Controlling a noise transfer function of a signal path to reduce charge pump noise
阅读说明:本技术 控制信号路径的噪声传递函数以减少电荷泵噪声 (Controlling a noise transfer function of a signal path to reduce charge pump noise ) 是由 普拉达普·达南杰 布鲁斯·E·杜尔威尔 于 2018-04-24 设计创作,主要内容包括:一种用于生成输出信号的装置可包括信号路径,该信号路径具有:模拟信号路径部分,其具有模拟幅值下垂;数字信号路径部分,其具有数字幅值下垂;数模转换器,其用于将数字输入信号转换为模拟信号;第一数字补偿滤波器,其用于补偿模拟幅值下垂;第二数字补偿滤波器,其用于补偿数字幅值下垂,使得第一数字补偿滤波器和第二数字补偿滤波器一起补偿信号路径的幅值下垂,以确保信号路径的通带响应基本平坦。(An apparatus for generating an output signal may include a signal path having: an analog signal path portion having an analog amplitude droop; a digital signal path portion having a digital amplitude droop; a digital-to-analog converter for converting a digital input signal to an analog signal; a first digital compensation filter for compensating for analog amplitude droop; a second digital compensation filter for compensating for the digital amplitude droop such that the first digital compensation filter and the second digital compensation filter together compensate for the amplitude droop of the signal path to ensure that the passband response of the signal path is substantially flat.)
1. An apparatus for generating an output signal, comprising a signal path having:
an analog signal path portion having an audio input for receiving an analog signal, an audio output for providing an output signal and an optional analog gain, and configured to generate an output signal based on the analog signal and in accordance with the optional analog gain, wherein a transfer function of the analog signal path portion has an analog amplitude droop;
a digital signal path portion having a selectable digital gain and configured to receive a digital input signal and process the digital input signal in accordance with the selectable digital gain, wherein a transfer function of the digital signal path portion has a digital amplitude droop;
a digital-to-analog converter for converting the digital input signal processed by the digital signal path portion into the analog signal;
a first digital compensation filter that compensates for the analog amplitude droop; and
a second digital compensation filter that compensates for the digital amplitude droop such that the first digital compensation filter and the second digital compensation filter together compensate for the amplitude droop of the signal path to ensure that the passband response of the signal path is substantially flat.
2. The apparatus of claim 1, wherein the first digital compensation filter comprises an oversampling rate magnitude compensation filter.
3. The apparatus of claim 2, wherein the oversampling rate magnitude compensation filter improves a stop band attenuation of the signal path.
4. The apparatus of claim 1, wherein the second digital compensation filter comprises a baseband magnitude compensation filter.
5. The apparatus of claim 1, wherein the first digital filter and the second digital compensation filter improve noise performance of the signal path for higher frequency signals.
6. The apparatus of claim 1, wherein:
the first digital compensation filter comprises a baseband amplitude compensation filter;
the second digital compensation filter comprises an oversampling rate magnitude compensation filter; and
the compensation filter coefficients of the first and second digital compensation filters are optimized for a plurality of gain configurations of the selectable analog gain and the selectable digital gain and stored in a memory.
7. The apparatus of claim 1, wherein the signal is an audio signal.
8. A method for generating an output signal through a signal path, comprising:
generating the output signal through an analog signal path portion of the signal path, the analog signal path portion having an audio input for receiving an analog signal, an audio output for providing the output signal and an optional analog gain, and being configured to generate the output signal based on the analog signal and in accordance with the optional analog gain, wherein a transfer function of the analog signal path portion has an analog amplitude droop;
processing a digital input signal according to a selectable digital gain by a digital signal path portion of the signal path, the digital signal path portion having the selectable digital gain and being configured to receive the digital input signal and process the digital input signal according to the selectable digital gain, wherein a transfer function of the digital signal path portion has a digital amplitude droop;
converting the digital input signal processed by the digital signal path portion into an analog signal by a digital-to-analog converter of the signal path
Compensating the analog amplitude droop with a first digital compensation filter; and
compensating the digital amplitude droop with a second digital compensation filter such that the first digital compensation filter and the second digital compensation filter together compensate for the amplitude droop of the signal path to ensure a substantially flat passband response of the signal path.
