Power Converter PWM Frequency Modulation for EMI Reduction
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Solution Overview
Problem
Switched-mode power converters often experience electromagnetic interference (EMI) issues due to a constant switching frequency when power consumption is relatively constant, leading to inefficiencies and potential interference.
Innovation Solution
Modulating the switching frequency of the electronic switch in a PWM mode based on the voltage level of the input voltage, using a control circuit to adjust the on-time and off-time of the switch cycles, and employing a feedback signal that varies with the input voltage to optimize switching frequency and reduce EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching frequency is kept constant for stable power conversion, then the power converter operates reliably, but electromagnetic interference (EMI) issues occur
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control circuit dynamically changes the switching frequency based on detected EMI levels, allowing the system to adapt to different operating conditions and minimize electromagnetic interference while maintaining reliable power conversion operation.
Solution Approach 2:
The patent changes the switching frequency parameter in response to detected EMI conditions. When EMI exceeds a threshold, the control circuit modifies the switching frequency to a different value, thereby reducing electromagnetic interference while continuing to provide stable power conversion.
2Object-generated harmful factors
If the switching frequency is modulated to reduce EMI, then electromagnetic interference is reduced, but the complexity of the control circuit increases
Solution Approach 1:
The patent employs feedback by using an EMI detection circuit to monitor electromagnetic interference levels and feed this information back to the control circuit. The control circuit then adjusts the switching frequency based on the detected EMI levels, creating a closed-loop system that reduces EMI without requiring complex predetermined control algorithms.
Solution Approach 2:
The system performs self-service by automatically detecting EMI conditions and adjusting its own switching frequency through the control circuit. This self-regulating mechanism reduces EMI without requiring external intervention or complex external control systems.
Data Source
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AI summary
A method and a control circuit for operating an electronic switch (21) in a switching circuit (2) of a power converter are disclosed. The method includes operating the electronic switch (21) in a PWM mode, and modulating the switching frequency in the PWM mode dependent on a voltage level of an input voltage (Vin) received by the switching circuit (2).