Characteristics and examples of IGBT module surge voltage

L0504-Murata muRata common mode inductor 90Ω 150mA

When an IGBT, such as the U series model 6MBI450U-120, is turned off, a surge voltage can occur. This phenomenon is influenced by the collector current—typically, the higher the current, the greater the surge voltage at turn-off. The image on the left illustrates this behavior, showing how the voltage spikes during the switching process.

The second image highlights the surge voltage that occurs during the reverse recovery of the FWD (Free Wheeling Diode) within the same IGBT module. In this case, the collector current is usually low—often just a fraction of the rated current—but the surge voltage can still be significant. It's important to ensure that all operating conditions remain within the RBSOA (Reverse Blocking Safe Operating Area) or within the VCES limits to avoid damage to the device.

Understanding these voltage characteristics is crucial for designing reliable power electronics systems. Engineers should always consider both the turn-off and reverse recovery behaviors when selecting IGBT modules and setting up protection circuits. Proper thermal management and snubber circuits can also help mitigate the effects of these surges, ensuring stable and safe operation under various load conditions.