Turn-on Switching Research Articles

Bio‐Voltage Diffusive Memristor from CVD Grown WSe2 as Artificial Nociceptor

AbstractMemristors have emerged as a promising candidate to mimic the human behavior and thus unlocking the potential for bio‐inspired computing advancement. However, these devices operate at a voltages which are still far from the energy‐efficient biological counterpart, which uses an action potential of 50–120 mV to process the information. Here, a diffusive memristor is reported from synthetic WSe2 fabricated in Ag/WSe2/Au vertical device geometry. The devices operate at bio‐voltages of 40–80 mV with Ion/Ioff ratio of 106 and steep switching turn ON and OFF slopes of 0.77 and 0.88 mV per decade, respectively. The power consumption in standby mode and power per set transition are found to be 10 fW and 64 pW, respectively. Further, the diffusive memristors are utilized to emulate the nociceptor, a special receptor for sensory neurons that selectively responds to noxious stimuli. Nociceptor in turn imparts a warning signal to the central nervous system which then triggers the motor response to take precautionary actions to prevent the body from injury. The key features of a nociceptor including “threshold”, “relaxation”, “no‐adaptation” and “sensitization” are demonstrated using artificial nociceptors. These illustrations imply the feasibility of developing low‐power diffusive memristors for bio‐inspired computing, humanoid robots, and electronic skins.

Multiphase LLC DC-Link Converter with Current Equalization Based on CM Voltage-Controlled Capacitor

In this study, a current-equalization technology utilizing a variable-capacitance technique for a multiphase inductor–inductor–capacitor (LLC) converter is studied. Accordingly, the proposed method involves adjusting the resonant capacitance of the LLC resonant converter to balance the currents between phases. This is achieved primarily by biasing ferroelectric multilayer ceramic capacitors (MLCCs) through a step-down circuit and a common-mode bias structure. These ferroelectric MLCCs serve as the resonant elements, allowing for variable capacitance by leveraging capacitance sensitivity to their trans voltages. This approach provides additional control flexibility to the resonant circuit. Furthermore, since each phase operates independently, the circuit can be scaled to accommodate any number of phases. Moreover, all switches in the circuit have zero-voltage switching (ZVS) turn-on, minimizing switching losses. This study initially analyzes and evaluates the proposed common-mode bias variable capacitance technique and the corresponding operational principles. Subsequently, a two-phase LLC experimental circuit based on a field-programmable gate array (FPGA) digital controller is utilized to assess current equalization and efficiency. That is to say, this experimentation aims to validate the effectiveness of the current-equalization variable-capacitance technique in an LLC resonant converter.

Anti-counterfeiting applications of antimony-doped zero-dimensional indium halide with temperature-responsive broad emission

While spatial-resolved luminescent anti-counterfeiting technology has reached maturity, achieving rapid responsiveness and exceptional fatigue resistance remains a challenge for high-security-level applications. Temperature-based multi-stimuli-responsive luminescent solid-state materials offer a promising solution to meet these requirements. In this study, we present a dual stimuli-responsive photoluminescence (PL) switching system that depends on both temperature and excitation wavelength, utilizing a Zero-Dimensional (0D) (PMA)4In0.98Sb0.02Cl7·H2O (PMA = benzylamine). Notably, (PMA)4In0.98Sb0.02Cl7·H2O exhibits orange broad-band emission at room temperature under both low-energy (365 nm) and high-energy (254 nm) irradiation. At 80 K, green light emission is observed under high-energy irradiation (254 nm), transforming into red emission when excited with low-energy wavelength (365 nm) at the same temperature. Moreover, the (PMA)4In0.98Sb0.02Cl7·H2O both in powder and film states demonstrate excellent stimuli-responsive performance, including short response times and superior cyclic reversibility. Therefore, this 0D (PMA)4In0.98Sb0.02Cl7·H2O can serve as a novel quarter-fold turn-on and tuning luminescent switch for encryption/decryption under the stimuli of temperature and excitation with rapid response and excellent fatigue resistance.

High-Voltage Gain Ripple-Free Resonant DC–DC Converter Using Active Voltage-Quadrupler

This paper presents a high-voltage gain ripple-free resonant DC/DC converter using an active voltage-quadrupler. By incorporating an active voltage-quadrupler at the secondary side of the transformer, the circuit achieved a very high-voltage gain. Without using extra input inductors, the inherent dual transformer plus interleaved active-clamped circuit operating with a fixed duty-ratio of 0.5 generate a ripple-free input current, which extends the lifetime of the fuel cell and shrinks the size of the input capacitive filter. This asymmetric structure of the active-clamp circuit requires an extra dead time for one of the secondary-side switches to achieve zero-voltage switching (ZVS) turn-on. After the extra dead time for one of the secondary-side switches is applied, all power components of the active voltage quadrupler cell are turned on and off with soft switching. The resonant capacitor voltages are unbalanced due to the extra dead time, but they are compensated by applying different secondary-side duty ratios. The operating principle and steady-state characteristics of the proposed converter were analyzed in detail. We built a 1-kW/700-V prototype that copes with 48-72 V inputs, and tested to verify the theoretical analysis.

