Isolated DC-DC converter with high CMTI for gate driver applications
DC-DC converters in integral housing are being used more and more in power electronics for the isolation of supply voltages for SiC MOSFET gate drivers. For this application, the entire switched DC link voltage is applied to the high-side converter. The very high and steep voltage peaks (measured in nV/s) that arise in the high-frequency SiC circuit affect the isolation and impair the service life of the product.
As a result, the DC-DC converters of Murata’s MGJ2D series have been specially designed and tested for such SiC FET applications, e.g. in chargers for e-mobility. They have a very high pulse strength (CMTI) of 80 V/ns at 1000 V. This can counteract a service life reduction resulting from the recurring influences on the isolation. In addition to the excellent isolation, the very low capacitive coupling of just around 3 pF also ensures good DC link properties. The extent of the voltage variation (V/ns) and the coupling capacitance are decisive for the induced current value, which can affect operation of the gate driver.
Procedures such as the hipot test and withstand voltage test are used for the DC-DC converters of the MGJ2D series to guarantee isolation resistance throughout the entire service life. The converters are fully tested and reach an approved value of 5.2 kV over 1 minute. Thanks to sufficiently dimensioned creepage distances and safety distances, they fully meet the requirements of the international standard IEC 62477. The compact design also contributes to interference resistance. In addition to the standard SIP housing, the new SMD version enables a reduction in size by a factor of 5 or more compared to discrete solutions.
The DC-DC converters from Murata can be found, along with other state-of-the-art components for the development of on-board and off-board charger technology, in the wide range offered by Angst+Pfister Sensors and Power (formerly Pewatron). This also includes the new BeFAST evaluation board – a versatile development tool for determining the relevant circuit properties in interaction with all essential components such as SiC FET, DC-DC converters, isolators, thermistors, etc.
