Class D audio amplifier and modulation method thereof
By employing triangular wave reshaping and pulse width modulation techniques in Class D audio amplifiers, and using reshaping triangular waves to replace the original triangular waves for modulation, the problem of high switching losses in traditional Class D audio amplifiers is solved, achieving higher energy efficiency.
Patent Information
- Application Number
- CN202410574291.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-10
- Publication Date
- 2025-11-11
AI Technical Summary
Traditional Class D audio amplifiers have significant switching losses, which cause the power stage to frequently turn on and off, increasing energy consumption.
By employing triangular wave reshaping and pulse width modulation techniques, a second triangular wave is generated by reshaping the triangular wave. This second triangular wave is then used to modulate the differential audio input wave, reducing the number of switching operations and lowering switching losses.
Achieving a single duty cycle in each cycle reduces switching losses in Class D audio amplifiers and improves energy efficiency.
Smart Images
Figure CN120934469A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to a Class D audio amplifier and its modulation method. More specifically, this disclosure relates to a Class D audio amplifier with less switching loss and its modulation method. Background Technology
[0002] Figure 1 This illustrates the working principle of a conventional Class D audio amplifier. For example... Figure 1 As shown, a conventional Class D audio amplifier uses a pair of differential audio input waves (shown as "IN") to... + "and "IN - The input signals are compared with a triangular wave to modulate the differential audio input waves, generating two pulse-width modulation (PWM) waves (shown as "W1" and "W2") with different widths. A conventional Class-D audio amplifier then differentially modulates these two PWM waves using an exclusive OR operation to generate a single pulse wave for output (shown as "W3"). This results in two duty cycles within each cycle of the triangular wave, meaning that a power stage of the conventional Class-D audio amplifier must be turned on and off twice for each of these two duty cycles. The more times the power stage is turned on and off, the greater the losses (called switching losses) of the conventional Class-D audio amplifier. Therefore, reducing the switching losses of the conventional Class-D audio amplifier is crucial in this technique. Summary of the Invention
[0003] To at least overcome the aforementioned problems, this disclosure provides a Class D audio amplifier. The Class D audio amplifier may include a triangle wave generator, a waveform reshaping device, and a pulse width modulator. The waveform reshaping device may be electrically connected to the triangle wave generator directly or indirectly, and the pulse width modulator may be electrically connected to the waveform reshaping device directly or indirectly. The triangle wave generator is used to generate a first triangle wave. The waveform reshaping device is used to generate a second triangle wave by reshaping the first triangle wave, and the slope of the second triangle wave is the same as the slope of the first triangle wave. The pulse width modulator is used to alternately or simultaneously modulate a pair of differential audio input waves using the second triangle wave instead of the first triangle wave, thereby reducing all commutation losses of the Class D audio amplifier. In the proposed Class D audio amplifier, the start of each cycle of the second triangular wave is when the amplitude of the first triangular wave becomes equal to the amplitude of a negative audio input wave of the pair of differential audio input waves, and the peak of each cycle of the second triangular wave is when the amplitude of the second triangular wave becomes equal to the amplitude of a positive audio input wave of the pair of differential audio input waves, or when the first triangular wave begins to decline.
[0004] To at least overcome the aforementioned problems, this disclosure also provides a modulation method for a Class D audio amplifier. The modulation method may include the following steps: generating a first triangular wave using a triangular wave generator; reshaping the first triangular wave using a waveform reshaping device to generate a second triangular wave, wherein the slope of the second triangular wave is the same as that of the first triangular wave; and modulating a pair of differential audio input waves using a pulse width modulator instead of the first triangular wave to reduce all switching losses of the Class D audio amplifier. In the proposed modulation method, the start of each cycle of the second triangular wave is when the amplitude of the first triangular wave becomes equal to the amplitude of a negative audio input wave of the pair of differential audio input waves, and the peak of each cycle of the second triangular wave is when the amplitude of the second triangular wave becomes equal to the amplitude of a positive audio input wave of the pair of differential audio input waves, or when the first triangular wave begins to decline.
