Power Limit for Insulation Capabilities of Modern IGBT/MOSFET Gate Drivers: Page 6 of 6

February 21, 2019 //By Bernhard Strzalkowski, Analog Devices
Power Limit for Insulation Capabilities of Modern IGBT/MOSFET Gate Drivers
This article investigates a gate driver’s isolation withstand performance through the intentional destruction of IGBT/MOSFET power switches.

Conclusion

Destructive tests of power switches do not impact the isolation withstand of the integrated gate driver ADuM4223/ADuM3223. Even if the driver was damaged due to an excess of energy flowing into the output chip, only local and limited molten areas occurred. The energy excess was directed via the P-MOS driver transistor into the blocking capacitors. Thus, the molten areas occurred in the P-MOS region only.

The chip arrangement of ADuM4223/ADuM3223 does not allow diffusion of molten areas into the control chip, which includes the galvanically isolated signal transformer. To limit the energy flowing into the driver output, a Zener diode can be used. The Zener diode in combination with an appropriate gate resistor can protect the gate driver during the power switch damage phase. It is possible to design the gate resistor to manage power dissipation during regular work and to separate the driver from the power switches during their destruction. When high voltage is directly applied into the chip, the gate resistor acts as a fuse. The resistor limits chip damage to small molten areas around the output power switch.

In the worst case, when unlimited energy was applied to the output chip, limited molten area in the vicinity of the driver’s output pin occurred. This test did not impact the isolation withstand. In the worst case on the primary side, when the supply voltage rose significantly above the absolute maximum rating, a limited molten area surrounding the supply voltage pin was observed. There was no sign of weakening of the isolation in any electrical overstress test. A high voltage isolation test, performed afterward, confirmed the withstand performance of the electrical microisolation. The appropriate chip construction, as well as the chip arrangement inside the driver package, avoided proliferation of the destructive energy into the high voltage isolation layer of the microtransformer.

References

1 Baoxing Chen and Bernhard Strzalkowski. “Isolated Gate Driver Using Microtransformers.” ECPE workshop “Electronica Around the Power Switches.” June 29, 2011.

2 Andreas Volke, Michael Hornkamp, and Bernhard Strzalkowski. “IGBT/MOSFET Applications Based on Coreless Transformer Driver IC 2ED020I12-F.” Proceedings of PCIM 2004, Nürnberg, 2004.

3 SLLA198. “The ISO72x Family of High Speed Digital Isolator.” Texas Instruments.

4 Bernhard Strzalkowski. “High Performance IGBT-Driver in Microtransformer Technology Providing Outstanding Insulation Capability.” Proceedings of PCIM2007, Nürnberg, 2007.

5 Bernhard Strzalkowski. “Maximum Power Limit for Withstand Insulation Capability of IGBT/MOSFET Gate Drivers.” Proceedings of PCIM 2014, 2014.

About the Author: Bernhard Strzalkowski studied electrical engineering at the Silesian University of Technology in Gliwice, Poland and Karlsruhe Institute of Technology in Germany, and received his Dipl.-Ing. degree in electrical engineering from Karlsruhe Institute of Technology in 1989. In 2003, he received a Ph.D. in electronics from Silesian University of Technology. From 1989 to 1996 he worked as a research and development engineer with Magnet-Motor in Starnberg developing power electronics for wind power converters and electrical/hybrid cars. From 1997 to 2008 he joined Siemens and Infineon in Munich, where his research and design work comprised integrated circuits for industrial and automotive applications. In February 2009, he joined Analog Devices in Munich, working on power management, digital power, and iCoupler applications. He supports automotive and communication infrastructure customers in Europe and has been granted numerous patents relating to the field of power electronics. He is a member of the standards committees ICE and VDE, as well as the PCIM advisory board. He can be reached at bernhard.strzalkowski@analog.com.

 

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