Semiconductor Switches Research Articles

Determination of electromagnetic disturbances in a buck chopper

ABSTRACT Electrical energy performs increasingly diverse functions through the widespread use of static converters. These converters are based on the use of semiconductor switching components that generate rapid voltage (dV/dt) and/or current (dI/dt) variations. This can result in electromagnetic disturbances that must be minimised in order to respect electromagnetic compatibility standards. Compliance with standards is often achieved by adding a heavy and bulky filter to the system. In order to optimise the EMC aspects, it is interesting to take into account the EMC constraint from the design phase, in order to do so, a predictive study of these disturbances must be available. In this work, the origins of electromagnetic disturbances created by a series chopper are presented. Electromagnetic interference in this DC/DC converter is determined by using simulation and experimental measurements.

A twelve-switch power conditioner for voltage and current compensation in three-phase four-wire grids

An interesting solution for problems associated with system voltage, such as sags and swells, as well as those associated with current such as low power factor and harmonic distortion is the unified power quality conditioner. However, one of its drawbacks is the high number of semiconductor devices since its conventional topology presents two full-bridge converters connected in a back-to-back configuration. Therefore, this paper proposes a twelve-switch converter topology as a power conditioner for voltage and current compensation in three-phase four-wire grids. The developed topology ally low voltage characteristic of dc bus of a hybrid power filter with a reduced number of semiconductor switches and the capability of homopolar voltage and current compensation through the converter fourth leg for the neutral wire connection. In the twelve-switch converter, there are two sets of three-phase four-wire outputs, each set behaving as an independent converter unit. One of these units is connected in parallel to the load by means of a series LC filter, working as a hybrid power filter and being responsible for the compensation of current harmonics and imbalance. The second converter unit is responsible for compensating harmonics, sags or swells in the grid voltage, in such way that the load receives a sinusoidal voltage waveform. Both converters are controlled in stationary reference frame through proportional-resonant controllers. Experimental results demonstrate the validity and the effectiveness of the proposed topology.

A Fault-Tolerant Cascaded Switched-Capacitor Multilevel Inverter for Domestic Applications in Smart Grids

Cascaded multilevel inverters (MLIs) generate an output voltage using series-connected power modules that employ standard configurations of low-voltage components. Each module may employ one or more switched capacitors to double or quadruple its input voltage. The higher number of switched capacitors and semiconductor switches in MLIs compared to conventional two-level inverters has led to concerns about overall system reliability. A fault-tolerant design can mitigate this reliability issue. If one part of the system fails, the MLI can continue its planned operation at a reduced level rather than the entire system failing, which makes the fault tolerance of the MLI particularly important. In this paper, a novel fault location technique is presented that leads to a significant reduction in fault location detection time based on the reliability priority of the components of the proposed fault-tolerant switched capacitor cascaded MLI (CSCMLI). The main contribution of this paper is to reduce the number of MLI switches under fault conditions while operating at lower levels. The fault-tolerant inverter requires fewer switches at higher reliability, and the comparison with similar MLIs shows a faster dynamic response of fault detection and reduced fault location detection time. The experimental results confirm the effectiveness of the presented methods applied in the CSCMLI. Also, all experimental data including processor code, schematic, PCB, and video of CSCMLI operation are attached.

