• 전력전자학회논문지
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• 제26권1호
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• pp.9-15
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• 2021

In multi-string light-emitting diode (LED) driver system, current balancing is crucial because the brightness of LED is directly related to its forward current. This paper presents a novel LED current balancing topology using current-fed Z-source converter. With the proposed structure, currents flowing through two LED strings are automatically balanced owing to the charge-balance condition on capacitors. Operation of the proposed converter is simple and the proposed converter uses only one active switch and one diode. Moreover, low-side gate driving can be used to operate the active switch. To verify the operation of the proposed LED current balancing converter, a prototype is built and tested with different numbers of LEDs.

• 전력전자학회논문지
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• 제26권4호
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• pp.249-255
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• 2021

A novel current balancing technique for multichannel light-emitting diode (LED) that uses a series resonance and coupled inductor is proposed in this paper. The proposed LED driver balances output currents through frequency control and enables zero-voltage switching. The proposed converter utilizes the charge balance condition of the resonant capacitor and the current sharing function of the coupled inductor to achieve whole LED current balancing without an additional controller. The proposed coupled inductor can integrate the current balancing function and the resonant inductor, so the power density can be increased by reducing the number of magnetic devices. A 40 W prototype is built to verify the validity of this LED driver, and the experimental results are successfully obtained.

• 전력전자학회논문지
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• 제26권1호
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• pp.66-73
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• 2021

This study presents a novel four-channel light-emitting diode (LED) current balancing topology using a current-fed hybrid quasi-Z-source converter. With the proposed structure, currents flowing through four LED strings are automatically balanced owing to the charge (amp-sec) balance condition on capacitors. Thus, automatic current balancing of the proposed driver is simple and precise. In addition, the proposed LED driver uses only one active switch and three diodes. The operating principle and characteristics of the proposed four-channel LED driver are analyzed in detail. To verify the operation of the proposed LED driver, a prototype is built and tested with different numbers of LEDs.

• 전력전자학회논문지
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• 제21권4호
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• pp.320-327
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• 2016

We propose a multi-channel current-balancing single switch light-emitting diode (LED) driver for a 3D TV. Conventional LED drivers require non-isolated DC/DC converters as many as the number of LED channels, whereas 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 simple structure with low cost and high efficiency. In particular, because its power switch can be turned off under the zero-current switching condition, the proposed driver has desirable advantages, such as improved electromagnetic interference characteristics and high efficiency. Moreover, it only uses a small number of DC blocking capacitors with no additional active devices for the current balancing of multi-channel LEDs. Therefore, the proposed driver exhibits high reliability and cost effectiveness. To confirm the validity of the proposed driver, we perform a theoretical analysis and present design considerations and experimental results obtained from a prototype that is applicable to a 46" LED TV.

• 전력전자학회논문지
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• 제19권6호
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• pp.564-571
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• 2014

A single-stage current-balancing multi-channel light-emitting diode (LED) driver is proposed in this study. The conventional LED driver system consists of two cascaded power conversion stages, i.e., an isolation DC/DC converter and LED driver. LED driver is usually implemented with the same number of expensive boost converters as those of LED channels to tightly control the current through each LED channel. Therefore, its overall system size is not only bulky, but the cost is rather high. By contrast, the proposed LED driver system is composed of a single power stage with the DC/DC converter and LED driver merged. Although the current balancing circuit of the proposed LED driver requires only passive devices instead of expensive boost converters, all currents through multi-channel LEDs can be well balanced. Therefore, the proposed LED driver features a small system size, improved efficiency, and low cost. To confirm the validity of the proposed driver, its operation and performance are verified on a prototype for a 46" LED TV.

• 조명전기설비학회논문지
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• 제27권5호
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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.

• Journal of Power Electronics
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• 제12권6호
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• pp.869-877
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• 2012

This paper presents a current-balancing circuit for security lights that uses parallel-connected LEDs. The parallel connection of LEDs causes current differences between the LED strings because of characteristic deviations. These differences can reduce the lifespan of a particular point of LEDs by thermal spotting. They can also cause non-uniform luminance of the lighting device. Among the different methods for solving these problems, the method using current-balancing transformers makes it easy to compensate for current differences and it has a simple circuitry. However, while the balancing transformer has been applied to AC light sources, LEDs operate on a DC source, so the driving circuitry and the design method have to be changed and their performances must be verified. Thus in this paper, a design method of the balancing transformer network and the driving circuitry for LEDs is proposed. The proposed design method could have a smaller size than the conventional design method. The proposed circuitry is applied to three types of 100-watt LED security lights, which use different LEDs. Experimental results are presented to verify the performance of the designed driving circuits.

• 전기학회논문지
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• 제66권10호
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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.

• 전력전자학회논문지
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• 제20권2호
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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 Power Electronics
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• 제15권2호
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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.