Switching Rise Time Research Articles

Review of High Voltage Pulsed Power Supplies and Power Electronics in Pulse Power Generation

Recently, pulse-shaped power supplies have become more popular. Pulsed power is versatile and useful as a supply method since it can take several shapes and has many pulse characteristics. The release of electrons, protons, and neutrons from an atom and the synthesis of molecules to generate ions or other molecules require a lot of immediate energy. Pulsed power is needed for decomposition, molecular fusion and material joining, radiation generation (e.g., electrons, lasers, radar), explosive processes for concrete recycling, wastewater and exhaust gas treatment, and material surface treatments. Industrial and environmental applications require pulsed power, which requires efficient and adaptive pulse modulators. Higher-quality repeating pulses are needed for plasma fusion and laser weapons. Marx Generators, Magnetic Pulse Compressors, Pulse Forming Networks, and Multistage Blumlein Lines have several uses. Pulse modulators use spark gap and hydrogen thyratron gas/magnetic switching technologies for their high voltage tolerance and low-rise times. These creatures are inefficient, unreliable, repetitious, and short-lived. These devices are heavy, bulky, and expensive. Solid-state switching technology can replace conventional devices, improving pulse supply. High-frequency switching repeats the pulsed power supply. These items are compact, efficient, affordable, reliable, and durable. Solid-state transistor applications may not meet switch voltage ratings and rise time constraints. Various power electronics configurations can produce solid-state high-voltage pulses.

Ultrafast and High Extinction Ratio 1×4 Electro-Optical Switch Based on Cascaded Dual-Output MZI

We propose and fabricate an ultrafast and high extinction ratio 1×4 optical switch based on a cascade, dual-output Mach–Zehnder interferometer (MZI) on the lithium niobate platform. The optical switch consists of cascaded, identical, dual-output MZI structures, and each of them includes a Y-branch waveguide, two parallel interference arms (electrode action area), and a 3 dB directional coupler. Four output optical paths can be switched through three groups of electrode hierarchical modulation. The test results of the fabricated device show that the insertion loss of each port is less than 7.1 dB and that the maximum extinction ratio is higher than 39.3 dB. The optical switch can achieve a high extinction ratio greater than 20 dB within the 50 nm wavelength range. The measured half-wave voltage is less than 4.13 V, and the minimum switching rise and fall times reach 125 ps and 250 ps, respectively. This result shows that the proposed and fabricated 1×4 integrated optical switch on a lithium niobate platform has the advantages of a fast response rate, high extinction ratio, and low switching voltage.

Switching Wave Characteristics Affecting the Life of Type II Machine Turn Insulation

In this article, the impact of the waveform switching frequency (SWF), overshoot (OS), and rise time on the time-to-failure and the endurance of Type II machine insulation is investigated. Reference life curves at 1 and 4 kHz SWF are derived utilizing a unipolar repetitive square-impulse of 15% OS and 300 ns rise time. The effects of the impulse OS and rise time in the ranges of 0%–30% and 400–600 ns are also evaluated and reflected on the established reference life curves. Based on the endurance test results and the reported time-to-failure data, it is evident that the turn insulation is subjected to additional stress factors when energized by an inverter supply as opposed to the stresses exhibited by sinusoidal waves. This indicates an incomparable aging rate between the two types of waveforms, even at similar peak voltages applied, resulting in inadequate use of sinusoidal supply to qualify inverter-fed machines. Moreover, the OS component of the waveform is found to have a substantial impact on the endurance of turn insulation apart from the jump voltage impact, and therefore, is identified as a significant factor influencing the life of turn insulation independent of other factors. Moreover, the reported results of the time-to-failure analysis advocate a nonlinear relationship between the SWF and the life of turn insulation, whereas the waveform rise time is found to have a negligible impact within the considered range in this study.

