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In this paper, a Phase-shift-modulated (PS) Resonant Two-switch Boosting Switched-capacitor Converter (RTBSC) and its modulation map are proposed. Compared with the traditional RTBSC, all diodes are replaced by active switches and then phase-shift modulation is applied. The advantages of the modified topology are obtained as follow. 1) The voltage gain can be regulated efficiently either below or above the nominal value even at light-load condition, making it suitable for applications with voltage fluctuations; 2) The conduction loss is reduced by replacing all diodes in RTBSC with low turn-on resistance transistors, especially for high-order and high-gain configuration; 3) All switches achieve the zero-voltage-switching (ZVS) turn-on operation; 4) The soft-charging property smooths the current profile. Aside from the topology modification, a comprehensive analysis of operation principle, voltage gain, component stress and ZVS region is given. On the basis, a modulation map with the optimal operation region is proposed. It provides a guideline to operate and design such converters in the target gain range, low component stress and ZVS region, making up for the lack of modulation map and design guideline in aforementioned literatures. A 120W prototype with low-voltage side 43-60V and high-voltage side 150V was designed to verify the above analyses.

This work includes fabrication and electrical characterization of Metal/Interlayer/Semiconductor (MIS) structures with methyl violet organic film on p-InP wafer. Metal(Ag)/ Interlayer (methyl violet =MV)/Semiconductor(p-InP) MIS structure presents a rectifying contact behavior. The values of ideality factor (n) and barrier height (BH) for the Ag/MV/p-InP MIS diode by using the current-voltage (I-V) measurement have been extracted as 1.21 and 0.84 eV, respectively. It was seen that the BH value of 0.84 eV calculated for the Ag/MV/p-InP MIS structure was significantly higher than the value of 0.64 eV of Ag/p-InP control contact. This situation was ascribed to the fact that the MV organic interlayer increased the effective barrier height by influencing the space charge region of inorganic semiconductor. The values of diffusion potential and barrier height for the Ag/MV/p-InP MIS diode by using the capacitance-voltage (C-V) measurement have been extracted as 1.21 V and 0.84 eV, respectively. The interface-state density of the Ag/MV/p-InP structure was seen to change from 2.57×1013 eV-1cm-2 to 2.19×1012 eV-1cm-2.

Time-to-digital converters (TDCs) are high-performance mixed-signal circuits capable of timestamping events with sub-gate delay resolution. As a result of their high-performance, in recent years TDCs were integrated in complementary metal-oxide-semiconductor (CMOS) technology with highly sensitive photodetectors known as single-photon avalanche diodes (SPADs), to form digital silicon photomultipliers (dSiPMs) and SPAD imagers. Time-resolved SPAD-based sensors are capable of detecting the absorption of a single photon and timestamping it with picosecond resolution. As such, SPAD-based sensors are very useful in the field of biomedical imaging, using time-of-flight (ToF) information to produce data that can be used to reconstruct high-quality biological images. Additionally, the capability of integration in standard CMOS technologies, allows SPAD-based sensors to provide high-performance, while maintaining low cost. In this paper, we present an overview of fundamental TDC principles, and an analysis of state-of-the-art TDCs. Furthermore, the integration of TDCs into dSiPMs and SPAD imagers will be discussed, with an analysis of the current results of TDCs in different biomedical imaging applications. Finally, several important research challenges for TDCs in biomedical imaging applications are presented.

A gallium nitride (GaN)-based resonant step-up converter is proposed for the application in the satellite electric propulsion (EP) system. This converter consists of a full-bridge inverter, a resonant tank and a multi-stage Cockcroft-Walton (CW) voltage multiplier to provide a high gain. Additionally, the air-core transformer is introduced due to the megahertz switching frequency allowed by the GaN device. Thus, the limited magnetizing inductance of transformer and the remarkable junction capacitance of diode have to be carefully considered in the resonant tank design, especially after considering that this converter normally operates at the light load in the EP system. In this work, the 4-order LCLC resonant converter is investigated. The recommended parameter selection for the 4-order resonant tank is also provided. A 1.2-MHz, 23-V/2.5-kV, and 6-W prototype is demonstrated. It achieves a low harmonics distortion and a low power loss with the zero voltage switching (ZVS).

White light-emitting diodes (WLEDs) fabricated by single-phase full color emitting phosphor is an emerging solution for health lighting. The crystallographic site occupation of activators in a proper host lattice is crucial for sophisticated design of such phosphor. Here, we reported a high quality white light-emitting phosphor Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+ with spectral distribution covering whole visible region. Blue light emission originates from Ce3+ ions occupying preferentially Ba2+ site by controlling synthesis conditions. Green and red light are abtained from Eu2+ occupying Ba2+ (and Ca2+) site and Mn2+ occupying Ca2+ site, respectively. In this triple-doped phosphor, strong red emission with a low concentration Mn2+ is realized by the efficient energy transfer from Ce3+ and Eu2+ to Mn2+. Furthermore, high quality white light is accomplished by properly tuning the relative doping amount of Ce3+(K+)/Eu2+/Mn2+ based on efficient simultaneous energy transfer. The results indicate that Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+ is a promising white light-emitting phosphor in WLEDs application.

