Thermal Impedance Meter for Power mosfet and IGBT Transistors

Modulation method and the device for thermal impedance measuring of power mosfets and IGBT transistors, and measurement results are described. The measurements were performed by generic modulation method that implies heating a device under test by power varying harmonically. A pulse sequence of heating current, with the pulse length varying harmonically, is passed through the device under test. The p-n junction temperature is determined by measuring a temperature-sensitive parameter, which is forward voltage drop on the p-n junction between heating pulses at low measuring current. Analysis of the dependence of thermal impedance on modulation frequency allows us to determine thermal impedance components corresponding to the structural elements of the object under test. The method allows us to significantly reduce the effect of heating the device's case during the measurement, and thereby increase the accuracy of thermal resistance measurement.