A Review of Modeling and Mitigation Techniques for Bearing Currents in Electrical Machines With Variable-Frequency Drives

The converter switching in variable-frequency drives can generate high frequency common mode voltage between the machine winding and the converter ground, leading to high frequency parasitic currents which can flow through the machine bearings unless precautions are taken in design and installation. These parasitic and unintended currents in the bearings cause deterioration of the lubrication film and surface damage to the rolling elements of the bearings. These problems will be exacerbated as wide-bandgap semiconductors with faster switching rise times start becoming more widespread in variable-frequency drives. This paper reviews the modelling and mitigation techniques of high frequency bearing currents in inverter fed AC drives. It aims to provide a solid base for the research community to further understanding the bearing currents phenomenon and helping to find novel improved technique for their mitigation and measurement.

Design of W-band PIN Diode SPDT Switch with Low Loss

A W-band PIN diode single pole double throw (SPDT) switch with low insertion loss (IL) was successfully developed using a hybrid integration circuit (HIC) of microstrip and coplanar waveguide (CPW) in this paper. In order to achieve low loss of the SPDT switch, the beam-lead PIN diode 3D simulation model was accurately established in Ansys High Frequency Structure Simulator (HFSS) and the W-band H-plane waveguide-microstrip transition was realized based on the principle of the magnetic field coupling. The key of the proposed method is to design the H-plane waveguide-microstrip transition, it not only realizes the low IL of the SPDT switch, but also the direct current (DC) bias of the PIN diode can be better grounded. In order to validate the proposed design method, a W-band PIN diode SPDT switch is fabricated and measured. The measurement results show that the IL of the SPDT switch is less than 2 dB in the frequency range of 85 to 95 GHz, while the isolation of the SPDT switch is greater than 15 dB in the frequency range of 89.5 to 94 GHz. In the frequency range of 92 to 93 GHz, the IL of the SPDT switch is less than 1.65 dB, and its isolation is higher than 22 dB. Switch rise time and switch fall time of the SPDT switch are smaller than 29ns and 19ns, respectively. Good agreement between the simulations and measurements validates the design method.

Low-power-consumption polymer Mach-Zehnder interferometer thermo-optic switch at 532 nm based on a triangular waveguide.

We designed and fabricated a Mach-Zehnder interferometer (MZI) thermo-optic switch with an inverted triangular waveguide. The inverted triangular waveguide achieves a fundamental mode in a large waveguide dimension, which can reduce the coupling loss and increase the extinction ratio. The triangular waveguide-based switch was simulated and presented higher heating efficiency and lower power consumption than that of the traditional rectangular waveguide-based switch. Compared with the traditional rectangular waveguide-based device, the power consumption of the proposed device is reduced by 60%. Spacing photobleaching was introduced to fabricate the inverted triangular waveguide and adjust the refractive index to minimize the mode number. The insertion loss of the typical fabricated device with a 2 cm length is about 7.8 dB. The device shows an extinction ratio of ∼8.1dB at 532 nm with a very low power consumption of 2.2 mW, and the switching rise time and fall time are 110 and 130 µs, respectively. The proposed single-mode waveguide and low-power-consumption optical switch have great potential applications in visible optical communication fields such as wavelength division multiplexing and mode-division multiplexing.

Polymeric Waveguide MZI Thermo-Optic Mode Switch Based on Asymmetric Directional Coupler

We propose and fabricate a polymeric thermo-optic mode switch based on a Mach-Zehnder interferometer (MZI) by connecting two asymmetric directional couplers formed with a single-mode waveguide (SMW) and a two-mode waveguide (TMW). Thin-film heaters were deposited on the arms of the MZI to realize the switching function. The LP01 mode in the SMW and the LP11a mode in the TMW can be converted to each other by driving the voltage supplied to the heater. Our typical fabricated device with polymer material shows extinction ratios higher than ~11 dB in the C-band. The switching power measured at 1550 nm is lower than 10 mW and the switching rise time and fall time are 540.0 μs and 440.0 μs, respectively. The device could find applications in reconfigurable mode-division-multiplexing systems.