Dynamic avalanche (DA) phenomena and current filament (CF) formation are two extreme conditions observed in high-power devices, setting the maximum limit on turn-on/off current capability and di/dt in Silicon-based bipolar devices. The properties of the Silicon Carbide (SiC) material enable devices with increased resilience for DA and CF compared to Si counterparts, and thus the SOA limits may be extended. In this study, the limit of DA and CF in SiC-based semiconductor structures are investigated by numerical TCAD simulations, for different current levels, di/dt, and temperatures for high-voltage devices (e.g., 20 kV class). DA is first indicated for di/dt beyond 105 kA/μs for current densities in the range of 50–1000 A/cm2, at 448 K. Similarly, stray inductance induced avalanche conditions are initiated above 33 kA/μs, while CF is initiated for di/dt starting from 83 kA/μs for current densities in the range of 8.3 kA/cm2. Moreover, the effects of the stray inductance in the main circuit loop are studied which may cause critical voltage transients during certain operating conditions. The outcome of the study may be useful to determine safe-operating-area limits and to be used as input for power electronic converter design as well as gate driver design for high-power electronic systems.

In this work, the influences of P-well design and turn-off gate-to-source bias on the surge robustness of SiC MOSFET’s body diode are studied. Devices with high and low P-well doping concentration designs are stressed with surge current pulses when gate-to-source is biased with 0V or -5 V. The gate-to-source bias is found to have effects on the surge capability of the low P-well doping designed device. In the case of 0 V bias, the channel is prone to turning on and acquires a higher surge capability than the devices under the -5 V. On the other hand, the surge capability of high P-well doping designed device is found less influenced by the gate-to-source bias. Furthermore, threshold voltage instability after repetitive surge pulses is also investigated. The device with low P-well doping shows better threshold stability due to its lower interface trap density. Based on the results above, a design methodology is proposed from the view of device mechanism and operation condition. Relatively low P-well doping design and negative gate bias are recommended for SiC MOSFET, as they can improve the single pulse surge robustness of body diode and minimize the threshold voltage instability in repetitive surge pulse events.

Multiplexing circuits in pixelated PET detectors are being studied with the goal of minimizing the degradation of detector performance. The purpose of this study was to develop a diode-based symmetric charge division (SCD) circuit with reducing the crosstalk caused by the leakage currents of adjacent channels connected in rows and columns. Four different SCD circuits (diode-based SCD with grounding path, diode-based SCD, resistor-based SCD with grounding path and resistor-based SCD) were constructed and their performance was evaluated and compared after being combined with a PET detector consisting of LYSO crystals optically coupled with SiPM. The diode-based SCD circuit with grounding path achieved a crosstalk ratio, energy resolution, coincidence timing resolution (CTR) and mean peak to valley ratio of 0.02, 14.3%, 0.5 ns and 27.9: 1, respectively; the diode-based SCD circuit achieved 0.03, 15.9%, 0.7 ns and 19.4: 1, respectively; the resistor-based SCD circuit with grounding path achieved 0.04, 14.5%, 0.9 ns and 19.4: 1, respectively; the resistorbased SCD circuit achieved 0.05, 17.8%, 1.8 ns and 17.7: 1, respectively. These results indicate that the proposed SCD has the potential to improve not only the crosstalk but also the energy linearity, energy resolution, and coincidence timing resolution characteristics in PET detectors.

In this paper, a simulation and measurement return loss parameter results comparison in frequency reconfigurable antenna is proposed. More lowprofile and compact microstrip antennas have been developed in recent years for 5 GHz, 5G, WLAN, Wi-Fi, and ISM band applications. These antenna frequency bands may be single, dual, or multiband. The small microstrip antenna, without connecting any external devices like switches, resonators, and passive elements, does not show any variations in their simulation and measurement results like return loss (S11 parameter), gain, and efficiency. However, in the S11 parameter most frequency reconfigurable antennas show a mismatch between simulation and measurement results. The reason for this mismatch between the simulation and measurement results are given in the paper.

Following the continuous development of wide bandgap (WBG) devices and multilevel converter technology, medium voltage (MV) active front ends (AFEs) are becoming promising in future high-power-density and high-power applications. However, the cost issue is one of the major drawbacks, which stops the WBG devices from being widely applied in high-power areas. This paper proposes a silicon carbide (SiC) and silicon (Si) hybrid five-level unidirectional rectifier. It requires only four SiC MOSFETs with relatively low blocking voltage and four Si diodes. Meanwhile, by adding snubber capacitors, all the Si devices are with low-speed switching, and the voltage stresses of fast SiC MOSFETs are minimized. In this paper, operational analysis and carrier-based phase-disposition PWM scheme for this circuit are discussed in detail. The capacitor voltage balancing and unity power factor are both realized. Simulation and scaled-down experimental results are demonstrated to verify the proposed rectifier. Furthermore, the comparison of the hybrid five-level rectifiers is given to show the advantages of the proposed rectifier in terms of voltage stress, efficiency, and cost.

Red emitting phosphor plays a significant role in accelerating the improvement of illumination quality for white light emitting diodes (WLEDs). In this work, by using solid-state reaction method, an efficient novel Ba2LuNbO6:Eu3+ phosphor with double-perovskite structure was successfully prepared. Here, a series of Ba2LuNbO6:Eu3+ red phosphors can be efficiently pumped by the near-ultraviolet (UV) light and then present high-brightness at orange emission (598 nm, 5D0→7F1) and red emission (610 nm, 5D0→7F2). The ratio values of 610 to 598 nm in Ba2LuNbO6:Eu3+ phosphors exceed 1 when the content of Eu3+ is larger than 0.4 mol, because the occupation of Eu3+ ions is changed from Lu3+ ions with symmetric sites to Ba2+ ions with asymmetric sites. Besides, the optimized concentration of Eu3+ at the 5D0→7F2 transitions is obtained when x=1, indicating that there is non-concentration quenching in Ba2LuNbO6:Eu3+ phosphors. Moreover, the CIE chromaticity coordinates of Ba2LuNbO6:Eu3+ was calculated to be of (0.587, 0.361), the color purity was calculated to be 72.26% and internal quenching efficiency (IQE) was measured to be 67%. Finally, the thermal stability of Ba2LuNbO6:Eu3+ phosphors was also studied. Our work demonstrates that the novel double-perovskite red-emitting Ba2LuNbO6:Eu3+ phosphors are prospective red emitting elements for WLEDs applications.

