PWM Decoding Circuit Using Duty Cycle Instead of Rising Edge Detection
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Solution Overview
Problem
Existing decoding circuits for PWM signals face challenges in accurately detecting the position of rising edges, leading to inaccuracies in determining logic values due to variations in signal frequency and period lengths.
Innovation Solution
A decoding circuit comprising section information, period information, and reference information generation units, along with a comparison unit, directly measures the period of the input signal and generates reference information to accurately determine logic values by comparing section information with the reference, improving decoding accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PWM signal decoding is performed by detecting rising edge position, then decoding can be implemented, but decoding accuracy deteriorates due to signal frequency and period variations
Solution Approach 1:
The patent changes the decoding parameter from rising edge position detection to duty cycle measurement. By measuring the high-level and low-level time periods and calculating the duty cycle ratio, the system achieves accurate decoding independent of signal frequency and period variations. The duty cycle becomes the invariant parameter for data determination.
Solution Approach 2:
The patent introduces period information and reference information as intermediary elements. The period information generation unit measures the total period, the reference information generation unit divides it by a given value to create a reference, and the comparison unit uses these intermediaries to determine logic values. This intermediary approach enables accurate decoding without directly detecting rising edges.
2Adaptability or versatility
If rising edge position is used to determine logic values, then decoding is achieved, but accuracy deteriorates under frequency variations
Solution Approach 1:
The system transitions from using absolute time position (rising edge location) to using relative time ratio (duty cycle). By comparing high-level period and low-level period to determine logic values, the system adapts to frequency variations while maintaining precise logic value determination. The duty cycle ratio remains constant regardless of frequency changes.
3Ease of operation
If PWM decoding relies on rising edge detection, then signal interpretation is possible, but measurement accuracy decreases
Solution Approach 1:
The patent segments the PWM period into high-level period and low-level period measurements. By separately measuring the duration of high and low levels and comparing them, the system achieves accurate decoding without relying on precise rising edge detection. This segmentation approach simplifies the measurement process while improving accuracy.
Data Source
AI summary
A decoding circuit may include a section information generation unit suitable for generating section information corresponding to a section in which an input signal has a first value, a period information generation unit suitable for generating period information corresponding to a period of the input signal, a reference information generation unit suitable for generating reference information by dividing a value of the period information by a given value, and a comparison unit suitable for determining a logic value of the input signal by comparing the section information with the reference information.