• JSTS:Journal of Semiconductor Technology and Science
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• 제15권3호
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• pp.390-396
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• 2015

This paper proposes a method to reduce flicker when running an AC-power direct-drive type multiple string LED driver IC. The proposed method greatly decreases flicker using one capacitor and P-type MOSFET transistor (PMOS). The flicker index (FI) was reduced by over 40% through experiments, and less than half of the conventional external components are used in the passive valley fill circuit, which gives an advantage in the cost and utilization in the design of LED lighting modules. The 0.35 um 700 V BCD process was used to manufacture this LED driver.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2334-2342
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• 2015

This paper proposes an LED driving circuit with a digital controller, power factor correct (PFC) function, and low light flicker. The key topology of the proposed circuit is a conventional Flyback combined with a pre-stage. As a result, there will be less light flicker than with other one-stage PFC circuits. A digital controller, implemented using a low-cost microcontroller, dsPIC30F2020, will meet PFC and low light flicker. The experimental results validate the functionality of the proposed circuit.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.790-793
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• 2009

In the case of projection type display, it needs to use the screen in order to project the image clearly and wide viewing angle. We have been developing the step in type display system using the smoke screen. However, the image with smoke screen was flickered by gravity and air flow. Then we considered to reduce the flicker of the image and we found that flicker can be reduced and viewing angle becomes more large. This time we report the large viewing angle step in type display system using screen made up with very small particle size smoke and flow controlled nozzle. Hence, at first we considered the most suitable particle for the screen and then the shape of screen and then we constructed the array of flow controlled smoke screen. By the results of experiment we could get considerably high contrast flicker-less image and get the viewing angle more than $60^{\circ}$ by this flow controlled nozzle attached new type smoke screen and make clear the efficiency of this method.

• Journal of Power Electronics
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• 제11권2호
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• pp.228-236
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• 2011

The ${\Delta}\;V_{10}$ or 10-Hz flicker index, as a common method of measurement of voltage flicker severity in power systems, requires a high computational cost and a large amount of memory. In this paper, for measuring the ${\Delta}\;V_{10}$ index, a new method based on the Adaline (adaptive linear neuron) system, the FFT (fast Fourier transform), and the PSO (particle swarm optimization) algorithm is proposed. In this method, for reducing the sampling frequency, calculations are carried out on the envelope of a power system voltage that contains a flicker component. Extracting the envelope of the voltage is implemented by the Adaline system. In addition, in order to increase the accuracy in computing the flicker components, the PSO algorithm is used for reducing the spectral leakage error in the FFT calculations. Therefore, the proposed method has a lower computational cost in FFT computation due to the use of a smaller sampling window. It also requires less memory since it uses the envelope of the power system voltage. Moreover, it shows more accuracy because the PSO algorithm is used in the determination of the flicker frequency and the corresponding amplitude. The sensitivity of the proposed method with respect to the main frequency drift is very low. The proposed algorithm is evaluated by simulations. The validity of the simulations is proven by the implementation of the algorithm with an ARM microcontroller-based digital system. Finally, its function is evaluated with real-time measurements.

• 한국전기전자재료학회논문지
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• 제24권12호
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• pp.944-948
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• 2011

In this paper, flicker noise characteristic and channel hot carrier degradation of NMOSFETs with plasma nitrided oixde (PNO) and thermally nitrided oxide (TNO) are analyzed in depth. Compared with NMOSFET with TNO, flicker noise characteristic of NMOSFET with PNO is improved significantly because nitrogen density in PNO near the Si/$SiO_2$ interface is less than that in TNO. However, device degradation of NMOSFET with PNO by channel hot carrier stress is greater than that with TNO although PMOSFET with PNO showed greater immunity to NBTI degradation than that with TNO in previous study. Therefore, concurrent investigation of the reliability as well as low frequency noise characteristics of NMOSFET and PMOSFET is required for the development of high performance analog MOSFET technology.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.414-417
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• 2008

