• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.4
• /
• pp.636-642
• /
• 2017

Recently, new power devices, SiC and GaN FETs, are commercialized. They are expected to change power electronics environments. They will raise operating frequencies of power electronic equipments. Accordingly, design method will be changed greatly. In this paper, an 1 MHz resonant converter with fully compensated coreless isolation transformer is proposed, where the primary voltage is proportional to the secondary current and the primary current to the secondary voltage. 30 W prototype is constructed and tested, and its usefulness is verified.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.2
• /
• pp.171-177
• /
• 2004

Piezoelectric transformer(PZT) can be used advantageously in high output voltage power supply. Recently, it also can be used in AC/DC Converter for miniaturizing size nd lightening weight. The modeling of PZT was performed by the calculation method through the physical and electrical constants of the material. The attributes of PZT were derived by an approximate analysis for output voltage gain, and resonant frequency. The proposed method is verified by computer simulation and experiment.

• Proceedings of the KIPE Conference
• /
• 2018.07a
• /
• pp.84-86
• /
• 2018

Active hybrid solid state transformer(AHSST) is newly emerging as a device to maintan the power quality of power distribution. AHSST has a simple structure in which a power electronics device is connected in series to a conventional distribution transformer. The connected power electronics device maintains the constant voltage regardless of the primary grid voltage fluctuation through the secondary voltage control to improve the power quality. It also has a simple structure compare to conventional solid state transformer system and can achieve the same performance with fractionally-rated converter. This paper proposes an multi-level converter based on AHSST system that has a simpler control method and wider voltage control range than the conventional AHSST. The proposed system is verified by simulations.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.12
• /
• pp.1678-1687
• /
• 2013

This paper describes a prototype of 3-phase 3.3kV/220V 6kVA modular semiconductor transformer developed in the lab for feasibility study. The developed prototype is composed of three single-phase units coupled in Y-connection. Each single-phase unit with a rating of 1.9kV/127V 2kVA consists of a high-voltage high-frequency resonant AC-DC converter, a low-voltage hybrid-switching DC-DC converter, and a low-voltage hybrid-switching DC-AC converter. Also each single-phase unit has two DSP controllers to control converter operation and to acquire monitoring data. Monitoring system was developed based on LabView by using CAN communication link between the DSP controller and PC. Through various experimental analyses it was verified that the prototype operates with proper performance under normal and sag condition. The system efficiency can be improved by adopting optimal design and replacing the IGBT switch with the SiC MOSFET switch. The developed prototype confirms a possibility to build a commercial high-voltage high-power semiconductor transformer by increasing the number of series-connected converter modules in high-voltage side and improving the performance of switching element.

• Journal of Power Electronics
• /
• v.7 no.3
• /
• pp.181-190
• /
• 2007

This paper presents a novel circuit topology of a DC bus line series switch and parallel snubbing capacitor-assisted soft-switching PWM full-bridge inverter type DC-DC power converter with a high frequency planar transformer link, which is newly developed for high performance arc welding machines in industry. The proposed DC-DC power converter circuit is based upon a voltage source-fed H type full-bridge soft-switching PWM inverter with a high frequency transformer. This DC-DC power converter has a single power semiconductor switching device in series with an input DC low side rail and loss less snubbing capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge arms and DC bus line can achieve ZCS turn-on and ZVS turn-off transition commutation. Consequently, the total switching power losses occurred at turn-off switching transition of these power semiconductor devices; IGBTs can be reduced even in higher switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules can be realized at 60 kHz. It is proved experimentally by power loss analysis that the more the switching frequency increases, the more the proposed DC-DC power converter can achieve a higher control response performance and size miniaturization. The practical and inherent effectiveness of the new DC-DC converter topology proposed here is actually confirmed for low voltage and large current DC-DC power supplies (32V, 300A) for TIG arc welding applications in industry.

• Proceedings of the KIEE Conference
• /
• 2006.04b
• /
• pp.211-215
• /
• 2006

This paper present the Half-Bridge converter for low current output. In converter system, magnetic components are important devices used for energy storage, energy transfer, galvanic isolation and filtering. The proposed Half-Bridge converter is to reduce the number of magnetic components. The secondary rectification was discussed by comparison of center-tap type with primary center-core transformer winding and primary side-core transformer winding. A prototype featuring 400V input, 10V output, 400kHz switching frequency, and 100W output power.

• Proceedings of the KIEE Conference
• /
• 1999.07f
• /
• pp.2508-2511
• /
• 1999

A non-contact battery charger which transfers energy using magnetic field without any electrical contacts is designed using half-bridge series resonant converter. This converter utilizes series resonance to reduce the undesirable effect of large leakage inductance of the non-contact transformer and ZVS operation can reduce switching losses. In this paper. analysis and design procedure of half-bridge series resonant converter with non-contact transformer is presented. Input voltage is 85VAC ${\sim}$ 270VAC, output voltage and current is 4.1V and 800mA, respectively. Furthermore, a method for calculating the secondary current of the transformer to control battery charging current in constant current charging mode which is required for litium-ion battery is proposed and the performance is verified from experiments.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.48 no.6
• /
• pp.342-348
• /
• 1999

A new welding machine which adopts zero voltage and zero current switching(ZVZCS) full bridge(FB) DC-DC converter is proposed. The proposed ZVZCS FB DC-DC converter uses auxiliary transformer to obtain ZCS for leading leg. It has capability of controlling load current even in short circuit condition and is suitable for arc welding machines. The power rating of the auxiliary transformer is about one 5th to one 10th of the main transformer. Experimental results for 10KW prototype are shown to verify the principle of operation.

• Proceedings of the KIEE Conference
• /
• 2003.04a
• /
• pp.276-280
• /
• 2003

This paper presents a zero voltage and zero current switching (ZVZCS) interleaving two-transistor forward converter for high input voltage and high power application. A phase shift has a disadvantage that a circulating current and RMS current stress, conduction losses of transformer and switching devices increases. Due to this circulating current and RMS current stress, conduction losses of transformer and switching devices increases. To alleviate these problems, we propose an improved interleaving two-transistor forward Zero Voltage and Zero Current Switching (ZVZCS) dc/dc converter using a tapped inductor a snubber capacitor and two snubber diodes attached at the secondary side of transformer. The proposed ZVZCS converter is verified on a 1.8kW, 5kHz experimental prototype.

• Proceedings of the KIPE Conference
• /
• 2002.11a
• /
• pp.121-124
• /
• 2002

The conventional three-level high frequency phase-shifted dc/dc converter has a disadvantage that a circulating current flows through transformer and switching devices during the freewheeling interval. Due In this circulating current and RMS current stress, conduction losses of transformer and switching devices increases. To alleviate these problems, we propose an improved three-level Zero Voltage and Zero Current Switching (ZVZCS) dc/dc converter using a tapped inductor, a snubber capacitor and two snubber diodes attached at the secondary side of transformer The proposed ZVZCS converter is verified on a 7kW, 30kHz experimental prototype.