• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.12
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• pp.8-14
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• 2015

An effective way to ensure that LEDs produce wanted light output is to use a current driving topology, because the brightness of LEDs is directly related to their current. However, this topology may lead to the lifetime shortening of a illumination system because over-currents may flow through non-damaged LEDs in case some LEDs are damaged. This paper presents an adaptive current control circuits for LEDs, which protect LEDs in a good state by limiting the driving currents according to the number of damaged ones. The proposed control circuits consist of a simple constant-current driver and a micro-controller which monitors the voltage of LED array without any auxiliary current sensors for fault diagnosis. And the driving current is automatically controlled into 6-levels according to the number of failures.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.35-36
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• 2014

본 논문은 Rear Combination LED Lamp 동작 시 전류와 광출력의 변동폭를 최소화하는 LED 조명광원의 특성을 고려하여 정전류 회로의 구현이 유리한 DC/DC 컨버터의 EMC 고효율 필터를 제안하여 외부의 전자계로부터 장애를 유발하지 않고, 일정 수준의 전자파 환경에서도 오동작 없이 원할하게 작동될 수 있도록 관련 기기 상호간의 전파 환경을 개선하는 고효율 Filter를 제안 하고자 한다. 본 논문에서 제안한 Filter는 EMI 측정을 통해 타당성과 우수성을 검증하였다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.586-592
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• 2018

In this paper, HIC with various functions is proposed for the design 140W LED power control circuit. The proposed HIC integrates constant voltage/constant current circuit, short circuit protection circuit, internal constant voltage circuit, and dimmer circuit, thereby reducing the horizontal length of the PCB by 16% comparing with the conventional system. Through various experiments, we verified the performance of each block implemented inside of HIC with numerical results. (Constant voltage variation ratio: 2.9%, dimmer circuit duty variation within 5%, stable short protection at 720 mA) Since the PCB area can be significantly reduced by applying the proposed HIC. It is possible to reduce the PCB manufacturing time which takes up most of the manufacturing time, however, It is expected that the faulted power module can be replaced without replacing the whole PCB, so that maintenance / repair can be made easier.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.6006-6012
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• 2012

General solar street light system needs two separate power supply for charging the battery and driving LED Lamp. In this study, one power supply is used for both charging battery and driving LED lamp. In particular, in order to increase the efficiency of the equipment, (maximum power point tracking: MPPT) was applied which is widely adopted in grid-connected solar systems. LED driver embodied using current control routine of charger into Essential constant current system.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.6 s.312
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• pp.33-39
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• 2006

Trichromatic LED backlight renders higher colour gamut and panel transmittance to the LCDs than the phosphor-converted white LED backlight. In realization, however, several technical challenges arise, such as colour shift, due to the ambient temperature change, brightness decrease along with the temperature increase, colour mixing, minimizing the total number of chips and so on. In this paper we designed and tested the low cost temperature compensating circuit, using a thermistor as a temperature compensating element, for stabilizing the brightness and maintaining the colour coordinates of the trichromatic backlight units. By applying the temperature compensating circuit, the decrement rate of the brightness and colour shift rate were achieved by 54% and 51% respectively comparing with uncompensated case.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.9
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• pp.8-13
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• 2011

In this paper, a mathematical model of the power LED system including the drive circuit will be presented to control the power LEDs current. Using this mathematical model, the constant current adaptive controller will be designed. A constant current drive circuit for power LEDs will be configured using Buck-type converter. Precise constant current controller design is enabled by presenting the mathematical model of power LEDs including the current driving circuits. Using the mathematical model of power LEDs and its drive circuits, the constant current adaptive controller will be designed to obtain the robustness for the parameter uncertainties. In order to verify the validity of the proposed controller, computer simulations are performed.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1219-1226
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• 2017

In this paper, it is performed the optimal design of the UV LED bar which can be used variously. The UV LED Bar emits ultraviolet rays, so it is important to emit ultraviolet rays constantly for the purpose of use. In order to emit a certain amount of ultraviolet rays as ever, the ultraviolet ray emission should be driven by a constant current source within the operable input voltage range. And also the heat dissipation is particularly important because of the long ultraviolet emission retention time due to the UV utilization characteristics. In addition, since human body protection is essential, the algorithm is configured to operate according to human body detection using distance sensor and Bluetooth. Three 365nm UV LEDs were used in series to emit ultraviolet UVA, operating at the constant current of 500mA with an efficiency of 87.5% and a power consumption of 6.006W. The ultraviolet radiation dose was measured at $5.35mW/cm^2$ at the distance of 10 cm when measured by the Lutron ultraviolet measuring instruments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.534-535
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• 2013

최근 LED 기술을 활용한 LED 조명은 밝기와 수명 및 저전력이라는 장점으로 인하여 현재 시중에 급속도로 퍼저 나가고 있다. 이러한 LED를 조명으로 사용하기 위한 기반 기술은 SMPS(Switching Mode Power Supply) 설계 기술이라 할 수 있다. 또한 LED 성능은 입력 전원 상태 및 LED 조명의 부하 조건에 따라 오차가 발생하여 LED등의 균일한 밝기를 유지하는데 기술적으로 많은 어려움이 있다. 본 논문에서는 12[W] 급 LED 다운 라이트에 대하여 LED SMPS의 전류 출력에 대하여 정전류제어를 함으로서 입/출력 조건의 변동에 대응하여 보다 안정적인 LED 등의 균일한 밝기를 유지하기 위한 12[W] 급 LED 다운 라이트용 SMPS에 PFC(Power Factor Correction) 회로를 추가하여 역율을 개선을 하며, 전압 위상에 따른 전류 위상 분포를 규일 비율로 제어 하여 보다 안정적인 밝기를 제공하는 12[W] 급 LED 조명용 SMPS를 개발하여 상품화를 제안하고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.66-72
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• 2016

An LED lighting control system was developed to combine information technology and LED lights for efficient management and energy savings. The system can monitor and control the status of an LED luminaire using Bluetooth wireless communication, sensor technology, and smart phones. An LED lighting control circuit was designed using a temperature sensor, illumination sensor, and Bluetooth module with a fuzzy constant-current control circuit. We extended the lifetime and prevented damage to the LED by optimizing the supply current of the LED luminaire based on the heat-generation temperature of $70^{\circ}C$ of an LED heat sink. We also automatically adjusted the ON/OFF time depending on the ambient illumination of the LED luminaire. By allowing easy control of the LED luminaires on a smartphone, we improved the efficiency and achieved energy savings. The control system was validated through experiments for normal operation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.191-198
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• 2015

The purpose of this study is to develope a current variation control system appropriate to the various LED(Light Emitting Diode) lamps using current control system equipped with microcontroller based voltage regulator of power driving circuit. For this, we will suggest a stable control system of current variation to enable a stable power-supply and current-control, consisting of circuit to minimize the affects on the LED forward voltage using variable resistance and compensating resistance. The method of constant current circuit and energy savings using microcontroller based voltage regulator suggested in this study can be applied to various a big capacity LED lamp to minimize the unnecessay heat generation and to control resistace delicately. Ultimately, we expect the results of this study will upgrade the reliability of LED lamp by supplying the current stably.