[0005] Unlike traditional Class D audio amplifiers that use a first triangular wave (i.e., a regular triangular wave) to modulate the pair of differential audio inputs (resulting in two duty cycles in each cycle of the first triangular wave), the proposed Class D audio amplifier uses a second triangular wave (i.e., a reshaped triangular wave) instead of the first triangular wave to modulate the pair of differential audio inputs. This achieves a single duty cycle in each cycle of the second triangular wave, which is equivalent to the integration of two duty cycles, thereby reducing all losses in the Class D audio amplifier.
[0006] This invention is not intended to limit the scope of the claimed invention, but merely to provide a basic overview. Details of the invention will be illustrated by the various embodiments presented below. Attached Figure Description
[0007] Figure 1 A waveform diagram illustrating the working principle of a conventional Class D audio amplifier is provided.
[0008] Figure 2A A schematic diagram illustrating a Class D audio amplifier according to some embodiments of the present disclosure is shown.
[0009] Figure 2B Provided Figure 2A The waveform diagram shows how a Class D audio amplifier generates a PWM wave.
[0010] Figure 3A A schematic diagram illustrating a Class D audio amplifier according to some other embodiments of the present disclosure.
[0011] Figure 3B Provided Figure 3A The waveform diagram shows how a Class D audio amplifier generates a PWM wave.
[0012] Figure 4 A flowchart illustrating a modulation method for a Class D audio amplifier according to some embodiments of the present disclosure is shown.
[0013] [Symbol Explanation]
[0014] 1. Class D audio amplifier
[0015] 4: Modulation method
[0016] 10: Power Stage
[0017] 11: Triangular Wave Generator
[0018] 13, 33: Waveform reshaping device
[0019] 15: Pulse Width Modulator
[0020] 17: Multiplexer
[0021] 17A: First Multiplexer
[0022] 17B: Second Multiplexer
[0023] 19: Logic Controller
[0024] 20: Comparator
[0025] 20A: First comparator
[0026] 20B: Second comparator
[0027] 30, 60: Triggers
[0028] 41, 43, 45: Steps
[0029] 50: First Triangular Wave
[0030] 52: Second Triangular Wave
[0031] IN + Positive audio input wave / Differential audio input wave
[0032] IN - Negative audio input wave / Differential audio input wave
[0033] OUT + First pulse wave
[0034] OUT - Second pulse wave
[0035] W1, W2: Pulse Width Modulation (PWM) Waves
[0036] W3, W11, W12, W21, W22: Pulse waves
[0037] ZC: Zero Crossing Signal Detailed Implementation
[0038] The embodiments disclosed below are not intended to limit the claimed invention to any particular environment, application, structure, process, or situation. Elements not directly related to the claimed invention are not illustrated in the drawings. The dimensions and dimensional relationships between the various elements in the drawings are merely exemplary examples and are not intended to limit the claimed invention. Unless otherwise stated, the same element numbers may correspond to the same elements in the following description without being inconsistent with the claimed invention.
[0039] The terminology used herein is for illustrative purposes only and is not intended to limit the scope of the claimed invention. Unless the context clearly indicates otherwise, the singular form “a (a and an)” is intended to include the plural form as well. The terms “comprises / comprising,” “includes / including,” etc., indicate the presence of the stated features, integers, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, operations, elements, components, and / or groups thereof. The term “and / or” includes any and all combinations of one or more of the related listings. Although the terms “first,” “second,” and “third,” etc., may be used herein to describe various elements, such elements should not be limited by these terms. These terms are used only to distinguish individual elements. Thus, by example, a first element described below may also be referred to as a second element without departing from the spirit and scope of the claimed invention.
[0040] Figure 2A A schematic diagram illustrating a Class D audio amplifier according to some embodiments of the present disclosure is shown. Figure 2B Provided Figure 2A The waveform diagram shows how a Class D audio amplifier generates a PWM wave. Figure 2A and Figure 2B The contents shown are provided only to illustrate embodiments of this disclosure and should not be construed as any limitation on the claimed invention.
