Differential Interpolation PWM Digital-to-Analog Converter for High SNR Audio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Class-D amplifiers face challenges in achieving high signal-to-noise ratio (SNR) due to stability issues with sigma-delta modulation and the difficulty in generating short pulse widths required for high SNR, which are further compromised by power driver stages due to parasitic capacitors, leading to diminished signal quality and increased power consumption.
Innovation Solution
A differential interpolation pulse width modulation (iPWM) digital-to-analog converter is developed, incorporating an iPWM module with a PWM pulse generator, interpolation unit, self-calibration unit, and differential pulse width generator to produce high SNR signals by determining optimal pulse widths and interpolation bits, ensuring accurate pulse-width maintenance and efficient power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sigma-delta modulation is used in Class-D amplifier, then feedback loop can be implemented, but stability problems occur and modulator output signal gain is less than 1
Solution Approach 1:
The patent changes the modulation approach from conventional sigma-delta to differential interpolation PWM, altering the fundamental operating parameters. This involves using differential signaling and interpolation techniques to achieve both stability and unity gain, resolving the contradiction by fundamentally changing how the modulation is performed rather than adjusting minor parameters
Solution Approach 2:
The patent introduces a differential interpolation PWM module as an intermediary component between the digital audio input and power driver stage. This intermediary performs differential modulation with interpolation, achieving stable operation and unity gain without requiring complex feedback loops, thus resolving the stability and gain contradiction
2Measurement precision
If short pulse widths are generated for high SNR, then signal quality improves, but power consumption increases and parasitic capacitors cause signal diminishment
Solution Approach 1:
The patent transitions from single-ended PWM to differential PWM, adding a dimensional aspect to the signal. This differential approach allows the use of longer pulse widths while maintaining high SNR, because the differential signaling rejects common-mode noise and allows better utilization of the pulse width without increasing power consumption proportionally
Solution Approach 2:
The patent implements dynamic interpolation that adapts pulse widths based on signal requirements. Rather than always using minimum pulse widths for high SNR, the system dynamically adjusts pulse widths using interpolation techniques, achieving high SNR only when necessary while consuming less power during normal operation
3Measurement precision
If minimum time resolution is reduced to 122 ps for SNR>100 dB, then signal quality improves, but pulse generation becomes more difficult and power driver performance degrades
Solution Approach 1:
The patent uses differential signaling to effectively double the signal resolution without requiring halving of pulse widths. The differential approach allows achieving equivalent or better time resolution through voltage differential measurement rather than requiring extremely short pulse durations, making the system more manufacturable
Solution Approach 2:
The patent performs interpolation calculations in advance to determine optimal pulse widths before actual pulse generation. This preliminary computation allows the system to use longer, more manufacturable pulse widths while still achieving high effective resolution through the interpolation algorithm, avoiding the need for difficult-to-generate 122 ps pulses
4Power
If power driver stage is used with conventional PWM, then power delivery is achieved, but dead-time and parasitic capacitors diminish the signal
Solution Approach 1:
The patent introduces a differential interpolation PWM module as an intermediary between the digital audio source and power driver. This intermediary compensates for the power driver's dead-time and parasitic effects through differential signaling and interpolation, maintaining signal integrity while still achieving power delivery
Solution Approach 2:
The patent applies preliminary anti-action by using differential signaling that anticipates and compensates for the parasitic effects of the power driver stage. The differential approach pre-corrects for dead-time losses and capacitive effects, ensuring signal integrity is maintained despite the power driver's inherent limitations
Data Source
AI summary
A differential interpolation pulse width modulation (iPWM) digital to analog converter is provided, including an iPWM module for generating differential pulses from an input digital audio data stream, a power driver for providing energy to a terminal load and a filter for removing unwanted harmonic signals to reconstruct an analog signal, wherein the iPWM module further includes a PWM pulse generator to convert the digital input numerical code to a series of time domain pulses; an interpolation unit to increase the time domain resolution of the pulses; a self-calibration unit to maintain the pulse-width accuracy of the interpolation unit; a differential pulse width generator to convert the series of time domain pulses into voltage and time domain differential form.