PWM Clipping Detection Circuit for Frequency-Independent Thresholding
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Solution Overview
Problem
Conventional amplifier circuits face challenges in accurately determining the clipping state of output signals, which leads to distortion, especially when the frequency of the input signal is high, and requires waiting for a certain duration to make clip determinations, resulting in frequency-dependent clip determination with varying threshold values.
Innovation Solution
A clipping state detecting circuit that includes a zero-cross detection circuit, a class D amplifier, and a clip detection circuit, which measures clip and non-clip times using reference clock signals to determine the clipping state based on a threshold value set as a ratio between these times, allowing for frequency-independent clip determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If clip determination is performed by waiting for a certain period of time, then the accuracy of clipping state detection is improved, but the response time increases and frequency dependence occurs
Solution Approach 1:
The patent changes the parameter used for clip determination from a fixed time period to a time period calculated based on the period of the input signal. Specifically, the clip determination time period is set to a predetermined proportion of the input signal period, which allows the measurement to be completed quickly while maintaining accuracy by adapting to the signal's frequency characteristics.
2Device complexity
If a fixed time period is used for clip determination, then the detection method is simple, but frequency dependence occurs and threshold values vary
Solution Approach 1:
The patent applies dynamics by making the clip determination time period variable rather than fixed. The time period is dynamically adjusted based on the period of the input signal, ensuring that the determination window adapts to different frequencies. This eliminates frequency dependence while maintaining a relatively simple detection method.
Solution Approach 2:
The patent uses feedback from the input signal period to adjust the clip determination time period. By detecting the period of the input signal and using it to set the appropriate determination window, the system ensures consistent threshold values across different frequencies, improving reliability without significantly increasing complexity.
3Speed
If the input signal frequency is high, then the amplifier can handle faster signals, but clip determination becomes less accurate with fixed time methods
Solution Approach 1:
The patent makes the clip determination time period dynamic by basing it on the input signal period. For high-frequency signals with shorter periods, the determination window is automatically reduced proportionally, allowing accurate clip detection to be completed within the available time. This maintains measurement precision across a wide range of signal frequencies.
Data Source
AI summary
According to one embodiment, a clipping state detecting circuit includes: a zero-cross detection circuit that detects a zero-cross point of an input signal; an output circuit that converts the input signal into a PWM signal; a clip detection circuit that detects a state in which an output of the output circuit is clipped; and a control circuit that determines a state is a clipping state when a clip time of the output of the output circuit satisfies a condition of a threshold value set in advance with respect to a non-clip time.