With the rapid and extensive development of wireless communication and low power electronics, electromagnetic wireless power harvesting (WPH) draws more and more attention. As the core component for RF-to-DC power conversion, its characteristics determine the performance of the overall system. To obtain as much DC energy as possible, ambient electromagnetic energy with various frequencies should be efficiently rectified. Therefore, its important to widen the operating bandwidth of the rectifier. According to the theoretical analysis of the Schottky diode, it can be found that if the harmonic components generated by the diode can be fed back through a specific approach for rectifying, the bandwidth of the rectifier will be effectively improved. Therefore, a broadband rectifier has been proposed based on the previous principle. For validation, a wideband rectifier based on Schottky diode SMS7630 had been designed, fabricated and measured. When the input power level is 0 dBm, the conversion efficiency of the implemented rectifier is larger than 40% from 0.4 GHz to 2.6 GHz within a relative bandwidth of 146.67%, exhibiting an ultra-wide bandwidth compared with existing state-of-the-art configurations.

In the existing solar photovoltaic modules, cells are connected in series. The performance of the series-connected module degrades severely during partial shading condition. Further, the use of bypass diode causes multiple peak (local and global peaks) problem. Therefore, total cross tied (TCT) connection has been proposed in this paper to connect the cells in a module (TCT connected module) that gives a better performance during partial shading without multiple peak problem. A novel analytical algorithm is presented in this paper, which will help the photovoltaic installers to estimate the output power of a TCT connected module without using any sophisticated measuring instruments except irradiance and temperature measurement. The proposed analytical algorithm is simple, robust and user friendly, which can be widely used in multidisciplinary research. The output of the proposed model is verified with the simulation and laboratory scale experimental results, which shows less than 4.58% error. Moreover, the proposed algorithm is implemented in 10MW solar plant, which shows around 174.44% performance improvement compared to the existing TCT connected array. Further, the current value of the TCT connected module is very high, which can be effectively used in high current applications such as welding even in partial shading condition.

Reliable and affordable AC/AC power conversion plays a key role in supplying various electrical equipment. Among the options available, direct matrix converter (DMC) outperforms its counterparts (e.g. AC/DC/AC), in terms of lifespan and compactness, due to its omission of fragile and bulky dc-link capacitors. However, most off-the-shelf DMC modules suffer from high input current spikes, which if unresolved, can noticeably increase current stresses and lower efficiency. Origin of the spikes and a mechanism for reducing them are hence studied in the paper, before developing a low-cost SiC-Si hybrid module for implementing DMC reliably and compactly. The developed module consists of 18 Si insulated gate bipolar transistors (IGBTs) and 18 SiC junction barrier Schottky (JBS) diodes connected in a common-collector structure. The improved reverse recovery property of the SiC JBS diodes then permits the hybrid module to operate with mitigated current spikes. To demonstrate, the hybrid module has been fabricated, tested and compared with two counterparts in terms of their input current spikes and power losses over different output voltages and switching frequencies. Experimental results have proven the expected performances of the hybrid DMC module, which collectively, can accelerate large-scale emergence of small all-semiconductor drives for industrial pumps, cooling and refrigeration systems, and others widely needed in developing economies.

In this manuscript, a novel single-input-dual-output (SIDO) LLC converter is proposed for wide output voltage applications. An H5-bridge is utilized on the primary side and linked with two separate resonant tanks. By morphing the H5 bridge, the input of each resonant tank can be configured as either full bridge, half bridge, or idle. On the secondary side, two semi-active rectifiers provide two control degrees-of-freedoms. The circuit operation is always tuned at the optimal resonant frequency and the output voltages are modulated by the secondary side pulsewidth. It exhibits good voltage regulation performance with two fully decoupled output ports. Both output ports can achieve wide voltage ranges. All MOSFETs can achieve ZVS turning-ON and all the diodes can achieve ZCS turning-OFF over a wide output voltage and load ranges. To verify this concept, a 1.4-kW rated prototype is designed to convert 390V input into two decoupled 100-400V outputs. The designed prototype exhibits 97.72% peak efficiency and good decoupled voltage regulation performances. The experimental results agree well with the theoretical analysis.

In conventional medium voltage Solid-State Circuit Breakers (SSCBs), series-connected semiconductor switches are used with Metal Oxide Varistors (MOVs) in parallel with each of them to extend the voltage ratings of the breakers without incurring the dynamic voltage unbalance. Besides, for isolating the faults at faster speeds, the clamped surge voltages of the MOVs are always much higher than the system voltages. For those reasons, the voltage ratings of all the switches in the SSCBs have to be overdesigned according to the surge voltage values, which causes high material costs along with nonideal conduction losses in the solid-state circuit breakers employed for medium voltage DC distribution systems. To solve this dilemma, a Surgeless Diode-Clamped Multilevel Solid-State Circuit Breaker has been proposed in this paper. It offers an ultrafast isolation speed with no significant surge voltages or dynamic unbalanced voltage across the semiconductor switches. With these attributes, the proposed SSCB can potentially use the semiconductor switches rated at lower voltages compared to conventional SSCBs and have higher efficiency along with faster isolation speed. The simulation and experimental results are presented to validate the technical feasibility and practical values of the proposed solid-state circuit breaker.

