The regular switching action of a pulse-width-modulated (PWM) circuit generates conducted and radiated electromagnetic interference (EMI) and may also generate acoustical disturbances. Programmed pulsewidth modulation techniques have been applied using various methods to control harmonics inherent in switched power circuits. A method for generating an optimal programmed switching waveform for a DC-DC converter is presented. This switching waveform is optimized to reduce the amplitude of harmonic peaks in the EMI generated by the converter. Experimental results, a brief discussion of sensitivity, and a practical implementation of a circuit to generate the PWM waveform are given.
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