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In this paper, a p–n thin film NiO/ZnO heterojunction for a rectifier diode and a UV photodetector is prepared and characterized. Nickel oxide (NiO) and gallium-doped zinc oxide (ZnO:Ga) thin films are grown by RF magnetron sputtering and spray pyrolysis techniques, respectively. The crystal structure of the thin films is studied by the X-ray diffraction (XRD) method. The transmittance and reflectance are studied by UV–VIS spectroscopy. The p–n electrical parameters are estimated from current–voltage characteristics. The effects of duration of thermal annealing at 450oC on the characteristics of the NiO/ZnO:Ga device are evaluated. The non-annealed diode shows the best rectification coefficient of 105 at ±1 V. The p–n photodetection capability is studied under UV illumination. At a reverse bias of –3 V under 365-nm UV illumination, the device shows a current intensity of ~6.2 × 10-12 A. The observed increase in the reverse current intensity by about two orders of magnitude under a UV lamp with a spectral irradiance of 10 W m-2 μ m-1 indicates a promising application in UV light detection.În această lucrare, a fost descrisă fabricarea și caracterizarea diodei redresoare și senzorului UV pe baza heterojoncțiunii cu straturi subțiri p-NiO/n-ZnO. Straturile subțiri de oxid de nichel (NiO) și oxid de zinc (ZnO:Ga) au fost obținute prin metoda pulverizării în regim de radiofrecvenţă (RF) și, respectiv, metoda pulverizării pirolitice. Structura cristalină a straturilor subțiri a fost investigată prin metoda difracției cu raze X (XRD). Transmitanța și reflectanța au fost studiate prin spectroscopie UV-VIS. Parametrii electrici ai heterojoncțiunii p-n au fost estimați din caracteristicile curent-tensiune. Au fost evaluate efectele duratei tratării termice la 450oC asupra caracteristicilor structurii NiO/ZnO:Ga. Dioda redresoare netratată a arătat cel mai bun coeficient de redresare de 105 la aplicarea tensiunii ±1 V. Capacitatea de detecție a senzorului pe baza heterojoncțiunii p-n a fost studiată la iluminarea UV. Curentul de întuneric al joncțiunii la polarizare inversă de -3V este ~ 6,2 × 10-12 A. O creștere a curentului invers cu aproximativ două ordine de mărime la iluminare cu lampa UV cu iradiere spectrală 10 Wm-2aproximativ două ordine de mărime la iluminare cu lampa UV cu iradiere spectrală 10 Wm-2aproximativ două ordine de mărime la iluminare cu lampa UV cu iradiere spectrală 10 Wm-2 μ m-1 prezintă o aplicație promițătoare în detectarea luminii UV.m-1 prezintă o aplicație promițătoare în detectarea luminii UV.m-1 prezintă o aplicație promițătoare în detectarea luminii UV.

A novel multiresonant dc–dc converter with notch filter function is proposed in this article. The converter can regulate the output voltage over a wide range and has significant advantages in terms of gain. Due to its gain characteristics, the multiresonant converter has better inherent soft startup capability and over-current protection function. In addition, the switches of the converter can realize zero-voltage switching over the entire output-voltage range, and the output rectifier diode can realize zero-current switching. Compared with the traditional LLC converter, the multiresonant converter can use third harmonic to transmit the active power, and the loss caused by the reactive power cycle of the converter is reduced, which improve the efficiency. The converter parameters are optimized from the perspective of gain and efficiency in this article. Finally, a 2.5-kW experimental prototype is designed and the peak efficiency is 97.27%. The correctness of the theoretical analysis and the rationality of the parameter design are proved by the experimental results.

