• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.26-32
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• 2013

The LED has the proportional characteristic between the flux of light and its current and has caused voltage-current deviation on production process. Thus the unbalancing of each LED strings current occurred by its characteristic deviation. This unbalancing reduce a uniformity of the flux of light. Therefore, we researched to design method the LED driver based on DSP and the balancing transformer for a LED current balancing. These are applied to 50W LED module consist of 4 parallel strings. We analyzed the reduction of LED currents unbalance by experimental result from each method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1474-1480
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• 2017

This paper presents a new LED current balancing scheme using double-step-down dc-dc converter. With the proposed structure, the two channel LED currents are automatically balanced without using any dedicated control or auxiliary circuit. In addition, switching loss of the switching devices in the proposed LED driver is lower than that of the conventional buck LED driver. To verify the operation of the proposed LED driver, a hardware prototype is built and tested with different number of LED.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.7
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• pp.374-379
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• 2006

The switch mode power supply is a source of EMI with other equipment as well as with its own proper operation because of rapid changes in voltages and currents within a switching converter. The EMI is transmitted in two forms: radiated and conducted. Conducted noise consists of two categories known as the differential mode and the common mode. Common mode noise current is a major source of EMI in the switch mode Power supply. Recently, a current balancing technique has been studied to reduce the common mode noise. This paper investigates the reduction of common mode noise according to a node expansion of the switch mode power supply which is based on a current balancing technique. In this paper, seven PCB patterns of the forward converter are manufactured and experimented.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.2
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• pp.122-129
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• 2015

In this study, we propose a low voltage stress and cost-effective light emitting diode (LED) driver capable of multi-channel current balancing. Conventional LED drivers require as many boost converters as the number of LED channels, whereas the proposed LED driver requires only one buck converter and several balancing capacitors instead of several expensive boost converters. Additionally, while the components of the boost converter have high voltage stress and depend on the LED driving voltage, components of the proposed driver have about one-half of the voltage stress across all components. The proposed driver exhibits high reliability and cost effectiveness because it only uses few DC blocking capacitors with no additional active devices to balance the current of multi-channel LEDs. The proposed driver exhibits high reliability and cost effectiveness. The validity of the proposed driver is confirmed through a theoretical analysis. An explanation of the design considerations and experimental results were obtained using a prototype applicable to a 46" LED-TV.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.46
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• pp.241-251
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• 1998

There are two methods of load balancing for detail scheduling : One method is to generate an initial schedule and obtain an improved final schedule by load balancing only during a specific period. The other method is to generate an initial schedule and obtain an improved schedule by load balancing from current date(TIMENOW) to unlimited time with the whole manufacturing processes. This paper proposes an algorithm for detail scheduling which can be a practical solution in job shop production or project job type by applying the former method.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.321-329
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• 2015

The static synchronous compensator (STATCOM) of cascaded H-bridge configuration accompanying multiple separate DC sides is inherently subject to the problem of uneven DC voltages. These DC voltages in one leg can be controlled by adjusting the AC-side output voltage of each cell inverter, which is proportional to the active power. However, when the phase current is extremely small, large AC-side voltage is required to generate the active power to balance the cell voltages. In this study, an alternative zero-sequence current injection method is proposed, which facilitates effective cell balancing controllers at no load, and has no effect on the power grid because the injected zero sequence current only flows within the STATCOM delta circuit. The performance of the proposed method is verified through simulation and experiments.

• Journal of Power Electronics
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• v.15 no.2
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• pp.319-326
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• 2015

In this paper, a cost-effective single switch multi-channel LED (light emitting diode) driver is proposed. While conventional LED drivers require as many non-isolated DC/DC converters as the number of LED channels, the proposed LED driver needs only one power switch and several balancing capacitors instead of expensive non-isolated DC/DC converters. Therefore, the proposed driver features a simpler structure, with a lower cost and a higher efficiency. Because its power switch can be turned off under the zero current switching condition, it has very desirable advantages such as improved electromagnetic interference characteristics and high efficiency. Moreover, it uses only a small number of DC blocking capacitors with no additional active devices for the current balancing of multi-channel LEDs. As a result, the proposed driver exhibits high reliability and is cost effective. To confirm the validity of the proposed driver, a theoretical analysis is performed, and design considerations and experimental results obtained from a prototype that is applicable to a 46" LED-TV are presented.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.3
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• pp.22-29
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• 2015

The AC-LED driving system which is connected directly to alternative current source is suitable for commercialization because of it's simple structure and low cost. However, it requires additional circuits compensating for current differences between the parallel connected LED strings. In this paper, we proposed the circuit compensating for current error of the three LED strings using the Y type balancing transformer. The proposed Half-bridge AC Chopper LED driving system used the ferrite material's balancing transformer. at the same time, it is able to dimming control. The proposed system is applied to 80W AC-LED module consist of three parallel strings. Experiment results present that Power factor and THD measured with power analyzer are 0.958 and 26.473% respectively satisfied with IEC61000-3-2 harmonics standard.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.98-105
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• 2014

According to a simple survey on the current status of the assembly line design, it was found that trial and error methods on the basis of experiences have been used mainly in domestic manufacturing industries, even though there exist a lot of excellent line balancing studies. It seems that more practical researches should be carried out to develop user-oriented line balancing tools especially for small and medium-sized enterprises. This study presents a design of the line balancing tool which can support the line balancing tasks of nonspecialists. The proposed design tool is composed of three major modules: pre-process, line balancing, and post-process. In particular, pre-process and post-process are newly proposed to increase its ease of use. We applied the proposed design to a test problem and test result showed that our practical method may contribute to enhance the efficiency of production operations management.

• Journal of Power Electronics
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• v.17 no.3
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• pp.653-663
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• 2017

Multilevel active neutral-point-clamped (ANPC) converter combines the advantages of three-level ANPC converter and multilevel flying capacitor (FC) converter. However, multilevel ANPC converter often suffers from capacitor voltage balancing problems. In order to solve the capacitor voltage balancing problems for five-level ANPC converter, phase-shifted pulse width modulation (PS-PWM) is used, which generally provides natural voltage balancing ability. However, the natural voltage balancing ability depends on the load conditions and converter parameters. In order to eliminate voltage deviations under steady-state and dynamic conditions, the active voltage-balancing control (AVBC) methods of floating capacitors and dc-link capacitors based on PS-PWM are proposed. First, the neutral-point current is regulated to balance the neutral-point voltage by injecting zero-sequence voltage. After that, the duty cycles of the redundant switch combinations are adjusted to balance the floating-capacitor voltages by introducing moderating variables for each of the phases. Finally, the effectiveness of the proposed AVBC methods is verified by experimental results.