An Interpretation of Discrete Switching in Small-Area Semiconductors

An Interpretation of Discrete Switching in Small-Area Semiconductors

Quasi Resonant Inverter Load Recognition Method

Induction heating (IH) technology is very popular in domestic applications because of its efficiency and safe operating properties. Resonant inverter circuits are widely used in IH systems owing to their high efficiency and soft-switching capability. Among the resonant inverters used in IH systems, the single-switch quasi-resonant inverter topology is generally preferred for low-cost and low-output-power applications. Despite the low-cost advantage of the quasi-resonant inverter, the soft-switching range is quite narrow, and it is not stable depending on the electrical parameters of the load that is desired to be heated. In other words, there is a critical relationship between the electrical characteristics of the pan, turn-on, and turn-off times, which are the control parameters of the semiconductor switch, and the safe working conditions. In addition, when the importance of closed-loop control methods is evaluated together with the selection of resonant circuit elements, it is essential to determine whether the load is suitable for heating, and to determine the electrical properties of the load to provide both reliable and efficient operating conditions. This study focuses on a new load-detection method based on circuit analysis for quasi-resonant induction hobs. After determining the load parameters, the turn-on and turn-off times of the semiconductor switch were determined to obtain the lowest possible switching loss. Therefore, the boundary conditions of the semiconductor switch are maintained within these limits. The proposed method and its advantages for the switch safe operating area were theoretically examined and proved through simulations and prototype circuits.

Output Characteristics of Side-Illuminated Photoconductive Semiconductor Switch Based on High Purity Semi-Insulating 4H-SiC

Photoconductive semiconductor switch (PCSS) allowing side illumination was fabricated on high purity semi-insulating (HPSI) 4H-SiC. A 532-nm pulsed laser with variable optical energy was used to trigger the PCSS. The performance of the PCSS was characterized under the two different load conditions, 50-Ω load and 0.05-Ω, with a current viewing resistor (CVR). The PCSS exhibited significantly different output characteristics for the two different loads. The equivalent resistance of the PCSS with the 50-Ω load, which was calculated from the output voltage and current, was inversely proportional to the optical energy, but the one with a 0.05-Ω load exhibited saturation behavior with the optical energy. While the times at peak output with the 50-Ω load were similar at various optical energies, the times at peak output with the 0.05-Ω load were dependent on the optical energy. Output current oscillation was also observed after the PCSS was turned off in the case of 0.05-Ω load condition. The different output characteristics for the different load resistances were analyzed using the transient response of the equivalent circuits. The PCSS exhibited a minimum on-state resistance of 0.27 Ω with the optical energy of 8 mJ and a maximum output current of 657 A at the bias voltage of 4.8 kV. The operating voltage of the PCSS was limited by surface flashover, which caused an additional output pulse following the first output pulse.

A New Reduced Switch Seven-Level Triple Boost Switched Capacitor Based Inverter

This paper proposes a new reduced switch count seven-level triple boost inverter based on switched capacitor technique. The proposed topology has fewer number of components and has the ability of balancing the voltage across the capacitors. The structure of the proposed topology is very simple and can be easily extended to higher number of voltage levels. The generalized structure for higher number of levels is presented. The level shifted pulse width modulation approach is used to evaluate the proposed topology. In addition, design of switched capacitors and power loss calculation of semiconductor switches are provided. This proposed inverter topology is compared with the state-of-art topologies to demonstrate its superior performance. Further, thermal modelling of the topology is done in PLECS to calculate the power losses and efficiency. Finally, this proposed 7-level topology is simulated using MATLAB/Simulink and tested on experimental prototype for the performance verification and the results are included.

A Fault Current Limiting Hybrid DC Circuit Breaker

Due to the low impedance characteristic of the high voltage direct current (HVDC) grid, the fault current rises extremely fast after a DC-side fault occurs, and this phenomenon seriously endangers the safety of the HVDC grid. In order to suppress the rising speed of the fault current and reduce the current interruption requirements of the main breaker (MB), a fault current limiting hybrid DC circuit breaker (FCL-HCB) has been proposed in this paper, and it has the capability of bidirectional fault current limiting and fault current interruption. After the occurrence of the overcurrent in the HVDC grid, the current limiting circuit (CLC) of FCL-HCB is put into operation immediately, and whether the protected line is cut off or resumed to normal operation is decided according to the fault detection result. Compared with the traditional hybrid DC circuit breaker (HCB), the required number of semiconductor switches and the peak value of fault current after fault occurs are greatly reduced by adopting the proposed device. Extensive simulations also verify the effectiveness of the proposed FCL-HCB.

