SiC and IGBT Dynamic Double-Pulse Testing: Procedure and Pitfalls

Dual Pulse Test and Its Precautions

For power electronics engineers, power components are our design focus, and IGBTs are widely used in power modules due to their excellent properties. The efficiency, protection functions, EMC performance of power modules are closely related to the application design of IGBTs, and different IGBT technologies have also produced IGBT products with varying performance

To optimize and verify component performance and verify the performance of different IGBTs, we have introduced a dual-pulse testing method, which allows us to achieve the following specific functions:

Learn more about various IGBT parameters, such as Eon, Eoff, Tdon, Tdoff, Tr, Tf, chip switching characteristics, etc. The purpose of this test is to verify the parameter values in the datasheet and to evaluate the performance of different modules

driver circuit design evaluation. The selection of Rg and Cg and gate cable affect the gate waveform, whether it oscillates, dv/dt, di/dt, and other characteristics. In addition, Miller clamping, gate clamping, active clamping, and soft shutdown design can all be evaluated in this test

Thermal design parameter check: Typically, thermal design is based on the Eon and Eoff values in the datasheet. These given values are given under specific test conditions. Due to requirements for module performance optimization and balance, the actual Eon and Eoff values often differ from the theoretical values. For example, due to EMC requirements, we want smaller dv/dt and di/dt, which leads to larger Eon and Eoff. Through this test, we obtain the true Eon and Eoff values, making the simulation more realistic

System stray inductance: The module's operating voltage must be below its rated voltage under any circumstances. At low temperatures, derating must also be considered. The IGBT voltage spike also depends on system stray inductance, di/dt when turned off, bus voltage, etc. This test allows evaluation of the maximum allowable stray inductance of the system and comparison of stray inductance across different busbars

Overcurrent and short-circuit protection circuit verification: In this experiment, it is necessary to check the peak voltage when turned off, the gate waveform during turn-off, short-circuit current, protection circuit operation time, and whether there is any oscillation

Busbar and AC busbar design during parallel operation: When modules need to be connected in parallel, the junction temperature of the module is related to the current sharing degree of the module, which determines whether the module can operate reliably, its lifespan, and the overall system lifespan depends on the modules under the harshest operating conditions. Moreover, multi-module parallel operation also presents challenges for overcurrent and short-circuit protection designs