Class-D Amplifier Common-Mode Feedback for Power Noise Suppression
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Solution Overview
Problem
Conventional class-D amplifiers face challenges in reducing differential mode power noise without adjusting the feedback path, which requires additional silicon area and affects performance.
Innovation Solution
A class-D amplifier design that includes a loop filter, PWM circuit, summing circuit, output circuit, and supply voltage filter to adjust the common mode level of input signals, allowing for reduced differential mode power noise without altering the feedback path matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If feedback path matching is improved to reduce differential mode power noise, then power noise suppression is improved, but silicon area increases
Solution Approach 1:
A common mode feedback path is introduced as an intermediary mechanism to suppress differential mode power noise. The common mode feedback signal acts as a mediator that counteracts the differential mode noise without requiring direct modification of the differential feedback path, thereby avoiding additional silicon area while achieving noise suppression
Solution Approach 2:
The patent implements a common mode feedback mechanism that feeds back the common mode signal to actively cancel differential mode power noise. This feedback approach allows dynamic suppression of noise without requiring static matching adjustments that would consume additional silicon area
2Object-affected harmful factors
If feedback path matching is adjusted to reduce differential mode power noise, then power noise suppression is improved, but device complexity increases
Solution Approach 1:
The common mode feedback path serves as an intermediary that simplifies the overall system by providing a straightforward mechanism to suppress differential mode noise without complicating the existing differential feedback path matching requirements
3Object-affected harmful factors
If power-supply rejection ratio is improved to reduce differential mode power noise, then power noise suppression is improved, but device complexity increases
Solution Approach 1:
The common mode feedback mechanism acts as an intermediary that improves power-supply rejection ratio without requiring complex circuit modifications. By introducing this intermediate feedback path, the system achieves better rejection of power supply variations and differential mode noise while maintaining relatively simple circuit architecture
Data Source
AI summary
A class-D amplifier configured to adjust at least one input signal to at least one output signal. The class-D amplifier comprises: a loop filter, configured to receive the input signal; a PWM circuit, configured to generate at least one PWM signal; a summing circuit, coupled between an output of the loop filter and an input of the PWM circuit; an output circuit operating at a supply voltage, configured to generate the output signal responding to the PWM signal; and a supply voltage filter, configured to monitor the supply voltage to generate a filtered signal to the summing circuit. The summing circuit is configured to sum the output of the loop filter and the filtered signal to adjust a common-mode level of the input of the PWM circuit.