Patent ID: 8278843
Filing Date: 2012-10-02
Classification: H02M

Abstract:
1. A method of operating a switching-mode power supply, comprising: providing a switching element; providing a switching signal with a variable switching frequency, the switching element being switched on and off by the switching signal; predefining a frequency bandwidth in order to comply with EMC (electromagnetic compatibility) regulations, wherein average levels of a frequency spectrum of the switching signal are determined within the frequency bandwidth; modulating the switching frequency at a modulation frequency greater than the frequency bandwidth; predefining a lower threshold frequency in order to determine a maximum level of the frequency spectrum of the switching signal; setting a critical harmonic of a frequency spectrum of the switching signal without switching frequency modulation as a function of a pulse duty factor of the switching signal, the frequency of the harmonic being greater than the threshold frequency and including the greatest interference level; and predefining a modulation index in order to modulate the switching frequency, wherein the modulation index corresponds to a value of a quotient of approximately 1.42 by an ordinal number of the critical harmonic.