Power converter control for reducing EMI noise by temporally changing the PWM carrier frequency

摘要

A controller and method for reducing EMI noise by changing a frequency of a control (or carrier) signal in accordance with a waveform that periodically changes within a first frequency range from a frequency fc1 to a frequency fc2, where the frequency fc1 is smaller than the frequency fc2, and a second frequency range from a frequency fc3 to a frequency fc4, where the frequency fc3 is smaller than the frequency fc4. The frequencies fc1 and fc4 satisfy the inequalities (n-1)·fc4 ‰¤ n·fc2 and n·fc3 ‰¤ (n+1)·fc1 and/or satisfy an approximate expression n·fc4‰ˆ (n+1)·fc1 where n is an integer. The frequencies fc2 and fc3 satisfy the inequalities n·fc2 ‰¤ fs-”fs and fs+”fs ‰¤ n·fc3 where fs±”fs represents a predetermined frequency band.