Improvement of thyristor turn-on by calculation of the gate-cathode characteristic before injection

The ohmic part of the gate-cathode characteristic of thyristors has been calculated numerically. Normal and amplifying gate structures as well as emitter shorts are included. By a simple extension of the model, the case of the dv/dt and breakover turn-on has also been treated. It is thus possible to calculate the minimal control current and voltage for a cathode side thyristor geometry and to optimize the device with respect to the turn-on process.     

Progress in light activated power thyristors

Light activated power thyristors would have considerable advantages in intermediate- and high-voltage circuits, as power and trigger circuits could be electrically separated by use of glass fiber cables. Besides high-voltage capability, such devices must have turn-on delay times, dv/dt capabilities, and di/dt stabilities which are comparable to conventionally fired thyristors. The necessary trigger power, however, has to be kept low enough to enable firing with GaAs light emitters, which are available now or will be in the near future. The dv/dt sensitivity is an essential limitation for the reduction of the minimum necessary trigger power. Optimizing of the thyristor emitter shunts results in an already acceptable compromise, but much better results can be obtained by a gate structure which actively compensates dv/dt fault triggering. Our test devices show good turn-on behavior. A short survey on different GaAs-light sources and the coupling problem is given.     

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     

Behavior of thyristors under transient conditions

The capability of gate-triggered thyristors to withstand steep wavefront, high-current pulses (i.e., di/dt capability) is a function of both junction temperature and frequency of operation. Localized internal heating occurs during turn-on and may lead to thermal runaway. The conditions required for this to occur have been determined by destructively testing many devices. The initial conducting area of a thyristor largely determines di/dt capability, which is not necessarily related to the size of the device but is a function of the design of the gate region. Gate drive is very important for determining the di/dt capability of a thyristor having a conventional gate design. Two devices which have been designed to increase the initial conducting area are discussed. One of these devices, if improperly designed, can lose its effectiveness with high gate drive. This characteristic can be studied by observing the reverse recovery current immediately following short forward current pulses.     

A high-current and high-temperature 6H-SiC thyristor

A 6H-SiC thyristor has been fabricated and characterized. A forward breakover voltage close to 100 V and a pulse switched current density of 5200 A/cm² have been demonstrated. The thyristor is shown to operate under pulse gate triggering for turn-on and turn-off, with a rise time of 43 ns and a fall time of less than 100 ns. The forward breakover voltage is found to decrease by only 4% when the operating temperature is increased from room temperature to 300°C. It is found that anode ohmic contact resistance dominates the device forward drop at high current densities     

Low-loss high-speed switching devices, 2300-V 150-A static induction thyristor

Focussing attention to the performance of high-speed high off-state voltage and large current provided in the buried-gate-type static induction (SI) thyristor, a 2300-V 150-A low-voltage-drop high-speed medium-power SI thyristor was developed. Irrespective of the magnitude of switching current, the SI thyristor has the characteristics of fast turn-on time and less on-gate current compared to that of the GTO thyristor. The characteristics of this SI thyristor obtained as the result of manufacturing this prototype were such that the forward blocking voltage was 2300 V at a gate reverse voltage of -5 V, the reverse blocking voltage was 2350 V, and the forward voltage drop was 1.4 V at an anode current of 150 A and 2.2 V at an anode current of 450 A. The switching characteristics were such that the turn-on time was 1.5 µs when an anode current IAof 150 A becomes ON, turnoff time was 2.5 µs at IA= 100 A and 3.6 µs at IA= 200 A. This SI thyristor is able to break the anode current of 1000 A at a gate current of 95 A. Performance exceeding 1100 A/µs was confirmed for the di/dt capability and even for dv/dt, and these normally can be operatable even at 100 times higher current compared with maximum average current.     

Power Converter EMI Analysis Including IGBT Nonlinear Switching Transient Model

It is well known that very high dv/dt and di/dt during the switching instant is the major high-frequency electromagnetic interference (EMI) source. This paper proposes an improved and simplified EMI-modeling method considering the insulated gate bipolar transistor switching-behavior model. The device turn-on and turn-off dynamics are investigated by dividing the nonlinear transition by several stages. The real device switching voltage and current are approximated by piecewise linear lines and expressed using multiple dv/dt and di/dt superposition. The derived EMI spectra suggest that the high-frequency noise is modeled with an acceptable accuracy. The proposed methodology is verified by experimental results using a dc-dc buck converter     

金属氧化物半导体控制晶闸管的di/dt优化

金属氧化物半导体控制晶闸管(MCT)相比于绝缘栅双极型晶体管(IGBT)具有高电流密度、低导通压降和快速开启等优势,在高压脉冲功率领域具有广阔的应用前景.作为脉冲功率开关,MCT开启过程对输出脉冲信号质量有很大影响.采用理论分析并结合仿真优化重点研究了MCT开启瞬态特性.通过对MCT开启过程进行详细地理论分析推导,给出了MCT开启过程中阳极电流和上升时间的表达式.结合Sentaurus TCAD仿真优化,将MCT开启过程中电流上升速率(di/dt)由40 kA/s提升至80 kA/s,极大地改善了器件开启瞬态特性.最后,总结提出了提高器件开启瞬间di/dt的设计途径.     

