Digital PWM Feedback for Switching Amplifier Error Correction
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Solution Overview
Problem
Conventional switching power amplifiers face issues with nonlinearity and ripple noise in the power stage, which degrade audio performance and require complex and costly analog loop filters for error correction.
Innovation Solution
An error correction method and apparatus that extracts and remodulates error signals between ideal and actual PWM signals in a digital domain, allowing for correction of PWM errors by adjusting pulse width, thereby eliminating the need for analog domain corrections and reducing system complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an accurate analog loop filter is designed to generate the error signal in the error processing unit, then the error correction performance is improved, but the system complexity and cost increase
Solution Approach 1:
The patent replaces the analog loop filter (analog domain) with a digital filter implemented in the digital signal processor. The error signal is generated by digitally filtering the difference between the PWM signal and the power stage output, substituting complex analog circuitry with digital processing to reduce system complexity while maintaining accuracy
Solution Approach 2:
The patent changes the domain of error signal processing from analog to digital. By converting the error signal generation and processing to the digital domain, the system achieves accurate error correction without requiring precise analog filter design, thereby reducing complexity and cost
2Reliability
If correction operation is performed in the analog domain, then the error correction is implemented, but it is very difficult to correct the characteristic of external noise or nonlinear characteristic
Solution Approach 1:
The patent substitutes analog domain correction with digital domain correction. The digital signal processor can implement sophisticated correction algorithms that are adaptable to various noise types and nonlinear characteristics, overcoming the limitations of analog correction methods
Solution Approach 2:
The patent transitions the correction operation from analog domain to digital domain, enabling flexible and adaptable correction of external noise and nonlinear characteristics through digital signal processing techniques that can be programmed and adjusted without changing hardware
3Use of energy by moving object
If conventional class D power amplifier is used, then amplification efficiency is improved, but nonlinearity of power stage and ripple noise of power supply unit deteriorate audio performance
Solution Approach 1:
The patent implements a feedback mechanism where the output of the power stage is compared with the original PWM signal, and the error signal is processed and fed back to correct the PWM signal before it enters the power stage. This closed-loop feedback system reduces nonlinearity and ripple noise while maintaining high amplification efficiency
Solution Approach 2:
The patent discards the distorted output signal and recovers the original audio signal by processing the error signal through digital filtering and remodulation, then using this corrected signal to drive the power stage, thereby eliminating harmful nonlinearities and noise while preserving efficiency
Data Source
AI summary
An error correction method and apparatus to enhance performance of a switching power amplifier through digital feedback of an audio pulse width modulation (PWM) signal. The error correction apparatus includes a PWM unit to convert an audio signal into a PWM signal, a power stage unit to switch and amplify power of the PWM signal generated by the PWM unit, an error signal extraction unit to compare a reference PWM signal generated in the PWM unit with the PWM signal output from the power stage unit, thereby extracting an error signal, a remodulation unit to compare the error signal extracted in the error signal extraction unit with a reference signal having a predetermined slope, thereby modulating the error signal to an error PWM signal, and a signal correction unit to correct an error, by changing the pulse width of the PWM unit according to the error PWM signal generated in the remodulation unit.