A novel modulation topology for power converters utilizing multiple carrier signals

Power converters are known to generate spectral components in the range of interest of electromagnetic compatibility measurements. Common approaches to manipulate some selected components in these frequency ranges are shown here. These approaches add components to the input signal of the modulator to derive a slightly varied spectrum. To achieve a rectangular output signal, those modulators use a triangular or saw tooth carrier signal. A novel family of modulators is shown here, using more than one carrier signal to obtain a completely changed spectrum while maintaining the rectangular shaped waveform at the output. The multiple carriers are fed into multiple comparators and their outputs are intelligently combined by logic gates to get a single signal to drive one power stage of any type of converter. This commutation distinguishes between the four members of the novel family: the first one uses an or- gate to combine the signals; the second one utilizes therefore an and-gate. The third modulator combines the outputs of those two and switches between the or-output and the and- output after each pulse. The last described modulator is commutating one of the described outputs dependent on the state of a master clock. The nonlinear operation of all modulators is described with nonlinear algebra in conjunction with Boolean algebra. The benefits for electromagnetic compatibility of the new schemes are presented, all modulators are examined in terms of steady state operation, dynamic behavior, maximum modulation range and added distortion. Finally the implementation of one of the modulators in a switch-mode power supply is presented. Experimental results are verifying the simulation.