Papers by Keyword: Thyristor

Abstract: 4H-SiC thyristors are of particular interest in pulsed power applications due to their ability to block high voltages and transfer high current densities along with fast switching times. Here, we present a paper that demonstrates both (i) the impact of the design parameters on the blocking characteristics based on simulations taking into account the anisotropy of 4H-SiC and (ii) a critical comparison to real devices having equivalent epitaxial structural design. Simulations and measurements show that an etched junction termination extension (JTE) is suitable to design high-voltage SiC thyristors. Concerning breakdown voltage, the real devices data agree to simulations for junction termination extension thickness in the relevant region. Besides the actual JTE thickness and doping concentration, the presence of a relatively thin field-stop layer might explain the discrepancy between experiment and simulation.

Abstract: This paper presents experimental 1.2 kV, 10 A SiC thyristors with different amplifying gate design. In contrast to comparative devices (with simple gate) the amplifying gate thyristors show a characteristic snap-back and a higher gate current to trigger. Their gate-anode I-V characteristics comply with the underlying design constraint, regarding the resistances of pilot and main thyristor: (R_P > R_M). Moreover, the turn-on waveforms of well-designed amplifying gate thyristors reveal peak-shaped inversions in the gate current and voltage transients, providing clear evidence of the successive triggering of pilot and main thyristor.

Abstract: High performance 15 kV n-GTOs were demonstrated for the first time in 4H-SiC. The device utilized a 140 μm thick, lightly doped n-type drift layer, with 1450°C lifetime enhancement oxidation, which resulted in a carrier lifetime of 17.5 μs. The p⁺ backside injector layer was thinned to minimize parasitic resistances. A room temperature forward voltage drop of 5.18 V was observed at a current density of 100A/cm². A 1 cm² device showed a leakage current of 0.17 μA at 15 kV. The 4H-SiC n-GTO showed latching characteristics, and showed a turn-off time of 170 ns in a resistive load switching setup, which represents about a factor of 45 improvement in turn-off speed over 4H-SiC p-GTOs with comparable voltage and current ratings.

Abstract: An investigation into the increased leakage currents and reduced blocking voltages associated with 1450°C lifetime enhancement oxidation for the 4H-SiC p-GTOs is presented. Roughening of the 4H-SiC surface due to localized crystallization of SiO₂, or crystobalite formation, during the high temperature oxidation was identified as one of the main causes of this issue. A factor of 30 difference in permeability to O₂ between amorphous SiO₂ and crystobalite caused uneven oxidation, which resulted in significant roughness. This roughness, placed at the metallurgical junction between the gate and the drift layer, where the E-field is greatest, is believed to be responsible for the premature breakdown characteristics. A 2-step lifetime enhancement process, which moves this roughness to the lower E-field region of the device was introduced to alleviate this issue. A 15 kV 4H-SiC p-GTO with the 2-step lifetime enhancement process demonstrated a significant reduction in V_F over the 1300°C oxidized devices, without any impact on blocking characteristics.

Abstract: The impact of the lifetime enhancement process using high temperature thermal oxidation method on 4H-SiC P-GTOs was investigated. 15 kV 4H-SiC P-GTOs with 140 μm thick drift layers, with and without 1450°C lifetime enhancement oxidation (LEO) process, were compared. The LEO process increased the average carrier lifetime in p-type epi layer from 0.9 μs to 6.25 μs, and it was observed that the effectiveness of the lifetime enhancement process was very sensitive to the doping concentration. The device with the LEO process showed a significant reduction in forward voltage drop and a substantially lower holding current, as expected from the carrier lifetime measurements. However, a slight reduction in blocking capability was also observed from the devices treated with LEO process. The common emitter current gain (β) of the wide base test NPN BJT was approximately 10X higher for the wafer with LEO process.

Abstract: Optical switch-on of a very high voltage (18-kV class) 4H-SiC thyristor with an amplification step (pilot thyristor) to the current I_max = 1225A has been demonstrated using a purely inductive load. The results obtained show that a further switch-on current increase can only be achieved by introducing additional amplification steps in the pilot thyristor structure.

Abstract: The high-voltage SVC realizes the dynamic reactive power compensation through the real-time control over the breakover and cut-off of thyristor. Because the current passing through thyristor is large, the frequent break-make will lead to a lot of thermal loss, so it should be cooled in time. The self-cooled heat pipe cooling system is a traditional high-voltage SVC cooling system, which is expensive and heavy because it adopts relatively expensive copper product and aluminium product.This paper introduces a new heat pipe radiator. Compared to the traditional heat pipe radiators, it is light in weight, small in volume and low in cost. The performance test shows that the thermal resistance of the radiator is 0.064°C/W, that the main performance indexes are superior to those of the similar heat pipe radiators at home and abroad and that its self-cooling ability has achieved a high level. Therefore, it will greatly promote the promotion and application of this technology in China.

Abstract: The power energy storage in battery transfers to capacitors through thyristor in hybrid energy storage, which makes the instantaneous power amplified. As the switch in Hybrid energy storage, the thyristor must satisfy its opening requirements , besides, the characteristics of the hybrid energy storage system is considered to design the width of trigger pulse, otherwise the thyristor can’t be opened that leads to failure of energy transfer. In this paper, the model of the system is established, the function of current to time is derived from the model, and then the minimum width of trigger pulse is calculated out. The simulation and experiment results are presented, which match with the designation well.

Abstract: A single-element passive quenching with active reset (PQAR) circuit is proposed. Its operation mechanism is studied in theory to show that this single element, based on thyristor, can provide similar function of quenching and reset for the free-running Geiger-mode operation of single photon avalanche diodes (SPADs) as the conventional PQAR circuits, but with significant simplicity. Requirement for the thyristor is identified, and an InP sample was designed, fabricated and characterized. Future work for further demonstration is also discussed.

Abstract: On the basis of incomplete three function mathematical principle, the method of using three point interpolation and undetermined coefficient can solve control circuit equation, which can realize the automatic conversion circuit of the AC/DC current, to achieve very good automatic control effect. In order to verify the effectiveness and reliability of the mathematical model, this paper designs twelve pulse thyristor full wave circuit current conversion experiment, the core of circuit analysis uses Web circuit computer online control system and Motorala development DSP56000 processor, and using the RAM port and the bus carry out communication. Finally, the system is introduced the design of Internet Web ideological and political education platform, to provide the technical support for the ideological and political Internet online education.