Switching Circuit EMI Suppression via Discontinuous Frequency Modulation
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Solution Overview
Problem
Conventional power supply designs face challenges in reducing electromagnetic interference (EMI) emissions while minimizing the size, weight, and cost of components, as existing methods either increase component size, add weight, or compromise efficiency.
Innovation Solution
The EMI emission suppressing system modulates the frequency of a switching element when drawing power from the main supply to reduce EMI emissions, applying low frequency modulation only during power access and discontinuing it when not in use to minimize ripple on the load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the switching frequency is reduced below 150 KHz to reduce EMI emissions, then EMI emissions are reduced, but the size of magnetic components increases
Solution Approach 1:
The patent applies periodic frequency modulation to the switching element, alternating between different frequency states to spread EMI emissions across multiple frequency bands rather than concentrating them at a single frequency. This periodic action reduces peak EMI emissions without requiring reduction of the fundamental switching frequency, thereby avoiding increased magnetic component size
Solution Approach 2:
The patent dynamically changes the operating frequency parameter of the switching element through modulation, transforming the fixed-frequency operation into variable-frequency operation. This parameter change allows the system to maintain higher average switching frequencies for compact magnetic components while periodically varying the frequency to reduce EMI emissions below regulatory thresholds
2Object-generated harmful factors
If additional filter components are added to reduce unwanted frequency harmonics, then EMI emissions are reduced, but the weight and size of the power supply increase
Solution Approach 1:
The patent converts the harmful EMI emissions into a beneficial control mechanism by using frequency modulation to intentionally generate controlled spectral spreading. Instead of passively filtering unwanted harmonics with heavy filter components, the system actively manages EMI through frequency variation, turning potential interference into a controllable parameter that reduces emissions without adding weight
Solution Approach 2:
The patent extracts the EMI reduction function from passive filter components and implements it through active frequency control of the switching element. By removing the dependency on additional filter hardware and using control-theoretic frequency modulation instead, the system achieves EMI reduction without the weight penalty of extra filter components
3Object-generated harmful factors
If a snubber circuit is used to reduce large spikes of harmonics or EMI, then EMI emissions are reduced, but the efficiency of the power converter is compromised
Solution Approach 1:
The patent replaces the passive mechanical/electrical snubber circuit with an active control mechanism using frequency modulation. Instead of using resistive and capacitive elements that dissipate energy to suppress EMI spikes, the system uses intelligent frequency variation to prevent the formation of large harmonic spikes, thereby reducing EMI without the energy losses inherent in snubber circuits
4Object-generated harmful factors
If jitter is continuously injected into the gate drive to spread EMI over a continuous frequency range, then EMI emissions are reduced, but output voltage signal distortion and excessive ripple occur
Solution Approach 1:
The patent applies periodic frequency modulation at controlled intervals rather than continuous random jitter injection. This periodic action spreads EMI emissions across frequency bands in a predictable, controlled manner that maintains output voltage stability. The modulation is synchronized with the power converter's operating cycles, ensuring that EMI reduction does not compromise output ripple performance
Solution Approach 2:
The patent implements feedback control to monitor and adjust the frequency modulation depth and frequency based on operating conditions. This feedback mechanism ensures that EMI reduction through frequency modulation does not push the system into unstable regions that would cause excessive output ripple or voltage distortion, maintaining both EMI compliance and output stability
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
This approach effectively reduces EMI emissions below standard bandwidth limits without increasing component size or compromising efficiency, while minimizing ripple on the output signal.
Implementation Method 1
a frequency modulation element that modulates the frequency of a switching element when the switching element is drawing power from the main power supply in order to reduce EMI emissions on the main power supply
Data Source
AI summary
An EMI emission suppressing system, apparatus and method that enables the EMI produced by high frequency switching of a switching circuit to be suppressed via the transfer of the higher order harmonic emissions to a frequency range below the standard EMI bandwidth of less than 150 KHz by applying low frequency modulation or jitter into the feedback of a switching signal of the switching circuit. The EMI suppression is achieved with minimal added ripple on the output signal of the switching circuit by using discontinuous modulations in the form of only applying the low frequency modulation when the switch or higher order harmonic producing element of the switching circuit is accessing, or drawing power from, the main power supply.