In situ diagnostics and prognostics of wire bonding faults in IGBT modules for electric vehicle drives

This paper presents a diagnostic and prognostic condition monitoring method for insulated-gate bipolar transistor (IGBT) power modules for use primarily in electric vehicle applications. The wire-bond-related failure, one of the most commonly observed packaging failures, is investigated by analytical and experimental methods using the on-state voltage drop as a failure indicator. A sophisticated test bench is developed to generate and apply the required current/power pulses to the device under test. The proposed method is capable of detecting small changes in the failure indicators of the IGBTs and freewheeling diodes and its effectiveness is validated experimentally. The novelty of the work lies in the accurate online testing capacity for diagnostics and prognostics of the power module with a focus on the wire bonding faults, by injecting external currents into the power unit during the idle time. Test results show that the IGBT may sustain a loss of half the bond wires before the impending fault becomes catastrophic. The measurement circuitry can be embedded in the IGBT drive circuits and the measurements can be performed in situ when the electric vehicle stops in stop-and-go, red light traffic conditions, or during routine servicing.

Flexible high voltage pulsed power supply for plasma applications

Demands for delivering high instantaneous power in a compressed form (pulse shape) have widely increased during recent decades. The flexible shapes with variable pulse specifications offered by pulsed power have made it a practical and effective supply method for an extensive range of applications. In particular, the release of basic subatomic particles (i.e. electron, proton and neutron) in an atom (ionization process) and the synthesizing of molecules to form ions or other molecules are among those reactions that necessitate large amount of instantaneous power. In addition to the decomposition process, there have recently been requests for pulsed power in other areas such as in the combination of molecules (i.e. fusion, material joining), gessoes radiations (i.e. electron beams, laser, and radar), explosions (i.e. concrete recycling), wastewater, exhausted gas, and material surface treatments. These pulses are widely employed in the silent discharge process in all types of materials (including gas, fluid and solid); in some cases, to form the plasma and consequently accelerate the associated process. Due to this fast growing demand for pulsed power in industrial and environmental applications, the exigency of having more efficient and flexible pulse modulators is now receiving greater consideration. Sensitive applications, such as plasma fusion and laser guns also require more precisely produced repetitive pulses with a higher quality. Many research studies are being conducted in different areas that need a flexible pulse modulator to vary pulse features to investigate the influence of these variations on the application. In addition, there is the need to prevent the waste of a considerable amount of energy caused by the arc phenomena that frequently occur after the plasma process. The control over power flow during the supply process is a critical skill that enables the pulse supply to halt the supply process at any stage. Different pulse modulators which utilise different accumulation techniques including Marx Generators (MG), Magnetic Pulse Compressors (MPC), Pulse Forming Networks (PFN) and Multistage Blumlein Lines (MBL) are currently employed to supply a wide range of applications. Gas/Magnetic switching technologies (such as spark gap and hydrogen thyratron) have conventionally been used as switching devices in pulse modulator structures because of their high voltage ratings and considerably low rising times. However, they also suffer from serious drawbacks such as, their low efficiency, reliability and repetition rate, and also their short life span. Being bulky, heavy and expensive are the other disadvantages associated with these devices. Recently developed solid-state switching technology is an appropriate substitution for these switching devices due to the benefits they bring to the pulse supplies. Besides being compact, efficient, reasonable and reliable, and having a long life span, their high frequency switching skill allows repetitive operation of pulsed power supply. The main concerns in using solid-state transistors are the voltage rating and the rising time of available switches that, in some cases, cannot satisfy the application’s requirements. However, there are several power electronics configurations and techniques that make solid-state utilisation feasible for high voltage pulse generation. Therefore, the design and development of novel methods and topologies with higher efficiency and flexibility for pulsed power generators have been considered as the main scope of this research