Conductive noise analysis of inverter circuits for vehicle equipments using an equivalent circuit

Conductive noise from vehicle equipments which contain inverter circuits has been increased by the demand of higher switching operation of power devices in order to improve the power efficiency. On the other hand, since the vehicle equipments are required to minimize the volume, the noise filters should be built-in the housing of inverter circuits. In this case, it is necessary that the conductive noise is predicted at design stage in order to optimize the size and performance of the noise filters. In this paper, we propose precise equivalent circuit to predict the conductive noise for the vehicle equipment. The equivalent circuit for the vehicle equipment consists of noise filters, switching devices, and motors with parasitic inductance and stray capacitance in each part so as to obtain higher accuracy. Futuremore, the accuracy of the conductive noise calculation using the proposed equivalent circuit is verified quantitatively by an experiment. The difference between the calculated and measured results is within 10dB in the frequency range between 150kHz to 6MHz.