PWM Audio Signal Processing to Avoid Double Switching Frequency
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Solution Overview
Problem
Class D amplifiers experience a 'double switching frequency' issue in ternary mode, leading to increased distortion, electromagnetic interference (EMI), and power consumption when the pulse width of output signals is large.
Innovation Solution
An electronic device comprising a first sampling circuit and a first summing circuit that samples the pulse width of a first input pulse of a PWM input signal and generates an output pulse whose pulse width is the summation of the input pulse widths, thereby maintaining consistent switching frequency with the triangle-wave signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the pulse width of output signal is large in T-mode, then the output signal can represent larger voltage levels, but the switching frequency would be doubled leading to increased distortion and EMI
Solution Approach 1:
The patent applies dynamics by making the switching frequency adaptive rather than fixed. The control circuit dynamically adjusts the switching frequency based on the pulse width of the output signal. When the pulse width is large, the system automatically reduces the switching frequency to avoid double switching, thereby reducing EMI and distortion while maintaining the ability to represent large voltage levels.
Solution Approach 2:
The patent changes the switching frequency parameter dynamically based on the pulse width condition. Instead of maintaining a constant switching frequency, the system modifies this critical parameter in response to varying signal conditions, specifically reducing frequency when pulse width exceeds certain thresholds to prevent harmful double switching effects.
2Adaptability or versatility
If the switching frequency is doubled to accommodate large pulse widths, then the output signal can cover wider dynamic range, but the power consumption (switching loss) is increased
Solution Approach 1:
The system dynamically adjusts switching frequency based on signal requirements. When large pulse widths are needed for wide dynamic range, the frequency is reduced accordingly, preventing unnecessary double switching and the associated power consumption. This dynamic adaptation allows the system to maintain versatility while optimizing energy efficiency.
Solution Approach 2:
The switching frequency parameter is changed dynamically in response to pulse width conditions. The control circuit monitors output signal characteristics and adjusts frequency to match actual needs, avoiding excessive frequency doubling that would increase power consumption while still supporting the required dynamic range.
Data Source
AI summary
An electronic device includes a sampling circuit and a summing circuit coupled with the sampling circuit. The sampling circuit samples a pulse width of a first input pulse of a PWM input signal since a first time point on a rising edge of a clock pulse of a clock signal. The summing circuit generates a first output pulse of a PWM output signal since a second time point on a falling edge of the clock pulse. A pulse width of the first output pulse is a summation of the pulse width of the first input pulse and a pulse width of a second input pulse of the PWM input signal, and the second input pulse is the next pulse after the first input pulse.