Accurate Online Junction Temperature Estimation of IGBT Using Inflection Point Based Updated I-V Characteristics

The junction temperature (T-j) estimation of the insulated gate bipolar transistor (IGBT) is important for reliable operation of the power converters in various applications. For T-j estimation, ON-state collector-emitter voltage (v(ce)) at higher collector currents (i(c)) is widely used temperature sensitive electrical parameter (TSEP). For real-time T(j )estimation, this TSEP is calibrated using the I-V characteristics of the new IGBT. Due to bond-wire degradation, the original I-V characteristics of IGBT changes resulting in inaccurate T-j estimation. In this article, a technique is proposed to update the I-V characteristics of the degraded IGBT, without affecting the normal operation of the power converter. It is achieved by estimating the increment in bond-wire resistance (Delta R-con) by using real-time samples of v(ce )and inductor current. The mathematical analysis is also presented to find an error in estimated Delta R-con. The major contributions of this article are as follows: a) it enables the accurate T-j estimation of the IGBT throughout its lifetime; and b) it also provides the parameter Delta R-con, which could be utilized in condition monitoring of the IGBT. Further no additional circuitry is required. The proposed technique is validated on experimental setup, which is developed in the laboratory. The error in T(j )estimation is observed within 1 degrees C the degraded IGBT, which shows the effectiveness of the proposed scheme.