Switching Amplifier PWM Timing for Zero-Crossing Distortion
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Solution Overview
Problem
Switching amplifiers suffer from crossover distortion, particularly at the zero crossing point, due to inherent transmission delays in the power amplifiers, leading to increased total harmonic distortion and noise in the output signal.
Innovation Solution
The implementation of a method that generates complementary pulse width modulated signals with delayed and digitally half-wave rectified pulse trains, ensuring non-zero drive levels near crossover points, thereby reducing crossover distortion. This involves modulating input signals into pulse trains with pairs or single pulses based on signal magnitude thresholds and using a delay cell to synchronize these signals, ensuring consistent pulse widths across output terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching amplifiers are used to achieve high efficiency and low power dissipation, then power consumption is reduced and heat sink size is minimized, but crossover distortion occurs at zero crossing points due to transmission delays
Solution Approach 1:
The patent applies preliminary action by generating a leading-edge pulse ahead of the zero-crossing point. This pulse is generated in advance (before the actual zero crossing occurs) to compensate for the transmission delay in the power amplifier stage. The leading pulse ensures that the output stage receives a signal early enough to reproduce the zero-crossing accurately, preventing crossover distortion while maintaining the efficiency benefits of switching amplification.
2Use of energy by moving object
If traditional pulse width modulation is used in switching amplifiers, then efficiency is improved, but small signal pulses near zero crossing are lost due to transmission delay
Solution Approach 1:
The patent generates a leading-edge pulse that occurs before the zero-crossing point, anticipating the delay in the power amplifier. This preliminary pulse ensures that the modulated signal is transmitted early enough to be accurately reproduced at the output, preventing loss of small signal pulses near the zero crossing while maintaining the high efficiency of switching amplification.
Data Source
AI summary
Embodiments of the present invention include switching amplifier circuits and methods. In one embodiment, the present invention includes an low distortion method of driving a switching amplifier comprising generating a first pulse width modulated signal on a first terminal, generating a second pulse width modulated signal on a second terminal, and delaying one of the first or second signals. In one embodiment, the modulated signals and delay result in pulse trains near zero crossings to reduce crossover distortion.