Instable mechanisms during unclamped operation of high power IGBT modules

The behaviour in terms of robustness during unclamped operations of power IGBT modules is presented. The experimental characterization is aimed to identify the main instable phenomena during unclamped turn-off in power IGBT modules. Several devices of different generations, current and voltage ratings have been analyzed. Thanks to a non-destructive experimental set-up, it is possible to observe instable phenomena without causing the damage of the device under test. In this paper, it is shown that the destructive conditions during unclamped operations are preceded by precursors on the gate side which indicate instable phenomena taking place inside the device. The dependence of the destructive phenomenon on the driver conditions are widely and exhaustively analyzed.     

The robustness of series-connected high power IGBT modules

The behaviour in terms of robustness of series-connected high power IGBT modules is presented, arranged in a topology which ensures voltage balance on IGBT’s and diodes by means of a simple auxiliary circuit applied directly on the high power devices, which are used in hard switching mode. Analyses in terms of IGBT and diode SOA (safe operating area), collector to emitter voltage gradient and short circuit condition are reported as well as an extended experimental characterisation. Both analyses confirm superior switching rating and system reliability, by using two series-connected IGBT in substitution of a single module, same current and double voltage rated. Moreover, thanks the auxiliary circuit presence, the robustness of total system is maintained also in extreme operating conditions.     

Soft switching active snubbers for DC/DC converters

A soft-switching active snubber is proposed to reduce the turn-off losses of the insulated gate bipolar transistor (IGBT) in a buck power converter. The soft-switching snubber provides zero-voltage switching for the IGBT, thereby reducing its high turn-off losses due to the current tailing. The proposed snubber uses an auxiliary switch to discharge the snubber capacitor. This auxiliary switch also operates at zero-voltage and zero-current switching. The size of the auxiliary switch compared to the main switch makes this snubber a good alternative to the conventional snubber or even to passive low-loss snubbers. The use of the soft-switching active snubber permits the IGBT to operate at high frequencies with an improved RBSOA. In the experimental results reported for a 1 kW, 40 kHz prototype, combined switching/snubbing losses are reduced by 36% through the use of the active snubber compared to a conventional RCD snubber. The use of an active snubber allows recovery of part of the energy stored in the snubber capacitor during turn-off. The generic snubber cell for the buck power converter is generalized to support the common nonisolated DC/DC power converters (buck, boost, buck-boost, Cuk, sepic, zeta) as well as isolated DC/DC power converters (forward, flyback, Cuk, and sepic)     

IGBT RBSOA失效分析及改善方案

一种绝缘栅双极晶体管模块在做反向偏置安全工作区测试时,器件在较低的关断电流下就发生了损坏。失效分析显示失效区的位置靠近栅极条区。模拟显示失效区处元胞结构并非对称,而正常元胞结构是对称的,由此造成了该处元胞的闩锁电流密度比对称结构元胞的闩锁电流密度低。因此,元胞结构的一致性不好是RBSOA关断电流低的原因。通过修改版图设计,使工作区元胞结构一致。对改版后的芯片封装后进行RBSOA测试,结果显示安全关断电流有明显提高。     

The high frequency behaviour of high voltage and current IGBT modules

Sharp voltage gradients act as a stimulus for high power IGBT modules, which can exhibit a potentially instable high frequency behaviour. In fact, they can act as a radio frequency amplifier and, in particular operating conditions, the interaction between the device and the control or the external circuit can cause self-sustaining oscillations or the enhancement of the unevenness in current distribution inside a power module thus having a significant impact on the reliability of the power converter. Moreover, this RF amplification worsen the generated EMI (Electro Magnetic Interference). This paper presents an extensive experimental investigation about the high frequency behaviour of IGBT high power modules. The measurements were performed by means of an original experimental set-up that was specifically conceived and constructed. The data are analysed with the help of a theoretical small signal model which is able to describe RF behaviour of high power IGBT modules.     

Experimental and numerical study of the emitter turn-off thyristor(ETO)

The emitter turn-off thyristor (ETO) is a new family of high power semiconductor devices that is suitable for megawatt power electronics application. ETOs with voltage and current ratings of 4-6 kV and 1-4 kA, have been developed and demonstrated. And those power levels are the highest in silicon power devices and are comparable to those of the gate turn-off thyristor (GTO). Compared to the conventional GTO, the ETO has much shorter storage time, voltage controlled turn-off capability, and much larger reverse biased safe operation area (RBSOA). Furthermore, ETOs have a forward-biased safe operation area (FBSOA) that enables it to control the turn-on di/dt similar to an insulated gate bipolar transistor (IGBT). These combined advantages make the ETO based power system simpler in terms of dv/dt snubber, di/dt snubber, overcurrent protection, resulting in significant savings in the system cost. This paper presents experimental and numerical results that demonstrate the advantages of the ETO     

Investigation of the power dissipation during IGBT turn-off using a new physics-based IGBT compact model

New compact models of the IGBTs (both non-punch through IGBT (NPTIGBT) and punch-through IGBT (PTIGBT)) are presented in this paper. The models are implemented in the SABER circuit simulator and used for a study of IGBT anode current and voltage characteristics during a device turn-off (clamped inductive load circuit with gate controlled turn-off), since these parts of the transient characteristics essentially predict the power dissipation (V×I) inside the device. It is shown that PTIGBTs are faster than NPTIGBTs, this becoming more apparent at higher clamp voltages.     

