Development of Si Device Based Power Converters for High Temperature Operation in HEV Applications

In this dissertation, the feasibility of operating Si devices at 200 ˚C [degree Celsius] is investigated and the guidelines on the development of a high temperature Si converter for operating with 105 ˚C high temperature liquid coolant in hybrid electrical vehicle (HEV) applications are provided. First, the characterization of a Si IGBT operating at 200 ˚C junction temperatures is presented. It is shown that the commercial 175 ˚C Si IGBT under test can be successfully switched at an elevated junction temperature of 200 ˚C with increased but acceptable losses. Second, a comprehensive evaluation of Si IGBT ruggedness at high temperature operation is provided through experiments. The important criteria considering latch-up immunity, short circuit capability, and avalanche capability are given to ensure the safe and reliable operation of Si IGBTs at 200 ˚C. Third, the feasibility of operating Si devices based converters continuously at the junction temperature of 200 ˚C is demonstrated. A Si IGBT phase-leg module is developed for 200 ˚C operation utilizing high temperature packaging technologies and appropriate thermal management. Fourth, a method is proposed to measure the junction temperatures of IGBTs during the converter operation using IGBT short circuit current. The calibration experiments show that the short circuit current has good sensitivity, linearity and selectivity, making the method suitable for use as temperature sensitive electrical parameter (TSEP). By connecting a temperature measurement unit to the converter and giving a short circuit pulse during the converter operation, the IGBT junction temperature can be measured. Fifth, a 30 kW Si IGBT based three-phase converter has been developed for operating at the junction temperature of 200 ˚C with the high temperature coolant in HEV applications. The experimental results demonstrate that the three-phase converter can operate at junction temperature of 200 ˚C with the 105 ˚C high temperature coolant, thus eliminating the need for the additional 65 ˚C coolant in HEV. Additionally, the emerging 600 V GaN HEMT is investigated as a potential replacement of Si devices for high efficiency and high temperature in future HEV applications

Reliability-Oriented Strategies for Multichip Module Based Mission Critical Industry Applications

The availability is defined as the portion of time the system remains operational to serve its purpose. In mission critical applications (MCA), the availability of power converters are determinant to ensure continue productivity and avoid financial losses. Multichip Modules (MCM) are widely adopted in such applications due to the high power density and reduced price; however, the high number of dies inside a compact package results in critical thermal deviations among them. Moreover, uneven power flow, inhomogeneous cooling and accumulated degradation, potentially result in thermal deviation among modules, thereby increasing the temperature differences and resulting in extra temperature in specific subset of devices. High temperatures influences multiple failure mechanisms in power modules, especially in highly dynamic load profiles. Therefore, the higher failure probability of the hottest dies drastically reduces the reliability of mission critical power converters. Therefore, this work investigate reliability-oriented solutions for the design and thermal management of MCM-based power converters applied in mission critical applications. The first contribution, is the integration of a die-level thermal and probabilistic analysis on the design for reliability (DFR) procedure, whereby the temperature and failure probability of each die are taken into account during the reliability modeling. It is demonstrated that the dielevel analysis can obtain more realistic system-level reliability of MCM-based power converters. Thereafter, three novel die-level thermal balancing strategies, based on a modified MCM - with more gate-emitter connections - are proposed and investigated. It is proven that the temperatures inside the MCM can be overcame, and the maximum temperate reduced in up to 8 %

Two decades of condition monitoring methods for power devices

Condition monitoring (CM) of power semiconductor devices enhances converter reliability and customer service. Many studies have investigated the semiconductor devices failure modes, the sensor technologies, and the signal processing techniques to optimize the CM. Furthermore, the improvement of power devices’ CM thanks to the use of the Internet of Things and artificial intelligence technologies is rising in smart grids, transportation electrification, and so on. These technologies will be widespread in the future, where more and more smart techniques and smart sensors will enable a better estimation of the state of the health (SOH) of the devices. Considering the increasing use of power converters, CM is essential as the analysis of the data obtained from multiple sensors enables the prediction of the SOH, which, in turn, enables to properly schedule the maintenance, i.e., accounting for the trade-off between the maintenance cost and the cost and issues due to the device failure. From this perspective, this review paper summarizes past developments and recent advances of the various methods with the aim of describing the current state-of-the-art in CM research

