Digital Amplifier Feedback Circuit for Full-Range PWM Correction
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Solution Overview
Problem
Conventional digital amplifiers can only correct pulse width distortion within a limited range, restricting the correction of distortion factors beyond the minimum pulse width, which limits their ability to handle distortion in digital pulse width modulation.
Innovation Solution
A digital amplifier configuration that includes a digital modulation circuit, a triangular wave generation circuit, a drive circuit, and an error amplifier, which performs low-pass filtering and computes voltage differences to regenerate a digital pulse width modulation waveform, allowing for correction of pulse width values beyond the minimum range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional digital amplifier correction method is used, then correction is achieved within limited range (up to half minimum pulse width), but distortion correction beyond this range cannot be performed
Solution Approach 1:
The patent implements a feedback mechanism where the output signal is fed back through a low-pass filter to the summing point, allowing continuous correction of pulse width modulation errors. This feedback loop enables the system to detect and correct distortion beyond the limited range of conventional methods, achieving comprehensive distortion correction across the full modulation range.
Solution Approach 2:
The patent introduces a low-pass filter as an intermediary component that processes the feedback signal from the output stage. This intermediary allows the system to extract the audio signal from the PWM output and feed it back for correction, enabling extended correction range without directly modifying the pulse width modulation process itself.
2Device complexity
If pulse width correction is limited to one level above or below digital pulse width, then simple correction structure is maintained, but distortion factors exceeding this range cannot be corrected
Solution Approach 1:
The feedback mechanism continuously monitors the output and adjusts the PWM signal accordingly, replacing the limited one-level correction approach. This allows the system to achieve comprehensive distortion correction without significantly increasing structural complexity, as the same basic components are used in a feedback configuration.
Solution Approach 2:
The patent makes the correction system universal by applying feedback that works for all pulse width values, not just those within one level of the original signal. The low-pass filter and summing point configuration enable the system to handle any distortion factor, making the correction mechanism applicable across the entire operating range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables correction of digital pulse width values from 0% to 100%, significantly improving distortion correction in analog signals demodulated by digital pulse width modulation, enhancing the amplifier's performance in handling distortion.
Implementation Method 1
a first analog audio output section that performs low-pass filtering of a pulse voltage that is output from the digital modulation circuit and outputs an analog audio voltage
Implementation Method 2
a second analog audio output section that performs low-pass filtering of a signal power-amplified by the drive circuit and outputs audio band analog power
Data Source
AI summary
The disclosed digital amplifier (200) is provided with a voltage value conversion block (220) for converting a digital value of a digital pulse width of a digital modulation block (210) to a voltage value; and an integration circuit block (230) for generating a triangular wave by way of a master clock and modulating the generated triangular wave on the basis of a signal corresponding to the value of the modulation width of digital pulse width modulation. The disclosed digital amplifier (200) is provided with a low-pass filter (260) for demodulating pulse power that has been power-amplified by way of a drive circuit (250) to analog power of an audio band, and an error amplifier (290) for computing the voltage difference between the voltage of a low-pass filter (280) and the low-pass filter (260) and amplifying thereof.