Switched-Mode Power Supply Frequency Spread for EMI Reduction
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Solution Overview
Problem
Switching power supplies face challenges in electromagnetic compatibility, particularly in avoiding interference with desired radio frequencies during operation, which affects the reception of high-frequency signals.
Innovation Solution
A system comprising a microcontroller and a switched-mode power supply with a clock generator that can generate a clock signal of any selected frequency, using a random number generator to spread the frequency and minimize electromagnetic interference, allowing the clock frequency to be precisely adjusted to avoid interfering with the desired frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a switching power supply operates at a fixed frequency, then the power supply achieves stable and efficient operation, but it generates electromagnetic interference at specific frequency bands that can disrupt radio reception
Solution Approach 1:
The patent implements dynamic frequency adjustment of the switching power supply by using a frequency counter to monitor the received signal frequency and automatically adjusting the switching frequency to avoid interference. The control unit modifies the switching frequency based on the detected radio frequency, transforming the fixed-frequency system into a dynamically adaptive one that eliminates electromagnetic interference while maintaining stable operation.
Solution Approach 2:
The patent changes the operating parameter (switching frequency) of the power supply based on the detected radio frequency. By varying the switching frequency away from the received signal frequency and its harmonics, the system prevents electromagnetic interference while maintaining efficient power conversion. This parameter adaptation resolves the contradiction between stable operation and electromagnetic compatibility.
2Object-affected harmful factors
If the switching frequency is adjusted to avoid interfering with received signals, then electromagnetic compatibility improves, but the complexity of the power supply control system increases
Solution Approach 1:
The microcontroller serves multiple functions: it controls the switching power supply, generates the clock signal for frequency adjustment, and implements the frequency detection and avoidance logic. By consolidating these functions into a single control unit, the system achieves electromagnetic compatibility without proportionally increasing overall system complexity, as the same hardware resources are utilized for multiple purposes.
Solution Approach 2:
The system employs a feedback mechanism where the frequency counter continuously monitors the received signal frequency and feeds this information back to the control unit. The control unit then adjusts the switching frequency accordingly, creating a closed-loop system that automatically maintains electromagnetic compatibility. This feedback approach simplifies the control strategy compared to complex pre-programmed avoidance schemes.
3Object-affected harmful factors
If a frequency counter and control unit are added to detect and avoid interfering frequencies, then electromagnetic compatibility improves, but the device complexity and cost increase
Solution Approach 1:
The microcontroller is designed to perform multiple functions including frequency detection via its built-in frequency counter, clock signal generation, and switching control. By utilizing the inherent capabilities of the microcontroller for frequency measurement and manipulation, the system avoids adding separate dedicated frequency detection and control circuits, thereby minimizing the increase in device complexity and cost while achieving electromagnetic compatibility.
Data Source
Figure 1
AI summary
The switched mode power supply has a switch (SW) as actuator for influencing an output voltage (U-OUT) of the switched mode power supply (SN), whose switching position depends on a switch control signal (U-ST). The control unit (CTU) is formed for generating the switch control signal depending on a clock pulse (CLK), which is fed external to the switched mode power supply over a clock pulse signal input of the switched mode power supply. An independent claim is also included for system with a switched mode power supply.