First harmonic analysis (FHA) is arguably the most widely used analytical technique for wireless power transfer (WPT) circuits due to its simplicity. Although FHA can provide closed-form solutions, the existence of rectifier diode forward voltage drop and higher order harmonics, especially the second and third harmonics at variable duty cycle operation, can significantly deteriorate its accuracy. This paper presents an accurate and efficient method called enhanced multiple harmonic analysis (eMHA) for the optimal design and optimal control of WPT systems. The eMHA method considers the nature of nonlinear rectification networks under nonsinusoidal current and reexamines the concept of the equivalent load. As a result, the rectified WPT system is transformed into a series of linear systems with complex load impedances. The steady-state electric quantities can be then explicitly calculated. This enables eMHA to seamlessly work with numerical optimization algorithms to facilitate the automated design and optimization of WPT systems. An example of optimal design and optimal control of a 10 W WPT system is demonstrated. The results obtained by eMHA and FHA are also compared. A prototype of the designed circuit was constructed. The accuracy and effectiveness of eMHA are verified by experimental measurements. This paper is accompanied by a MATLAB-based analytical tool with a graphical user interface demonstrating the effects of circuit variables on electrical quantities and waveforms.

This paper proposes a single-stage bridgeless isolated AC-DC power factor correction (PFC) topology, and this topology can realize the function of step-up and the galvanic isolation for the AC input and DC output voltages through single-stage power conversion process. Firstly, the operation principle of the topology is analyzed in details. Then, by reasonably designing the series resonant parameters, the zero-voltage-switching (ZVS) turn-on for the power switches in the primary-side and zero-current-switching (ZCS) turn-off for the output rectifier diodes in the secondary-side of the transformer can also be achieved under wide load range, and the voltage stress of the power switches are also reduced based on the active clamping technology. The design procedure for the key components of the proposed converter is also derived. Finally, a 3 kW experimental prototype based on SiC power devices with 85 kHz switching frequency is built to verify the correctness and feasibility of the proposed topology, and the experimental results show a good performance. It can operates in a wide input grid voltage range, 95.7% of peak conversion efficiency and 3.9% of total harmonic distortion(THD) value for grid current could be obtained.

The article presents the results of studies of ultrafast rectifier diodes intended for use in high-frequency rectifiers, modulators, converters, pulse transducers, limiters and other pulse devices under the influence of radiation. The schemes of measuring the current and voltage of diodes under the influence of special factors are given

The article describes the study of rectifier diodes for resistance to special factors. The direct reverse current Iobr and the forward voltage of the diode Uobr were considered as a criterion for the performance of diodes. Based on the results of the calculation and experimental evaluation of the resistance of rectifier diodes to special factors, graphical dependences of the reverse current and direct voltage on the value of the special factor are constructed.

NASA's Evolutionary Xenon Thruster-Commercial (NEXT-C) project is tasked with developing flight electric propulsion systems, including both thrusters and power processing units (PPUs). In 2018, the beam supply in a NEXT-C engineering prototype PPU experienced an output rectifier diode failure during development thermal-vacuum testing. A failure investigation led by NASA GRC identified the root cause of the failure as a thermal runaway caused by increased reverse recovery losses in the diodes when the PPU was run at its maximum operating temperature. Significant reverse recovery performance variations were identified in diodes with the same part number but manufactured by different vendors. The failure investigation was able to collect evidence of the increased reverse recovery and replicate the diode failures in a controlled laboratory environment.

A simple modified configuration of the conventional phase-shifted full-bridge (C-PSFB) converter, phase-shifted FB converter without filter inductor (PSFB-w/o-L) is proposed in this study in order to reduce the peak voltage stress on the rectifier diodes. As the proposed configuration is devoid of filter inductor, it features lighter weight and low cost. As the proposed configuration is achieved eliminating the filter inductor, the maximum voltage that comes across the rectifier diode is limited to the output voltage, thus eliminating the need for snubber circuit. Additionally, the proposed PSFB-w/o-L has the advantage of negligible duty cycle loss. A comprehensive analysis on the mechanism of the peak voltage problem across the rectifier diode in the C-PSFB is addressed and the way it is eliminated in the proposed PSFB-w/o-L is described. The detailed analysis of the operation and design consideration of the proposed PSFB-w/o-L is presented. Simulation and experimental results are presented to verify the analysis.

