Class D Audio Amplifier Clock Synchronization for Low Distortion
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Solution Overview
Problem
Conventional Class D audio amplifiers generate unnecessary noise and decrease audio quality when multiple units are used asynchronously, and are prone to distortion and noise interference due to improper frequency manipulation.
Innovation Solution
An audio amplifier system comprising multiple sub-audio amplifier sets, a clock source, and a speaker, where each sub-audio amplifier set includes a comparator, resistors, capacitors, and a transistor set, allowing for both audio amplify and self-oscillation modes to synchronize operating frequencies and reduce distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple Class D amplifiers are used simultaneously, then the power consumption is reduced and audio output capability is enhanced, but unnecessary noise is generated when output audio signals are asynchronous
Solution Approach 1:
The patent implements a feedback mechanism where the operating frequency of each Class D amplifier is fed back to a central controller, which then generates clock signals to synchronize all amplifiers. This feedback loop ensures that multiple amplifiers operate at the same frequency, eliminating asynchronous noise while maintaining the power efficiency benefits of using multiple Class D amplifiers.
Solution Approach 2:
The patent combines multiple Class D amplifiers into a unified system with a shared clock source and frequency synchronization mechanism. By merging the control functions and synchronizing the operating frequencies of individual amplifiers, the system achieves noise reduction while maintaining the enhanced audio output capability provided by multiple amplifiers operating in unison.
2Device complexity
If the operating frequency of Class D amplifier is not properly manipulated, then the circuit is simple to implement, but the amplifier is easily disturbed by noise having similar frequency
Solution Approach 1:
The patent introduces dynamic frequency manipulation by implementing a frequency detection and adjustment mechanism. The system continuously monitors the operating frequency and dynamically adjusts it to avoid noise interference, transforming the static frequency operation into a dynamic adaptive process that maintains performance while managing complexity.
Solution Approach 2:
The patent changes the operating parameter (frequency) of the Class D amplifier dynamically based on detected noise conditions. By adjusting the frequency parameter in response to environmental noise, the system avoids interference while maintaining simple circuit implementation through parameter adaptation rather than complex structural changes.
3Duration of action of stationary object
If audio signals are inputted continuously to maintain continuous output, then the audio output is uninterrupted, but distortion of previously inputted audio signal occurs
Solution Approach 1:
The patent implements periodic action by using pulse width modulation (PWM) with synchronized switching cycles across all Class D amplifiers. This periodic operation ensures that audio signals are processed in synchronized intervals, allowing continuous output while maintaining signal accuracy through the regular, predictable timing of signal processing cycles.
Solution Approach 2:
The patent maintains continuous useful action through the LC filter that stores energy during active regions and releases it during inactive regions, ensuring uninterrupted audio output. Combined with synchronized PWM operation, this allows continuous output without the distortion that would result from asynchronous switching between multiple amplifiers.
Data Source
AI summary
An audio amplifier includes a plurality of sub-audio amplifier sets, a clock source, and a speaker. When the audio amplifier is under an audio amplify mode, the plurality of sub-audio amplifier sets is operated under a synchronic operating frequency with a same clock signal generated by the clock source. When the audio amplifier is under a self-oscillation mode, the clock signal is isolated from being input to the plurality of sub-audio amplifier sets. A higher distortion is prevented by repeatedly charging and discharging an oscillating capacitor of a sub-audio amplifier in a sub-audio amplifier set.