9. The method of claim 8, wherein the first digital compensation filter comprises an oversampling rate magnitude compensation filter.
10. The method of claim 9, further comprising improving a stop band attenuation of the signal path by the oversampling rate magnitude compensation filter.
11. The method of claim 8, wherein the second digital compensation filter comprises a baseband magnitude compensation filter.
12. The method of claim 8, further comprising improving noise performance of the signal path for higher frequency signals by the first and second digital compensation filters.
13. The method of claim 8, wherein:
the first digital compensation filter comprises a baseband amplitude compensation filter;
the second digital compensation filter comprises an oversampling rate magnitude compensation filter; and
the compensation filter coefficients of the first and second digital compensation filters are optimized for a plurality of gain configurations of the selectable analog gain and the selectable digital gain and stored in a memory.
14. The method of claim 8, wherein the signal is an audio signal.
Technical Field
The present disclosure relates generally to charge pump power supplies, including but not limited to personal audio devices such as wireless telephones and media players, and more particularly to systems and methods for regulating output power generated by a charge pump to maintain an input current limit of the charge pump.
Background
Personal audio devices, including wireless telephones such as mobile/cellular telephones, cordless telephones, mp3 players, and other consumer audio devices are widely used. Such personal audio devices may include circuitry for driving a pair of headphones or one or more speakers. Such circuitry typically includes a power amplifier for driving the audio output signal to a headphone or speaker.
One particular characteristic of a personal audio device that may affect its marketability and desirability is the dynamic range of its audio output signals. In short, the dynamic range is the ratio between the maximum and minimum values of the audio output signal. One way to increase the dynamic range is to apply a high gain to the power amplifier. However, the noise present in the audio output signal may typically be a monotonically increasing function of the power amplifier gain, so that any dynamic range increase due to a high gain amplifier may be cancelled by the signal noise, which may effectively mask audio signals of lower intensity.
U.S. patent application No. 14/083,972 (the' 972 application), entitled "enhancing Dynamic range of Audio Signal Path," filed on 19/11/2013 and assigned to the applicant of the present disclosure (cirrus logic, Inc.) discloses a method and system for enhancing Dynamic range of Audio Signal Path. In the' 972 application, an apparatus for providing an output signal to an audio transducer includes a digital signal path portion, an analog signal path portion, a digital-to-analog converter (DAC) coupled between the digital signal path portion and the analog signal path portion, and a control circuit. The digital path portion may have a selectable digital gain and may be configured to generate a digital audio output signal in accordance with the selectable digital gain, and the DAC may be configured to generate an analog signal from the digital output signal. The analog signal path portion may have an audio input for receiving an analog signal, an audio output for providing an output signal, and an optional analog gain, and may be configured to generate the output signal based on the analog signal and according to the optional analog gain. The control circuit may be configured to select the selectable analog gain and select the selectable digital gain based on a magnitude of a signal indicative of the output signal.
Efficient operation of dynamic range enhancement systems typically requires pass band flatness of the signal path in the frequency range of interest, since deviations from a flat pass band can lead to false triggering of the dynamic range enhancement system, altering both the optional analog gain and the optional digital gain. However, each of the analog and digital path portions of the signal path may have a transfer function that is not flat over the frequency range of interest, a condition commonly referred to as "amplitude droop".
Power amplifiers can often be the primary consumer of power in personal audio devices and, therefore, can have the greatest impact on the battery life of the personal audio device. In a device having a linear power amplifier for the output stage, power is wasted during low signal level output because the voltage drop across the active output transistor plus the output voltage will be equal to the constant supply rail voltage. Thus, amplifier topologies such as class G and class H are desirable to reduce the voltage drop across the output transistor(s) and thereby reduce the power wasted by the power consumption of the output transistor(s).
To provide a variable supply voltage to such power amplifiers, a charge pump power supply may be used, for example, such as that disclosed in us patent 8,311,243, where an indication of the signal level at the output of the circuit is used to control the supply voltage in a class G topology. In general, the above topology can improve the efficiency of an audio amplifier as long as there are periods of low signal level in the audio source. Typically, in such topologies, multiple thresholds define output signal level dependent modes of operation of the charge pump power supply, wherein in each mode the charge pump power supply generates a different supply voltage.
