This paper investigates the application of a limited pool random pulse-width modulation algorithm to digitally controlled dc-dc power converters. The randomisation action affects the switching period, so the system realizes a random carrier frequency modulation with fixed duty cycle (RCFMFD). The use of a suitably selected small number of switching frequencies ensures the generation of a flat and well spread spectrum while limiting system complexity. Due to its simple implementation, this solution results to be very interesting from the Integrated Circuit (IC) point of view. The generation of the random number stream is based on a simple Linear Feedback Shift Register. The quality of the output voltage regulation is not affected by the random DPWM thanks to the position of the width modulated pulses in the middle of the switching period. The definition of the switching frequencies pool and the evaluation of system performances has been realized using a detailed time based model of a Spectrum Analser. Experimental results on a dc-dc synchronous buck converter, where the digital control has been implemented in Field Programmable Gate Array (FPGA), confirm the effectiveness of the proposed solution.

Limited-Pool Random Carrier-Frequency Pulse Width Modulation for Digitally Controlled DC-DC Converters

MATTAVELLI, PAOLO;ZIGLIOTTO, MAURO
2006

Abstract

This paper investigates the application of a limited pool random pulse-width modulation algorithm to digitally controlled dc-dc power converters. The randomisation action affects the switching period, so the system realizes a random carrier frequency modulation with fixed duty cycle (RCFMFD). The use of a suitably selected small number of switching frequencies ensures the generation of a flat and well spread spectrum while limiting system complexity. Due to its simple implementation, this solution results to be very interesting from the Integrated Circuit (IC) point of view. The generation of the random number stream is based on a simple Linear Feedback Shift Register. The quality of the output voltage regulation is not affected by the random DPWM thanks to the position of the width modulated pulses in the middle of the switching period. The definition of the switching frequencies pool and the evaluation of system performances has been realized using a detailed time based model of a Spectrum Analser. Experimental results on a dc-dc synchronous buck converter, where the digital control has been implemented in Field Programmable Gate Array (FPGA), confirm the effectiveness of the proposed solution.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/1558346
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