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This paper presents a GaN Transistor based 90W ac/dc adapter with a Buck-PFC stage and an isolated Quasi-Switched-Capacitor (QSC) dc/dc stage. In the dc/dc stage, two different QSC converters are proposed. Compared to Flyback and LLC resonant converters, the QSC converters feature: 1) reduced voltage stress on the primary-side switches to 2/3 of the input voltage; 2) reduced voltage stress on the...
Transformer parameters such as leakage inductance and self-capacitance are rarely calculated in advance during the design phase, because of the complexity and huge analytical error margins caused by practical winding implementation issues. Thus, choosing one transformer architecture over another for a given design is usually based on experience or a trial and error approach. This work presents equations...
High voltage high frequency (HF) transformer provides the isolation between high and low dc link voltages in dual active bridge (DAB) converters. Such DAB converters are finding wide applications as an intermediate DC-DC converter in transformerless intelligent power substation (TIPS), which is proposed as an alternative for conventional distributiontransformer connecting 13.8 kV and 480 V grids....
Considering stability, the loadability of long line ac transmission system is typically far below its thermal limitation. To partially address this problem, a hybrid ac/dc approach is investigated in this paper by superposing dc current on ac currents along existing ac lines, and no changes of insulators, towers and conductors are required. First, detailed performance comparison between line commutated...
An important functionality of the Solid State Transformer (SST) is the integration of renewable energy sources within the topology itself, acting as a renewable energy hub. Due to the fluctuating nature of the renewable energy source, such integration becomes a challenge and energy storage becomes a requirement. In this paper a topology variant of single phase SST with multi limb magnetic core is...
LLC Resonant converters have been popular in recent years by providing highly-efficient, compact isolated power conversion for numerous applications. 48V to 12V and 400V to 12V step-down isolated converters are often required in server, telecom and automotive applications. While the switching losses in LLC converters are eliminated due to zero-voltage switching, the primary-side switch output capacitance...
This paper presents the design and optimization of MEMS-microfabricated toroidal inductors targeted for use in integrated power electronics. The process is based on MonteCarlo inductor synthesis, performance evaluation based on analytic inductor models and circuit simulation, and Pareto-optimal filtering. The models and simulation are verified through comparison with magnetic finite element analysis...
In this paper, the common mode (CM) EMI noise characteristic of three popular topologies of resonant converter (LLC, CLL and LCL) is analyzed. The comparison of their EMI performance is provided. A state-of-art LLC resonant converter with matrix transformer is used as an example to further illustrate the CM noise problem of resonant converters. The CM noise model of LLC resonant converter is provided...
In the LLC resonant converter, the air gap is generally positioned in the core of the transformer for proper magnetizing inductance. Traditional transformer design methods assume infinite permeability of the core and no energy stored in the core. The improved design methodology for the gapped transformer is proposed with the optimum relative permeability and gap selection to meet the temperature rise...
Induction cookers are usually designed to deliver up to several kilowatts per burner, working above 20 kHz. These appliances are arranged by means of planar-spiral inductors, made of conventional multi-stranded litz-wire, whose size can reach up to tens of centimeters. In this work, a PCB implementation of such inductors is proposed in order to replace the conventional windings, with the objective...
We present a novel, wafer-level fabrication method of 3D solenoidal microtransformers using an automatic wire bonder. Automatic wire bonders allow to precisely shape 25 μm diameter wire around prefabricated yokes or magnetic cores within seconds. Former reports of wire bonded microcoils treated individual solenoids showing low mutual inductances, whereas in this study transformers with strongly coupled...
An approach to the ultimate integration and miniaturization of MEMS-based 3-D magnetic components involves embedding the volume of the magnetic structures within the volume of the silicon wafer itself, exploiting microfabricated windings to create current paths, and utilizing embedded magnetic cores within the limited footprint of these components to boost the magnetic performance. However, this embedding...
An optimize design process of inductors and transformers used in switching power converters is presented in this paper. An analytical modeling of conductor physical behavior was developed to match optimization requirements, and used to compare various components with different cores — coils geometries and wire technologies. Rigorous analytical modeling was applied to achieve minimization of the losses,...
Bearing currents cause a reduction of ball bearing's lifetime in electronically commutated permanent magnet motors. To compensate the lifetime decreasing factors, a tradeoff between special bearings and additional changes in the machine design have to be found. Stator grounding, for example, keeps the bearing voltage low and thus guarantees a long fan system's lifetime, however, results in a higher...
Traditional induction heating cooktops typically employ a circular planar coil in resonance excited by a switching inverter. This configuration results in stray magnetic fields below the coil and non-uniform heating profile on the top. This paper presents the concept of multiphase, multi-resonant induction heating using a Halbach winding arrangement to eliminate the shortcomings of the traditional...
A new interleaved three-phase PFC AC-DC singlestage multilevel is proposed in this paper. The proposed converter uses a flying capacitor structure with standard phase-shift PWM to improve efficiency, particularly at light load conditions. In the paper, the operation and its steady-state characteristics are explained and its design is discussed. The feasibility of the new converter is confirmed with...
In this paper, a high efficiency high power density matrix transformer structure for LLC resonant converters is proposed. Matrix transformer is help to reduce leakage inductance and the AC resistance of windings. Flux cancellation method is utilized to reduce core size and loss. Synchronous Rectifier (SR) devices and output capacitors are integrated into secondary windings to eliminate termination...
This paper presents a compact bi-directional solidstate transformer (SST) based on a current-source topology, featuring high-frequency galvanic isolation and only two minimal power conversion stages. The topology, referenced as Dynamic Current or Dyna-C, can be configured for multiterminal DC and/or multi-phase AC applications. The Dyna-C is robust, can be stacked for MV applications, and be paralleled...
Wireless power transmission region stands out for its convenience in the applications where several terminals or movable terminals need to be charged. The conventional single coil excited charging region has the drawback of distance and angle limitation. To overcome the shortcoming, a charging region which is constructed by four emitting coils is proposed in this paper. This four emitting coils configuration...
This paper discusses a development for high output of 2.5 MHz inverter without fast-switching semiconductor switches. This inverter consists of a multi-phase inverter using conventional silicon semiconductor switches and multiple core transformers. In this paper, a principle of drop in inverter output voltage which reduces the inverter output voltage due to a relationship between dead-time and a leakage...
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