Breakover Voltage Research Articles

A Bidirectional Fast EV Charger for Wide Voltage Range Using Three-Level DAB Based on Current and Voltage Stress Optimization

Converter cost is the crucial concern while designing off-board electric vehicle (EV) chargers for high-voltage charging applications using advanced high breakover voltage power semiconductor switches. To solve this problem, multilevel topology is used with the typical dual active bridge (DAB) for the development of high-voltage and high-power EV charging. It offers low cost, compact, less complex control, highly efficient, and reliable development. This article presents the design and development of bidirectional off-board fast EV charger with voltage and current stress optimization for wide voltage range. It is designed with two-stage power conversion. Here, active front-end converter is connected to three phase grid and controlled through synchronous reference frame (SRF) d-q control approach for active rectification. The large range of power and voltage variation in off-board EV charger design makes it challenging to develop a controller that allows the converter to operate inside the zero voltage switching (ZVS) operating region. In this context, a detailed circuit analysis of dc–dc stage with dual phase shift (DPS) control under different operating conditions is presented to identify the coordinates of safe operating region with reduced voltage stress. To select the converter control parameters with optimum current stress in conjunction with reduced voltage stress, particle-swarm-optimization technique is applied to the identified operating regions. This provides a unique selection criterion for both control parameters over wide voltage conversion ratio. A coordinated control is designed based on the identified boundaries for easy implementation and less computation burden on microcontroller units (MCUs). A 7.2-kW system is designed and simulated on MATLAB/Simulink. A 3.3-kW laboratory prototype is designed to validate the identified operating points with wide battery voltage range under varying source and loading scenarios.

Study of the effect of switching speed of the a-SiC/c-Si(p)-based, thyristor-like, ultra-high-speed switches, using two-dimensional simulation techniques

A parametric study for a series of technological and geometrical parameters affecting rise time of Al/a-SiC/c-Si(p)/c-Si(n+)/Al thyristor-like switches, is presented here for the first time, using two-dimensional simulation techniques. By varying anode current values in simulation procedure we achieved very good agreement between simulation and experimental results for the rising time characteristics of the switch. A series of factors affecting the rising time of the switches are studied here. Two factors among all others studied here, exerting most significant influence, of more than one order of magnitude on the rising time, are a-SiC and c-Si(p) region widths, validating our earlier presented model for device operation. The above widths can be easily varied on device manufacture procedure. We also successfully simulated the rising time characteristics of our earlier presented simulated improved switch, with forward breakover voltage and forward voltage drop at the ON state, exhibiting an ultra low rise time value of less than 10 ps, which in conjunction with its high anode current density values of 12 A/mm2 and also cheap and easy fabrication techniques, makes this switch appropriate for ESD protection as well as RF MEMS and NEMS applications.

Origin of the Ultrafast Response of the Lateral Photovoltaic Effect in Amorphous MoS2/Si Junctions.

The lateral photovoltaic (LPV) effect has attracted much attention for a long time because of its application in position-sensitive detectors (PSD). Here, we report the ultrafast response of the LPV in amorphous MoS2/Si (a-MoS2/Si) junctions prepared by the pulsed laser deposition (PLD) technique. Different orientations of the built-in field and the breakover voltages are observed for a-MoS2 films deposited on p- and n-type Si wafers, resulting in the induction of positive and negative voltages in the a-MoS2/n-Si and a-MoS2/p-Si junctions upon laser illumination, respectively. The dependence of the LPV on the position of the illumination shows very high sensitivity (183 mV mm-1) and good linearity. The optical relaxation time of LPV with a positive voltage was about 5.8 μs in a-MoS2/n-Si junction, whereas the optical relaxation time of LPV with a negative voltage was about 2.1 μs in a-MoS2/p-Si junction. Our results clearly suggested that the inversion layer at the a-MoS2/Si interface made a good contribution to the ultrafast response of the LPV in a-MoS2/Si junctions. The large positional sensitivity and ultrafast relaxation of LPV may promise the a-MoS2/Si junction's applications in fast position-sensitive detectors.

