Inverter light triggered thyristor with unique arm-structure amplifying gate

A 1200-V 200-A directly light triggered thyristor suitable for inverter application has been developed. A new amplifying gate design with a second amplifying stage was used in achieving a factor of 15 to 50 increase in gate sensitivity without any loss indV/dtcapability and only a small (less than a factor of two) reduction in devicedi/dtrating, despite a ten times smaller initial turn-on line length. In all, three versions were made with gate threshold currents down to 1 mA anddV/dtcapabilities to 1000 V/µs. All three types had 60-Hz di/dt capabilitLes of about 250 A/µs at 125 deg TJand turn-off times of approximately 25 µs. The new light sensitive amplifying gate stage design features a gate thyristor region with extending arms for high gate sensitivity, the inner portion of which is just large enough to accommodate initial on-region spreading duriag the short on-time of the gate stage. The arms increase gate sensitivity while contributing very little to the overalldV/dtcurrent. The turn-on speed can be accounted for by most of the inner region being turned on by the photogate pulse. Like regular electrically fired thyristors, a gate overdrive factor is important. With these devices an overdrive factor of about 3 to 5 is needed for highdi/dtturn-on whereas in an electrically triggered device this factor is closer to 10.     

High dI/dT light-triggered thyristors

Directly light-triggered, 4000- and 6000-V thyristors were designed, fabricated, and tested to obtain high performance in dI/dt, dV/dt, and photosensitivity. Built-in resistors protected both auxiliary stages during high dI/dt turn-on. The novel use of etched moats to define the resistors was compatible with an optical gate structure that gives high dV/dt and good photosensitivity. No additional processing steps were needed to fabricate these devices, as compared to standard light-triggered thyristors. A record value of 1000 A/µs at 60 Hz was measured on a 6000-V thyristor, and 850 A/µs was safely triggered with only 1.8 mW of light. The dV/dt immunity of the photogate structure measured 4000 V/µs, rising exponentially to 80 percent of 4000 V, VDRM. Thyristors triggered by dV/dt were not destroyed. A new model of resistor heating was combined with the first measurements of the current pulses through both built-in resistors to identify the mechanism responsible for occasional burn-out of the second resistor. The failure mechanism was conductivity modulation in the surface of the resistor during its microsecond on-time caused by thermally generated carriers. The test results confirmed the utility of built-in resistors for high dI/dt performance with minimal light power and for nondestructive dV/dt triggering.     

Development of a 2.6-kV light-triggered thyristor for electric power systems

The status of a present Electric Power Research Institute, Inc. (EPRI) funded research program on a directly light-triggered thyristor for high-voltage direct current (HVDC) application is reviewed. An existing 53-mm, 2600-V, 1000-A electrically fired device was suitably modified to be turned on with an incident photopulse of 30 nJ, the basic problem being the retension of a 2000-V/µsdV/dtcapability. Design tradeoffs betweendV/dtand gate sensitivity are discussed as well asdi/dtproblems encountered in turning on a 2-in device with such a small gate signal. Special experiments and design and analysis computer programs have helped in assessing temperature excursion during turn-on and led to improved design with adi/dtcapability approaching that of the original electrically gated device.     

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.     

Simulated turn-off of 4H-SiC gate turn-off thyristors with gateelectrodes on the p-base or the n-base

Turn-off simulations of a 4H-SiC GTO thyristor structure having a gated p-base and p-type substrate are compared with that having a gated n-base and n-type substrate. Two gate drive circuits are considered, one with a voltage source and resistor between the gate and adjacent emitter region, and the other with a voltage source and resistor between the gate and farthest emitter region. The gated n-base thyristor's substrate current increases atypically before the device turns off. Also, the gated n-base structure turns off when the gate circuit is connected directly to the emitter region furthest from the gate region, but the gated p-base structure does not. Furthermore, turn-off gain is lower for the gated n-base structure due to mobility differences as demonstrated by current-voltage (I-V) and current versus time (I-t) curves     

An emitter switched thyristor with base resistance control

An MOS-gated emitter-switched thyristor structure with base resistance control, which combines the best features of both the emitter-switched thyristor (EST) and the base-resistance-controlled thyristor (BRT), is reported. With this structure, it is possible to obtain turn-off (dynamic) current densities above the static latch-up current density of the parasitic thyristor in the EST, while preserving its unique current saturation capability. It has been experimentally demonstrated for 600 V forward blocking devices that the maximum controllable current density under dynamic conditions is a function of both the gate bias and the dimensions of the N⁺ floating emitter. Turn-off measurements have demonstrated that the new structure has a maximum controllable current density of over 2.5 times that for the EST structure without base resistance control     

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.     

Numerical simulation of an optoelectronic thyristor in the regime of incomplete turn-off

Direct two-dimensional simulations are used to analyse the possibility of controlling the carrier concentration in the gated base of a GaAs optoelectronic thyristor, which operates in the regime of incomplete turn-off. Modelling results indicate that the number of carriers, light intensity, current distribution, and the position of the light-emitting region the gated base of the thyristor can effectively be changed using gate currents, insufficient to turn the device completely off. The utilization of incomplete turn-off principle can be used for light-intensity modulation and switching purposes.     

