• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.106-109
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• 2003

With the variation of Ag concentration in bath, current density, additive and agitation for electroplating of Sn-Ag solder, the compositions and the morphologies of solder were studied. It was possible to control Ag content in Sn-Ag solder by varying Ag concentration in bath and current density The microstructure size of Sn-Ag solder decreased with increasing current density. Duty cycle of pulse electroplating and quantity of additive affected on Ag content of deposit and surface roughness. In this work eutectic Sn-Ag solder bumps with fine pitch of 30m and height of 15m was formed successfully. The Ag content of electrodeposited solder was confirmed by EDS and WDS analyses and the surface morphologies was analyzed by SEM and 3D surface analyzer.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.528-532
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• 1987

Closed-loop fiber-optic gyroscope with linear scale factor for a wide dynamic range is demonstrated using a gating process and two-harmonic phase modulation, of which the second harmonic is obtained by a frequency doubler. Also the effects of the second harmonic and duty cycle of gating signal on the linearity of scale factor are estimated theoretically and compared with the measured data. The experimental results show the best linearity of scale factor is about 0.5% within the rotation rate 90.deg./sec. The closed-loop fiber-optic gyroscope with gated two-harmonic phase modulation can be used in the application demanding less sensitive performance and modest scale factor linearity.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.83-86
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• 2002

This paper presents an implementation of Pill controller for DC-DC converter using the microcontroller. The features of the microcontroller such as the on chip ADC and Pulse width Modulator (PWM) eliminate the external components needed to perform these functions. The duty rate cycle for the DC-DC converter can be updated every time when the (ADC) conversation and the calculation time are finished. The stable response can be obtained for any kind of DC-DC converters. The SMPS controller looks at the converter output, compares the output to a set point, performs a control algorithm (Pill algorithm) and finally applies the algorithm output to the PWM. PWM output is then used to drive the DC-DC converter. Figure (1) shows a simplified block diagram of a complete DC-DC converter system.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.101-101
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• 2000

MSC(Multispectral Camera), which will be a unique payload on KOMPSAT-II, is designed to collect panchromatic and multi-spectral imagery with a ground sample distance of 1m and a swath width of 15km at 685km altitude in sun-synchronous orbit. The instrument is designed to have an orbit operation duty cycle of 20% over the mission life time of 3 years. MSC electronics consists of three main subsystems; PMU(Payload Management Unit), CEU(Camera Electronics Unit) and PDTS(Payload Data Transmission Subsystem). PMU performs all the interface between spacecraft and MSC, and manages all the other subsystems by sending commands to them and receiving telemetry from them with software protocol through RS-422 interface. CEU controls FPA(Focal Plane Assembly) which contains TDI(Timc Delay Integration) CCD(Charge Coupled Device) and its clock drivers. PMU provides a Master Clock to synchronize panchromatic and multispectral camera. PDTS performs compression, storage and encryption of image data and transmits them to the ground station through x-band.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1146-1148
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• 2007

This paper proposes a method to improve the charging speed and discharging performance of a high voltage capacitor used in a portable medical device. The improvement of the charging speed was achieved by duty cycle control. The discharging performance was carried out by varying the phase duration and the leading edge voltage of the output according to the transthoracic impdedance of the patient. As a result, the improvement in the charging speed and the performance of the discharging parameters shorten the patient treatment time.

• Journal of Power Electronics
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• v.7 no.2
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• pp.124-131
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• 2007

In this paper, a novel type of auxiliary switched capacitor assisted edge resonant soft switching PWM resonant DC-DC converter with two simple auxiliary commutation lossless inductor snubbers is presented. The operation principle of this converter is described using the switching mode equivalent circuits. This newly developed multi resonant DC-DC converter can regulate its DC output AC power under a principle of constant frequency edge-resonant soft switching commutation by an asymmetrical PWM duty cycle control scheme. The high frequency power regulation and actual power characteristics of the proposed soft switching PWM resonant DC-DC converter are evaluated and discussed. The operating performances of the newly proposed soft switching inverter are represented based on simulation results from an applications point of view.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.168-170
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• 1998

In this paper a driving method using the microcomputer in safe driving the axial type double rotor brushless DC motor without shaft position sensor is studied. The rotor position is determined from the back-EMF passed though special filter. Starting technique which uses the motor as a synchronous motor at standstill are explained. The motor speed is controlled by changing the duty cycle of PWM. The test motor has Y-connected three-phase stator and 8-pole axial type double rotor. From the experiments, we got good performences of the proposed control system.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.34-36
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• 2008

This paper is given a full detail of mathematical analyses of input current for novel active type power factor correction(PFC) AC-DC converter of step up-down added electric isolation. These are compared with harmonics components of input current for a conventional PFC converter of electric isolation type. The proposed PFC converter is constructed in using a new loss-less snubber circuit to achieve a soft switching of control device. Also the proposed converter for discontinuous conduction mode(DCM) eliminates the complicated circuit control requirement and reduces the size of components. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, input power factor is nearly unity and the control method is simple. Particularly, the stored energy of loss-less snubber capacitor is recovered with input side and increases input current from resonant operation. The result is that input power factor of the proposed converter is higher than that of a conventional PFC converter. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1636-1647
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• 1997

As most of today's automatic transmissions in passenger car adopt a electro-hydraulic control system, the role of electronically controlled solenoid valves occupies an important position and it is essential to predict solenoid transient characteristics in order to design and evaluate the performance of the hydraulic control system. However, in general, both the magnetic and electrical parameters f the solenoid system are hardly known and it is not easy to model this section with moderate complexity although mechanical system could be developed using the classical second order system. This paper presents a dynamic modelling technique of a solenoid valve, that is controlled by pulse width modulation for an automatic transmission, in terms of system identification theory. In nonlinear computer simulation, it is shown that the identified systems which produce magnetic force to input duty cycle for various excitation signals predict the static and dynamic performance very well near the operating point and in experiment conducted to confirm the validity of identification theory for PWM solenoid valve, we find that there is a good agreement between the experimental data and simulation result. Hence, this model can be utilized in the development of pressure control system with PWM solenoid valve.

• Physical Therapy Korea
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• v.14 no.2
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• pp.76-84
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• 2007

This study was designed to determine the efficacy of ultrasound and laser therapy for sub-acute lower back pain. Twenty-seven patients with sub-acute low back pain were recruited, who were randomly assigned to three groups: Ultrasound group (actual ultrasound, 1.1 MHz, $1.0W/cm^2$, duty cycle 100%, 10 min/session, n=9), laser group (actual laser, 904 nm, 155 ns, 13.5 W, 12 mW, 90 sec/point, n=9), and control group (placebo ultrasound or placebo laser, n=9). All of treatments including placebo procedures were applied to patients over a period of 2 weeks, five times a week. Visual Analogue Scale (VAS), Modified Schober's Test (MST), and Modified Oswestry Disability Questionnaire (MODQ) were used by the clinical and functional evaluations before and after intervention. At post-hoc, significant differences were observed in all groups with respect to VAS, MST (p<.05), except MODQ. VAS and MST score were more significantly improved in the ultrasound group than the laser and control group (p<.0167). However, no significant difference was present between the laser group and the control group. Therefore, this study revealed that ultrasound therapy was effective in pain relief and improvement of lumbar mobility in patients with sub-acute lower back pain. However, laser therapy did not show the effects for sub-acute lower back pain.