• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.580-582
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• 2008

The object of this paper is develope the PC based controlled high voltage power supply and studies 1.2kW(120kV, 10mA) pulse power X-ray generator possible to adapt fluoroscopy of Dental CT X-ray generator and industrial X-ray pulse power equipment. The developed pulse power X-ray generator consisted of mono-block tank include X-ray tube and high voltage X-ray power supply circuit and high voltage control unit with RS232C/422 communication port. The PC control program of pulse power X-ray generator uses LabVIEW, and the size of high voltage transformer and high voltage generator is minimized by high voltage high frequency inverter has 100kHz switching frequency. Also this paper shows result of X-ray tube voltage and tube current correspond to variable load.

• 설비공학논문집
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• 제6권3호
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• pp.282-290
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• 1994

A numerical model for the analysis and design of orifice pulse tube refrigerators has been developed. Heat transfer coefficient and friction factors in the model vary with time, and the real physical properties such as thermal conductivity and viscosity were used to improve the accuracy of the model. Thermodynamic behavior of the working fluid within pulse tube refrigerators was investigated and the effect of design parameters, such as reservoir volume, orifice diameter, and NTU of regenerator, on the cooling load and COP was shown.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 B
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• pp.486-489
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• 1998

In this paper, we introduced the neural network to reduce force ripple of current controller for a linear pulse motor. In general, conventional position controllers of linear pulse motor disregard the modeling error and load variations, which cause inaccuracy in position control. The proposed current controller based on neural network teaming modifies the current commands in order to reduce force ripple due to these factors. The experiment results show that the proposed controller works efficiently for accurate position control of linear pulse motor.

• 전자공학회논문지A
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• 제31A권8호
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• pp.62-71
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• 1994

A novel semiconductor device is proposed to be used as a processing element for the implementation of pulse-mode neural networks which consists of alternating n' GaAs quantum wells and undoped AlGaAs barriers sandwitched between n' GaAs cathode and P' GaAs anode and in simple circuit in conjunction with a parallel capacitive and resistive load the trigger circuit generates neuron-like pulse train output mimicking the function of axon hillock of biological neuron. It showed the sigmoidal relationship between the frequency of the pulse-train and the applied input DC voltage. In conjunction with MQWIMD the various neural circuits are proposed especially a neural chip monolithically integrated with photodetectors in order to perfrom the pattern recognition.

• Journal of Power Electronics
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• 제16권1호
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• pp.388-397
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• 2016

An error-compensated pulse width modulator (ECPWM) is proposed to improve the baseband harmonic performance and the switching loss of voltage source inverters (VSIs). Selecting between harmonic distortion and switching loss is a design tradeoff in the conventional space vector pulse width modulation. In this work, an accumulated difference in produced and desired phase voltages is considered to adjust the reference signal. This mechanism can compensate for the voltage error in the previous carrier period. With error compensation every half-carrier period, the proposed ECPWM allows one-half reduction in carrier frequency without scarifying baseband harmonic distortion. The proposed modulator is applied to a three-phase VSI with R-L load and a motor-speed-control system for experiments. The measured efficiency and operating temperature of switches confirm the effectiveness of the proposed scheme.

• 한국초전도ㆍ저온공학회논문지
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• 제12권4호
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• pp.36-40
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• 2010

In this paper, a noble method for rapid cooldown of pulse tube refrigerator (PTR) was proposed and experimentally investigated. An orifice pulse tube refrigerator generates refrigeration effect by expansion PV work at the cold-end, and its amount is affected by the orifice valve opening. There exists the optimum valve opening for maximum cooling capacity and it varies as cold-end temperature. It is verified from simulation results using isothermal model that the optimum valve opening increases as the cold-end temperature increases. In the experiments, a single stage orifice pulse tube refrigerator is fabricated and tested. The fabricated PTR shows 97.5 K of no-load temperature and 10 W at 110 K of cooling capacity with the fixed orifice valve opening. From experiments, the initial cooldown curve with four cases of valve opening control scenario are obtained. And it is experimentally verified that the initial cooldown time can be reduced through the control of orifice valve opening.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(2)
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• pp.367-370
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• 2004

