Thyristors and Power Devices

After a hype and a consolidation phase regarding the potential of silicon carbide based components in power electronics (mostly diodes and switches), we are observing a solid penetration of these components in modern solutions even for power ratings of several kW. Benefits of these new power devices are now more clearly identified and applications were depicted where the use of these new components, in particular Schottky barrier diodes available from Infineon and Cree, can be a technical and commercial access. For a further market penetration, new generations of diodes as well as powerful switching devices are released recently resp. ready to commercialization. Especially upcoming markets for high voltage power devices offering not only high power densities, but energy saving as well push these developments. Supported by the improvements in base material quality and size, SiC power devices are believed to be on the hop to a next important step regarding its propagation in a broader range of applications. The paper will sketch these recent developments and will show how the improved performance can provide new perspectives in conventional systems as well as new solutions.

The introduction of next generation mobile systems and alternative applications demands significant improvement in efficiency and linearity of the power amplifier. It is essential to understand the limitations inherent to the power transistor, and improve it for emerging applications. The package containing the power transistor is built up of various components; MOS capacitors, bond wire arrays and ESD protection circuitry common in commercial power transistors in addition to the semiconductor transistor die. The objectives of this work are to develop multiphysics modelling components which are needed for CAD-based design optimisation. An electrothermal bond wire array model is proposed which combines the electrical and thermal characteristics at high-frequency, reproducing the non-uniform distribution seen in measurements. The model returns the temperature distribution over 2000-times faster, in a fraction of a second, compared to an equivalent 3D multiphysics simulation which takes at least 23 minutes, making it well suited to circuit modelling for CAD-design and optimisation. Fundamentally, the foundations of the power transistor is the semiconductor technology that the package holds. Extraction of compact transistor models is time consuming, requiring a multitude of measurement steps and specialised equipment. Behavioural modelling techniques simplify the measurement extraction procedure, while conserving the accuracy and convergence needed for circuit modelling. A primary limiting factor of the X-parameter behavioural model is that it lacks thermal memory effects that are prevalent in most applicable transistor technologies. This work extends the extraction of X-parameters to include dynamic thermal memory effects. Thermal hysteresis is demonstrated and shown to introduce spectral asymmetry during simulations using two-tone and QAM-16 modulation stimulus. Furthermore, distributed multiphysics modelling techniques co-simulate electromagnetics, thermodynamics and semiconductor device physics - the coupled solution providing enhanced insight into the performance and limitations of the transistor compared to lumped modelling approaches. A distributed electrothermal model was developed which enables significant design improvements by optimisation of the thermal and electrical layouts. This is demonstrated at 28~GHz for a GaN pHEMT transistor where a 12% increase in linear output power and 54% increase in PAE is achieved relative to the peak efficiency of the transistor (24%). The multiphysics modelling components developed in this work aim to improve power transistors for next generation mobile systems and applications requiring the efficient application of high-power microwaves.

Dynamic control of electromagnetic-emission, efficiency, and stress of switching power systems using optically-modulated and galvanically isolated gate control of power semiconductor devices (PSDs) is outlined and experimentally demonstrated at a scaled power level. This is achieved by modulating the switching dynamics of a PSD using an optically triggered power transistor (OTPT), which controls the gate excitation of the PSD. An important aspect regarding scalability of the same concept towards higher power application is the controllability of the PSD onset delay (which can be optically modulated, and as demonstrated, in the proposed device concept) particularly for series/parallel connected device configurations for high voltage and current applications.

