Oscillator Reference-Signal Jittering for EMI Reduction
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Solution Overview
Problem
Existing methods for reducing electromagnetic interference (EMI) in consumer electronic devices through frequency jittering of switching power supplies require significant chip area, which is inefficient.
Innovation Solution
A frequency-jittering apparatus comprising an oscillator and a frequency control circuit that operates in different states based on signal magnitude comparisons, varying the reference signal to change the signal frequency, thereby achieving frequency jittering without the need for large chip areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency jittering is implemented using prior art methods, then EMI is reduced, but chip area increases considerably
Solution Approach 1:
The patent changes the operational parameters of the oscillator by varying the reference signal frequency dynamically. The frequency control circuit adjusts the reference signal frequency based on predetermined criteria, causing the oscillator to operate at different frequencies within a range rather than a fixed frequency. This parameter variation achieves frequency jittering that reduces EMI while using minimal additional circuitry
Solution Approach 2:
The patent implements dynamic frequency adjustment where the oscillator's operating frequency is not fixed but varies over time according to the reference signal. The frequency control circuit continuously or periodically modifies the reference signal frequency, creating a dynamic frequency jittering effect that disperses electromagnetic energy across multiple frequencies, thereby reducing EMI without requiring large chip area
Data Source
AI summary
A frequency-jittering apparatuses includes an oscillator and a frequency control circuit. The oscillator generates a signal. When the magnitude of the signal exceeds a magnitude of a reference signal, the oscillator operates substantially in a first state; and when the magnitude of the signal is lower than the magnitude of the reference signal, the oscillator operates substantially in a second state different from the first one. The frequency control circuit varies the reference signal to change the frequency of the signal output from the oscillator.