Class D Amplifier Stereo-Mono Conversion With Current Sharing Control
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Solution Overview
Problem
Class D amplifiers face challenges in efficiently controlling output current and managing current sharing among multiple channels, leading to potential overstressing of electronic components and increased component costs due to the need for additional circuitry for generating reference waveforms.
Innovation Solution
The design incorporates a current feedback loop with integrated self-oscillating feedback, allowing signal artifacts to provide a self-oscillating loop, eliminating the need for a dedicated reference waveform generator and enabling cost savings, while also ensuring equal current sharing among channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated reference waveform generator is used for current feedback control, then current control precision is improved, but device complexity and component costs increase
Solution Approach 1:
The patent applies self-service by using the amplifier's own output signal and its inherent switching artifacts as the reference waveform for current feedback control. Instead of requiring an external dedicated reference waveform generator, the system utilizes its own operational characteristics (switching frequency and output signal) to generate the necessary reference, thereby eliminating additional components while maintaining control precision
Solution Approach 2:
The patent implements multi-functionality by making the output filter serve dual purposes: filtering the amplifier output signal and simultaneously generating the reference waveform for current feedback control. This allows a single component to perform multiple functions, reducing overall device complexity while maintaining the required control precision
2Reliability
If additional circuitry is added for current feedback control, then current sharing among channels is improved, but manufacturing costs increase
Solution Approach 1:
The patent merges the current feedback control circuitry with the existing output filter and signal processing paths. By combining these functions into existing structural elements rather than adding separate dedicated circuits, the system achieves reliable current sharing among channels while avoiding the increased manufacturing costs that would result from additional discrete components
3Measurement precision
If a current feedback loop is implemented, then output current control is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback by using the amplifier's own output current to generate a reference waveform that is fed back to the modulator. This closed-loop feedback mechanism provides precise output current control while utilizing existing system components (output filter, switching artifacts) to minimize the addition of complex circuitry
Solution Approach 2:
The system applies self-service by generating its own reference waveform from its own output signal and switching artifacts. This eliminates the need for external reference sources or additional dedicated control circuits, achieving precise current control without proportionally increasing device complexity
Data Source
AI summary
The technology described in this document can be embodied in an audio power amplifier that includes a first channel and a second channel. Each of the first channel and the second channel includes an input to receive an input signal, a pair of switching devices, drive circuitry for driving the pair of switching devices to produce a signal, and an output filter to filter the signal from the pair of switching devices. The output filter is configured to provide the filtered signal to an audio load. Each of the first channel and the second channel includes a voltage feedback loop to provide a voltage of the filtered signal to a voltage controller of the audio power amplifier, and a current feedback loop to provide a current of the filtered signal to a current controller of the audio power amplifier. The audio power amplifier includes a summer for combining the input of the first channel and the input of the second channel when an output of the first channel is connected to an output of the second channel.