A thyristor protected against di/dt failure at breakover turn-on

The principle and the operation of a thyristor that can be turned on by exceeding its breakover voltage are described. The principle uses the concept of an auxiliary thyristor amplifying the small breakover current to a large gate current for the main thyristor. In this arrangement the breakover turn-on has to occur first in the auxiliary thyristor. This is ensured by a doping of the n-base of the auxiliary thyristor which is higher than that of the n-base of the main thyristor. Time resolved infrared photographs of the breakover turn-on are presented. Also, infrared photographs of the breakdown radiation from p-n-p structures are used to give a survey on the starting silicon which already contains the inhomogeneous doping.     

An optically-coupled crosspoint array with high dv/dt capability and high gate sensitivity

A 2/spl times/4 optically-coupled economical crosspoint array for the telephone speech path with a high breakover voltage (>450 V), high dv/dt capability (>200 V/0.1 /spl mu/s), and high gate sensitivity (<5 mA) is described. This has been achieved by a new device structure with a double-gate MOSFET and RC discharge circuitry formed on a p-n-p-n element. This MOS associated circuitry for dv/dt improvement is referred to as `MAC' p-n-p-n elements with MAC can be separated from each other with a new simple isolation technique called `canal isolation' which facilitates low manufacturing cost. Both p-n-p-n elements and LEDs are bonded face-down on a 44 pin chip carrier ceramic package with bump electrodes which again allows low manufacturing cost. The MAC enables independent control of the dv/dt capability and the gate sensitivity. The authors show the MAC performance in dv/dt improvement and various evaluations of MAC, including computer simulation. High breakover voltage technology and some processes for forming the gate-to-cathode resistor R/SUB GK/ for devices with MAC are discussed. This new optically-coupled crosspoint array with MAC makes possible a high-performance direct interface with conventional telephone sets.     

Zero-current and zero-voltage soft-transition commutation cell for PWM inverters

This paper presents a universal auxiliary commutation cell for pulse-width modulated (PWM) inverters termed zero current and zero voltage transition (ZCZVT) commutation cell. It provides zero current and zero voltage commutation, simultaneously, during main power devices turn-on and turn-off, with controlled di/dt and dv/dt. As a result, commutations of the main power devices occur without any losses. This unique characteristic is not achieved by any other soft-switching commutation cell for inverters hitherto presented in the literature, making it a strong candidate for use in low-power (MOSFET), medium-power (IGBT) or high-power applications (GTO, thyristor). Furthermore, reverse recovery losses of main diodes are minimized and auxiliary switches commutate at zero current. To demonstrate the operation of the proposed universal auxiliary commutation cell, a ZCZVT PWM full-bridge inverter is analyzed. To evaluate the operation of the auxiliary circuit in different conditions, prototypes with both IGBTs and MOSFETs for different output powers levels were implemented and their performances compared. Experimental results confirm that there is no overlap between main switch current and voltage, and that waveform ringing is practically eliminated.     

Switching dynamics of IGBTs in soft-switching converters

Next generation of power semiconductor devices will be designed and optimized to meet the specific application requirements. Mixed-mode simulations are used to study the carrier dynamics in punch-through and nonpunch-through Insulated Gate Bipolar Transistor (IGBT) structures during soft- and hard-switching conditions. The simulation results are shown to qualitatively predict the measured bump in the tail current with varying output dv/dt conditions and excessive forward conduction voltage under varying di/dt conditions. A new physical effect termed “conductivity modulation lag” is shown to occur during turn-on under soft-switching conditions. This mechanism is caused by the fact that minority carrier injection into the base of the bipolar transistor significantly lags behind the rate at which drift region conductivity can be modulated. The proposed phenomenon leads to an inductive effect that results in dynamic voltage saturation during turn-on and causes excessive forward voltage drop     

DV/DT related spurious gate turn-on of bidirectional switches in a high-frequency cycloconverter

We identified a failure mode in a two stage dc/ac converter, comprising a high-frequency dc/ac inverter followed by an ac/ac cycloconverter, both operating at the same switching frequency. The failure-mode is a short-circuit condition, which is a combined effect of the reverse recovery of the MOSFET body diode and simultaneous spurious turn-on of the bidirectional switches of the cycloconverter, owing to a significantly high dv/dt (>2/spl times/10/sup 8/V/ns). A high dv/dt causes appreciable current to flow through the gate-to-drain (Miller) capacitance, thereby producing a significant amount of voltage drop across the external gate resistance. Consequently, the gate-to-source voltage of the power MOSFET may exceed the threshold voltage of the device, which turns the device on. We explain the mechanism for the dv/dt-related gate turn-on and present experimental results to validate the explanation. We also demonstrate, how a two-fold increase in the value of external gate resistance of the inverter switches (to reduce the dv/dt applied to the cycloconverter) reduces the periodicity of the short-circuit condition.     

