Static Induction Thyristor Research Articles

Ultrasonic butt welding of aluminum, aluminum alloy and stainless steel plate specimens

Welding characteristics of aluminum, aluminum alloy and stainless steel plate specimens of 6.0 mm thickness by a 15 kHz ultrasonic butt welding system were studied. There are no detailed welding condition data of these specimens although the joining of these materials are required due to anticorrosive and high strength characteristics for not only large specimens but small electronic parts especially. These specimens of 6.0 mm thickness were welded end to end using a 15 kHz ultrasonic butt welding equipment with a vibration source using eight bolt-clamped Langevin type PZT transducers and a 50 kW static induction thyristor power amplifier. The stainless steel plate specimens electrolytically polished were joined with welding strength almost equal to the material strength under rather large vibration amplitude of 25 μm (peak-to-zero value), static pressure 70 MPa and welding time of 1.0–3.0 s. The hardness of stainless steel specimen adjacent to a welding surface increased about 20% by ultrasonic vibration.

高効率固体化パルス電源を用いたTEA CO<SUB>2</SUB>レーザ発振

We have studied and developed a high efficiency and a high repetition rate transversely excited atmospheric pressure CO2 laser by an all solid-state pulsed power generator. The pulsed power generator consists of a high speed turn-on static induction thyristor and a single-stage magnetic pulse compression circuit using a saturable transformer. The static induction thyristor was improved in the switching speed and a switching loss. The saturable transformer with a Fe-based nano-crystalline magnetic core has two functions of voltage gain and pulse compression. The maximum switching voltage was 4.1 kV. The output voltage was 34.5 kV. On the other hand, the laser head is consisted of uniform field main discharge electrodes and corona preionized electrodes. Maximum laser energy of 3.2 J was obtained. The energy transfer efficiency of the pulsed power generator was 93% and the laser efficiency of 13.8% was obtained. An overall laser efficiency of 12.9% was obtained. The high speed static induction thyristor and the simple magnetic pulse compression circuit realized the high energy transfer efficiency and the high laser efficiency.

Performance of pulsed power generator using high-voltage static induction thyristor

In a present pulsed power generator system using semiconductor switches, saturable magnetic switches are usually connected in series to compress the output pulse because the current rise-time of semiconductor switches are generally not short enough, However, the magnetic switches are heavy and they reduce the energy transfer efficiency. So we propose a pulsed power generator system using a 5500-V static induction thyristor (SI-Thy), a Blumlein line for pulse formation, and a step-up pulse transformer. The fundamental characteristics of the generator are evaluated. From experiments using only one SI-Thy, turn-on time of several tens of nanoseconds and the maximum rise rate of the output voltage of 115-kV//spl mu/s are obtained. It is confirmed that an SI-Thy will have sufficient performance as a main switch of the pulsed power generator for the flue gas treatment and decomposition of hazardous gases when several SI-Thys are connected in series.

Development of a Static Induction Thyristor for Electric Power Application

It is desirable that ac/dc converter for system interconnection (such as High Voltage Direct Current transmission system) should have following performance. (1) The converter does not fail to carry out commutation even when a voltage dip or distortion has broken out in the ac system. (2) The converter is able to send power from a healthy ac system even when another ac side has completely failed. (3) The converter is able to reduce generation of harmonics power in the network. It is necessary to improve characteristics of power semiconductor devices besides adoption of self-commutated ac/dc converter and development of control scheme. IGBT (Insulated Gate Bipolar Transistor), IEGT (Injection Enhanced Gate Transistor), GCT (Gate Commutated Turn off Thyristor) and Static Induction Thyristor (SITh) will be able to refine the characteristics. Especially SITh has high di/dt and dv/dt critical ratio and high switching characteristics. It is expected to apply SITh to power system in the future.From these background, 4.5kV-1kA SITh which consists of 70mm in diameter pellet with the planer gate structure has been developed. This SITh shows a normally-off characteristic because of a low concentration p-base layer under n-emitter, and has a pin-base structure. For lifetime control, electron irradiation and proton implantation were used. A 5kHz-frequency test in a chopper drive was achieved in condition of 2250V as a supply voltage and 270A as a rectangular on-state current. Adopting a hard drive operation, a snubberless turn-off drive of I000A as an anode current was also achieved.

