Adaptive Frequency Jittering Circuit for Switching Power Supply EMI
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Solution Overview
Problem
Frequency jittering control in switching power supplies can lead to higher conduction loss, lower system efficiency, and increased electromagnetic radiation due to variations in switching frequency, which can result in suboptimal suppression of electromagnetic interference (EMI).
Innovation Solution
A new frequency jittering control approach is implemented, where the amplitude of the frequency jittering signal is adaptively controlled to be proportional to the switching period and inversely proportional to the sum of conduction time and demagnetization time of the inductor, ensuring a fixed jittering range of the switching frequency across different load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency jittering control is implemented in switching power supplies, then electromagnetic interference suppression is improved, but conduction loss increases and system efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable rather than fixed. The controller dynamically changes the switching frequency within a range to suppress EMI while optimizing efficiency. The frequency is modulated according to system conditions, allowing the power supply to adapt between fixed-frequency operation (for efficiency) and frequency-jittering operation (for EMI suppression), thus resolving the contradiction between EMI suppression and energy loss.
2Object-affected harmful factors
If frequency jittering control is implemented in switching power supplies, then electromagnetic interference suppression is improved, but system efficiency decreases
Solution Approach 1:
The system dynamically adjusts operating parameters including switching frequency and duty cycle based on real-time conditions. The controller can switch between fixed-frequency mode (higher efficiency) and frequency-jittering mode (better EMI suppression), optimizing the trade-off between productivity and harmful factor suppression.
Solution Approach 2:
The patent changes key operating parameters (switching frequency, duty cycle) to resolve the contradiction. By modulating the switching frequency within a controlled range and adjusting the duty cycle accordingly, the system achieves EMI suppression while minimizing the impact on system efficiency, thus resolving the contradiction between EMI performance and productivity.
3Object-affected harmful factors
If frequency jittering control is implemented in switching power supplies, then electromagnetic interference suppression is improved, but electromagnetic radiation increases
Solution Approach 1:
The system dynamically controls switching frequency and duty cycle to suppress conducted EMI while minimizing electromagnetic radiation. By using frequency modulation within a controlled range rather than extreme frequency switching, the system reduces voltage spikes and current harmonics that cause radiation, thus resolving the contradiction between conducted EMI suppression and electromagnetic radiation generation.
Solution Approach 2:
The patent optimizes parameter changes (frequency and duty cycle) to achieve EMI suppression while controlling radiation. The controlled frequency modulation range and duty cycle adjustment prevent excessive voltage and current variations, thereby reducing electromagnetic radiation while maintaining conducted EMI suppression performance.
Data Source
AI summary
A controller of a switching power supply can include: a frequency-jittering control circuit configured to generate a frequency-jittering signal adaptively; a comparator having two input terminals for respectively receiving an inductor current sampling signal and a feedback control signal, and being configured to compare the signals of the two input terminals to generate a switching control signal, in order to control a power transistor in the switching power supply; and a superimposing circuit configured to superimpose the frequency-jittering signal on one of the two input terminals of the comparator, where a switching frequency of the switching power supply varies within a preset range under different load conditions.