This paper proposes a novel active-clamp forward converter (ACFC) with a lossless-snubber on the secondary-side, which combines a resonant capacitor and a clamping diode with an output inductor in parallel. The conventional ACFC achieves zero-voltage-switching on switches of the primary-side during dead time for reducing the switching loss and voltage spike. Unfortunately, on the secondary-side of transformer, the voltage spike damages the free-wheeling diode and rectifier diode due to the reverse recovery current and junction-capacitor of the diode and leakage inductance of the transformer. This paper proposes a lossless-snubber on the secondary-side operation for reducing the voltage spike on the free-wheeling diode and forward-rectifier diode. Therefore, the converter proposed in this paper is suitable for high-output-current applications. Experimental results are shown to verify the analysis and design procedure of the proposed forward converter.

A novel selective dimming method of the output channels of a multichannel LED driver is proposed in this paper. This LED driver comprises a front-end ac–dc boost power factor correction converter followed by symmetric half-bridge isolated nonresonant dc–dc converter and symmetric voltage-multiplier rectifier with purely capacitive output filters. By controlling the duty ratios of the secondary side switches, which are strategically placed at the output voltage-multiplier-based rectifiers, the average LED current and hence the brightness of individual channels are controlled. Moreover, a unique primary side peak current control is implemented to control the peak currents of LEDs during pulsewidth modulation dimming, which prevents electromigration-related fast aging of the LEDs. This driver also has the advantages of high power (>120 W) operation capabilities, and high efficiency (>94%) with primary side switches zero voltage switching turning on and secondary side rectifier diodes zero current switching turning off . A detailed analysis and design procedure of the proposed converter is presented. To validate the analysis, an industry-standard 150 W prototype is developed, which is digitally controlled by a cost-effective non-DSP microcontroller. The experimental results are in perfect agreement with the claims. A comparison for universal ac input and isolated LED drivers with selective dimming is displayed.

Wireless inductive-coupled power transfer is a very appealing technique for the battery recharge of autonomous devices like surveillance drones. The charger design mainly focuses on lightness and fast-charging to improve the drone mission times and reduce the no-flight gaps. The charger secondary circuit mounted on the drone generally consists of a full-bridge rectifier and a second-order filter. The filter cut-off frequency is usually chosen to make the rectifier output voltage constant and so that the battery is charged with continuous quantities. Previous works showed that an increase in power transfer is achieved, if compared to the traditional case, when the second-order filter resonant frequency is close to the double of the wireless charger excitation and the filter works in resonance. This work demonstrates that the condition of resonance is necessary but not sufficient to achieve the power increment. The bridge rectifier diodes must work in discontinuous-mode to improve the power transfer. The paper also investigates the dependence of the power transfer increase on the wireless excitation frequency. It is found the minimum frequency value below which the power transfer gain is not possible. This frequency transition point is calculated, and it is shown that the gain in power transfer is obtained for any battery when its equivalent circuit parameters are known. LTSpice simulations demonstrate that the transferred power can be incremented of around 30%, if compared to the case in which the rectifier works in continuous mode. This achievement is obtained by following the design recommendations proposed at the end of the paper, which trade off the gain in power transfer and the amplitude of the oscillating components of the wireless charger output.

In recent years, the LLC (inductor&ndash, inductor&ndash, capacitor) DC transformer has been widely used in communication and computer power supply because of its advantages of zero voltage conduction of primary switch and zero current turn off concerning the output rectifier diode. To obtain higher transmission efficiency and make the LLC DC transformer always run at the optimal operating point, the switching frequency of the LLC DC transformer should work at the resonance frequency of the circuit. In actual conditions, the optimal operating frequency of the LLC DC transformer will be changed due to the influences of the working condition on the circuit parameters and the load change. Therefore, the LLC DC transformer controlled by the fixed frequency mode will not be in the best working condition. In this paper, an adaptive frequency tracking method is used to control the circuit, when the circuit parameters change, the LLC DC transformer can always be in the best working state. Then, the influence of circuit parameters such as output power and excitation inductor on the optimal working point of the LLC DC transformer is analyzed in detail. Finally, a 1 kW LLC resonant converter prototype is designed under laboratory conditions to verify the feasibility of the control strategy.

