High Current Switching Research Articles

Analytical Switching Loss Modeling Based on Datasheet Parameters for <sc>mosfet</sc>s in a Half-Bridge

Modern wide-bandgap devices, such as SiC- or GaN-based devices, feature significantly reduced switching losses, and the question arises if soft-switching operating modes are still beneficial. For most of the semiconductor devices, only limited information is available to estimate the switching losses. Especially, if a wide operating range is desired, excessive measurements have to be performed to determine the switching losses for arbitrary operating points. Therefore, in this paper, a fast calculation method to determine the switching losses based on the charge equivalent approximation of the mosfet capacitances, relying only on datasheet parameters, is presented. In addition, the turn- off losses at high switching currents are investigated, and an analytical expression to estimate the maximum current range for which the mosfet can be turned off with negligible switching losses is proposed.

Two-pulse sub-ns switching scheme for advanced spin-orbit torque MRAM

The steady increase in performance and speed of modern integrated circuits is continuously supported by constant miniaturization of complementary metal-oxide semiconductor (CMOS) devices. However, a rapid growth of the dynamic and stand-by power due to transistor leakages becomes a pressing issue. A promising way to slow down this trend is to introduce non-volatility in circuits. The development of an electrically addressable non-volatile memory combining high speed and high endurance is essential to achieve these goals. To further reduce the energy consumption, it is essential to replace SRAM in modern hierarchical multi-level processor memory structures with a non-volatile memory technology. The spin-orbit torque magnetic random access memory (SOT-MRAM) combines non-volatility, high speed, and high endurance and is thus suitable for applications in caches. However, its development is still hindered by relatively high switching currents and the need of an external magnetic field for deterministic switching of perpendicularly magnetized layers. The switching by means of two orthogonal current pulses allows achieving deterministic sub-500 ps and magnetic field-free switching in perpendicularly magnetized rectangular structures. Complementing the two-pulse switching scheme with weak perpendicular interface-induced magnetic anisotropy reduces the switching current significantly for achieving sub-500 ps switching in in-plane structures.

Device and System-Level Transient Analysis in a Modular Designed Sub-MW EV Fast Charging Station Using Hybrid GaN HEMTs + Si MOSFETs

Though wide bandgap devices are believed to be promising candidates for next-generation high-efficiency and high-power-density power electronic converters, two major challenges remain, high cost (more than twice of Si) and less options (the maximum power rating for GaN is only 650 V/60 A). From the device level, paralleling GaN with Si can inherit merits of both GaN devices (superior switching performance) and Si devices (affordable with high-current capability). In this paper, first, GaN HEMTs are paralleled to a TO-247 Si MOSFET to form a high-current switching cell for a 6.6-kW electric vehicle (EV) charging module. A time delay is added between the switch gate signals to make GaN endure the switching loss and Si conduct majority of the static current. Critical dynamic behaviors, such as the current overshoot to the GaN, current distribution during the dead time, and voltage spike during the turn off caused by parasitics, are comprehensively discussed. From the system level, series connecting the input and paralleling output of multiple such modules yield a sub-MW EV charging station. Once one phase drops, the related phase can act as the active filter, while other two phases still work to charge the battery.

Corona-stabilized gas spark gap switch for a double forming line with 300 kV working voltage

A high-current self-breakdown gas switch stabilized by corona preionization was developed for closing of 300 kV repetitively operated at 10 pps water insulated double-forming line (Blumlein) of a nanosecond electron accelerator. The switch is installed at the end of the Blumlein and is used for closing of outer of two coaxial lines. High stability of the self-breakdown voltage (within ±1%) at fast charging of Blumlein (during ≈1.4 μs) is achieved by gas preionization in the spark-gap by additional pulsed corona discharge. The spark-gap electrode system includes two main toroidal electrodes and an additional corona needle that is located in the cavity of one of them (negative during the operation). It combines two parallel gas discharge gaps – the main spark gap and an additional corona discharge gap. Separating the functions of the spark and corona gaps makes it possible to optimize the geometry of the electrodes of each gap and provide both the ability to switch high currents and high dynamic characteristics for a long operating time. Dried air is used as a working gas at pressure of 3-4 atm (abs.). Gas blowing system includes 4 gas inlets located at outer flange supporting the high voltage insulator (water-gas interface) and one outlet in the cavity of the grounded main electrode. This scheme of gas flow protects the insulator from deposition of electrode erosion products and minimizes gas flow (≈20 l/min) for stable operation of the switch by removing of the hot gas throw the cavity of the grounded electrode.The design of the switch together with the main results of the working tests will be presented and discussed.