[0041] Reference Figure 2AThis invention proposes a Class D audio amplifier 1. The Class D audio amplifier 1 may include, for example, a triangle wave generator 11, a waveform reshaping device 13, a pulse width modulator 15, and a power stage 10. In some embodiments, the Class D audio amplifier 1 may further include a multiplexer 17 and a logic controller 19 to alternately input and output a pair of differential waves. The triangle wave generator 11, waveform reshaping device 13, pulse width modulator 15, multiplexer 17, logic controller 19, and power stage 10 may be electrically connected to each other directly or indirectly. The power stage 10 can be used to output pulse waves to drive a loudspeaker (not shown).
[0042] The multiplexer 17 may include two input terminals and one output terminal, and the two input terminals are used to receive a pair of differential audio input waves, the pair of differential audio input waves including a positive audio input wave IN. + and a negative audio input wave IN - Furthermore, the output of multiplexer 17 is used to alternately output a negative audio input wave IN based on a zero-crossing signal ZC. - Or positive audio input wave IN + The zero-crossing signal ZC is used to switch voltage polarity, for example, from a positive value to a negative value, or from a negative value to a positive value. For instance, multiplexer 17 can be used to output the negative audio input wave IN of the pair of differential audio input waves during the first half of the cycle. - During the second half of the cycle, the positive audio input wave of the differential audio input wave is output.
[0043] The triangular wave generator 11 can be implemented as any of various known triangular wave generators and used to generate a first triangular wave 50.
[0044] The waveform reshaping device 13 can be used to generate a second triangular wave 52 by reshaping a first triangular wave 50, wherein the slope of the second triangular wave 52 is the same as the slope of the first triangular wave 50. For example, the waveform reshaping device 13 may include a comparator 20 and a trigger 30. Figure 2A As shown, comparator 20 is electrically connected to triangular wave generator 11, multiplexer 17 and trigger 30, while trigger 30 is electrically connected to triangular wave generator 11, comparator 20 and pulse width modulator 15.
[0045] Reference Figures 2A to 2B Comparator 20 can be used to compare the amplitude of the first triangular wave 50 generated by the triangular wave generator 11 with the negative audio input wave IN of the pair of differential audio input waves. - Or positive audio input wave IN + The amplitudes are compared. For example, when multiplexer 17 is in the first half of the cycle, it compares the negative audio input wave IN of the pair of differential audio input waves.- When the output is sent to comparator 20, comparator 20 compares the amplitude of the first triangular wave 50 with the negative audio input wave IN. - The amplitudes are compared. Similarly, when multiplexer 17 is in the second half of the cycle, the positive audio input wave IN of the pair of differential audio input waves is compared. + When the output is sent to comparator 20, comparator 20 compares the amplitude of the first triangular wave 50 with the positive audio input wave IN. + The amplitudes were compared.
[0046] Reference Figures 2A to 2B The trigger 30 can be any of various known triggers (e.g., an SR (set-reset) trigger), and the start of each cycle of the second triangular wave 52 is determined based on the output of the comparator 20, while the peak of each cycle of the second triangular wave 52 is determined based on the time when the first triangular wave 50 begins to fall. In other words, under the control of the trigger 30, the start of each cycle of the second triangular wave 52 is when the amplitude of the first triangular wave 50 becomes equal to the negative audio input wave IN of the pair of differential audio input waves. - When the amplitude is such that the peak of each cycle of the second triangular wave 52 is when the first triangular wave 50 begins to decline.
[0047] Reference Figures 2A to 2B The pulse width modulator 15 can be used to modulate the pair of differential audio input waves using a second triangular wave 52 instead of a first triangular wave 50, thereby reducing all switching losses of the Class D audio amplifier 1. For example, the pulse width modulator 15 may include a comparator (not shown) that alternately modulates the second triangular wave 52 with the negative audio input wave IN of the pair of differential audio input waves. - and positive audio input wave IN + The comparisons are made to generate the corresponding pulse waves.
[0048] Reference Figures 2A to 2B The logic controller 19 can be used to alternately output a first pulse wave OUT. + and a second pulse wave OUT - A pair of pulse waves are output to power stage 10 to drive a loudspeaker (not shown). The negative audio input wave IN is then converted to a signal by multiplexer 17. - In the case where the output is sent to comparator 20, logic controller 19 will output the second pulse wave OUT. + The output is sent to power stage 10. The positive audio input wave IN is then converted to a multiplexer 17. + In the case where the output is sent to comparator 20, logic controller 19 will output the first pulse wave OUT. - Output to power stage 10.
