Vinoth Sundaramoorthy

A study on IGBT junction temperature (Tj) online estimation using gate-emitter voltage (Vge) at turn-off

Abstract A novel method is presented for online estimation of the junction temperature (Tj) of semiconductor chips in IGBT modules, based on evaluating the gate-emitter voltage (Vge) during the IGBT switch off process. It is shown that the Miller plateau width (in the Vge waveform) depend linearly on the junction temperature of the IGBT chips. Hence, a method can be proposed for estimating the junction temperature even during converter operation – without the need of additional thermal sensors or complex Rth network models. A measurement circuit was implemented at gate level to measure the involved time duration and its functionality was demonstrated for different types of IGBT modules. A model has been proposed to extract Tj from Vge measurements. Finally, an IGBT module with semiconductor chips at two different temperatures has been measured using Vge method and this method was found to provide the average junction temperature of all the semiconductor chips.

On the influence of active area design on the performance of SiC JBS diodes

This paper presents an investigation regarding the influence of the active area design on the static and dynamic performance of SiC JBS diodes. The analysis has been performed on fabricated JBS diodes, rated for 1.7kV applications. For the active area layout, both stripe and hexagonal cell patterns have been used for the implanted p+ regions.

A novel method to protect IGBT module from explosion during short-circuit in traction converters

A novel method using gate overdrive is suggested to avoid explosion of IGBT modules in converters. With this method, the gate drive impedance is set to low (~0 Ω), such that the driving capability of the gate drive is not limited by the short-circuit present between the gate and auxiliary emitter terminals of a damaged IGBT. Using the implemented gate driving concept, the fault current can be redirected through good chips in the module and the current concentration in the faulty chip of the IGBT module could be reduced to avoid explosion.

Formation of Ohmic Contacts to n-Type 4H-SiC at Low Annealing Temperatures

The formation of Ohmic contacts to n-type 4H-SiC layers at low annealing temperature using dopant segregation technique is reported. n-SiC epilayer was implanted with phosphorous and subsequently activated at 1700 °C. Ni metal contacts fabricated on phosphorous implanted and annealed epilayers produced Ohmic contacts with a specific contact resistivity (ρc) of ~7.2x10-5 Ω.cm2 at an annealing temperature of 550 °C. ρc decreased with further annealing temperature reaching a value of ~2.1x10-5 Ω.cm2 at 1000 °C. XRD analysis showed that nickel silicide phase was formed at both 550 °C and 1000 °C.

The Effects of Illumination on Point Defects Detected in High Purity Semi-Insulating 4H-SiC

The electrical characterization of high-purity semi-insulating 4H-SiC is carried out by means of current deep level transient spectroscopy (I-DLTS). Measurements are performed by employing either an electrical or optical pulse (below/above bandgap). The study performed on as-grown material, either annealed or oxidized, reveals the presence of six levels with ionization energies in the 0.4-1.3 eV range.

A study to improve IGBT reliability in power electronics applications

Lifetime prediction of IGBT modules from their junction temperature is an important aspect to improve the reliability of power electronic systems. Here, methods to estimate the IGBT junction temperature from its electrical characteristics are discussed. A solution is also proposed to avoid explosion of IGBTs used in traction converters.

Design of quasi-vertical GaN high power Schottky diodes based on field plate termination

In this paper, the numerical design of a optimized quasi-vertical gallium nitride power Schottky diode for high power electronic applications is illustrated. Bevel oxide field plate was employed as a junction termination technique to enhance the breakdown voltage in reverse bias. It was found that a maximum breakdown voltage of 1995 V was obtained for a bevel width of 18 um and oxide thickness of 1.5 um. This diode with on-state resistance of 14mΩcm2 has a high power figure of merit of 274 MW/cm2.