• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.621-624
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• 2003

In this paper, a novel multilevel inverter using DC-Link voltage combination is presented to reduce the harmonics of output voltage without the output filter inductor. The proposed multilevel inverter can generate 27-level output voltage. It employs three H-bridge cells which consist of single phase full-bridge inverter module. As well as, it can make continuous output voltage level employing the properly three DC-Link voltage ratio. The validity of the proposed inverter is verified through the experimental result using a prototype which can generate a 110[Vac], 60[Hz] output voltage from 12[Vdc], 36[vdc], and 108[Vdc] input voltages

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.154-158
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• 2003

This paper presents an improved soft switching buck converter using a non-dissipative snubber, which is composed of a tapped inductor, two snubber capacitors and three snubber diodes. The proposed buck converter achieves zero voltage turn-off in the main switch and freewheeling diode. The Proposed Soft Switching buck converter is verified through the simulation, relevant equations, analysis and experimental results.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.95-98
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• 2003

A ZVT PWM Boost Converter is proposed to reduce current stresses and conduction losses of main switch in a conventional circuit. By attaching resonant inductor Lr1 in parallel with capacitor Cr, the resonant circulating current is diverted to the additional component and then the main switch is subjected to minimum current stresses same as those in their PWM counterparts. Moreover, the operation of the auxiliary switch in a half wave mode to prevent reverse resonant energy from freewheeling can be able to lessen the conduction losses. The operation principles of the proposed converters are analyzed using the PWM boost converter topology as an example. Theoretically analysis and experimental results verify the validity of the boost converter topology with the proposed circuit.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.603-608
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• 1998

Single-phase diode bridge rectifiers with dc filter capacitor usually operate in discontinuous mode and generate large amounts of harmonic currents. This paper presents a precise harmonic analysis of the line side current in the case that both the filter inductor and the filter capacitor are not infinite. The analytical expressions of the line side performance parameters associated with harmonics are derived. The curves that show the relationship of these parameters associated with harmonics are derived. The curves that show the relationship of these parameters as the functions of circuit parameters are illustrated. By simulation the results are verified to be accurate and the conclusion clearly reveals the relations between the line side performance parameters and circuit parameters.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.250-253
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• 2007

This paper presents a new sustain driver employing energy recovery function to minimize power losses transpired during the operation of plasma display panel. The proposed circuit uses the resonance between the equivalent capacitance of panel and an external inductor to provide/recover energy to/from the panel. The proposed circuit can save the system cost compared with the conventional one, and has high-performance in energy recovery. To verify the validity of the proposed circuit, we implemented experiments based on 7.5 inch AC-PDP.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.479-480
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• 2010

In this paper, the bi-directional soft switching DC-DC converter using ZCT(Zero Current Transition) method is proposed for using battery application system. This topology is composed of soft switching bi-directional buck/boost converter having the ZCT auxiliary circuit with two switches, two resonant capacitors, one resonant inductor. Therefore, the proposed topology can reduce switching loss. To verify the validity of the proposed topology, theoretical analysis and simulation results are presented.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.200-203
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• 2002

This paper presents Continuous-current mode of $S^4$-PFC(Single-Stage Single-switch Power Factor Correction) converter. Proposed converter operates in the continueous current mode(CCM) at full load and discontinuous current mode(DCM) at light load. So, characteristic of proposed converter is no bus voltage stress and Zero Voltage Switching(ZVS) using resonant auxiliary circuit. And. This paper presents characteristic of $S^4$-PFC converter and effect of circuit parameter of proposed converter through the input inductor, PFC capacitor's variation. All of these theory and characteristic verified through the experiment with a 72W(12V, 6A), $90^{kHz}$ prototype converter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.2
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• pp.219-225
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• 1998

A voltage controlled oscillator for the local oscillator in 380 MHz TRS handset is designed and fabricated. To improve the phase noise characteristics, the NEC's 2SC4226 transistor with NF=1.2 at 1 GHz and Toshiba's 1SV229 varactor diode with Q=70 are used. And an inductor of VCO is realized by microstrip line. At the bias condition of 5 V and 10 mA, the output power and phase noise in the operating frequency range of 357∼387 MHz are above 3.7 dBm and 111 dBc/Hz at 12.5KHz offset from the carrier, respectively. And FM sensitivity deviation are within ±0.4 KHz. This VCO is well suited for TRS handset.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.276-280
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• 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
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• 2004.11a
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• pp.59-63
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• 2004

In this paper, active forward converter with snubber circuit - composed of a tapped inductor, a snubber capacitor, two diodes - is proposed. By adding the snubber circuit, ZVS operation became possible even in a smaller magnetizing current conditions than the conventional converter. The operational principles and the equivalent mode analysis of the proposed converter is described and compared to conventional converter. We constructed the prototype active clamped forward converter with 300W output capacity and verified that efficiency of the proposed converter is higher than the conventional converter.