In electrical power devices, ac losses from a superconductor is a primary factor which determines their usefulness as commercial power equipment. For this reason, extensive studies have been carried out on the losses of Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}/Ag, [Bi(2223)/Ag], tapes. These studies were mostly limited to a single isolated tape. However, a conductor in a power device is surrounded by other conductors and the precise magnetic field distribution around it is very different from that for a single conductor carrying currents or in ac fields. Since the precise field distribution in and around a superconductor is critical in determining the losses, it is very important to measure and to understand the losses in Bi(2223)/Ag tapes which are surrounded by other tapes as in a power device. Taking this fact into consideration, recently the authors have studied ac losses in stacks of Bi(2223)/Ag tapes in parallel and perpendicular applied fields and shown that they can calculate the losses in these cases utilizing the critical state model if a number of appropriate factors about properties of the tape are taken into a consideration. However, in a power device such as a transformer, magnetic fields near the ends of a solenoid vary from parallel to perpendicular with the tape face. Thus, it is important to learn the behavior of the losses in the stacks of Bi(2223)/Ag tapes with respect to the variations in the angle between the applied field direction and the tape face. In order to accomplish this, they measured the angular dependence of the losses in the stacks which were made from two different Bi(2223)/Ag tapes. Here they report this result and discuss under what conditions they can calculate the losses with a reasonable accuracy. The angular dependence of the losses in ac applied fields were measured using a series of stacked Bi(2223)/Ag tapes having the angles with the direction of applied fields of 0, 7.5, 15, 30, 45, 60, and 90 degrees. The measured values of the losses were compared with the calculated values. The calculations were performed using the measured losses for the 0 and 90 degrees orientations and assuming the losses can be separated for the currents circulating in the plane of and across the tapes. It was shown that at very high fields, i.e., well above the full penetration fields, this assumption was justified by the observed good agreement between the measured and the calculated losses for both tapes. However, at the low fields, significant deviations between the calculated and the measured were seen for both of the tapes. One possible contributing factor to this discrepancy is the non-ideal shape of the tape cross sections. This can causes the field distribution near the edges of the slabs to deviate from that for an assumed uniform infinite slab. This makes the actual fields at the edge regions to be greater than the applied fields. Thus, the losses will be higher than those calculated. Although not having a full understanding of the losses at low fields is of concern, it will not be of a great importance in the designs of power devices in practice. This is due to the fact that the values of the losses at low fields are orders of magnitudes lower than those at high fields and thus the primary concern for the power device development is the reduction of the losses at high fields.

A New Rotary Powered Device for Bone Marrow Aspiration and Biopsy Yields Superior Specimens with Less Pain: Results of a Randomized Clinical Study

In this letter, a planar integration using the deep trench isolation (DTI) technique is proposed to suppress the inter-well parasites in smart power integrated circuits implemented in 0.35 µm BiCMOS technology. In this technology, all devices share the same epitaxial layer. This can lead to a punch-through between power devices as well as between power and low-voltage CMOS devices. A DTI scheme is used to suppress the effect of the parasitic BJT by using a P+ retardation implant region under the deep trench isolation region. The injection ratio of the parasitic BJT is reduced by a factor between 3 and 8.5. The effect of the trench length and the retardation implant is investigated using SENTAURUS TCAD simulations. It is confirmed, through using TCAD simulations, that the amount of the collected carriers of the sensitive devices changes as a function of the trench length and the presence of the retardation implant.

Power devices (PD) are ubiquitous elements of the modern electronics industry that must satisfy the rigorous and diverse demands for robust power conversion systems that are essential for emerging technologies including Internet of Things (IoT), mobile electronics, and wearable devices. However, conventional PDs based on “bulk” and “single-crystal” semiconductors require high temperature (> 1000 °C) fabrication processing and a thick (typically a few tens to 100 μm) drift layer, thereby preventing their applications to compact devices, where PDs must be fabricated on a heat sensitive and flexible substrate. Here we report next-generation PDs based on “thin-films” of “amorphous” oxide semiconductors with the performance exceeding the silicon limit (a theoretical limit for a PD based on bulk single-crystal silicon). The breakthrough was achieved by the creation of an ideal Schottky interface without Fermi-level pinning at the interface, resulting in low specific on-resistance Ron,sp (< 1 × 10–4 Ω cm2) and high breakdown voltage VBD (~ 100 V). To demonstrate the unprecedented capability of the amorphous thin-film oxide power devices (ATOPs), we successfully fabricated a prototype on a flexible polyimide film, which is not compatible with the fabrication process of bulk single-crystal devices. The ATOP will play a central role in the development of next generation advanced technologies where devices require large area fabrication on flexible substrates and three-dimensional integration.