Small and low-cost chlorophyll sensors are popular in agricultural sector and food-quality control.Combining such sensors with silicon CMOS electronics is challenged by the absence of silicon-integrated light-sources.We experimentally achieve optical absorption sensing of chlorophyll based pigments with silicon (Si) micro light-emitting diodes (LED) as light-source, fabricated in a standard SOI-CMOS technology.By driving a Si LED in both forward and avalanche modes of operation,we steer its electroluminescentspectrum between visible (400-900 nm) and near-infrared (1120 nm). For detection of chlorophyll in solution phase, the dualspectrum light from the LED propagates vertically through glycerol micro-droplets containing sodium copper chlorophyllin at varying relative concentrations. The transmitted light is detected via an off-chip Si photodiode. The visible to near-infrared color ratio (COR) of the photocurrent yields the effective absorption coefficient. We introduce the LED-specificmolar absorption coefficient as ametric to compute the absolute pigment concentration (0.019 ± 0.006 mol L-1) and validate the results by measurements with a hybrid spectrophotometer. With the same sensor, we also show noninvasive monitoring of chlorophyll in plant leaves. COR sensitivities $\sim 3.9 \times 10^{4}$ mol-1L and $\sim 5.3 \times 10^{4}$ mol-1L are obtained for two leaf species, where light from the LED propagates diffusely through the thickness of the leaf prior to detection by the photodiode. Our work demonstrates the feasibility of realizing fully CMOS-integrated optical sensors for biochemical analyses in food sector and plant/human health.

The snappy reverse recovery (SRR) and failure of high-voltage non-punch-through (NPT)-PIN diodes under extreme working conditions is of great significance to the reliability evaluation of operating diodes in actual power electronic devices. In this paper, the analysis of the physical mechanism of the diode SRR and the restrictions of the traditional PT-PIN diode model are made. Then, the traditional model for soft recovery is improved in order to accurately describe the diode SRR characteristics. Simulations of key dynamic performances of the established model agree well with the testing results. Furthermore, a suppression method for diode SRR based on the optimal RC snubber circuit is proposed. A high-voltage NPT-PIN diode used in the DC-DC converter with different RC snubber circuits is simulated using the proposed diode snappy model and tested. The comparison results show good consistency between the simulated and measured voltage and current peaks and the diode SRR can be suppressed effectively. The model developed and the results are of much importance to the prediction of the safe operation area of the diode and to the reliability improvement of power electronic device.

In renewable energy micro-source applications, a wide range of voltage conversion of the step-up converter is an essential part to equalize the typical low voltage of micro-source with DC-bus voltage of Inverter or motor drives. In order to meet this purpose, an ultra-voltage gain step-up DC-DC converter is proposed in this paper. The proposed converter has made an arrangement of the regenerative-boost fed switched inductor and capacitor configurations. Thereby, due to such an organization of structure, the proposed converter can develop an extremely high voltage-gain even at lower duty ratios. In addition, it has advantages of lesser switching stress across all power semi-conductive diodes. Furthermore, this paper describes the steady-state analysis and comparative features of the converter with existing recent literature. Finally, to validate theoretical analysis and test feasibility and suitability of the proposed ultra-gain converter, the experimental results were observed by a 500 W fabricated prototype.

Two-switch converters (TSC) are widely used and are more efficient at high power levels with lower component stress than the single-switch topologies. These converters have flexible operations in both boost and buck modes, and are applicable to onboard battery chargers in the power factor correction (PFC) converter stage. The intermediate output voltage at PFC can be greater or lesser than the peak of input voltage (variable DC-link voltage) resulting in higher switching losses across the boost switch. An auxiliary circuit proposed in the paper comprises of an active switch, a diode with a pair of resonant inductor’s and capacitor that are applied across the main switch to operate with loss-less switching. Though the conduction time of the proposed auxiliary circuit is small compared to the main converter operation but it attains the main switch to turn-ON with zero voltage transition (ZVT) and turn-OFF with zero current transition (ZCT). Also, the auxiliary switch involved in the converter operation is also subjected to SS. Additionally, the proposed converter has no extra component stress and switching losses. With this, it can enhance the overall converter efficiency. The various operating modes involved in different time intervals are analyzed and presented in the paper. Moreover, the design criteria of auxiliary circuit and the main converter parameters are also discussed in the paper. As proof-of-concept, a hardware prototype of 1 kW is implemented with the proposed control structure and the results are presented in the paper. Maximum efficiency of 97.4% has been achieved from the implemented hardware prototype.

