Power Semiconductor Switches Research Articles

GTO thyristor and bipolar transistor cascode switches

The switching performance of both the bipolar transistor and gate turnoff thyristor is improved when used in a cascode switch configuration. ‘Snubberless’ turnoff occurs without second breakdown and the technique results in shorter saturation delay times, faster current fall and higher operational sustaining voltages than obtained with conventional switching techniques. Improved switching performance is traded for increased drive circuit complexity and an increased on-state power loss associated with two series connected power semiconductor switches. The circuit techniques features and performance of two 720 V DC, 320 A cascode switches are presented. The bipolar transistor cascode switch is tested up to 100 kHz, whereas tail current power loss limits the GTO thyristor cascode switch to 16 kHz.

An optically controlled closing and opening semiconductor switch

A concept for a bulk semiconductor switch is presented, where the conductivity is increased and reduced, respectively, through illumination with light of different wavelengths. The increase in conductivity is accomplished by electron ionization from deep centers and generation of bound holes. The reduction of conductivity is obtained by hole ionization from the excited centers and subsequent recombination of free electrons and holes. The transient behavior of electron and hole density in a high power semiconductor (GaAs:Cu) switch is computed by means of a rate equation model. Changes in conductivity by five orders of magnitude can be obtained.

A Graphical Approach to AC Drive Classification

A classification of ac drive technology is presented. A series of diagrams show how the various types of ac drives have evolved into families that meet various application requirements. The objective is to provide a convenient graphical format from which suitable drive types for classes of applications are readily apparent. The diagrams are organized around the input and output power circuit topology with the type of semiconductor power switch as the primary classification element. All other drive properties, such as motor type, control strategy, power level, voltage level, and regeneration capability, are incorporated by segmenting and highlighting portions of the basic diagrams. A discussion of drive properties is also presented and integrated with the graphical presentations.

270-V Dc Hybrid Switch

High-voltage direct current (dc) power is one of the most efficient, reliable, and lightweight methods to generate and distribute energy. This power system is not in common use today on aircraft or other weight- and reliability-sensitive applications because of difficulties in switching high-voltage dc power. This difficulty becomes acute when switching at high altitude because of the very low mobility of an arc in low pressure. Direct application of power semiconductor switching devices is feasible but would result in severe thermal problems for other than the lowest current applications. A novel switching device is described that overcomes these shortcomings. This device is based on a unique combination of power semiconductor and contact structure switching systems. This hybrid switching device exhibits arcless switching for currents below two times the device rating. Above this current level the contact structure limits the current to a level that can be handled by the power semiconductor. The contact structure develops this currentlimiting capability over a range of pressure from atmospheric to 20 torr. At low pressures a high arc mobility is achieved through a novel approach where the arc develops its own environment. The arc plasma decomposes plastic wall materials to produce an environment that is conducive to high arc mobility.

Power electronics, control of the electromechanical energy conversion process and some applications

Some fundamental considerations regarding power electronics and machine electronics are discussed. The historical development of ideas in this field is examined, the applications in the field of electric traction for rail vehicles are summarised and possible future developments are outlined. A systematic approach to power electronics, based upon the control of energy flow in switching convertors, is presented. This approach takes into consideration the different possible switching functions, the modulation functions, the realisation of these switching and modulation functions, the realisation of these switching and modulation functions by practical power semiconductor switches and the different classes of forced turn-off and commutation in power electronic circuits. Subsequently the concepts of topology and structure are defined, leading to different generic topologies for singular convertors. The structure of the five different families of composite convertors are examined, and practical examples are given. The systematic approach to machine electronics presented in the paper is based on a power flow model, using the unifying concept of rotating field theory. In combination with previously defined systematics for power electronics, this enables a systematic approach to the different classes of variable speed drives, based on power flow considerations. The historical developments of some power electronic and machine electronic ideas are traced, starting at the beginning of this century. Since the introduction of power semiconductor switches, applications of the older ideas have increased exponentially in all fields, making it impossible to cover all of them. As a consequence the development of power electronics and control of machines by electronic convertors in the field of electric traction is discussed in some detail, because this represents a record of important engineering achievements in this field. In conclusion, the present state and future trends of power and machine electronics are examined. This evaluation covers the development in the field of switching devices regarding the improvement of interfacing between signal and power electronics, the decrease of switching transition times, the reduction of device losses during conduction, and device developments for decreasing energy storage devices in convertors. The development of power electronic convertors for the reduction of the number of components in the topology and the development of convertors with a high frequency link are then covered, related to the expected development of switching devices. New directions of development regarding the electronic conditioning of the electromechanical energy conversion process concerning the elimination of undesirable effects and losses are important. The implementation of these trends by utilising the improved switching characteristics of power electronic switches and the information processing capability of microprocessors is discussed. This is then extended toward control aspects, where both these characteristics enable solutions not possible hitherto. Field control of AC machines imparts control characteristics equal to, or better than, those obtainable with DC machines to the systems, while the processing capability of microprocessors allows the configuration of adaptive machine electronic systems. Finally attention is given to the interfacing of power electronic and machine electronic systems to the power supply network. If the exponential growth of the installed capacity of equipment in the future is to be handled, active compensation of the distorted currents drawn from the supply by this equipment will have to be considered seriously.

Power semiconductor switching devices—A comparison based on inductive switching

In this paper, a comparison of the switching efficiency of MOSFET's Darlington transistors, field controlled thyristors (FCT's), and gate turn-off thyristors (GTO's) will be made for devices with breakdown voltages between 100 and 1000 V. The comparison is made as a function of switching frequency with a 50-percent duty cycle and for devices of the same area, carrying the same current. Conclusions are presented as to the most appropriate device for different combinations of breakdown voltage and switching frequency requirements.

Optical bistability in semiconductors

Detailed results are presented on optical bistability (OB) and two-beam optical transistor (transphasor) action in simple, one-element Fabry-Perot devices, with the semiconductor InSb using a CW CO laser near the bandgap region, and OB for semiconductors in general is discussed. OB and multistability are seen in transmission and reflection at 5 K. At 77 K, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n_{2} \simeq 3 \times 10^{-3}</tex> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /W [corresponding to an effective <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\chi^{(3)} \sim 1</tex> ESU] is measured and OB is observed at ∼8 mW. Transphasor action at 5 K is presented and the influence of degenerate four-wave mixing is discussed. The basic physics of the microscopic mechanism for n <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (bandgap-resonant saturation) is summarized and a simplified, generalized model is derived. This model and arguments on cavity optimization are used to predict order of magnitude limits to switching power, energy, and speed, both in InSb and other semiconductors, even in the absence of excitonic enhancement.

A wide-band wattmeter for the measurement and analysis of power dissipation in semiconductor switching devices

A technique is presented for accurately measuring and displaying the magnitude and time function of the exchange and absorption of electrical energy in linear and nonlinear circuit elements such as semiconductor power switches. A novel electronic wattmeter with a wide-band (dc to 10 MHz) linear multiplier is used to observe the instantaneous product of the time-varying voltage and current in an arbitrary load. Experimental data show that the peaks of power dissipation during the turn-on and turn-off phases of a switching power transistor are much greater than the power dissipated during the time intervals of settled current flow. Furthermore, it is verified experimentally that the average power dissipation increases linearly with the transistor pulse-repetition frequency beyond a static (dc) value. The absence of such a frequency-dependent component of power dissipation in switches of resonant-current circuits is also confirmed.