work. This aim is pursued through several innovative proposals that can be classified under the following two principal objectives. • To innovate and develop novel solid-state based topologies for pulsed power generation • To improve available technologies that have the potential to accommodate solid-state technology by revising, reconfiguring and adjusting their structure and control algorithms. The quest to distinguish novel topologies for a proper pulsed power production was begun with a deep and through review of conventional pulse generators and useful power electronics topologies. As a result of this study, it appears that efficiency and flexibility are the most significant demands of plasma applications that have not been met by state-of-the-art methods. Many solid-state based configurations were considered and simulated in order to evaluate their potential to be utilised in the pulsed power area. Parts of this literature review are documented in Chapter 1 of this thesis. Current source topologies demonstrate valuable advantages in supplying the loads with capacitive characteristics such as plasma applications. To investigate the influence of switching transients associated with solid-state devices on rise time of pulses, simulation based studies have been undertaken. A variable current source is considered to pump different current levels to a capacitive load, and it was evident that dissimilar dv/dts are produced at the output. Thereby, transient effects on pulse rising time are denied regarding the evidence acquired from this examination. A detailed report of this study is given in Chapter 6 of this thesis. This study inspired the design of a solid-state based topology that take advantage of both current and voltage sources. A series of switch-resistor-capacitor units at the output splits the produced voltage to lower levels, so it can be shared by the switches. A smart but complicated switching strategy is also designed to discharge the residual energy after each supply cycle. To prevent reverse power flow and to reduce the complexity of the control algorithm in this system, the resistors in common paths of units are substituted with diode rectifiers (switch-diode-capacitor). This modification not only gives the feasibility of stopping the load supply process to the supplier at any stage (and consequently saving energy), but also enables the converter to operate in a two-stroke mode with asymmetrical capacitors. The components’ determination and exchanging energy calculations are accomplished with respect to application specifications and demands. Both topologies were simply modelled and simulation studies have been carried out with the simplified models. Experimental assessments were also executed on implemented hardware and the approaches verified the initial analysis. Reports on details of both converters are thoroughly discussed in Chapters 2 and 3 of the thesis. Conventional MGs have been recently modified to use solid-state transistors (i.e. Insulated gate bipolar transistors) instead of magnetic/gas switching devices. Resistive insulators previously used in their structures are substituted by diode rectifiers to adjust MGs for a proper voltage sharing. However, despite utilizing solid-state technology in MGs configurations, further design and control amendments can still be made to achieve an improved performance with fewer components. Considering a number of charging techniques, resonant phenomenon is adopted in a proposal to charge the capacitors. In addition to charging the capacitors at twice the input voltage, triggering switches at the moment at which the conducted current through switches is zero significantly reduces the switching losses. Another configuration is also introduced in this research for Marx topology based on commutation circuits that use a current source to charge the capacitors. According to this design, diode-capacitor units, each including two Marx stages, are connected in cascade through solid-state devices and aggregate the voltages across the capacitors to produce a high voltage pulse. The polarity of voltage across one capacitor in each unit is reversed in an intermediate mode by connecting the commutation circuit to the capacitor. The insulation of input side from load side is provided in this topology by disconnecting the load from the current source during the supply process. Furthermore, the number of required fast switching devices in both designs is reduced to half of the number used in a conventional MG; they are replaced with slower switches (such as Thyristors) that need simpler driving modules. In addition, the contributing switches in discharging paths are decreased to half; this decrease leads to a reduction in conduction losses. Associated models are simulated, and hardware tests are performed to verify the validity of proposed topologies. Chapters 4, 5 and 7 of the thesis present all relevant analysis and approaches according to these topologies.