U ovom diplomskom radu odrađena je optimizacija parametara laserskog zavarivanja čelika P92, čija je primjena relativno specifična s obzirom na karakteristike kao što su velika toplinska otpornost, otpornost na oksidaciju, velika čvrstoća i tvrdoća te mu je glavna primjena u elektranama s fosilnim gorivima. U prvom dijelu rada detaljno je objašnjen rad lasera, osnovni dijelovi, princip rada i glavna podjela lasera. Također, detaljno su opisani laseri koji se najčešće koriste kao što su: Nd:YAG, CO2, rubinski, He-Ne, dušikov i drugi laseri. U drugom dijelu rada (eksperimentalnom) provedena je Taguchi temeljena siva relacijska analiza kako bi se optimirali parametri zavarivanja, određen je S/N omjer za pojedine parametre i geometrijske karakteristike te je naposljetku izvedena analiza varijance (ANOVA) ., In this work, the optimization of laser welding parameters of P92 steel was performed, which application is relatively specific considering its characteristics such as high heat resistance, oxidation resistance, high strength and hardness, and its main application is in power plants with fossil fuels. In the first part of the work, the operation of the laser, the basic parts, the principle of operation and the main division of the laser are explained in detail. Also, the most commonly used lasers are described in detail, such as: Nd:YAG, CO2, ruby, He-Ne, nitrogen and other lasers. In the second part of the work (experimental), a Taguchi gray relational analysis was performed in order to optimize the welding parameters, the S/N ratio was determined for individual parameters and geometric characteristics, and finally an analysis of variance (ANOVA) was performed.

Lightweight and flexible electronics have recently emerged at the forefront of optoelectronic applications. In this regard, graphene electrodes enable opportunities for new photodiode devices. In this paper, we formulated and tested graphene ink using the standard inkjet printing technique. It was shown that the maximum conductivity of ink was achieved for 14 print passes of the graphene layer. Moreover, we deposited Molybdenum Disulfide (MoS2) ink in the same pattern and used it as an active layer. We put MoS2 ink on an Indium-Tin-Oxide (ITO) glass substrate and then deposited graphene ink as a top electrode to fabricate an ITO/MoS2/graphene device. The fabricated device showed good rectification behavior and high ON/OFF switching behavior with a max photocurrent of 15 µA at +2 V. The technique thus paves the way for low-cost, low-temperature processing of electronics and one-step fabrication.

The supply of energy with the correct parameters to electrical appliances is possible with the use of energy converters. When a direct current is required, rectifier bridges are needed. These can be made using rectifier diodes. The problem of excessive junction temperatures in power diodes, which are used to build rectifier bridges and power converters, was recognized. For this reason, research work was carried out to create a model of a rectifier diode placed on a heat sink and to analyze the heat dissipation from the junction of this diode under forced convection conditions. The results obtained from the simulation work were compared with the results of thermographic temperature measurements. The boundary conditions chosen for the simulation work are presented. A method is also presented that determined the convection coefficient under forced convection conditions. The difference between the simulation results and the results of the thermographic measurements was found to be 0.1 °C, depending on the power dissipated at the junction and the air velocity around the diode.

In recent years, the military has been exploring the use of wide bandgap semiconductors (WBGS) such as gallium nitride (GaN) and silicon carbide (SiC) due to their promising material properties, as compared to silicon (Si). Understanding the reliability of these high-performance WBGS devices is paramount to their implementation in military systems. However, it remains to be tested because good-quality reliability data is needed, but it is difficult and expensive to produce. This thesis looks at the design and implementation of a modular reliability testing subsystem in the form of a novel data acquisition system. First, a system was designed to perform automated, in-situ leakage current measurements of up to four devices under test (DUT) with sub-nA resolution. Next, a wide sample of devices consisting of a resistor, two Zener diodes, a power diode, two GaN diodes, and a field effect transistor (FET) were subjected to various voltage sweep and reverse-bias tests that were recorded by the system. Finally, the results of those validation tests were processed and analyzed. The system achieved leakage current resolutions below 100 pA, demonstrating its ability to measure various devices. ONR Arlington, VA, 22217 Captain, United States Marine Corps Approved for public release. Distribution is unlimited.

In this paper we demonstrate a high wall-plug efficiency and low threshold current for heterogeneously integrated III-V-on-Silicon distributed feedback (DFB) lasers. Above 12% wall plug efficiency is achieved for a 200 µm long DFB laser diode at 25 °C. Up to two times 6 mW of optical power is coupled into the silicon waveguide and more than 40 dB side-mode suppression ratio is obtained. We also discuss the non-return-to-zero on-off keying modulation at 20 Gb/s and the transmission over a 2 km long optical fiber.

In a hard switched MOSFET based converter, turn-on energy losses is predominant in the total switching loss. At higher junction temperature the turn-on energy loss further increases due to the reverse recovery effect of the complementary MOSFETs body diode in a half-bridge configuration. Estimation of the switching loss under different operating conditions at an early design stage is essential for optimising the thermal design. Analytical switching loss models available in literature are generally used for estimating the switching losses, due to its accuracy and simplicity. In this paper, the inaccuracy in the reported loss models due to non inclusion of temperature dependent reverse recovery characteristics of body diode, is investigated. A structured method to determine the temperature-dependent switching loss of a SiC MOSFET in a half-bridge is presented. A simple methodology has been proposed to analyze the carrier lifetime's temperature dependencies of a SiC MOSFETs body diode. Device parameters from a 1.2kV/36A SiC MOSFETs datasheet are used for developing the loss model and experimental validation of the model.

A single input dual output (SIDO) converter with a coupled inductor is a widely used converter to generate two outputs from a single input. The analysis presented in the literature is for continuous conduction mode (CCM), where the converters are operating in heavily loaded conditions. While operating, the load may reduce, leading to the discontinuous conduction mode (DCM) of the converter. A coupled inductor SIDO (CI-SIDO) boost converter is analyzed in this paper. As this converter combines two boost converters with a common input and a coupled inductor, the DCM operation of one boost affects the other. Due to coupling, it is found that the body diode of the MOSFET turns ON in the DCM operation of the CI-SIDO boost converter. This paper finds the conditions to turn ON body diode and its effect on the average values of the inductor current, diode current, and input current. The paper also analyses the CI-SIDO boost when the body diode is not turned ON. This paper finds the effect of change in input voltage, load current, and duty ratios on the DCM operation of the CI-SIDO boost. Simulations verify all the obtained conditions in MATLAB/Simulink and experiments using a laboratory prototype.

