive output signal for the linear portion of the negative output signal. An example of the class-AB amplifier circuitry 140 is shown in Figure 2 and 4 .

[0038] The filter circuitry 150 is coupled to the resistors 120, 125 and the amplifier circuitry 130, 140. The filter circuitry 150 receives the positive output signal from the class-D amplifier circuitry 130 and the negative output signal from the class-AB amplifier circuitry 140. The filter circuitry 150 filters the output signal differential pair. The filter circuitry 150 supplies the filtered output signal differential pair to the speaker 160 and / or the line output 170. An example of the filter circuitry 150 is shown in Figure 2 .

[0039] In some examples, the speaker 160 is coupled to the filter circuitry 150. The speaker 160 receives the filtered output signal differential pair from the filter circuitry 150. The speaker 160 generates audible noise in response to the filtered output signal differential pair. Alternatively, the filter circuitry 150 can be coupled to the line output 170. In such examples, the filter circuitry 150 supplies the filtered differential output signal to the line output 170 to allow external devices to be coupled to the audio system 100. For example, the line output 170 can be an auxiliary connection adapted to couple an external amplifier to the audio system 100. In this example, the multi-class modulation circuitry 110 can include circuitry to detect an external audio device based on an increase in impedance coupled to the filter circuitry 150. The multi-class modulation circuitry 110 adjusts the modulation of the class-D amplifier circuitry 130 and the gain of the class-AB amplifier circuitry 140 in response to such detection.

[0040] Although in Figure 1In the example, the multi-class modulation circuitry 110 is implemented in the audio system 100, but the multi-class modulation circuitry 110 can be implemented in alternative applications, such as driving non-speaker loads.

[0041] Figure 2 yes Figure 1 A block diagram of an example of a multi-class modulation circuit system 110, which includes Figure 1 The regulating circuit system 115, 135, Figure 1 Resistors 120, 125 and Figure 1 Amplifier circuit systems 130 and 140. In Figure 2 In the example, the multi-class modulation circuit system 110 includes adjustment circuit systems 115 and 135, resistors 120 and 125, amplifier circuit systems 130 and 140, an example modulator circuit system 220, an example combinational circuit system 225, an example feedforward circuit system 230, an example comparator circuit system 235, a first example output stage circuit system 240, an example output detection circuit system 245, an example gain selection circuit system 255, an example amplifier circuit system 260, and a second example output stage circuit system 265. The multi-class modulation circuit system 110 is coupled to... Figure 1 The filter circuit system 150. In Figure 2 In the example, the filter circuit system 150 includes an example inductor 270, a first example capacitor 275, and a second example capacitor 280.

[0042] The Class D amplifier circuit system 130 is coupled to the first regulation circuit system 115, resistors 120 and 125, the Class AB amplifier circuit system 140, and the filter circuit system 150. The Class D amplifier circuit system 130 is adapted to be coupled to the first regulation circuit system 115 via the regulation circuit system 115. Figure 1 Audio source 105. Figure 2 In the example, the Class D amplifier circuit system 130 includes a modulator circuit system 220, a combinational circuit system 225, a feedforward circuit system 230, a comparator circuit system 235, a first output stage circuit system 240, and an output detection circuit system 245. Another example of the Class D amplifier circuit system 130 is... Figure 3A and 3B As shown in the image.

[0043] The Class AB amplifier circuit system 140 is coupled to the Class D amplifier circuit system 130, the second resistor 125, the second adjustment circuit system 135, and the filter circuit system 150. The Class AB amplifier circuit system 140 is adapted to be coupled to the audio source 105 via the second adjustment circuit system 135. Figure 2In the example of FIG. 1, the class-AB amplifier circuitry 140 includes gain selection circuitry 255, amplifier circuitry 260, and second output stage circuitry 265. Another example of class-AB amplifier circuitry 140 is shown in Figure 4

[0044] The modulator circuitry 220 has a first input coupled to the first regulating circuitry 115 and the first resistor 120. The modulator circuitry 220 has a second input coupled to the first regulating circuitry 115 and the second resistor 125. The modulator circuitry 220 has second and third inputs coupled to the output detection circuitry 245. The modulator circuitry has first and second outputs coupled to the combining circuitry 225. The modulator circuitry 220 receives a combined input signal from the first regulating circuitry 115. In Figure 2 In the example of FIG. 1, the combined input signal includes the input signal differential pair and the output signal differential pair of the amplifier circuitry 130, 140. In some examples, the combined input signal is formed as an addition of one of the input signal differential pair and one of the output signal differential pair. For example, the modulator circuitry 220 receives a first combined signal approximately equal to the positive input signal and the positive output signal and a second combined signal approximately equal to the negative input signal and the negative output signal.

[0045] The modulator circuitry 220 modulates the combined differential signal to suppress error between the output signal differential pair and the input signal differential pair. The modulator circuitry 220 generates first and second error signals based on a difference between the differential output signal and the differential input signal. The first error signal represents a difference between the positive input signal and the positive output signal, while the second error signal represents a difference between the negative input signal and the negative output signal. Advantageously, the error signals are differential representations of the difference between the differential input signal and the differential output signal.

[0046] Components of the modulator circuitry 220 (shown in Figure 3B implement a multi-order transfer function that modulates the combined input signal. In some examples, the modulator circuitry 220 implements a relatively high-order transfer function (e.g., a third-order function) to modulate the combined input signal. However, in response to a relatively large load (e.g., a load greater than one hundred ohms (Ω)) coupled to the inductance-capacitance (LC) resonance of the filter circuitry 150 increases the THD of the differential output signal. The modulator circuitry 220 improves the THD of the differential output signal by implementing a relatively low-order transfer function (e.g., from third-order to second-order). In some examples, reducing the order of the transfer function increases stability by suppressing the LC resonance at relatively high frequencies. In such examples, the frequency at which the LC resonance is suppressed stabilizes the error signals of the modulator circuitry 220. In Figure 2 ​In some examples, the order of modulator circuitry 220 can be configured or adjusted by output detection circuitry 245. Advantageously, modulator circuitry 220 can be modified to modulate the combined input signal based on the resistance of the load coupled to filter circuitry 150.

[0047] Combination circuitry 225 is coupled to a plurality of inputs of modulator circuitry 220. Combination circuitry 225 has first and second outputs coupled to feedforward circuitry 230. Combination circuitry 225 receives error signals from modulator circuitry 220. Combination circuitry 225 determines a difference between the error signals from modulator circuitry 220. Combination circuitry 225 combines the error signals from modulator circuitry 220. Combination circuitry 225 supplies the combined error signal to feedforward circuitry 230.

[0048] Feedforward circuitry 230 has first and second inputs coupled to combination circuitry 225 and a third input coupled to filter circuitry 150, second resistor 125, gain selection circuitry 255, and second output stage circuitry 265. Feedforward circuitry 230 has an output coupled to comparison circuitry 235. Feedforward circuitry 230 receives the combined error signal from combination circuitry 225. Feedforward circuitry 230 receives the negative output signal from second output stage circuitry 265. Feedforward circuitry divides the negative output signal by a value greater than one to supply a signal that approximates the logic level of comparison circuitry 235. Feedforward circuitry 230 generates a single-ended error signal by combining the combined error signal and the divided negative output signal. In some examples, combining the combined error signal and the divided negative output signal produces a combined error signal that includes a non-linearity of the negative output signal. Advantageously, feedforward circuitry 230 addresses the non-ideal linearity of the negative output signal by offsetting the combined error signal by the negative output signal. Feedforward circuitry 230 supplies the combined error signal to comparison circuitry 235.

[0049] In some examples, feedforward circuitry 230 includes circuitry to adjust the common mode reference of the combined error signal. In such examples, feedforward circuitry 230 can also include circuitry to adjust the logic level of the single-ended error signal to the logic level of comparison circuitry 235. Such examples of feedforward circuitry 230 are shown in Figure 3B Advantageously, feedforward circuitry 230 can offset the combined signal and / or the divided negative output signal to adjust the single-ended error signal. Feedforward circuitry 230 supplies the single-ended error signal to comparison circuitry 235.

[0050] The comparison circuitry 235 has an input coupled to the feedforward circuitry 230. The comparison circuitry 235 has an output coupled to the first output stage circuitry 240. The comparison circuitry 235 receives the single-ended error signal from the feedforward circuitry 230. The comparison circuitry 235 compares the single-ended error signal to the triangle signal to generate a square wave waveform as a comparison output. The comparison output of the comparison circuitry 235 has a duty cycle determined by the comparison of the combined error signal and the triangle signal. When the single-ended error signal is greater than the triangle signal, the comparison circuitry 235 sets the comparison output to a logic high (e.g., a logic one). When the combined error signal is less than the triangle signal, the comparison circuitry 235 sets the comparison output to a logic low (e.g., a logic zero). Advantageously, the duty cycle of the comparison output is based on the combined error signal. Advantageously, averaging the comparison output generates a sine wave shape for the linear adjustment of the combined error and negative output signal for the input signal differential pair. The comparison circuitry 235 supplies the comparison output to the first output stage circuitry 240.

[0051] The first output stage circuitry 240 has an input coupled to the comparison circuitry 235. The first output stage circuitry 240 has an output coupled to the class-AB amplifier circuitry 140, the filter circuitry 150, the first resistor 120, and the output detection circuitry 245. The first output stage circuitry 240 receives the comparison output from the comparison circuitry 235. The first output stage circuitry 240 generates a positive output signal based on the comparison output. In some examples, the first output stage circuitry 240 generates the positive output signal using a first power domain, while the comparison output has a second power domain. In such examples, the first power domain can be a relatively higher power domain as compared to the second power domain of the comparison output. For example, the first power domain can be a twelve volt power domain, while the second power domain can be a three volt power domain. In this example, the comparison output can be generated using a relatively lower power supply. Advantageously, the relatively lower power circuitry reduces cost and increases speed of the class-D amplifier circuitry 130. The first output stage circuitry 240 supplies the positive output signal to the filter circuitry 150 and the first resistor 120.

[0052] The output detection circuitry 245 has a first input coupled to the negative output signal of the class AB amplifier circuitry 140. The output detection circuitry 245 has a first output coupled to the filter circuitry 150, the first resistor 120, and the first output stage circuitry 240. The output detection circuitry has second and third outputs coupled to the modulator circuitry 220. The output detection circuitry has a fourth output coupled to the class AB amplifier circuitry 140. The output detection circuitry 245 determines whether the resistance of the load coupled to the filter circuitry 150 is greater than a threshold resistance. In some examples, the output detection circuitry 245 sets the positive output signal to a fixed voltage. In such examples, the output detection circuitry 245 measures the voltage of the negative output signal in response to the fixed voltage at the positive output signal. The output detection circuitry 245 determines the resistance of the load based on the fixed voltage and the measured voltage.

[0053] When the resistance of the load is less than the threshold resistance, the output detection circuitry 245 configures the modulator circuitry 220 for a relatively high order of modulation and increases the gain of the class AB amplifier circuitry 140. For example, when the load is a speaker 160 having a resistance of 4 ohms, the output detection circuitry 245 adjusts the modulator circuitry 220 to use a third order transfer function and sets the gain of the class AB amplifier circuitry 140 to approximately eighty. Figure 1 When the resistance of the load is greater than the threshold resistance, the output detection circuitry 245 configures the modulator circuitry 220 for a relatively low order of modulation and decreases the gain of the class AB amplifier circuitry 140. For example, when the load is a load output 170 having a resistance of 16 ohms, the output detection circuitry 245 adjusts the modulator circuitry 220 to use a second order transfer function and sets the gain of the class AB amplifier circuitry 140 to a minimum value. Figure 1 Advantageously, the output detection circuitry 245 allows the multi-class modulator circuitry 110 to be coupled to a variety of possible loads without having the LC resonance that would make a class D amplifier circuitry 130 unstable.

