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Large inrush currents can be harmful to equipment subjected to it and can also disturb other devices through voltage dips. Traditional ways of dealing with large inrush currents include the usage of parasitic elements in the supply, negative temperature coefficient (NTC) resistances and start-up relays. These solutions have several disadvantages among which are a non-negligible standby consumption, using a relay or a compromise between inrush current and load losses using an NTC. This paper proposes a solution which solves these disadvantages. The proposed circuit uses a semi-controlled bridge rectifier requiring a very low standby power consumption and is capable of withstanding grid interruptions. Moreover, it is designed to power on only when the load is not too heavy. This is accomplished by the use of positive temperature coefficient thermistors. The presented solution can be used for DC-link start-up circuits in applications with a power range from several watts up to a few kilowatts and it is particularly suitable for on-board battery chargers designed for electrical vehicles. [ABSTRACT FROM AUTHOR]

The omnipotent Li–ion battery charger with multimode control and polarity reversible techniques is presented in this article. The proposed chip is fabricated with TSMC 0.35μm 2P4M complementary metal-oxide- semiconductor processes, and the chip area including pads is 1.5 × 1.5 mm2. The structure of the omnipotent charger combines three charging modes and polarity reversible techniques, which adapt to any Li–ion batteries. The three reversible Li–ion battery charging modes, including trickle-current charging, large-current charging and constant-voltage charging, can charge in matching polarities or opposite polarities. The proposed circuit has a maximum charging current of 300 mA and the input voltage of the proposed circuit is set to 4.5 V. The maximum efficiency of the proposed charger is about 91% and its average efficiency is 74.8%. The omnipotent charger can precisely provide the charging current to the battery. [ABSTRACT FROM PUBLISHER]

This paper proposes a robust and simple direct power control (DPC) of a thyristor-based current-fed drive for generator applications. A current-fed drive and permanent magnet-assisted synchronous reluctance generator (PMa-SynRG) are investigated to deliver 3 kW power using a combustion engine. The current-fed drive utilises a thyristor-based three-phase rectifier to convert generator power to DC-link power and a single-phase current-fed inverter to supply a single-phase inductive load. In addition, a new control algorithm is developed based on DPC for the current-fed drive. The DC-link voltage-based DPC is proposed in order to directly control the output power. The goal of the DPC is to maintain the DC-link voltage at the required output power operating point. The DPC has advantages such as a simple algorithm for constant speed operation. Another feature of the developed current-fed drive is its inherent capability to provide generating action by making the PMa-SynRG operates as a generator, rectifying the phase voltages by means of the three-phase rectifier and feeding the power into the load. These features make the current-fed drive a good candidate for driving any type of synchronous generators including the proposed PMa-SynRG. [ABSTRACT FROM AUTHOR]

This article presents a grid-connected photovoltaic (PV) system using the classical DC-DC buck converter, which is responsible for stepping down the resulting voltage from several series-connected panels. Besides, the structure provides high power factor operation by injecting a quasi-sinusoidal current into the grid, with near no displacement in relation to the line voltage at the point of common coupling among the PV system and the loads. A CSI employing thyristors is cascaded with the DC-DC stage so that AC voltage results. The inverter output voltage level is adjusted by using a low-frequency transformer, which also provides galvanic isolation. The proposed system is described as mathematical approach and design guidelines are presented, providing an overview of the topology. An experimental prototype is also implemented, and relevant results to validate the proposal are discussed. [ABSTRACT FROM AUTHOR]

This paper describes the construction of new circuit configurations for some sequential circuits. These circuits are based on the microthyristor as a microelectronic bistable device that can store logic one and logic zero and on NMOS transistors that act either as pass transistors or drivers. The shift register, considered as a main type of sequential circuit, is developed from a D flip-flop that is designed basically from the microthyristor as a bistable device. Moreover, different types of counters based on the microthyristor as a storing element are developed. Microthyristor sequential circuits were found to perform well. [ABSTRACT FROM AUTHOR]

This paper describes the development of new configurations for flip-flops which are based on a microthyristor as a storage element, the NMOS transistor as a series switch or a driver and a high pull-up resistor. The performance of these flip-flops is analysed, using a PSPICE simulator. These devices perform well with regard to speed and power consumption and are more compact because of the use of the microthyrister. [ABSTRACT FROM AUTHOR]