Low-Power Broadband Thermo-Optic Switch With Weak Polarization Dependence Using a Segmented Graphene Heater

We propose and demonstrate experimentally a 2 × 2 polymer optical waveguide thermo-optic switch, featuring wide bandwidth, low power, and weak polarization dependence. Our proposed switch is based on Mach-Zehnder interferometer (MZI) configuration and driven by a segmented graphene electrode heater formed with four identical small heaters in parallel. The use of the parallel graphene electrode heater can improve the heating efficiency by placing the heater in direct contact with the waveguide core and achieve a low driving voltage. Unlike the works reported previously, the graphene electrode heater used here achieves negligible light absorption for both the transverse electric (TE) and the transverse magnetic (TM) polarizations and, hence, weak polarization-dependent operation because a large cross-sectional square waveguide structure without upper cladding is employed. Meanwhile, two asymmetric directional couplers are employed to achieve broadband operation. Our fabricated device, which has a length of 9.5 mm, exhibits extinction ratios higher than ∼13.5 dB over a wavelength range of 1530 – 1605 nm and higher than ∼26 dB at 1561 nm for all channels. The switching powers are ∼3.30 and 3.12 mW for the TE and TM polarizations, respectively. The insertion losses are lower than 10.5 dB for all channels. The rise and fall time of switching are 0.98 and 0.52 ms, respectively.

Low power consumption thermo-optic switch formed by an integrated processing method.

In this paper, an integrated processing method was demonstrated to fabricate the polymer-based thermo-optic (TO) switch with low power consumption. The characteristic parameters of the switch were carefully designed and simulated. The air trench structure was exploited to reduce the power consumption, which can be formed with the waveguide simultaneously by the integrated processing method. Moreover, the introduced polymer/silica hybrid waveguide structure can also improve the response time of the device. A typical fabricated switch presented a low switching power of 5.2mW. The measured switching rise time and fall time are 192.2 and 201.1μs, respectively.

Thermo-Optic Mode Switch Based on an Asymmetric Mach–Zehnder Interferometer

A thermo-optic waveguide mode switch based on an asymmetric Mach–Zehnder interferometer (MZI) is demonstrated. A metal heater is deposited on one arm of the asymmetric MZI to implement switching between the LP01 and LP11 a modes. The polymer/SiO2 hybrid waveguide structure is adopted to decrease the power consumption and switching time. The fabricated device shows a mode extinction ratio of 10.5 dB with a power consumption of 15.4 mW at 1550 nm. The operation bandwidth ranges from 1525 to 1615 nm. The rise time and fall time of mode switching are 71.5 and $140.3~\mu \text{s}$ , respectively. This device has potential in configurable mode-division multiplexing systems.

Low-power total internal reflection thermo-optic switch based on hybrid SiON-polymer X-junction waveguides.

We propose and demonstrate a low-power 2×2 total internal reflection thermo-optic switch based on an X-junction configuration formed with a silicon oxynitride (SiON) core and polymer cladding. Unlike X-junctions reported thus far, our proposed configuration features a slot formed on the center of the X-junction and filled with polymer cladding. With such a configuration, the opposite thermo-optic characteristics of SiON and polymer and, hence, heat utilization efficiency can be fully utilized. Our fabricated proof-of-principle switch shows extinction ratios of larger than 15.34dB and switching powers of less than ∼59.6 mW. The rise time and fall time of switching are 1.42 and 0.85ms, respectively. The insertion losses are less than 10.6dB for all channels, and the polarization-dependent loss is ∼0.3 dB.

High-speed electro-optic switch based on nonlinear polymer-clad waveguide incorporated with quasi-in-plane coplanar waveguide electrodes

Nonlinear optical (NLO) polymer is a promising material for active waveguide devices that can provide large bandwidth and high-speed response time. However, the performance of the active devices is not only related to the waveguide materials, but also related to the waveguide and electrode structures. In this paper, a high-speed Mach–Zehnder interferometer (MZI) type of electro-optic (EO) switch based on NLO polymer-clad waveguide was fabricated. The quasi-in-plane coplanar waveguide electrodes were also introduced to enhance the poling and modulating efficiency. The characteristic parameters of the waveguide and electrode were carefully designed and simulated. The switches were fabricated by the conventional micro-fabrication process. Under 1550-nm operating wavelength, a typical fabricated switch showed a low insertion loss of 10.2 dB, and the switching rise time and fall time were 55.58 and 57.98 ns, respectively. The proposed waveguide and electrode structures could be developed into other active EO devices and also used as the component in the polymer-based large-scale photonic integrated circuit.

