IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 34, NO. 4, APRIL 2019 3615 Indirect IGBT Over-Current Detection Technique Via Gate Voltage Monitoring and Analysis Xinchang Li , Dawei Xu, Hongyue Zhu, Xinhong Cheng, Member, IEEE, Yuehui Yu, and Wai Tung Ng , Senior Member, IEEE Abstract—This paper presents a new insulated gate bipolar tran- sistor (IGBT) over-current detection method based on the analy- sis of the gate voltage waveform. The IGBT’s gate voltage turn- ON transient pattern is analyzed for the detection of IGBT hard switching fault (HSF). The ON-state gate voltage is monitored to detect IGBT fault under load (FUL). The IGBT’s turn-OFF Miller plateau voltage is extracted and measured to sense the IGBT col- lector current in case of an over-load condition. Compared to the commonly used IGBT short-circuit detection methods or collec- tor current sensing methods, this method can provide indirect fast detection of IGBT short circuit and accurate measurement of over- load within one switching period. The feasibility and effectiveness of the proposed approach are validated both by simulation and ex- perimental results. Measurement results show that HSF and FUL can be detected within 0.6 and 0.5 μs, respectively. By comparing the extracted plateau voltage (V PL ) with a preset reference volt- age (V OCx ), the IGBT over-load can be detected with a maximum deviation of ±1.2 A when I C ranges from 3 to 110 A. Index Terms—Insulated gate bipolar transistor (IGBT), Miller plateau, over-current detection. I. INTRODUCTION I NSULATED gate bipolar transistor (IGBT) over current can be classified as short-circuit over current or over-load over current [1]. Generally, short-circuit over current is a result of IGBT hard switching fault (HSF) or fault under load (FUL) [2]. Most IGBTs can withstand short circuit for only several microseconds because the fault current can be very large. The IGBT experiencing high electrical and thermal stress under large current would lead to thermal breakdown. Therefore, fast pro- tection methods are needed for IGBT short-circuit over-current conditions. In contrast, IGBT over-load current comes from in- rush current, filter in-rush, and a change in load. In this case, Manuscript received February 6, 2018; revised May 20, 2018; accepted July 2, 2018. Date of publication July 16, 2018; date of current version February 20, 2019. This work was supported by the National Key Research and Devel- opment Program of China under Grant 2016YFB0010700. Recommended for publication by Associate Editor S. S. Ang. (Corresponding author: Dawei Xu.) X. Li, D. Xu, H. Zhu, X. Cheng, and Y. Yu are with the State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China, and also with the University of the Chinese Academy of Sciences, Beijing 100049, China (e-mail:, lixc@mail.sim.ac.cn; dwxu@mail.sim.ac.cn; zhy@mail.sim.ac.cn; xh_cheng@mail.sim.ac.cn; yhyu@mail.sim.ac.cn). W. T. Ng is with The Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON M5S 3G4, Canada (e-mail:, ngwt@vrg.utoronto.ca). 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/TPEL.2018.2856777 IGBTs can have much longer endurance time than the previous condition because the fault current is much smaller. However, current sensors are also needed to monitor the over-load current for loop control. In conventional IGBT over-current detection methods, a de- saturation detection method is widely used for short-circuit fast protection. This method monitors the collector–emitter voltage drop to judge whether the IGBT is suffering from short circuit fault. However, high-voltage isolation elements such as diodes are needed between the collector node and the low side. In addition, a blanking time is mandatory [3]. Collector current transient di/dt can also be used for short-circuit detection. This method monitors the voltage drop on the emitter parasitic induc- tor due to di/dt. It can realize fast fault detection, but usually the value of the parasitic inductance is not provided [4], [5]. IGBT current measurement, which is used for over-load detection, can be accomplished using a shunt resistor, a current transformer, or by voltage measurement over the power module’s parasitic inductance [6]–[10]. A low-ohmic resistor is usually placed be- tween the emitter of the IGBT and ground to sense the output current. However, the power loss associated with this resistor can be quite high, leading to a significant increase in system cost and size. The use of current-sensing transformers is com- mon in high power systems. The idea is to sense a fraction of the high inductor current by using the mutual inductance in the transformer. The major drawbacks are increased cost and size, and integration is not possible. In this paper, an indirect IGBT over-current detecting strategy, which can detect both short-circuit over current and over-load simultaneously via the IGBT gate node, is presented. The proposed method detects IGBT short-circuit conditions such as HSF and FUL through a gate voltage pattern analyzer. The IGBT over-load condition can be accurately predicted by measuring the turn-OFF Miller plateau voltage. There are three main advantages of the proposed technique. First, there is no need to measure current directly in the high-voltage environment associated with the collector side. Second, costly discrete com- ponents such as shunt resistors and transformers are not needed. Finally, the technique not only can provide fast short-circuit detection, but also detect over load where the fault current is not excessively large, both detections are implemented within one switching period. This paper is organized as follows. Section II describes the physical background of IGBT switching transients and the relationship between IGBT Miller plateau and the collector current I C . Section III describes the circuit design and 0885-8993 © 2018 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.