Junction Temperature Online Extraction Method for Power MOSFET by Current Fall Time

Temperature-sensitive electrical parameter (TSEP) approaches are widely used in junction temperature (
${T}_{j}$
) prediction of insulated gate bipolar transistor (IGBT). Due to different physical characteristics, TSEPs in IGBT may not suitable for power MOSFET. In this article, a novel junction temperature extraction for power MOSFET based on current fall time (
${t}_{fi}$
) during turn-off process is proposed. The voltage rise time (
${t}_{rv}$
) and
${t}_{fi}$
during turn-off process as power MOSFET’s TSEPs are evaluated, and
${t}_{rv}$
is often used for junction temperature prediction of IGBT. In addition, a method of using parasitic inductance induced voltage in the circuit to extract
${t}_{fi}$
is proposed, and the feasibility of this method has been analyzed. Then, the boost experimental platform is established, and three different types of power MOSFETs were tested. It is established that the model based on
${t}_{fi}$
is a viable model with good linearity and sensitivity, and through induced voltage on parasitic inductance,
${t}_{fi}$
can be well-reflected. Finally, online extraction of power MOSFET junction temperature in the boost circuit is implemented in this article.