Power Controller Jitter Inducer for EMI Reduction
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Solution Overview
Problem
Conventional methods for reducing electromagnetic interference (EMI) in switch-mode power supplies through frequency jittering are inadequate as they often result in the switching frequency remaining at one or several specific frequencies, limiting the effectiveness of EMI reduction.
Innovation Solution
The implementation of a power controller with a jitter inducer that alters the peak current-sensing voltage by introducing a jitter current, which changes sign between consecutive switching cycles, thereby spreading the switching frequency across a broader spectrum to effectively reduce EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional frequency jittering is used to reduce EMI, then EMI reduction is achieved, but the switching frequency remains at one or several specific frequencies, limiting the effectiveness of EMI reduction
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The controller dynamically adjusts the switching frequency within a range around a center frequency, preventing the frequency from staying at one or several specific values. This dynamic frequency adjustment spreads the spectral energy across a broader range, effectively reducing EMI while maintaining adaptability.
Solution Approach 2:
The patent changes the frequency parameter from a fixed value to a variable range. By introducing frequency deviation from the center frequency and allowing the switching frequency to vary within a specified range, the patent transforms the static frequency parameter into a dynamic one, thereby spreading spectral distribution and reducing EMI effectiveness.
2Stability of the object's composition
If switching frequency is kept constant for stable operation, then operational stability is maintained, but EMI is concentrated at specific frequencies, reducing EMI reduction effectiveness
Solution Approach 1:
The patent resolves this contradiction by introducing controlled dynamics to the switching frequency. Instead of keeping the frequency completely constant, the system maintains stability around a center frequency while allowing dynamic variations within a specified range. This controlled dynamics spreads the EMI spectrum without compromising overall operational stability.
Solution Approach 2:
The patent employs periodic action through frequency jittering, where the switching frequency periodically varies around the center frequency. This periodic variation prevents EMI concentration at any single frequency while maintaining stable operation through the centered frequency reference, effectively distributing EMI energy across multiple frequency points.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly enhances EMI reduction by ensuring the switching frequency does not remain constant, effectively dispersing it across a wider range, thereby improving the overall efficiency of EMI mitigation in switch-mode power supplies.
Implementation Method 1
Transformer TF, an inductive device, has primary winding PRI, secondary winding SEC, and auxiliary winding AUX, inductively coupled to each other. As shown in FIG. 1, transformer TF provides direct-current (DC) isolation to separate a primary side from a secondary side.
Implementation Method 2
Quasi-resonant (QR) mode is a highly efficient mode of operation for power supplies where the turning-on of a power switch is synchronized with the point where the drain-to-source voltage of the power switch is at a local minimum (valley). In other words, QR mode performs valley switching to reduce switching loss and increase power conversion efficiency.
Implementation Method 3
The implementation of a power controller with a jitter inducer that alters the peak current-sensing voltage by introducing a jitter current, which changes sign between consecutive switching cycles, thereby spreading the switching frequency across a broader spectrum to effectively reduce EMI.
Data Source
AI summary
A power controller disclosed is for the use of a power converter with an inductive to regulate an output power source. The power controller has a PWM signal generator and a jitter inducer. The PWM signal generator controls a power switch to generate consecutive switching cycles. In each switching cycle the PWM signal generator controls a peak to regulate the output power source, and the peak is capable of representing a current flowing through the inductive device. The jitter inducer, connected to the PWM signal generator, is for altering the peak, so as to make a difference between two consecutive peaks. The difference has a sign and a magnitude. The jitter inducer makes the sign changed switching cycle by switching cycle.