[0049] like Figure 2BAs shown, this invention proposes a pair of pulse waves W11. The negative audio input wave IN is modulated by a pulse width modulator 15. - A pulse wave W11 is generated by comparing it with the second triangular wave 52, while the positive audio input wave IN is generated by the pulse width modulator 15. + A pulse wave W12 is generated by comparing it with the second triangular wave 52. During the first half of each cycle of the differential audio input waves, pulse wave W11 presents a series of pulses with different widths, but pulse wave W12 does not show any pulses. Conversely, during the second half of each cycle of the differential audio input waves, pulse wave W12 presents a series of pulses with different widths, but pulse wave W11 does not show any pulses. Therefore, differentially dividing pulse wave W11 and pulse wave W12 will still generate a pulse wave with only one duty cycle in each cycle of the second triangular wave 52, thus the Class D audio amplifier 1 has lower switching losses compared to a conventional Class D audio amplifier.
[0050] Figure 3A A schematic diagram illustrating a Class D audio amplifier according to some other embodiments of the present disclosure is shown, while Figure 3B Provided Figure 3A The waveform diagram shows how a Class D audio amplifier generates a PWM wave. Figure 3A and Figure 3B The contents shown are provided only to illustrate embodiments of this disclosure and should not be construed as any limitation on the claimed invention.
[0051] Reference Figure 3A This invention proposes another Class D audio amplifier 3. The differences between Class D audio amplifier 1 and Class D audio amplifier 3 include: Class D audio amplifier 3 includes two multiplexers (shown as a first multiplexer 17A and a second multiplexer 17B) instead of just one multiplexer (i.e., multiplexer 17), and the waveform reshaping device 33 of Class D audio amplifier 3 includes two comparators (shown as a first comparator 20A and a second comparator 20B) instead of just one comparator (i.e., comparator 20 of waveform reshaping device 13). The first multiplexer 17A and the first comparator 20A of Class D audio amplifier 3 respectively function as multiplexer 17 and comparator 20 of Class D audio amplifier 1. Furthermore, the triangular wave generator 11, pulse width modulator 15, and power stage 10 of Class D audio amplifier 3 are the same as those of Class D audio amplifier 1.
[0052] Similar to the first multiplexer 17A, the second multiplexer 17B may include two input terminals and one output terminal, and the two input terminals are used to receive a pair of differential audio input waves, which include a positive audio input wave IN. +and a negative audio input wave IN - Furthermore, the output of the second multiplexer 17B is used to alternately output the negative audio input wave IN based on a zero-crossing signal ZC. - Or positive audio input wave IN + The difference between the first multiplexer 17A and the second multiplexer 17B is that they output the pair of differential audio input waves in opposite ways. That is, when the first multiplexer 17A outputs the negative audio input wave IN... - At that time, the second multiplexer 17B will output the positive audio input wave IN. + ,vice versa.
[0053] Unlike the first comparator 20A, the second comparator 20B is used to compare the amplitude of the second triangular wave 52 with the pair of differential audio input waves.
[0054] Similar to flip-flop 30, flip-flop 60 can be any of various known flip-flops (e.g., an SR flip-flop) and is used to determine the start of each cycle of the second triangular wave 52 based on the output of the first comparator 20A. However, unlike flip-flop 30, flip-flop 60 is used to determine the peak of each cycle of the second triangular wave 52 based on an output of the second comparator 20B. In other words, under the control of flip-flop 60, the start of each cycle of the second triangular wave 52 is when the amplitude of the first triangular wave 50 becomes equal to the negative audio input wave IN of the pair of differential audio input waves. - When the amplitude of the second triangular wave 52 is equal to the amplitude of the positive audio input wave IN of the differential audio input wave, the peak of each cycle of the second triangular wave 52 is when the amplitude of the second triangular wave 52 becomes equal to the amplitude of the positive audio input wave IN of the differential audio input wave. + When the amplitude is.