High-voltage modular power supply using parallel and series configurations of flyback converter for pulsed power applications

To cover wide range of pulsed power applications, this paper proposes a modularity concept to improve the performance and flexibility of the pulsed power supply. The proposed scheme utilizes the advantage of parallel and series configurations of flyback modules in obtaining high-voltage levels with fast rise time (dv/dt). Prototypes were implemented using 600-V insulated-gate bipolar transistor (IGBT) switches to generate up to 4-kV output pulses with 1-kHz repetition rate for experimentation. To assess the proposed modular approach for higher number of the modules, prototypes were implemented using 1700-V IGBTs switches, based on ten-series modules, and tested up to 20 kV. Conducted experimental results verified the effectiveness of the proposed method

A Novel VSI- and CSI-Fed Active-Reactive Induction Motor Drive with Sinusoidal Voltages and Currents

Till date load-commutated inverter (LCI)-fed synchronous motor drive configuration is popular in high power applications (>10 MW). The leading power factor operation of synchronous motor by excitation control offers this simple and rugged drive structure. On the contrary, LCI-fed induction motor drive is absent as it always draws lagging power factor current. Therefore, complicated commutation circuit is required to switch off thyristors for a current source inverter (CSI)-driven induction motor. It poses the major hindrance to scale up the power rating of CSI-fed induction motor drive. Anew power topology for LCI-fed induction motor drive for medium-voltage drive application is proposed. A new induction machine (active-reactive induction machine) with two sets of three-phase winding is introduced as a drive motor. The proposed power configuration ensures sinusoidal voltage and current at the motor terminals. The total drive power is shared among a thyristor-based LCI, an insulated gate bipolar transistor (IGBT)-based two-level voltage source inverter (VSI), and a three-level VSI. The benefits of SCRs and IGBTs are explored in the proposed drive. Experimental results from a prototype drive verify the basic concepts of the drive.

Low-inductance axial flux BLDC motor drive for more electric aircraft

As aircraft technology is moving towards more electric architecture, use of electric motors in aircraft is increasing. Axial flux BLDC motors (brushless DC motors) are becoming popular in aero application because of their ability to meet the demand of light weight, high power density, high efficiency and high reliability. Axial flux BLDC motors, in general, and ironless axial flux BLDC motors, in particular, come with very low inductance Owing to this, they need special care to limit the magnitude of ripple current in motor winding. In most of the new more electric aircraft applications, BLDC motor needs to be driven from 300 or 600 Vdc bus. In such cases, particularly for operation from 600 Vdc bus, insulated-gate bipolar transistor (IGBT)-based inverters are used for BLDC motor drive. IGBT-based inverters have limitation on increasing the switching frequency, and hence they are not very suitable for driving BLDC motors with low winding inductance. In this study, a three-level neutral point clamped (NPC) inverter is proposed to drive axial flux BLDC motors. Operation of a BLDC motor driven from three-level NPC inverter is explained and experimental results are presented.

Optimum design of 1.4KV trench IGBTs - The next generation of high power switching devices

The Trench Insulated Gate Bipolar Transistor (IGBT) is the most promising structure for the next generation of power semiconductor devices with wide applications ranging from motor control (1-4 kV) to HVDC (6.5 kV). Here we present for the first time an optimum design of a 1.4kV Trench IGBT using a new, fully integrated optimisation system comprising process and device simulators and the RSM optimiser. The use of this new TCAD system has contributed largely to realizing devices with characteristics far superior to the previous DMOS generation of IGBTs. Full experimental results on 1.4kV Trench IGBTs which are in excellent agreement with the TCAD predictions are reported.

Transient electrothermal simulation of power semiconductor devices

In this paper, a new thermal model based on the Fourier series solution of heat conduction equation has been introduced in detail. 1-D and 2-D Fourier series thermal models have been programmed in MATLAB/Simulink. Compared with the traditional finite-difference thermal model and equivalent RC thermal network, the new thermal model can provide high simulation speed with high accuracy, which has been proved to be more favorable in dynamic thermal characterization on power semiconductor switches. The complete electrothermal simulation models of insulated gate bipolar transistor (IGBT) and power diodes under inductive load switching condition have been successfully implemented in MATLAB/Simulink. The experimental results on IGBT and power diodes with clamped inductive load switching tests have verified the new electrothermal simulation model. The advantage of Fourier series thermal model over widely used equivalent RC thermal network in dynamic thermal characterization has also been validated by the measured junction temperature.© 2010 IEEE.

