Adaptive Jitter Control Circuit for Power Supply EMI and Ripple
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Solution Overview
Problem
Existing frequency jittering methods in switching power supply circuits, particularly in quasi-resonant valley conduction mode, fail to adjust amplitude according to load conditions, leading to suboptimal EMI performance due to large frequency jitter amplitudes and limited frequency ranges, which affect output ripple and EMI optimization.
Innovation Solution
A control circuit with an adaptive amplitude jitter generation circuit, comparison circuit, and trigger circuit that generates periodic amplitude jitter signals based on feedback voltage, allowing for automatic adjustment of frequency jitter amplitude according to load conditions, thereby optimizing EMI performance by varying the amplitude of frequency jitter in response to changing load demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a fixed amplitude frequency jittering method is used, then EMI noise amplitude is reduced, but the frequency jitter amplitude cannot be adjusted according to different loads, resulting in large output ripple under light load conditions
Solution Approach 1:
The patent applies dynamics by making the frequency jitter amplitude adjustable and adaptive to different load conditions. The control circuit dynamically changes the jitter amplitude based on load detection, transitioning from a static fixed amplitude system to a dynamic adaptive system that optimizes EMI reduction across varying operating conditions.
Solution Approach 2:
The patent implements parameter changes by modifying the frequency jitter amplitude parameter according to load conditions. The control circuit detects load changes and adjusts the jitter amplitude parameter accordingly, enabling the system to maintain optimal EMI performance across different power levels without introducing large ripples under light load.
2Object-affected harmful factors
If a large frequency jittering amplitude is used, then EMI optimization effect is improved, but output ripple becomes very large under light load conditions
Solution Approach 1:
The patent uses parameter changes to adjust the frequency jitter amplitude based on load conditions. Under light load, the jitter amplitude is reduced to prevent large output ripple, while under heavy load, the amplitude is increased to achieve better EMI optimization, thus dynamically optimizing both EMI performance and output ripple characteristics.
Solution Approach 2:
The system transitions from a static large amplitude jittering approach to a dynamic adaptive approach where the jitter amplitude is continuously adjusted according to load detection. This dynamic control enables the system to achieve strong EMI optimization under heavy load while maintaining clean output under light load conditions.
3Object-affected harmful factors
If frequency jittering is superimposed on current sampling value, then frequency jitter is achieved, but the method cannot adjust jitter amplitude according to load and affects EMI performance
Solution Approach 1:
The patent modifies the parameter adjustment approach by changing from a fixed superimposed amplitude method to a load-adaptive parameter change method. The control circuit detects load conditions and adjusts the jitter amplitude parameter accordingly, enabling the system to maintain effective frequency jittering while adapting to different power levels and load characteristics.
Solution Approach 2:
The patent implements feedback by detecting load conditions and using this information to adjust the frequency jitter amplitude. The control circuit continuously monitors load changes and feeds this information back to the jitter generation circuit, enabling real-time optimization of jitter amplitude to match actual power supply conditions and improve EMI performance.
Data Source
AI summary
A control circuit for controlling power switch in switching power supply circuit. The optimization circuit comprises an adaptive amplitude jitter generating circuit, a comparison circuit and a trigger circuit. The adaptive amplitude jitter generating circuit is used to generate a periodic amplitude jitter signal according to the feedback voltage signal indicative of the output of the switching power supply circuit. The comparison circuit is used to compare the sampled voltage signal with periodic amplitude jitter signal, and generate an output signal with periodic fluctuations. The trigger circuit is used for outputting the control signal for driving the power switch according to the output signal with periodic fluctuations and the clock signal.