Digital Amplifier Duty Correction Using Adaptive Triangular Waves
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Solution Overview
Problem
Conventional digital amplifiers are limited in correcting distortion beyond the minimum pulse width, restricting the range of distortion correction to one level above or below the digital pulse width, which cannot effectively address distortions exceeding this range in PWM output.
Innovation Solution
The implementation of a digital amplifier with a level-adaptive triangular wave generation circuit and local analog feedback, allowing for the generation of triangular waves corresponding to the number of levels in the digital signal, enabling correction of digital pulse width modulation duty from 0% to 100% and improving distortion in analog signals demodulated by a low-pass filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional edge delay correction method is used, then distortion correction is achieved within limited range, but the correction range is restricted to up to half the minimum pulse width
Solution Approach 1:
The patent implements dynamic pulse width adjustment by generating multiple corrected pulse widths (first, second, third corrected pulse widths) based on different correction amounts. The system dynamically selects and applies the appropriate correction level depending on the detected edge delay, enabling adaptation beyond the fixed half-minimum-pulse-width limitation of conventional methods.
Solution Approach 2:
The patent changes the correction parameter from a fixed correction amount to multiple variable correction amounts. By introducing different correction levels (first correction amount, second correction amount, third correction amount) that correspond to different pulse width adjustments, the system expands the correction range while maintaining precision within each correction level.
2Device complexity
If digital pulse width modulation is performed with limited correction, then simple circuit operation is maintained, but distortion exceeding one level above or below digital pulse width cannot be corrected
Solution Approach 1:
The patent segments the distortion correction process into multiple discrete correction levels, each handling specific ranges of edge delay. By dividing the correction into first, second, and third corrected pulse widths with different correction amounts, the system maintains relatively simple circuit operation for each segment while collectively achieving comprehensive distortion correction across the full range.
Solution Approach 2:
The patent introduces an intermediary correction mechanism that processes the PWM signal through multiple correction stages. The correction amount calculation unit acts as an intermediary that determines the appropriate correction level based on the edge delay detection, enabling effective distortion correction without requiring complete redesign of the PWM generation circuitry.
3Speed
If correction is limited to minimum pulse width range, then fast response is achieved, but distortion factors beyond one level cannot be addressed
Solution Approach 1:
The patent performs preliminary correction by generating multiple corrected pulse width options in advance based on detected edge delay. The correction amount calculation unit pre-determines the appropriate correction level before the final PWM output, enabling fast response while ensuring accurate distortion correction across the full range of possible delays.
Data Source
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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.