Condition monitoring (CM) technology plays an important role in ensuring the reliable operation of power semiconductor devices. Power semiconductor devices can generate stress waves when turned on and off, and the stress waves released by the device can be detected by the acoustic emission (AE) sensor. AE detection technology has the characteristics of both nondestructive and real-time, and is expected to be applied to the CM of power semiconductor devices in the future. However, temperature and electromagnetic fields can both affect the output characteristics of the AE sensor, which is not conducive to the application of AE detection technology. In addition, it is not clear how temperature affects the stress waves generated by power semiconductor devices. In this article, a novel stress wave extraction method for power semiconductor devices is proposed, and the influence of temperature on the stress wave generated by insulated gate bipolar transistor (IGBT) at the turn-off moment is explored. Besides, a signal characteristic of the stress waves associated with the junction temperature of the device is extracted as the temperature-sensitive acoustic parameter, which will lay the foundation for the future research of new methods for online monitoring of junction temperature.

Accurate modeling of self-heating effect in power transistors is crucial for reliable design and performance evaluation of wireless communication circuits and systems. This letter presents an enhanced time delay neural network (TDNN) technique specifically developed to model power transistors considering self-heating effect. At first, an enhanced TDNN model topology suitable for power transistors is proposed. To accurately describe the self-heating effect, a thermal sub-circuit is incorporated into the model framework. Moreover, novel formulations for direct current, small-signal S-parameters, and large-signal harmonic balance outputs of the proposed TDNN are derived so that typical measurement data can be utilized for model training. Finally, training algorithm is also proposed to effectively optimize the weighting and thermal parameters in the proposed TDNN model. The effectiveness of the proposed technique is validated through a modeling example involving a practical power transistor. The resulting TDNN model is embedded in Keysight Advanced Design System, and simulation results based on this model demonstrate good agreement with the measured data.

This study aims to implement a power device and to evaluate its characteristics for expecting to integrate it with an implantable biomedical system in the future. The power device mainly consists of a commercial Li-ion battery with a dimension of 30 × 20 × 4 mm3 and with a capacity of 120 mAH, a charge IC, and a protection IC. First, from the results of the battery evaluation obtained by charge, discharge, and cycle life tests, we find that the battery matches the basic requirements for applying it to implantable and rechargeable biomedical system. Further, in the following inductive powering experiment for the developed power device, we also find that, when the powering coupling distance is within 3 to 5 cm, the battery can be charged fully after about 50 minutes and still maintain low temperature rise (< 1 0C). Thus, if the power device is packaged properly, it can be applied to implantable biomedical system for long-term and safe usage.

To ascertain the damage mechanism caused by high-energy proton irradiation to AlGaN/GaN power devices of enhanced Cascode structures, we study the radiation effect of enhanced Cascode structure and depletion AlGaN/GaN power devices by using 60 MeV energy protons in this work. In the case of proton injection reaching 1×10&lt;sup&gt;12&lt;/sup&gt; p/cm&lt;sup&gt;2&lt;/sup&gt;, the experimental results show that the threshold voltage of the Cascode type device is negatively drifted, the transconductance decreases, and the peak leakage current increases. The threshold voltage decreases from 4.2 V to 3.0 V, with a decrement of 1.2 V, and the peak transconductance value decreases from 0.324 S/mm to 0.260 S/mm, with a decrement of about 19.75%. There is no significant change after the conventional depleted AlGaN/GaN device has been irradiated. The Cascode-type AlGaN/GaN power device is more sensitive to proton irradiation than the depletion-type AlGaN/GaN device. The Cascode-type device is sensitive to proton irradiation because of its structure connected to a silicon-based MOS tube. Proton irradiation causes the silicon-based MOS gate oxide layer to generate a large amount of net positive charge, induces an ionization damage effect, and causes threshold voltage to negatively drift and the gate leakage current to increase. The equivalent 60 MeV energy protons and cumulative injection of 1×10&lt;sup&gt;12&lt;/sup&gt; p/cm&lt;sup&gt;2&lt;/sup&gt; dose of the &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}$ {}_{}{}^{60}\rm{C}\rm{o}~\rm{\gamma } $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M2.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M2.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; radiation device is used to obtain the ionization damage effect. It is found that after being irradiated by the equivalent dose &lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}${}_{}{}^{60}\rm{C}\rm{o}~\rm{\gamma }$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M3.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M3.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; ray , the device has the threshold voltage decreasing from 4.15 V to 2.15 V, with a negative drift of 2 V; transconductance peak decreases from 0.335 S/mm to 0.300 S/mm, with an approximate decrement of 10.45%. The degradation of the electrical properties of the device after being irradiated by &lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}${}_{}{}^{60}\rm{C}\rm{o}~\rm{\gamma }$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M4.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M4.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; ray is consistent with the degradation law after being irradiated by high-energy protons. In order to further verify the experimental accuracy and conclusions, the ionization energy loss and non-ionization energy loss induced by radiation in the device are obtained by Monte Carlo simulation. The simulation results show that the ionization energy loss induces silicon-based MOS to generate oxide trap charge and interfacial state trap charge, which is mainly responsible for the performance degradation of AlGaN/GaN HEMT power devices with enhanced Cascode structure.

