A Frequency-Hopping Based Pulse Width Modulator for Spur Reduction in Switching Buck Converters
Subject Areas : electrical and computer engineering
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Abstract :
This paper presents an EMI reduction technique for switched-mode buck converters. To achieve this, the frequency hopping concept is utilized in asynchronous pulse width modulators (APWM) performing the power conversion with controlling the on-off time of the power switches. The modulator has an oscillatory behavior; such that its oscillation frequency depends on its internal loop delay. Making use of this property and randomly changing the loop delay between 8 distinct random values, its self-oscillation frequency is also changed between 8 different values. As a result, a spur-free spectrum is achieved at the output of the converter. To verify the usefulness of the proposed method, a model-based behavioral simulation was done using MATLAB-SIMULINK. The main advantage of the proposed method over previous works is that the switching frequency controlling mechanism is fully digital. Besides, it can be readily done without causing any disturbance in the carrier signal.