An Efficient Interleaved Bidirectional DC–DC Converter With Shared Soft-Switching Auxiliary Circuit

A soft-switching interleaved bidirectional DC-DC converter, which is the combination of the conventional one and the introduced auxiliary circuit, is proposed in this paper. The auxiliary branch composed of a capacitor, an inductor and two switches connected in series, is attached to the switching nodes of the two phases and serves them in a shared manner. Due to voltage continuity of the auxiliary capacitor, the zero-voltage switching (ZVS) condition is realized nearly for primary switches at turn-off. With the designed driving sequences, the current gradually flows through auxiliary inductor ahead of primary switches turn-on, which is key to realizing ZVS condition for the switches. Moreover, the limited current slope guarantees the zero-current switching (ZCS) condition for auxiliary switches. Operating principle in buck mode is elaborated and design guideline is presented. Considering the parasitic resonance between the auxiliary inductor and the output capacitors of auxiliary switches, a clamping structure is given. A 1.2-kW prototype of the proposed converter is built and tested. The experimental results show the high performance.

GaN-Based 4-MHz Full-Bridge Electrosurgical Generator Using Zero-Voltage Switching Over Wide Load Impedance Range.

In this article, a 4-MHz full-bridge inverter system for an electrosurgical generator (ESG) is presented with zero-voltage switching (ZVS) turn-on over a wide load impedance range based on wideband gap material gallium nitride (GaN) technology. The proposed resonant circuit is used for impedance matching and limits the current when the load is short state while performing ZVS over a wide load impedance range. It also ensures high power performance at high frequencies for electric surgery. The implementation methods of the GaN switch at 4 MHz with high output performance are guided by the low inductance from the gate-driver output to the switch gate node and the effective heating management structure of the GaN-based inverter. The proposed generator achieved a maximum output power of 99 W to the load and a maximum overall efficiency of 89% with overcurrent of <3 A at short state of the load. The ESG can generate constant output power of 20, 50, 70 W through mode control of 2, 5, and 7 s. The overcurrent Moreover, the proposed generator is tested on porcine tissue samples to verify its effectiveness as an ESG.

Soft-Switching Resonant DC Transformer for Class-D Switching Amplifier With Symmetric Bipolar Outputs

In this letter, soft-switching resonant DC transformer (DCX) for the class-D switching amplifier with the symmetric bipolar outputs is proposed. The proposed DCX consists of a single transformer primary inverter circuit and two transformer secondary dual series resonant half-bridge rectifier circuits, which reduces the voltage stress of the rectifier diodes. In the proposed DCX, the duty cycle of the primary inverter circuit is 0.5, and the symmetric bipolar output voltage gains only depend on the transformer. By dual series resonance between the leakage inductance and the output resonant capacitors, ZVS turn-on of switches and ZCS turn-off of the diodes can be achieved, which improves the overall efficiency. The characteristic of the DCX is elaborated and analyzed in this letter. Finally, a 60 W prototype is established and the experimental verified the theoretical analysis of the proposed DCX.

A General Purpose Transformerless Charging System Based on Fully Bridgeless Canonical Switching Cell High-Quality Rectifier for LVEVs

A general purpose transformerless charging system (CS) targeted for various class of low voltage electric vehicles (LVEVs) (24 V–72 V), is designed, analyzed, and implemented in this work. The presented CS employs a fully bridgeless canonical switching cell (FBLCSC) improved power quality rectifier (IPQR) at its front end stage, and a high gain buck (HGB) DC-DC converter at its back end stage. At front end, the presented FBLCSC IPQR does not employ diode bridge rectifier (DBR) circuit, and therefore, ensures better conversion efficiency while operating over wide range of AC mains conditions (110 V–265 V). Further, compared to conventional buck-boost derived IPQRs, the presented IPQR employs minimum component count and maintains low current ripples at its AC and DC ends. On one side, the minimum component count shrinks down the cost, size and losses of the complete CS; low current ripples characteristic on the other side lowers the size of AC and DC end filtering elements. Notably, the FBLCSC IPQR exhibits auto unity power factor operation during discontinuous current mode (DCM) design, and thus, facilitates simple and low cost control architecture. Apart from control simplicity, the DCM operation of FBLCSC IPQR leads to negligible switch turn-on and diode reverse recovery losses. Likewise, at the back end stage, the HGB converter realizes a transformerless DC-DC stage to ensure ripple free charging of different classes of LVEVs. Even if, the HGB DC-DC stage accomplishes transformerless steeper step down gain, its simple design and effective operation over wide battery voltages (24 V–72 V), are further ensured through flexible DC link voltage (150 V – 350 V) control of front end FBLCSC IPQR. At last, the design, operation, and performance of the presented CS are validated experimentally, and relevant results are discussed comprehensively in support of the performance validation of the presented CS.