Aluminum based wire-bonds are still representing the most important technology for the chip top side connection in power devices. At the same time, they often limit the reliability and lifetime of the overall power device or module. Hence, knowledge of the wire-bond reliability can be key for predicting and modelling the lifetime of the whole electronics assembly.In this paper, a short overview of load and design based lifetime models for power devices and modules together with their limitations will be given. Based on this, the requirements as well as the necessary process steps for developing a more generic lifetime model for wire-bond degradation using stress and damage parameters are discussed. This includes the development of global-local finite element models as well experimental measurements and test for material characterization, model calibration and validation. Finally, first results of a parametric finite element study evaluating the wire-bond lifetime depending on different geometry parameters and material combinations will be provided.

Hybrid DC switches have been intensively studied because of the increasing demand for DC power distribution systems. A hybrid switch consists of high-speed mechanical contacts, semiconductor power devices, and metal– oxide varistor elements. Make arcs are suppressed from occurring by turning on the power device connected in parallel before closing the contacts. In the opening period, the contact voltage increases and microsecond make arcs occur intermittently during the rise of contact voltage exceed the boiling voltage of the contact material. The arc voltage turns on the power device and subsequently the circuit current commutates from the contacts to the power device. The DC current is interrupted by the power device with varistors. Although the duration of make arcs was a few 10 m s, the contact surface was degraded and the insulation strength decreased up to 20% in 1 kA DC commutation.

Two main classes of optical TEMPEST attacks against the confidentiality of information processed/delivered by devices have been demonstrated in the past two decades; the first class includes methods for recovering content from monitors, and the second class includes methods for recovering keystrokes from physical and virtual keyboards. In this paper, we identify a new class of optical TEMPEST attacks: recovering sound by analyzing optical emanations from a device's power indicator LED. We analyze the response of the power indicator LED of various devices to sound and show that there is an optical correlation between the sound that is played by connected speakers and the intensity of their power indicator LED due to the facts that: (1) the power indicator LED of various devices is connected directly to the power line, (2) the intensity of a device's power indicator LED is correlative to the power consumption, and (3) many devices lack a dedicated means of countering this phenomenon. Based on our findings, we present the Glowworm attack, an optical TEMPEST attack that can be used by eavesdroppers to recover sound by analyzing optical measurements obtained via an electro-optical sensor directed at the power indicator LED of various devices (e.g., speakers, USB hub splitters, and microcontrollers). We propose an optical-audio transformation (OAT) to recover sound in which we isolate the speech from optical measurements obtained by directing an electro-optical sensor at a device's power indicator LED. Finally, we test the performance of the Glowworm attack in various experimental setups and show that an eavesdropper can apply the attack to recover speech from speakers' power LED indicator with good intelligibility from a distance of 15 meters and with fair intelligibility from 35 meters.

A new power convertor, using power transistors in a switching mode as the main power elements, has been introduced. This convertor is capable of conversion from a fixed 3-phase source to variable frequency, controlled output current, such that the operating frequency range is not limited by the supply frequency. The power transformers, inductors and capacitors normally associated with many existing forms of such a convertor are no longer needed. Further advantages of the new convertor are that it is capable of accepting regenerative power, operates without the need for a d.c. link and the input displacement factor is unity, regardless of the output condition.A new mode of operation, that of class ABD, has been introduced, which allows the switching rate of the power transistors to be considerably reduced for a given output. Such a technique reduces switching losses and results in a much less severe operational environment for the power transistors. It also helps to improve the power factor to a value close to unity.The present paper describes a 3-phase to single-phase convertor but the method can be used to provide a fully-regenerative 3-phase to 3-phase static converter, using only 18 power elements and producing a variable frequency, 3-phase controlled output current whose waveform is a very close approximation to a sinusoid.