Circuit utilization characteristics of MOS-controlled thyristors

Measurements have been made evaluating the switching and conduction characteristics of the first commercially available 600-V MCT (MOS controlled thyristor), the second-generation, 600-V MCT still under development, and a fast commercially N-IGBT (insulated-gate bipolar transistor). The data presented indicate that great strides have been made in improving the electrical performance of the P-MCT in the generation 2 device. Using the fmax curve as a figure of merit, the lower switching losses of the N-IGBT are favorable, under the test conditions used, compared to the generation 1 P-MCT up to approximately 50 A. The lower conduction losses of the MCT become the predominant factor for larger current levels. The generation 2 P-MCT combines the same conduction loss characteristics as its predecessor, with drastic reductions in turn-off switching times and losses. The combined effect gives the generation 2 P-MCT the lowest losses over the whole current and frequency range evaluated. The N-IGBT provides a better safe operating area than either of the P-MCTs, though capacitive snubbers can be employed to improve this situation. >

Measured and simulated turn-off curves of high-voltage MCTs (MOS-controlled thyristors) and IGBTs (insulated-gate bipolar transistors) are presented. Device simulation results show that the inherently faster-switching IGBT is much more affected by dynamic avalanche phenomena than the MCT. It is also shown that the avalanche-injected carriers can be removed by shorting the anode layer, resulting in a much higher turn-off performance for both devices. Because of the lower charge and therefore the higher dV/dt, the ionization rate is higher in the IGBT than in the MCT. >

An attempt was made to simplify the processing of MCT (MOS controlled thyristor) and IGBT (insulated-gate bipolar transistor) devices by combining the anneal of the p/sup +/-emitter with the gate oxidation process. A high-dose boron implantation prior to the gate oxidation is found to be responsible for significantly reduced breakdown field strengths observed for gate oxides in the MCT and IGBT devices. A failure mechanism based on lattice misfit stress and implantation damage below the amorphization threshold is proposed, which explains the observation that breakdown events occur exclusively at the very periphery of the implanted regions. This is in accordance with the scaling law that is found, exhibiting a logarithmic relationship between the breakdown strength of MOS capacitors and the perimeter length of p/sup +/ regions in the substrate. The substantial reduction in breakdown field strength was found to result in yield losses. By appropriate separate annealing of the p/sup +/-emitter, such weak spots in the gate oxide are not observed. With the use of BF/sub 2//sup +/ for the p/sup +/-emitter implantation it was possible to prevent yield losses and to reach intrinsic breakdown field strengths while still staying with the simplified device processing.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Chapter 2 - Power Semiconductors

A high-voltage phase-controlled symmetrical thyristor with MOS control was developed called the QCT. The QCT consists of two thyristor parts integrated on the same wafer; one MOS-controlled thyristor (MCT) with low conducting losses and a parallel conventional phase-controlled thyristor (PCT) with low switching losses. During the on-state both thyristor parts conduct the current. At commutation, the MCT-part is turned off, forcing the current over to the PCT. Thereby the QCT, even with high-voltage blocking capability, can have both low on-state losses and low switching losses, An experimental QCT for 5-10 kV has been designed and processed, having a diameter of 45 mm with a segmented MCT-part of 9-cm/sup 2/ area with high carrier lifetime to achieve low conduction losses and a 1.5-cm/sup 2/ PCT with low carrier lifetime to achieve low switching losses. The QCT has a conventional amplifying thyristor gate for turn-on and separate MOS-gates for turning off the MCT-part. The QCT was designed for a current handling capability of 400 A. It was shown that the reverse recovery charge could be reduced three to five times as compared to a device without this MOS-control.

There is a continuous demand for improvements in the quality of switching power devices, such as higher switching frequency, higher withstand voltage capability, larger current-handling capability, and lower conduction losses. However, for single-conduction-mechanism devices (SCRs, GTOs, BJTs, FETs), possessing all these features is probably unrealizable for physical reasons. An attractive solution appears to be double-mechanism devices, in which the features of both a minority carrier device (BJT or SCR) and a majority carrier device (MOSFET) are embedded. Both IGBTs (insulated-gate bipolar transistors) and MCTs (MOS-controlled thyristors) belong to this family of double-mechanism devices and promise to have a major impact on converter circuit signs. The authors deal with the major features of these two devices, pointing out those that are most critical to the design of power converter topologies. In particular, the two devices have been tested both in a chopper and in two resonant link converter topologies, and the experimental results are reported. >

SummaryTurn-off semiconductor devices have vastly promoted modern power electronics during the last decade. Included are bipolar power transistors. Field Effect Transistors (MOSFETs), Gate Tun-off Thyristors (GTOs) and Insulated Gate Bipolar Transistors (IGBTs). Additional elements are Static Induction Transistors and Thyristors (SITs and SIThs) as well as MOS Controlled Thyristors (MCTs) for higher frequency applications.The prensent status of semiconductor power devices is discussed including switching behavior, losses, gate driver, snubber, overcurrent and protection. The standard control is nowadays pulse width modulation, Resonant circuits are growing in importance because they allow for higher frequency, lower storage components and transformers and reduction of switching losses in semiconductor devices, Main field of application are discussed and future trends given.