This paper presents the design and analysis of 2.45GHz Low-IF Mixer using CMOS 0.18um. The Mixer is implemented by using the Gilbert-type configuration, current bleeding technique, and the resonating technique for the tail capacitance. And the design of this Double Balance Mixer is based on its lineaity since it is important in the interference cancellation system. The low flicker noise mixer is implemented by incorporating a double balanced Gilber-type configuration, the RF leakage-less current bleeding technique, and Cp resonating technique. The proposed mixer has a simulated conversion gain of 16dB a simulated IIP3 of -3.3dBm and P1dB is -19dBm. A simulated noise figure of 6.9dB at l0MHz and a flicker corner frequency of 510kHz while consuming only 10.65mW od DC power. The layout of Mixer for one-chip design in a 0.18-um TSMC process has 0.474mm$\times$0.39 mm size.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.267-272
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• 1999

The auxiliary power supply system fur passenger service of railway car has been developed from MA(Motor-Alternator) to CVCF Inverter (Static Inverter). Generally, a customer wants to apply tile new control method and device for auxiliary power supply of railcar However, if the auxiliary power supply is supplied to extended existing line, the maintenance cost of the old system is less expensive than new developed system, so, the customer specifies that the auxiliary power supply has compatibility with existing one completely. At that time, the hardware is nearly same as existing system except small changes of accessories for better performance. This paper describes the flicker control using feed-forward method of auxiliary power supply system for new 50 electric railcars, which are delivered to Korean National Railroad (KNR) Kwa-chon Line. The existing power supply system has damping resistor box to stabilize the DC input (1.5 ㎸). At this time, for better system efficiency the new system has not include resistor box but new control method including feed-forward control is applied. This control algorithm realizes the better stabilization of input power compared to the result of the existing system, which includes resistor box

• 대한전자공학회논문지SP
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• 제37권6호
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• pp.9-16
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• 2000

최근 컴퓨터의 급속한 보급에 따라 고밀도 CRT(cathode ray tube)가 요망되고 있다. 이를 위하여 신호 대역과 주사 속도의 증가에 따른 주사선 수를 증가 시켜야 하고 플리커(flicker)도 줄여야 한다. 플리커 현상은 PC작업을 장시간 하는 경우 더욱 심하게 느껴지므로 플리커 현상을 줄이는 연구가 필요하다. 본 논문에서는 플리커가 덜 느껴지도록 하는 디스플레이 시스템의 설계를 위한 기초 연구로서 CRY에 사용된 인광체의 잔광 특성 및 화면의 밝기에 따른 플리커와 프레임 주파수와의 관계를 정량적으로 해석하였으며, 또한 디스플레이 전화면에 대해서 시각을 고려하여 플리커를 덜 느끼도록 하는 프레임 주파수를 제시하였다.

• 전기학회논문지
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• 제60권9호
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• pp.1651-1655
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• 2011

The reference impedances which is about 95% supply impedance value of residential consumers' supply impedances was published by IEC in 1980. The reference impedances are the standard values for use in determining the voltage disturbance characteristics of electrical equipment like the flicker. In IEC 60725, the reference impedances for premises having service current capacities less than 100A per phase and for service current capacities more than 100A per phase are recommended. And these reference impedances are targeted for the countries using 50Hz power frequency. Because of the frequency difference, the reactance values of the reference impedances will be increased in 60Hz power system like Korea, And also the reference impedances are different significantly each other according to declared voltage variation, power consumption and service wire length etc. Therefore It is needed to calculate the reference impedances suitable for domestic low-voltage power system. In this paper, the reference impedances for service current capacities less than 100A in 220/380V, 60Hz single-phase two wire and three-phase four wire low-voltage system are calculated, And the equations for service current capacities more than 100A to calculate the modulus value of maximum supply impedances are suggested base on IEC 60725 and the reference impedances for those are calculated on service current of 100A per phase.

• ETRI Journal
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• 제37권4호
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• pp.677-684
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• 2015

Recently, orthogonal frequency-division multiplexing (OFDM) was applied to VLC systems owing to its high rate capability. On the other hand, a real-valued unipolar OFDM signal for VLC significantly reduces bandwidth efficiency. For practical implementation, channel estimation is required for data demodulation, which causes a further decrease in spectral efficiency. In addition, the large fluctuation of an OFDM signal results in poor illumination quality, such as chromaticity changes. This paper proposes a spectrally efficient method based on a hidden-pilot-aided precoding technology for VLC with less flickering than a conventional OFDM-based method. This approach can obtain channel information without any loss of bandwidth efficiency while ensuring illumination quality by reducing the flickering effect of an OFDM-based VLC. The simulation results show that the proposed method provides a 6.4% gain in bandwidth efficiency with a 4% reduction in flicker compared to a conventional OFDM-based method.