A novel and versatile test-and-drive circuit for gate turnoff (GTO) thyristors is described in detail. The developed low-cost and reliable electronic control circuit was employed in the characterization and dynamic evaluation of the recently reported double-interdigitated (TIL) GTO thyristors. The circuit, which combines simplicity with versatility, could be employed in the drive of GTOs in those particular applications where the pulse-width modulation (PWM) inverter is a key element in a network supplying power to resistive-inductive or inductive loads (motor speed control systems, switched-mode power supplies, horizontal TV deflection systems, etc.). A distinctive feature of the developed circuit is that the gate of the GTOs is controlled during turn-on and turn-off by current signals, which is an important aspect when (a) the gate-cathode breakdown voltage of the GTOs is relatively low and (b) the exact determination of the turn-off gain K[sub off] of the GTOs is one of the objectives. A remarkable feature of the drive circuit is that each gate current parameter during both turn-on and turn-off of the GTOs (pulse amplitude and width, rate of gate current rise, repetition frequency) can easily be controlled independently over a wide range. The switching duty cycle is also adjustable over a wide range. [ABSTRACT FROM AUTHOR]

The paper describes the effects of changes in the triggering frequency on the maximum working frequency of a series inverter. Inverters differ in the type of load and in the mutual coupling existing between two commutation inductors in the circuit. It has been shown that the transient state is a result of changes in thyristor commutation from natural or critical to overlapping, and is dependent on the mode of change of the triggering frequency. The region of overlapping commutation has been determined by using two types of frequency change: fast (by keying modulation) and slow (by frequency modulation). The results show that slow changes in thyristor commutation permit a higher maximum working frequency than do fast changes. The region of overlapping commutation of thyristors is defined by new limit curves. The results may, for example, be applied in the design of an ultrasonic generator operating with frequency modulation. [ABSTRACT FROM AUTHOR]

The paper focuses on the peculiar dynamic behaviour of the recently developed 8mm², TO-220-packaged, high-voltage, double-interdigitated (or two interdigitation levels—TIL) GTO thyristor. This novel power device was rated under both slightly and heavily inductive resistive loads, i.e. close to the real conditions encountered in practical power circuits employing GTO thyristors. Emphasis is laid on the ability of TIL GTOs to switch safely, with minimum power losses, a certain amount of anode current under high-voltage conditions and high commutation frequencies. The merits of TIL GTO thyristors are analysed in terms of their reliability and switching efficiency, which include the total power losses (conduction and switching losses), turn-on and turn-off gains and the switching speed. It is shown that thanks to their built-in self-protective features, these novel GTOs possess an enhanced current-handling capability at commutation frequencies up to 50 kHz under extremely tough load conditions. The main implications of the results for power applications are outlined. [ABSTRACT FROM AUTHOR]

Development of a sequential machine model of a thyristor considering ‘turn-on’ and ‘turn-off’ time of the device is presented. A model of a thyristor along with the snubber circuit is also developed. The models are used to illustrate the operation of a thyristor chopper where the thyristors are protected by snubbers. The model is useful in analysis and design of circuits employing a number of thyristors. [ABSTRACT FROM AUTHOR]

The paper presents the results of theoretical analysis as well as numerical calculations of the maximum output frequency in a series inverter working with overlapping commutation of the thyristors. The changes from natural or critical thyristor commutation to overlapping commutation were fast. The region of overlapping commutation is limited by new extreme curves which ave dependent on the type of load as well as on the mutual coupling value between the two commutation inductors. Resonance shaping load-current edges have also been considered in this paper. [ABSTRACT FROM AUTHOR]

A novel coupled-inductor commutation circuit is described. The circuit may also be used for inverters. It uses only two auxiliary thyristors, each operating in alternate cycles and eliminating the need for reversal of the commutating capacitor voltage. Trapped energy is fed back to the source. The output voltage is controllable from zero to the full input voltage. The commutation circuit can be connected to a voltage source other than that feeding the load. A DC chopper using this commutation scheme has been analysed and experimentally verified. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical simulation of a DC chopper circuit has been made by considering the thyristor as a unit step function multiplied with the applied voltage. The wave pattern of the output current and voltage developed across the associated load have been plotted utilizing the results. [ABSTRACT FROM AUTHOR]

