• Journal of Power Electronics
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• v.19 no.2
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• pp.353-362
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• 2019

To address the problem of circulating current loss in the traditional zero-current switching (ZCS) full-bridge (FB) DC/DC converter, a ZCS FB DC/DC converter topology and modulation strategy is proposed in this paper. The strategy can achieve ZCS turn on and zero-voltage and zero-current switching (ZVZCS) turn off for the primary switches and realize ZVZCS turn on and zero-voltage switching (ZVS) turn off for the auxiliary switches. Moreover, its resonant circuit power is small. Compared with the traditional phase shift full-bridge converter, the new converter decreases circulating current loss and does not increase the current stress of the primary switches and the voltage stress of the rectifier diodes. The diodes turn off naturally when the current decreases to zero. Thus, neither reverse recovery current nor loss on diodes occurs. In this paper, we analyzed the operating principle, steady-state characteristics and soft-switching conditions and range of the converter in detail. A 740 V/1 kW, 100 kHz experimental prototype was established, verifying the effectiveness of the converter through experimental results.

• Journal of Power Electronics
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• v.19 no.1
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• pp.278-287
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• 2019

In this study, a zero-crossing spike current issue in a totem-pole bridgeless power factor correction (PFC) converter is comprehensively investigated for the first time. Spike current occurs when input voltage crosses zero, becomes a noise source, and causes severe common mode emission issues. A generation mechanism for electromagnetic interference (EMI) is presented to investigate the EMI problem caused by zero-crossing issue, and a noise spectrum due to this issue is predicted by a theoretical analysis based on the Fourier coefficient of an approximate spike current waveform. Furthermore, a noise reduction method is proposed and then improved to reduce the spike current. Experimental measurements are implemented on a GaN-based totem-pole bridgeless PFC converter, and the spike current can be effectively suppressed through the proposed method. Furthermore, the noise spectrums measured without and with the reduced zero-crossing spike current are compared. Experimental results validate the analysis of the noise spectrum caused by the zero-crossing spike current issue.

• Transactions on Semiconductor Engineering
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• v.2 no.3
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• pp.13-18
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• 2024

This paper proposes a circuit utilizing auto zero technology to minimize offset and enhance accuracy in the reference generator and comparator. As evidence, a comparison between pre and post auto zero usage revealed a reduction of approximately 90% in standard deviation. The proposed circuit was implemented using a 55nm CMOS process, with an input frequency of 781.2 Hz. It achieves an Effective Number of Bits (ENOB) of 8.01 bits and a Signal-to-Noise Distortion Ratio (SNDR) of 49.98 dB.

• The Journal of Sustainable Design and Educational Environment Research
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• v.18 no.4
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• pp.44-57
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• 2019

'Vision Zero' is a fundamental response to rapidly increasing number of traffic accidents. It was first introduced in Sweden in the late 20th century and is spreading worldwide. 'Vision Zero' criticizes an existing traffic safety policy that presupposes a reasonable human beings. It suggests that traffic safety policies should be on the possibility of making mistakes by irrational beings. Under the ethical vision that human life and health cannot be exchanged for any other social benefits, the policy issue should allow to make zero out the death rate and serious injuries of traffic accidents while allowing minor injuries. 'Vision Zero' argues that the government should design an environment in which individual mistakes never lead to fatal accidents. 'Vision Zero', which shows a different perspective from existing policies regarding safety ultimate goal, is spreading from traffic safety to other areas such as health, safety and well-being. This study examines the implication of the Korea's school safety policy from the perspectives of 'Vision Zero' on the five areas : "for what", "from what", "by what", "by whom", and "how". The study is intended to establish a new directions and challenges of school safety policy in Korea through an analytical discussions on 'Vision Zero'.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.4
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• pp.143-148
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• 2020

In the case of a system that detects and controls the phase of an alternating voltage, the analog control method compensates the phase offset part by filtering for the detected phase and applies it to the control. However, in the digital control method, precise control cannot be achieved due to an error between the operating frequency of the microprocessor or the microcontroller and the input phase time when controlled using such phase detection. In general, when the method used is a certain time, the accumulated error is compensated and adjusted at random. To solve this problem, a method of detecting a zero point in real time and compensating for the operating frequency of the microprocessor is needed. Therefore, the research to be performed in this paper to reduce these errors and apply them to precise digital control is as follows. 1) Research on how to implement Zero Crossing Detection algorithm through simulation modeling to compensate the zero point to match the operating frequency through detection. 2) A study on the method of detecting zero points in real time through the Zero Crossing Detection design using a microcontroller and compensating for the operating frequency of the microprocessor. 3) A study on the estimation of the rotor position of BLDC motors using the Zero Crossing Detection circuit.

• Journal of the Chungcheong Mathematical Society
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• v.19 no.1
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• pp.49-56
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• 2006

A convergence behavior is under investigation near a simple real zero for the k-fold pseudo-Olver's method defined by extending the classical Olver's method. The order of convergence is shown to be at least k+3. The asymptotic error constant is explicitly given in terms of k and the corresponding simple zero. Various numerical examples with a proposed zero-finding algorithm are successfully confirmed with the use of symbolic and computational ability of Mathematica.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.1930-1932
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• 1997

Instantaneous active/reactive powers are defined in three phase four wire systems. The definition can be generally applicable to any source conditions and load conditions including nonlinear circuits. The zero-sequence power resulted from the zero-sequence voltage and zero-sequence current between two sub-systems affects both to the instantaneous active and reactive powers. The zero-sequence current can be controlled by compensation of the reactive power without power storage elements.

• Journal of the Korean Data and Information Science Society
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• v.14 no.1
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• pp.45-53
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• 2003

The Zero-Inflated Poisson regression is a model for count data with exess zeros. When the reponse variables have excess zeros, it is not easy to apply the Poisson regression model. In this paper, we study and simulate the zero-inflated Poisson regression model. An real example was applied to this model. Regression parameters are estimated by using MLE's. We also compare the fitness of zero-inflated Poisson model with the Poisson regression and decision tree model.

• Kyungpook Mathematical Journal
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• v.50 no.4
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• pp.465-472
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• 2010

In this paper, we consider two extreme sets of zero-term rank sum of fuzzy matrix pairs: $$\cal{z}_1(\cal{F})=\{(X,Y){\in}\cal{M}_{m,n}(\cal{F})^2{\mid}z(X+Y)=min\{z(X),z(Y)\}\};$$ $$\cal{z}_2(\cal{F})=\{(X,Y){\in}\cal{M}_{m,n}(\cal{F})^2{\mid}z(X+Y)=0\}$$. We characterize the linear operators that preserve these two extreme sets of zero-term rank sum of fuzzy matrix pairs.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1993.10a
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• pp.50-50
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• 1993

이 연구는 선형계획법을 위하여 개발된 프로그램들의 언어 및 자료 구조에 대한 차이를 비교, 분석하고자 한다. 선형계획법을 위하여 사용된 언어로는 C, PASCAL, FORTRAN이 있고 자료구조로는 Full Matrix형태와 Non-Zero Matrix형태를 고려한다. Non-Zero Matrix에서는 프로그램 언어별로 Cursor-Based System을 비교하고자 한다. 위의 실험을 수행하기 위하여 다음의 연구과정을 수행한다. 첫째, Non-Zero Matrix의 이용을 위한 Cursor-Based System과 Pointer-Based System을 설계한다. 둘째, LP프로그램을 위한 Full Matrix와 Non-Zero Matrix의 효율적인 자료구조를 구축한다. 세째, 프로그램 언어와 자료구조별로 LP프로그램의 성능을 비교분석한다.