Disclosure of Invention
In accordance with the teachings of the present disclosure, certain disadvantages and problems associated with the performance of charge pumps have been reduced or eliminated.
According to an embodiment of the present disclosure, an apparatus for generating an output signal may include a signal path having: an analog signal path portion having an audio input for receiving an analog signal, an audio output for providing an output signal, and an optional analog gain, and configured to generate the output signal based on the analog signal and in accordance with the optional analog gain, wherein a transfer function of the analog signal path portion has an analog amplitude droop; a digital signal path portion having a selectable digital gain and configured to receive a digital input signal and process the digital input signal in accordance with the selectable digital gain, wherein a transfer function of the digital signal path portion has a digital amplitude droop; a digital-to-analog converter for converting the digital input signal processed by the digital signal path portion into the analog signal; a first digital compensation filter that compensates for the analog amplitude droop; and a second digital compensation filter that compensates for the digital magnitude droop such that the first digital compensation filter and the second digital compensation filter together compensate for the magnitude droop of the signal path to ensure that the passband response of the signal path is substantially flat.
In accordance with these and other embodiments of the present disclosure, a method for generating an output signal through a signal path may include: generating the output signal through an analog signal path portion of the signal path, the analog signal path portion having an audio input for receiving an analog signal, an audio output for providing the output signal and an optional analog gain, and being configured to generate the output signal based on the analog signal and in accordance with the optional analog gain, wherein a transfer function of the analog signal path portion has an analog amplitude droop. The method may also include processing a digital input signal according to a selectable digital gain through a digital signal path portion of the signal path, the digital signal path portion having the selectable digital gain and being configured to receive the digital input signal and process the digital input signal according to the selectable digital gain, wherein a transfer function of the digital signal path portion has a digital amplitude droop. The method may additionally include converting the digital input signal processed by the digital signal path portion to an analog signal by a digital-to-analog converter of the signal path. The method may further include compensating the analog amplitude droop with a first digital compensation filter and compensating the digital amplitude droop with a second digital compensation filter such that the first digital compensation filter and the second digital compensation filter together compensate for the amplitude droop of the signal path to ensure a substantially flat passband response of the signal path.
In accordance with these and other embodiments of the present disclosure, an apparatus may include: a delta-sigma modulator for quantization noise shaping a digital signal, a digital-to-analog converter configured to generate an analog signal from the digital signal, and an amplifier configured to amplify the analog signal and to be powered by a charge pump, wherein the charge pump is configured to operate at a switching frequency approximately equal to a zero of a modulator noise transfer function of the delta-sigma modulator such that an effect of the charge pump on a total harmonic distortion noise of the apparatus is minimized.
In accordance with these and other embodiments of the present disclosure, a method is provided for minimizing noise in an apparatus that includes a delta-sigma modulator for quantization noise shaping a digital signal, a digital-to-analog converter configured to generate an analog signal from the digital signal, and an amplifier configured to amplify the analog signal and to be powered by a charge pump. The method may include operating the charge pump at a switching frequency approximately equal to a zero of a modulator noise transfer function of the delta-sigma modulator such that an effect of charge pump noise on total harmonic distortion noise of the apparatus is minimized.
The technical advantages of the present disclosure may be readily apparent to one skilled in the art from the figures, descriptions, and claims included herein. The objects and advantages of the embodiments will be realized and attained by at least the elements, features, and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the claims as set forth in this disclosure.
Drawings
A more complete understanding of embodiments of the present invention and the advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:
FIG. 1 is an illustration of an example personal audio device in accordance with an embodiment of the present disclosure;
FIG. 2 is a block diagram of selected components of an example integrated circuit that may be implemented as the audio integrated circuit of the personal audio device depicted in FIG. 1 or any other suitable device, in accordance with embodiments of the present disclosure; and
FIG. 3 is a block diagram of selected components of an example over-sampling rate magnitude compensation filter according to an embodiment of the present disclosure.