At present, solid-state laser-driven lighting fabricated with blue laser diode (LD) and phosphor has been greatly developed in high-power lighting applications. The major obstacle is the luminescence saturation threshold of the fluorescence conversion material (YAG:Ce). In this work, we successfully prepared a series of high-quality and robust YAG:Ce single crystals. With high quantum efficiency (QE = 92%), regular crystal structure and high thermal conductivity, the single-crystal has excellent ability to deal with high radiation flux and thermal accumulation generated by high power. Matching the single-crystal with the laser, the luminous efficiency up to 274 lm/W and saturation threshold of 12 W/mm2 were obtained. In addition, the influence of Ce doping concentration and sample processing conditions on the indicators in laser-driven white lighting was systematically studied. The results are of great significance and are believed to promote the development of solid-state laser-driven lighting.

In this letter, high-performance p-NiO/-Ga2O3 heterojunction diodes (HJDs) with composite terminal structures, a p-NiO junction termination extension (JTE), and a small-angle beveled field plate (BFP), are demonstrated. By implementing a p-NiO JTE structure, the optimal breakdown voltage (Vbr) of -Ga2O3 HJD increase from 955 V to 1945 V, and the integration of the small-angle BFP further boosts the breakdown voltage up to 2410 V. An 80-nm thin p-NiO layer is adopted in the heterojunction to reduce the specific on-resistance (Ron,sp), while the composite terminal structures have little effect on Ron,sp, due to the super-large lateral spread resistance. The -Ga2O3 HJD with composite terminal structures achieves a low Ron,sp of 1.12 mcm2, yielding the highest direct-current Baligas figure-of-merit (FOM = Vbr2/Ron,sp) among all reported -Ga2O3 diodes with a value of 5.18 GW/cm2, which is about 15% of theoretical value. These results suggest that the electrical field engineering with composite terminal structure is a viable and effective technological strategy to enable the realization of -Ga2O3 bipolar power rectifiers.

Deadtime is a critical design target for soft switching dc/dc converters. On the one hand, the deadtime is necessary to ensure safety operation of the devices in one switching leg; on the other hand, enough deadtime is required to achieve zero voltage switching (ZVS) operation. Due to the complexity of LLC converters, traditionally, the deadtime selection is either based on engineering experience or inaccurate analysis of converter, which leads to an unoptimized deadtime. Specifically, a large deadtime will lead to the efficiency degradation due to the body diode conduction during deadtime. The ZVS operation cannot be completely achieved with a small deadtime, which will also degrade the converter efficiency. Therefore, there is a demand for the accurate analysis of deadtime effect on LLC converters. In this paper, an accurate and in-depth analysis of deadtime effect on LLC converter is performed with the aid of time domain analysis. But the proposed adaptive deadtime strategies can also be implemented based on the experiment or simulation results for those who do not have access to time domain analysis of LLC converters. Based on the analysis, novel adaptive deadtime strategies are proposed for LLC converter. Compared with traditional fixed deadtime strategy, around 1% efficiency improvement is achieved for a 125 W experimental prototype during the whole operating range.

A series of single phase, warm white light emitting phosphors, Gd(PxV1–x)O4:y at% Sm3+, with 1 at% Bi3+ doping concentration were synthesized by high temperature solid state method in this work. The experimental results indicate broadband cyan emission of Bi3+ and characteristic orange-red emission of Sm3+ can be effectively tuned by changing the ratios of PO43−/VO43− in Gd(PxV1–x)O4:1 at% Sm3+,1 at% Bi3+, and the energy transfer process among VO43−, Sm3+, Bi3+ also can be adjusted. Based on this, warm white light emitting can be realized by further optimizing the doping concentration of Sm3+ in the phosphors. At 423 K, the PL intensity of Gd(P0.7V0.3)O4:2 at% Sm3+,1 at% Bi3+ remains ～84.3% of the initial value at 293 K, while the measured quantum efficiency is 67.8%. EL spectrum analysis results of the fabricated white light emitting diode (wLED) based on a 310 nm UV-chip and Gd(P0.7V0.3)O4:2 at% Sm3+,1 at% Bi3+ phosphors imply low correlated color temperature (3132 K) and appropriate color-rending index (Ra = 82.7). These results demonstrate that Gd(P0.7V0.3)O4:2 at% Sm3+,1 at% Bi3+ is a good candidate for manufacturing UV-activated warm white light emitting diodes.

In order to suppress the crosstalk in gallium nitride (GaN)-based bridge configuration, a novel negative voltage self-recovery gate drive (NVSRGD) is proposed in this paper. The resistor-capacitor-diode voltage divider is applied to establish the negative gate-source voltage and suppress the impact of positive crosstalk. The antiparallel diode is added to constitute low-impedance Miller current path from the driver integrated circuit (IC) to the GaN device. It works together with the self-recovery gate-source voltage to suppress the negative crosstalk, which not only prevents the GaN device from the negative overstress but also reduces the reverse conduction loss during the dead time. The NVSRGD is composed of a few passive components, which are suitable for integrating into the driver IC. The capacitors and resistors of the NVSRGD are designed to determine the negative voltage level and the restore time. Additive separate negative voltage power supplies or active devices are not needed. The double pulse test based on GS66508B verifies the effectiveness of the proposed method for suppressing the positive and negative crosstalk of GaN devices.

