Digital Audio Amplifier Feedback Loop for Low-Distortion PWM Output
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Solution Overview
Problem
Existing power amplifier technologies face challenges in efficiently processing digital audio signals while minimizing noise and distortion, particularly in reducing chip size and increasing the role of digital components over analog blocks to meet high-quality audio requirements.
Innovation Solution
The solution involves a digital audio power amplifier design that incorporates a digital-to-analog converter (DAC) and an analog-to-digital converter (ADC) in a feedback loop, along with a pulse-width modulator (PWM) and an inductor-capacitor network, to process digital input signals and reduce analog components, thereby enhancing signal processing and reducing harmonic distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital-to-analog converter (DAC) and analog-to-digital converter (ADC) are incorporated in feedback loop, then signal processing quality is improved and harmonic distortions are reduced, but device complexity increases
Solution Approach 1:
The amplifier is divided into distinct digital and analog sections. The digital section handles signal processing and control, while the analog section handles power amplification. This segmentation allows each section to be optimized independently, reducing overall complexity while maintaining high signal quality through the digital feedback loop with DAC and ADC.
Solution Approach 2:
The patent introduces digital signal processing blocks as intermediaries between the analog input/output and the control system. The DAC converts feedback voltage to current for error signal generation, and the ADC converts error voltage back to digital for processing. These intermediary conversions enable precise digital control while maintaining analog signal integrity.
2Area of stationary object
If analog components are reduced and digital components are increased, then chip size is reduced and manufacturing cost is lowered, but noise and distortion performance may deteriorate
Solution Approach 1:
The patent replaces traditional analog feedback mechanisms with a digital feedback system. Instead of using purely analog circuitry for error detection and correction, the system uses ADC to convert error signals to digital, processes them digitally, and uses DAC to convert corrected signals back to analog. This substitution reduces analog component count and chip size while maintaining or improving noise and distortion performance through digital signal processing capabilities.
Solution Approach 2:
The patent implements a sophisticated feedback loop that continuously monitors the output signal and corrects errors. The feedback mechanism uses ADC to digitize the error signal, allowing for precise digital processing and correction. This digital feedback system effectively reduces harmonic distortions and noise while requiring fewer analog components, thus reducing chip size without sacrificing performance.
3Ease of manufacture
If critical and complex circuit blocks are eliminated, then device complexity is reduced and ease of manufacture is improved, but reliability may be compromised
Solution Approach 1:
The patent changes the operational parameters and signal formats throughout the system. Digital signals are used for control and feedback processing instead of traditional analog waveforms. The system operates with digital error signals that are processed through digital logic blocks rather than complex analog circuitry. This parameter change to digital operation simplifies manufacturing while maintaining reliability through the robustness of digital signal processing and error correction capabilities.
Data Source
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AI summary
A method, comprising: receiving a digital audio input signal (D); applying signal processing (12, 14, 56, 17) to the digital audio input signal (D) received and providing an analog audio output signal (VOUT) based on the digital audio input signal (D) via a switching converter circuit (17) driven by a pulse-width-modulated, PWM, signal (DRV); sensing (19, RFB) the analog audio output signal (VOUT) and providing an analog feedback signal (IFB) indicative of the sensed analog audio output signal (VOUT); wherein applying signal processing (12, 14, 56, 17) to the digital audio input signal (D) comprises: applying digital-to-analog conversion, DAC (12) to the digital audio input signal (D), producing an analog replica of the digital input signal (IIN) as a result; producing (14) an analog error signal (IE) indicative of a difference between the analog replica of the digital input signal (IIN) and the analog feedback signal (IFB); applying analog-to-digital conversion, ADC (560) to the analog error signal (IE), producing a digital error signal (W) as a result; applying digital filtering (562) to the digital error signal (W), producing a filtered digital error signal (DC) as a result; and driving the switching converter circuit (17) with the PWM signal (DRV) produced based on the filtered digital error signal (Dc).