• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.52 no.12
• /
• pp.632-640
• /
• 2003

In conventional Zero-Voltage-Transition(ZVT) PWM converters, zero-voltage turn-on and turn-off for main switch without increasing voltage/current stresses is achieved at a fixed frequency. The switching loss, stress, and noise, however, can't be minimized because they adopt auxiliary switches turned off under hard-switching condition. In this paper, new ZVS-PWM converters of which both active and passive switches are always operating with soft-switching condition are proposed. Therefore, the proposed ZVS-PWM converters are most suitable for avionics applications requiring high-power density. Breadboarded ZVS-PWM boost converters using power MOSFET are constructed to verify theoretical analysis.

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

• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.264-269
• /
• 1998

A proposed soft-switching buck-boost PWM converter has a lot of advantages, Viz., electric isolation, a high power factor, low switching losses, low EMI noise, reduction of the voltage and current stresses, etc. In a new PFC converter, the switching device is replaced by the loss-less snubber circuit to achieve the zero voltage switching (ZVS) at the maximum current. However, the charging current of the capacitor in the loss-less snubber circuit distorts the input current waveforms. To improve the input current waveform, a new duty factor control method is proposed in this paper.

• Proceedings of the KIEE Conference
• /
• 1998.07f
• /
• pp.1863-1865
• /
• 1998

A class-D zero voltage switching (called soft-switching) inverter with only one capacitor in parallel with both FET, along with an approximate analysis and experimental results, is introduced. The inverter offers both zero turn-on and zero turn-off switching losses, yielding high efficiency at high frequencies. In addition, soft switching reduces switching noise associated with the high frequency ringing at the swithching instants.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.50 no.9
• /
• pp.467-472
• /
• 2001

In conventional zero-current-switching(ZCS) PWM converters, zero-current turn-off for main switch without increasing voltage/current stresses is achieved at a fixed frequency. The switching loss, stress, and noise, however, can\`t be minimized because they adopt auxiliary switches turned off and main switches turned on under hard-switching condition. In this paper, new ZCS-PWM converters of which all switches are always operating with soft-switching condition are proposed. Therefore, the proposed ZCS-PWM converters are most suitable for systems requiring high-power density Breadboarded ZCS-PWM boost converters using power MOSFET are constructed to verify theoretical analysis.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.12 no.4
• /
• pp.90-99
• /
• 1998

The DC/DC power converter increase switching frequency in order to achieve small size, a low noise, and light weight. However, the power switches have high power losses and switching stresses as the switching frequency is increased. Therefore in this paper, the author propose the Soft-Switching Forward-Flyback PWM DC/DC converter using assistant-circuit, based on forward-flyback operation of a high-frequency transformer. The proposed converter scheme is verified by simulation and experiment.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1383-1386
• /
• 2005

Non-isolated OSAKA Converter, which removes a three-phase transformer, is described in this paper. The converter switches once in every half cycle of an AC commercial power source. Therefore, it can solve many problems caused by the high frequency operation. The proposed converter achieves the soft-switching operation and the EMI noise can be reduced. In this circuit, the resonant capacitor, which is used for the soft-switching operation, is utilized for the improvement of an input current waveform. To achieve low cost and compact structure, non-isolated OSAKA converter removes a three-phase transformer of the OSAKA converter. By removing the three-phase transformer, three phase currents occur the interferences each other. To avoid the interference, a new switching method for non-isolated OSAKA converter is preposed. The converter can be constructed by the low-speed large power devices. The converter generates the low distorted input current waveforms with high power factor.

• International journal of advanced smart convergence
• /
• v.8 no.3
• /
• pp.61-68
• /
• 2019

Spatial modulation (SM) is the first proposed space modulation technique. By further utilizing the quadrature spatial dimension, quadrature spatial modulation (QSM) has been developed as an amendment to SM system to enhance the overall spectral efficiency. Both techniques are capable of entirely eliminating interchannel interference (ICI) at the receiver. In this paper, we propose a simple adaptive hybrid switching transmission scheme to obtain better system performance than SM and QSM systems under a fixed transmission date rate. The presented modulator selection criterion for switching between spatial modulator and quadrature spatial modulator is based on the larger received minimum distance of spatial modulator and quadrature spatial modulator to exploit the spatial channel freedom. It is shown through Monte Carlo simulations that the proposed hybrid SM and QSM switching system yields lower error performance than the conventional SM and QSM systems under the same fixed data rate and thus can provide signal to noise ratio (SNR) gain.

• Proceedings of the KIPE Conference
• /
• 1996.06a
• /
• pp.117-120
• /
• 1996

Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. In this paper, the authors propose a DC-DC boost converter of high power by partial resonant switch method (PRSM). The switching devices in a proposed circuit are operated with soft switching and the control technique of those is simplified for switch to drive in constant duty cycle. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. Also the circuit has a merit which is taken to increase of efficiency, as it makes to a regeneration at input source of accumulated energy in snubber condenser without loss of snubber in conventional circuit. The result is that the switching loss is very low and the efficiency of system is high. The proposed converter is deemed the most suitable for high power applications where the power switching devices are used.

• Journal of information and communication convergence engineering
• /
• v.9 no.5
• /
• pp.591-596
• /
• 2011

Image denoising is a key issue in all image processing researches. Generally, the quality of an image could be corrupted by a lot of noise due to the undesired conditions of image acquisition phase or during the transmission. Many approaches to image restoration are aimed at removing either Gaussian or impulse noise. Nevertheless, it is possible to find them operating on the same image, which is called mixed noise and it produces a hard damage. In this paper, we proposed noise type classification method and a mixed nonlinear filter for mixed noise suppression. The proposed filtering scheme applies a modified adaptive switching median filter to impulse noise suppression and an efficient nonlinear filer was carried out to remove Gaussian noise. The simulation results based on Matlab show that the proposed method can remove mixed Gaussian and impulse noise efficiently and it can preserve the integrity of edge and keep the detailed information.