A single-phase full-color emitting phosphor Sr2Ca2La(PO4)3O:Eu2+,Tb3+,Mn2+ was synthesized by the high temperature solid-state method. The phase formation, luminescence properties, thermal stability, and energy transfer from Eu2+ to Tb3+ and Eu2+ to Mn2+ in Sr2Ca2La(PO4)3O were investigated in detail. Tunable emission color from blue to blueish green or orange can be observed under 365 nm near-ultraviolet excitation based on the energy transfer from Eu2+ to Tb3+ or Mn2+ ions by varying the ratio of Eu2+/Tb3+ or Eu2+/Mn2+ ions. White light was obtained with chromaticity coordinates of (0.3558, 0.3500) in the Sr2Ca2La(PO4)3O:0.04Eu2+,0.08Tb3+,0.40Mn2+ phosphor, suggesting their potential applications in white light emitting diodes.

Recently, gallium oxide (Ga2O3) has attracted great interest as material for efficient power devices. Yet, experimental studies rather concentrate on the investigation of bare dies and lack the analysis of devices in industry standard packages. Furthermore, while Ga2O3 trench MOS Schottky barrier diodes (SBDs) appear to be promising candidates, temperature-dependent measurements previously revealed inhomogeneous junctions. In this work, a vertical β-Ga2O3 trench MOS Schottky barrier diode is presented. The diode exhibits a homogeneous Schottky junction and nearly ideal thermionic current flow. This indicates better junction properties than previously observed for trench as well as non-trench Ga2O3 SBDs, with only a slight influence of interface states at high temperatures. As a next step towards application, the chip is successfully bonded in an industry-standard TO-247 package. The molded discrete is operational at low temperatures of -50 °C and up to high temperatures of 150 °C while exhibiting a lower increase in on-resistance with rising temperature than SiC Schottky diodes.

The switching oscillations caused by the high-speed switching and low-damping characteristics of SiC MOSFET seriously deteriorates its high-reliability applications. By viewing from the terminals of both SiC MOSFET and diode for the turn-on and turn-off oscillation, not only can the two-port networks be formed to carry out more accurate analysis about the system characteristics, but also the characteristic equations of system can be deduced, thereby reliably guiding the RC snubber design. Since the oscillation is essentially caused by the imaginary part of poles, with the assistance of the two-port networks, an optimized design method of RC snubber circuit is developed by the way of actively assigning poles. Different from existing analytical techniques, no necessity is needed to reduce the order of characteristic equations to yield the mathematical expressions of RC snubbers. Instead, RC snubber regions where oscillations can be completely suppressed are determined directly by exhaustion method. A very promising overlapping area is found, which means that both the turn-on and turn-off oscillation can be eliminated simultaneously by the same snubber circuit. Moreover, the related discussions about existence conditions of the snubber region, sensitivity to parameters and the limitation in choosing RC are illustrated in detail.

Owing to the diversity of structure and potential applications in the field of electrics, sensors, and light-emitting diodes, lead halide perovskites have attracted great attention in recent years. Especially those lead halide perovskites with non-centrosymmetric crystal structures usually exhibit nonlinear optical (NLO) characteristics, which may endow them photoelectricity switching functionality. In this work, a lead-based hybrid organic-inorganic perovskite (HOIP) material, trimethyliodomethylammonium lead trichloride (TMIM·PbCl3), is obtained on the basis of tetramethylammonium lead chloride through halogen substitution on the cation part. It shows dual-phase-transition behavior around 345 and 358 K, which is significantly improved. TMIM·PbCl3 crystallizes in the chiral space group, P212121, and shows a well-defined second harmonic generation (SHG) response, and good switching endurance, which makes it an excellent candidate for SHG switching material. This work highlights the importance of halogen substitution for crystal engineering and may pave way for the further exploration of the optoelectronic devices.

The correct parameter determination of the photovoltaic module and the solar cell is considered an important phase to deliver a reliable simulation for the PV system characteristics. The triple diode model (TDM) has been examined to model the PVM 752 GaAs thin-film PV solar cell (SC), STM6 PV module, and RTC SC. A set of the measured I-V data at various levels of the weather conditions has been considered for the studied PV solar cell/modules. A new marine predators algorithm (MPA) is used to identify the TDM parameters based on measured datasets. Throughout the optimization procedure, the nine undetermined parameters of TDM are employed as decision variables but the fitness function requires to be least is the RMSE between the experimental and calculated datasets. The achieved results by MPA are compared with different algorithms. The comparison confirmed the superiority of MPA.

Opening new wavelength bands is the most economic step for further increasing the capacity of optical transmission links. Characteristics of different amplifier technologies for signal amplification in different wavelength bands are detailed. In particular, the suitability of these technologies for short-term and mid-term implementation is considered. An important criterion is the availability of qualified components, notably the required pump laser diodes. On this basis, solutions for the near-term and the mid-term are discussed.