[0054] Gain selection circuit system 255 has a first input coupled to second resistor 125, feedforward circuit system 230, output detection circuit system 245, and second output stage circuit system 265. Gain selection circuit system 255 has a second input coupled to output detection circuit system 245. Gain selection circuit system 255 has an output coupled to amplifier circuit system 260. Gain selection circuit system 255 sets the gain of amplifier circuit system 260 based on the detection of a negative output signal and output detection circuit system 245. When output detection circuit system 245 detects a load with a resistance less than a threshold resistance, gain selection circuit system 255 configures amplifier circuit system 260 to have a relatively high gain. In this configuration, the relatively high gain of gain selection circuit system 255 configures amplifier circuit system 260 to operate to saturate the negative output signal. When output detection circuit system 245 detects a load with a resistance greater than the threshold resistance, gain selection circuit system 255 configures amplifier circuit system 260 to have a relatively low gain. In this configuration, the relatively low gain of the gain selection circuitry 255 prevents the amplifier circuitry 260 from operating under saturation conditions.

[0055] Amplifier circuit system 260 has first and second inputs coupled to second adjustment circuit system 135. Amplifier circuit system 260 has a third input coupled to gain selection circuit system 255. Amplifier circuit system 260 receives differential pairs of input signals from second adjustment circuit system 135. Gain selection circuit system 255 configures the gain of amplifier circuit system 260. Amplifier circuit system 260 determines the difference between the differential pairs of input signals. Amplifier circuit system 260 amplifies the difference between the differential input signals to generate an amplified output signal.

[0056] In some examples, a relatively high gain configures amplifier circuitry 260 for saturation operation. In saturation operation, the amplified output signal is approximately equal to a first supply value for an input signal greater than a first value, and approximately equal to a second supply voltage for an input signal less than a second value. The first and second values ​​are approximately equal to the supply value divided by the relatively high gain. However, amplifier circuitry 260 operates in linear operation for values ​​between the first and second values. In linear operation, the input signal transitions between the first and second values. The gain is adjusted to reduce the time amount of the linear operation. Ideally, amplifier circuitry 260 is configured to operate linearly only in saturation operation to reduce the negative output. Advantageously, considering that amplifier circuitry 260 is in linear operation, feedforward circuitry 230 adjusts the positive output signal.

[0057] The second output stage circuitry 265 has an input coupled to the amplifier circuitry 260. The second output stage circuitry 265 has an output coupled to the second resistor 125, the class-D amplifier circuitry 130, the filter circuitry 150, the feed-forward circuitry 230, the output detection circuitry 245, and the gain selection circuitry 255. The second output stage circuitry 255 receives the amplified output from the comparison circuitry 235. The second output stage circuitry 265 generates a negative output signal based on the amplifier output. In some examples, the second output stage circuitry 265 generates the negative output signal using a first power domain, while the amplifier output has a second power domain. In such examples, the first power domain can be a relatively higher power domain than the second power domain of the amplified output. For example, the first power domain can be a twelve volt power domain, while the second power domain can be a three volt power domain. In this example, the amplified output can be generated using a relatively lower power. Advantageously, the relatively lower power circuitry reduces cost and increases speed of the class-AB amplifier circuitry 140. The second output stage circuitry 265 supplies the negative output signal to the second resistor 125, the filter circuitry 150, the feed-forward circuitry 230, the output detection circuitry 245, and the gain selection circuitry 255.

[0058] The inductor 270 has a first terminal coupled to the first resistor 120 and the class-D amplifier circuitry 130. The inductor 270 has a second terminal coupled to the first capacitor 275 and adapted to be coupled to a load (e.g., the speaker 160 and / or the load output 170). The inductor 270 prevents a spike of output current from being supplied to the load in response to a transition of the positive output signal. The inductor 270 allows excess charge from the current spike to recirculate through the filter circuitry 150, rather than being supplied to the load. The inductor 270 averages the positive output signal to convert the positive output signal from a square wave shape to a sinusoidal shape. Advantageously, the inductor 270 increases efficiency of the filter circuitry 150.

[0059] The first capacitor 275 has a first terminal coupled to the inductor 270 and adapted to be coupled to a load. The first capacitor 275 has a second terminal coupled to the second resistor 125, the amplifier circuitry 130, 140, the second capacitor 280, and adapted to be coupled to a load. The first capacitor 275 averages relatively higher frequency signals of the differential output signal. In some examples, the relatively higher frequency signals are noise on the differential output signal.

[0060] The second capacitor 280 has a first terminal coupled to the second resistor 125, the amplifier circuitry 130, 140, the first capacitor 275, and adapted to be coupled to a load. The second capacitor 280 has a second terminal coupled to a common terminal (e.g., ground) that supplies a common potential. The second capacitor 280 averages relatively higher frequency signals of the negative output signal. In some examples, the relatively higher frequency signals are noise on the negative output signal.

[0061] Figure 3A and 3B is Figure 1 and 2 a first conditioning circuitry 115 of the first example, Figure 1 and 2 a class-D amplifier circuitry 130 of the second example, Figure 2 a modulator circuitry 220 of the third example, Figure 2 a combination circuitry 225 of the fourth example, Figure 2 a feed-forward circuitry 230 of the fifth example, Figure 2 a comparison circuitry 235 of the sixth example, Figure 2 a first output stage circuitry 240 of the seventh example, and Figure 2 an output detection circuitry 245 of the eighth example. In Figure 3B the first example, the first conditioning circuitry 115 includes a third example resistor 302, a fourth example resistor 304, a first example capacitor 306, a fifth example resistor 308, and a sixth example resistor 310.

[0062] In Figure 3B the third example, the modulator circuitry 220 includes a first example amplifier 312, a second example capacitor 314, a third example capacitor 316, a first example switch 318, a second example switch 320, a seventh example resistor 321, an eighth example resistor 322, a fourth example capacitor 323, a third example switch 324, a fifth example capacitor 325, a fourth example switch 326, a second example amplifier 327, a sixth example capacitor 328, a seventh example capacitor 330, a fifth example switch 332, a sixth example switch 333, a seventh example switch 334, an eighth example switch 335, a ninth example resistor 336, a tenth example resistor 338, an eleventh example resistor 340, a ninth example switch 342, a twelfth example resistor 344, a tenth example switch 346, a third example amplifier 348, an eighth example capacitor 350, a ninth example capacitor 352, an eleventh example switch 354, and a twelfth example switch 356.

[0063] In Figure 3BIn the example, the combined circuit system 225 includes a first example variable resistor 357, a second example variable resistor 358, a thirteenth example resistor 359, a third example variable resistor 360, a fourth example amplifier 361, a fourth example variable resistor 362, a fifth example variable resistor 363, a fourteenth example resistor 364, and a sixth example variable resistor 365. Figure 3B In the example, the feedforward circuit system 230 includes a fifteenth example resistor 366, a fifth example amplifier 367, a sixteenth example resistor 368, a seventeenth example resistor 369, an eighteenth example resistor 370, a nineteenth example resistor 371, an example voltage divider circuit system 372, and a twentieth example resistor 373.

[0064] exist Figure 3A In the example, the comparator circuit system 235 includes a sixth example amplifier 374 and an example triangular signal 375. Figure 3A In the example, the first output stage circuit system 240 includes an example logic driver circuit system 376, a first example level shifter circuit system 377, a second example level shifter circuit system 378, an example power stage circuit system 379, a first example driver 380, a first example transistor 381, a second example driver 382, ​​and a second example transistor 383. Figure 3B In the example, the output detection circuit system 245 includes an example digital-to-analog converter (DAC) 384, an example analog-to-digital converter (ADC) 385, an example resistance determination circuit system 386, and an example controller circuit system 388.

[0065] The third resistor 302 has a design suitable for coupling to Figure 1 The first terminal of the audio source 105. The third resistor 302 has a second terminal coupled to the fourth resistor 304 and the first capacitor 306. The fourth resistor 304 has a first terminal coupled to the third resistor 302 and the first capacitor 306. The fourth resistor 304 has a second terminal coupled to the first resistor 120 and the modulator circuit system 220. The first capacitor 306 has a first terminal coupled to the resistors 302 and 304. The first capacitor 306 has a second terminal coupled to the resistors 302 and 304. The fifth resistor 308 has a first terminal adapted to be coupled to the audio source 105. The fifth resistor 308 has a second terminal coupled to the first capacitor 306 and the sixth resistor 310. The sixth resistor 310 has a first terminal coupled to the first capacitor 306 and the fifth resistor 308. The sixth resistor 310 has a second terminal coupled to the second resistor 125 and the modulator circuit system 220.

[0066] The third resistor 302 receives a positive input signal from the audio source 105, while the fifth resistor 308 receives a negative input signal from the audio source 105. Resistors 302, 308, and the first capacitor 306 filter out relatively high-frequency noise in the differential pair of the input signals. In some examples, resistors 302, 308, and capacitor 306 may be referred to as low-pass filters. Advantageously, resistors 302, 308, and capacitor 306 reduce relatively high-frequency noise.

[0067] The fourth resistor 304 receives the filtered positive input signal, while the sixth resistor 310 receives the filtered negative input signal. Furthermore, the fourth resistor 304 receives the positive output signal from the first resistor 120, while the sixth resistor 310 receives the negative output signal from the second resistor 125. Resistors 304 and 310 combine the filtered input signal differential pair with the output signal differential pair. In some examples, resistors 304 and 310 may be referred to as summing resistors. Resistors 304 and 310 supply the combined signal to the modulator circuit system 220.

[0068] The first amplifier 312 has a first input coupled to a first regulating circuit system 115, a first resistor 120, and a second capacitor 314. The first amplifier 312 has a second input coupled to the first regulating circuit system 115, a second resistor 125, and a third capacitor 316. The first amplifier 312 has a first output coupled to the second capacitor 314, a first switch 318, and a seventh resistor 321. The first amplifier 312 has a second output coupled to the third capacitor 316, a second switch 320, and an eighth resistor 322.

[0069] The second capacitor 314 has a first terminal coupled to the first regulating circuit system 115, the first resistor 120, and the first amplifier 312. The second capacitor 314 also has a first terminal coupled to the first amplifier 312, the first switch 318, and the seventh resistor 321. The third capacitor 316 has a first terminal coupled to the first regulating circuit system 115, the second resistor 125, and the first amplifier 312. The third capacitor 316 also has a second terminal coupled to the first amplifier 312, the second switch 320, and the eighth resistor 322.

[0070] The first amplifier 312 receives a combined signal from resistors 304 and 310. Capacitors 314 and 316 provide frequency-dependent feedback to the input of the first amplifier 312. The first amplifier 312 and capacitors 314 and 316 integrate the combined signal. In some examples, the first amplifier 312 and capacitors 314 and 316 are described as an integrator circuit system. The first amplifier 312 supplies the first-order integrated signal to switches 318 and 320 and resistors 321 and 322.

[0071] The first switch 318 has a first terminal coupled to the first amplifier 312, the second capacitor 314, the seventh resistor 321, and the fourth capacitor 323. The first switch 318 also has a second terminal coupled to the first variable resistor 357. The first switch 318 has a control terminal coupled to the controller circuit system 388. The second switch 320 has a first terminal coupled to the first amplifier 312, the third capacitor 316, the eighth resistor 322, and the fifth capacitor 325. The second switch 320 has a second terminal coupled to the fourth variable resistor 362. The second switch 320 also has a control terminal coupled to the controller circuit system 388. When closed, switches 318 and 320 couple the first-order integrated signal from the first amplifier 312 to the combined circuit system 225. When open, switches 318 and 320 prevent the first-order integrated signal from coupling to the combined circuit system 225.

[0072] The seventh resistor 321 has a first terminal coupled to the first amplifier 312, the first switch 318, and capacitors 314 and 323. The seventh resistor 321 also has a second terminal coupled to the third switch 324, the second amplifier 327, the sixth capacitor 328, and the eleventh resistor 340. The eighth resistor 322 has a first terminal coupled to the first amplifier 312, the second switch 320, and capacitors 316 and 325. The eighth resistor 322 also has a second terminal coupled to the fourth switch 326, the second amplifier 327, the seventh capacitor 330, and the twelfth resistor 344.

[0073] Resistors 321 and 322 receive the first-order integrated signal from the first amplifier 312. Capacitors 314 and 316, along with resistors 321 and 322, form a high-pass filter circuit system. Capacitors 314 and 316, and resistors 321 and 322 filter out relatively low-frequency signals from the first-order integrated signal. Furthermore, when switches 342 and 346 are closed (e.g., turned on), resistors 321 and 322 combine the filtered first-order integrated signal with the third-order integrated signal. In some examples, resistors 321 and 322 may be referred to as summing resistors. Resistors 321 and 322 supply the combined integrated signal to the second amplifier 327.