Balance of Horizontal and Vertical Charge Transport in Organic Field-Effect Transistors

Beyond the usual, lateral layouts for organic field-effect transistors (OFETs), vertical designs allow for high current densities and fast switching, but charge transport in such a configuration is not well understood. This study integrates experiments on light-emitting transistors with drift-diffusion simulations to investigate the formation of the conduction channel in a vertical OFET. The authors present a model for the lateral extent of the channel, and its scaling behavior. The results will allow us to find better routes to optimize such vertical OFETs, and the methodology extends to other vertical devices as well.

Mn-Zn ferrite line EMI suppressor for power switching noise in the impulse/high current bias regime

Ferrite cores 50 mm long were formed from large ferrite tubes obtained using fine Mn-Zn ferrite powder (M-30-IHIS) extruded and sintered at 1280 $^{\circ}$C for 2 h. Core impedance was measured in the HF range (0.1--100 MHz), varying the number of coil turns and DC bias. Characteristic parameters such as maximum of impedance Z$_m$, frequency of maximum impedance F$_m$, and suppressing range f around F$_m$ were determined for each configuration. The analyzed ferrite cores were tested as round cable suppressors in the impulse regime. Impulses were generated by MOSFET transistor switching of high currents (1--10 A). The number of turns, impulse current, and DC bias current were varied in the range from 0 to 10 A. Magnetic interference configurations were formed on the ferrite core using opposite wound coils and tested in the impulse regime. Suppressor responses to different impulses were mutually compared and analyzed. Finally, two ferrite cores were EM coupled by a short circuited coil to form a novel line EMI suppressor aimed for suppression of power switching noise. Several configurations were formed with coupled cores acting on a magnetically interfering principle with opposite coils. The realized configurations were analyzed in view of application for EMI suppression in an uninterruptible power supply and AC/DC and DC/DC converters.

Thermal Resistance Evaluation of Low-Inductance Double-Stacked SiN-AMC Substrate for High-Temperature Operation SiC Power Module

Silicon carbide (SiC) power device is attracting attention as a candidate for future power device, since they can be operated at higher current density and higher switching speed than conventional silicon (Si) power device. A power module packaging technology for SiC power device should have both low thermal resistance and low inductance to bring out a potential ability of the device. In general, high-speed with high-current switching causes huge surge noise due to the parasitic inductance of the module. We have introduced a double-stacked silicon nitride active metal brazed copper (SiN-AMC) substrate as a circuit board which has five-layer (Cu/SiN/Cu/SiN/Cu) structure by bonding two SiN-AMC substrates. The parasitic inductance of the module is reduced by minimizing the loop area of the current path using a internal conductor layers of the double-stacked SiN-AMC substrate as a current return path. However, it is predicted that the double-stacked SiN-AMC substrate power module has higher thermal resistance compared with the conventional power module which has single SiN-AMC substrate. In this paper, the thermal resistance of double stacked SiN-AMC was measured by transient thermal analysis method and investigated the magnitude of the effect of SiN thickness, Cu thickness and SiN thermal conductivity. The appearance of the test vehicle is shown in Fig. 1. Each type of the test vehicle which is composed of an SiC-Schottky barrier diode (SiC-SBD), one (or two) SiN-AMC(s) and an Al baseplate were fabricated. The specifications of the SiN-AMC substrate to be compared are shown in Table 1. The thermal resistance of each test vehicle was measured by transient thermal analysis method and the thermal resistance of the SiN-AMC substrate part was extracted. The measurement results of thermal resistance at SiN-AMC substrate part are shown in Fig. 2. In general, it is considered that increasing the thermal conductivity of a portion with a relatively low thermal conductivity (in this case it is SiN) in the module or thinning the total thickness of the SiN-AMC substrate leads to a reduction in thermal resistance. However, in case the SiC die size is 3 mm square, we found that the thickness of the Cu film is more effective than the thermal conductivity of SiN in order to reduce the thermal resistance of the module. Thermal resistance of double stacked SiN-AMC with 0.3 mm-thick Cu film is lower than the thermal resistance of single SiN-AMC with 0.1 mm-thick Cu film. The effect of changing Cu film thickness is higher than changing thermal conductivity of SiN from 90 W/mK to 140 W/mK. If Cu film of the SiN-AMC substrate is thick the thermal resistance is reduced, since the heat is diffused in the in-plane direction and the heat-flow area is increased. These results will help for optimizing the power module circuit board which has both low inductance and low thermal resistance. Figure 1