In-situ Health Monitoring Applied to High-Voltage IGBT Power Modules

PhD ThesisThis thesis addresses an important issue of identifying insulated gate bi-polar transistor (IGBT) chip failures in multichip IGBT power modules. IGBT power modules are the dominant semiconductor devices of choice in high-voltage (HV) high-power converter applications which include domestic, commercial, automotive, railway, marine, aerospace and industrial applications. Commonly available HV IGBT power modules in the market are rated at 3.3 kV, 4.5 kV and 6.5 kV. These HV IGBT modules comprise several IGBT chips connected in parallel to achieve high-current capability; hence they are also known as multichip IGBT power modules. IGBT power modules are not flawless. The increased complexity of IGBT power module construction and inhomogeneous semiconductor chips make HV power modules less reliable. IGBT chips and electrical and mechanical interface material within the modules wear out and fail due to thermal cycling, operating environment or mishandling. IGBT failures while in application have repercussions on safety and failure costs. Thus the reliability of IGBTs while in their application is crucial especially in HV applications which comprise critical and large loads. To improve the reliability, an in-situ (online) health monitoring interface for HV IGBT power modules is proposed in this thesis. Two distinct advantages of in-situ IGBT health monitoring are that it allows IGBT module replacement prior to complete failure thus reducing safety and reliability risks. The second advantage is that the interval time for IGBT maintenance work can be tailored towards the real degradation rather an obligatory fixed time interval thus reducing maintenance costs. In large power modules, it is common to have IGBT chips as well as anti-parallel diode chips within the power module. This research focusses only on the health monitoring of the IGBT chips and not the diode chips. The main reason is that IGBT chips experience higher thermal stresses compared to diodes hence IGBT chips are more susceptible to failures compared to diode chips. In practice, IGBT chip failures are accompanied by a change in junction temperature. Thus this thesis proposes the use of temperature- sensitive electrical parameters (TSEPs) for in-situ health monitoring of IGBT power modules. Following a comparison of twelve traditional online TSEPs from literature and five new TSEPs proposed in this thesis, this thesis employs a novel TSEP, gate-emitter prethreshold voltage (VGE(pre-th)) as a health-sensitive parameter (HSP) for chip failure detection in multichip HV IGBT power modules. A VGE(pre-th) online chip loss monitoring circuit has been successfully implemented on a commercially available IGBT gate driver. VGE(pre-th) is measured at a fixed pre-determined instant of the gateemitter voltage (VGE) between the VGE zero-crossing (VGE(0)) and threshold voltage (VGE(th)) during IGBT turn-on. VGE(pre-th) requires low hardware with only a voltage sensor and a counter. Since it is based on the low-voltage (LV) gate side rather than the HV collector side of IGBT, VGE(pre-th) does not require HV isolation or HV insulation. Simulation and experimentation of 16-chip 3.3kV 800A DIM800NSM33-F IGBT power modules from Dynex Semiconductor Limited (Ltd) have shown that VGE(pre-th) has a good accuracy and repeatability; a linear sensitivity of 500 mV/chip loss with IGBT chip failures; a linear virtual junction temperature (Tvj) sensitivity of -2.2 mV/°C and tracks the highest chip temperature. It has thus been concluded that VGE(pre-th) can be used for both Tvj and IGBT chip failure monitoring in HV IGBT power modules. VGE(pre-th) can be tested during normal IGBT turn-on operation or during the off-state of the IGBT. In both cases the same information about temperature and loss of chip number can be detected which makes VGE(pre-th) more versatile than any other TSEP or HSP.Engineering and Physical Sciences Research Council (EPSRC), Newcastle University

Mjerenje radne temperature IGBT-a u stvarnom vremenu

Temperature management and control are among the most critical functions in power electronic devices. Knowledge of power semiconductor’s operating temperature is important for circuit design, as well as for converter control. Virtual junction temperature measurement or estimation is not an easy task, therefore designing the appropriate circuitry for virtual junction temperature in the real operating conditions not affecting regular circuit operation is a demanding task for engineers. The proposed method enables virtual junction temperature estimation based on the real-time measurement of semiconductor’s quasi-threshold voltage using dedicated modified gate driver circuit.Upravljanje temperaturom je jedna od najkritičnijih funkcija kod učinskih poluvodičkih komponenata. Poznavanje radne temperature učinske poluvodičke sklopke vrlo je važno pri projektiranju sklopa, kao i za upravljanje učinskim pretvaračem. Mjerenje ili estimacija nadomjesne temperature silicija nije lagan zadatak, stoga je projektiranje odgovarajućeg sklopovlja za određivanje nadomjesne temperature silicija u stvarnim radnim uvjetima, koje ne utječe na normalan rad sklopa, vrlo zahtjevan inženjerski zadatak. Predložena metoda omogućava određivanje nadomjesne temperature silicija utemeljeno na mjerenju kvazi-napona praga u stvarnom vremenu pomoću posebno prilagođenog pobudnog stupnja IGBT-a