Use of a co-axial CT and planar bus to improve IGBT device characterization

Modern high power insulated gate bipolar transistor (IGBT) modules typically have a package inductance of less than 50 nH and switching times as low as 30 ns. Proper characterization of high power fast switching devices requires total test fixture stray inductance be minimized to preferably less than module package inductance. Design and fabrication of such a test fixture is detailed. Specially designed strategic components such as: (1) a co-axial current transformer (CCT) to minimize current monitoring insertion impedance; (2) a planar bus to minimize total circuit inductance; and (3) special bus capacitors to minimize component inductance are utilized. Fixture grounding and instrumentation are also shown to affect IGBT characterization results. Test fixture design, grounding and instrumentation techniques presented are proposed as basis for a standard characterization test procedure of high power IGBTs under hard and soft switching. A power structure design methodology that integrates IGBT characterization results is proposed