Surface alignment of nematic liquid crystals by direct laser writing of photopolymer alignment layers

ABSTRACT We demonstrate the fabrication of good quality surface alignment layers on glass by Direct Laser Writing method using a 2-photon polymerisation technique. We use commercially available photosensitive resins to print alignment layers by scanning the focal point of a femtosecond laser near the resin-glass interface. This results in down to ~ 100 nm thin alignment layers that provide good planar anchoring of 5CB and MLC13300, with the easy axis of alignment along the scanning direction. The azimuthal anchoring strength is ~ 5 × 10−6 J/m2 and is an order of magnitude weaker compared to commercial rubbed polyimide alignment layer. The threshold voltage for Fréedericksz transition in a 90° twisted nematic cell is slightly increased compared to conventional rubbed polyimide for printed alignment layers. The turn-on switching time is longer for printed layers compared to polyimide alignment layers, whereas the turn-off time is shorter for printed alignment layers. The advantage of this new method is in its flexibility, as we demonstrate printing of complex surface alignment patterns with alignment layer thickness below 100 nm.

A Soft-Switching Bridgeless Buck-Boost Power Factor Correction Converter With Simple Auxiliary Circuit and Low Input Current THD

In this paper, a new bridgeless (BL) buck-boost power factor correction (PFC) converter using pulse width modulation (PWM) control is presented. The introduced structure operates in discontinuous conduction mode (DCM) to achieve the sinusoidal form of the input current inherently. The proposed converter utilizes a simple zero voltage transition (ZVT) circuit in which the auxiliary switch is turned ON and OFF under zero current switching (ZCS) condition, and the main switches turn ON and OFF under zero voltage switching (ZVS). Moreover, all diodes are turned OFF under ZCS condition, and the reverse recovery problem is solved. By reducing the number of semiconductor elements in the current flow path, conduction loss is minimized. Also, the proposed structure utilizes only one magnetic element. The above-mentioned advantages along with a low total harmonic distortion (THD) and high efficiency are the main benefits of the proposed structure compared to previous topologies. In addition, unlike the BL-buck converter, the input current dead angle is omitted without adding any extra components. Finally, a 500 W-100 kHz prototype at 90-265 Vrms input and 96 V output is implemented to verify the theoretical analysis and it illustrates the efficiency of 97.35 % and the input current THD is about 2.7 % at 220Vrms input voltage.

A Novel Three-Phase Omnidirectional Wireless Power Transfer System With Zero-Switching-Loss Inverter and Cylindrical Transmitter Coil

Aiming at the problems of large switching loss and large output power fluctuation in the existing omnidirectional wireless power transfer (OWPT) system, a novel OWPT system with zero-switching-loss inverter and cylindrical transmitter coil is proposed. By introducing an auxiliary resonant network with simple structure and low-loss on each phase arm of the three-phase inverter, zero-voltage switching (ZVS) turn-ON and zero-current switching (ZCS) turn-OFF within the full power range can be acquired. The switching loss in the main circuit of inverter is reliably eliminated. The transmitter coil is a cylindrical coil composed of the three curved rectangular coils, whose excitation current amplitude is equal and the phase difference is 120°. It can arise a spatial rotating magnetic field around the transmitter coil and provide an omnidirectional energy transmission channel. The operating principle of soft-switching is analyzed in detail, and the design rules of soft-switching in full power range and the parameter design method of coupler to reduce the fluctuation of output power are given. Ultimately, an experimental prototype is used to verify the feasibility of the proposed OWPT system. The experimental results indicate that the system output power is retained at 93.4W∼104.7W and transfer efficiency is retained at 71.2%∼78.1% under arbitrary angular misalignment of receiver.