In the medium-voltage dc collection system for renewable energy sources, the high-power high-frequency transformer is one of the key equipment. To lower down the parasitic capacitance of high-power high-frequency transformer, the multi-layer and multi-section structure is adopted for the secondary winding. Furthermore, the multiwinding output series structure on the high-voltage side is employed as well, which is beneficial to reduce the voltage stress and voltage sharing difficulty of the rectifier diodes. A special bobbin is designed to implement the multi-winding output series structure. At last, a 250 kW high-frequency transformer is designed and manufactured with the good performance verified.

©2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Transformer Rectifier Units (TRUs) are a reliable way for DC generation in several electric applications. These units are formed by multiple three-phase uncontrolled bridge rectifiers connected according to two main topologies (parallel and series), and fed by a phase-shifting transformer, which can have different configurations. Fault diagnosis of the uncontrolled bridge rectifier diodes is one of the most important concerns on the electronic devices, nonetheless, rectifier units are inherently not protected in front of Open-Circuit (O/C) faults, which cause malfunction and performance deterioration. In order to solve this drawback, the proposed fault diagnosis method is based on the O/C fault signature observed in the DC-link output voltage of TRUs rectifier. It allows detecting the O/C diodes of parallel and series TRUs with different phase-shifting transformer configurations and for the most usual fault scenarios. Moreover, it also helps the prediction of diodes that could be exposed to failure after the fault, which provides corrective maintenance for the TRU development. The proposed method is illustrated from MATLABTM numerical simulations of a 12-pulse TRU, and is validated with experimental tests. This work supported in part by the Research Project Estabilidad de Redes MVdc Integrando Tecnologias de Energias Renovables, Almacenamiento de Energia y Convertidores de Fuente de Impedancia, RTI2018-095720-B-C33, in part by the Ministerio de Ciencia, Innovación y Universidades, and in part by the European Union.

Isolated, zero-voltage-switching dc–dc converter topologies represent attractive solutions in the continuous run toward higher switching frequencies, allowing more compact power supplies. Among them, the asymmetrical half-bridge flyback converter represents an interesting option, featuring simple duty-cycle control at constant switching frequency, as opposed to the popular $LLC$ converter. The majority of papers dealing with this topology consider an approximated voltage gain similar to that of an isolated buck converter operating in continuous conduction mode, i.e., proportional to the duty cycle and, practically, load independent. On the contrary, the true voltage gain is nonmonotonic at high duty-cycle values. Anytime the converter is designed for a resonant operation, as is advisable to eliminate any reverse recovery problem of the rectifier diode, the voltage gain not only increases, but also becomes a function of the switching frequency. This article investigates the converter's voltage gain in detail, deriving a theoretical framework capable of capturing its real behavior and dependencies. The proposed analytical model has been verified through simulations as well as experimental measurements taken on a 160-W prototype working at 400 kHz.

Avalanche breakdown of novel 650 V SiC Schottky-barrier rectifiers is investigated. The rectifier diode has low leakage current for the temperatures up to 300 °C. Thermal coefficient of avalanche breakdown increases with the temperature to around 0.009%/K at 200 °C. Near-uniform avalanche breakdown is verified using emission imaging, and maximum specific avalanche energy of 20.7 J/cm2 is achieved. The critical temperature for stability in unclamped inductive switching (UIS) is above 520 °C as estimated through thermal simulation. Long-term walkout of breakdown voltage at 176 °C is less than 0.02%.