A new static induction thyristor (SITh) analytical model

In this paper, an analytical static induction thyristor (SITh) model is proposed based on device internal physical operating mechanisms. The nonquasi-static model predicts both device static and dynamic characteristics. The model accounts for effects of the device structure, lifetime, and temperature. Implemented in PSPICE as a subcircuit, model simulation results are compared with numerical simulation and experiment results for various electrical and thermal conditions. The model exhibits accurate results, good convergence, and fast simulation speed.

Degradation of MOS tunnel structures at high current density

The stability of tunneling-thin (2–3 nm) SiO2 films during prolonged flow of high-density currents (102–103 A/cm2) was investigated. A sharp increase in the charge which a tunneling MOS structure is capable of transmitting without degradation on switching from Fowler-Nordheim injection to direct tunneling (103 C/cm2 and 107 C/cm2, respectively) was observed. The degradation of SiO2 films was investigated using Al/SiO2/n-Si/p +-Si thyristor structures with a positive bias on the semiconductor, i.e., with reverse bias of the MOS structure. The use of these devices accounted for the uniformity of the current distribution over the area and made it possible to monitor the state of the insulator layer by measuring the device gain in the phototransistor mode.

A Reverse Conduction Static Induction Thyristor Model for Circuit Simulation

In a field of simulation concerning semiconductor power devices, there are process simulation, device simulation, circuit simulation. These simulations are selected for their purpose. In order to analyze static and dynamic phenomena of semiconductor power devices or passive devices, and to support the design of power conversion systems, many circuit simulation models of semiconductor power devices such as GTOs, IGBTs, Thyristors are fabricated.In this paper, a reverse coducting static induction thyristor model is proposed. The model is made up of SI thyristor model with two transistor analogue and diode model with SPICE internal diode, capacitance and resistance. For confirming the accuracy of this circuit model, some experiments are carried out. As a result, good agreement are shown between the measured and calculated results.

Low loss static induction devices (transistors and thyristors)

To decrease the power loss, a current gain of a bipolar mode Static Induction Transistor (BSIT) is examined with quasi-one-dimensional analysis. The current gain dependence on source contact area is presented with experimental, analyzed and simulated results. Concerning Static Induction Thyristor (SIThy), the switching speed improvement methods are presented to reduce the switching loss of device. A proton irradiation, or a shorting method is a useful technique to decrease the switching time and switching loss of SIThy.

Fast high-voltage pulse generator with nonlinear transmission line for high repetition rate operation

A new application of the nonlinear transmission line (NLTL) for high-voltage pulse generation is reported. In this NLTL, a rise time of an input pulse voltage of 20-kV amplitude can be reduced from 500 to less than 120 ns. Using this circuit, we demonstrated excitation of a pulsed CO/sub 2/ laser, and obtained output energy of 129 mJ at an efficiency of 4.3%. Moreover, we find that the head-on collision of two solitons is quite effective to generate a high-voltage and short-width pulse. The input pulse is doubled in amplitude and sharpened in width, from 3.6 kV-300 ns to 11 kV-76 ns. With this method, the utilization of semiconductor devices such as the SI thyristor is possible as a primary switching device. Finally, a xenon lamp has been flashed at a repetition rate of 1 kHz.

Fast‐switching‐speed, low‐forward‐voltage‐drop static induction (SI) thyristor

AbstractA static induction (SI) thyristor using a normally‐off planar‐gate structure in a low power class has been developed to be used as a power switching device in a three‐phase inverter circuit. A 600 V‐15 A class SI thyristor with very fast switching time (tgt, tgq) and low forward voltage drop (VTM) was designed and created. This design was performed with a reasonable wafer structure (n−/n/p+), an n− base carrier concentration and thickness, and a gate structure (gate diffusion length and gate‐gate pitch). Microscopic processing was used to obtain this SI thyristor. The performance trade‐off between turn‐off time and forward voltage drop is controlled by a lifetime control process using proton irradiation that results in a very fast switching time with tgt of 500 ns and tgq of 500 ns with VTM of 1.5 V (at IT= 18 A). At a current level of IT = 18 A, the current density in the active area becomes 200 A/cm2, which indicates that the performance of the SI thyristor is superior to that of conventional IGBTs and MOSFETs.

Fast-Switching-Speed, Low-Forward-Voltage-Drop Static Induction(SI) Thyristor.

