• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.147-148
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• 2006

Sl-Thyristor는 기존의 Power semlconductor인 단일 IGBT,MOSFET과 비교하여 높은 정격 전압과 대전류의 소호가 가능하며 빠른 turn on swithcing time을 가지는 특성이 있다. 하지만 게이트 드라이버를 이용한 Sl-Thyristor의 turn on 구동시에는 전압구동의 특성과 turn 0ff시에는 전류 구동의 특성에 가까운 구동 특성이 요구되기 때문에 스위칭 요구 특성에 맞는 게이트 드라이버의 설계 및 제어가 쉽지 않다. 본 논문은 펄스 파워 어플리케이션으로 Sl-Thyristor(PT-201 5kV/100A)를 사용하여 pulsed power moduiator용 Sl-Thyristor의 게이트 드라이버의 요구인 빠른 turn on switching 특성과 turn off 시 Si-Thyristor 내의 전하를 빨리 제거하기 위한 조건을 제시하고 있다.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1665-1670
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• 2023

It is shown that in the IBR-2M reactor by the end of the reactor cycle, changes in dynamics are observed associated with a strong weakening of the fast power feedback (PF), as a result of which the reactor becomes oscillatorily unstable. After each week of zero-power operation the negative changes in reactor dynamics disappear and the stability of the reactor is restored. Thus, the reactor undergoes cyclic changes in the oscillatory instability. The correlation between of a fast PF and a slow PF is experimentally observed, which makes it possible to almost completely eliminate the cyclic component of instability by changing the control mode of rods of the control system.

• Journal of Satellite, Information and Communications
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• v.11 no.1
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• pp.1-5
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• 2016

In this paper, High Power Pulsed Amplifier with wide-band characteristic is implemented for L-band Navigational Aid(NAVAID). Due to the characteristics of L-Band NAVAID, implemented SSPA is demanded characteristics of high RF power, high linearity and high efficiency. Therefore, in this paper, efficiency characteristic is improved by modified class F technique. And linearity characteristic is improved by balance structure using hybrid coupler, $2^{nd}$ & $3^{rd}$ harmonic trap and anti-phase technique using non-linear characteristics of drive amplifier. Implemented SSPA shows that bandwidth of 300MHz, RF Output power of 1.5KW and efficiency of 55%.

• ETRI Journal
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• v.33 no.5
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• pp.679-688
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• 2011

A new discrete-amplitude pulse width modulation (DAPWM) scheme for a high-efficiency linear power amplifier is proposed. A radio frequency (RF) input signal is divided into an envelope and a phase modulated carrier. The low-frequency envelope is modulated so that it can be represented by a pulse whose area is proportional to its amplitude. The modulated pulse has at least two different pulse amplitude levels in order that the duty ratios of the pulse are kept large for small input. Then, an RF pulse train is generated by mixing the modulated envelope with the phase modulated carrier. The RF pulse train is amplified by a switching-mode power amplifier, and the original RF input signal is restored by a band pass filter. Because duty ratios of the RF pulse train are kept large in spite of a small input envelope, the DAPWM technique can reduce loss from harmonic components. Furthermore, it reduces filtering efforts required to suppress harmonic components. Simulations show that the overall efficiency of the pulsed power amplifier with DAPWM is about 60.3% for a mobile WiMax signal. This is approximately a 73% increase compared to a pulsed power amplifier with PWM.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.3
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• pp.96-100
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• 2004

The Nd： YAG laser is commonly used throughout many fields such as accurate material processing, IC marking, semiconductor annealing, medical operation devices, etc., due to the fact that it has good thermal and mechanical properties and is easy to maintain. In materials processing, it is essential to vary the laser power density for specific materials. The laser power density can be mainly controlled by the current pulse width and pulse repetition rate. It is important to control the laser energy in those fields using a pulsed laser. In this paper we propose the constant-frequency current resonant half-bridge converter and monitoring of capacitor charging voltage. This laser power supply is designed and fabricated to have less switching loss, compact size, isolation with primary and secondary transformers, and detection of capacitor charging voltage. Also, the output stabilization characteristics of this Nd： YAG laser system are investigated. The test results are described as a function of laser output energy and flashlamp arc discharging constant. At the energy storage capacitor charges constant voltage, the laser output power is 2.3％ error range in 600[V].

• Proceedings of the Korean Vacuum Society Conference
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• 2002.06a
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• pp.200-200
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• 2002

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.4
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• pp.127-132
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• 2001

We describe the pulse forming of pulsed $CO_2$laser using multi-pulse superposition technique. A various pulse length, high duty cycle pulse forming network(PFN) is constructed by time sequence. That is, this study shows a technology that makes it possible to make various pulse shapes by turning on SCRs of three PFN modules consecutively at a desirable delay time with the aid of PIC one-chip microprocessor. The power supply for this experiment consists of three PFN modules. Each PFN module uses a capacitor, a pulse forming inductor, a SCR, a High voltage pulse transformer, and a bridge rectifier on each transformer secondary. The PFN modules operate at low voltage and drive the primary of HV pulse transformer. The secondary of the transformer has a full-wave rectifier, which passes the pulse energy to the load in a continuous sequence. We investigated laser pulse shape and duration as various trigger time intervals of SCRs among three PFN modules. As a result, we can obtain laser beam with various pulse shapes and durations from about 250 $mutextrm{s}$ to 600 $mutextrm{s}$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.6
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• pp.29-37
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• 2012

As the demand for the fresh non-thermal food is increased, it is required to develop the fast and perfect sterilization method. The conventional sterilization method using ultraviolet lamp has some disadvantages such as imperfect sterilization and longer process time. In this research, IPL(Intense Pulsed Light) sterilization system is introduced to overcome the drawbacks of the conventional system, and suitable power supply architecture for the system is discussed. Since the IPL sterilization system uses Zenon lamps which requires the 600~2,100[V] for the lightning and 16~30[kV] for the trigger, the converter for the system should be able to generate the high voltage and to discharge the large amount of energy instantaneously. In this research a new power system architecture which has a modified forward converter topology with two switches for generating high voltage and a capacitor bank to control the energy for the lightning by switching is introduced.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1703-1705
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• 2001

The pulsed Nd:YAG laser is used widely for materials processing and medical instrument etc. It is important to control the laser energy in those fields using a pulsed Nd:YAG laser. In this paper, constant-frequency current resonant half-bridge inverter and Cockcroft-Walton circuit are used to charge the energy storage capacitor variably. This laser power supply is designed and fabricated which has no high-voltage transformer, less switching losses, compact size and capability in varying the laser output power. Also, the output characteristics of this Nd:YAG laser system are investigated. The tested results are described.

• Journal of Welding and Joining
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• v.29 no.3
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• pp.82-88
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• 2011

With a tendency for the application of thin magnesium alloy plates in portable electronic equipment such as cell phone and notebook PC, there is a requirement to develop a welding technology for the lap welding of these thin magnesium alloy. This paper presents the single pulsed laser welding of AZ31B magnesium alloy. The effects of fiber types and parameters such as peak power and pulse width on laser weldability were investigated. The results show that weld defects, especially solidification crack, were always generated in the weld. These defects couldn't be controlled by the simple square pulse, but could be improved through the application of variable pulse. It is because that variable pulse has effect of solidification delay by dropping peak power gradually.