A soft-switched flyback converter with leakage recovery snubber for class 2 LED driver

This work presents a soft-switching flyback converter with active leakage recovery snubber suitable for use in high-performance class 2 LED lamp drivers. The proposed converter enjoys the features of simple circuit structure, improved switching performance, high efficiency and high power density. Transformer leakage energy of the flyback converter is recovered using an active auxiliary circuit, which also helps in soft-switching transition of the switches and power diodes. Switching turn-on and turn-off of its main switch occurs under ZVZCS and ZVS conditions respectively, whereas ZCS turn-on and ZVZCS turn-off of the auxiliary switch are also achieved in this converter. The detailed steady-state operating principle with mathematical equations, design guidelines and loss analysis are presented in this work. Finally, the converter feasibility is thoroughly tested through laboratory experimentation on a hardware prototype. The experimental results have successfully validated the theoretical analysis and real-time behavior of the converter.

A Single-Stage Charger for LEV Based on Quadratic Buck-Boost AC-DC Converter Topology

A single-stage AC-DC converter, which uses a quadratic buck-boost voltage gain, for LEVs' (Light Electric Vehicles) battery charging is presented in this work. Unlike conventional BCs (Battery Chargers), which employ transformer (low or high frequency) based approaches to charge low voltages LEVs' batteries, the presented charger utilizes transformerless single-stage power architecture. In order to realize desired charging of LEVs and to maintain proper transformerless voltage gain, the presented quadratic buck-boost AC-DC converter ensures high step-down gain characteristics between AC mains and low voltage battery packs. Besides realizing desired battery charging profile, the presented single-stage BC ensures high PQ (Power Quality) indices (low input current distortions and unity power factor operation) at the supply side. Notably, the presented quadratic buck-boost AC-DC converter exhibits an intrinsic power factor correction (PFC) feature at the AC input mains under discontinuous inductor current mode (DICM) operation, thereby, incurring minimum complexities during the control implementation, which further reduces the cost of the charger. The DICM operation facilitates negligible switch turn-on and diode reverse recovery losses, and therefore, ensures an improved conversion efficiency of the BC. Even if, the presented AC-DC converter employs two switching devices, the simultaneous switching of both switches shrinks the cost and complexity of driving circuitry even further. Finally, a comprehensive operational analysis, component selection criteria, and modelling of the presented quadratic buck-boost AC-DC converter-based LEVs BC are carried out and its performance is validated through a test bench set-up in a laboratory environment. Relevant results are presented to validate the efficacy of the presented quadratic buck-boost AC-DC converter for LEVs charging applications.

Body Diode of 1.2kV SiC MOSFET: Unipolar and Bipolar Operation

In this work, we investigate the Body Diode (BD) of a 40mOhm, 1.2kV SiC MOSFETs. We performed DC measurements and switching measurements, at Room Temperature (RT) and High Temperature (HT) (T=175°C), together with TCAD simulation and calibration. In switching measurements, we focused on the low side (LS) switch turn-on event, i.e., the BD turn-off event. We demonstrated that unipolar and bipolar BD can both be achieved with different VGS. With VGS=-5V, BD conducts in bipolar mode with carriers being injected via pn junction. This is rather well known in literature and is well characterized by the Negative Temperature Coefficient (NTC) of BD VF. Switching with BD VGS=-5V show strong reverse recovery-temperature dependent that caused by the augmented minority carrier injection at high temperature. Unipolar BD is achieved by channel conduction at VGS=0V and it is well characterized by BD VF - Positive Temperature Coefficient (PTC). Thanks to the unipolar nature, turn-on switching with BD VGS=0V show no reverse recovery-temperature dependent.

High-performance Cuk converter with turn-on switching at zero voltage and zero current

The soft-switching technique has the potential to significantly enhance the performance of the power converter. This is primarily because it allows for an increase in the switching frequency, which ultimately leads to improved modulation quality. This raises extra concerns, particularly in high-power applications, because in a standard hard-switching converter structure, components can often not function at frequencies higher than a few hundred hertz. This paper presents a high-efficiency soft switching CUK converter.When the main and auxiliary switches are turned on and off at zero voltage, the proposed converter yields zero voltage and zero current. The suggested method is ideal for a DC-DC converter based on IGBTs or MOSFETs. The recommended systems are described using theoretical analysis, the results of computer simulations, and experimental data derived from a prototype. The design parameters of the inductance and capacitor circuit for edge-resonant soft switching were obtained using the output power and the switching duty ratio. In the end, soft-switching is better than hard-switching in terms of efficiency, particularly when operating under full load.