High-speed electro-optic switch using buried electrode structure in polymer Mach–Zehnder waveguide

A low-cost and high-speed electro-optic (EO) switch using the guest–host EO material Disperse Red 1/Polymethyl Methacrylate (DR1/PMMA) was designed and fabricated. The DR1/PMMA material presented a low processing cost, an excellent photostability and a large EO coefficient of 13.1 pm/V. To improve the performance of the switch, the in-plane buried electrode structure was introduced in the polymer Mach–Zehnder waveguide to improve the poling and modulating efficiency. The characteristic parameters of the waveguide and the electrodes were carefully designed and the fabrication process was strictly controlled. Under 1550 nm, the insertion loss of the device was 12.7 dB. The measured switching rise time and fall time of the switch were 50.00 ns and 54.29 ns, respectively.

A high-pressure, flowing liquid dielectric pulse-forming line

Liquid dielectrics as switching media are of special interest because of their higher breakdown field strength than that of compressed gases, especially in the case of ultrafast nanosecond charging, better thermal management, and removal of eroded electrode material while circulating through the switch. The pulse-forming line (PFL) presented here is designed to operate together with our own Marx generators. It is comprised of a peaking switch with, compared with the previous design, an increased high-pressure operability up to 4000 kPa and an additional annular crowbar electrode. The geometry of the peaking switch electrodes was optimized with computational fluid dynamics simulations, in order to ensure a laminar liquid flow through the switch with flow rates up to 55 mL/s. Galden-type HT270 perfluoropolyether fluid was chosen as the liquid dielectric. The breakdown field strength showed a significant pressure dependency, which is due to the high gas solubility of Galden. At a pressure of 3950 kPa and a gap distance of 0.25 mm, a maximum breakdown field strength of 14.3 MV/cm has been reported, an increase of 360% compared with the breakdown field strength of 3.8 MV/cm at atmospheric pressure. The minimum peaking switch rise time was 220 ps; the corresponding peak voltage rise time amounted to $1.2\times 10^{15}$ V/s. With the addition of the crowbar electrode, an ultrashort monopolar output pulse with a characteristic pulsewidth of 210 ps was achieved. First, the results of a repetitive operation of the PFL driven by an inductive Marx generator will be discussed.

Nonblocking 3 × 3 polymer thermo-optic switch array based on total-internal-reflection effect.

A nonblocking 3×3 polymer thermo-optic (TO) switch array based on the total-internal-reflection (TIR) effect is demonstrated. The switch array consists of three 2×2 TIR TO switch elements with a total device length of 15.5 mm, and achieves nine switching states with no more than one switch element working. The fabricated 3×3 TO switch array shows excellent switching performance with low crosstalk for all switching states of less than -20 dB. The power consumption of each switch element is below 53 mW, and the switching rise time and fall time are ∼450 and 550 μs at 1550 nm wavelength, respectively.

Fluorinated photopolymer thermo-optic switch arrays with dielectric-loaded surface plasmon polariton waveguide structure

Novel polymer thermo-optic switch arrays were successfully designed and fabricated based on dielectric-loaded surface plasmon polariton waveguide (DLSPPW) structure. Highly fluorinated low-loss photopolymers and organic–inorganic grafting materials were used as the waveguide core and cladding, respectively. The low absorption loss characteristics and excellent thermal stabilities of the core and cladding materials were obtained. The proposed DLSPPW model was included of fluorinated polymer ridge with 4 × 4 μm2 size loaded on 60-nm thin gold stripe electrode heaters, organic-inorganic grafting material cladding and PMMA substrate. The operation of the device at signal wavelengths is controlled via the thermo-optic effect by electrically heating the gold stripes of dielectric-loaded surface plasmon polariton waveguides. The optimized structural properties of dielectric-loaded surface plasmon polariton waveguides were provided. The propagation loss of a 4-μm wide straight DLSPPW was measured as 0.55 dB∕cm at 1550 nm wavelength. The insertion loss of the device was measured to be about 4.5 dB. The switching rise and fall time of the device applied by 200 Hz square-wave voltage were obtained as 287.5 μs and 370.2 μs, respectively. The switching power was about 5.6 mW, and the extinction ratio was about 13.5 dB. The flexible low-loss multi-functional waveguide switch arrays are suitable for realizing large-scale optoelectronic integrated circuits.

