Spread Spectrum Clock Switching for Display EMI Reduction
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Solution Overview
Problem
High-frequency clock signals in electronic devices cause electromagnetic interference (EMI) in devices in close proximity, necessitating a solution to minimize noise.
Innovation Solution
A display device and electronic device utilizing a spread spectrum clock generator that alternates between up-spread and down-spread methods at predetermined time intervals to generate output clock signals, incorporating a phase frequency detector, charge pump, loop filter, profile register, modulator, and voltage controlled oscillator to modulate the clock signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high-frequency clock signal is generated to process data at high speed, then the operating speed of electronic devices is improved, but electromagnetic interference is increased in electronic devices in close proximity
Solution Approach 1:
The patent applies periodic action by alternating between up-spread and down-spread methods at predetermined time intervals. The spread spectrum clock generator switches between different spread spectrum techniques periodically, which distributes the electromagnetic energy over time and frequency, reducing peak interference levels while maintaining high-speed data processing capability
Solution Approach 2:
The patent changes the frequency parameters of the clock signal by applying spread spectrum modulation. The up-spread method increases the frequency above the center frequency while the down-spread method decreases it, creating a frequency-modulated signal that distributes energy across a wider bandwidth, thereby reducing electromagnetic interference at any single frequency point
2Object-generated harmful factors
If a spread spectrum method is applied to reduce electromagnetic interference, then noise is minimized, but the clock signal frequency is modulated requiring additional circuit components
Solution Approach 1:
The patent merges the spread spectrum modulation function with the existing phase-locked loop (PLL) clock generation circuitry. The modulator is integrated into the PLL structure, allowing the spread spectrum method to be applied without requiring completely separate modulation circuits, thus reducing overall device complexity while still achieving noise reduction
Solution Approach 2:
The spread spectrum clock generator is designed to perform multiple functions: it generates the clock signal, applies spread spectrum modulation, and alternates between up-spread and down-spread methods. This multi-functional design eliminates the need for separate circuits for each function, reducing device complexity while maintaining effective noise minimization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces electromagnetic interference by distributing energy across a wider frequency bandwidth, lowering peak values and minimizing noise in electronic devices.
Implementation Method 1
a voltage controlled oscillator that generates a frequency-modulated output clock signal using the voltage modulated by the modulator
Implementation Method 2
a phase frequency detector that receives the input clock signal and a divided clock signal and outputs a phase frequency signal representing a phase difference and/or a frequency difference between the input clock signal and the divided clock signal
Implementation Method 3
a loop filter that filters the voltage and/or current
Data Source
AI summary
An electronic device including a spread spectrum clock generator that generates an output clock signal using an input clock signal, wherein the spread spectrum clock generator generates the output clock signal using a different spread spectrum method at a predetermined time interval.