Generation of High-Voltage Pulses with a Picosecond Front in a Cascade Kivotron Connection

The possibility of the operation of high-current high-voltage switches based on “open” discharge with the generation of counter-propagating electron beams, that is, kivotrons, in a two-stage pulse compression scheme is demonstrated experimentally. The total degree of the initial-pulse compression, which exceeded 600 at a minimum measured front duration of a generated pulse of at most 100 ps, was achieved at a voltage of up to 18 kV and a pulse-repetition rate of 1 kHz.

Time-resolved ion energy and charge state distributions in pulsed cathodic arc plasmas of Nb−Al cathodes in high vacuum

Cathodic arcs have been utilized in various applications including the deposition of thin films and coatings, ion implantation, and high current switching. Despite substantial progress in recent decades, the physical mechanisms responsible for the observed plasma properties are still a matter of dispute, particularly for multi-element cathodes, which can play an essential role in applications. The analysis of plasma properties is complicated by the generally occurring neutral background of metal atoms, which perturbs initial ion properties. By using a time-resolved method in combination with pulsed arcs and a comprehensive Nb−Al cathode model system, we investigate the influence of cathode composition on the plasma, while making the influence of neutrals visible for the observed time frame. The results visualize ion detections of 600 μs plasma pulses, extracted 0.27 m from the cathode, resolved in mass-per-charge, energy-per-charge and time. Ion properties are found to be strongly dependent on the cathode material in a way that cannot be deduced by simple linear extrapolation. Subsequently, current hypotheses in cathodic arc physics applying to multi-element cathodes, like the so-called ‘velocity rule’ or the ‘cohesive energy rule’, are tested for early and late stages of the pulse. Apart from their fundamental character, the findings could be useful in optimizing or designing plasma properties for applications, by actively utilizing effects on ion distributions caused by composite cathode materials and charge exchange with neutrals.

The development of shock wave overpressure driven by channel expansion of high current impulse discharge arc

During the formation of a high current impulse discharge arc, objects near the discharge arc will be strongly impacted. In this paper, a high power, high current gas switch is used as the site of the impulse discharge arc. The explosion wave theory and the arc channel energy balance equation are introduced to analyze the development of the shock wave overpressure driven by the high current impulse discharge arc, and the demarcation point of the arc channel is given, from which the energy of the arc channel is no longer converted into shock waves. Through the analysis and calculation, it is found that the magnitude of the shock wave overpressure caused by impulse discharge arc expansion is closely related to the arc current rising rate. The arc shock wave overpressure will undergo a slow decay process and then decay rapidly. The study of this paper will perform the function of deepening the understanding of the physical nature of the impulse arc discharge, which can be used to explain the damage effect of the high current impulse discharge arc.