[0074] The fourth capacitor 323 has a first terminal coupled to the first amplifier 312, the second capacitor 314, the first switch 318, and the seventh resistor 321. The fourth capacitor 323 has a second terminal coupled to the third switch 324. The third switch 324 has a first terminal coupled to the fourth capacitor 323 and a second terminal coupled to resistors 321 and 340, the second amplifier 327, and the sixth capacitor 328. The third switch 324 has a control terminal coupled to the controller circuit system 388.

[0075] The fifth capacitor 325 has a first terminal coupled to the first amplifier 312, the third capacitor 316, the second switch 320, and the eighth resistor 322. The fifth capacitor 325 has a second terminal coupled to the fourth switch 326. The fourth switch 326 has a first terminal coupled to the fifth capacitor 325 and a second terminal coupled to resistors 322 and 344, the second amplifier 327, and the seventh capacitor 330. The fourth switch 326 has a control terminal coupled to the controller circuit system 388.

[0076] When closed, switches 324 and 326 couple the first-order integral signal from the first amplifier 312 to the input of the second amplifier 327 through capacitors 323 and 325. In this example, capacitors 323 and 325 filter the frequency of the first-order integral signal. When open, switches 324 and 326 prevent the first-order integral signal from coupling to the input of the second amplifier 327.

[0077] The second amplifier 327 has a first input coupled to resistors 321 and 340 and a sixth capacitor 328. The second amplifier 327 has a second input coupled to resistors 322 and 344 and a seventh capacitor 330. The second amplifier 327 has a first output coupled to the sixth capacitor 328, switches 332 and 333, and a ninth resistor 336. The second amplifier 327 has a second output coupled to the seventh capacitor 330, switches 334 and 335, and a tenth resistor 338.

[0078] The sixth capacitor 328 has a first terminal coupled to resistors 321 and 340 and the second amplifier 327. The sixth capacitor 328 also has a second terminal coupled to the second amplifier 327, switches 332 and 333, and the ninth resistor 336. The seventh capacitor 330 has a first terminal coupled to resistors 322 and 344 and the second amplifier 327. The seventh capacitor 330 also has a second terminal coupled to the second amplifier 327, switches 334 and 335, and the tenth resistor 338.

[0079] The second amplifier 327 receives the combined integrated signal from resistors 321 and 322. Capacitors 328 and 330 provide frequency-dependent feedback to the input of the second amplifier 327. The second amplifier 327 and capacitors 328 and 330 integrate the combined integrated signal. In some examples, the second amplifier 327 and capacitors 328 and 330 are described as an integrator circuit system. The second amplifier 327 supplies the second-order integrated signal to switches 332, 333, 334, and 335 and resistors 336 and 338.

[0080] The fifth switch 332 has a first terminal coupled to the second amplifier 327, the sixth capacitor 328, the sixth switch 333, and the ninth resistor 336. The fifth switch 332 has a second terminal coupled to the second variable resistor 358. The fifth switch 332 has a control terminal coupled to the controller circuit system 388. The sixth switch 333 has a first terminal coupled to the second amplifier 327, the sixth capacitor 328, the fifth switch 332, and the ninth resistor 336. The sixth switch 333 has a second terminal coupled to resistors 359 and 370 and the fourth amplifier 361. The sixth switch 333 has a control terminal coupled to the controller circuit system 388.

[0081] The seventh switch 334 has a first terminal coupled to the second amplifier 327, the seventh capacitor 330, the eighth switch 335, and the tenth resistor 338. The seventh switch 334 also has a second terminal coupled to the fifth variable resistor 363. The seventh switch 334 has a control terminal coupled to the controller circuit system 388. The eighth switch 335 has a first terminal coupled to the second amplifier 327, the seventh capacitor 330, the seventh switch 334, and the tenth resistor 338. The eighth switch 335 also has a second terminal coupled to the fourth amplifier 361 and resistors 364 and 366. The eighth switch 335 also has a control terminal coupled to the controller circuit system 388.

[0082] When closed, switches 332 and 334 couple the second-order integral signal from the second amplifier 327 to the combined circuit system 225. When open, switches 332 and 334 prevent the second-order integral signal from being supplied to the combined circuit system 225. When closed, switches 333 and 335 couple the second-order integral signal from the second amplifier 327 to the feedforward circuit system 230. When open, switches 333 and 335 prevent the second-order integral signal from being supplied to the feedforward circuit system 230.

[0083] Ninth resistor 336 has a first terminal coupled to second amplifier 327, switches 332 and 333, and sixth capacitor 328. Ninth resistor 336 has a second terminal coupled to third amplifier 348 and eighth capacitor 350. Tenth resistor 338 has a first terminal coupled to second amplifier 327, switches 334 and 335, and seventh capacitor 330. Tenth resistor 338 has a second terminal coupled to third amplifier 348 and ninth capacitor 352.

[0084] Resistors 336 and 338 receive the second-order integrated signal from the second amplifier 327. Capacitors 328 and 330, along with resistors 336 and 338, form a high-pass filter circuit system. Capacitors 328 and 330, along with resistors 336 and 338, filter out relatively low-frequency signals from the second-order integrated signal.

[0085] Eleventh resistor 340 has a first terminal coupled to seventh resistor 321, second amplifier 327, and sixth capacitor 328. Eleventh resistor 340 has a second terminal coupled to ninth switch 342. Ninth switch 342 has a first terminal coupled to eleventh resistor 340. Ninth switch 342 has a second terminal coupled to third amplifier 348, eighth capacitor 350, and eleventh switch 354. Ninth switch 342 has a control terminal coupled to controller circuit system 388.

[0086] Eleventh resistor 340 and ninth switch 342 form a feedback loop that supplies one of the third-order integrated signals to second amplifier 327. When ninth switch 342 is closed (e.g., on), eleventh resistor 340 and ninth switch 342 couple the first output of third amplifier 348 to the first input of second amplifier 327. When ninth switch 342 is open (e.g., not on), ninth switch 342 prevents the first output of third amplifier 348 from being supplied to the first input of second amplifier 327. In this example, eleventh resistor 340 stabilizes the timing of the feedback loop.

[0087] The twelfth resistor 344 has a first terminal coupled to the eighth resistor 322, the second amplifier 327, and the seventh capacitor 330. The twelfth resistor 344 has a second terminal coupled to the tenth switch 346. The tenth switch 346 has a first terminal coupled to the twelfth resistor 344. The tenth switch 346 has a second terminal coupled to the third amplifier 348, the ninth capacitor 352, and the twelfth switch 356. The tenth switch 346 has a control terminal coupled to the controller circuit system 388.

[0088] The twelfth resistor 344 and the tenth switch 346 form a feedback loop that supplies one of the third-order integrated signals to the second amplifier 327. When the tenth switch 346 is closed (e.g., on), the twelfth resistor 344 and the tenth switch 346 couple the second output of the third amplifier 348 to the second input of the second amplifier 327. When the tenth switch 346 is open (e.g., not on), the tenth switch 346 prevents the second output of the third amplifier 348 from being supplied to the second input of the second amplifier 327. In this example, the twelfth resistor 344 stabilizes the timing of the feedback loop.

[0089] The third amplifier 348 has a first input coupled to the ninth resistor 336 and the eighth capacitor 350. The third amplifier 248 has a second input coupled to the tenth resistor 338 and the ninth capacitor 352. The third amplifier 248 has a first output coupled to switches 342 and 354 and the eighth capacitor 350. The third amplifier 348 has a second output coupled to switches 346 and 356 and the ninth capacitor 352.

[0090] The eighth capacitor 350 has a first terminal coupled to the ninth resistor 336 and the third amplifier 348. The eighth capacitor 350 has a second terminal coupled to switches 342, 354 and the third amplifier 348. The ninth capacitor 352 has a first terminal coupled to the tenth resistor 338 and the third amplifier 348. The ninth capacitor 352 has a second terminal coupled to switches 346, 356 and the third amplifier 348.

[0091] The third amplifier 348 receives the second-order integrated signal from resistors 336 and 338. Capacitors 350 and 352 provide frequency-dependent feedback to the input of the third amplifier 348. The third amplifier 348 and capacitors 350 and 352 integrate the second-order integrated signal. In some examples, the third amplifier 348 and capacitors 350 and 352 are described as an integrator circuit system. The third amplifier 348 supplies the third-order integrated signal to switches 342, 346, 354, and 356.

[0092] Eleventh switch 354 has a first terminal coupled to ninth switch 342, third amplifier 348, and eighth capacitor 350. Eleventh switch 354 has a second terminal coupled to third variable resistor 360. Eleventh switch 354 has a control terminal coupled to controller circuit system 388. Twelfth switch 356 has a first terminal coupled to tenth switch 346, third amplifier 348, and ninth capacitor 352. Twelfth switch 356 has a second terminal coupled to sixth variable resistor 365. Twelfth switch 356 has a control terminal coupled to controller circuit system 388.

[0093] Switches 354 and 356 receive a third-order integrated signal from the third amplifier 348. When closed, switches 354 and 356 supply the third-order integrated signal to the variable resistors 360 and 365 of the combinational circuit system 225. When open, switches 354 and 356 prevent the third amplifier 348 from supplying the third-order integrated signal to the combinational circuit system 225.

[0094] The first variable resistor 357 has a first terminal coupled to the first switch 318 and a second terminal coupled to variable resistors 358, 360, the thirteenth resistor 359, and the fourth amplifier 361. In some examples, the first variable resistor 357 has a control terminal coupled to the controller circuit system 388. In such examples, the controller circuit system 388 can configure the resistance of the first variable resistor 357.

[0095] The second variable resistor 358 has a first terminal coupled to the fifth switch 332 and a second terminal coupled to variable resistors 357, 360, the thirteenth resistor 359, and the fourth amplifier 361. In some examples, the second variable resistor 358 has a control terminal coupled to a controller circuit system 388. In such examples, the controller circuit system 388 can configure the resistance of the second variable resistor 358. The thirteenth resistor 359 has a first terminal coupled to variable resistors 357, 358, 360, and the fourth amplifier 361 and a second terminal coupled to the sixth switch 333, the fourth amplifier 361, and the eighteenth resistor 370.

[0096] The third variable resistor 360 has a first terminal coupled to the eleventh switch 354 and a second terminal coupled to the first variable resistor 357 and the fourth amplifier 361. In some examples, the third variable resistor 360 has a control terminal coupled to the controller circuit system 388. In such examples, the controller circuit system 388 can configure the resistance of the third variable resistor 360.

[0097] The fourth amplifier 361 has a first input coupled to variable resistors 357, 358, 360 and the thirteenth resistor 359, and a second input coupled to variable resistors 362 and 365. The fourth amplifier 361 has a first output coupled to the sixth switch 333 and resistors 359 and 370. The fourth amplifier 361 has a second output coupled to the eighth switch 335 and resistors 364 and 366.

[0098] The fourth variable resistor 362 has a first terminal coupled to the second switch 320 and a second terminal coupled to the fourth amplifier 361, variable resistors 363, 365, and the fourteenth resistor 364. In some examples, the fourth variable resistor 362 has a control terminal coupled to the controller circuit system 388. In such examples, the controller circuit system 388 can configure the resistance of the fourth variable resistor 362.

[0099] The fifth variable resistor 363 has a first terminal coupled to the seventh switch 334 and a second terminal coupled to the fourth amplifier 361, variable resistors 362, 365, and the fourteenth resistor 364. In some examples, the fifth variable resistor 363 has a control terminal coupled to the controller circuit system 388. In such examples, the controller circuit system 388 can configure the resistance of the fifth variable resistor 363. The fourteenth resistor 364 has a first terminal coupled to the fourth amplifier 361 and variable resistors 362, 363, 365, and a second terminal coupled to the eighth switch 335, the fourth amplifier 361, and the fifteenth resistor 366.

[0100] The sixth variable resistor 365 has a first terminal coupled to the twelfth switch 356 and a second terminal coupled to the fourth amplifier 361, variable resistors 362, 363, and the fourteenth resistor 364. In some examples, the sixth variable resistor 365 has a control terminal coupled to a controller circuit system 388. In such examples, the controller circuit system 388 can configure the resistance of the sixth variable resistor 365.

