Abstract
This paper deals the design of EMI filter associated with buck converter using fast semiconductors silicon carbide SiC (diode and transistor JFET). To comply with EMC standards, a filter design method based on an equivalent electrical circuit is proposed. The aim is to identify the different values of the EMI filter elements but also to obtain the limits values of the parasitic elements of the passive components which have a major influence on the attenuation of the filters. The purpose is to study the influence of the modification of the common mode propagation paths before and after the installation of the filter. A solution is also proposed to reduce the conducted disturbances that occur at high frequency caused by the fast SiC components.The comparison of the simulation results with the measurements data carried out on a DC-DC converter without and with the EMI filter, shows the effectiveness of the proposed design approach.
Highlights
The utilization of the fast power switches based on the silicon carbide (SiC) or GaN semi-conductor materials will result in higher operating frequencies of static converters, this has as consequence the increases of the conducted emissions toward the power network [1,2,3,4,5,6,7]
A high frequency model of the EMI filter which takes into account the common mode paths impedance is proposed
The first aspect is related to the development of a methodology allowing to determine, in the first approach, the different values of the CM and DM filters, and the limit values of the parasitic elements of passive components that have negative effect on the filter efficiency in high frequency
Summary
The utilization of the fast power switches based on the SiC or GaN semi-conductor materials will result in higher operating frequencies of static converters, this has as consequence the increases of the conducted emissions toward the power network [1,2,3,4,5,6,7]. To calculate the elements of the L-C common mode filter, the value of the capacitor is fixed to CY = 4.7nF This value provides a good compromise; it is large enough to minimize the value of the CM inductor and small enough to limit ground currents to prevent accidental tripping of mains differential circuit breaker. From calculated values of L1, L2 and CY, and limits given by the EMC standard (figure 6a), the proposed model of the CM filter is given in figure 7 It will be used for the simulation of the filter to evaluate the attenuation necessary that taking into account the limits values of the parasitic elements of the passive components (Rp1, Rp2, Cf1, Cf2, Ry/2, Ly/2, Lf, Rs) and CM impedance path Zp named "the second CM impedance path". The design of the CM and DM filters is presented
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