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A transformerless multicellular dc-dc converter has been newly proposed. The capacitively isolated dc-dc cell converters have been applied to develop the multicellular converter without using high frequency transformers. The high voltage transformation ratio is achieved by the ISOP (Input Series Output Parallel) connection topology of the cell converters and the realization of the highly efficient...
An active gate controlled power transfer switch using SiC-MOSFET is proposed to achieve the fault tolerant operation of ISOP (Input Series and Output parallel) multicellular dc-dc converter. The SiC-MOSFET with high temperature capability simplifies the configuration of the protection circuit, and the control of its on-resistance by the active gate control realizes the smooth protection without the...
A multicellular ac-dc converter is proposed to realize highly efficient dc distribution system in data centers. The proposed converter consists of the singe-phase full-bridge ac-dc cell converters using ultralow loss GaN (Gallium Nitride) transistors and the non-regulated highly efficient isolated dc-dc cell converters. These cell converters are connected in ISOP (Input Series and Output Parallel)-IPOS...
Output-inductor-less full-bridge converter for a High-Voltage Direct-Current power distribution system has been proposed. This proposed circuit topology suppresses the surge voltage due to the secondary-side diode's recovery, and miniaturizes the converter because the number of circuit components is reduced. On the other hand, some problems occur, such as the increasing switching-loss of primary switches...
To achieve high power-density isolated dc-dc converter, gallium nitride high electron mobility transistors (GaN-HEMTs) and planar transformer have been used. Also, for the high power-density design, these components are placed close to each other. GaN-HEMTs are significantly affected by the leakage flux of the planar transformer, because of their lateral structure. Therefore, the mutual effects of...
In this paper, a high power-density output-inductor-less full-bridge converter for the HVDC power distribution system is proposed. The new reduction techniques of switching loss and noise in the output-inductor-less full-bridge converter by using SiC-MOSFETs are applied. As the result, the power loss is reduced by 20W in a wide load range, and the noise is also reduced. Furthermore, a high power density...
In this paper, the influence of parasitic components of LLC resonant dc-dc converters operated at MHz-level switching frequency is investigated. In MHz-level switching frequency, value of the parasitic components are getting closer to value of circuit parameters. Therefore, influence of the parasitic components cannot be neglected even in the initial step of the circuit design. In particular, undesirable...
This paper proposes a power-loss reduction technique for a kW-scale isolated dc-dc converter, which installs a novel PWM control to achieve the soft-switching of primary side MOS-FETs. As a result, the efficiency is achieved over 90% in a wide load range. Moreover, the temperature of the primary side MOS-FETs can be reduced by 30 degrees when compared with the conventional method, and the power-density...
This paper proposes a PFM+PWM hybrid controlled soft-switching half-bridge converter which has both benefit of conventional half-bridge converter and LLC converter. Generally, conventional half-bridge converter has good constant current characteristic due to PWM control, however it has some drawbacks of (1) primary side switches and secondary side diodes operate under hard switching, (2) two magnetic...
This paper proposes the simple and seamless operation technique for bi-directional LLC resonant converter. Generally, bi-directional operation of LLC resonant converter is complicated and difficult to control. Because, the switching frequency has to be changed across fsr (series resonant frequency) and the switching sequences (the switching timing between high voltage side and low voltage side) has...
A high-voltage full bridge dc-dc converter has a big problem of high-voltage surge occurrence across secondary-side rectifying diodes. In order to solve this problem, a simple solution with a snubber capacitor has been proposed. This technique provides a prominent effect of surge-voltage suppression. On the other hand, it deteriorates the control characteristics of this converter. In this paper, the...
In this study, integrated H-bridge converter with the Matrix-POL power supply system is proposed. From the simulation results, the validity of the Matrix-POL is revealed. The results revealed that the fast response to the load current and the voltage change can be done with duty and parallel number control by the proposed system.
This paper presents the novel load regulation technique for parallel connected POLs which reads for power supply on chip (power-SoC). In power-SoC, many POLs are implemented on the same chip. In this case, the conventional loop control (feedback control) may have some problem such as oscillation. The proposed strategy regulates the output voltage by changing number of the working POLs under fixed...
This paper proposes the new LLC converter with unique control method. Generally, LLC resonant converter, which is controlled by PFM, has the drawback of (1) difficulty of PWM controllability, (2) difficulty of constant current limitation, and (3) narrow input voltage range limitation. These difficulties come from the resonant operation. In order to overcome those drawbacks, a hybrid control of PFM...
In this paper, the method of the realization of a MHz level switching frequency DC-DC converter for high power-density is presented. For high power-density, Gallium Nitride field effect transistor (GaN-FET) and current-mode resonant DC-DC converter are adopted. In addition, the proposed pulse width modulation (PWM) control method which is suitable for the isolated current-mode resonant DC-DC converter...
This paper proposes the simple and seamless operation technique for bi-directional LLC converter. Generally, bi-directional operation of LLC converter is complicated and difficult to control. Because, the switching frequency has to be changed across fsr (series resonant frequency) and the switching sequences has to be also changed due to resonant characteristics. In order to simplify the switching...
In this paper, a proposed pulse width modulation (PWM) control method for the isolated current-mode resonant DC-DC converter with MHz level switching frequency is presented. The circuit topology is same as a conventional resonant converter with synchronous rectification and without any additional components. The control technique for the output voltage regulation is proposed with the unique PWM control...
Recently, the bi-directional dc-dc converter has been focused on because of the huge demand for diversification of power supply network including battery. The dual active bridge (DAB) dc-dc converter is one of the most popular circuits for bi-directional applications because of its simple structure. However, power efficiency at light load is the intrinsic problem of a bi-directional DAB DC-DC converter...
In this study, integrated buck-boost converter with the Matrix-POL power supply system is proposed. From the simulation results, the validity of the Matrix-POL is revealed. The results revealed that the fast response to the load current and the voltage change can be done with duty and parallel number control by the proposed system.
This paper will discuss about the proposed hardware logic type digital controller for on-board SMPS which has a very small time-delay in control loop. Experimental results of the load current change experiment and the frequency characteristic of open loop transfer function has been described respectively. These results reveal the validity of the proposed technique.
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