Single-Stage Active Rectifier With Wide Impedance Conversion Ratio Range for Inductive Power Transfer System Delivering Constant Power

Compared with the constant current (CC) charging mode, the constant power (CP) charging mode can speed up the battery charging rate and free the charger from excessive thermal design problems. However, the range of the battery's equivalent resistance in CP mode is wider than that in CC mode, which makes it difficult to track the optimal resistance of the inductive power transfer (IPT) system for efficiency enhancement. To solve this problem, this paper proposes a single-stage active rectifier (SSAR) integrating an interleaved buck converter with a full-bridge active rectifier (FBAR). Compared with the traditional FBAR, the resistance conversion ratio range of the SSAR is extended from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$[0, 8/\pi ^{2}]$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$[0, 8]$</tex-math></inline-formula> , and the output current ripple is reduced due to the interleaved operation. A novel optimal phase angle control strategy is correspondingly proposed for the IPT system with the SSAR, which features advantages of wide impedance conversion ratio range, zero voltage switching (ZVS) turn-on of all MOSFETs, and no communication between the primary and the secondary sides. A 150 W experimental prototype is provided to verify the effectiveness of the proposed rectifier.

A ZVS-Based Non-Isolated High Step-Up DC–DC Converter With Low Voltage Stress for Renewable Applications

A high gain soft switched step-up DC-DC converter is presented in this paper. High gain is achieved at lower duty and turns ratio with a pair of coupled inductors and a voltage multiplier. In addition, an active clamp is incorporated to reduce the voltage stress across the main switch. Hence, switches with lower on-state resistance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_dson</i> ) and lower voltage ratings are employed, reducing both conduction losses and cost. It additionally helps in achieving zero voltage switching (ZVS) to both MOSFETs. By recycling the leakage energy of the coupled inductors, voltage gain is further increased. It also helps to accomplish zero current switching (ZCS) turn-on and off of diodes. This further reduces losses and increases further efficiency. Moreover, the reverse recovery problem of the diodes is also mitigated. The working principle, steady-state analysis, and design guidelines have been carried out. Finally, a 500 W hardware set up with an input voltage range of 20-24 V and output of 400 V at a switching frequency of 50 kHz is built to validate the performance of the proposed converter. The operating efficiency at full load is observed as 95.11%.

Triple-Mode Wide-Input Range Resonant DC–DC Converter With Extended Asymmetric Modulation

This article proposes a triple-mode resonant converter operating over a wide input voltage range for renewable energy harvesting applications. The proposed converter operates in a pure series resonant mode with a nominal input voltage, an asymmetric resonant boost mode with a low-input voltage, and an asymmetric pulse-width-modulation series resonant buck mode with a high-input voltage. This converter adopts an asymmetric half-bridge-type voltage-doubler to reduce the transformer turns ratio and number of active components. Moreover, its extended asymmetric modulation reduces hard switching turn-ON losses compared to conventional symmetric modulations. Consequently, the proposed converter attains high power conversion efficiency and power density over a wide input voltage range. The operating principles and steady-state analysis are presented in detail herein. Finally, a 300-W/380-V prototype is presented to validate the feasibility of the proposed converter over an input voltage range of 30-60 V.

Study on changes in electrical and switching characteristics of NPT-IGBT devices by fast neutron irradiation

We studied the irradiation effects of fast neutron generated by a 30 MeV cyclotron on the electrical and switching characteristics of NPT-IGBT devices. Fast neutron fluence ranges from 2.7 × 109 to 1.82 × 1013 n/cm2. Electrical characteristics of the IGBT device such as I–V, forward voltage drop and additionally switching characteristics of turn-on and -off were measured. As the neutron fluence increased, the device's threshold voltage decreased, the forward voltage drop increased significantly, and the turn-on and turn-off time became faster. In particular, the delay time of turn-on switching was improved by about 35% to a maximum of about 39.68 ns, and that of turn-off switching was also reduced by about 40%–84.89 ns, showing a faster switching.

Optimized 750V SiC MOSFETs for Electric Vehicle Inverter Operation

We report an AEC-Q101-qualified 750V, 15 mΩ planar SiC MOSFETs with a long short circuit withstand time (SCWT) of &gt; 9μs at VDS=400V and VGS=15V and a low specific on-resistance (RON,SP) of 2.1 mΩ.cm2 at VGS=15V designed for xEV traction inverter applications. The RDS(on) at VGS=15V increases from 15mΩ at 25 °C to 21 mΩ at 175 °C. A low turn-on (EON) and turn-off (EOFF) switching energy loss of 95.5μJ and 67μJ at IDS=75A, VDS=400V was measured at 25 °C. The gate oxide lifetime at worst case operating fields of 5MV/cm is &gt;&gt; 20 years.