The effect of maintaining a high conductivity state in high-voltage GaAs diodes switched-on in the delayed avalanche breakdown mode

It is experimentally established that high-voltage GaAs diodes maintain conducting state with low residual voltage after switching to the conducting state in the delayed impact-ionization mode. The duration of the constant current in the reversely-biased structure is determined by the duration of the applied rectangular voltage pulse (up to 100 ns) and significantly exceeds drift extraction and recombination times. The discovered effect of self-supporting conducting state resembles the "lock-on" effect in optically activated GaAs semiconductor switches and S-diodes with deep centers. The effect can be explained by shock ionization in narrow collapsing Gann domains. Keywords: high-voltage GaAs diodes, "lock-on" effect.

Эффект самоподдержания проводящего состояния в обратносмещенных GaAs-диодах, переключаемых в режиме задержанного лавинного пробоя

It is experimentally established that high-voltage GaAs diodes maintain conducting state with low residual voltage after switching to the conducting state in the delayed impact-ionization mode. The duration of the constant current in the reversely-biased structure is determined by the duration of the applied rectangular voltage pulse (up to 100 ns) and significantly exceeds drift extraction and recombination times. The discovered effect of self-supporting conducting state resembles the lock-on effect in optically activated GaAs semiconductor switches and S-diodes with deep centers. The effect can be explained by shock ionization in narrow collapsing Gann domains.

Real-Time Nonlinear Behavioral Electrothermal Device-Level Emulation of IGBT on Heterogeneous Adaptive Compute Acceleration Platform

Power converter design evaluation by means of real-time simulation techniques is prevalent, although it is mostly restricted to simple power semiconductor switch models that exclude device-level physical details. In this work, the nonlinear high-order electro-thermal model of the Insulated-gate bipolar transistor (IGBT) is developed and then deployed onto the heterogeneous digital hardware for real-time implementation. As the complexity of the nonlinear behavioral model (NBM) of the IGBT poses a significant computational burden on real-time hardware emulation, machine learning (ML) methodology is utilized so that the trained model can reproduce the characteristics of its original counterpart as much as possible and then it is implemented on the Adaptive Compute Acceleration Platform (ACAP), which composes of the processing system (PS), programmable logic (PL), and Artificial Intelligent Engine (AIE). The vector multiplication feature of the AIE caters to mathematical operations of the ML-based model particularly well and consequently enables it to be executed in real-time with remarkable speedup over the original model with which matrix inversion is otherwise mandatory. Finally, the validation for real-time device-level results and system-level results of a multi-converter system is provided by SaberRD® and MATLAB/Simulink®.

On-Line Multistep Predictive Spectral Control of the Distortion in Switched-Mode Converters

In automotive power electronics, distortion and electromagnetic interference (EMI) generated by the switching action of power semiconductors can be a significant challenge for the design of a compact, lightweight vehicle. As semiconductor switching frequencies increase, e.g., through the introduction of new materials, such as gallium nitride and silicon carbide, this problem becomes more severe. We present a control scheme for an automotive dc-to-dc converter that reduces the EMI generated by shaping switching distortion predictively at the run time. The multistep model-predictive control scheme chooses the subsequent switching state that optimizes the output spectrum according to predefined criteria. To achieve real-time operation, it evaluates the possible switching state candidates for the next modulation step without explicitly solving a single Fourier transform. In addition, the switching rate and voltage ripple are controlled in a single unified control law. We present and experimentally validate that the control scheme can indeed run at real time already with currently available mid-range hardware. The results demonstrate that the largest spectral peak of the switching distortion can be decreased by 48 dB compared to conventional pulse-width modulation. Furthermore, spectral gaps can be implemented in the output distortion and altered in real-time, allowing certain frequency bands—e.g., bands used by other sensitive electronics such as sensors, communication busses, or tuners—to be kept free of EMI from the converter’s switching actions.

