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Circuit modeling is an essential tool in the design of power electronic applications. The widespread use of these models, however, depends upon the availability of parametric data for devices and the proper trade-off of the accuracy and simplicity of the model. This paper addresses these two areas with regard to the forward on-state voltage of thyristors and diodes. As has been described in previous papers, forward on-state forward voltage drop can be modeled by the now classical ABCD parameters. This paper discusses the problems and strengths of the ABCD model and describes how the ABCD parameters can be quickly and efficiently calculated by a 3rd order, multiple, nonlinear regression in a new STARS Visual module. This paper proposes an alternate mathematical model to the ABCD model, labeled the MNOP model, and describes the advantages of this model. This paper also describes one of the main limitations of the ABCD model, which is the fact that it is typically used to describe the maximum forward voltage drop on the data sheet, which is NOT an isothermal curve. This, in turn, does not permit the change in the on-state forward voltage drop as a function of junction temperature to be modeled. Isothermal models of diodes and thyristors will be discussed and a new simplified model proposed for surge and overload conditions.

For circuits using SCRs and diodes, both the on-state forward voltage drop and transient thermal impedance are complex characteristics, for which adequate mathematical models been developed. The on-state forward voltage drop can be modeled by both the classical ABCD and the new MNOPQ...parameters. The transient thermal impedance can be well represented via four or five exponential terms representing the significant transient thermal time constants of the device. There is, however, one complication which is not represented in the ABCD and MNOPQ...models. This is the dependence of the on-state voltage on the instantaneous junction temperature. This effect, termed COD or VFIT, requires that the model be electro-thermal, meaning that this important dependence must be accounted for in a microsecond by microsecond manner during the simulation. This paper describes the basic device modeling equations and the techniques required to use these models in "analog" simulation programs such as PSPICE/sup TM/. Parameter extraction from empirical test data is described and the electro-thermal model accuracy evaluated. The final and new result is an electro-thermal model for power electronic application using SCRs and diodes which includes the dynamic effect of instantaneous junction temperature on the on-state voltage. The resulting PSPICE/sup TM/ electro-thermal model is expected to be an important design tool in multi-megawatt power electronic applications, providing the detailed analysis the power electronic engineer needs to quickly evaluate an existing or proposed power electronic application.

Circuit modeling is an essential tool in the design of power electronic applications. Both the onstate forward voltage drop and transient thermal impedance of high power SCRs and diodes are complex functions. The main objective of this paper is how to use modeling equations to evaluate a given power electronic application. The forward on-state forward voltage drop can be modeled by both the classical ABCD and the new MNOP...parameters. The transient thermal impedance has been shown to be well represented via four or five exponential terms representing the significant transient thermal time constants of the device. Both the digital (hard code) simulation and "analog" PSPICE simulation techniques are described. Also, a new tool, called STARSim, is described. STARSim permits comparison of the older superposition method and new modeling method by performing the calculations using both approaches. A simple SCR model for PSPICE incorporating the on-state forward voltage drop and transient thermal impedance models is also described and evaluated. This information is considered to be important in providing the tools required for power electronic design engineers to quickly evaluate a given device in proposed or existing power electronic application.

Circuit modeling is an essential tool in the design of power electronic applications. The widespread use of these models, however depends upon the availability of parametric data for devices and the proper trade-off of accuracy and simplicity of the model. This paper addresses these two areas as well as describing another modeling subject, the spatial temperature distribution during serge and overloads of thyristors and diodes. The conversion from the physical ladder thyristor (diode) thermal model to the much simpler series equivalent thermal circuit model was described previously. This paper describes a unique multiple regression method to automate the calculation of the parameters for the simplified model. This permits the manufacturer to provide the necessary parameter values for the power electronic design engineer to hard code and/or use SPICE circuit modeling to obtain the waveform of virtual junction temperature verses time in a proposed or existing application. An important characteristic of thyristors is the ability to withstand surge and overloads significantly above their steady state ratings. When considering this ability of the device to absorb and remove heat we are forced to extend our analysis to another dimension, namely, the physical or spatial distance through the device. The spatial temperature-time distribution provides a millisecond by millisecond account of the temperature in each of the device components during surge and overload conditions.

The design, fabrication, and characteristics of a 350-V, 100-A buried-gate static induction transistor (SIT) as a power switching device for applications in military and space environments because of its potential for radiation hardness, high-frequency operation, and the incorporation of on-chip smart power sensor and logic functions are described. The potential radiation hardness of this class of devices was evaluated by measurement of SIT characteristics after irradiation with 100-Mrad (2-MeV) electrons and up to 10/sup 16/ fission neutrons/cm/sup 2/. High-temperature operation and the possibility of radiation damage self-annealing are discussed. >

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, V DRM . 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.

A light-triggered thyristor (LTT) is a four-layer pnpn switch that can be triggered in a different mode than electrically triggered thyristors. For the former, photocarriers generated in the space-charge region activate the pnp transistor first, whereas for electrically triggered thyristors the gate current activates the npn transistor.