Hydrothermal assisted growth of vertically aligned platelet like structures of WO3 films on transparent conducting FTO substrate for electrochromic performance

Controlled growth of nanostructured metal oxide films growing on the conducting substrates with good adhesion in a single step process via hydrothermal method is still challenging. In the present work, WO3 platelets were deposited on transparent conducting fluorine doped tin oxide substrates by single step hydrothermal process via tailoring the reaction time (8 h, 12 h and 16 h) and reaction temperature (120 °C and 180 °C). X-ray diffraction analysis showed that the WO3 thin films grown at 120 °C for 8 h and 12 h reaction time comprised with mixed phases of hexagonal and monoclinic system, whereas 16 h of reaction time produced single phase monoclinic system. However the WO3 films deposited at 180 °C for 8 h, 12 h and 16 h reaction time acquired monoclinic system. Raman spectrum showed the stretching and bending modes of WO3. The WO3 films deposited at 120 °C and 180 °C for different reaction time 8 h, 12 h and 16 h exhibited various surface morphology such as buds like, bricks like, platelets like and sheets with platelets like structures. Optical studies showed that the transmittance of WO3 film is decreased with increase in the reaction temperature. The WO3 film deposited at 120 °C for 12 h reaction time acquired transmittance of about 86% at 463 nm whereas the film deposited at 180 °C for 12 h reaction time showed transmittance of about 75% at 465 nm. The direct and indirect optical band gap of the deposited WO3 films varies in the range 2.5 eV– 2.9 eV and 2.6–2.75 eV respectively with varying growth parameters. The electrical properties of WO3 film deposited at 120 °C for 12 h showed relatively low resistivity (1.8 × 10−3 Ωcm) and high carrier concentration (9.3 × 1019 cm−3). The electrochromic studies carried out for the WO3 film synthesized at 120 °C for 16 h exhibits high peak current density, diffusion coefficient and fast switching kinetics with respect to other deposited films.

An experimental setup for investigation of arc and erosion processes in high-voltage high-current breakers

An experimental test setup for investigating arc and erosion processes in gas-filled high-voltage high-current switches is described and some results that were obtained on it are presented. The setup includes a discharge chamber that allows simulation of the process of disconnecting the ring and pin contacts, a capacitive energy storage with a capacitance of 0.11 F and a charging voltage of up to 10 kV, and a remotely controlled gas-supply system. The diagnostic complex includes systems for measuring the discharge current, the voltage across the arc, and the pulse pressure in the chamber, as well as high-speed filming and optical spectroscopy. Experiments with a current amplitude of 30–300 kA can be performed on the test bench. During the first current half-period of 1.0–3.0 ms, the contacts move apart to a distance of 3–4 cm. The arc is cooled via transverse gas blowing at a pressure in the chamber of 0.5–1.5 MPa. A movable contact is displaced due to the pressure of the gas that is pumped into the chamber.

High-current pulse switching by thyristors triggered in the impact-ionization wave mode

The operation of a thyristor switch triggered in the impact-ionization wave mode was investigated. The switch contained two series-connected Т253-800-24 thyristors of the tablet design with a semiconductor- structure diameter of 56 mm. When a triggering pulse is applied to the switch at a voltage rise rate dU/dt of more than 1 kV/ns, the transition time of the thyristors to the conducting state was shorter than 1 ns. It was shown that the maximum amplitude of the no-failure current increases with an increase in dU/dt at the triggering stage. The possible mechanism of the influence of the dU/dt value on the thyristor breakdown current is discussed. In the safe operating mode at dU/dt = 6 kV/ns (3 kV/ns per single thyristor), the switch discharged a storage capacitor with a capacitance of 1 mF, which was charged to a voltage of 5 kV, through a resistive load of 18 mΩ. The following results were obtained: the discharge-current amplitude was 200 kA, the initial current rise rate was 58 kA/μs, the pulse duration (FWHM) was 25 μs, and the switching efficiency of 0.97.

An Off-line Single-Inductor Multiple-Output LED Driver With High Dimming Precision and Full Dimming Range

This paper presents a single-inductor multiple-output (SIMO) LED driver with precise dimming and full dimming range. Based on the coordination of a string-level scheme and a system-level dimming scheme, the proposed SIMO LED driver can overcome practical constraints of existing SIMO LED drivers such as limited dimming range and needs for high-current switches. The proposal can achieve dimming precision up to an accuracy of 0.8% and also full dimming range. It has the flexibility of using either phase-shift or synchronous pulsewidth-modulated (PWM) switching for dimming control. The proposed circuit and control operations have been practically verified with a 25-W off-line SIMO-driven LED system. Practical evaluations of its power quality and energy efficiency are also provided.

