• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.1
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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.

• Computers and Concrete
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• v.27 no.3
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• pp.269-282
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• 2021

A dynamic analytical solution for a simply supported, rectangular functionally graded plate with a porous middle layer under time-dependent load based on a refined third-order shear deformation theory with a cubic variation of in-plane displacements according to the thickness and linear/quadratic transverse displacement is presented. The solution achieved in the trigonometric series form and rests on the Green's function method. Two porosity types and their influence on material properties, and mechanical behavior are considered. The network of pores is assumed to be empty or filled with low-pressure air, and the material properties are calculated using the power-law distribution idealization. Numerical calculations have been carried out to demonstrate the accuracy of the kinematic model for the dynamic problem, the effect of porosity, thickness of porous layers, power-law index, and type of loading on the dynamic response of an imperfect functionally graded material plate.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.332-338
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• 2022

This study proposes a battery state-of-health estimation method by applying a feature extraction technique. The technique that can improve estimation performance is the process of identifying and extracting meaningful data. To apply a data-driven-based aging state estimation method to batteries, health indicators are used as training data. However, limitations occur in extracting health indicators from charge/discharge cycles. This study proposes a deep-learning-based battery state-of-health estimation method that applies feature extraction techniques to compensate for this problem. According to the performance evaluation result of the proposed method, it has a low estimation error of 0.3887% based on an absolute error evaluation method.

• ETRI Journal
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• v.44 no.6
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• pp.955-965
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• 2022

A low Earth orbit (LEO) satellite constellation could be used to provide network coverage for the entire globe. This study considers multi-beam frequency reuse in LEO satellite systems. In such a system, the channel is time-varying due to the fast movement of the satellite. This study proposes an efficient power and bandwidth allocation method that employs two linear machine learning algorithms and take channel conditions and traffic demand (TD) as input. With the aid of a simple linear system, the proposed scheme allows for the optimum allocation of resources under dynamic channel and TD conditions. Additionally, efficient projection schemes are added to the proposed method so that the provided capacity is best approximated to TD when TD exceeds the maximum allowable system capacity. The simulation results show that the proposed method outperforms existing methods.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.8
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• pp.93-97
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• 2004

Since powerline for powerline communications (PLC) is designed for supplying electric power using 60 Hz wave, they will have different electrical behaviors for high data rate PLC whose bandwidth is allocated between 1 MHz and 30 MHz. Thus, it is necessary to investigate the different properties in this frequency bandwidth for the high data rate PLC. In this paper, low voltage (220V) powerline impedance for indoor high data rate PLC in between 1 MHz and 30 MHz is measured. For measurement a low voltage coupling unit is made and a vector network analyzer is used. A T-equivalent circuit of the low voltage coupling unit is obtained and then powerline impedance is derived by measuring the reflection coefficient of the total powerline network. With the method proposed, impedance is measured in case of a general korean apartment and its property is analyzed. Measurement shows that the average impedance is about 100Ω.

• Journal of the Korea Society for Simulation
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• v.18 no.3
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• pp.13-21
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• 2009

The sensor nodes that form a wireless sensor network must perform both routing and sensing roles, since each sensor node always has a regular energy drain. The majority of sensors being used in wireless sensor networks are either unmanned or operated in environments that make them difficult for humans to approach. Furthermore, since many wireless sensor networks contain large numbers of sensors, thus requiring the sensor nodes to be small in size and cheap in price, the amount of power that can be supplied to the nodes and their data processing capacity are both limited. In this paper, we proposes the WSN(Wireless Sensor Network) algorithm which is applied sensor node that has low power consumption and efficiency measurement. Moreover, the efficiency routing protocol is proposed in this paper. The proposed algorithm reduces power consumption of sensor node data communication. It has not researched in LEACH(Low-Energy Adaptive Clustering Hierarchy) routing protocol. As controlling the active/sleep mode based on the measured data by sensor node, the energy consumption is able to be managed. In the event, the data is transferred to the local cluster head already set. The other side, this algorithm send the data as dependent on the information such as initial and present energy, and the number of rounds that are transformed into cluster header and then transferred. In this situation, the assignment of each node to cluster head evenly is very important. We selected cluster head efficiently and uniformly distributed the energy to each cluster node through the proposed algorithm. Consequently, this caused the extension of the WSN life time.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.378-379
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• 2012

Nowadays, great energy consumption in advanced electrical industry has called up the great y efficiency. Electric power IT industry such as intelligent electric power system is receiving great attention and being marked up as a new growth engine. Through Intelligent electric power system, the electric power supply can be balance optimized according to demand, giving huge cost savings advantage for energy imports, infrastructure construction and operation. Nevertheless, the intelligent system promotes better reliability in power supply. Manual electric power management using man power appears to be non-practical. Real time electric power management on all facilities and equipment can be done through an intelligent electric power system, any accident break out issue can be easily recorded and recognized. In this paper, a fully integrated intelligent switchgear electric management system is developed to monitor and remote control the electrical switch based on smart phone. The proposed system is superior than the existing switchgear management system's weakness and can sharply improve effectiveness and stability with low cost. In future, the proposed system is expected to be greatly contributed to the advancement of the IT industry in electric power management.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.89-94
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• 2007

For successful implementation of multi-standard transmitter, reconfigurable architecture and component design are essential. This paper presents a reconfigurable CMOS power amplifier designed CMOS 0.25 um process. Designed power amplifier can be operated at 0.9, 1.2, 1.75, and 1.85 GHz. Also, it can be used at 2.4 GHz by using bonding wire inductor. The interstage matching network is composed of two inductors and four switches, and operation frequency can be varied by controlling switches. Proposed power amplifier can be used as a power amplifier in low power applications such as ZigBee or Bluetooth application and used as a driver amplifier in high power application such as CDMA application. Designed power amplifier has 18.2 dB gain and 10.3 dBm output power at 0.9 GHz. Also, it represented 10.3 (18.1) dB gain and 5.2 (10) dBm output power at 1.75 (2.4) GHz.

• The KIPS Transactions:PartC
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• v.17C no.5
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• pp.433-440
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• 2010

Energy efficiency, low latency and scalability for wireless sensor networks are important requirements, especially, the wireless sensor network consist of a large number of sensor nodes should be minimized energy consumption of each node to extend network lifetime with limited battery power. An efficient algorithm and energy management technology for minimizing the energy consumption at each sensor node is also required to improve transfer rate. Thus, this paper propose no-overlap multi-pass protocol provides for sensor data transmission in the wireless sensor network environment. The proposed scheme should minimize network overhead through reduced a sensor data translation use to searched multi-path and added the multi-path in routing table. Proposed routing protocol may minimize the energy consumption at each node, thus prolong the lifetime of the sensor network regardless of where the sink node is located outside or inside the received signal strength range. To verify propriety proposed scheme constructs sensor networks adapt to current model using the real data and evaluate consumption of total energy.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.228-230
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• 2004

ZigBee Alliance is a network designed for low-cost and very low-power short-range wireless communications. The ZigBee Alliance is a consortium formed by several leading semiconductor and industrial manufactures, and end users. One of the tasks of this organization is the definition of the networking support and applications profiles that will use IEEE Std 802.15.4-compliant transceivers. In the case of IEEE Std 802.15.4, the ZigBee Alliance is an organization that has led the development of the upper layers, through the definition of application profiles. We have implemented ZigBee home control system, however we have not fully implemented. Because of the ZigBee is not perfectly standarded. We will have to implement according to ZigBee Specifications.