The Experimental Evaluation of Simple Bidirectional DC/DC Converter with Snubber Compensation for Electric Vehicle Application

This research discusses the implementation of a buck-boost converter which is also known as a Bidirectional DC/DC Converter (BDC) in electric vehicles with a specific focus on electric All-Terrain Vehicles (ATV). The BDC circuit was used to integrate the main battery of the ATV (Li-Po) with the secondary battery (a 25V max./8 Farad Supercapacitor bank). This is to ensure the main battery of the ATV motor safer from unstable output load currents through the charging and discharging mechanism facilitated by BDC in order to ensure it has a longer lifetime. This discussion is more focused on the charging mechanism which occurs when the BDC is in buck mode (36V to 18 V). Meanwhile, the DC motor was used as the load inductor in this BDC circuit. It is also important to note that an interruption in the current flowing either due to a switch or other components has the ability to cause a voltage or current spike in the semiconductor switch component. Therefore, a special circuit was required to be connected to the main circuit to reduce interruption and also indicates the role of the snubber circuit in reducing the spike. This paper is more highlighted on voltage spike reduction. Moreover, LTSpice simulation was applied to verify the BDC circuit design, and the results obtained were compared with a real laboratory measurement based on the ability to change the Duty Cycle on the Vout of the BDC circuit for the charging mechanism. The determination of the desired Vout was followed by a change in the parameters of the BDC circuit such as input voltage, inductor value, switching frequency, duty cycle, and power supply configuration to determine their impact on the Vout of BDC, Spike, and MOSFET's temperature. The experiments showed that the Snubber circuit was able to compensate for voltage fluctuations in the MOSFET.

High voltage gain resonant DC-DC converter with vm cells for renewable sources applications

Due to the widespread impact of renewable energy resources on high power density grids, transmission at the DC regime has been considered more useful than AC transmission systems. The findings of this study suggest the application of a ripple-free input current resonant DC-DC converter possessing high voltage gain and high efficiency as being more suitable for renewable energy systems. Applying variable switching frequency control systems, the proposed converter discussed here is generally operated at the critical conduction mode for soft switching of the semiconductor switches. Using the resonance mechanism, the proposed converter causes a decrease in the turn-on loss of the power switch without needing additional semiconductor gadgets. It leads to a reduction in the reverse-recovery losses of the rectifying diodes. Also, analysis and design consideration of the proposed converter are presented with excellent performance.

All-solid-state pulsed current injection source based on the light initiated multi-gate semiconductor switches.

To study the damage and protection mechanism of the transient electromagnetic pulse to the cables of the electronic equipment under test, an all-solid-state pulsed current injection source with light initiated multi-gate semiconductor switches is developed. The output peak current range of the prepared all-solid-state pulsed current injection source was 0.1-1kA, the risetime was 18ns, and the pulse width was 520ns. In addition, the waveforms of the output peak current were consistent.

철도 차량용 배터리 충전을 위한 LLC 공진형 컨버터의 SiC FET와 Si FET의 병렬 연결에 관한 연구

Wide-Band-Gap (WBG) switching semiconductor has been improved for higher efficiency and higher power density. Especially, SiC FET is the most attractive switching semiconductor for mid-voltage and high power applications, such as, railway transportation. Its desired features for high power converter are low on-state resistance, thermal stability, no reverse recovery, high switching speed, and so on. However, faster switching speed derives higher dv/dt of drain-source voltage, then this result in larger voltage ringing and worse switching noise. In this paper, parallel configuration of SiC FET and Si FET is proposed to suppress voltage ringing and minimize switching noise. Based on the characteristics of output capacitances of both SiC and Si FETs, the switching performances of single SiC FET and parallel connection of SiC/Si FETs are compared of voltage ringing and switching noise in LLC resonant converter for 10kW battery charging module of railway transportation.

