SMPS Controller Frequency Staggering for EMI Reduction
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Solution Overview
Problem
Conventional switching mode power supplies (SMPS) face challenges in reducing electromagnetic interference (EMI) due to switching noise, which increases production costs and disrupts operations of peripheral electronic devices, as users have limited control over the switching frequency of power switches.
Innovation Solution
An SMPS with a controller that generates a ramp signal and clock signal based on supply voltage changes, using a frequency staggering signal to adjust the switching frequency of the power switch, allowing for user-controlled frequency modulation through a simple structure that includes a frequency staggering signal generator, oscillator, and supply voltage controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter is added to block EMI, then electromagnetic interference is reduced, but production cost increases
Solution Approach 1:
The patent converts the harmful switching noise into a beneficial frequency modulation mechanism. By detecting the switching noise and using it to generate a frequency staggering signal, the system dynamically adjusts the switching frequency to avoid EMI problems rather than blocking them with filters, thereby reducing production costs while maintaining EMI performance
Solution Approach 2:
The patent introduces a frequency staggering signal generator as an intermediary component that processes the switching noise and converts it into frequency modulation control signals. This intermediary mechanism transforms the direct harmful effect into a controlled frequency variation, eliminating the need for external EMI filters
2Object-affected harmful factors
If switching frequency is changed to block EMI, then electromagnetic interference is reduced, but user control over frequency is lost
Solution Approach 1:
The patent implements a feedback mechanism where the switching noise is detected and fed back to the frequency staggering signal generator. This closed-loop system automatically adjusts the switching frequency based on the detected noise characteristics, providing intelligent EMI reduction while maintaining user control through the controller interface
Solution Approach 2:
The system performs self-adjustment by automatically detecting its own switching noise and using that information to modulate its frequency. This self-service mechanism eliminates the need for external EMI filters while preserving user control capabilities through the integrated controller
3Speed
If passive elements or digital circuits are used for frequency change, then switching frequency can be adjusted, but device complexity increases
Solution Approach 1:
The patent merges the frequency adjustment function with the existing controller by integrating the frequency staggering signal generator within the controller architecture. This consolidation eliminates the need for separate passive elements or digital circuits, reducing device complexity while maintaining frequency adjustment capabilities
Solution Approach 2:
The controller is designed to perform multiple functions: it generates the frequency staggering signal, detects switching noise, modulates the switching frequency, and maintains user control interfaces. This multi-functional approach eliminates the need for dedicated frequency adjustment circuits, thereby reducing overall device complexity
Data Source
AI summary
The present invention relates to a switching mode power supply and a driving method thereof. In the present invention, a supply voltage is generated by using a start voltage that corresponds to input power, and a switching operation frequency of a power switch is changed according to an increase/decrease of the supply voltage.