Clock Switching Circuit for Interference-Free Frequency Changes

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Solution Overview

Problem

Existing switching circuits cannot seamlessly switch between two fixed clock frequencies (F1 and F2) and a new frequency (F3) without generating interference, which is necessary in electronic circuits that require distinct frequency processing, and this cannot be done without modifying the existing circuitry.

Innovation Solution

A clock switching circuit utilizing a frequency detector, D flip-flop, and NOR logic gate to resynchronize the clock signals, allowing switching between F1 and F3 without interference by filtering frequencies F1 and F2 and using a control signal to manage the switching process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a switching circuit is designed to switch between two fixed clock frequencies F1 and F2, then the switching function is achieved, but the circuit cannot accommodate a new frequency F3 without modification

Engineering Contradiction:
Improvefrequency switching capabilityVSAvoidcircuit modification requirement
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The frequency detector is designed to detect multiple clock frequencies (F1, F2, and F3) rather than being limited to a single fixed frequency. This multi-functionality allows the switching circuit to adapt to different frequency requirements without hardware modification, resolving the contradiction between versatility and complexity by making the detection mechanism universal.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The switching circuit transitions from a static configuration with fixed frequency pairs to a dynamic system where the frequency detector can identify any of multiple frequencies and the switch can respond accordingly. This dynamic adaptation allows the circuit to handle new frequencies F3 without structural changes, maintaining simplicity while improving versatility.

Inventive Principle:
Principle #15Dynamics

2Adaptability or versatility

If clock switching is performed between different frequencies, then frequency flexibility is achieved, but interference is generated that disturbs processor operation

Engineering Contradiction:
Improveclock frequency switchingVSAvoidswitching interference
Core Design Contradiction:
Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The frequency detector continuously monitors the clock signal frequency in advance before switching is needed. By detecting the current frequency F1 or F3 ahead of time, the system can prepare for the transition and execute the switch at the appropriate moment, reducing abrupt transitions that cause interference and protecting processor operation.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The switching circuit incorporates feedback through the frequency detector that continuously monitors the clock signal and provides information about the current frequency state. This feedback mechanism allows the system to adjust the switching timing and control signals accordingly, minimizing interference during frequency transitions while maintaining processor stability.

Inventive Principle:
Principle #23Feedback

3Measurement precision

If a frequency detector is added to enable frequency-based switching control, then switching precision is improved, but device complexity increases

Engineering Contradiction:
Improvefrequency detection accuracyVSAvoidcircuit component count
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The frequency detector is integrated into the existing switching circuit architecture rather than being completely separate. The detector shares the clock signal input and works in conjunction with the existing switch and control logic, merging multiple functions into a unified structure. This reduces overall complexity compared to having completely separate detection and switching systems.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The frequency detector uses the existing clock signal F1/F3 that is already present in the system to perform its detection function, rather than requiring an external reference signal or additional test inputs. The circuit essentially detects its own operating state using available resources, reducing the need for external components and simplifying the overall system architecture.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP2326004B1Circuit for undisturbed clock signal switching
Publication Date: 2012.03.14 THALES SA
  • EP2326004B1 patent drawingFigure 1
  • EP2326004B1 patent drawingFigure 2
  • EP2326004B1 patent drawingFigure 3

AI summary

The circuit has a NOX logic gate (104) for outputting the synchronization signal (105) according to NOX logic function between clock signals (101, 102). A D flip-flop type logic circuit (106) receives the signal (105) and a signal (108) from a frequency detector (107), and produces a control signal (109) at the destination of a clock switch (103) piloting the switching between the signals (101, 102), such that a clock signal (110) is equal to the signals (101, 102) when the frequency of the signal (101) is equal to low and high clock frequencies (F1, F2) of the signal (101), respectively.