Series-connected IGBTs using active voltage control technique

With series insulated-gate bipolar transistor (IGBT) operation, well-matched gate drives will not ensure balanced dynamic voltage sharing between the switching devices. Rather, it is IGBT parasitic capacitances, mainly gate-to-collector capacitance Cgc, that dominate transient voltage sharing. As Cgc is collector voltage dependant and is significantly larger during the initial turn-off transition, it dominates IGBT dynamic voltage sharing. This paper presents an active control technique for series-connected IGBTs that allows their dynamic voltage transition dV\ce/dt to adaptively vary. Both switch ON and OFF transitions are controlled to follow a predefined dVce/dt. Switching losses associated with this technique are minimized by the adaptive dv /dt control technique incorporated into the design. A detailed description of the control circuits is presented in this paper. Experimental results with up to three series devices in a single-ended dc chopper circuit, operating at various low voltage and current levels, are used to illustrate the performance of the proposed technique. © 2012 IEEE.

Effect of bandgap narrowing on performance of modern power devices

The effect of the bandgap narrowing (BGN) on performance of power devices is investigated in detail in this paper. The analysis reveals that the change in the energy band structure caused by BGN can strongly affect the conductivity modulation of the bipolar devices resulting in a completely different performance. This is due to the modified injection efficiency under high-level injection conditions. Using a comprehensive analysis of the injection efficiency in a p-n junction, an analytical model for this phenomenon is developed. BGN model tuning has been proved to be essential in accurately predicting the performance of a lateral insulated-gate bipolar transistor (IGBT). Other devices such as p-i-n diodes or punch-through IGBTs are significantly affected by the BGN, while others, such as field-stop IGBTs or power MOSFETs, are only marginally affected. © 2013 IEEE.

Uma fonte chaveada de 50kW com correção de fator de potência para alimentação de uma tocha de plasma Indutiva utilizando técnicas de controle digital

This work deals with the development of an experimental study on a power supply of high frequency that provides the toch plasmica to be implemented in PLASPETRO project, which consists of two static converters developed by using Insulated Gate Bipolar Transistor (IGBT). The drivers used to control these keys are triggered by Digital Signal Processor (DSP) through optical fibers to reduce problems with electromagnetic interference (EMI). The first stage consists of a pre-regulator in the form of an AC to DC converter with three-phase boost power factor correction which is the main theme of this work, while the second is the source of high frequency itself. A series-resonant inverter consists of four (4) cell inverters operating in a frequency around 115 kHz each one in soft switching mode, alternating itself to supply the load (plasma torch) an alternating current with a frequency of 450 kHz. The first stage has the function of providing the series-resonant inverter a DC voltage, with the value controlled from the power supply provided by the electrical system of the utility, and correct the power factor of the system as a whole. This level of DC bus voltage at the output of the first stage will be used to control the power transferred by the inverter to the load, and it may vary from 550 VDC to a maximum of 800 VDC. To control the voltage level of DC bus driver used a proportional integral (PI) controller and to achieve the unity power factor it was used two other proportional integral currents controllers. Computational simulations were performed to assist in sizing and forecasting performance. All the control and communications needed to stage supervisory were implemented on a DSP

V-CE Sensing for IGBT Protection in NPC Three Level Converters-Causes For Spurious Trippings and Their Elimination

Neutral point clamped (NPC), three level converters with insulated gate bipolar transistor devices are very popular in medium voltage, high power applications. DC bus short circuit protection is usually done, using the sensed voltage across collector and emitter (i.e., V-CE sensing), of all the devices in a leg. This feature is accommodated with the conventional gate drive circuits used in the two level converters. The similar gate drive circuit, when adopted for NPC three level converter protection, leads to false V-CE fault signals for inner devices of the leg. The paper explains the detailed circuit behavior and reasons, which result in the occurrence of such false V-CE fault signals. This paper also illustrates that such a phenomenon shows dependence on the power factor of the supplied three-phase load. Finally, experimental results are presented to support the analysis. It is shown that the problem can be avoided by blocking out the V-CE sense fault signals of the inner devices of the leg.