[0101] exist Figure 3B In the example, variable resistors 357 and 362 have a first resistance representing a first parameter (a1) of the first-order integral signal from modulator circuitry 220. In some examples, the first parameter may correspond to the first-order coefficients of the transfer function. In such examples, the resistance of variable resistors 357 and 362 can be modified based on the operating mode of modulator circuitry 220. Advantageously, the contribution of the first-order integral signal to the error signal generated by the fourth amplifier 361 can be modified by variable resistors 357 and 362.

[0102] exist Figure 3B In the example, variable resistors 358 and 363 have a second resistance representing a second parameter (a2) of the second-order integral signal from modulator circuitry 220. In some examples, the second parameter may correspond to the second-order coefficients of the transfer function. In such examples, the resistance of variable resistors 358 and 363 can be modified based on the operating mode of modulator circuitry 220. For example, the second resistance of variable resistors 358 and 363 may be a first value for third-order modulation and a second value for second-order modulation. Advantageously, the contribution of the second-order integral signal to the error signal generated by the fourth amplifier 361 can be modified by variable resistors 358 and 363.

[0103] exist Figure 3B In the example, variable resistors 360 and 365 have a third resistance representing a third parameter (a3) ​​of the third-order integral signal from modulator circuitry 220. In some examples, the third parameter may correspond to the third-order coefficients of the transfer function. In such examples, the resistance of variable resistors 360 and 365 can be modified based on the operating mode of modulator circuitry 220. Advantageously, the contribution of the third-order integral signal to the error signal generated by the fourth amplifier 361 can be modified by variable resistors 360 and 365.

[0104] The fourth amplifier 361 combines the contributions from variable resistors 357, 358, 360, 362, 363, and 365 to generate an error signal differential pair. The fourth amplifier 361 isolates the modulator circuitry 220 from the feedforward circuitry 230. The fourth amplifier 361 supplies the error signal differential pair to resistors 366 and 370.

[0105] The fifteenth resistor 366 has a first terminal coupled to the eighth switch 335, the fourth amplifier 361, and the fourteenth resistor 364. The fifteenth resistor 366 has a second terminal coupled to the fifth amplifier 367 and resistors 368 and 369. The fifteenth resistor 366 receives the first error signal from the error signal differential pair in the combined circuit system 225.

[0106] The fifth amplifier 367 has a first input coupled to resistors 366, 368, and 369, and a second input coupled to resistors 370, 371, and 373. The fifth amplifier 367 has an output coupled to the sixteenth resistor 368 and the sixth amplifier 374.

[0107] The sixteenth resistor 368 has a first terminal coupled to amplifiers 367 and 374 and a second terminal coupled to the fifth amplifier 367 and resistors 366 and 369. The sixteenth resistor 368 couples the input and output of the fifth amplifier 367. The sixteenth resistor 368 stabilizes the timing of the loop formed between the input and output of the fifth amplifier 367. In some examples, the sixteenth resistor 368 may be described and / or referred to as a feedback resistor. Furthermore, the resistance of the sixteenth resistor 368 can set the gain of the fifth amplifier 367.

[0108] The seventeenth resistor 369 has a first terminal coupled to resistors 366, 368 and the fifth amplifier 367, and a second terminal coupled to a supply terminal supplying a scaled power supply value (PVDD / N). The scaled power supply value is a voltage proportional to the power supply value (PVDD) of the power stage circuit system 379. In some examples, a voltage divider circuit system is coupled between the seventeenth resistor 369 and the supply terminal of the power stage circuit system 379 to generate the scaled power supply value. In other examples, another resistor is coupled between the seventeenth resistor 369 and the supply terminal of the power stage circuit system 379 to form a voltage divider.

[0109] The eighteenth resistor 370 has a first terminal coupled to the sixth switch 333, the fourth amplifier 361, and the thirteenth resistor 359. The eighteenth resistor 370 has a second terminal coupled to the fifth amplifier 367 and resistors 371 and 373. The eighteenth resistor 370 receives a second error signal from the error signal differential pair in the combined circuit system 225.

[0110] Nineteenth resistor 371 has a first terminal coupled to fifth amplifier 367 and resistors 370, 373, and a second terminal coupled to a common-mode terminal supplying the common-mode voltage (VCM). The common-mode voltage represents the target common-mode voltage of the error signal differential pair from combinational circuit system 225. In some examples, a voltage divider circuit system is coupled between nineteenth resistor 371 and the error signal differential pair to determine the common-mode voltage. In other examples, the common-mode voltage is approximately equal to the common-mode voltage of triangular signal 375. Advantageously, the common-mode voltage can adjust the DC offset of the output of fifth amplifier 367.

[0111] Voltage divider circuit system 372 has inputs coupled to Class AB amplifier circuit system 140 and output determination circuit system 245. Voltage divider circuit system 372 has an output coupled to twentieth resistor 373. Voltage divider circuit system 372 receives a negative output signal from Class AB amplifier circuit system 140. Voltage divider circuit system 372 divides the negative output signal by a scalar value to generate a scaled negative output signal. In some examples, the scalar value of voltage divider circuit system 372 is determined by the logic levels of comparison circuit system 235 and / or combination circuit system 225. In such examples, the scalar value allows voltage divider circuit system 372 to supply a relatively low-power version of the negative output signal to fifth amplifier 367. Twentieth resistor 373 has a first terminal coupled to voltage divider circuit system 372 and a second terminal coupled to fifth amplifier 367 and resistors 370, 371.

[0112] Resistors 366, 368, and 369 combine a first error signal, a scaled supply voltage, and the output of the fifth amplifier 367. Resistors 370, 371, and 373 combine a second error signal, a common-mode voltage, and a scaled negative output signal. The fifth amplifier 367 generates a combined error signal based on the voltages supplied by resistors 366, 368, 369, 370, 371, and 373. The combined error signal combines the nonlinearity of the error signal differential pair from the modulator circuit system 220 with the negative output signal. Furthermore, the fifth amplifier 367 determines that the combined error signal has a voltage between the scaled supply voltage from the seventeenth resistor 369 and the common-mode voltage from the nineteenth resistor 371. Advantageously, the Class D amplifier circuit system 130 operates in response to supplying the combined error signal to the comparator circuit system 235, taking into account the nonlinearity of the negative output signal.

[0113] The sixth amplifier 374 has a first input coupled to the fifth amplifier 367 and the sixteenth resistor 368. The sixth amplifier 374 has a second input coupled to a triangular signal 375. The sixth amplifier 374 has an output coupled to the logic driver circuitry 376. The sixth amplifier 374 receives a combination error signal from the fifth amplifier 367. The sixth amplifier 374 receives the triangular signal 375 at its second input. The triangular signal 375 is a triangular waveform with a fixed frequency. The fixed frequency of the triangular signal 375 corresponds to a relatively high switching frequency of the positive output signal. In some examples, the fixed frequency of the triangular signal 375 is referred to as the carrier frequency. The sixth amplifier 374 supplies a modulated signal to the logic driver circuitry 376.

[0114] The sixth amplifier 374 compares the combinational error signal with the triangular signal 375. In some examples, when the combinational error signal is greater than the triangular signal 375, the sixth amplifier 374 sets the modulated signal to logic high (e.g., logic one). In such examples, when the combinational error signal is less than the triangular signal 375, the sixth amplifier 374 sets the modulated signal to logic low (e.g., logic zero). The sixth amplifier 374 uses pulse width modulation (PWM) to generate the modulated signal. In some examples, PWM uses the duty cycle of the signal to represent data. Figure 3A In some examples, the duty cycle of the modulated signal is proportional to the amplitude of the combination error signal. In some examples, in response to the amplitude of the combination error signal being approximately equal to the amplitude of the triangular signal 375, the sixth amplifier 374 generates multiple pulses with relatively high duty cycles. In other examples, in response to the amplitude of the combination error signal being significantly smaller than the amplitude of the triangular signal 375, the sixth amplifier 374 generates multiple pulses with relatively low duty cycles.

[0115] Advantageously, the sixth amplifier 374 uses PWM to convert the sinusoidal waveform of the combination error signal into a discrete signal. Advantageously, the combination error signal can be reconstructed by averaging the modulated signal. Advantageously, using a relatively high carrier frequency (e.g., the fixed frequency of the triangular signal 375) increases noise immunity.

[0116] Logic driver circuitry 376 has an input coupled to a sixth amplifier 374. Logic driver circuitry 376 has outputs coupled to level shifting circuitry 377, 378. Logic driver circuitry 376 receives a modulated signal from the sixth amplifier 374. Logic driver circuitry 376 generates driver signal differential pairs based on the modulated signal. In some examples, logic driver circuitry 376 generates driver signal differential pairs by converting a single-ended modulated signal into a differential signal. In such examples, logic driver circuitry 376 adjusts the differential version of the modulated signal to prevent time overlap between signals in the driver signal differential pairs. The duration of this time overlap prevention can be referred to as dead time. Advantageously, dead time prevents transistors 381, 383 of power stage circuitry 379 from being simultaneously activated. Advantageously, dead time improves power efficiency by reducing crossover duration.

[0117] A first level shift circuit system 377 has an input coupled to a logic driver circuit system 376. The first level shift circuit system 377 has an output coupled to a first driver 380. The first level shift circuit system 377 receives a first driver signal from a driver signal differential pair from the logic driver circuit system 376. A second level shift circuit system 378 has an input coupled to the logic driver circuit system 376. The second level shift circuit system 378 has an output coupled to a second driver 382. The second level shift circuit system 378 receives a second driver signal from a driver signal differential pair from the logic driver circuit system 376.

[0118] Level shifting circuit systems 377 and 378 increase the logic level of the driver signal differential pairs to generate switching signal differential pairs capable of controlling relatively high-power transistors, such as transistors 381 and 383. In some examples, level shifting circuit systems 377 and 378 use amplifiers configured as buffers to increase the drive strength of the driver signal differential pairs. In such examples, the amplifiers of level shifting circuit systems 377 and 378 can use the voltage of a relatively high voltage supply and / or a reference switching circuit system (e.g., transistors 381 and 383) to amplify the driver signal differential pairs. Level shifting circuit systems 377 and 378 supply the switching signal differential pairs to power stage circuit system 379. Advantageously, the logic levels of circuit systems 220, 225, 230, and 235 can be significantly lower than the logic level of the first output stage circuit system 240.

[0119] Power stage circuitry 379 is coupled between level shifting circuitry 377, 378 and filter circuitry 150. Figure 3BIn the example, power stage circuit system 379 includes a first driver 380, a first transistor 381, a second driver 382, ​​and a second transistor 383. Power stage circuit system 379 receives a differential pair of switching signals from level shifting circuit systems 377 and 378. Power stage circuit system 379 switches transistors 381 and 383 to generate a positive output signal.

[0120] The first driver 380 has an input coupled to a first level shift circuit system 377 and an output coupled to a first transistor 381. The first driver 380 has a supply reference coupled to transistors 381 and 383. The first transistor 381 has a first current terminal coupled to a power supply value (PVDD). The power supply value is the voltage of the positive output signal. In some examples, the power supply voltage is a fixed voltage supplied by a power supply. The first transistor 381 has a second current terminal coupled to the first driver 380 and the second transistor 383. The first transistor 381 has a control terminal coupled to the first driver 380.

[0121] The second driver 382 has an input coupled to the second level shift circuit system 378 and an output coupled to the second transistor 383. The second driver 382 has a supply reference coupled to a common terminal supplying a common potential. The second transistor 383 has a first current terminal coupled to the first driver 380 and the first transistor 381. The second transistor 383 has a second current terminal coupled to the common terminal. The second transistor 383 has a control terminal coupled to the second driver 382.

[0122] Drivers 380 and 382 receive differential pairs of switching signals from level shifting circuit systems 377 and 378. Drivers 380 and 382 control transistors 381 and 383 based on the switching signals in the differential switching signal pairs. Transistors 381 and 383 generate a positive output signal by setting the positive output signal to either a power supply value or a common potential. In an example operation, the switching signal corresponds to a first switching operation in which the first transistor 381 sets the positive output signal to approximately equal to the power supply value. In another example operation, the switching signal corresponds to a second switching operation in which the second transistor 383 sets the positive output signal to approximately equal to the common potential. Advantageously, transistors 381 and 383 can be relatively high-voltage transistors in response to the shifting of the logic level of the differential switching signals by level shifting circuit systems 377 and 378 and drivers 380 and 382. Advantageously, power stage circuit system 379 generates a positive output signal based on a PWM of a modulated signal from comparator circuit system 235.

