PLL Frequency Jittering Circuit for Lower-Complexity EMI Control
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Solution Overview
Problem
Conventional frequency jittering control circuits employing digital counters are complex, costly, and inefficient in reducing electromagnetic interference (EMI) due to their large size and requirement for multiple current source devices.
Innovation Solution
A frequency jittering control circuit that utilizes a phase lock loop (PLL) with switching between two or more oscillators to generate a smoother and more random frequency jitter, eliminating the need for a digital counter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a digital counter is used to achieve frequency jittering, then frequency shifting can be achieved, but the circuit complexity and area increase significantly
Solution Approach 1:
The patent extracts and removes the digital counter component from the frequency jittering control circuit, replacing it with a simpler oscillator-based solution that achieves the same frequency shifting function without requiring complex counting logic or multiple current source devices
Solution Approach 2:
The patent uses an oscillator to generate frequency variations that copy or simulate the effect of a digital counter, but through analog signal generation rather than digital counting, thereby achieving frequency jittering with reduced circuit complexity
2Reliability
If a digital counter is used for frequency jittering, then frequency control is achieved, but the circuit area and cost increase
Solution Approach 1:
The patent merges the frequency control function with the oscillator operation, combining what would traditionally be separate components (counter and current source control) into a unified oscillator-based frequency generation approach that occupies less circuit area
Solution Approach 2:
The oscillator serves multiple functions simultaneously: it generates the base frequency signal and also produces the frequency variations needed for jittering, eliminating the need for separate counter and control circuitry that would increase circuit area
3Reliability
If sequential or random counts are generated by a digital counter, then frequency shifting is achieved, but the anti-EMI effect is less effective
Solution Approach 1:
The patent implements dynamic frequency variation through the oscillator, creating continuous and unpredictable frequency changes that more effectively disrupt EMI patterns compared to the discrete, structured counting sequences of a digital counter
Solution Approach 2:
The oscillator generates periodic frequency variations that create a more effective anti-EMI pattern through continuous sinusoidal or near-sinusoidal frequency modulation, which is more disruptive to electromagnetic interference than the step-wise frequency changes from digital counting
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 provides a more efficient and cost-effective anti-EMI effect by generating a smoother and more random frequency spectrum, reducing circuit complexity and improving EMI mitigation.
Implementation Method 1
The present invention takes advantage of the characteristics of a phase lock loop (PLL) in a very inventive way; by switching the input frequency of the PLL, the output frequency of the PLL swings between two frequency limits to provide the desired frequency jittering function
Data Source
AI summary
A frequency jittering control circuit wherein by means of the characteristics of a PLL whose input switches between different frequencies, the output frequency of the PLL swings between the different frequencies to achieve the desired frequency jittering.