A McMurray commutation circuit with a (di/dt) inductor in series with the main thyristors is analysed. Analysis shows that advanced firing on the commutation current ring is necessary in order to avoid the commutation failure in case of sudden loading of the inverter. Advanced firing boosts the commutation capacitor voltage. Hence, the operating conditions should be adjusted so as to control the commutation capacitor voltage in a narrow range from no-load to full-load conditions. At the same time, the commutation energy corresponding to these conditions should not deviate much from the minimum commutation energy. [ABSTRACT FROM AUTHOR]

This paper derives simple equations to determine the effects of the reverse recovery time and stray inductance on the available reverse bias time of the main thyristor to guarantee the commutation of the main thyristor. These effects are illustrated by an example of a practical chopper circuit. [ABSTRACT FROM AUTHOR]

In the present paper, an equivalent circuit of the thyristor has been developed considering it independently and also considering the two-transistor analogy of the thyristor by a matrix method. The equivalent circuit is further modified to develop an equivalent circuit of the thyristor for the blocking and conducting state for both DC and AC operation. [ABSTRACT FROM AUTHOR]

This paper explains the requirements of thyristor chopper circuits to operate without any commutation limits and also explains the commutation processes of a thyristor chopper which satisfies these requirements. The practical design equations for the selection of components are derived and the complete design of the chopper circuit to meet typical drive specifications is presented. [ABSTRACT FROM AUTHOR]

The paper presents the effects of source inductance and discontinuous conduction in the load on the commutation, and voltage ratings of thyristors, diodes and capacitors of some commonly used chopper circuits. [ABSTRACT FROM AUTHOR]

This paper explains the methods for determining the commutation losses of a thyristor chopper circuit, derives analytical expressions for each component of commutation losses and demonstrates the importance of commutation losses on the design of the thyristor chopper to guarantee the minimum reverse bias time of the main thyristor. [ABSTRACT FROM AUTHOR]

The operation of a static reactor compensator using a thyristor phase-controlled inductor for improvement of the power factor of single-phase loads is investigated. Such compensators find widespread application with fast-changing loads such as electric are furnaces, induction furnaces, and rolling mill drives in the steel industry. A laboratory model of the reactive power compensator was built, and tested. The control scheme and associated control circuitry are explained in detail, and results showing the supply power factor with and without the compensator are presented. The transient response of the controller whenever the load is changed is illustrated by oscillograms which clearly show that the power factor is improved substantially and the regulator requires only one cycle to implement the desired correction. The dynamic response of the thyristor controlled reactor (TCPR) regulator indicates that there is scope for improvement in the control circuit, and modifications are suggested. [ABSTRACT FROM AUTHOR]

Analyzes a single phase current source inverter feeding an inductive load. Design criteria for the inverter; Proportion between the necessary commutating capacitance and the square of turn-off time of the thyristors; Circuit operation for higher frequencies.

The method employed in the measurement of plasma spreading velocity vs in power thyristors and the results obtained are reported in detail. To induce Vs to be primarily one-dimensional the thyristors were rectangular in configuration with gate contacts to measure the arrival of the plasma, being placed at regular intervals around the rectangular (alloyed) cathode. Gold-doped devices were compared with geometrically similar thyristors nominally gold free. Values of vs for gold-doped thyristors were persistently, though not always, lower. The current gain of the constituent transistors has also been measured and attempts are made to correlate these to the measured vs values. The current gains, particularly of the n-p-n section, prevailing in the ‘off’ region of a thyristor during a switch-on transient are contrasted with those obtaining during current gain measurements and are thought to be responsible, in conjunction with the lowered life-time in the wide n-base regoin of the p-n-p section, for the lowered vs values of gold-doped thyristors. [ABSTRACT FROM AUTHOR]