Performance and reliability testing of modern IGBT devices under typical operating conditions of aeronautic applications

As for railway traction applications, aeronautical power electronics implies high power density handling. Moreover typical aeronautical applications impose a harsh thermal environment. SiC technology has recently emerged for high power and high temperature application, but is not yet mature enough. Consequently it is still important to push the silicon devices temperature limits in order to increase the amount of switched power. Device ageing is accelerated and there exists the risk of catastrophic failure by thermal runaway. In order to design correctly high temperature power systems, knowing the IGBT characteristics at extended temperature ranges becomes essential. This paper describes an experimental setup and test procedure conceived to experiment with different available IGBT technologies at temperatures beyond the limits rated by manufacturers (?55 °C, +175 °C). The aim is to characterize the devices for a better understanding and optimized safe application. This will ease prototyping for future development of IGBT modules in aircraft.     

Some observation dealing with the failures of IGBT transistors in high power converters

The explosion strength of high power IGBT modules is one of the important parameters that may decide on converter equipment reliability in extreme circumstances. The explosion strength of a device is represented by the peak value of the collector current (so called “peak case nonrupture current”) that cannot be exceeded. Some main IGBT failure mechanisms under service conditions are discussed. Test methods and experimental results on device case explosion strength are presented. Experiences concerning starting, tests and service of high IGBT converters are given. Preliminary load tests with rapidly changing current values are useful for newly fabricated IGBT converters.     

Advanced RBSOA analysis for advanced power BJTs

Performances of some modern power BJT's in inductive turn-off are experimentally evaluated, by means of an unclamped non-destructive method. The different instabilities exhibited are classified and their influence on device performances is discussed both in clamped and unclamped applicationsAn “Instability Map” is proposed both as a synthetic picture which eases comparison of reverse-bias performances of devices having different ratings, and as an investigation tool for linking device behaviour to its physical features.It results that RBSOA performances are not just related to lateral dimensions of the emitter, but also to metallization lay-out of the chip, which evidently influences current distribution among cells.Finally, stray elements of testing circuit which affect results of RBSOA measurements are investigated, and some suggestions are proposed in order to let measurement results become independent of testing circuit.     

A study on the short-circuit capability of field-stop IGBTs

The short-circuit failure mechanism of 1200 V trench gate field-stop insulated gate bipolar transistor (IGBT) has been investigated in this paper. Experimental testing shows that most of the devices failed during the blocking state after a few hundred microseconds of the short-circuit turn-off condition. This unusual failure mode was analyzed both with experimental and numerical investigation. It has been determined that due to significantly large leakage current, thermal run-away can occur causing device failure after short circuit turn-off. Due to the smaller heat capacity of the FS-IGBT structure, the device temperature after the turn-off becomes so high that the local heating produced by the high temperature leakage current results in the thermal run-away.     

一种具有部分高介电常数介质调制效应的IGBT

提出了一种具有高介电常数介质填充沟槽的绝缘栅双极晶体管(IGBT).分析了高介电常数介质调制效应.结果表明,与普通场阻型IGBT相比,该器件的击穿电压提高了 8％,通态压降减小了 8％,关断损耗降低了 11％;在相同通态压降下,该器件的关断损耗降低了 35％.在栅极与原HK介质之间增加介电常数更高的介质,进一步提升了该...     

Robustness test and failure analysis of IGBT modules during turn-off

Considering the typical operational conditions of railway traction applications, this paper proposes an insightful study of the failure mechanism of IGBT modules when exposed to various limit load conditions during turn-off. First, the results of extensive experimental analysis are presented. These are based on a dedicated test-circuit and point out a repetitive failure mechanism. This is subsequently investigated by means of simulations based on a compact model which includes all major and secondary electro-thermal effects (i.e. latch-up). The results enable an interpretation of the observations and point out how the limits of transient safe operation can be significantly reduced by parasitic effects.     

