Noise-Shaping Amplifier Waveform Lock via Phase Detection
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Solution Overview
Problem
Conventional digital audio systems suffer from significant distortion at the power stage, which existing noise-shaping techniques fail to effectively mitigate, especially when trying to reproduce input waveforms faithfully, and often require costly and complex digital-to-analog conversion.
Innovation Solution
A noise-shaping amplifier architecture that locks the output waveform to the input waveform using phase detection, filter, and voltage-controlled oscillator circuitry, along with internal and external feedback loops, to move distortion outside the band of interest and maintain waveform fidelity without the need for D/A conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional digital audio systems use noise-shaping feedback techniques to reduce power stage distortion, then distortion is reduced, but the output waveform does not closely resemble the input waveform
Solution Approach 1:
The patent employs a feedback mechanism where the output waveform is continuously compared with the input waveform through phase detection circuitry. The phase difference generates a control signal that adjusts the VCO to lock the output frequency to the input frequency, thereby maintaining waveform fidelity while preserving distortion reduction benefits
Solution Approach 2:
The patent changes the operating parameters of the power stage by using a voltage-controlled oscillator whose frequency is dynamically adjusted based on phase detection. This allows the system to adapt the output frequency to match the input frequency, ensuring waveform fidelity while maintaining the noise-shaping distortion reduction
2Object-generated harmful factors
If modified sigma-delta modulator architecture is used to reduce power stage distortion, then distortion is pushed out of the band of interest, but digital-to-analog conversion is required adding cost and complexity
Solution Approach 1:
The patent extracts and eliminates the digital-to-analog conversion stage from the system. By using a voltage-controlled oscillator directly driven by the noise-shaping modulator output, the system maintains distortion reduction benefits without requiring separate D/A conversion circuitry, thereby reducing complexity and cost
Solution Approach 2:
The patent merges the functions of the noise-shaping modulator and the frequency control mechanism into a unified architecture. The VCO directly translates the modulated signal while being controlled by phase detection feedback, combining multiple functions into fewer components and eliminating the need for separate D/A conversion
3Object-generated harmful factors
If noise-shaping feedback is used to mitigate distortion, then distortion is reduced, but the output frequency may drift from the input frequency
Solution Approach 1:
The patent implements a phase detection feedback loop that continuously monitors the frequency relationship between input and output waveforms. When frequency drift occurs, the phase difference generates a corrective control signal that adjusts the VCO frequency back to match the input, maintaining accurate frequency tracking while preserving distortion reduction
Solution Approach 2:
The patent uses a dynamic voltage-controlled oscillator whose frequency can be adjusted in real-time based on phase detection feedback. This dynamic adjustment capability allows the system to maintain frequency accuracy despite the noise-shaping feedback process, preventing frequency drift while preserving distortion mitigation benefits
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 approach significantly reduces power stage distortion while ensuring the output waveform closely resembles the input waveform, enhancing signal fidelity and reducing system complexity and cost by eliminating the need for digital-to-analog conversion.
Implementation Method 1
Phase detection circuitry is operable to receive an input signal characterized by an input frequency, and to detect a phase difference between the input signal and a feedback signal
Implementation Method 2
Filter circuitry characterized by a filter response corresponding to a band of interest is operable to filter the control signal
Implementation Method 3
Voltage-controlled oscillator (VCO) circuitry is operable to receive the filtered control signal and generate an output signal in response thereto. The output signal is characterized by an output frequency which is substantially locked to the input frequency
Implementation Method 4
Feedback circuitry is operable to provide the feedback signal to the phase detection circuitry
Implementation Method 5
The feedback circuitry is further operable in conjunction with at least some of the phase detection circuitry, the filter circuitry, and the VCO circuitry to move at least some distortion generated by the output power stage outside of the band of interest
Data Source
AI summary
A generalized amplifier architecture is described which employs noise-shaping feedback, and for which the output waveform closely resembles the input waveform.