The three-phase stepped-wave inverter is based on a new method of synthesizing waveforms. The proposed system comprises a 120° conduction type three phase bridge inverter and a single-phase triple-frequency square-wave inverter. The triple-frequency inverter used for wave-shaping is of low power and is used in the neutral circuit of the three-phase inverter. A special complementary impulse commutation circuit realizes the above system with only eight thyristors. The output voltage waveform has three steps per quarter cycle and has a total harmonic distortion of 15-1%. The kVA ratings of the wound components are derived. The experimental results are presented and discussed. [ABSTRACT FROM AUTHOR]

Discusses the simultaneous elimination of undesirable harmonics and output voltage variation in a pulse-width modulated inverter. Advantages of the sinusoidal modulation technique and the Patel-Hoft method; Relationship between the actual load voltage waveform and phase shift angle; Causes of variation in phase shift between the triggering signals applied to the half-bridge inverters.

An automatic measurement system is described which plots current gain of the thyristor—regarded as an npn transistor—versus log frequency on an XY recorder, each curve being for a fixed anode voltage and current. By varying the latter two a series of curves can be recorded within minutes often with improved accuracy what previously could take hours to obtain manually. From these curves the individual current gain of transistor components constituting the thyristor can be quickly evaluated as a function of anode current and voltage. [ABSTRACT FROM AUTHOR]

A current fed thyristor inverter circuit useful for ultrasonic frequency cleaning and welding is analysed. The design criteria for the choice of circuit components and their effect on circuit operation are discussed. Experimental results are presented.
For high power ultrasonic applications such as cleaning and welding, a frequency range of 20 to 50 kHz is used. Transistor inverter circuits are generally used as ultrasonic sources. A number of transistors are connected in parallel to obtain the required power output. In high power applications thyristors can be used with advantage. With the advent of fast acting gate turn-off thyristors (Raderecht 1974), the thyristor circuits are likely to become more economical and the system more compact.
Voltage fed inverters (Fry 1960, Mapham 1967, Revankar and Karande 1974) can be used as ultrasonic sources. These circuits essentially consist of a series inverter configuration. The ultrasonic inverters proposed by Mapham have a better circuit turn-off time, but they suffer from high dv/dt. Nowadays the current fed inverters (Pelly 1970, Revankar and Gadag 1973, 1974) are being widely used for high frequency induction heating systems with a tuned compensated load because of their distinct advantages. These circuits work on the principle of forced commutation. They have high di/dt and starting problems. The principle of time-sharing (Thompson 1963, Akodis et al. 1965, Pelly 1970, Berkovich et al. 1973, Revankar and Patwardhan 1974) can be applied to increase the frequency range of such inverters. In this paper a current fed inverter described by Berkovich is studied in greater detail and its suitability for ultrasonic applications is discussed. [ABSTRACT FROM AUTHOR]

A simple type of d.c. chopper circuit with triacs is presented. The circuit is analyzed and the design criteria for the reliable operation of the circuit are evolved. Certain circuit modifications are suggested and their effects are discussed.
The triac (RCA manual 1971, GE SCR manual 1972) is basically a controlled bidirectional switch and can be used to replace the combination of a thyristor and an inverse-parallel connected diode used in chopper circuits. In an earlier work the concept of forced commutation in triac circuits (Revankar and Trasi 1975 a) is evolved and the necessary conditions are derived. Use of triacs in chopper circuits (Revankar and Trasi 1975 b) is investigated and a simple chopper circuit with a commutating L-C circuit directly across the main triac is presented. In this paper a triac chopper circuit, where the commutating circuit appears directly across the load circuit, is discussed. [ABSTRACT FROM AUTHOR]

Small-signal low-frequency current gains of the npn and pnp transistor sections of high and low power thyristors were measured by a three-terminal technique. From their dependence upon current and temperature it was found that the saturation current dependence of the isolated centre junction primarily determines temperature stability. Current gain measured at a series of temperatures, and plotted parametrically with anode current, qualitatively correctly predicts the temperature dependence of the two-terminal latching currents. Gold-doping predictably heads to a low current gain for the pnp section. [ABSTRACT FROM AUTHOR]