[0123] DAC 384 has an input coupled to controller circuitry 388. DAC 384 has an output suitable for coupling a positive output signal to Class D amplifier circuitry 130 and filter circuitry 150. DAC 384 receives digital values ​​from controller circuitry 388. DAC 384 converts the digital values ​​into an analog voltage. DAC 384 sets the positive output signal to approximately equal to the analog voltage. Advantageously, DAC 384 supplies the analog voltage to filter circuitry 150 via the positive output signal. In some examples, DAC 384 sets the positive output signal when the first output stage circuitry 240 does not set the positive output signal during the duration of setting the positive output signal.

[0124] The ADC 385 has an input suitable for coupling to a negative output signal in a Class AB amplifier circuit system 140 and a filter circuit system 150. The ADC 385 has an output coupled to a resistor determination circuit system 386. The ADC 385 samples the negative output signal in response to a positive output signal set by the DAC 384. The ADC 385 converts the value of the sampled negative output signal from an analog value to a digital value representing the sampled negative output signal value. The ADC 385 supplies the digital value to the resistor determination circuit system 386.

[0125] The resistance determination circuit system 386 has an input coupled to the ADC 385. The resistance determination circuit system 386 has an output coupled to the controller circuit system 388. The resistance determination circuit system 386 receives a digital value from the ADC 385. The resistance determination circuit system 386 compares the digital value of the sampled negative output signal with the digital value supplied to the DAC 384. The resistance determination circuit system 386 determines the load coupled to the filter circuit system 150 (e.g., ...). Figure 1 160 or Figure 1 The resistance determination circuit system 386 determines whether the resistance of the load (line output 170) is greater than the threshold resistance. When it is determined that the resistance of the load exceeds the threshold resistance, the resistance determination circuit system 386 determines that the load is line output 170. However, when it is determined that the resistance of the load is less than the threshold resistance, the resistance determination circuit system 386 determines that the load is speaker 160. The resistance determination circuit system 386 indicates to the controller circuit system 388 whether the resistance of the load is greater than the threshold resistance.

[0126] The controller circuit system 388 has an input coupled to the resistance determination circuit system 386. The controller circuit system 388 has a first output adapted for coupling to the Class AB amplifier circuit system 140. In some examples, the controller circuit system 388 has a second output coupled to variable resistors 357, 358, 360, 362, 363, and 365. The controller circuit system 388 has a third output coupled to switches 318, 320, 324, 326, 332, 333, 334, 335, 342, 346, 354, and 356. The controller circuit system 388 has a fourth output coupled to the DAC 384. The controller circuit system 388 supplies a digital value to the DAC 384 to determine the resistance of the load. The controller circuit system 388 receives from the resistance determination circuit system 386 an indication that the resistance of the load is greater than or less than a threshold resistance. The controller circuit system 388 controls the circuit based on the indication from the resistance determination circuit system 386. Figure 2 The amplifier circuit system 260 has a gain and a second coefficient for the variable resistors 358 and 363. Furthermore, the controller circuit system 388 controls switches 318, 320, 324, 326, 332, 333, 334, 335, 342, 346, 354, and 356 based on instructions from the resistance determination circuit system 386.

[0127] In example operation, in response to the load resistance being less than the threshold resistance, controller circuitry 388 closes switches 318, 320, 332, 334, 342, 346, 354, and 356, and opens switches 324, 326, 333, and 335. In this example operation, in response to the load resistance being less than the threshold resistance, controller circuitry 388 configures the gain of amplifier circuitry 260 and the resistances of variable resistors 358 and 363 to first values. In response to this example operation, controller circuitry 388 configures modulator circuitry 220 as a third-order modulator circuitry implementing a third-order transfer function.

[0128] In another example operation, in response to a load resistance greater than a threshold resistance, controller circuitry 388 disconnects switches 318, 320, 332, 334, 342, 346, 354, and 356, and closes switches 324, 326, 333, and 335. In this type of example operation, in response to a load resistance greater than a threshold resistance, controller circuitry 388 configures the gain of amplifier circuitry 260 and the resistances of variable resistors 358 and 363 to a second value. In response to this type of example operation, controller circuitry 388 configures modulator circuitry 220 as a second-order modulator circuitry implementing a second-order transfer function. Advantageously, controller circuitry 388 adjusts the order of modulator circuitry 220 to compensate for LC resonance in relatively high-resistivity loads.

[0129] Figure 4 yes Figure 1 and 2 The second regulating circuit system 135 and Figure 1 and 2 A schematic diagram of an example of a Class AB amplifier circuit system 140. Figure 4 In the example, the second regulation circuit system 135 includes a first low-pass filter circuit system 405 and a second low-pass filter circuit system 410. Figure 4 In the example, the Class AB amplifier circuit system 140 includes Figure 2 Gain selection circuit system 255 Figure 2 Amplifier circuit system 260, Figure 2 The second output stage circuit system 265, the first example variable resistor 415, the example capacitor 420, the second example variable resistor 425, the first example amplifier 430, the example level shifting circuit system 435, the second example amplifier 440, the third example amplifier 445, the example power stage circuit system 450, the first example transistor 455, and the second example transistor 460.

[0130] The first low-pass filter circuit system 405 has a feature suitable for coupling to Figure 1 The audio source 105 receives input and is coupled to the output of the first amplifier 430. A second low-pass filter circuit system 410 has an input suitable for coupling to the audio source 105 and an output suitable for coupling to the first amplifier 430. Low-pass filter circuit systems 405 and 410 receive differential pairs of input signals. Low-pass filter circuit systems 405 and 410 filter out relatively high-frequency signals from the differential pairs of input signals. Low-pass filter circuit systems 405 and 410 supply the differential pairs of input signals to the first amplifier 430.

[0131] The first variable resistor 415 has coupling to Figure 1 and 2 The first terminal of the second resistor 125, the output stage circuit system 265, and the capacitor 420. The first variable resistor 415 has a second terminal coupled to the capacitor 420, the second variable resistor 425, and the first amplifier 430. In some examples, the first variable resistor 415 has a second terminal adapted to couple to the capacitor 420, the second variable resistor 425, and the first amplifier 430. Figure 3A The controller circuit system 388 has control terminals. In this type of example, the controller circuit system 388 can be configured with the resistance of the first variable resistor 415.

[0132] Capacitor 420 has a first terminal coupled to the second resistor 125, the output stage circuit system 265, and the first variable resistor 415. Capacitor 420 has a second terminal coupled to the variable resistors 415 and 425 and the first amplifier 430.

[0133] The second variable resistor 425 has a first terminal coupled to the first variable resistor 415, the capacitor 420, and the first amplifier 430. The second variable resistor 425 also has a second terminal coupled to a common terminal supplying a common potential. In some examples, the second variable resistor 425 has a control terminal adapted for coupling to a controller circuit system 388. In such examples, the controller circuit system 388 can configure the resistance of the second variable resistor 425.

[0134] Variable resistors 415 and 425 are configured as a voltage divider circuit system. The resistance of variable resistors 415 and 425 sets the gain of the first amplifier 430. Figure 4 In some examples, variable resistors 415 and 425 set the gain of the first amplifier 430 to a relatively high gain (e.g., eighty). In such examples, the relatively high gain of the variable resistors 415 and 425 saturates the output of the first amplifier 430 for a relatively wide range of input voltages. In some examples, the controller circuitry 388 can modify the resistance of the variable resistors 415 and 425 to adjust the gain of the first amplifier 430.

[0135] The first amplifier 430 has first and second inputs adapted to be coupled to an audio source 105 via low-pass filter circuitry 405, 410. The first amplifier 430 has a third input coupled to variable resistors 415, 425 and a capacitor 420. The first amplifier 430 has a first output coupled to a second amplifier 440 and a second output coupled to a third amplifier 445. The first amplifier 430 receives differential pairs of input signals from the low-pass filter circuitry 405, 410. Variable resistors 415, 425 set the gain of the first amplifier 430. The first amplifier 430 generates differential pairs of saturated output signals based on the gain and the input signals. The first amplifier 430 supplies the differential pairs of saturated output signals to amplifiers 440, 445.

[0136] The level shifting circuit system 435 is coupled to the first amplifier 430 and the power stage circuit system 450. Figure 4 In the example, the level shifting circuit system 435 includes amplifiers 440 and 445. The level shifting circuit system 435 shifts the logic level of the saturated output signal differential pair to a logic level that enables the switching transistors 455 and 460.

[0137] The second amplifier 440 has an input coupled to the first amplifier 430 and an output coupled to the first transistor 455. The second amplifier 440 has a first supply input coupled to a negative output reference voltage (OUTM+5V) and a second supply input coupled to transistors 455 and 460. The negative output reference voltage is a voltage that is approximately five volts greater than the voltage of the negative output signal at any given time. In some examples, the Class AB amplifier circuit system 140 includes a charge pump circuit system coupled between the first and second supply inputs of the second amplifier 440 to generate the negative output reference voltage.

[0138] The third amplifier 445 has an input coupled to the first amplifier 430 and an output coupled to the second transistor 460. The third amplifier 445 has a first supply input coupled to a first power supply voltage (GVDD) and a second supply input coupled to a common terminal for supplying a common potential.

[0139] Amplifiers 440 and 445 receive a differential pair of saturated output signals from a first amplifier 430. Amplifiers 440 and 445 amplify the differential pair of saturated output signals based on the supply input. A second amplifier 440 generates a first switching signal based on the first of the saturated output signals using a voltage between the negative output reference voltage and the voltage of the negative output signal. A third amplifier 445 generates a second switching signal based on the second of the saturated output signals using a voltage between the first power supply voltage and the common potential. Advantageously, the voltages of the switching signals have the logic levels of transistors 455 and 460.

[0140] The power stage circuitry 450 is coupled to amplifiers 440 and 445, as well as to the circuitry coupled to the negative output signal. Figure 4 In the example, power stage circuitry 450 includes transistors 455 and 460. Power stage circuitry 450 generates a negative output signal based on a switching signal from level shifting circuitry 435.

[0141] The first transistor 455 has a first current terminal coupled to the second power supply voltage (PVDD) and a second current terminal coupled to the second amplifier 440, the second transistor 460, and a circuit system coupled to the negative output signal. The first transistor 455 also has a control terminal coupled to the second amplifier 440. The second transistor 460 has a first current terminal coupled to the second amplifier 440, the first transistor 455, and a circuit system coupled to the negative output signal. The first transistor 455 has a second current terminal coupled to a common terminal and a control terminal coupled to the second amplifier 440.

[0142] Transistors 455 and 460 set the negative output signal to a voltage between the second power supply voltage and the common potential based on switching signals from amplifiers 440 and 445. In some example operations, such as during saturation operation mode, transistors 455 and 460 set the negative output signal approximately to either the second power supply voltage or the common potential. In other example operations, such as during linear operation mode, transistors 455 and 460 may be partially enabled, setting the negative output signal to a voltage between the second power supply voltage and the common potential. When partially enabled, transistors 455 and 460 conduct a configurable amount of current in response to changes in their transconductance. When the transconductance begins to stabilize and the current conducted by transistors 455 and 460 is fixed, transistors 455 and 460 are considered fully enabled. Advantageously, when in saturation operation mode, one of transistors 455 and 460 is fully enabled (e.g., turned on), while the other is completely deactivated (e.g., not turned on). Advantageously, fully enabling transistors 455 and 460 during saturation operation mode improves power efficiency.

[0143] Figure 5 This is a schematic diagram of an example conversion circuit system 500 that generates differential input signals based on digital values. Figure 5 In the examples, the conversion circuit system 500 includes an example current digital-to-analog converter (IDAC) 505, an example overcurrent circuit system 510, an example switching circuit system 515, a first example resistor 520, a second example resistor 525, an example amplifier 530, a third example resistor 535, a first example capacitor 540, a fourth example resistor 545, and a second example capacitor 550. In some examples, the conversion circuit system 500 draws from... Figure 1 The audio source 105 receives digital values ​​representing audio signals. In some such examples, the conversion circuitry 500 is coupled to... Figure 1 and 2 The audio source 105 is located between the multi-class modulation circuitry system 110 and the audio source 105. In other examples, the audio source 105 includes a conversion circuitry system 500.