A novel hybrid resonant zero-voltage zero-current switching three-level converter with capacitive output filter is proposed in this paper, which undergoes half of the input voltage for switches and is suitable for offshore wind farms in medium-voltage dc (MVDC) collection systems. The proposed converter, utilizing two transformers with very different power ratings, adopts insulated-gate bipolar transistors for all six power switches and operates in discontinuous current mode and can achieve zero-current switching for the four main switches and rectifier diodes over the whole load range. Meanwhile, the auxiliary switches with small current rating can realize zero-voltage switching naturally. Hence, the switching loss is reduced, which is vital in MVDC applications. By the trajectory formulas of the resonant current and voltage, the trajectory paths can be achieved, which is helpful to compare the peak and turn- off currents of switches. The design rules of main parameters can be deduced with the trajectory formulas and paths. The influence of the turns ratio of auxiliary transformer and the resonant capacitance on the peak and turn- off currents is discussed in detail. The operation principles of the proposed converter are analyzed and verified by the simulation and experimental results.

In this study, a novel AC-DC bridgeless buck converter for power-factor-correction (PFC) applications with the inherent current-shaping ability and high PFC performance is proposed. Under a certain operation condition, dead zones in the proposed converter are reduced inherently compared with its conventional buck PFC counterpart, which result in higher PF and lower total harmonic distortion significantly. Furthermore, two rectifier diodes are eliminated, which contributes to efficiency. The detailed operation principle and theoretical analysis of discontinuous conduction mode (DCM) are presented. The simulation comparison between the conventional and proposed bridgeless buck PFC converter is also described. Finally, an experimental lab-made prototype operating in DCM is constructed to validate the feasibility of this proposed converter.

In this paper, a novel soft-switching full-bridge converter with an additional secondary switch and a nondissipative energy recovery snubber is proposed. Thanks to the combination of an active switch and the capacitor—diode–diode snubber employed at the secondary side of the converter, the proposed converter can achieve zero-voltage zero-current switching for all of the primary switches and rectifier diodes over the entire load range. As a result, the rectifier diodes have no reverse-recovery problem and their ringing voltage is clamped. In addition, since no phase shift is used for the gate signals of the primary-side switches, the converter control can be implemented easily and it has no circulating current inherently. The converter exhibits a significant improvement in terms of efficiency, especially under light-load conditions, which is difficult to achieve with conventional phase-shift full-bridge converters. A 3-kW prototype circuit is implemented to verify the superior performance of the proposed converter.

A voltage multiplier rectifier with a novel time-division-multiplexing (TDM) control scheme for high step-up converters is proposed in this study. In the proposed TDM control scheme, two full-wave voltage doubler rectifiers can be combined to realise a voltage quadrupler rectifier. The proposed voltage quadrupler rectifier can reduce transformer turn ratio and transformer size for high step-up converters and also reduce voltage stress for the output capacitors and rectifier diodes. An N-times voltage rectifier can be straightforwardly produced by extending the concepts from the proposed TDM control scheme. A phase-shift full-bridge (PSFB) converter is adopted in the primary side of the proposed voltage quadrupler rectifier to construct a PSFB quadrupler converter. Experimental results for the PSFB quadrupler converter demonstrate the performance of the proposed TDM control scheme for voltage quadrupler rectifiers. An 8-times voltage rectifier is simulated to determine the validity of extending the proposed TDM control scheme to realise an N-times voltage rectifier. Experimental and simulation results show that the proposed TDM control scheme has great potential to be used in high step-up converters.

