Common and differential mode noise separate technology with low cost and high performance

For conduction emission noise, the separation of the common and differential mode noise is important for determining parameters of proper filter. This paper proposes a novel noise separation technology with low cost and high performance which combines hardware with software. The common mode (CM) noise is separated by differential mode rejection network (DMRN) which is composed of three resistors. The differential mode (DM) noise is shown by software method based on the definition of CM and DM. This paper estimates the error brought by this separation technology. Conducted emission produced by a 600W DC motor system was separated by the novel separation technology. The parameters of filter was designed according to the separation result. Conducted inteference produced by this motor was measured after this designed filter was connected into the motor system. Experiment results indicate that it is complied with electromagnetic compatible (EMC) standard in the whole conducted interference frequency band and prove that this separation technology is very valid.