A solid state point on a wave switch has been developed using thyristors to control reactive loads. Completely transistorized control circuitry has been designed for this purpose with provision for one shot or repetitive action. Sequential closing of independent poles is also possible.
A reliable and high-speed point on a wave switch has interesting applications in a 'dynamic test bench' for protective gear testing (Hamilton and Ellis 1956) and in the study of transients in electric machines (Simpson and Slater 1967). Interest is mainly focused on recording the transient behaviour because it simplifies and allows systematic study. The conventional procedure for such requirement has been to use a thyratron relay circuit with momentum transfer device to eliminate contact bounce. Simpson and Slater (1967) utilised a two-pole unit employing power diodes and thyristors. The present work discusses a simpler method of achieving a point on a wave switch. The control circuitry has been designed to suit one-shot or repetitive operation. Provisions are made for sequential closing of a 3-pole unit. [ABSTRACT FROM AUTHOR]

The development of a high power, high frequency, inverter thyristor is described.
The techniques and procedures used to achieve forward blocking recovery times of less than 2 microseconds are summarized, and electrical test data are included to show that other thyristor parameters are not too adversely impaired.
This paper is concerned with the general problems involved in the design of high frequency thyristors, and briefly describes the techniques used to develop this particular device. [ABSTRACT FROM AUTHOR]

The impurity profile in the region of the forward blocking (control) junction of a thyristor was determined by means of measurements of capacitance versus voltage. The measurement frequency was chosen to minimize the influence of parallel and series resistances of all thyristor junctions. The determination of the impurity profile was based on the exponential approximation N(x)= N (exp (-x . )-1) of the impurity distribution on both sides of a diffused p-n junction. The procedure proposed here to determine two main parameters of the exponential distribution, N and , is a combination of previously known analyses presented by Scarlett (1959), van de Wiele et al. (1970), and van Opdorp (1968). The 1/C versus V and 1/C versus V curves experimentally determined serve to obtain N and . If, on the other hand the position of the junction, x, is known, a more exact approximation may be used based on the error function distribution. A comparison between both approximations was done in one special ease. The resulting impurity profile was compared with the impurity profile earlier known by four-point probe measurements. In the light of these two procedures the exponential approximation has been proved to be suitable.
The same method may be used to determine the impurity profile in the region of the reverse blocking junctions. [ABSTRACT FROM AUTHOR]

Discusses the failure mechanism of GTO thyristors and optimization for minimum current crowding during turn-off. Qualitative optimization of internal parameters through detailed two-dimensional device simulations to minimize the current crowding; Influence of the current crowding phenomenon on the maximum controllable anode current.

A digital logic model of a gate turn-off thyristor is developed considering the turn-on and turn-off mechanisms of the device. A commonly used R-C-D snubber circuit is also included in the proposed model. Relations between different delay times, e.g. storage time, fall time, turn-off time and tail time, become apparent from the model. The model is simulated with the help of a microprocessor to establish the validity of the proposal. [ABSTRACT FROM AUTHOR]

Describes a two-level circuit model for a gate turn-off thyristor in power electronic simulations. Basis of the semiconducting phenomena; Incorporation of additional charge control, anode-cathode and gate-cathode resistance modulation networks to simulate turn-off phenomena; Methods for determining the model parameters.

Outlines the design and construction of a half-wave quasi-resonant flyback converter using gate turn-off thyristor. Maximum operating frequency; Circuit analysis; Prototype design; Practical waveforms illustrating the operation of the circuit.

Discusses the induction cooking unit using a gate turn-off (GTO) thyristor. Technical and economic factors that have hindered the progress of induction cooking into the domestic market; Power supply design based on a Class E amplifier circuit employing a GTO at a nominal frequency.

Presents the state-of-the art developments in the sequential-switching high-power high-frequency inverter using reverse-blocking thyristors. Control implementation of the inverter on the basis of induction heating and melting applications; Description of fast-response power regulation and parallel tuned frequency tracking strategies; Use of state-variable clamped action.