Detailed Description
Fig. 1 is an illustration of an example personal audio device 1 according to an embodiment of the present disclosure. The personal audio device 1 is an example of a device in which techniques according to embodiments of the present disclosure may be employed, but it should be understood that not all of the elements or configurations embodied in the illustrated personal audio device 1 or circuits depicted in subsequent illustrations are required to practice the subject matter set forth in the claims. The personal audio device 1 may include a transducer such as a speaker 5, the speaker 5 may reproduce distant speech received by the personal audio device 1 as well as other local audio events such as ringtones, stored audio programming material, injection of near-end speech (i.e., speech of the user of the personal audio device 1) to provide balanced conversational perception, and other audio that needs to be reproduced by the personal audio device 1, such as sources from web pages or other network communications received by the personal audio device 1 as well as audio indications such as low battery indications and other system event notifications. Additionally or alternatively, headphones 3 may be coupled to the personal audio device 1 to generate audio. As shown in fig. 1, the earpiece 3 may be in the form of a pair of
The personal audio device 1 may provide a display to a user and receive user inputs using the touch screen 2, or alternatively, a standard Liquid Crystal Display (LCD) may be combined with various buttons, sliders, and/or dials disposed on a surface and/or sides of the personal audio device 1. As also shown in fig. 1, the personal audio device 1 may include an audio Integrated Circuit (IC)9 for generating analog audio signals for transmission to the headphones 3, speakers 5, and/or other audio transducers.
Fig. 2 is a block diagram of selected components of an example IC9, the example IC9 may be implemented as an audio IC9 of the personal audio device 1 or any other suitable device, in accordance with an embodiment of the present disclosure. As shown in FIG. 2, a digital signal source (e.g., a processor)A digital signal processor, a microcontroller, test equipment, or other suitable digital signal source) may provide a digital input signal DIG _ IN to a digital path portion of the signal path that includes interpolation filter 22, dynamic
The charge
Interpolation filter 22 may include any suitable system for upsampling the digital input signal DIG _ IN to generate a resulting digital signal having a sample rate greater than the sample rate of the digital input signal DIG _ IN.
The up-sampled digital signal generated by the interpolation filter 22 may then be processed by a dynamic
As an example of the dynamic range enhancement function of audio IC9, gain
The output of the dynamic
The output generated by the OSR
The output generated by the modulator/
As described above, the digital signal generated by FIR filter 32 (i.e., the digital output signal generated by the digital path portion) may be converted to an equivalent analog signal (e.g., V) by DAC 14IN) The
As described in the background section of the present application, the signal path of the audio IC9 may suffer from amplitude droop, where the passband frequency response is not flat over the frequency range of interest, and such amplitude droop may result in false triggering of the dynamic range enhancement system. In many cases, different portions of the signal path may cause amplitude droop, respectively. For example, the digital path portion (without the OSR amplitude compensation filter 28) may have digital amplitude droop, and the
To compensate for digital amplitude droop, and in particular droop caused by interpolation filter 22, interpolation filter 22 may include a baseband amplitude compensation filter 24 that compensates for the digital amplitude droop. Thus, the
Further, the OSR
In some embodiments, the filter coefficients of the baseband magnitude compensation filter 24 and the OSR
FIG. 3 is a block diagram of selected components of an example OSR
Storing the OSR amplitude compensation filter 28One potential drawback in the signal path of the audio IC9 is that the quantization noise present in the signal path may be shaped such that its contribution in the audio band is reduced, but the quantization noise power may reside in higher frequencies close to the switching frequency of the charge
To reduce or eliminate foldback noise of such charge pumps, a delta-sigma modulator implementing at least a portion of the modulator/
The present disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the exemplary embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to a device or system or a component of a device or system adapted to, arranged to, capable of, configured to, enabling, operable to, or operative to perform a particular function includes the device, system or component, whether or not it or the particular function is activated, turned on, or unlocked, so long as the device, system or component is so adapted, arranged, capable, configured to, enabled, operable, or operative.
All examples and conditional language recited herein are intended to aid the reader in understanding the concepts of the invention and the inventors further the field of development and are to be construed as being without limitation to such specifically recited examples and conditions. Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto without departing from the spirit and scope of the invention.
- 上一篇:一种医用注射器针头装配设备
- 下一篇:使用开关电源的相位频率检测器线性化