Owing to environmental issue and global temperature rise, the growth of renewable energy sources such as photovoltaic arrays, fuel cells and wind turbine power has been developed. Therefore, the direct current (DC) micro-grid distributed systems are more and more important to integrate renewable energy sources, energy storage devices, local DC loads or alternative current (AC) loads and AC micro-grid through AC–DC converters to achieve high reliability and efficiency in power systems. For industry and transportation applications such as metro and light transit, the preferred voltage level on DC micro-grid system is recommended as 600–900 V. The proposed DC–DC converter contains three half-bridge circuits with a series–parallel connection at primary–secondary sides so as to decrease voltage rating of active devices and current rating of rectifier diodes. Asymmetric pulse-width modulation scheme is used to realise the soft-switching turn-on for active devices and the switching losses of power devices can be further reduced. To overcome input split voltage balance issue, flying capacitors are employed between two cascaded half-bridge circuits and the voltage rating of each active device is limited at V in/3. Finally, experiments with a laboratory prototype are provided to verify the theoretical analysis and circuit performance.

This paper presents a study and design of an isolated DC-DC bidirectional converter. Conditions for zero-voltage switching (ZVS) for all the active switches and zero current switching (ZCS) for the rectifier diodes are derived analytically. Design guidelines to ensure ZVS are presented. A lab prototype is designed to verify the functionality of the converter and experimental results are recorded.

In this communication, a new theoretical model for the ac transit frequency of organic rectifier diodes is proposed. The model is built upon a full description of the drift-diffusion current in the rectifier diode for the entire forward bias regime. Such a method precisely correlates the transit frequency to a number of materials, geometrical, and operational parameters in particular the charge-Injection barriers. By systematic variation of parameters, it is found that a rectifier operating beyond 1 GHz is observable only with a highly injecting anode. Other parameters to reach that regime of operation are discussed. This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1D1AB07048877), and by Materials, Components & Equipment Research Program funded by the Gyeonggi Province.

This study presents a new LLC resonant converter with two transformers in parallel for the electric vehicle battery charger. This topology achieves the zero-voltage switching for main switches in the entire charging profile. In addition, the zero-current switching for output rectifier diodes is extended under charging condition. The proposed charger provides a wide range output voltage for the battery system. Moreover, in order to maintain the high efficiency under charging, the charger adopts a bidirectional switch. At low-output power condition, the charger uses one transformer to transfer the energy. Finally, the design procedure is provided and implemented in a prototype charger with the input DC link 400 V and the output voltage of 36-58 V. Experimental results are presented to demonstrate the system performance. The maximum power is up to 700 W and the peak efficiency is as high as 93.6%.

In this paper, the LLC resonant converter based on SiC devices is applied to the auxiliary converter of subway. The principle of operation of this converter is analyzed in detail, and a LLC resonant converter with a capacity of 40kW is designed. By building the system circuit in the PSIM simulation software, it is proved that the converter can work normally, the ZVS of the switches and the ZCS of the rectifier diodes are realized in the full input range and the full load range to ensure the high-efficiency operation of the circuit under high frequency conditions and meet the requirements of auxiliary converter in subway.

In this paper, an alternator rotating speed detection method for auto-start application is presented, which proposes to detect the alternator rotating speed from the frequency of field signal at rotor side. The conventional methods detects the alternator rotating speed from the frequency of phase signal at stator side, which is easily interfered by the leakage current of rectifier diodes. The proposed method solves the above issue and stably gets the alternator rotating speed from the rotor signal even though the phase signal is distorted by the leakage current of rectifier diodes. Experimental results verified the analysis.

A full-bridge LLC resonant converter with series-parallel connected transformers for an onboard battery charger of electric vehicles is proposed, which can realize zero voltage switching turn-on of power switches and zero current switching turn-off of rectifier diodes. In this converter, two same small transformers are employed instead of the single transformer in the traditional LLC resonant converter. The primary windings of these two transformers are series-connected to obtain equal primary current, while the secondary windings are parallel-connected to be provided with the same secondary voltage, so the power can be automatically balanced. Series-connection can reduce the turns of primary windings. Parallel-connection can reduce the current stress of the secondary windings and the conduction loss of rectifier diodes. Compared with the traditional LLC resonant converter with single transformer under same power level, the smaller low-profile cores can be used to reduce the transformers loss and improve heat dissipation. In this paper, the operating principle, steady state analysis, and design of the proposed converter are described, simulation and experimental prototype of the proposed LLC converter is established to verify the effectiveness of the proposed converter.