Simulation-Based Study About the Lifetime and Incident Light Properties Dependence of the Optically Triggered 4H-SiC Thyristors Operation

We investigated a methodology to design light-triggered thyristors thanks to TCAD. The simulation model accuracy, especially the holding current and the minimum incident light intensity to turn-ON, were compared with experimental results. The influence of SiC epitaxial layer lifetime and the incident light properties (wavelength and intensity) on the optically triggered 4H-SiC thyristor characteristics have been studied by simulation. We considered the wavelength dependence of quantum efficiency, penetration depth, and photon energy. The holding current and turn-ON time depends on the lifetime. The minimum intensity to turn-ON the device significantly depends on the wavelength. This intensity becomes less than 0.003 times when the wavelength changed from 380 to 325 nm. In addition, the breakover voltage is affected by the constant incident light even if the intensity is tiny.

20 mA bidirectional laser triggering in planar devices based on vanadium dioxide thin films using CO(2) laser.

By utilizing a CO2 laser centered at ~10.6 μm as an optical stimulus, we demonstrated bidirectional laser triggering in a two-terminal planar device based on a highly resistive vanadium dioxide (VO2) thin film. The break-over voltage of the VO2-based device was measured as large as ~294.8 V, which resulted from the high resistivity of insulating VO2 grains comprising the thin film and the large electrode separation of the device. The bidirectional current switching of up to 20 mA was achieved by harnessing the dramatic resistance variation of the device photo-thermally induced by the laser illumination. The transient responses of laser-triggered currents were also analyzed when laser pulses excited the device at a variety of pulse widths and repetition rates. In the transient responses, a maximum switching contrast between off- and on-state currents was measured as ~7067 with an off-state current of ~2.83 μA, and rising and falling times were measured as ~30 and ~16 ms, respectively, for 100 ms laser pulses.

Two dimensional simulation and modeling of the electrical characteristics of the a-SiC/c-Si(p) based, thyristor-like, switches

The electrical characteristics of the Al/a-SiC/c-Si(p)/c-Si(n+)/Al switches were successfully simulated here for the first time. Forward breakover voltage VBF, forward voltage drop VF and anode current simulated values of the device showed very good agreement with the experimental results. Electric field and impact generation rate across the switches are also simulated for different anode current conditions extending to second breakdown region of the device, showing a shifting of the phenomena caused by electric field and impact generation rate, from c-Si(p) region to a-SiC film as anode voltage values increase from VBF up to second breakdown region of the device. A both simulation and experimental based model describing the device behavior, is also presented here. Two critical facts leading to switching transition are proved to be at first a-SiC/c-Si(p) heterojunction breakdown dominated by impact generation rate and second subsequent trap filling in the amorphous film. Al/a-SiC/c-Si(p+)/c-Si(p)/c-Si(n+)/Al switches with reduced VBF and VF values, were also fabricated and successfully simulated here, enhancing the validity of our simulation procedure and making the switches candidates for ESD protection devices, also due to their advantages of high anode current value density of 5A/mm2 before reaching second breakdown conditions in conjunction with cheap and easy fabrication procedure mainly due to r.f. sputtering technique used for a-SiC film fabrication.

Analysis and Optimization of a Thyristor Structure Using Backside Schottky Contacts Suited for the High Temperature

In high current, high voltage, high temperature power applications, commercially available conventional silicon thyristors are not suited because they present high leakage current. In this context, this paper presents a high-symmetrical (voltage) thyristor structure that presents a lower leakage current and higher breakover voltage as compared with the conventional thyristor at. It is shown through 2-D physical simulations that the replacement of the P-emitter of a standard symmetrical thyristor by a judicious association of P diffusions and Schottky contacts at the anode side contributes to the reduction of the leakage current in the forward blocking state at high temperature. A fine tune of the anode side configuration will improve the forward OFF-state behavior with only a negligible ON-state voltage drop degradation. Moreover, the comparison with the conventional anode short thyristor shows that the insertion of Schottky contacts leads to the same improvements in terms of OFF-state forward breakover voltage and leakage current and also presents a high reverse blocking voltage.

Mechanical and Thermal Properties of Polymethyl Methacrylate‐BN Nanotube Composites

Polymethyl methacrylate (PMMA)‐BN nanotube (BNNT) composites were fabricated and their mechanical and thermal properties were analyzed. Using a 1 wt.% BNNTs fraction in a polymer, the elastic modulus of PMMA was increased up to 19%. In addition, thermal stability and glass transition temperature of PMMA were also positively affected. The thermal conductivity of PMMA with BNNT additions increased three times. The resultant BNNT‐PMMA composites possess the high electrical breakover voltages. Thus our studies clearly indicate that BNNTs are promising nanofillers for improvement of mechanical and thermal conductivity of dielectric polymers under preservation of their electrical insulation.