[0144] The IDAC 505 has inputs suitable for coupling to a digital data source. For example, the IDAC 505 can be coupled to the audio source 105 when the audio signal is supplied as digital data by the audio source 105. The IDAC 505 has first and second outputs coupled to the overcurrent circuit system 510, the amplifier 530, resistors 535 and 545, and capacitors 540 and 550. The IDAC 505 receives digital data (DATA) from the digital data source. In some examples, the digital data source may be a memory location, an external device, etc. The IDAC 505 converts the digital data into a differential analog current. The IDAC 505 supplies at least a portion of the differential analog current to the overcurrent circuit system and the amplifier 530.

[0145] The overcurrent circuit system 510 is coupled to IDAC 505, amplifier 530, resistors 535 and 545, and capacitors 540 and 550. Figure 5 In one example, the overcurrent circuit system 510 includes a switching circuit system 515 and resistors 520, 525. The overcurrent circuit system 510 provides a current path for excess current from the IDAC 505. In some examples, the overcurrent circuit system 510 is added to the switching circuit system 500 based on the class of the IDAC 505. For example, the switching circuit system 500 includes the overcurrent circuit system 510 in response to the IDAC 505 being a Class A IDAC. In this example, the overcurrent path of the overcurrent circuit system 510 prevents charge buildup due to excess current. In other examples, the switching circuit system 500 does not include the overcurrent circuit system 510.

[0146] Switching circuit system 515 has a first terminal coupled to IDAC 505, amplifier 530, third resistor 535, and first capacitor 540. Switching circuit system 515 has a second terminal coupled to IDAC 505, amplifier 530, fourth resistor 545, and second capacitor 550. Switching circuit system 515 has a third terminal coupled to first resistor 520. Switching circuit system 515 has a fourth terminal coupled to second resistor 525. Switching circuit system 515 couples one of the first or second terminals to one of the third or fourth terminals to provide one or more paths for excess current flow. For example, switching circuit system 515 may couple the first terminal to the third terminal and the second terminal to the fourth terminal. In this example, the first terminal provides a first current path to the third terminal, while the second terminal provides a second current path to the fourth terminal. In some examples, switching circuit system 515 switches the coupled terminals to balance current flow. In such examples, the switching circuit system balances non-ideal variations in resistors 520 and 525 in the two current paths.

[0147] The first resistor 520 has a first terminal coupled to the switching circuit system 515 and a second terminal coupled to a common terminal (e.g., ground) supplying a common potential. The second resistor 525 has a first terminal coupled to the switching circuit system 515 and a second terminal coupled to the common terminal supplying a common potential. Resistors 520 and 525 provide a path for current to be supplied to the common potential. The resistance of resistors 520 and 525 can be referred to as pull-down resistors.

[0148] Amplifier 530 has a first input coupled to IDAC 505, switching circuit system 515, third resistor 535, and first capacitor 540. Amplifier 530 has a second input coupled to IDAC 505, switching circuit system 515, fourth resistor 545, and second capacitor 550. Amplifier 530 has a first output coupled to third resistor 535, first capacitor 540, and adapted to be coupled to multi-class modulator circuit system 110. Amplifier 530 has a second output coupled to fourth resistor 545, second capacitor 550, and adapted to be coupled to multi-class modulator circuit system 110.

[0149] The third resistor 535 has a first terminal coupled to the IDAC 505, the switching circuit system 515, the amplifier 530, and the first capacitor 540. The third resistor 535 also has a second terminal coupled to the amplifier 530, the first capacitor 540, and adapted for coupling to the multi-class modulator circuit system 110. The first capacitor 540 has a first terminal coupled to the IDAC 505, the switching circuit system 515, the amplifier 530, and the third resistor 535. The first capacitor 540 also has a second terminal coupled to the amplifier 530, the third resistor 535, and adapted for coupling to the multi-class modulator circuit system 110.

[0150] The fourth resistor 545 has a first terminal coupled to the IDAC 505, the switching circuit system 515, the amplifier 530, and the second capacitor 550. The fourth resistor 545 has a second terminal coupled to the amplifier 530, the second capacitor 550, and adapted to be coupled to the multi-class modulator circuit system 110. The second capacitor 550 has a first terminal coupled to the IDAC 505, the switching circuit system 515, the amplifier 530, and the fourth resistor 545. The second capacitor 550 has a second terminal coupled to the amplifier 530, the fourth resistor 545, and adapted to be coupled to the multi-class modulator circuit system 110.

[0151] Amplifier 530 receives differential analog current from IDAC 505. Resistors 535, 545 and capacitors 540, 550 configure amplifier 530 for closed-loop operation. Amplifier 530 buffers the differential analog current to generate a differential input signal. In some examples, amplifier 530 amplifies the differential analog current to generate a differential input signal. Resistors 535, 545 and capacitors 540, 550 can filter out relatively high-frequency noise from the differential analog current. In some examples, resistors 535, 545 and capacitors 540, 550 limit the current contribution of the differential analog current.

[0152] Figure 6 yes Figure 1 and 2 Timing diagram 600 for example operation of the multi-class modulation circuit system 110. Figure 6 In the example, timing diagram 600 shows an example positive input signal (INP) 605, an example negative input signal (INM) 610, an example positive output signal (OUTP) 615, an example negative output signal (OUTM) 620, an example filtered positive signal 625, an example filtered negative signal 630, and an example differential load signal 635. Timing diagram 600 shows... Figure 1 , 2 and 3 Class D amplifier circuit system 130 and Figure 1 , 2 Example operation of Class AB amplifier circuit system 140 modulating input signals 605 and 610.

[0153] The positive input signal 605 is from Figure 1 The diagram illustrates the first of the differential input signals of the audio source 105. In some of the described examples, the audio source 105 supplies a positive input signal 605 to the amplifier circuitry 130, 140. In such examples, the positive input signal 605 indicates that it is to be supplied to... Figure 1 Speakers 160 and / or Figure 1 The negative input signal 610 is a representation of at least a portion of the audio signal at line output 170. The negative input signal 610 is an illustration of the second of the differential input signals from audio source 105. In some of the described examples, audio source 105 supplies the negative input signal 610 to amplifier circuitry 130, 140. In such examples, the negative input signal 610 represents at least a portion of the audio signal to be supplied to speaker 160 and / or line output 170.

[0154] The positive output signal 615 is an illustration of the first of the differential output signals from the multi-class modulation circuitry system 110. Specifically, the positive output signal 615 represents the output of the Class D amplifier circuitry system 130. In some of the described examples, the Class D amplifier circuitry system 130 supplies the positive output signal 615 to...Figure 1 and 2 The filter circuit system 150. In this example, the positive output signal 615 represents at least a portion of the modulated audio signal to be supplied to the speaker 160 and / or line output 170. Figure 6 In the example, the positive output signal 615 has a switching frequency that is relatively higher than the input signals 605 and 610. However, for simplicity, another example of the positive output signal 615 is given below. Figure 7 As shown in the image.

[0155] The negative output signal 620 is an illustration of the second of the differential output signals from the multi-class modulation circuitry 110. Specifically, the negative output signal 620 represents the output of the Class AB amplifier circuitry 140. In some of the described examples, the Class AB amplifier circuitry 140 supplies the negative output signal 620 to the filter circuitry 150. In such examples, the negative output signal 620 represents at least a portion of the modulated audio signal to be supplied to the speaker 160 and / or the line output 170.

[0156] The filtered positive signal 625 is an illustration of the first of the differential audio signals supplied by the filter circuit system 150 to a load (e.g., speaker 160, line output 170). Specifically, the filtered positive signal 625 represents the positive output signal 615 after being filtered by the filter circuit system 150. For example, Figure 2 Inductor 270 and / or Figure 2 The first capacitor 275 averages the positive output signal 615 to generate a filtered positive signal 625. In this type of example, the change in the duty cycle of the positive output signal 615 determines the amplitude of the filtered positive signal 625. An example modulation for generating the sinusoidal signal of the positive output signal 615 is described below. Figure 7 As shown in the image.

[0157] The filtered negative signal 630 is an illustration of the second of the differential audio signals supplied by the filter circuit system 150 to a load (e.g., speaker 160, line output 170). Specifically, the filtered negative signal 630 represents the negative output signal 620 after being filtered by the filter circuit system 150. For example, Figure 2 The second capacitor 280 averages the relatively high frequency (e.g., noise) of the negative output signal 620 to generate a filtered negative signal 630.

[0158] The differential load signal 635 is a diagram of the signal applied across the load by the filter circuit system 150. The differential load signal 635 is approximately equal to the difference between the filtered signals 625 and 630. Advantageously, the differential load signal 635 is an amplified version of the input signals 605 and 610. Advantageously, the modulation by the multi-class modulation circuit system 110 improves the total harmonic distortion (THD) of the differential load signal 635 at various frequencies and power levels.

[0159] At the first time 640, the negative output signal 620 leaves the linear region and enters the saturation region. While in the linear region... Figure 2 and 4 The transistors of the second output stage circuit system 265 are partially enabled, which reduces power efficiency. When in the saturation region, the transistors of the second output stage circuit system 265 are fully enabled, which improves efficiency. In the described example, Figure 2 and 4 The amplifier circuit system 260 has a relatively high gain to increase the duration of the negative output signal 620 in the saturation region while reducing the linear region.

[0160] At the second time 645, the negative output signal 620 leaves the operating saturation region and enters the operating linear region. At the third time 650, the negative output signal 620 leaves the operating linear region and enters the operating saturation region. However, between times 645 and 650, the negative output signal 620 decreases linearly.

[0161] Advantageously, Figure 2 and 3B The feedforward circuit system 230 supplies the negative output signal 620 to Figure 2 and 3B The combined circuit system 225. Advantageously, taking into account the operating linear region, the feedforward circuit system 230 combines the negative output signal 620 and the signal from... Figure 2 and 3B The error signal of the modulator circuit system 220. Advantageously, considering the linearity between times 645 and 650, Figure 2 and 3A The comparator circuit system 235 modulates the combined signal from the feedforward circuit system 230. Advantageously, the Class D amplifier circuit system 130 adjusts the positive output signal 615 to compensate for the linearity of the Class AB amplifier circuit system 140.

[0162] Figure 7 yes Figure 2 and 3A The timing diagram 700 shows an example operation of the comparator circuit system 235. Figure 7 In the example, timing diagram 700 shows Figure 3A The triangular signal 375 Figure 6The positive output signal 615 and the example combined error signal 720. As described above, the triangular signal 375 is a triangular waveform whose frequency determines the switching frequency of the positive output signal 615. Although in Figure 7 In the example, the triangular signal 375 has a first frequency, but the triangular signal 375 can be modified to have a second frequency.

[0163] The combined error signal 720 is Figure 2 and 3B A diagram illustrating an example output of the combinational circuit system 225. In some of the described examples, the combinational error signal 720 includes signals from... Figure 2 and 3B The error signal of the modulator circuit system 220 and from Figure 2 and 3B Feedforward circuit system 230 Figure 6 The negative output signal 620. In some examples, the feedforward circuit system 230 amplifies the negative output signal 620 with a gain of less than one to reduce the logic level of the negative output signal 620.

[0164] exist Figure 3A In the example, Figure 3A The sixth amplifier 374 compares the combined error signal 720 and the triangular signal 375. The sixth amplifier 374 generates a modulated signal in response to the comparison. When supplied to... Figure 2 and 3A When the first output stage circuit system 240 is activated, the modulated signal is converted into a positive output signal 615.

[0165] Advantageously, the comparator circuit system 235 compares the triangular signal 375 with the combination error signal 720 to generate a modulated signal with a varying duty cycle. The duty cycle of the positive output signal 615 is represented by a discrete waveform, which reflects the amplitude of the combination error signal 720. Advantageously, the discrete waveform of the positive output signal 615 improves power efficiency by reducing linear operating conditions.

[0166] Figure 8 yes Figure 1 and 2 The graph 800 shows an example operation of the multi-class modulation circuit system 110 at a fixed output power. Figure 8In the example, graph 800 shows an example total harmonic distortion (THD) 820 across a frequency range. THD 820 is a performance characteristic of the output of the multi-class modulation circuitry system 110. THD 820 shows the suppression factor of the multi-class modulation circuitry system 110. Before the first frequency 840, THD 820 is approximately a constant value. After the first frequency 840, THD 820 decreases. Advantageously, the audible sound range is after the first frequency 840. Advantageously, the multi-class modulation circuitry system 110 has a relatively low THD for applications targeting frequencies within the audible noise range, for example... Figure 1 The audio system 100.