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.     

Theoretical and experimental characteristics of the base resistancecontrolled thyristor (BRT)

Described are the characteristics of a new MOS gated thyristor structure called the base resistance controlled thyristor (BRT), in which the turn-off of a thyristor built with an N drift region is achieved by reducing the resistance of the p-base region under MOS gate control. A p-channel MOSFET used to achieve turn-off is formed in the N drift region. The device is designed so that, when the p-channel MOSFET is switched on, holes are diverted from the p-base region of the thyristor into the adjacent p⁺ region, raising the holding current of the thyristor above the operating current level, and turning off the thyristor. Results of extensive 2-D numerical simulations that have been performed to demonstrate operation of this new device concept are discussed. Experimental results on 600-V devices fabricated with an IGBT process have corroborated theoretical predictions. Current densities above 900 A/cm² have been turned off at room temperature with a gate bias of -10 V     

Method of rapid numerical calculation of transient processes in a thyristor

A method is proposed for the rapid numerical calculation (less than 0.5 min with an IBM 370 computer) of thyristor behaviour during transient operation. The dV/dt blocking capability, the gate triggering and the anode-current turnoff are simulated. The results obtained are compared with experimental results.     

A Novel 4.5$hbox{F}^{2}$ Capacitorless Semiconductor Memory Device

This letter proposes a novel 4.5$hbox{F}^{2}$ capacitorless dynamic random access memory cell with a floating gate (FG) connected to drain via a gated p-n junction diode. The FG in the proposed memory device is for charge storage and can electrically be charged or discharged by current flowing through a gated p-n junction diode.      

The di/dt capability of thyristors

This paper describes an experimental investigation of the di/dt failure mechanism of thyristors. The location of the initial turn-on region and the spread of the "on" region were observed on a specially designed thyristor having many monitoring electrodes. The turn-on process was studied for triggering by gate, by breakover, and by dv/dt. In many cases it was found that turn-on occurred at almost the same region, whether it was triggered by breakover or by dv/dt. This area coincided with the final holding position in the turn-off process. The di/dt capability of the thyristor was measured. It was found that the capabilities were almost the same for the three triggering methods. The destruction temperature in the di/dt test was estimated from the area of the burn-out spots and the energy dissipation.     

高压高阻断增益的水平沟道场控晶闸管

水平沟道场控晶闸管(简称LFCT)是由垂直沟道场控晶闸管发展而来的,它具有开关速度快、与集成电路工艺兼容等特点。我们采用刻蚀V型槽来代替栅扩散,已制成最大正向阻断电压为200V,可关断电流为2A的LFCT,其正向电压阻断增益达40～200。     

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.     

Comparison of light triggered and electrically triggered thyristor turn-on

As part of an EPRI (Electric Power Research Institute) funded research program on a directly light triggered (LT) thyristor for HV dc application, an existing 53-mm 2600-V 1000-A electrically fired device was suitably modified to be turned on with an incident photo-pulse of 20 nJ, the basic problem being the retention of a 2000 V/µsdV/dtcapability. The price paid for high sensitivity and highdV/dtcapability was found to be a device inherently more susceptible todV/dtfailure. In the efforts to cope with this problem a number of computer-type models were developed to assist in predicting turn-on in both electrically and light fired devices with one or more amplifying stages. At the same time, devices were fabricated which could be either light or electrically fired. Both the model and experiment point to faster turn-on of the light fired device and an increased requirement for careful design.     

光控MOS栅固态继电器的电路分析与模拟

光控MOS栅固态继电器是由MOS栅控晶闸管、开关三极管、光电耦合器、增强型MOSFET和齐纳二极管组成的新型开关器件。文章提出了光控MOS栅固态继电器的电路结构，详细分析了它的工作原理及其光电特性。     

High-voltage high-power gate-assisted turn-off thyristor for high-frequency use

The fast switching thyristor with an integrated rectifier-diode connected in antiparallel to the cathode-emitter junction of auxiliary thyristor has been made. This thyristor has the ratings of blocking voltage 1200 V, average current 400 A. The turn-off time of less than 6 µs can be obtained by applying -10 V gate bias. It has the interdigitated gate structure and the high-frequency current rating more than 500 A at 10 kHz.     

Photo-sensitive characteristics of negative resistance turn-around occurring in SIPTH

Influences of light irradiation on the negative resistance turn-around characteristics of static induction photosensitive thyristor(SIPTH)have been experimentally and theoretically studied.As the gate current of SIPTH is increased by the light irradiation,the potential barrier in the channel is reduced due to the increase in voltage drop across the gate series resistance.Therefore.SIPTH Can be quickly switched from the blocking state to the conducting state by relatively low anode voltage.The optimal matching relation for controlling anode conducting voltage of SIPTH by light irradiation has also been represented.