We fabricated PLT(5) thin film on $Pt/TiO_x/SiO_2/Si$ substrate by using sol-gel method and investigated leakage current, switching and retention properties. The leakage current density of PLT(5) thin film was $3.56{\times}10^{-7}A/cm^2$ at 4V. In the examination of switching properties, pulse voltage and load resistance were $2V{\~}5V$ and $50{\Omega}{\~}3.3k{\Omega}$, respectively. Switching time had a tendency to decrease from 520ns to 140ns with the increase of pulse voltage, and also the time was increased from 140ns to $13.7{\mu}s$ with the increase of load resistance. The activation energy obtained from the relation of applied pulse voltage and switching time was about 143kV/cm. The error of switched charge density between hysteresis loop and experiment of polarization switching was about $10\%$. Also, polarization in retention was decreased as much as about $8\%$ after $10^5$s.

• 전자공학회논문지S
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• 제35S권8호
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• pp.120-129
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• 1998

본 논문은 PWM(Pulse width Modulation)전압형 인버어터를 사용하여 전원차단 경우나 전압변동 및 부하변동에 의한 출력전류 변화에도 일정한 출력전압을 유지하는 무정전 전원장치에 대해 논하였다. 본 시스템은 전압형 인버어터를 교류전원과 동기시켜 운전하고 정상상태에서는 전원으로부터 운전하고 정상상태에서는 전원으로부터 직류측에 연결된 축전지를 태양전지를 이용한 광기전력효과와 함께 일정전압을 충전하며, 전원의 차단, 전원의 전압변동 및 부하전류의 변화에도 일정한 전압을 유지하도록 하였다. 출력은 PWM방식에 의하여 양호한 파형이 되도록 하고 전원차단과 부하의 상태의 변화 및 전원 전압 변동에도 일정한 전압으로 출력됨을 실험을 통하여 확인할 수 있었다.

• Journal of Magnetics
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• 제17권1호
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• pp.27-32
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• 2012

Transcranial magnetic stimulation requires an electric field composed of dozens of V/m to achieve stimulation. The stimulation system is composed of a stimulation coil to form the electric field by charging and discharging a capacitor in order to save energy, thus requiring high-pressure kV. In particular, it is charged and discharged in capacitor to discharge through stimulation coil within a short period of time (hundreds of seconds) to generate current of numerous kA. A pulse-type magnetic field is formed, and eddy currents within the human body are triggered to achieve stimulation. Numerous pulse forms must be generated to initiate eddy currents for stimulating nerves. This study achieved high internal pressure, a high number of repetitions, and rapid switching of elements, and it implemented numerous control techniques via introduction of the half-bridge parallel load method. In addition it applied a quick, accurate, high-efficiency charge/discharge method for transcranial magnetic stimulation to substitute an inexpensive, readily available, commercial frequency condenser for a previously used, expensive, high-frequency condenser. Furthermore, the pulse repetition rate was altered to control energy density, and grafts compact, one-chip processor with simulation to stably control circuit motion and conduct research on motion and output characteristics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1612-1614
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• 1994

Modulators Installed in PLS(Pohang Light Source) Linac are composed of a DC high voltage section, a charging section and a discharging section. PFN is charged by a resonant charging mechanism, and discharged by a switching device through the primary of the pulse transformer connected to a load. Charged PFN voltage must be well regulated to obtain stable output pulse voltage at the load. For this purpose, DCHV is controlled by a SCR controller with feedback signal, and PFN voltage is regulated by a De-Q'ing circuit. The full power operation test shows the pulse voltage regulation within ${\pm}0.13%$ with SCR feedback control alone, and within ${\pm}0.08%$ together with De-Q'ing. This paper describes the design concept and operational characteristics of the De-Q'ing circuit.