GaN PWM Audio Amplifier Feedback Circuit for Low THD+N
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Solution Overview
Problem
High-power audio amplifiers face limitations in size, signal-to-noise ratio, and total harmonic distortion plus noise (THD+N) while striving for high-resolution audio, small size, and high efficiency, especially when output power exceeds 200 W at 4ohm.
Innovation Solution
The design incorporates a GaN-based audio amplifier circuit with a modulator, switch stage, demodulator, and feedback circuit, utilizing pulse width modulation (PWM) and high-order digital filtering, along with a gate driver and GaN FETs to achieve efficient power amplification and minimize distortion, integrating a digital feedback loop and controller to manage impedance and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional amplifier designs are used to achieve high power output (>200W at 4ohm), then power output is improved, but size and heat dissipation increase
Solution Approach 1:
The patent employs GaN (gallium nitride) transistors instead of conventional silicon-based devices, fundamentally changing the material parameter to achieve higher efficiency and lower heat dissipation at high power outputs
Solution Approach 2:
The patent replaces conventional analog amplification mechanisms with a digital pulse-width modulation (PWM) based system, substituting continuous analog signal processing with digital switching control to reduce heat generation
2Power
If high power output is achieved in conventional amplifiers, then power output is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent substitutes analog signal processing with digital PWM modulation and processing, where the audio signal is converted to digital domain, processed through PWM, and then reconstructed, thereby improving signal-to-noise ratio through digital precision
Solution Approach 2:
The patent introduces a digital PWM signal as an intermediary between the input audio signal and the power output stage, allowing precise control of the power delivery while maintaining signal integrity and minimizing noise
3Power
If high power output is achieved in conventional amplifiers, then power output is improved, but total harmonic distortion plus noise increases
Solution Approach 1:
The patent replaces conventional analog power amplification with a digital PWM-based switching amplifier, where the output stage operates in a switching mode that significantly reduces harmonic distortion and noise
Solution Approach 2:
The patent implements a feedback circuit that monitors the output signal and feeds it back to the input stage, allowing real-time correction of distortion and noise, thereby improving total harmonic distortion plus noise performance at high power outputs
4Volume of moving object
If amplifier size is reduced for compact design, then device complexity is improved, but power output capability deteriorates
Solution Approach 1:
The patent changes the fundamental operating parameters by using GaN transistors with higher switching frequencies and efficiencies, allowing high power output in a smaller physical footprint
Solution Approach 2:
The patent substitutes conventional low-frequency analog amplification with high-frequency digital PWM switching, allowing smaller transformer and filter components, thereby reducing overall amplifier size while maintaining or improving power output capability
Data Source
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AI summary
The present disclosure provides an audio amplifier circuit, including: a modulator circuit configured to modulate an audio input signal into a pulse width modulation (PWM) signal; a switch stage circuit configured to receive the PWM signal and amplify the PWM signal; a demodulator circuit configured to receive and demodulate the amplified PWM signal to obtain a demodulated audio signal, and to output the demodulated audio signal to a speaker; and a feedback circuit configured to feed back the demodulated audio signal output by the demodulator circuit, and to output a feedback signal to an input end of the modulator circuit. Here, the feedback circuit includes an analog-to-digital converter and a loop filter. The switch stage circuit includes a driver and two GaN FETs.