• Journal of Power Electronics
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• v.14 no.5
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• pp.882-889
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• 2014

This paper presents a zero voltage switching (ZVS) converter with three resonant tanks. The main advantages of the proposed converter are its ability to reduce the switching losses on the power semiconductors, decrease the current stress of the passive components at the primary side, and reduce the transformer secondary windings. Three resonant converters with the same power switches are adopted at the low voltage side to reduce the current rating on the transformer windings. Using a series-connection of the transformer secondary windings, the primary side currents of the three resonant circuits are balanced to share the load power. As a result, the size of both the transformer core and the bobbin are reduced. Based on the circuit characteristics of the resonant converter, the power switches are turned on at ZVS. The rectifier diodes can be turned off at zero current switching (ZCS) if the switching frequency is less than the series resonant frequency. Therefore, the reverse recovery losses on the rectifier diodes are overcome. Experiments with a 1.6kW prototype are presented to verify the effectiveness of the proposed converter.

• Journal of Power Electronics
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• v.14 no.3
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• pp.478-487
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• 2014

This study presents a new interleaved three-level zero-voltage switching (ZVS) converter for high-voltage and high-current applications. Two circuit cells are operated with interleaved pulse-width modulation in the proposed converter to reduce the current ripple at the input and output sides, as well as to decrease the current rating of output inductors for high-load-current applications. Each circuit cell includes one half-bridge converter and one three-level converter at the primary side. At the secondary side, the transformer windings of two converters are connected in series to reduce the size of the output inductor or switching current in the output capacitor. Based on the three-level circuit topology, the voltage stress of power switches is clamped at $V_{in}/2$. Thus, MOSFETs with 500 V voltage rating can be used at 800 V input voltage converters. The output capacitance of the power switch and the leakage inductance (or external inductance) are resonant at the transition interval. Therefore, power switches can be turned on under ZVS. Finally, experiments verify the effectiveness of the proposed converter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.798-802
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• 2013

In a conventional DC power supply used for CO2 laser, the circuit elements such as a rectifier bridge, a current-limiting resistor, a high voltage switch, energy storage capacitors ans a high-voltage isolation transformer using high turn ratio are necessary. Consequently, those supplies are expensive and require a large space. Thus, laser resonator and power supply should be optimally designed. In this paper, we propose a new power supply using high frequency resonance phenomena for CW(Continuous wave) CO2 laser (maximum output of 23W with discharge length of 450mm). It consists of a transformer including leakage inductance, magnetizing inductance and half-bridge converter, a three-stage Cockcroft-Walton and PFC(Power factor correction) circuit. The output ripple voltage can be controlled the minimum of 0.24% under the high frequency switching of 231kHz. Furthermore, the output efficiency was improved to 16.4% and the laser output stability of about 5.6% was obtained in this laser system.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.344-347
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• 2001

A high frequency resonant inverter consisting of three unit half-bridge serial resonant inverter used as power source of induction heating at high frequency is presented in this paper. As a output power control strategy, tine-sharing gate control method is applied. The analysis of the proposed circuit is generally described by using the normalized parameters. Also, according to the calculated characteristics value, a method of the circuit design and operating characteristics of the inverter is proposed. This paper proves the validity of theoretical analysis through the experiment. This proposed inverter show that it can be practically used in future as power source system for induction heating application, DC-DC converter etc.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2001.11a
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• pp.123-127
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• 2001

In this paper, prototype high-power-factor single-stage electronic ballast for fluorescent lamps is designed and implemented. A new low cost single stage high power factor electronic ballast for fluorescent lamps is based on integration of two-boost converter and LC type high frequency resonant converter. A ballast is obtained by simple construction, because full bridge rectifier diode is eliminated and simple control circuit is applied. Using two boost converter operating positive and negative half cycle respectively at line frequency (60Hz), operation in discontinuous conduction mode performs high power factor. The experimental results Show the good performance as PF 0.99, $A_{THD}$ 15.4%, and CF 1.65 at Output 63.5W.W.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.670-672
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• 2004

In this paper, single phase boost converter with low current harmonic components and high power factor are proposed. A single-phase half-bridge rectifier based on a neutral point switch clamped scheme is proposed to draw a nearly unity power factor and regulate the DC link voltage. Three power switches are employed in the proposed rectifier. This rectifier is controlled to generate a bipolar or unipolar PWM voltage waveform on the AC side. The proposed converter is implemented by a digital signal processor.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1129-1131
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• 2001

A new low cost single stage high power factor electronic ballast for fluorescent lamps is presented in this paper. The proposed topology is based on integration of two-boost converter and LC type high frequency resonant converter. A ballast is obtained by simple construction, because full bridge rectifier diode is eliminated and simple control circuits is applied. Using two boost converter operating positive and negative half cycle respectively at line frequency (60Hz), operating in discontinuous conduction mode performs high power factor. The simulated and experimental results for 64W fluorescent lamps operating at 45kHz switching frequency and 110V line voltage have been obtained.

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

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.99-103
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• 2003

Recently, a fuel cell with low voltage and high current of electronic output characteristics is remarkable for new generation system. It needs both a dc-dc boost converter and do-ac inverter to be used in domestic power. Therefore, this paper presents do-dc boost converter with ZVS for fuel cell generation system This topology has several advantages, which are ZVS characteristics of all of main and auxiliary switches, reduction of reactor component size because of high frequency switching, and low rated voltage stress of the switches. In this paper, theoretical analysis, operation principle, and design procedures are presented. And simulation results from Pspice are presented to validate the theoretical analysis.

• Journal of Power Electronics
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• v.12 no.2
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• pp.233-241
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• 2012

This paper presents a design of a 30kW 250V/530V bidirectional DC-DC converter to be used in an electrical car. A detailed explanation of the design is given. The system uses two phase shifted half bridge (boost and buck) topologies to reduce the ripple current in the output capacitor. The converter has an efficiency of 95% at nominal power. It works as a constant voltage in one direction and as a constant current in the other to charge the batteries. Simulations and measurement are done at high power to test the efficiency.