• Proceedings of the KIPE Conference
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• 1998.11a
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• pp.60-63
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• 1998

The widely used power supply (Switched Mode Power Supply : SMPS) as a source in order to stabilize direct current for electronics or communication systems has merits, when it is compared to the existing source for stability, such as high efficiency, small size, light weight by means of switching process of the semiconductor device which controls the flow of power. However, due to existence of inductors and capacitors used for charging energy, the source part in electronic or communication systems hasn't reached the speed, that is supposed to get, for achieving smaller size and lighter weight. In order to get smallness in size, it is necessary to increase switching frequency. And that makes devices for measuring energy smaller. Nevertheless, the rise switching frequency brings increases in switching loss, inductor loss, and power loss. Also, the occurrence of surge and noise caused by high frequency switching is getting higher. The resonant converter has been considered as one of methods that give solutions for the problems of SMPS and that method have been paid attention as a source technology in electronics and communication.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.12
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• pp.622-628
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• 2005

This paper is given a full detail of mathematical analyses of input current and output voltage for a novel active type power factor correction (PFC) converter. These are compared with harmonics components of input current for a conventional PFC converter. The proposed PFC converter is constructed in using a new loss-less snubber circuit to achieve a soft switching of control device. Also the proposed converter for discontinuous conduction mode (DCM) eliminates the complicated circuit control requirement and reduces the size of components. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, input power factor is nearly unity and the control method is simple. Particularly, the stored energy of loss-less snubber capacitor is recovered with input side and increases input current from resonant operation. The result is that input power factor of the proposed converter is higher than that of conventional PFC converter. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.1
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• pp.82-91
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• 2017

This paper is a study on the bi-directional DC-DC converter, one of the key elements of 48V-12V dual systems in mild hybrid electric vehicles. Mild hybrid electric vehicles require a bi-directional DC-DC converter that can efficiently transmit power in two directions between a 48V battery and a 12V battery. To develop a bi-directional DC-DC converter with better price competitiveness, upgraded fuel economy, excellent performance and smaller size, this study designed, produced and presented a circuit that improved on the existing one. In the proposed 8-phase bi-directional DC-DC converter, the size of the passive element was reduced through the 8-phase interleaved topology, whereas downscaling had previously posed a difficulty. This study also designed and produced a 2.5kW class prototype. Based on the proposed 8-phase interleaved topology, a size of 227.5 (W) * 172 (L) * 64.35 (H) was achieved. In the boost mode operation and buck operation modes, the maximum efficiency was recorded at 94.04 % and 95.78 %, respectively.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.34-36
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• 2008

This paper is given a full detail of mathematical analyses of input current for novel active type power factor correction(PFC) AC-DC converter of step up-down added electric isolation. These are compared with harmonics components of input current for a conventional PFC converter of electric isolation type. The proposed PFC converter is constructed in using a new loss-less snubber circuit to achieve a soft switching of control device. Also the proposed converter for discontinuous conduction mode(DCM) eliminates the complicated circuit control requirement and reduces the size of components. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, input power factor is nearly unity and the control method is simple. Particularly, the stored energy of loss-less snubber capacitor is recovered with input side and increases input current from resonant operation. The result is that input power factor of the proposed converter is higher than that of a conventional PFC converter. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• Journal of Power Electronics
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• v.14 no.3
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• pp.413-420
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• 2014

The conventional Phase-Shift Full-Bridge (PSFB) converter has a serious voltage spike because of the ringing between the leakage inductance of the transformer and the parasitic output capacitance of the secondary side rectifier switches. To overcome this problem, an asynchronous active clamp technique employing an auxiliary DC/DC converter has been proposed. However, an exact analyses for designing the auxiliary DC/DC converter has not been presented. Therefore, the amount of power that is supposed to be handled in the auxiliary DC/DC converter is calculated through a precise mode analyses in this paper. In addition, this paper proposes a lossy snubber circuit with hysteresis characteristics to reduce the burden that the auxiliary DC/DC converter should take during the starting interval. This technique results in optimizing the size of the magnetic component of the auxiliary DC/DC converter. The operational principles and the theoretical analyses are validated through experiments with a 48V-to-30V/15A prototype.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.98-101
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• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%${\sim}$30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with USN. which are connected to the spectrum analyzer respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.5
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• pp.421-425
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• 2008

In this research, a 8-bit CMOS 2 stage folding A/D converter is designed, For low power consumption and small chip size, the A/D converter is designed by using folding and interpolation circuit. Folding circuit is composed of the transistor differential pairs which are connected in parallel. It reduces the number of comparator drastically. The analog block composed of folding block, current interpolation circuit, and three stage current comparator is designed with differential-mode for high speed operation. The simulation in a $0.35\;{\mu}m$ CMOS process. shows DNL and SNDR of 0.5LSB and 47 dB at 250 MHz/s sampling frequency.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.6
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• pp.25-32
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• 2011

This paper proposes high efficiency current-mode DC-DC buck converter that are suitable for portable devices. The current-mode DC-DC buck converter using adjustable Dead-time control method improves the power efficiency 2~5%. The buck converter has been implemented with a standard 0.35${\mu}m$ CMOS process. The size of this chip is 0.97$mm^2$. The input range of the fabricated DC-DC buck converter is 2.5V~3.3V, and the output is 1.8V. The maximum loading current of the converter is 500mA and the peak efficiency is 93% at 200mA loads.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.3
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• pp.278-283
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• 1997

The rectifier is the main element in the telecom DC power system. This paper investigates the advantages and disadvantages of three rectifier techniques ; thyristor, ferro - resonant, and switched - mode. Compared with other techniques, the switched - mode rectifier tech¬nique offers several advantages such as higher efficiency, smaller size and weight, and lower audible noise. Technical requirements in telecom rectifier plant are also described. Finally, the future trends in telecom powering are discussed in connection with the advance oftelecom net¬works.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.818-823
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• 1998

A three-arm PWM UPS is realizable low price and small size UPS. In this UPS configuration, the center arm operates in both PWM converter mode and PWM inverter mode. Therefore, the operation of this UPS differs from the conventional UPS. In this paper, the three-arm PWM UPS is analyzed and a trial product is realized.