[0167] Figure 9 yes Figure 1 and 2 Graph 900 shows example operations of the multi-class modulation circuit system 110 at various power levels. Figure 9 In the example, graph 900 includes a first example THD 920, a second example THD 940, and a third example THD 960. THDs 920, 940, and 960 illustrate the multi-class modulation circuit system 110 for... Figures 1-4 The operation of different variations of resistors 120 and 125.

[0168] exist Figure 9 In the examples, the first THD 920 shows the THD characteristics of the multi-class modulation circuit system 110 when resistors 120 and 125 have exactly the same resistance. The second THD 940 shows the THD characteristics of the multi-class modulation circuit system 110 when there is approximately one percent mismatch between the resistances of resistors 120 and 125. The third THD 960 shows the THD characteristics of the multi-class modulation circuit system 110 when there is approximately five percent mismatch between the resistances of resistors 120 and 125.

[0169] Below the power threshold of 980, the THDs 920, 940, and 960 are approximately the same. Advantageously, the implementation of the multi-class modulation circuit system 110 supplying signals below the power threshold of 980 has higher tolerances for resistors 120 and 125. However, above the power threshold of 980, the mismatch between resistors 120 and 125 increases the THD of the multi-class modulation circuit system 110. Advantageously, reducing the mismatch between resistors 120 and 125 improves the THD of the multi-class modulation circuit system 110.

[0170] Figure 10 yes Figure 1 and 2 A multi-class modulation circuit system 110 spans an output power level range with and without Figure 2 and 3BThe example operation of the feedforward circuit system 230 is shown in Figure 1000. Figure 10 In the example, graph 1000 includes a first example THD performance 1020 and a second example THD performance 1040. The first THD performance 1020 shows the THD of the multi-class modulation circuit system 110 without the feedforward circuit system 230. The second THD performance 1040 shows the THD of the multi-class modulation circuit system 110 with the feedforward circuit system 230.

[0171] Before the first power level 1060, the THD performances 1020 and 1040 are substantially the same. After the first power level 1060 and before the second power level 1080, the second THD performance 1040 decreases in response to the feedforward circuitry system 230. After the second power level 1080, the THD performances 1020 and 1040 are substantially the same. Advantageously, including the feedforward circuitry system 230 improves the THD of the multi-class modulation circuitry system 110.

[0172] Figure 11A and 11B The formation indicates that it can be executed. Figure 1 and 2 A flowchart of an example operation 1100 of the multi-class modulation circuit system 110. The example operation 1100 in Figure 11 begins at block 1104, where… Figure 1 and 2 The multi-class modulation circuit system 110 receives a first input signal and a second input signal. In some examples, Figure 1 The audio source 105 supplies a differential input signal with a positive input signal (INP) and a negative input signal (INM) to the multi-class modulation circuit system 110. In this type of example, Figures 1-4 The regulating circuit systems 115 and 135 can receive differential input signals.

[0173] The regulating circuit systems 115 and 135 filter the first and second input signals (box 1108). In some examples, the regulating circuit systems 115 and 135 are low-pass filters. In such examples, the regulating circuit systems 115 and 135 average signals with relatively high frequencies, such as noise. For example, the regulating circuit systems 115 and 135 may filter inaudible frequencies, such as frequencies greater than twenty kilohertz (kHz).

[0174] Figure 2The amplifier circuit system 260 determines the difference between the first input signal and the second input signal (Box 1112). In some examples, the amplifier circuit system 260 converts the differential input signal into a single-ended signal. In such examples, the amplifier circuit system 260 determines the difference by subtracting the positive input signal from the negative input signal.

[0175] Amplifier circuitry 260 amplifies the difference (Box 1116). In some examples, amplifier circuitry 260 amplifies a single-ended version of the differential input signal by a gain. In such examples, the gain of amplifier circuitry 260 is a relatively high gain that saturates the output of amplifier circuitry 260. For example, amplifier circuitry 260 clips the output signal to supply a value in response to multiplying the single-ended signal by a gain of eighty. In this example, the output of amplifier circuitry 260 operates in linear mode for a relatively small voltage range near the common potential.

[0176] Figure 2 and 4 The second output stage circuitry 265 generates the first output signal based on the amplified difference (Box 1120). In some examples, the amplifier circuitry 260 supplies a nearly saturated output signal to the second output stage circuitry 265 to generate a negative output signal operating in a nearly saturated mode. In such examples, the negative output signal is in the linear region (e.g., in...). Figure 6 The duration (between 645 and 650) is relatively short. Advantageously, reducing the duration in the linear operating region improves power efficiency.

[0177] Figure 2 and 3B The feedforward circuitry system 230 scales the first output signal to generate a feedforward signal (Box 1124). In some examples, the feedforward circuitry system 230 amplifies the negative output signal with a gain less than one to scale the negative output signal. In such examples, the gain of the feedforward circuitry system 230 converts the power level of the negative output signal into... Figure 2 and 3B The power level of the combined circuit system 225.

[0178] The first regulating circuit system 115 combines the first and second input signals with the first and second output signals (box 1128). In some examples, Figures 1-4 The components of the first regulating circuit system 115 and / or resistors 120, 125 are summing resistors. In such examples, the first regulating circuit system 115 and / or resistors 120, 125 combine input signal differential pairs and output signal differential pairs from resistors 120, 125.

[0179] Figure 2and 3B The output detection circuitry 245 determines whether the resistance of the load is less than a threshold (Box 1132). In some examples, the output detection circuitry 245 determines the resistance of the speaker 160 and / or the line output 170 by setting the positive output signal to a fixed voltage. In such examples, the output detection circuitry 245 determines the resistance based on the voltage of the negative output signal in response to the fixed voltage of the positive output signal. The output detection circuitry 245 compares the determined resistance with a threshold resistance to determine whether the filter circuitry 150 is coupled to the speaker 160 or to the line output 170.

[0180] If the output detection circuitry 245 determines that the load resistance is less than a threshold (e.g., box 1132 returns a result "Yes"), then Figure 2 and 3B The modulator circuitry 220 applies a third-order transfer function to the combined signal to determine the error signal (Box 1136). In some examples, the output detection circuitry 245 configures the modulator circuitry 220 to implement the third-order transfer function. For example, the output detection circuitry 245 is closed. Figure 3B Switches 318, 320, 332, 334, 342, 346, 354, and 356 are disconnected. Figure 3B Switches 324, 326, 333, and 335 will... Figure 3B The resistance of the variable resistors 358 and 363 is set to the first value, and the resistance of the variable resistors is set to the first value. Figure 4 The resistances of the variable resistors 415 and 425 are set to a first value. In this type of example, the modulator circuit system 220 filters the combined signal from the first regulation circuit system 115 and / or suppresses the difference between the input signal differential pair and the output signal differential pair.

[0181] Turning Figure 11B If the output detection circuitry 245 determines that the load resistance is greater than a threshold (e.g., block 1132 returns a result of "No"), then the modulator circuitry 220 applies a second-order transfer function to the combined signal to determine an error signal (block 1140). In some examples, the output detection circuitry 245 configures the modulator circuitry 220 to implement the second-order transfer function. For example, the output detection circuitry 245 opens switches 318, 320, 332, 334, 342, 346, 354, 356 and closes switches 324, 326, 333, 335, setting the resistances of variable resistors 358, 363 to a second value, and setting the resistances of variable resistors 415, 425 to a second value. The second value reduces... Figure 2 and 4The gain of the amplifier circuit system 260. In such an example, the modulator circuit system 220 filters the combined signal from the first conditioning circuit system 115 and / or suppresses the difference between the input signal differential pair and the output signal differential pair.

[0182] The feedforward circuitry 230 combines the error signal and the scaled first output signal (box 1144). In some examples, the feedforward circuitry 230 determines to convert the error signal from the modulator circuitry 220 into a single-ended error signal. Advantageously, the combined error signal from the feedforward circuitry 230 takes into account the error determined by the modulator circuitry 220 and the negative output signal.

[0183] Figure 2 and 3A The comparator circuit system 235 compares the combination error signal with a triangular waveform (box 1148). In some examples, the comparator circuit system 235 compares the combination error signal with... Figure 3A and 7 A triangular signal 375 is used to generate a square wave waveform with a varying duty cycle. In this example, the variation in the duty cycle of the square wave waveform represents the amplitude of the combined error signal during the period of the triangular signal 375.

[0184] Figure 2 and 3A The first output stage circuitry 240 generates a second output signal based on a comparison (Box 1152). In some examples, the first output stage circuitry 240 is driven by a square wave waveform from the comparator circuitry 235. Figure 3A The transistors of the power stage circuit system 379. In this type of example, the switching of the power stage circuit system 379 is generated. Figure 6 and 7 The positive output signal is 615.

[0185] Amplifier circuit systems 130 and 140 supply the first and second output signals to the filter circuit system (box 1156). In some examples, output stage circuit systems 240 and 265 will... Figure 6 Output signals 615 and 620 are supplied to Figure 1 and 2 The filter circuit system 150. In such an example, the filter circuit system 150 supplies output signals 615, 620 to one of the speaker 160 or line output 170.

[0186] Although reference Figure 11A and 11BThe flowchart shown illustrates an example method; however, many other methods of implementing the multi-class modulation circuit system 110 may be used alternatively according to this specification. For example, the execution order of the blocks may be changed, and / or some of the blocks described may be altered, eliminated, or combined. Similarly, additional operations may be included in the manufacturing process before, between, or after the blocks shown in the illustrated example.

[0187] In this specification, the term "and / or" (when used in the form of, for example, A, B, and / or C) means any combination or subset of A, B, and C, such as: (a) only A; (b) only B; (c) only C; (d) A and B; (e) A and C; (f) B and C; and (g) A, B, and C. Furthermore, as used herein, the phrase "at least one of A or B" (or "at least one of A and B") means an embodiment comprising any one of: (a) at least one A; (b) at least one B; and (c) at least one A and at least one B.

[0188] In this specification, the term "coupled" may cover a connection, communication, or signal path that supports a functional relationship consistent with this specification. For example, if device A generates a signal to control device B to perform an action, then: (a) in a first example, device A is coupled to device B via a direct connection; or (b) in a second example, device A is coupled to device B via an intermediate component C, but the intermediate component C does not change the functional relationship between device A and device B such that device B is controlled by the control signal generated by device A.

[0189] Numerical identifiers, such as "first," "second," and "third," are used only to distinguish elements of substantially the same type in terms of structure and / or function. These identifiers used in the detailed description are not necessarily identical to those used in the claims.

[0190] A device “configured” to perform a task or function can be configured (e.g., programmed and / or hardwired) at the time of manufacture to perform the function, and / or can be configured (or reconfigured) by a user after manufacture to perform the function and / or other additional or alternative functions. Configuration can be performed through firmware and / or software programming of the device, through the construction and / or arrangement of hardware components and the interconnection of the device, or through a combination of these operations.

[0191] As used herein, the terms “terminal,” “node,” “interconnect,” “pin,” and “lead” are used interchangeably. Unless explicitly stated otherwise, these terms are generally used to refer to interconnections or ends between device elements, circuit elements, integrated circuits, devices, or other electronic or semiconductor components.

[0192] The circuits or devices described herein as containing specific components may actually be adapted to be coupled to those components to form the described circuit system or device. For example, a structure described as containing one or more semiconductor elements (e.g., transistors), one or more passive elements (e.g., resistors, capacitors, and / or inductors), and / or one or more sources (e.g., voltage and / or current sources) may actually contain only semiconductor elements within a single physical device (e.g., a semiconductor die and / or integrated circuit (IC) package) and may be adapted to be coupled to at least some passive elements and / or sources during or after manufacturing, for example, by an end user and / or a third party, to form the described structure.