In this paper the influence of the dynamic parameters of real thyristors on the properties of series inverters operating in the region of overlapping commutation has been presented. The formal SCR model has been used based on the rise time (t[sub r]) characterizing the thyristor turn-on process and on the reverse recovery time (t[sub rr]) and the total stored charged (Q[sub rr]) characterizing the thyristor turn-off process. [ABSTRACT FROM AUTHOR]

The work presents an alternative solution—with respect to the conventional cathode shunts or MOS-controlled emitter shorts—for achieving virtual immunity to the parasitic action of displacement currents in power thyristors. The simple design/technological approach developed, based upon the novel doubleinterdigitated or two interdigitation levels (TIL) concept with a coarse geometry, offers a fair balance between technological simplicity/cost effectiveness and overall device performance. Based upon the presented design guidelines, two sets of gold-doped thyristors with different geometrical configurations and current/voltage-handling capabilities were produced. The measurements performed on both sets of TIL-type thyristors have shown that the devices possess an extremely high value of the maximum permissible critical rate of rise of the forward anode voltage static dV/dtcapability) even under open-gate conditions. Unlike the thyristors using conventional emitter shorts, the TIL-type devices possess a good static and dynamic turn-on/latching sensitivity and have low on-state losses at high anode current densities. The main implications of developed concepts for power thyristors design/technology are also outlined in this work. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis of the transient and steady state processes in RC choppers. A difference equation describing these processes is obtained and solved. The analytical solution of the problem and the conditions of the transient and steady state existence in the chopper are found. Theoretical and experimental results both for transient and steady state conditions are compared and satisfactory agreements are obtained. [ABSTRACT FROM AUTHOR]

A rigorous developmental design is performed with the aim of achieving the limits of the peak interruptable anode current I[sub ATO] in the recently reported TO-220-packaged, high-voltage double-interdigitated (TIL) GTO thyristors. The 8mm²-area trial devices possess a safe operating value of I[sub ATO] = 60 A under the heaviest possible on-state power dissipation conditions. This value of I[sub ATO], which exceeds even the non-repetitive peak on-state current I[sub TSM] (50A) of test TIL GTOs and which corresponds to a peak switched current density of 750 A/cm², is the highest ever reported for this class of GTOs (with identical device area and case). The devices have good reliability at high commutation frequencies under heavy load conditions. They possess an excellent turn-on sensitivity accompanied by an immunity to noise (high dV/dt capability). [ABSTRACT FROM AUTHOR]

The work reports the development of trial high-voltage (2000-2500 V), high-current (up to 500 A) gate-assisted turn-off (GAT) thyristors based on the novel double-interdigitated or two interdigitation levels (TIL) gate-cathode configuration. The active cathode area of devices is only 1·7 cm² The test TIL GATTs were both normal, i.e. using no lifetime killers and gold-diffused at several temperatures. The investigations revealed the high efficiency of the negative current pulse, applied to the gate during the time when the forward anode voltage is being reapplied, in the reduction of the turn-off time t[sub q]. Thus, the application of a peak gate current I[sub GR] of only 2·5-4 A leads to a two- to tenfold decrease of t[sub q] in TIL GATTs rated at an anode current iv of 200-500 A. Within the aforementioned levels of iv and at constant value of I[sub GR], the dependence of t[sub q] on i[sub T] was found to be relatively weak. The dependence of TIL GATT performance on gold-doping, junction temperature, n-base thickness and the rate of reapplied anode voltage rise is presented in detail. All trial TIL GATTs possess an excellent turn-on sensitivity accompanied by a high immunity to noise. The results presented reveal the ability of TIL patterns with a relatively coarse geometry to perform multiple-end roles in various modes of operation of high-power GATTs. [ABSTRACT FROM AUTHOR]

The current-gain values of the effective component transistors of a thyristor structure are measured by a method originally due to Fulop (1963) and the technique is shown to be applicable to measurements on high-power thyristors, provided that certain precautions are taken with the measuring system. [ABSTRACT FROM AUTHOR]

The demands of transmitter users for equipment with increased power-to-weight ratios can be met by eliminating mains transformers and condensers and replacing them with inverters incorporating mains-voltage semiconductor devices. The relative merits of silicon thyristors and power transistors for this and similar applications are considered.
Breakdown voltages of 800 volts and operating frequencies exceeding 20 kHz, rising in future to 100 kHz or more, are required, together with maximum possible power ratings.
Thyristors meet the voltage and power requirements, but the ultimate frequency-limiting factor is the minority-carrier lifetime in the wide base. Methods of reducing this with minimum sacrifice or blocking voltage and forward voltage drop requirements are discussed. Diminishing returns limit the practical maximum frequency.
In power transistors the collector must accommodate depletion-layer spread, since the base-width must be held down to meet frequency requirements. High blocking voltages raise saturation voltage problems. The effects of base-width, emitter-current density and breakdown voltage on frequency are examined. Interdigitated or mesh-emitter structures are required to limit current crowding.
It is concluded that high-power transistors offer the better long-term prospect of satisfying transmitter power-supply requirements. [ABSTRACT FROM AUTHOR]