Design and Simulation of a Thyristor Surge Protective Device for Telecommunication Systems

This paper describes the design of a thyristor surge protective device (TSPD) for telecommunication equipments based on electrical simulations carried out with ATLAS from SILVACO. The influence of the device doping and geometry on the breakover voltage, switching and holding current and on the on-state voltage drop has been analyzed. It has been shown that the TSPD voltage capability is dependent on the breakdown voltage of the p-n (substrate) junction. Also, it has been observed that pregion doping concentration and emitter geometry have both a great impact on the on-state device operation. A TSPD with breakover voltage of 297 V, holding current of 38.5 mA and on-state voltage drop of 6.7 V at a current of 1 A has been demonstrated.

Dual Gate Emitter Switched Thyristor의 전기적 특성

Two dimensional MEDICI simulator is used to study the electrical characteristics of Dual Gate Emitter Switched Thyristor. The simulation is done in terms of the current-voltage characteristics with the variations of p-base impurity concentrations and current flow. Compared with the other power devices such as MOS Controlled Cascade Thyristor(MCCT), Conventional Emitter Switched Thyristor(C-EST) and Dual Channel Emitter Switched Thyristor(DC-EST), Dual Gate Emitter Switched Thyristor(DG-EST) shows to have tile better electrical characteristics, which is the high latch-up current density and low forward voltage-drop. The proposed DG-EST which has a non-planer u-base structure under the floating N+ emitter indicates to have the better characteristics of latch-up current and breakover voltage in spite of the same turn-off characteristics.

Dual Gate Emitter Switched Thyristor의 Latch-up 전류 특성

Two dimensional MEDICI simulator is used to study the characteristics of latch-up current of Dual Gate Emitter Switched Thyristor. The simulation is done in terms of the current-voltage characteristics, latch-up current density, ON-voltage drop and electrical property with the variations of p-base impurity concentrations. Compared with the other power devices such as MOS Controlled Cascade Thyristor(MCCT), Conventional Emitter Switched Thyristor(C-EST) and Dual Channel Emitter Switched Thyristor(DC-EST), Dual Gate Emitter Switched Thyristor(DG-EST) shows to have the better electrical characteristics, which is the high latch-up current density and low forward voltage-drop. The proposed DG-EST which has a non-planer p-base structure under the floating <TEX>$N^+$</TEX> emitter indicates to have the better characteristics of latch-up current and breakover voltage.

Influence of Different Peripheral Protections on the Breakover Voltage of a 4H-SiC GTO Thyristor

Influence of Different Peripheral Protections on the Breakover Voltage of a 4H-SiC GTO Thyristor

Spice Analysis for the DC Behavior of the Light Amplifying Optical Switch (LAOS)

A heterojunction phototransistor (HPT) is integrated in series with a light-emitting diode to form an optoelectronic device called Light Amplifying Optical Switch. This device has been shown to switch from low current region to high current region at a voltage called breakover voltage. This switching has been attributed to the presence of optical and electrical feedback mechanisms as well as to gain nonlinearity. A circuit model for such device that took into account different factors affecting the switching behavior has been proposed previously. In this paper, a modification to the previously published circuit is made and a spice model is presented for the modified circuit and hence for the LAOS. The spice results presented here are compared to published results and showed a good qualitative agreement. In addition, several factors that affect the switching behavior of such device are analyzed and a good agreement with published results is achieved. The spice model presented here can be very helpful to engineering students in studying optoelectronic circuits and systems that use LAOS.

The critical charge density in high voltage 4H-SiC thyristors

The critical charge density in 2.6 kV 4H-SiC thyristors, n cr, has been investigated in the temperature range from 300 to 500 K using gate-controlled switching and pulsed optical triggering. The n cr values furnished by these different techniques are in reasonable agreement. The n cr decreases monotonically from n cr∼10 16 cm −3 at T=300 K to n cr∼10 14 cm −3 at T=500 K. At room temperature, the n cr value found in this study for high-voltage SiC thyristors is an order of magnitude larger than that in low-voltage SiC thyristors with breakover voltage of 400 V, and is of the same order as that in the high-voltage power Si thyristors.