A soft switching active snubber optimized for IGBT's in singleswitch unity power factor three-phase diode rectifiers

This paper describes a soft switching active snubber for an IGBT operating in a single switch unity power factor three-phase diode rectifier. The soft switching snubber circuit provides zero-voltage turn-off for the main switch. The high turn-off losses of the IGBT due to current tailing are reduced by zero-voltage switching. This allows the circuit to be operated at very high switching frequencies with regulated DC output voltage, high quality input current and unity input power factor. Simulation and experimental results are included     

Assessment of the Trench IGBT reliability: low temperature experimental characterization

The purpose of this study is an assessment of the Trench IGBT reliability at low temperature under static and dynamic operations by the aim of intensive measurements. The analysis of the Trench IGBT behaviour in these conditions is dedicated to the HEV applications. One question can be raised in case of the use of HEV in countries where during winter the temperature drops down −50 °C or less: are Trench IGBT strongly affected by the low temperature environment? In this paper, we present experimental results under various test conditions (temperature, gate resistance, voltage and current) to give an understanding of the device behaviour by focusing on the device current and voltage waveforms and the power losses.     

IGBT关断瞬态电压尖峰影响及抑制

绝缘栅双极晶体管(IGBT)是一种性能优良的全控型电力电子器件,由于线路和器件内部分布电感的存在,关断时集电极电流的快速变化会感应产生一个较大的电压尖峰从而引起过电压击穿。分析了栅极结电容放电时间常数和拖尾电流对电压尖峰的影响,通过改变栅极驱动电阻和温度可以抑制电压尖峰。分析了电压尖峰引起过压击穿的失效机理以及失效模式,表明IGBT过压击穿引起失效的本质仍然是结温过高引起的热击穿失效。     

软特性650V IGBT：低电磁干扰和电压尖峰的优化器件

近年来,功率半导体厂商致力于提高器件的开关速度,这带来了开关损耗降低和系统能效提升的益处。这些功率器件需要优化的直流电路寄生电感（Ls）。为了满足具有大电流的高功率应用的需求,推出了一种全新的芯片650V IGBT4,旨在提供更大的设计自由度。这款全新的IGBT4器件具备更好的关断软度,并且由于关断电流变化率di／dr...     

Dual MOS gate controlled thyristor (DMGCT) structure withshort-circuit withstand capability superior to IGBT

A dual MOS gate controlled thyristor (DMGCT) structure is analyzed with experimental data and shown to have superior performance over insulated-gate bipolar transistor (IGBT) for power switching applications. The DMGCT device structure consists of a thyristor structure with the thyristor current constrained to flow via the channel region of a MOSFET. Although this increases the on-state voltage drop in the thyristor current path by a small amount due to the voltage drop across the low-voltage series MOSFET, this structure allows control of the thyristor current by the gate voltage applied to the MOSFET even after latch-up of the thyristor. This configuration allows uniform turn-off in the device with no current crowding. The DMGCT does not have any parasitic thyristor structure. In contrast to the IGBT, the saturation current of the DMGCT can be controlled independently of the on-state voltage drop     

Current state-of-the-art and future prospects for power semiconductor devices in power transmission and distribution applications

Since the first commercially viable thyristors appeared in the early 1960s, there has been a dramatic increase in the switched power ratings and versatility of high-voltage power semiconductor devices. By the mid 1970s, thyristors with switched power ratings of several MVA were being applied in high voltage dc transmission systems and static VAr compensators. The introduction, in the 1980s, of controlled turn-off devices, such as the gate turn-off thyristor (GTO) and insulated gate bipolar transistor (IGBT), broadened the application of high-voltage power devices to hard-switched converters and, by the start of the 21st century, controllable silicon power devices were available with voltage ratings of 12?kV and switched power capabilities of up to 40?MVA. A review of the current state-of-the-art in silicon high-voltage power semiconductor technology covers gate-commutated thyristors (GCT, IGCT) and IGBT devices, including the injection-enhanced IGBT or IEGT. Despite these considerable achievements, there is now mounting evidence that silicon-based power semiconductors are reaching their limit, both in terms of voltage rating and of switched power capability. The introduction of wide-band-gap semiconductor materials such as silicon carbide offers the potential to break through the voltage-switching frequency limitations of silicon, with power-switching frequency products more than two orders of magnitude higher. An analysis of the current status and future prospects for silicon carbide power electronic devices is presented, together with a case study comparing a variety of silicon and silicon carbide solutions in a 10?kV hard-switched converter application. It is shown that an all-silicon carbide switch offers the best electrical performance and lowest cost solution, in spite of higher per unit area device costs.     

IGBT过流关断主结边缘烧毁失效机理研究

针对4 500 V IGBT在过流关断过程中主结边缘烧毁失效的问题,设计了3种不同场板连接结构。为了分析失效机理,采用Sentaurus TCAD工具对IGBT的过流关断过程进行仿真,重点研究了主结边缘附近3种场板结构对过流关断的影响。结果表明,IGBT电阻区边缘场板结构参数是影响坚固性的重要因素,在一定程度上减小场板连接的倾斜角,可减弱主结附近电场强度,避免过流关断过程中器件在该处发生烧毁,提升了器件的动态坚固性。