New Industry Products

EPCOS CeraLink Capacitors for Faster Switching in Inverters

November 06, 2012 by Jeff Shepard

The new EPCOS CeraLink™ offers many benefits for stabilizing and filtering the DC link circuits of power inverters - particularly in comparison with conventional capacitor technologies. Developers of topologies with new fast-switching IGBT modules will profit from this innovation.

The power semiconductor switches used in power supplies and inverters are determined by two technologies, namely MOSFETs and IGBTs. MOSFETs can be operated at relatively high switching frequencies significantly above 30 kHz, but unlike IGBTs, they have a very large chip surface area. A new generation of IGBT modules from Infineon Technologies operates at frequencies of up to 100 kHz. Line-based and turn-off losses are of about the same magnitude in both systems. Fast IGBTs, whose manufacturing complexity is significantly lower and chip areas are often smaller than superjunction MOSFETs, are the basis of an IGBT3 technology with high switching frequencies and an excellent price-performance ratio.

Fast-switching systems require circuit designs with minimized ESR and ESL values. Accordingly, the passive components - inductors, but especially capacitors - must also keep pace with the high switching frequencies. These in turn permit more compact and lightweight passive components to be used, producing lower losses and increasing efficiency.

Capacitors are at the focus of these developments. They must combine high switching frequencies with low ESL and ESR values as well as an extremely compact design. Conventional capacitor technologies are only partially able to meet these requirements. The EPCOS CeraLink represents a completely new approach: This advanced component is a ceramic multilayer ripple-current suppressor, also known as a link circuit or DC link capacitor; moreover, it functions as a snubber.

The EPCOS CeraLink was developed in the company's Competence Center for Ceramic Components in Deutschlandsberg, Austria. The know-how that formed the basis for this advanced component was gained, among others, over many years in the volume manufacture of piezo actuators. The EPCOS CeraLink offers the advantages of ceramic capacitors without their unfavorable characteristics. The patented multilayer component that is based on antiferroelectric ceramic material with special copper internal electrodes allows both standard IGBTs and the new high-speed types with significantly higher switching frequencies to be used even more economically. This naturally also applies to circuits with corresponding superjunction MOSFETs.

The innovative CeraLink combines high capacitance per volume with lowest ESL and ESR values, which thus enables significant improvements in efficiency, reliability and space requirement for future IGBT and MOSFET inverter designs. Moreover, CeraLink is also available in a low-profile SMD design, making it suitable as a snubber solution for integration in power modules. The EPCOS CeraLink components were adapted and continuously optimized for the first designs of special IGBT modules in close cooperation with Infineon Technologies, the market leader in IGBTs. This allowed the best results to be achieved in terms of performance and energy efficiency. For both the EASY automotive series from Infineon Technologies and the corresponding types in industrial applications, all the relevant capacitor parameters and properties were optimized towards more economy and efficiency.