Effect of the anchoring groups on the switching behaviour of the dihydroazulene/vinylheptafulvene molecular junction with zigzag-edged graphene nanoribbons electrodes

ABSTRACTThe switching behaviour of dihydroazulene/vinylheptafulvene molecule with different anchoring groups sandwiched between two zigzag-edged graphene nanoribbons (ZGNRs) electrodes is investigated by applying nonequilibrium Green's function formalism combined with first-principles density functional theory. The calculated results show that the anchoring groups play a significant role in determining the electronic transport properties and switching behaviour of the molecular junctions. A higher current switching ratio without any oscillation can be obtained for the molecular junctions with carbon atom anchoring group, which suggests that this system has a broader application in future logic and memory devices.

Design and Characterization of High-Current Optical Darlington Transistor for Pulsed-Power Applications

A high-current and low on-state voltage optical Darlington transistor (ODT) is developed in this paper for high-power applications. The structure of this device includes a two-stage Darlington transistor in which the first stage is triggered optically using an infrared laser of an 808-nm wavelength. The photogenerated current in the first stage drives the second stage of the ODT for current amplification. The ON-state voltage of the proposed two-stage ODT is found to be 1.12 V at 50 A. The results show that a single-pipe laser with a low optical power of 2 W is sufficient to trigger this high-current optical switch. This can give us more flexibility to achieve an optimal tradeoff between the ON-state voltage and delay times. The experimental results show that the ODT has a breakdown voltage of 70 V and can operate at frequencies higher than 10 kHz. Thismakes it potentiallysuitable as an optical gate driver for applications including but not limited to pulsed-power and series-connectionof power semiconductor devices for voltage scaling, and as an auxiliary optical-triggering device for anode- or even gate-currentmodulation of a high-frequency and high-power all-optical emitter turn-OFF thyristor.

Voltage transients in thin-film InSb Hall sensor

The work is reached to study temperature transients in thin-film Hall sensors. We experimentally study InSb thin-film Hall sensor. We find transients of voltage with amplitude about 10μV on the sensor ports after current switching. We demonstrate by direct measurements that the transients is caused by thermo-e.m.f., and both non-stationarity and heterogeneity of temperature in the film. We find significant asymmetry of temperature field for different direction of the current, which is probably related to Peltier effect. The result can be useful for wide range of scientist who works with switching of high density currents in any thin semiconductor films.

Rotating Constricted Switching Arcs Burning in Gas and in Vacuum

The method of controlling high-current switching arcs by transverse magnetic fields (TMF) forcing the constricted arc to rotate in a contact system is being applied successfully to improve the breaking capability of vacuum interrupters and gas circuit breakers. We describe the behavior of magnetically driven switching arcs in vacuum and in gas environment. We report on experiments using high-velocity videography, magnetic probes, and spectroscopy; they deliver the velocity, the temperature and the voltage of an arc. We present models and simulations of the moving constricted arc burning in metal vapor and in air. And we describe a particular switching application of TMF arc control and explain a scaling law of the contact size with the current interruption capability.

A high-current rail-type gas switch with preionization by an additional corona discharge

The characteristics of a high-current rail-type gas switch with preionization of the gas (air) in a spark gap by an additional corona discharge are investigated. The experiments were performed in a voltage range of 10–45 kV using a two-electrode switch consisting of two cylindrical electrodes with a diameter of 22 mm and a length of 100 mm and a set of laterally located corona-discharge needles. The requirements for the position and size of the needles are defined for which a corona discharge is ignited before a breakdown of the main gap and does not change to a sparking form, and the entire length of the rail electrodes is efficiently used. The fulfillment of these requirements ensures stable operation of the switch with a small variation of the pulse breakdown voltage, which is not more than 1% for a fixed voltage-pulse rise time in the range from 150 ns to 3.5 μs. A short delay time of the switch breakdown makes it possible to control the two-electrode switch by an overvoltage pulse of nanosecond duration.

High-current Semiconductor Switch instead of High-current Relay

High-current Semiconductor Switch instead of High-current Relay