The effect of different carrier lifetimes on the forward I-V characteristics of a MOS-controlled thyristor (MCT) has been studied using numerical simulation. Those physical mechanisms that have a strong effect on the forward operation of the MCT have been identified and taken into account. The results show that in the design tradeoff between the switching speed and forward current capability there exists a characteristic lifetime below which the operation mode changes from thyristor-like to IGBT-like, and in the transfer between them a region of differential negative resistance exists. >

Chapter 4 - Safe Operating Area Design

A novel trench insulated gate bipolar transistor (IGBT) with emitter dual injection (EDI-IGBT) is proposed and investigated. The device features the hybrid gate electrode and the tiny P-base. The hybrid gate is a combination of the conventional trench gate (TG) and the accumulation gate (AG). The TG contacts the P-base region and the N-drift region, while the AG contacts the N-drift region only. In the ON-state, the accumulation layer formed by the AG makes an additional accumulation injection in the emitter side, leading to the EDI phenomenon, and hence a low forward voltage drop (VON). Simultaneously, the tiny P-base region reduces holes extracted by the reversebiased p-base/n-drift junction, which also contributes to the reduction in VON. The simulation results show that the EDI-IGBT delivers comparable breakdown voltage and safe operating area (SOA) while featuring a 28% lower VON, resulting in a reduction in total energy loss. Moreover, the existence of the AG suppresses the gate self-charging effect during the turn-on transient, leading to an improved turn-on performance. The excellent device performance, coupled with industry-standardIGBT-compatible fabrication process, makes the proposed EDI-IGBT a promising candidate for power switching applications.

This paper discusses the characteristics and limitations of various power semiconductors used in motor controls and drives. Semiconductor types discussed include the insulated gate bipolar transistor (IGBT), transistor (bipolar and MOS device), SCR, gate-turn-off transistor (thyristor) (GTO), and diode. Important limitations, including voltage rating, current ratings, safe operating area, heat transfer characteristics, and limitations due to a particular device characteristic are discussed. The focus is on the IGBT; its advantages and disadvantages are discussed, as well as how it can be rated in a drive application.

Insulated gate bipolar transistor (IGBT)-based pulsewidth modulation (PWM) inverters are commonly used in inductive load circuits such as motor control. During clamped inductive load turn off of the IGBT, high-power losses occur during two phases. Due to the large inductive motor load, the voltage across the IGBT rises to the bus voltage while carrying the full-rated current. In the second phase, the current decreases as the IGBT goes into its forward blocking mode. In this paper, the turn-off process during the first phase is analyzed in detail for the first time. A simple analytical model has been derived, based upon the initial steady-state minority carrier distribution, which allows predicting the rate of rise of the voltage during this time period where the collector current remains constant. The predictions of the analytical model are in excellent agreement with results obtained from two-dimensional (2-D) numerical simulations over a broad range of minority carrier lifetime values. This analytical model provides a good estimate (within 10%) of the power losses incurred during the first phase of turn off.

The Safe Operating Area (SOA) of lithium-ion (Li-ion) batteries defines the permissible range of operational conditions (e.g. temperature, voltage) within which the battery operates safely and reliably, avoiding damage, performance degradation, or critical hazards such as thermal runaway. While the SOA concept is critical for battery performance optimization and safety assurance, its evolving nature has led to inconsistent definitions and methodologies across the literature. These fragmented perspectives hinder the development of a solid understanding and practical application of SOA. This review addresses these gaps by systematically examining the diverse perspectives and methodologies surrounding SOA. It categorizes and structures related topics directly and indirectly linked to SOA while integrating insights from adjacent fields to construct a cohesive framework. By treating SOA as an evolving concept, this work assembles its “building blocks” from various disciplines, creating a comprehensive roadmap for defining and refining SOA boundaries. The proposed approach aims to guide researchers and practitioners in advancing safer, more efficient battery systems. • Comprehensive Review of SOA & Critical Analysis. • Bridging SOA with Related Fields. • Unified and Structured Framework for SOA. • Systematic Categorization of existing SOA concepts. • Practical Guide for Modular SOA Design.

The emitter turn-off (ETO) thyristor is a new type of MOS-controlled thyristor that has a wide reverse-biased safe operation area (RBSOA) due to its unity-gain turn-off capability. Because of the negative feedback provided by the emitter MOSFET, the ETO also has current saturation capability. The forward biased safe operation area (FBSOA) of a small ETO is experimentally demonstrated. The results show that the small ETO has excellent current saturation capability that can be used to control the turn-on di/dt. Issues related to realizing a large area ETO's FBSOA are discussed.

4H-SiC gate turn-off (GTO) thyristor offers extraordinary advantages over its counterparts in handling ultra-high voltage electric power conversion applications because of its relatively low forward voltage drop at high conduction current density. Besides, though the SiC thyristors never suffer from long carrier liftime induced large switching loss like Si thyristors, the peak temperature rise rather than dynamic avalanche breakdown is blamed for the safe operation area (SOA) failure, making further reduction of power loss in SiC GTOs even more important. In this paper, a 20 kV SiC GTO with direct carrier extraction access to its drift region (DA-GTO) is investigated to explore the benefit this structure could bring for SiC thyristors, namely achieving smaller switching loss and/or potential larger SOA with slight sacrifice in forward voltage drop at high current. The structure is formed by interleaved P+ ion implantation into part of the thin N-injector layer based on conventional 20 kV SiC GTO. The SiC DA-GTO operates in BJT mode at low current, and in GTO mode with low forward voltage drop at high current. During turn-off process, it offers a direct current path to quickly sweep out the excess carriers in the P-drift region, thus speeds up the turn-off process and decreases the turn-off loss. Simulation results show that its turn-off loss reduces by 37.4%, contributing to 12.6% reduction in total power loss, compared with SiC GTO. Therefore, SiC DA-GTO is a very promising choice for next-generation power conversion systems.