• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.11
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• pp.1625-1633
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• 2012

In the lighting industry, a Lighting Emitting Diode (LED) is increasingly used because of many advantages and a eco-friendly product comparing with the conventional lighting. However, the LED lighting has to include various AC/DC converters because the direct current is used for the LED lighting. Among a lot of power converters, the flyback converter is widely used for the LED lighting and includes some electrolytic capacitors for the voltage regulation. But the electrolytic capacitor has shorter lifetime than the LED element. It makes the expected life-time of the converter having the electrolytic capacitor shorter than the LED element. This paper proposes the single-stage PFC flyback converter without electrolytic capacitors. To verify the performance of the proposed converter, simulated and experimental works were carried out.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.366-373
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• 2011

The magnetic switch used in pulsed-power applications is superior in its high repetition rate, high stability, and long lifetime. But magnetic switch was optimized switching operation by manual control. When the load changes, the switching state can not be optimized automatically. In this paper, the auto control method of magnetic switch for high pulsed-power proposed. The magnetic switch is used capacitor charging power supply for high-voltage compressor. The proposed method can be optimized an efficiency of the system by magnetic switch auto control according to load variation. And the proposed method verify the experimental results.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.327-328
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• 2017

This paper presents the power supply system which is made of three units: the capacitor charging and main pulse unit, simmer power supply unit, and series trigger unit. The capacitor charging and main pulse unit charges the capacitor bank by using the series parallel resonant converter and the generated main pulses apply to the lamp. The series trigger unit ionize the xenon gas located in the lamp and the simmer power supply unit sustains the ionized condition. It means that the lamp lifetime and efficiency are advanced by reducing the number of triggering. Not only the operation of the proposed system but also the performance of each unit will be verified by the experimental results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.510-511
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• 2017

In this paper, we have studied to minimize the lifetime and fault occurrence of LED fixtures, which have a short lifetime and frequent faults. In the current LED chip, the lifetime is semi-permanent, but compared to the lifetime of the LED chip, Drivers do not last long. In recent years, low-priced LED illuminators such as those from China have entered the market, and many consumers are perceiving LED illuminators. In order to solve these problems, we designed an LED illuminator of 25W class by using AC Direct IC, which has a longer lifetime than the conventional driver, by removing the electrolytic capacitor in the LED driving driver which is the cause of the failure.

• Journal of Applied Reliability
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• v.12 no.2
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• pp.67-78
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• 2012

An electric double-layer capacitor(EDLC) is an electrochemical capacitor with relatively high energy density, typically hundreds of times greater than conventional electrolytic capacitors. EDLCs are widely used for energy storage rather than as general-purpose circuit components. They have a variety of commercial applications, notably in energy smoothing and momentary-load devices, and energy-storage and kinetic energy recovery system devices used in vehicles, etc. This paper presents an accelerated degradation test of an EDLC with rated voltage 2.7V, capacitance 100F, and usage temperature $-40^{\circ}C{\sim}65^{\circ}C$. The EDLCs are tested at $50^{\circ}C$, $60^{\circ}C$, and $70^{\circ}C$, respectively for 1,750hours, and their capacitances are measured at predetermined times by constant current discharge method. The failure times are predicted from their capacitance deterioration patterns, where the failure is defined as 30% capacitance decrease from the initial one. It is assumed that the lifetime distribution of EDLC follows Weibull and Arrhenius life-stress relationship holds. The life-stress relationship, acceleration factor, and $B_{10}$ life at design condition are estimated by analyzing the accelerated life test data.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1109-1118
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• 2014

A Fundamental Frequency Sorting Algorithm (FFSA) is proposed in this paper to balance the voltages of floating dc capacitors for Modular Multilevel Converters (MMCs). The main idea is to change the sequences of the CPS-PWM carriers according to the capacitor voltage increments during the previous fundamental period. Excessive frequent sorting is avoided and many calculating resources are saved for the controller. As a result, more sub-modules can be dealt with. Furthermore, it does not need to measure the arm currents. Therefore, the communication between the controllers can be simplified and the number of current sensors can be reduced. Moreover, the proposed balancing method guarantees that all of the switching frequencies of the sub-modules are equal to each other. This is quite beneficial for the thermal design of the sub-modules and the lifetime of the power switches. Simulation and experimental results acquired from a 9-level prototype verify the viability of the proposed balancing method.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1894-1903
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• 2016

In general, electrolytic capacitors are used to reduce power pulsations on PV-panels. However, this can reduce the reliability of the PV AC-module system, because electrolytic capacitors have a shorter lifetime than PV-panels. In addition, PV-panels generate irregular power and inject it into the grid because the output power of a PV-panel depends on the surrounding conditions such as irradiation and temperature. To solve these problems, a grid-connected photovoltaic (PV) AC-module with active power decoupling and energy storage is proposed. A parallel bi-directional converter is connected to the AC module to reduce the output power pulsations of PV-panels. Thus, the electrolytic capacitor can be replaced with a film capacitor. In addition, the irregular output power due to the surrounding conditions can be regulated by using a parallel energy storage circuit. To maintain the discontinuous conduction mode at low irradiation, the frequency control method is adopted. The design method of the proposed converter and the operation principles are introduced. An experimental prototype rated at 125W was built to verify the performance of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.2
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• pp.182-189
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• 2012

In this paper, the input current and output voltage ripple of the soft switching interleaved boost converter was analyzed. Ripples of input current and output voltage with an interleaved method is analysed and as a result, the facts that it has lower ripple current than conventional interleaved method is verified. it means that a capacity of a main inductor can be reduced. Besides, a low capacitance of capacitor which means high lifetime and confidence can be used because of reducing ripples of output voltage. In order to verify the validity of the proposed converter used 10uF film capacitor, experiment was performed, and the efficiency of the proposed converter was measured with variable load and duty conditions.

• Journal of the Korean Solar Energy Society
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• v.39 no.2
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• pp.81-92
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• 2019

When Photovoltaic inverter is connected to grid and used as PVPCS (Photovoltaic Power Conditioning System), 120 Hz AC ripple occurs at the dc-link capacitor voltage. This AC ripple reduces the efficiency of PVPCS and shortens the lifetime of the capacitor. In this paper, we design a notch filter to remove AC ripple. As a result, the AC voltage ripple was removed from the dc link and the THD of the PVPCS output current with the notch filter was lowered. This notch filter is determined by the damping coefficient, the bandwidth coefficient, and the switching frequency. Among these, the switching frequency determines the switching loss and the size of the LC filter, and the PVPCS with the high switching frequency has a greater efficiency loss due to the switching loss than the efficiency improvement by the notch filter. Therefore, it is important to set the optimum switching frequency in the PVPCS with the notch filter applied. In this paper, THD and switching loss of PVPCS output current with notch filter are calculated through simulation, and cost function to calculate optimum switching frequency through data is proposed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.4
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• pp.388-393
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• 2018

In this paper, We developed a high efficiency reflector integrated type 50W AC direct connection type engine to realize miniaturization and weight reduction of product without using SMPS and to design a multistage varistor circuit Reduced costs by reducing the number of parts High reliability is achieved by using a circuit structure that does not use an electrolytic capacitor, thus increasing the lifetime of the LED. In addition, it is possible to manufacture an AC direct-coupled type driving device by using an IC semiconductor and apply an AC direct-coupled type driving device integrated with a reflector so that the lifetime of the device can be fully utilized for the lifetime of the LED, A light source having a plurality of light emitting diode channels including a plurality of light emitting diode channels arranged in series is driven with a rectified voltage.