Advanced operational techniques and pn-pn-pn structures for high-power silicon carbide gate turn-off thyristors

SiC GTO thyristors may soon be the best available choice for very high-power switching. At this time, the authors have developed new operational techniques, growth requirements and pn-pn-pn type structures to address the issues of high on-state voltage, poor turn-off gain, and inability to reach predicted breakover voltages. They present these findings using experimental measurements and numerical simulations.

Turn-off operation of a 2.6 kV 4H-SiC gate turn-off thyristor in MOS-gate mode

The turn-off operation of a 4H-SiC gate turn-off thyristor with 2.6 kV breakover voltage has been studied in the MOS-gate mode by means of computer simulation. The turn-off was analyzed at different blocking voltages in the temperature range from 300 to 500 K. A good agreement between the simulation results and experimental data was demonstrated. It is shown that, according to the experiment, for complete turn-off of a thyristor in the MOS-gate mode, the duration of the turn-off pulse applied to the MOSFET gate, Δ t off, should be long enough (Δ t off>Δ t * off), where Δ t * off is the minimum duration of the turn-off pulse. The Δ t * off value depends rather weakly on the cathode blocking voltage V 0, despite the strong dependence of the critical charge density on V 0. It is shown that the long delay in the spontaneous switch-on, occurring at Δ t off⩽Δ t * off, is due to the very slow current rise at low injection level in the blocking p 0-base. An analytical theory of the current rise processes has been developed for the case when the current injection coefficients of the emitter–base junctions are not unity.

Turn-off performance of 2.6 kV 4H-SiC asymmetrical GTOthyristor

4H-SiC asymmetrical gate turn-off thyristors (GTOs) with 2.6 kV breakover voltage have been studied in relation to the gate turn-off performance. Transient characteristics of SiC GTOs and the pulse regime of gate turn-off processes were studied in the temperature range 293 to 500 K. At cathode current density of 300 A cm-2, a turn-off current gain KG of 12.5 was achieved at room temperature. The above value of KG is the highest reported for SiC GTOs. The temperature dependences of the turn-off time, pulse turn-off gate current and holding current were studied.

Turn-off Performance of a 2.6 kV 4H-SiC Asymmetrical GTO Thyristor

H-SiC asymmetrical gate turn-off thyristors (GTOs) with 2.6 kV breakover voltage have been studied in relation to the gate turn-off performance. Transient characteristics of SiC GTOs and the pulse regime of gate turn-off processes were studied in the temperature range 293 to 500 K. At cathode current density of 300 A cm −2 , a turn-off current gain KG of 12.5 was achieved at room temperature. The above value of KG is the highest reported for SiC GTOs. The temperature dependences of the turn-off time, pulse turn-off gate current and holding current were studied.

A new optoelectronic integrated device for light-amplifying optical switch (LAOS)

A new optoelectronic integrated device is proposed for a light-amplifying optical switch (LAOS). The device is composed of an optical field-effect transistor (OPFET) in series with a light source which may be either a double heterostructure light-emitting diode (LED) or laser diode (LD). A quantitative circuit model for the proposed LAOS is presented and theoretical investigation is carried out for developing a current-voltage (I-V) relation for the device. It is shown analytically that switching action takes place from a low current state to a high current state through a region of negative differential resistance (NDR) when a voltage greater than the breakover voltage is applied.

Turn-off operation of a MOS-gate 2.6 kV 4H–SiC gate turn-off thyristor

The turn-off operation of a 4H–SiC gate turn-off thyristor (GTO) with 2.6 kV breakover voltage has been investigated using an external Si-MOSFET as a gate-to-emitter shunt (MOS-gate mode), in the temperature interval 293–496 K. The maximum cathode current density j cmax that can be turned off in such a mode decreases from 1850 A/cm 2 at 400 K to 700 A/cm 2 at 496 K. The room temperature j cmax value is estimated to be about 3700 A/cm 2. The above j cmax values are essentially higher than those observed when turning this thyristor off in the conventional GTO mode. Turn-off transients in the MOS-gate mode have been studied in both quasi-static and pulse regimes. Temperature dependencies of the turn-on and turn-off times, as well as those of the turn-on and turn-off energy losses have been measured. The upper switching frequency of the GTO is estimated to be about 700 kHz.