An SI thyristor using a normally-off planar-gate structure in a low power class has been developed for the use as a power switching device in a three-phase inverter circuit. A 600V-15A class SI thyristor with very fast switching time (tgt, tgq) and low forward voltage drop (VTM) was designed and fabricated. This design was performed with a reasonable wafer structure (n-/n/p+), an n- base carrier concentration and thickness, and a gate structure (gate diffusion length and gate pitch). Microscopic processing was used to obtain this SI thyristor. The performance trade-off between turn-off time and forward voltage drop is controlled by a life time control process using proton irradiation which results in a very fast switching time with tgt of 500ns and tgq of 500ns with VTM of 1.5V (at IT=18A). At the current level of IT=18A, the current density in the active area becomes 200A/cm2 which indicates that the performance of the SI thyristor is superior to that of conventional IGBTs and MOSFETs.

Improvement on the Performance of Static Induction(SI) Thyristor by Proton Irradiation.

The turn-off time (tgq), forward voltage drop (VTM) and the power dissipation at switching operation of static induction (SI) thyristor using a normally-off planer gate structure was improved by lifetime control using proton irradiation. In proton irradiation, defects form locally in silicon, and the depth of the defects distribution can be controlled by the energy of the proton beam.It has been found that the performance trade-off between tgq and VTM and the high temperature performance in the power dissipation of the SI thyristor depends on the depth of the defects formed by proton irradiation. If the defects were formed in the anode region then the power dissipation was nearly constant at from room temperature to 100°C.

Ultrasonic Butt Welding of Aluminum, Copper and Steel Plate Specimens

Characteristics of ultrasonic butt welding of the same and of different metal plates are studied. The ultrasonic vibration source used has eight 15-kHz bolt-clamped Langevin-type lead-zircon-titanate (PZT) transducers of 60 mm diameter and is driven by a 50-kW static induction thyristor power amplifier. Welding specimens of aluminum, copper and steel plates of 6 mm thickness are successfully joined end-to-end with weld strength almost equal to that of an aluminum specimen. The input power required for aluminum, aluminum and copper, and aluminum and steel plates are about 5 kW/cm2, 5.5 kW/cm2 and 3.5 kW/cm2, respectively. The measured temperature rise at the specimen side surface and elongation of the welded specimen during a tensile test correspond to weld strength. The hardness distributions along the weldment of welded specimens are measured and the maximum temperature rise in an aluminum welding specimen is estimated to be over 480°C from the reduction of hardness at a welding specimen surface.

Steady‐state characteristics of matrix converter

AbstractThe matrix converter proposed by Venturini is very simple in structure and has powerful controllability. However, there are few applications especially in power electronics fields. This seems to be caused mainly by the fact that such power devices that were fast enough to suppress ringing oscillations in the supply lines and large enough to pay for more devices and more complicated control circuits than in conventional dc‐link converter‐inverter systems were not available. At present, static induction thyristors (SIThs) have been introduced and a new possibility for the matrix converter has been raised.This paper describes a new control strategy which is simple and practical and allows the output voltage of 0.866 times the supply voltage to be generated. Also, the new firing sequences which eliminate voltage and current spikes are proposed. Steady‐state and distortion characteristics of the prototype PWM matrix converter with SITh are shown.

Electronic Chaos in Silicon Thyristor

Deterministic chaos was observed in the ac response of the Si thyristor in relation to its S-shaped negative differential conductivity. Period-doubling and period-adding chaotic sequences appeared in the same device corresponding to the change of operating parameters. A simple device/circuit model reproduced experimental Lorenz plots qualitatively.

Ultrasonic Butt Welding of Large Metal Plates by Shifting Welding Tip Driving Position

Ultrasonic butt welding of large metal plates by means of shifting the welding tip driving position at regular intervals is studied. The ultrasonic vibration source used has eight 15 kHz bolt-clamped Langevin-type lead-zircon-titanate (PZT) transducers of 60 mm diameter and is driven by a 50 kW static induction thyristor power amplifier. Aluminum plate specimens of 6 mm thickness and 100 mm to 400 mm width are joined successfully end-to-end with almost equal weld strength along the weldment. The input power required for aluminum plates is about 2.2 kW/cm2. The power required by one welding process for aluminum and copper plate specimens of 40 mm width is 4 kW/cm2.

Steady State Characteristics of PWM Matrix Converter.

The matrix converter Prof. Venturini proposed is very simple in structure and has powerful controllability. But, there are few applications especially in power electronics fields. This seems to be mainly caused by the fact that we didn't have such power devices that were fast enough to suppress ringing oscillations in the supply lines and big enough to pay for more devices and more complicated control circuits than in conventional DC-link converter-inverter systems. Now we've static induction thyristors (SIThs) and new possibility for the matrix converter is opened for us.In this paper, we describe the new control strategy which is simple and practical and allows to generate the output voltage of 0.866 times the supply voltage. We also propose the new firing sequences which eliminate voltage and current spikes. Steady state and distortion characteristics of the prototype PWM matrix converter with SITh are shown in the paper.

