IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 52, NO. 2, MARCH/APRIL 2016 1677 Sensing Power MOSFET Junction Temperature Using Gate Drive Turn-On Current Transient Properties He Niu, Student Member, IEEE, and Robert D. Lorenz, Fellow, IEEE Abstract—Junction temperature sensing for high-bandwidth power MOSFET junction temperature protection is usually achieved on the power converter’s high power side, by directly monitoring the power switches with additional temperature detec- tors. This requires special considerations for high voltage, high current, high temperature, and EMI protection. This paper presents a new method applied on the power converter’s low power side (MOSFET gate drive) so that junction temperature sensing can be integrated into MOSFET gate drive. For the purpose of demonstrating MOSFET junction temperature sens- ing, a push–pull gate drive is applied to a switching current divider circuit. The gate drive turn-on current transient waveform is used for MOSFET junction temperature estimation. A “gate drive-MOSFET” switching dynamic model is implemented indi- cating the mechanisms of MOSFET gate drive output dynamics. Modeling includes gate-drive push–pull output, gate drive output parasitics, power MOSFET intrinsic parameters, PCB parasitics, and load parasitics. LTSpice simulation of this model is studied and compared with experimental results. Index Terms—Gate drive, MOSFETs, sensing, temperature, transient. I. I NTRODUCTION S ENSING power semiconductor junction temperature (T j ) is commonly achieved by adding contact temperature detectors to the power converter. Direct bonded copper (DBC) temperature sensing with thermistors or thermocouples is included in this category. However, since these temperature detectors have slow thermal response and are difficult to inte- grate [1], [2], they are ill-suited for fast junction temperature sensing. With modern semiconductor processing, a small p–n junc- tion can be made on the same piece of silicon as the power MOSFET or IGBT. The temperature dependence of the p–n junction voltage drop can be used for MOSFET junction tem- perature estimation [3]. However, making this additional p–n Manuscript received February 5, 2015; revised August 17, 2015; accepted October 21, 2015. Date of publication November 2, 2015; date of current ver- sion March 17, 2016. Paper 2015-PEDCC-0099.R1, presented at the 2014 IEEE Energy Conversion Congress and Exposition, Pittsburgh, PA, USA, September 14–18, and approved for publication in the IEEE TRANSACTIONS ON I NDUSTRY APPLICATIONS by the Power Electronic Devices and Components Committee of the IEEE Industry Applications Society. This work was sup- ported by the Wisconsin Electric Machines and Power Electronics Consortium (WEMPEC) of the University of Wisconsin–Madison. The authors are with the University of Wisconsin–Madison, Madison, WI 53706 USA (e-mail: hniu@wisc.edu; lorenz@engr.wisc.edu). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIA.2015.2497202 junction sensor can affect the silicon effective area of the power semiconductor, thus limiting the semiconductor power rating. Current commercial versions of this technology demonstrate an 8-ms temperature sensing delay, making it ill-suited for fast junction temperature sensing and control [4]. The giant magneto resistive (GMR) effect enables very small GMR devices to be useful for measuring magnetic fields, thus allowing them to be integrated as current sensors. Since the GMR is made of very thin layers of metal, it can achieve MHz bandwidth current sensing [5]. The resistivity of the metallic layers is dependent upon their “bulk” temperature [6]. Any change in resistance of a shielded element is due to a change in temperature. This has allowed a GMR to be used for both current sensing and interconnect temperature sensing [7]. Indirect junction temperature sensing utilizes the correla- tion between junction temperature and semiconductor electrical properties. Electrical properties such as MOSFET ON-state resistance R DS-on are known to be junction temperature depen- dent. By monitoring R DS-on (using V DS-on /I DS-on ) and referring to its T j dependency, the junction temperature can be estimated online [8], [9]. However, the change of V DS-on and I DS-on in terms of the change of MOSFET junction temperature is small. Therefore, this method requires very accurate voltage and cur- rent measurement. Furthermore, galvanic isolation is required since invasive voltage measurement is necessary in [8] and [9]. The galvanic isolation can make the converter more complex and ill-suited for power integration. It is established in [1] that the behavior of the power MOSFET in a converter configuration during a switching transient can be described as that of an under-damped LCR circuit approximately under step excitation (referred to as “volt- age source- R DS-on -L-C”). Simulation and experimental results indicated that the time constant of the load voltage ringing decay (or dc bus current ringing decay) can be used to esti- mate R DS-on . Note that the ringing usually contains multiple orders of harmonics, and that [1] studied the lower order ringing (low-frequency component). The “voltage source- R DS-on -L-C” ringing function diagram is illustrated in Fig. 1 with parasitic resonance, intermediate variable, and ringing decay extraction. By utilizing the T j - R DS-on dependency provided by MOSFET manufacturers, this ringing decay methodology could be a suitable, noninvasive, but load dependent way to estimate the junction temperature of the MOSFET. The ringing decay methodology was extended in [11] from the “voltage source- R DS-on -L-C” resonant model to the “gate 0093-9994 © 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.