Class-D Audio Amplifier PWM Reshaping for Lower Switching Loss
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Solution Overview
Problem
Conventional Class-D audio amplifiers suffer from high switching losses due to the power stage being turned on and off twice in each cycle of the triangular wave, leading to significant energy inefficiencies.
Innovation Solution
A Class-D audio amplifier design that generates a reshaped triangular wave to modulate differential audio input waves, reducing switching losses by integrating two duties into a single duty in each cycle, using a triangular wave generator, wave reshaping device, and pulse-width modulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power stage is turned on and off twice for each cycle of the triangular wave to handle two duties, then the audio signal can be properly amplified, but the switching loss increases significantly
Solution Approach 1:
The patent merges two separate duty cycles into a single duty cycle by using a full-bridge configuration where the first and second power switches operate in complementary fashion. The output stage combines the outputs of both half-bridges to produce a single PWM signal, reducing the number of switching events from two per triangular wave cycle to one, thereby reducing switching losses while maintaining proper audio amplification.
2Device complexity
If the conventional Class-D amplifier uses two duties per triangular wave cycle, then complete audio waveform reconstruction is achieved, but the device complexity increases
Solution Approach 1:
The patent segments the amplification function into two parallel half-bridges, each handling one duty cycle, but combines their outputs through a full-bridge configuration. This segmentation allows each half-bridge to operate independently with simpler switching control, while the combined output maintains complete audio waveform reconstruction, thus reducing device complexity without compromising signal integrity.
Data Source
AI summary
A Class-D audio amplifier includes a triangular wave generator, a wave reshaping device and a pulse-width modulator. The triangular wave generator generates a first triangular wave. The wave reshaping device generates a second triangular wave by reshaping the first triangular wave. The pulse-width modulator modulates a pair of differential audio input waves with the second triangular wave instead of the first triangular wave to reduce a switching loss of the Class-D audio amplifier.