[0193] The circuits described herein can be reconfigured to include the replaced components to provide functionality at least partially similar to that available before the component replacement. Unless otherwise stated, components shown as resistors generally represent any one or more elements coupled in series and / or parallel to provide the impedance represented by the resistor shown. For example, a resistor or capacitor shown and described herein as a single component can actually be multiple resistors or capacitors coupled in parallel between the same nodes. For example, a resistor or capacitor shown and described herein as a single component can actually be multiple resistors or capacitors coupled in series between the same two nodes as the single resistor or capacitor. While some components in the described examples are included in the integrated circuit, and other components are outside the integrated circuit, in other example embodiments, additional or fewer features may be incorporated into the integrated circuit. Additionally, some or all features shown as outside the integrated circuit may be included in the integrated circuit, and / or some features shown as inside the integrated circuit may be incorporated outside the integrated circuit. As used herein, the term "integrated circuit" refers to one or more of the following circuits: (i) integrated in / on a semiconductor substrate; (ii) incorporated in a single semiconductor package; (iii) incorporated in the same module; and / or (iv) incorporated in / on the same printed circuit board.

[0194] The use of the phrase "ground" in the foregoing description includes chassis grounding, earth grounding, floating grounding, virtual grounding, digital grounding, common grounding, and / or any other form of grounding connection applicable to or suitable for the teachings of this specification. Unless otherwise stated, "approximately," "roughly," or "substantially" preceding a value indicates + / - 10% of the value, or, if the value is zero, a reasonable range of values ​​near zero.

[0195] Within the scope of the claims, the described embodiments may be modified, and other embodiments are possible.

Claims

1. An apparatus comprising: A Class D amplifier circuit system having a first input, a second input, a third input, and an output, wherein the first input of the Class D amplifier circuit system is coupled to the output of the Class D amplifier circuit system; as well as An AB-class amplifier circuit system has a first input, a second input, a third input, and an output. The first input of the AB-class amplifier circuit system is coupled to the first input and the output of the D-class amplifier circuit system. The second and third inputs of the AB-class amplifier circuit system are coupled to the second and third inputs of the D-class amplifier circuit system and the output of the AB-class amplifier circuit system.

2. The device according to claim 1, further comprising: A filter circuit system having a first terminal, a second terminal, a third terminal, and a fourth terminal, wherein the first terminal of the filter circuit system is coupled to the output of the Class D amplifier circuit system, the first input of the Class D amplifier circuit system, and the first input of the Class AB amplifier circuit system; and the second terminal of the filter circuit system is coupled to the output of the Class AB amplifier circuit system, the second input of the Class D amplifier circuit system, the third input of the Class D amplifier circuit system, the first input of the Class AB amplifier circuit system, and the third input of the Class AB amplifier circuit system. as well as A loudspeaker having a first terminal and a second terminal, the first terminal of the loudspeaker being coupled to the third terminal of the filter circuit system, and the second terminal of the loudspeaker being coupled to the fourth terminal of the filter circuit system.

3. The device according to claim 1, wherein the Class D amplifier circuit system comprises: A modulator circuit system having a first input, a second input, a first output, and a second output, wherein the first input of the modulator circuit system is coupled to the output of the Class D amplifier circuit system and the first input of the Class AB amplifier circuit system, and the second input of the modulator circuit system is coupled to the output of the Class AB amplifier circuit system, the third input of the Class D amplifier circuit system, the first input of the Class AB amplifier circuit system, and the third input of the Class AB amplifier circuit system. as well as A combinational circuit system having a first input and a second input, the first input of the combinational circuit system being coupled to a first output of the modulator circuit system, and the second input of the combinational circuit system being coupled to a second output of the modulator circuit system.

4. The device of claim 3, wherein the combined circuit system further has an output, and the Class D amplifier circuit system further comprises: A feedforward circuit system having a first input, a second input, and an output, wherein the first input of the feedforward circuit system is coupled to the output of the combined circuit system, and the second input of the feedforward circuit system is coupled to the output of the Class AB amplifier circuit system; A comparator circuit system having an input and an output, wherein the input of the comparator circuit system is coupled to the output of the feedforward circuit system; as well as An output stage circuit system having an input and an output, wherein the input of the output stage circuit system is coupled to the output of the comparator circuit system, and the output of the output stage circuit system is coupled to the first input of the class AB amplifier circuit system and the first input of the modulator circuit system.

5. The device of claim 1, further comprising a current digital-to-analog converter (IDAC) having a first terminal and a second terminal, the first terminal of the IDAC being coupled to a first input of the Class D amplifier circuit system, the output of the Class D amplifier circuit system, and the first input of the Class AB amplifier circuit system, the second terminal of the IDAC being coupled to a second input of the Class D amplifier circuit system, a third input of the Class D amplifier circuit system, a second input of the Class AB amplifier circuit system, a third input of the Class AB amplifier circuit system, and the output of the Class AB amplifier circuit system.

6. The device according to claim 1, wherein the Class AB amplifier circuit system comprises: An amplifier circuit system having a first input, a second input, and an output, wherein the first input of the amplifier circuit system is coupled to the first input of the Class D amplifier circuit system and the output of the Class D amplifier circuit system, and the second input of the amplifier circuit system is coupled to the second input of the Class D amplifier circuit system, the third input of the Class AB amplifier circuit system, and the output of the Class AB amplifier circuit system; as well as An output stage circuit system having an input and an output, wherein the input of the output stage circuit system is coupled to the output of the amplifier circuit system, and the output of the output stage circuit system is coupled to the second input and the third input of the Class D amplifier circuit system.

7. The device of claim 6, wherein the input of the amplifier circuit system is a first input, the Class AB amplifier circuit system further comprising a gain selection circuit system having a first terminal and a second terminal, the first terminal of the gain selection circuit system being coupled to the second input of the Class D amplifier circuit system and the output of the output stage circuit system, and the second terminal of the gain selection circuit system being coupled to the second input of the amplifier circuit system.

8. An apparatus comprising: A first amplifier circuit system has a first input, a second input, and an output; as well as The second amplifier circuit system includes: A modulator circuit system having a first input, a second input, a first output, and a second output, wherein the first input of the modulator circuit system is coupled to the first input and the output of the first amplifier circuit system, and the second input of the modulator circuit system is coupled to the second input of the first amplifier circuit system. A combinational circuit system having a first input, a second input, and an output, wherein the first input of the combinational circuit system is coupled to the first output of the modulator circuit system, and the second input of the combinational circuit system is coupled to the second output of the modulator circuit system; A feedforward circuit system having a first input, a second input, and an output, wherein the first input of the feedforward circuit system is coupled to the output of the combined circuit system, and the second input of the feedforward circuit system is coupled to the output of the first amplifier circuit system; A comparator circuit system having an input and an output, wherein the input of the comparator circuit system is coupled to the output of the feedforward circuit system; as well as An output stage circuit system having an input and an output, wherein the input of the output stage circuit system is coupled to the output of the comparator circuit system, and the output of the output stage circuit system is coupled to the first input of the first amplifier and the first input of the modulator circuit system.

9. The device of claim 8, wherein the modulator circuit system comprises: A first amplifier has a first input, a second input, a first output, and a second output, wherein the first input of the first amplifier is coupled to the first input and the output of the first amplifier circuit system, and the second input of the first amplifier is coupled to the second input of the first amplifier circuit system and the output of the output stage circuit system. A first resistor having a first terminal and a second terminal, wherein the first terminal of the first resistor is coupled to the first output of the first amplifier; A second resistor having a first terminal and a second terminal, wherein the first terminal of the second resistor is coupled to the second output of the first amplifier; as well as A second amplifier has a first input and a second input, the first input of the second amplifier being coupled to the second terminal of the first resistor, and the second input of the second amplifier being coupled to the second terminal of the second resistor.

10. The device of claim 9, wherein the modulator circuit system further comprises: A first capacitor has a first terminal and a second terminal. The first terminal of the first capacitor is coupled to the first input of the first amplifier circuit system, the output of the first amplifier circuit system, and the first input of the first amplifier. The second terminal of the first capacitor is coupled to the first output of the first amplifier and the first terminal of the first resistor. as well as A second capacitor has a first terminal and a second terminal. The first terminal of the second capacitor is coupled to the second input of the first amplifier circuit system, the output of the output stage circuit system, and the second input of the first amplifier. The second terminal of the second capacitor is coupled to the second output of the first amplifier and the first terminal of the second resistor.

11. The device of claim 8, wherein the modulator circuit system further comprises a third output, a fourth output, a fifth output, and a sixth output, and the combined circuit system comprises: A first resistor having a first terminal and a second terminal, wherein the first terminal of the first resistor is coupled to the first output of the modulator circuit system; A second resistor having a first terminal and a second terminal, wherein the first terminal of the second resistor is coupled to the second output of the modulator circuit system; as well as An amplifier having a first input, a second input, and an output, wherein the first input of the amplifier is coupled to a second terminal of a first resistor, the second input of the amplifier is coupled to a second terminal of a second resistor, and the output of the amplifier is coupled to the first input of the feedforward circuit system.

12. The device of claim 8, wherein the input of the comparison circuit system is a first input of the comparison circuit system, the comparison circuit system further having a second input coupled to a triangular signal, the comparison circuit system being configured to compare the output of the combined circuit system with the triangular signal.

13. The device of claim 8, wherein the combined circuit system further has a third input, the device further includes a third amplifier circuit system having an input and an output, the input of the third amplifier circuit system being coupled to the first input of the first amplifier circuit system, the output of the first amplifier circuit system and the first input of the modulator circuit system, and the output of the third amplifier circuit system being coupled to the third input of the combined circuit system.

14. The device of claim 8, wherein the first amplifier circuit system is a Class AB amplifier and the second amplifier circuit system is a Class D amplifier.

15. An apparatus comprising: A first amplifier circuit system has a first input, a second input, and an output; as well as The second amplifier circuit system includes: A third amplifier circuit system has a first input, a second input, and an output, wherein the first input of the third amplifier circuit system is coupled to the first input and the output of the first amplifier circuit system, and the second input of the third amplifier circuit system is coupled to the second input of the first amplifier circuit system. as well as An output stage circuit system having an input and an output, wherein the input of the output stage circuit system is coupled to the output of the third amplifier circuit system, and the output of the output stage circuit system is coupled to the second input of the first amplifier circuit system.

16. The device of claim 15, wherein the second amplifier circuit system further comprises a gain selection circuit system having a first terminal and a second terminal, the first terminal of the gain selection circuit system being coupled to the second input of the first amplifier circuit system and the output of the output stage circuit system, and the second terminal of the gain selection circuit system being coupled to the third input of the third amplifier circuit system.

17. The device of claim 15, wherein the output of the third amplifier circuit system is a first output of the third amplifier circuit system, the output stage circuit system comprising: A level shifting circuit system having a first input, a second input, a first output, and a second output, wherein the first input is coupled to the first output of the third amplifier circuit system, and the second input is coupled to the second output of the third amplifier circuit system; as well as A power stage circuit system having a first input, a second input, and an output, wherein the first input of the power stage circuit system is coupled to the first output of the level shifting circuit system, the second input of the power stage circuit system is coupled to the second output of the power stage circuit system, and the output of the power stage circuit system is coupled to the second input of the first amplifier circuit system.

18. The device of claim 17, wherein the level shifting circuit system comprises: A fourth amplifier circuit system having an input and an output, the input of the fourth amplifier circuit system being coupled to the first output of the third amplifier circuit system, the output of the fourth amplifier circuit system being coupled to the first input of the power stage circuit system, the fourth amplifier circuit system being used to shift the voltage of the first output of the third amplifier circuit system with reference to the supply voltage; as well as A fifth amplifier circuit system having an input and an output, the input of the fifth amplifier circuit system being coupled to the second output of the third amplifier circuit system, the output of the fifth amplifier circuit system being coupled to the second input of the power stage circuit system, the fifth amplifier circuit system being used to shift the voltage of the first output of the third amplifier circuit system with reference to a common potential.

19. The device of claim 17, wherein the power stage circuit system comprises: A first transistor having a first terminal and a control terminal, wherein the control terminal of the first transistor is coupled to the first output of the level shifting circuit system; as well as The second transistor has a first terminal and a control terminal, the first terminal of the second transistor being coupled to the first terminal of the first transistor and the second input of the first amplifier circuit system, and the control terminal of the second transistor being coupled to the second output of the level shifting circuit system.

20. The device of claim 15, wherein the first amplifier circuit system is a Class D amplifier circuit system and the second amplifier circuit system is a Class AB amplifier circuit system.

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