[0055] like Figure 3B As shown, this invention proposes a pair of pulse waves. The negative audio input wave IN is generated by a pulse width modulator 15. - The signal is compared with the second triangular wave 52 to generate a pulse wave W21, while the positive audio input wave IN is modulated by the pulse width modulator 15. + A comparison is made with the second triangular wave 52 to generate a pulse wave W22. During the first half of each cycle of the differential audio input waves, pulse wave W21 presents a series of pulses with different widths, but pulse wave W22 does not show any pulses. Conversely, during the second half of each cycle of the differential audio input waves, pulse wave W22 presents a series of pulses with different widths, but pulse wave W21 does not show any pulses. Therefore, differentially dividing pulse wave W21 and pulse wave W22 will still produce a pulse wave with only one duty cycle in each cycle of the second triangular wave 52, and thus the Class D audio amplifier 3 has lower switching losses compared to a conventional Class D audio amplifier.
[0056] Figure 4 The flowchart illustrating a modulation method of a Class D audio amplifier according to some embodiments of the present disclosure is provided only to illustrate various embodiments and should not be considered as any limitation on the claimed invention.
[0057] Reference Figure 4 This invention proposes a modulation method 4 for a Class D audio amplifier. Modulation method 4 may include the following steps: generating a first triangular wave (labeled "41") using a triangular wave generator; reshaping the first triangular wave to generate a second triangular wave using a waveform reshaping device, wherein the slope of the second triangular wave is the same as that of the first triangular wave (labeled "43"); and using a pulse width modulator to modulate a pair of differential audio input waves using the second triangular wave instead of the first triangular wave to reduce all switching losses of the Class D audio amplifier (labeled "45"). Furthermore, in modulation method 4, the start of each cycle of the second triangular wave is when the amplitude of the first triangular wave becomes equal to the amplitude of a negative audio input wave of the pair of differential audio input waves, and the peak of each cycle of the second triangular wave is when the amplitude of the second triangular wave becomes equal to the amplitude of a positive audio input wave of the pair of differential audio input waves, or when the first triangular wave begins to decline.
[0058] In some embodiments, modulation method 4 may further include the following steps: comparing the amplitude of a first triangular wave with the amplitude of the negative audio input wave of the pair of differential audio input waves using a comparator to generate a comparison result; determining the start of each period of the second triangular wave based on the comparison result using a trigger; and determining the peak of each period of the second triangular wave based on the time when the first triangular wave begins to fall using a trigger.
[0059] In some embodiments, modulation method 4 may further include the following steps: comparing the amplitude of a first triangular wave with the amplitude of the negative audio input wave of the pair of differential audio input waves using a first comparator to generate a first comparison result; determining the start of each period of a second triangular wave based on the first comparison result using a trigger; comparing the amplitude of the second triangular wave with the amplitude of the positive audio input wave of the pair of differential audio input waves using a second comparator to generate a second comparison result; and determining the peak of each period of the second triangular wave based on the second comparison result using a trigger.
[0060] In some embodiments, modulation method 4 may further include the following step: alternately inputting the positive audio input wave and the negative audio input wave of the pair of differential audio input waves to a waveform reshaping device via at least one multiplexer.
[0061] In some embodiments, modulation method 4 may further include the step of: alternately outputting a pair of pulse waves through a logic controller.
[0062] In some embodiments of modulation method 4, modulating the pair of differential audio input waves and the second triangular wave includes: comparing the pair of differential audio input waves and the second triangular wave using a comparator.
[0063] Each embodiment of modulation method 4 essentially corresponds to a specific embodiment of either Class D audio amplifier 1 or Class D audio amplifier 3. Therefore, even though not all embodiments of modulation method 4 have been described in detail above, those skilled in the art can fully understand and implement all corresponding embodiments of modulation method 4 by referring only to the above description of Class D audio amplifier 1 and Class D audio amplifier 3.
[0064] Without being inconsistent with the claimed invention, various combinations, modifications, and / or substitutions of the embodiments disclosed directly or indirectly are substantially included throughout the disclosure, even if such combinations, modifications, and / or substitutions are not specifically mentioned above. The scope of protection of this invention is defined by the appended claims.
