Class D PWM Power Stage with Instantaneous Per-Pulse Feedback
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Solution Overview
Problem
Class AB amplifiers exhibit low efficiency, leading to increased power dissipation and heat management issues, which are not effectively mitigated by conventional class D amplifiers due to sensitivity to jitter and supply-related errors.
Innovation Solution
A class D amplifier with a modulator and power stage that provides instantaneous per-pulse feedback, correcting errors in each pulse to minimize power dissipation and heat generation, using a modulator circuit to adjust the PWM output signal based on instantaneous feedback from the power stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If class AB amplifiers are used to drive speaker load, then audio quality is maintained, but power efficiency deteriorates leading to increased power dissipation and heat generation
Solution Approach 1:
The patent employs pulse-width modulation (PWM) to switch power transistors between completely on and completely off states, creating discrete phase transitions in the power delivery. This switching action minimizes the time transistors operate in the linear region where power dissipation occurs, thereby reducing heat generation while maintaining audio quality
Solution Approach 2:
The patent uses high-frequency periodic carrier signals modulated by audio input signals to control power delivery. This periodic PWM action allows the amplifier to maintain low average power dissipation while delivering required audio power, effectively resolving the contradiction between power efficiency and thermal management
2Loss of energy
If class D amplifiers use conventional PWM without per-pulse feedback, then power efficiency is improved, but sensitivity to jitter and supply-related errors deteriorates
Solution Approach 1:
The patent implements instantaneous per-pulse feedback that measures the actual output pulse characteristics and adjusts subsequent PWM pulses to compensate for deviations. This feedback mechanism corrects jitter and supply-related errors in real-time, maintaining measurement precision while preserving the power efficiency benefits of class D operation
Solution Approach 2:
The patent uses feedback information from previous pulses to pre-adjust control parameters for upcoming pulses. This preliminary correction action compensates for anticipated errors before they affect output quality, reducing sensitivity to jitter and supply variations while maintaining high power efficiency
Data Source
AI summary
A class D amplifier is provided. The class D amplifier includes a modulator and a class D power stage. The modulator provides a PWM output signal to the class D power stage. For each pulse of the PWM input signal, the class D amplifier provides a corresponding pulse in the PWM output signal, such that the pulse is terminated when the area under the pulse of the output of the class D power stage is substantially equal to the area under the pulse of the corresponding PWM input signal. In this way, the class D amplifier provides instantaneous per-pulse PWM feedback.