Several batches of inverse gate thyristors were prepared including some from golddoped silicon. A pattern of ohmic contacts to the p-type base was incorporated into the cathode region below the p-n junction. The spreading of the conduction pulse when the devices were switched on was monitored directly and the spread of the conducting region was found to be slower in devices with thicker base regions and in gold-doped devices with thinner base regions. For the devices made on large area discs of silicon the conducting front became non-circular as it spread to the edge of the device. [ABSTRACT FROM AUTHOR]

An analysis is made of the possibility of achieving switching action in a silicon thyristor structure which contains thick intrinsic layers to improve the high voltage performance. It is concluded that if the intrinsic layers are sufficiently thick to significantly improve on present thyristor voltage ratings then it will not be possible to obtain controlled switching. [ABSTRACT FROM AUTHOR]

A device is described in which thyristors are used to score information as to the state of a digital display unit (e.g. digital voltmeter or scaler). One thyristor corresponds to each possible setting of each possible tube. A trigger pulse of about 10 sec duration is used to 'read' the display and the corresponding thyristors become conducting. The conducting thyristors can then be used to transmit a 'print' pulse for a conventional tape punch or printer. The speed of repetition is limited only by the speed of the punch unit (or printer).
A number of systems commercially available allow the automatic transfer of data displayed on a digital display unit (e.g. a digital voltmeter or scalar counting system) to an electronic typewriter or paper tape punch. Most of these systems have two major drawbacks. The first problem is that the data-collecting equipment, is interrupted for a period of time which may be unacceptably long, normally ranging from a few hundredths of a second at best to a second or so at worst. The second--sometimes the more serious problem--is that of cost, since some of the faster commercial interrogating-printing systems can cost over a thousand pounds. [ABSTRACT FROM AUTHOR]

The temperature rise in rectangular thyristors during the gate-triggered turn-on process is analyzed by means of Laplace transforms and residue calculus. Two models for the heat generation in the thyristor material are considered: uniform heat generation throughout the turned-on volume of the thyristor and heat generated only in the turned-on region of the central p-n junction. Conditions for excessive temperature in the thyristor during turn-on are considered.
Critical factors (besides the current and voltage of the thyristor), giving a large temperature rise, are shown to be the current rise time, the spreading velocity of the current-carrying region and the geometry of the thyristor. The most critical factor, however, is found to be the distribution of the heat generation in the thyristor. The temperature rise under pulsed load conditions is also treated. Numerical examples are given.
The mathematical model given in the paper may be used to calculate the excess temperature for thyristors of arbitrary geometry. [ABSTRACT FROM AUTHOR]

There are two important problems that arise in the design of bi-directional thyristors, particularly for high-current applications. These are the problem of (1) gate isolation and (2) commutation. The former arises in bi-directional thyristors with two gates, one to fire in the 1st quadrant and the other to fire in the 3rd quadrant of the device's characteristics. The normal requirement is that the 1st quadrant gate should not fire in the 3rd quadrant and vice versa. Successful gate isolation consists of meeting this requirement.
The problem of commutation arises when a bi-directional thyristor which has been carrying current in one quadrant is switched rapidly into the other quadrant, where it is expected to present a blocking characteristic. Under some circumstances stored charge effects can cause the device to turn on in the other quadrant (i.e. fail to commutate).
In this paper analyses are made of both these problems, some practical results are given, and the implication in actual device design is examined. [ABSTRACT FROM AUTHOR]

The advantages of an IC 555 timer in thyristor phase control are examined. Analysis of the standard line voltage compensation scheme shows that the modulating voltage of the timer can be conveniently employed for this purpose. A simple modification in the circuit also makes it an ideal zero crossover switch. [ABSTRACT FROM AUTHOR]