Comportamiento mecánico y eléctrico de un gel de silicona empleado en el encapsulamiento de transistores de potencia tipo IGBT

Resumen: Los materiales dieléctricos son ampliamente utilizados en el sector energético, estando a veces sometidos a condiciones de alto estrés eléctrico, mecánico y ambiental en general, que los ponen al borde de procesos y mecanismos de degradación que conllevan a una probable falla futura. Los geles dieléctricos han comenzado a ser ampliamente utilizados en aplicaciones de encapsulamiento de transistores de alta potencia tipo IGBTs (del inglés Insulated Gate Bipolar Transistor), donde se manejan tensiones y corrientes considerables. En la mayoría de los casos, se necesita una protección para evitar descargas en fase gaseosa, ingreso de humedad al circuito y amortiguamiento mecánico para vibraciones. En el presente trabajo caracterizamos con diferentes técnicas aspectos destacables de este tipo de encapsulantes a base de un gel bifásico de silicona. Para observar el proceso de curado se empleó la técnica de espectroscopía de absorción infrarroja (FTIR), junto con la reología oscilatoria desde las propiedades mecánicas. A su vez, esta última, sirvió para comparar información provista por un novedoso concepto que implica observar a estas últimas desde el interior, a partir de la evolución de cavidades gaseosas generadas eléctricamente. Se comprobó que el comportamiento de estas cavidades es sensible a la historia previa del material, es decir, mecanismos de curado y envejecimiento previo.

Spice modelling of the superjunction IGBT

This paper presents a SPICE model of the SuperJunction Insulated Gate Bipolar Transistor (SJIGBT) [1]. SPICE simulation results are in good agreement with the DESSIS simulation results under DC conditions. This model consists of an intrinsic MOSFET and a parallel combination of a wide and a narrow base pnp BJTs. A parasitic JFET is also included to account for the restricted current flow between two adjacent p-wells. In addition the JFET component also models the additional depletion region caused by the transverse junction at the upper side of the n-drift region where the current is mainly transported via majority carriers.

200V superjunction lateral IGBT fabricated on partial SOI

A 200V lateral insulated gate bipolar transistor (LIGBT) was successfully developed using lateral superjunction (SJ) in 0.18μm partial silicon on insulator (SOI) HV process. The results presented are based on extensive experimental measurements and numerical simulations. For an n-type lateral SJ LIGBT, the p layer in the SJ drift region helps in achieving uniform electric field distribution. Furthermore, the p-pillar contributes to the on-state current. Furthermore, the p-pillar contributes to sweep out holes during the turn-off process, thus leading to faster removal of plasma. To realize this device, one additional mask layer is required in the X-FAB 0.18μm partial SOI HV process. © 2013 IEEE.

IGBT series connection under active voltage control

In this paper an Active Voltage Control (AVC) technique is presented, for series connection of insulated-gate-bipolar-transistors (IGBT) and control of diode recovery. The AVC technique can control the switching trajectory of an IGBT according to a pre-set reference signal. In series connections, every series connected IGBT follows the reference and so that the dynamic voltage sharing is achieved. For the static voltage balancing, the AVC technique can clamp the highest collector-to-emitter voltage to a pre-set clamping voltage level. By selecting the value of the clamping voltage, the difference among series connected IGBTs can be controlled in an accepted range. Another key advantage for AVC is that by changing the reference signal at turn-on, the diode recovery can be optimized. © 2011 EPE Association - European Power Electr.