Design of High-Frequency ZVS Full-Bridge Power Converter for Photovoltaic Applications

This paper presents the design of a high-frequency Zero Voltage Switching (ZVS) full-bridge converter with a phase-shifted driving signal for photovoltaic applications. According to the rapid development of power electronics technology, the smart power converter could provide high-power capacity with the high-frequency operation and achieve high energy delivery to the load. This power converter could also reduce the size of the transformer compared to the same power rating. The transformer has been developed using resonant technique and selecting the optimal switching frequency whereby the power converter could reduce switching loss and improve the system efficiency. The phase-shifted modulation switching technique has been selected to drive the power semiconductor switches of a full-bridge power converter based on the switching loss minimization method. The desired output voltage has been controlled using a closed-loop controller under a loop gain stability margin. The simulation results have showed that the output voltage could be controlled to the desired constant when the input voltage has changed from 370 VDC to 400 VDC. The output voltage of the power converter could be controlled at a constant of 24 VDC. Therefore, the proposed study has showed the effectiveness of the phase-shifted ZVS full-bridge power converter for photovoltaic applications such as the battery charging system. This power converter could operate at the desired voltage system and reduce the sizing of the power converter under high-performance efficiency.

Asymmetrical eleven‐level inverter topology with reduced power semiconductor switches, total standing voltage and cost factor

Voltage source multilevel inverters (MLI) is widely utilized in medium and high-power applications due to their advantages. Here, an 11-level, asymmetrical multilevel inverter topology is proposed. The topology utilizes four unidirectional switches, three bidirectional switches along with two dc sources. The proposed configuration of switches and the concept of the dc-link capacitor is utilized to generate eleven level output voltage. The reduced number of components such as power switches and DC sources, lower control complexity due to capacitors' self-balancing nature, and low total standing voltage (TSV) are the critical features of the proposed topology. Moreover, a reliability assessment of the topology shows that the topology has a high mean time to fault (MTTF), which makes it robust and reliable. Matlab/Simulink environment is used to develop a simulation model of the proposed topology, while PLECS is used for the thermal modelling and analysis of the converter. A prototype is developed and tested in the laboratory to validate the performance for different loading conditions. The proposed topology can be cascaded to produce the ‘n’ number of levels. The critical comparison of the proposed topology shows that the proposed circuit has advantages over other compared topologies.

Synchrotron X-ray topographic characterization of dislocations in 6H-SiC axial samples

Wide bandgap semiconductor, 6H-SiC, is being applied in photoconductive semiconductor switches (PCSS) due to its semi-insulating properties. The behavior of the dislocations in 6H- SiC under the application of voltage and laser in such devices is of particular interest. In this study, synchrotron X-ray transmission topography, grazing incidence topography and rocking curve topography are applied to characterize the types and distribution of defects in (1 1 –2 0) oriented wafers. Threading edge dislocations (TED), threading screw dislocations (TSD), threading mixed dislocation (TMD) and basal plane dislocations (BPD) in 6H-SiC axial samples are revealed in the X-ray topographs. TEDs are observed to be more likely off c-axis compared to TSDs/TMDs. Contrast features of BPDs differ depending on their Burgers vectors and orientation with respect to wafer surface on rocking curve topographs and grazing incidence topographs. Applying ray tracing simulations, the configurations of BPDs can be determined, and the threading dislocations (TED, TSD and TMD) can be distinguished in grazing incidence topographs. The understanding of the nature and the distribution of these dislocations will help predict their propagation and movement under the application of voltage and laser, providing guidance for device fabrication.

A Voltage-Fed Soft-Switched Push–Pull Topology With Phase-Shifted Power Transfer Using Coupled LC Snubber

This article proposes a voltage-fed zero-voltage-switched topology based on the push-pull converter. The proposed converter uses the leakage inductance of the transformer to transfer power from input to output. Phase-shift modulation strategy is used to control the flow of this power. A coupled LC regenerative snubber-based energy recovery circuit reclaims the trapped energy in the leakage inductance. The snubber circuit also ensures soft-switched operation and reduces the voltage stress across the semiconductor switches. The power-flow equation is characterized and experimentally verified for the proposed converter. The gate control signals are implemented using an field-programmable gate array (FPGA). A 240-W prototype validates the steady-state behavior and snubber design equations.