A DC-DC Circuit Using Boost Converter for Low Voltage Energy Harvesting Application

A DC-DC step-up voltage converter is designed to convert a very low voltage supply, 35 mV such as from the thermal energy source from body heat. The converter can generate an output voltage up to 210 mV, approximately six imes its initial input voltage over a frequency of 36 GHz. The effect of switching transistors, inductor current, rise and fall time is also highlighted. The circuit operates using 2 µH inductor and 0.01 fF load capacitor, is simulated using PSpice Simulation tool. This voltage converter is suitable for energy harvesting application in implanted electronic devices.

Optimized design and fabrication of nanosecond response electro–optic switch based on ultraviolet-curable polymers**Project supported by the National Natural Science Foundation of China (Grant Nos. 61177027, 61107019, 61205032, and 61261130586).

A nanosecond response waveguide electro-optic (EO) switch based on ultraviolet (UV) sensitive polymers of Norland optical adhesive (NOA73) and Dispersed Red 1 (DR1) doped SU-8 (DR1/SU-8) is designed and fabricated. The absorption properties, refractive indexes, and surface morphologies of NOA73 film are characterized. The single-mode transmission condition is computed by the effective index method, and the percentage of optical field distributed in EO layer is optimized to be 93.78 %. By means of spin-coating, thermal evaporation, photolithography, and inductively coupled plasma etching, a Mach–Zehnder inverted-rib waveguide EO switch with micro-strip line electrode is fabricated on a silicon substrate. Scanning electron microscope characterization proves the physic-chemical compatibility between NOA73 cladding and DR1/SU-8 core material. The optical transmission loss of the fabricated switch is measured to be 2.5 dB/cm. The rise time and fall time of switching are 3.199 ns and 2.559 ns, respectively. These results indicate that the inverted-rib wave-guide based on UV-curable polymers can effectively reduce the optical transmission loss and improve the time response performance of an EO switch.

Using fast moving electrode to achieve overvoltage breakdown of gas switch stressed with high direct voltages.

A small-scale fast risetime gas switch attached to a 50 Ω pulse forming line is tested. It includes a fast moving electrode and a fixed electrode. For the applied direct voltages, such as 2.8 kV, 2.0 kV, and 1.0 kV, the risetimes of this switch are tested to be ∼3.8 ns, ∼2.3 ns, and ∼1.1 ns, respectively, while the risetimes of a switch with two fixed electrodes are about ∼10.1 ns, ∼9.0 ns, and ∼3.6 ns. The results of high-speed photography and laser interferometry reveal that the moving electrode will obviously shorten discharge spark length but almost will not change the inter-electrodes gas pressure. The reason of shortening spark length is the existence of the discharge time delay of gas switch. After moving to the static breakdown spacing, the fast moving electrode will move on for an additional distance within the discharge time delay, which makes gas switch achieve overvoltage breakdown under high direct voltages and therefore leads to shorter spark length and faster switch risetime.

Time Response of a Microelectromechanical Silicon Photonic Waveguide Coupler Switch

Time response of a silicon photonic nanowire-waveguide microelectromechanical switch is studied by measuring optical output and analyzing mechanical and electrical dynamics. The switching mechanism is based on the gap variation of a directional waveguide coupler consisting of 400-nm-wide and 260-nm-thick waveguides. One of the coupler waveguides is moved by an ultrasmall comb actuator. A theoretical model is proposed by combining the mechanical motion and the electrical circuit response of the switch. By analyzing the model, an optimum condition for switching rise time is obtained to be ~10 μs, where the mechanical oscillation is suppressed by the driving electrical circuit with a large resistance. The rise time measured from the optical output intensity was 18 μs.