Switch Mode Power Converter Frequency Avoidance
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Solution Overview
Problem
In battery-powered portable electronic devices, switch mode DC-DC power converters generate electromagnetic interference (EMI) that can align with the operating frequencies of sensitive subsystems, causing interference, especially in space-constrained devices like smartphones and tablets, where practical EMI shielding or positioning of inductors is not feasible.
Innovation Solution
An adaptive circuit that monitors the switching frequency of the power converter and adjusts input parameters, such as inductor current limit or pulse timing, to avoid aligning with the operating frequencies of nearby sensitive subsystems, thereby reducing EMI without impacting power efficiency or increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the switch mode power converter operates in PFM mode with variable switching frequency to improve efficiency under light load conditions, then power efficiency is improved, but electromagnetic interference (EMI) may align with operating frequencies of sensitive subsystems causing interference
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable and adaptive rather than fixed. The controller dynamically modifies the switching frequency based on detected operating frequencies of sensitive subsystems, allowing the power converter to maintain high efficiency while avoiding EMI alignment issues. This is achieved through feedback mechanisms that continuously monitor and adjust the switching frequency in real-time operation.
Solution Approach 2:
The patent changes the switching frequency parameter adaptively to resolve the EMI problem. By detecting the operating frequencies of sensitive subsystems and adjusting the power converter's switching frequency away from these frequencies, the system maintains PFM mode efficiency benefits while avoiding harmful EMI alignment. The controller modifies frequency parameters based on system conditions and detected interference patterns.
2Object-affected harmful factors
If EMI shielding is added between the power converter circuitry and nearby sensitive circuits, then EMI interference is reduced, but device space is consumed
Solution Approach 1:
The patent extracts the EMI problem from the physical spatial domain and moves it to the frequency domain for resolution. Instead of adding physical shielding between components, the system detects operating frequencies of sensitive subsystems and adjusts the power converter's switching frequency to avoid alignment. This eliminates the need for additional EMI shielding materials or increased spacing between components.
Solution Approach 2:
The patent replaces the mechanical/physical approach of EMI shielding with an electronic/software-based frequency adjustment mechanism. The controller uses detection and control circuits to monitor operating frequencies and dynamically adjust switching frequency parameters, substituting physical barrier methods with intelligent frequency management that consumes no additional device space.
3Object-affected harmful factors
If spread spectrum techniques are used to randomize switching parameter and spread noise power across wider frequency range, then noise power at operating frequency is reduced, but noise floor is raised
Solution Approach 1:
The patent applies preliminary anti-action by proactively detecting the operating frequencies of sensitive subsystems before EMI alignment occurs. The system preemptively adjusts the switching frequency away from detected operating frequencies, preventing harmful alignment rather than attempting to mitigate it after the fact. This approach avoids the need to spread noise across wider ranges, maintaining a low noise floor while preventing interference.
Solution Approach 2:
The patent uses feedback mechanisms to detect operating frequencies of sensitive subsystems and continuously adjust the power converter's switching frequency in response. This closed-loop control allows the system to maintain optimal efficiency while avoiding EMI alignment, without requiring the noise spreading approach that raises the noise floor. The feedback ensures precise frequency management tailored to actual system conditions.
Data Source
AI summary
The switching frequency of a switch mode PFM power converter is compared with a predetermined frequency range that contains the operating frequency of a nearby clocked sub-system. In response to the switching frequency coming into the range, a parameter of the power converter is changed from an original value, so as to cause the switching frequency to go out of the range.