Claims
1. A Class D audio amplifier, comprising: A triangular wave generator is used to generate the first triangular wave; A waveform reshaping device, electrically connected to the triangular wave generator, is used to reshape the first triangular wave to generate a second triangular wave, wherein the slope of the second triangular wave is the same as the slope of the first triangular wave; and A pulse-width modulator, electrically connected to the waveform reshaping device, is used to use the second triangular wave instead of the first triangular wave to modulate the differential audio input wave, thereby reducing the switching loss of the Class D audio amplifier. The second triangular wave begins each cycle when the amplitude of the first triangular wave becomes equal to the amplitude of the negative audio input wave of the pair of differential audio input waves, and the peak of each cycle of the second triangular wave occurs when the amplitude of the second triangular wave becomes equal to the amplitude of the positive audio input wave of the pair of differential audio input waves, or when the first triangular wave begins to decline.
2. The Class D audio amplifier of claim 1, wherein the waveform reshaping device comprises: A comparator is used to compare the amplitude of the first triangular wave with the amplitude of the negative audio input wave of the pair of differential audio input waves; and A flip-flop is used to: The start of each cycle of the second triangular wave is determined by the output of the comparator; and The peak of each cycle of the second triangular wave is determined by the time when the first triangular wave begins to decline.
3. The Class D audio amplifier of claim 1, wherein the waveform reshaping device comprises: A first comparator is used to compare the amplitude of the first triangular wave with the amplitude of the negative audio input wave of the pair of differential audio input waves; A second comparator is used to compare the amplitude of the second triangular wave with the amplitude of the positive audio input wave of the pair of differential audio input waves; and Triggers, used to: The start of each cycle of the second triangular wave is determined based on the output of the first comparator; and The peak of each cycle of the second triangular wave is determined by the output of the second comparator.
4. The Class D audio amplifier as claimed in claim 1, further comprising: At least one multiplexer is used to alternately input the positive audio input wave and the negative audio input wave of the pair of differential audio input waves into the waveform reshaping device.
5. The Class D audio amplifier as claimed in claim 1, further comprising: A logic controller used to alternately output pulse waves.
6. The Class D audio amplifier as claimed in claim 1, wherein, The pulse width modulator includes a comparator for comparing the pair of differential audio input waves with the second triangular wave.
7. A modulation method for a Class D audio amplifier, comprising: The first triangular wave is generated using a triangular wave generator; A second triangular wave is generated by reshaping the first triangular wave using a waveform reshaping device, wherein the slope of the second triangular wave is the same as the slope of the first triangular wave; and The second triangular wave is used instead of the first triangular wave to modulate the differential audio input wave using a pulse width modulator, thereby reducing the switching loss of the Class D audio amplifier. The second triangular wave begins each cycle when the amplitude of the first triangular wave becomes equal to the amplitude of the negative audio input wave of the pair of differential audio input waves, and the peak of each cycle of the second triangular wave occurs when the amplitude of the second triangular wave becomes equal to the amplitude of the positive audio input wave of the pair of differential audio input waves, or when the first triangular wave begins to decline.
8. The modulation method as described in claim 7, further comprising: The amplitude of the first triangular wave is compared with the amplitude of the negative audio input wave of the pair of differential audio input waves by a comparator to produce a comparison result. The start of each cycle of the second triangular wave is determined by the comparison result using a trigger. as well as The trigger determines the peak of each cycle of the second triangular wave based on the time when the first triangular wave begins to fall.
9. The modulation method as described in claim 7, further comprising: The amplitude of the first triangular wave is compared with the amplitude of the negative audio input wave of the pair of differential audio input waves by a first comparator to produce a first comparison result. The trigger determines the start of each cycle of the second triangular wave based on the result of the first comparison. The amplitude of the second triangular wave is compared with the amplitude of the positive audio input wave of the pair of differential audio input waves by a second comparator to produce a second comparison result. as well as The trigger determines the peak of each cycle of the second triangular wave based on the second comparison result.
10. The modulation method of claim 7, further comprising: The positive audio input wave and the negative audio input wave of the pair of differential audio input waves are alternately input to the waveform reshaping device through at least one multiplexer.
11. The modulation method of claim 7, further comprising: The logic controller alternately outputs pulse waves.
12. The modulation method as described in claim 7, wherein, Modulating the differential audio input wave and the second triangular wave further includes comparing the differential audio input wave and the second triangular wave using a comparator.