Switched-capacitor-based multilevel inverters for boost-type dc–ac power conversions usually exhibit a trade-off between the switch count and switch-voltage rating, i.e., a reduction of one necessitating an increase of the other. Such a dilemma is well addressed in this article by proposing a novel single-phase nine-level inverter based on a switched-capacitor network with a single switch. The proposed inverter then reduces the number of switches while generating a boosted dc-link voltage. A unique six-switch full-bridge cooperating with a low-frequency half-bridge further steps-up the output voltage with a quadruple gain. The voltage stresses on the power devices are, however, maintained low even under the boosted high output voltage, as all the switches/diodes can be clamped to any of the low-voltage capacitors. Consequently, low-voltage power devices can be utilized, reducing the overall power loss. Detailed theoretical analysis, calculations, and design considerations of the proposed inverter are provided. Comparisons with the prior-art inverters illustrate its advantages. Simulations and experimental tests on a 1-kVA inverter prototype verify the above-claimed benefits.

InGaAs/InP single-photon avalanche diodes (SPADs) attract increasing attention for the infrared light detection and ranging (LIDAR) due to the low-cost and compact-size construction. Although constant endeavor has been dedicated to improve the dead time and timing jitter, it remains challenging to implement high-speed and high-resolution LIDAR. Here, we develop a high-performance GHz-gated InGaAs/InP APD operated in the quasi-free-running mode, while its gating signal is unlocked from the light source. The used low-pass filtering technique enables us to continuously adjust the repetition frequency of the gate for carefully optimizing photon detection efficiency (PDE) and timing jitter. Increasing the gates’ repetition frequency from 1 GHz to 2.75 GHz, the PDE improves dramatically from 2.02% to 3.30%, while the timing jitter drops from 156 ps to 114 ps. Furthermore, we verify that changes in the PDE have little effect on the timing characteristics, making the SPAD more suitable for LIDAR with large dynamic range. Meanwhile, the dead time is about 4 ns, which is much shorter than that of the SPAD working in the free-running mode, guaranteeing rapid mapping of targets. Finally, as a proof-of-principle demonstration, the InGaAs/InP SPAD is used in a time-of-flight LIDAR system, which demonstrates a sub-centimeter depth resolution directly.

This paper presents an improved full-bridge converter with a five-diode rectifier. The primary side circuit is composed of a full bridge with two transformers and two split capacitors. On the secondary side, five diodes are employed in the rectifier stage. By using the asymmetrical PWM signals, this converter can realize the ZVS of all switches and reduce the circulating current. The two transformers share the load power equally in whole load range. Compared with the other dual-transformer-isolated-full-bridge converters, the transformers in the proposed converter are easy to optimize because of the load power equal sharing. Furthermore, the output filter inductance is reduced, which reduces the loss and volume. According to the loss analysis, the proposed converter has higher efficiency compared with some other DC-DC converters. The experimental results of a prototype with 300-400V input voltage and 250V/4A output verify the performance of the proposed converter.

Critical conduction mode (CRM) or discontinuous conduction mode (DCM) boost power factor correction (PFC) converter is widely used in low power applications for its advantages of zero-current turn-on of the switch, no reverse recovery in diode and simple control. The input current of fixed switching frequency control CRM boost PFC converter and the input current of constant duty-cycle control DCM boost PFC converter mainly contain third harmonic. Moreover, the phase of the third harmonics is opposite. This paper proposes a harmonic elimination parallel control to connect these two converters in parallel. The input current third harmonic of the parallel converter can be eliminated completely so as to improve the PF to nearly unity in the whole input voltage range. This parallel method is an interesting way to extend power, and is different from the existing method of parallel DCM boost PFC converter or parallel CRM boost PFC converter. The experimental results verify the accuracy of the theoretical analysis.

For bidirectional CLLC resonant converters, synchronous rectification (SR) is a key technique that can reduce the conduction losses in rectifying side by replacing the diodes with the switches channel. However, existing methods suffer from either complex hardware, or incomplete and imprecise control effect. Aiming at solving these problems, this paper proposes a digital sensor-less SR algorithm based on the time-domain model under a hybrid modulation for symmetrical CLLC converters. The proposed approach can precisely enable the SR drive action within almost the whole load range and without any additional hardware, e.g., anti-parallel diode, SR IC, and high bandwidth sensor. Its implementation only needs to measure DC signals (e.g., the output current), rather than any high-frequency resonant signals. Additionally, the presented algorithm can be easily implemented on a digital controller. Finally, experiments have been performed on a prototype to verify the validity and applicability of the presented SR algorithm.

CMOS single-photon avalanche diodes (SPADs) have broken into the mainstream by enabling the adoption of imaging, timing, and security technologies in a variety of applications within the consumer, medical and industrial domains. The continued scaling of technology nodes creates many benefits but also obstacles for SPAD-based systems. Maintaining and/or improving upon the high-sensitivity, low-noise, and timing performance of demonstrated SPADs in custom technologies or well-established CMOS image sensor processes remains a challenge. In this paper, we present SPADs based on DPW/BNW junctions in a standard Bipolar-CMOS-DMOS (BCD) technology with results comparable to the state-of-the-art in terms of sensitivity and noise in a deep sub-micron process. Technology CAD (TCAD) simulations demonstrate the improved PDP with the simple addition of a single existing implant, which allows for an engineered performance without modifications to the process. The result is an 8.8 $\mu$ m diameter SPAD exhibiting $\sim$ 2.6 cps/ $\mu$ m $^2$ DCR at 20 $^{\circ}$ C with 7 V excess bias. The improved structure obtains a PDP of 62% and $\sim$ 4.2% at 530 nm and 940 nm, respectively. Afterpulsing probability is $\sim$ 0.97% and the timing response is 52 ps FWHM when measured with integrated passive quench/active recharge circuitry at 3 V excess bias.