Capacitor technologies and ceramic materials for DC- link capacitors in electric or hybrid car inverters are reviewed and a comparison with film capacitors is presented, with emphasis for inverters that use SiC switches. The ceramic capacitors help in balancing the semiconductor switching speed, the frequency of switching, the current density, and they lower the ripple and the voltage overshoot. It is shown, how the basic properties in either ferroelectric, antiferroelectric, and paraelectric material relate to these requirements. A comparison is done for BaTiO3 – based MLCC (ferroelectric, FE), and (Pb,La)ZrTiO3 – based MLCC (antiferroelectric, AFE) and film capacitors (paraelectric, PE) . The limits with respect to high current, voltages, temperatures, and frequencies are discussed in conjunction with circuit design and the driving methods of Si and SiC inverters. Exemples are given for choosing the capacitance value in specific applications for the combinations of Si or SiC with all these types of capacitors. In system designs of inverters, the relatively higher cost of SiC has to be balanced with the gain from decreasing switching losses at higher frequencies. Depending on the application (charging, main drive inverter, auxiliary DC/DC), different cost considerations result. To achieve lowest loss in main drive inverters, frequencies > 100kHz, the so called « soft switching » with active gate drivers of SiC, and MLCCs as DC-Link capacitors are recommended, either FE or AFE. Presently, AFE MLCC have higher energy density and need less space but are more costly than FE MLCC.

For increasing the energy density (realistic target is a factor 7 – 8), and thus a cost down (with the same factor) in the AFE MLCC it is proposed to use (Pb,Ba)(Zr,Ti)O3 perovskites as new ceramic dielectric, which shows increased dielectric constants and lower dielectric losses, and is capable for copper inner electrodes for the multilayer construction and capable to be fired in reducing atmosphere. The result is then that an inverter of ~200kW (typical main drive inverter in electric cars) will need only 3~5 MLCC with case size 2220 (EIA- standard), and an efficiency of > 99,4%. Thus, the following split strategy is recommended for optimum benefit for the climate protection : 1st part is Ba- doping for PLZT, and 2nd is using these antiferroelectric MLCCs in soft switching SiC with active gate driver inverter applications. Calculations show, that the cost of Ba- doped AFE- MLCC that constitute the DC-link is lower than for FE- MLCC, and also much lower than in SiC plus film capacitor solution, because of the inverse scaling of cost with the energy density and the high current capability of the AFE-MLCC.

Key- words : Antiferroelectrics, PLZT, MLCC, soft switching, SiC inverter, electromobility.