Digital Speaker Code Conversion for Lower-Switching MOSFET Drive
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Solution Overview
Problem
Digital speaker systems based on multi-bit Σ-Δ modulation face high switching rates, leading to nonlinear distortion, excessive heating, and reduced efficiency, while conventional Class-D systems fail to address unified digital coding for multiple channels and frequency response deviations.
Innovation Solution
A method and device for driving digital speakers using code conversion, involving multi-bit Σ-Δ modulation, thermometer code conversion, dynamic mismatch-shaping, and pulse width modulation to reduce switching rates and eliminate harmonic distortion, while ensuring unified digital coding and frequency response correction across multiple channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multi-bit Σ-Δ modulation is used to drive digital speakers, then harmonic distortion is suppressed and audio quality is improved, but switching rate increases causing nonlinear distortion, excessive heating, and reduced efficiency
Solution Approach 1:
The patent segments the high switching rate signal into multiple lower-rate parallel channels. The multi-bit Σ-Δ modulated signal is decomposed into multiple 1-bit streams that are processed in parallel through separate digital speaker units, then combined at the output. This segmentation reduces the switching rate burden on individual channels while maintaining overall audio quality and harmonic suppression.
Solution Approach 2:
The patent introduces an intermediary code conversion stage that transforms the multi-bit Σ-Δ modulated signal into a format suitable for parallel processing. This intermediary representation allows the signal to be distributed across multiple channels with lower switching rates, acting as a bridge between the high-quality audio source and the physical limitations of individual speaker units.
2Manufacturing precision
If multi-bit Σ-Δ modulation is used to drive digital speakers, then harmonic distortion is suppressed, but switching losses and power dissipation increase
Solution Approach 1:
The patent divides the power delivery function across multiple parallel channels, each operating at lower switching rates. This segmentation reduces the switching losses in each individual channel, and the cumulative effect across all channels results in lower total power dissipation while maintaining the harmonic suppression benefits of multi-bit Σ-Δ modulation.
3Ease of manufacture
If 1-bit Σ-Δ modulation is used to simplify circuit implementation, then manufacturing complexity is reduced, but the system becomes sensitive to clock jitter causing nonlinear distortion
Solution Approach 1:
The patent uses multi-bit Σ-Δ modulation as an intermediary stage between the audio source and the final 1-bit digital speaker drivers. This intermediary multi-bit representation is more tolerant of clock jitter and manufacturing variations, and can be converted to 1-bit signals for each parallel channel in a way that reduces sensitivity to timing errors compared to direct 1-bit modulation.
4Manufacturing precision
If high switching rate is used in multi-bit Σ-Δ modulation, then audio quality is maintained, but MOSFET efficiency decreases due to increased heating
Solution Approach 1:
The patent segments the high switching rate operation across multiple parallel MOSFET channels, each operating at a fraction of the original switching rate. This distribution reduces the switching frequency burden on each MOSFET, decreasing switching losses and heating, while the parallel architecture maintains the overall audio quality and fidelity of the system.
Data Source
AI summary
A method and device for driving a digital speaker based on code conversion are provided in the invention. The method comprises the steps of: (1) converting input format; (2) performing multi-bit Σ-Δ modulation; (3) thermometer code conversion; (4) dynamic mismatch-shaping processing; (5) pulse width modulation code conversion; and (6) controlling on/off status switching of the MOSFET of a full-bridge power amplification network to drive a digital speaker load sound. The device comprises a sound source, an input format converter, a multi-bit Σ-Δ modulator, a thermometer coder, a dynamic mismatch shaper, a code converter, a multi-channel digital amplifier and a digital speaker load which are connected to each other in sequence. By means of the device and method of the invention, the switching rate of the power tube, the power dissipation and heating generated during the switching are reduced, the sound quality and efficiency of electroacoustic restoration are improved, the volume, weight and implementation cost of the system are decreased, and the level of electromagnetic radiation is reduced. Furthermore, the device and method of the invention also have excellent immunity to the frequency response deviation of multiple digital channels.