An optically-coupled high-voltage p-n-p-n crosspoint array

A solid-state crosspoint array compatible with electromechanical switches has been developed in order to realize high-performance telephone exchange networks. The optically-coupled high breakover voltage crosspoint array discussed in this paper has achieved complete isolation of the speech path from the triggering circuit while it can be triggered directly by a transistor-transistor logic (TTL) level signal from the control circuit. The crosspoint array has a unique photo-coupling structure which allows four p-n-p-n elements to be triggered effectively by only one LED, maintaining up to 200 V/0.1 /spl mu/s dv/dt characteristics. It provides breakover voltage of up to 450 V, gate trigger LED current less than 20 mA, ON-state resistance within 4.5 /spl Omega/ and OFF-state capacitance less than 7 pF. The matrix arrangement is a 1/spl times/4 configuration; it is composed of a two wire bidirectional circuit and packaged in a 16-pin ceramic DIP. These device characteristics make possible the realization of solid-state crosspoint array practically compatible with the conventional electromechanical switch, particularly meeting requirements of miniaturization, low-power dissipation, and inexpensive construction. Accordingly, direct interface with conventional telephone sets is possible.     

级联式Buck-Boost校正电路在高压电子镇流器中的应用

本文提出了一种带有无源无损缓冲结构的级联式buck-boost校正电路,并成功地应用在高压式电子镇流器中.缓冲电路通过抑制反向恢复电流所引起的di/dt和漏源极电压的dv/dt,有效地减少了开关损耗和EMI噪音.Buck电路中的IGBT实现零电流开通和零电压关断,同时续流二极管也工作在零电压状态.研制的380 V交流输入,400 V直流输出,额定功率600W的实验样机,其功率因数达0.98,THD小于11%.     

Controlled turn-on thyristors

In a one or more amplified stage thyristor design it is possible to control the peak current level of all but the final stage with impedance built into the p-base zone. This impedance reduces both the current and the duty cycle of the protected amplifying stage effectively protecting it from undesirable temperature rises during turn-on. A further bonus and perhaps equally important is the fact that the amplifying stage and its current control impedance can be used to reduce and essentially fix the voltage level at which the following stage turns on. This results in a lower voltage, lower stress turn-on of the following stage, and a device essentially protected from di/dt turn-on failure. This paper describes several aspects of controlled turn-on in the context of a 2.6- and 6-kV light triggered thyristor. In particular we discuss selection of the resistor value, the problem of unwanted current control resistor modulation by device current as well as some factors affecting the proper wattage of such resistors. We also discuss the role current control resistors can play in controlling avalanche current from known locations on the device.     

提高晶闸管器件对di/dt的耐受能力的途径

介绍了晶闸管器件的通态电流上升率di/dt参数及其损坏晶闸管器件的机理，并进一步介绍了提高晶闸管器件的通态di/dt耐量的设计和工艺方法，及应用过程中限制晶闸管阳极电路的电流上升率，保护晶闸管器件的方法。     

An overvoltage self-protected thyristor with a structure to predictbreakover voltage

A new concept for an overvoltage self-protected thyristor was theoretically analyzed and the thyristor manufactured. Its breakover operation is basically a combination of punchthrough and avalanche phenomena. Temperature dependence of the original structure in this thyristor is 5% from 20 to 125°C. A second device which has a function to predict breakover voltage was also produced. The difference in temperature dependence of breakover voltage for both devices was investigated by an analytical model. Structures offering improved characteristics were proposed. The breakover voltage decrease of the developed structures at high temperature could be made equal to that of the original structure by a slight modification of the breakover region     

High-power dual amplifying gate light triggered thyristors

The feasibility of directly light triggering a high power phase control thyristor is investigated. Work is described on an optically triggered gated 53-mm diameter 2600-V 1000-A thyristor which is similar to an electrically gated production version. Test results describing the response of this thyristor to various optical signals are presented. Our work has shown that this cell can be directly triggered by light at an equivalent gate current which is a factor of three below its present dynamic gate requirements and still largely retain all its blocking and dynamic characteristics. This improvement is obtained by the use of a second very sensitive amplifying gate stage which is responsive to light. All wafer processing of the light sensitive thyristor was carried out on standard production lines. Tests made on static dV/dt, di/dt, blocking voltage, and leakage current on light sensitive devices all closely match parameters of the standard electrically fired equivalent cell.     

Multiple Slope Switching Waveform Approximation to Improve Conducted EMI Spectral Analysis of Power Converters

An improved and simplified electromagnetic interference (EMI) modeling method based on multiple slope approximation of device-switching transitions for EMI analysis of power converters is presented. The traditional noise source modeling method, which uses single slope for rise and fall transition, is studied, and the criteria for reasonable modeling in the frequency range is analyzed. The turn-on and turn-off dynamics are investigated by dividing the nonlinear transitions into several stages based on an insulated gate bipolar transistor (IGBT) behavior circuit model. Real device-switching voltage and current waveforms are approximated by piece-wise linear lines and modeled by multiple dv/dt and di/dt slopes. The predicted EMI spectra suggest that high-frequency EMI noise is modeled with an acceptable accuracy. The proposed method was verified experimentally for a dc-dc buck converter