DLL Delay Control for Accurate Duty Cycle Measurement

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Solution Overview

Problem

Conventional methods for determining the duty cycle of fast periodic digital signals are inaccurate due to bandwidth limitations and introduce distortions, requiring analog circuits and converters that increase errors and costs.

Innovation Solution

A digital solution using a delay locked loop (DLL) to delay the periodic signal based on digital control words, eliminating the need for analog voltage meters and reducing errors by accounting for unknown variables in the calculation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional analog methods are used to measure duty cycle of fast periodic digital signals, then measurement can be performed, but measurement precision deteriorates due to bandwidth limitations and signal distortions

Engineering Contradiction:

Improveduty cycle measurement accuracyVSAvoidbandwidth limitations and signal distortions

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the analog measurement system with a fully digital system. Instead of using analog voltage meters and filters that suffer from bandwidth limitations, the invention uses digital logic circuits (D-flip flops, counters, XOR gates) to capture and measure signal parameters. The periodic signal is sampled and processed in the digital domain where bandwidth constraints are eliminated, directly resolving the measurement accuracy problem caused by analog bandwidth limitations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces digital control words as intermediaries between the periodic signal and the measurement process. These control words are generated by digital circuits and used to control D-flip flops and counters, enabling precise measurement of duty cycle without direct analog measurement. This intermediary digital control mechanism avoids the signal distortions that plague direct analog measurement methods.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If analog circuits and converters are used for duty cycle measurement, then measurement functionality is achieved, but device complexity increases

Engineering Contradiction:

Improveduty cycle measurement capabilityVSAvoidanalog circuit components

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent eliminates analog circuits and converters by substituting them with digital logic components. The measurement functionality previously requiring analog voltage meters, filters, and ADCs is achieved using digital D-flip flops, counters, and logic gates. This substitution reduces device complexity by removing unnecessary analog components while maintaining measurement capability in the digital domain.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts and removes the analog measurement subsystem from the overall measurement system. By taking out the analog circuits and converters that contribute to device complexity, the invention creates a streamlined digital-only measurement system that achieves the same measurement functionality with fewer and simpler components.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If conventional analog measurement methods are used, then duty cycle can be determined, but reliability deteriorates due to introduced errors

Engineering Contradiction:

Improveduty cycle determinationVSAvoidmeasurement error

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the error-prone analog measurement system with a digital system that inherently provides higher reliability. Digital logic circuits provide stable, noise-immune measurement of signal parameters. The use of digital counters and logic gates to determine duty cycle eliminates the measurement errors introduced by analog bandwidth limitations and signal distortions, directly improving measurement reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs feedback mechanisms where the measured parameters are processed through digital logic circuits that can detect and correct measurement conditions. The digital system uses feedback from the signal edges to control D-flip flops and counters, ensuring accurate capture of signal parameters and reducing measurement errors through iterative verification and correction.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12066476B2Systems and methods for duty cycle measurement

Publication Date: 2024.08.20 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Systems, methods, and circuits for determining a duty cycle of a periodic input signal are provided. A delay element is configured to delay the periodic input signal based on a digital control word. A digital circuit is configured to generate a first digital control word used to delay the periodic input signal a first amount of time corresponding to a period of the periodic input signal, generate a second digital control word used to delay the periodic input signal a second amount of time corresponding to a portion of the periodic input signal having a logic-level high value, and generate a third digital control word used to delay the periodic input signal a third amount of time corresponding to a portion of the periodic input signal having a logic-level low value. A controller is configured to determine the duty cycle based on the first, second, and third digital control words.