The automotive industry is in the midst of a once-in-a-century transformation. The industry began adopting semiconductors in the 1960s, starting with rectifier diodes for alternators. Then, the spread of electronically controlled engines that supported emission control in the 1970s triggered wide-scale installation of semiconductor devices (Figure 1.3.1). The automotive semiconductor market has grown rapidly since the 1980s [1]. Further growth is expected as electrification, autonomous vehicles, and connected vehicles develop (Figure 1.3.2). In the past, when semiconductors were introduced into automobiles, the purpose was to improve performance by replacing conventional mechanical controls with electronic ones; it is important to note that no changes were made to the major components. But, for the projected disruptive transformation (already underway), dramatic changes to all major automobile components and related concepts are expected. Electrification (replacing the internal combustion engine (ICE) with an electric motor), automated driving (replacing the human driver with artificial intelligence (AI)), and connected vehicles (replacing independent automobiles with ones that are incorporated into society) will play important roles in this transformation as the automobile evolves in a major way.

There exists high rectified output voltage spike in isolated transformer’s secondary, especially for the high frequency link auxiliary inverters under wide input voltage. It will lead to increased voltage stress and loss of switching devices, impeding the improvement of system’s reliable operation and conversion efficiency. In order to solve the root causes of rectified output voltage spike, the mathematical model of rectifier output voltage is established. Based on the model, the mechanism of voltage spike is explored, deriving two main reasons: one is the wide input voltage, and the other is the resonance between the transformer leakage and the rectifier diode junction capacitor. Consequently, it is more pertinent to address the problem and improve the system’s reliability.

A new quench protection circuit for a 3.5 T MRI SC magnet has been designed based on cryogenic property of rectifier diodes performance of the quench protection circuit is studied by a numerical simulation with the discussion of the influence of heaters' location and startup time on quench protection.

This paper presents a hybrid-type full-bridge dc/dc converter with high efficiency. Using a hybrid control scheme with a simple circuit structure, the proposed dc/dc converter has a hybrid operation mode. Under a normal input range, the proposed converter operates as a phase-shift full-bridge series-resonant converter that provides high efficiency by applying soft switching on all switches and rectifier diodes and reducing conduction losses. When the input is lower than the normal input range, the converter operates as an active-clamp step-up converter that enhances an operation range. Due to the hybrid operation, the proposed converter operates with larger phase-shift value than the conventional converters under the normal input range. Thus, the proposed converter is capable of being designed to give high power conversion efficiency and its operation range is extended. A 1-kW prototype is implemented to confirm the theoretical analysis and validity of the proposed converter.

This paper presents a soft switching technique used along with the series connected transformer to run a PMDC motor. The three level PWM circuits with two active switches and the capacitors are connected in parallel with it. The two switches are reduced in the existing method. Instead of those two switches two capacitors are used to reduce the switching losses. The series resonant converter is used to achieve ZVS turn-on for all power switches and zerocurrent switching for all rectifier diodes. The switching losses of the switches and the reverse recovery loss of the diodes are reduced. The resonant converter has wide range of switching frequency that can be overcome by adopting the PWM method to regulate the output voltage. The series connected transformer is used in the primary and secondary side to balance and share the current which is supplied to the load. The PMDC motor can be used as load. The conventional method does not use any controller to control the resistive load. The speed of the motor can be sensed by using the fuzzy logic controller.The leakage inductance can be reduced by making the frequency constant.

This paper presents a practical way of identifying the defective diodes of an alternator. For this purpose are presented a series of experimental tests of some car alternators. There are detailed the automatic voltage control by modifying the excitation current of the generator and different waveforms of the voltage obtained when one or more rectifier diodes are damaged. The paper ends with conclusions and references.