Class-D Amplifier Control Using a VCO-Based Error ADC
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Solution Overview
Problem
Analog-input Class-D amplifiers require high precision analog components, which are difficult to fabricate reliably in current semiconductor manufacturing processes, and typically require complex analog control.
Innovation Solution
A Class-D amplifier with a front-end feedback error ADC followed by a digital loop filter, compensation filter, and digital PWM generator, utilizing a voltage-controlled oscillator (VCO) based Delta-Sigma ADC to encode analog signals into digital pulses, reducing the need for precise analog circuits by processing signals primarily in the digital domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high precision analog components are used in Class-D amplifiers, then amplification accuracy is improved, but manufacturing reliability deteriorates due to difficulty in fabrication
Solution Approach 1:
The patent replaces the mechanical/analog control system with a digital control system. Specifically, an analog-to-digital converter (ADC) converts the analog control signal to a digital signal, which is then processed by a digital pulse width modulator (PWM) to generate the switching control signal. This substitution eliminates the need for high-precision analog components while maintaining amplification accuracy through digital processing.
2Measurement precision
If complex analog control circuits are used, then amplification accuracy is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex analog control circuits with a digital control system comprising an ADC, digital signal processor, and digital PWM generator. This digital approach simplifies the overall control circuit architecture while achieving the required amplification accuracy through software-based signal processing and digital modulation techniques.
3Use of energy by moving object
If switching modes are used for power delivery, then power efficiency is improved, but heat dissipation characteristics worsen due to switching losses
Solution Approach 1:
The patent employs pulse width modulation (PWM) switching, which uses periodic on-off switching of power transistors to deliver power in controlled pulses. By rapidly switching the transistors between fully on and fully off states, the system achieves high power efficiency while minimizing the duration of transitional states where heat generation occurs, thereby reducing overall heat dissipation.
Data Source
AI summary
An amplifier includes an input circuit configured to receive an analog input signal and a feedback signal, and output an analog error signal based on the analog input signal and the feedback signal. An ADC is configured to convert the analog error signal into a digital signal in a phase domain. A digital control circuit is configured to generate a digital control signal based on the digital signal in the phase domain. An output circuit is configured to generate an amplified output signal based on the digital control signal, and a feedback circuit is configured generate the feedback signal based on the amplified output signal.