Switching Mode Power Supply Spectrum Shaping Circuit
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Solution Overview
Problem
High switching frequencies in switching mode power supplies generate severe electromagnetic interference (EMI), which affects electronic equipment and interferes with radio waves, and existing solutions are not adaptable to variable switching frequencies.
Innovation Solution
A switching mode power supply with a feedback circuit that generates a feedback signal related to the load on the secondary winding, a switching circuit to control current flow through the primary winding, and a control circuit that includes a spectrum shaping circuit to regulate the switching frequency and spectrum shaping range based on the feedback signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high switching frequency is used to achieve small volume and high efficiency, then power density and efficiency are improved, but electromagnetic interference becomes severe
Solution Approach 1:
The patent applies dynamics by making the spectrum shaping range variable rather than fixed. The control circuit dynamically adjusts the spectrum shaping range according to the actual switching frequency, allowing the power supply to adapt to different operating conditions and maintain EMI reduction effectiveness across variable frequency ranges while preserving high switching frequency benefits
Solution Approach 2:
The patent changes the parameter of spectrum shaping range from a fixed value to a variable parameter that adjusts with switching frequency. By modifying this parameter dynamically, the system resolves the contradiction between maintaining high switching frequency for efficiency and reducing EMI through appropriate spectrum shaping
2Object-generated harmful factors
If fixed spectrum shaping range is used to reduce EMI, then electromagnetic interference is reduced, but adaptability to variable switching frequency is lost
Solution Approach 1:
The patent implements feedback by having the control circuit monitor the actual switching frequency and use this information to adjust the spectrum shaping range accordingly. This closed-loop feedback mechanism ensures the spectrum shaping remains effective regardless of switching frequency variations, resolving the adaptability issue
Solution Approach 2:
The system transitions from a static fixed spectrum shaping range to a dynamic variable spectrum shaping range that responds to switching frequency changes, thereby achieving both EMI reduction and adaptability to variable operating conditions
Data Source
Figure 1
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Figure 3a~3b
AI summary
The present invention discloses a switching mode power supply with spectrum shaping. The spectrum range of the switching frequency of the switching mode power supply varies with the switching frequency. The spectrum shaping range becomes narrower if the switching frequency decreases, and it becomes broader if the switching frequency increases.