A circuit simulator of the SITh

A classification of circuit simulators is provided and the techniques used in these simulators to cater to requirements for the static induction thyristor (SITh) are examined. A circuit simulator expressly for the SITh is reported. Circuit equations implicitly containing two-dimensional (2-D) physical device equations are computed by the Newton-Raphson method. The incompletely rectangular mesh structure of M.S. Adler (1978) is modified to conveniently handle current equations at an arbitrary state. Terminal currents are precisely computed by counting displacement currents that have not been simulated but are experimentally known to be important. The model includes the crystal orientation of the wafer. The simulation makes clear how to design gate doping and control the gate during on-states to improve forward voltage drop without violating forward-blocking capability. Simulation of the turn-off state proves the reliability of the circuit simulator physically as well as mathematically.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Evaluation of modern power semiconductor devices and future trends of converters

A review of the modern power semiconductor devices that appeared in the 1980s, i.e., the insulated gate bipolar transistor (IGBT), the static induction transistor (SIT), the static induction thyristor (SITH), and the MOS-controlled thyristor (MCT) is presented. The characteristics of these devices are discussed and compared from the viewpoint of power electronics applications. Although the IGBT is well known, the power electronics community is somewhat unfamiliar with the latter three devices. For completeness, a brief review of other power devices, such as the thyristor, the triac, the gate turnoff thyristor (GTO), the bipolar junction transistor (BJT), and the power MOSFET, is also incorporated. Finally, future converter trends are outlined. >

EPITAXIAL SILICON GROWTH BY RAPID THERMAL CVD

A rapid thermal chemical vapour deposition system has been used for the growth of epitaxial silicon layers on silicon substrates in the temperature range 590°C 1000°C. Low pressure deposition schedules have been found essential in order to minimise the concentrations of oxygen and carbon in the layers. In-situ pre-cleaning schedules have been established to remove oxide layers from the substrates prior to layer deposition. The application of these deposited epitaxial layers to the production of a buried gate static induction thyristor is described. The deposition of polycrystalline silicon and the growth of epitaxial silicon are vital steps in advanced integrated circuit processes. The technique in almost universal use for the production of these films is chemical vapour deposition (CVD), wherein gaseous species (eg SiH4, SiH2C12) react on a substrate and a solid phase material (silicon) is produced. Both polysilicon and epitaxial silicon have traditionally been produced in atmospheric pressure reactors. However, in the case of polysilicon, low pressure reactors have largely taken over because of improved uniformity and reduced gas consumption. Reduced pressures are also beneficial for the growth of epitaxial silicon, as autodoping and pattern shift effects are alleviated [l] and homogeneous gas phase nucleation of silane is retarded [ Z ] . Low pressure (LP) CVD is thus, becoming the most technologically important means of producing silicon films. Recently, much attention has been given to a refinement of LPCVD which incorporates the concept of rapid thermal processing (RTP). In RTP, the single process wafer is heated by a high-intensity light source, and very fast ramp rates can be achieved. The combination of LPCVD and RTP is known as rapid thermal chemical vapour deposition (RTCVD). In particular, when reactions are triggered by a temperature pulse (rather than by gas switching), the technique has been termed limited reaction processing (LRP) 1 3 1 . Rapid thermal processes have the advantage of a reduced thermal budget, as the fast ramp rates minimize the time for which the wafer is at elevated temperatures. This is an important consideration for high-speed VLSI circuitry, where lateral and vertical device dimensions must be tightly controlled. Because RTP minimises unwanted dopant diffusion, shallow junctions of high quality are more readily obtained by this technique than by traditional furnace methods. The ability to switch temperatures rapidly also means that several different process steps can be carried out sequentially in-situ. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jp4:1991291 C2-780 JOURNAL DE PHYSIQUE IV LRP shares the advantages of RTP, and may be used to deposit a sequence of thin, highly abrupt semiconducting layers. Applications include shallow emitter-base structures for heterojunction bipolar transistors [4, 53 and superlattices [ 6 ] , and buried p ' grid structures for advanced static induction thyristors. This paper will describe a twin reactor system used for the production of epitaxial silicon layers for device manufacture. One of the reactors has been dedicated to high temperature epitaxy from SiH2C12 and the other to low temperature epitaxy from SiH,,. The requirements and properties of the two processes will be contrasted.