• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2529-2533
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• 1999

This paper proposes a modified hysteresis current control method based on space vector modulation. The proposed method differs from former works in that it uses effective voltage vectors instead of zero vectors while not significantly increasing the circuit complexity. The circuit uses outer band that is slightly wider than the usual current limit band (inner band) to detect the phase of current command and thereby the region information. The comparator output signals associated with the inner and outer band are used to determine the proper voltage vector that minimizes the current error and number of switching, with simple logic circuitry. The utilization of effective voltage vector is of particular importance when the ac-side emf is relatively large. Both the simulation and experiment show that the proposed method is more effective than the conventional one that uses zero vectors, in reducing the number of switching over a range of ac-side emf variation.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.310-312
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• 1989

From the viewpoint of an effective energy use, many method for reactive power compensation has been developed. Among of the reactive power compensation, this paper describes the relation of operation interpretation, filter, hysteresis width and switching time of current controlled PWM converter which has excellent reactive power compensation. This current controlled PWM convertor is excellent the view of reactive power compensation by current control method using hysteresis comparator method, but is required element of high response characteristics. Therefore this paper offers the series of data for system considering switching characteristics of switching element.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.335-337
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• 1993

Offset voltage and drift characteristics of operational amplifier are critical factor to precision AID conversion System. In this study, a method is suggested to design the programmable A/D conversion system which has high resolution and low drift characteristics. First, hardware was designed to reduce the offset voltage of integrator and comparator, and analog switches are connected to reduce the drift characteristics of operational amplifier. And then, a calibration software technique was performed to obtain the stable data from A/D converter. The main advantage of our method is high precision A/D converter can be constructed with low cost and high confidence. Therefore proposed method is expected to be used in the industrial field where a high precision measurement is required.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.450-452
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• 1993

In this study, a method is suggested to design the A/D conversion system which has high resolution to convert load cell signal. First, hardware was designed to reduce the offset voltage of integrator and comparator. And then, a calibration software technique was performed to obtain the stable data from A/D converter. The optimal parameters of each elements in the circuits was selected using the SPICE simulation. The main advantage of our method is high precision A/D converter can be constructed with low cost and high confidence. Therefore proposed method is expected to be used in the industrial field where a high precision measurement is required.

• Analytical Science and Technology
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• v.18 no.6
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• pp.520-528
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• 2005

Two biological Certified Reference Materials (CRMs), KRISS 108-04-001 (oyster tissue) and 108-05-001 (water dropwort stem), were prepared by Korea Research Institute of Standards and Science (KRISS)during FY '01. The certified values of these materials had been determined by Isotope Dilution Mass Spectrometry (IDMS) for six elements (Cd, Cr, Cu, Fe, Pb and Zn). Additional analytical works are now progressing to certify the concentrations of a number of the environmental and nutrimental elements in these CRMs. The certified values in a CRM are usually determined by using a single primary method with confirmation by other method(s) or using two independent critically-evaluated methods. Instrumental Neutron Activation Analysis (INAA) plays an important role in the determination of certified values as it can eliminate the possibility of common error sources resulting from sample dissolution. In this study INAA procedure was used in determination of 23 elements in these two biological CRMs to acquire the concentration information and the results were compared with KRISS certified values.

• Journal of IKEEE
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• v.12 no.3
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• pp.176-183
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• 2008

The high efficiency power management IC(PMIC) with DTMOS(Dynamic Threshold voltage MOSFET) switching device is proposed in this paper. PMIC is controlled with PWM control method in order to have high power efficiency at high current level. DTMOS with low on-resistance is designed to decrease conduction loss. The control parts in Buck converter, that is, PWM control circuits consist of a saw-tooth generator, a band-gap reference circuit, an error amplifier and a comparator circuit as a block. The Saw-tooth generator is made to have 1.2 MHz oscillation frequency and full range of output swing from ground to supply voltage(VDD:3.3V). The comparator is designed with two stage OP amplifier. And the error amplifier has 70dB DC gain and $64^{\circ}$ phase margin. DC-DC converter, based on Voltage-mode PWM control circuits and low on-resistance switching device, achieved the high efficiency near 95% at 100mA output current. And DC-DC converter is designed with LDO in stand-by mode which fewer than 1mA for high efficiency.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1367-1371
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• 2004

In this paper, we propose a method and condition of locating the position of an object in one dimension by using the phase difference of arrival(PDOA), To get a phase difference, the comparator of a wayside radio station(WRS) compares the reference signal with the received signal, Therefore, we can locate the position of a moving object. Finally, by using the simulation of a computer we analyze their values.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.9
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• pp.915-919
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• 2007

This paper proposed a transponder detection method to reduce recognition time in RFID system. It's also shown that conventional procedure of communication in the system could cause a waste of time when a reader recognizes a transponder. The reduction of recognition time can be obtained by developing a circuit to detect a transponder actively. Detecting a transponder is achieved by using the voltage variation of reader antenna voltage that happens when a transponder approaches to the vicinity of magnetic field formed by the reader. By adding a comparator to the antenna receiver of a reader, the reader can perceive approach or existence of a transponder. A reader for experiment is made using the MFRC500 by Phillips that supports ISO/IEC 14443 protocol. Comparing the proposed method with the conventional methods by experiment, there are 47.5ms reduction of recognition time maximally and 12ms in average.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.9
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• pp.107-116
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• 1996

In the stochastic structure for doing exact calculationk, an input number must be changed to a pulse stream. Because the performance of random number generator (RNG) is controlled by its initial condition, we suggested newly modified cellular automata (MCA) which is uses a counter for boundary condition. We compared newly suggested MCA RNG to previously reported RNGs using the AND gate passing outputs which have the same meaning of multiplication in the stochastic calculation. In order to use stochastic we studied about the method, one large RNG can generate many small random numbers. In this method, RNG must have large drive capabilities for many input comparator. So we studied about drive capabilities using BiCMOS circuit and CMOS circit by SPICE.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.968-971
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• 1993

Fuzzy inference system which inferences and processes the Fuzzy information is designed using digital voltage mode neural circuits. The digital fuzzification circuit is designed to MIN,MAX circuit using CMOS neural comparator. A new defuzzification method which uses the center of area of the resultant fuzzy set as a defuzzified output is suggested. The method of the center of area(C. O. A) search for a crisp value which is correspond to a half of the area enclosed with inferenced membership function. The center of area defuzzification circuit is proposed. It is a simple circuit without divider and multiflier. The proposed circuits are verified by implementing with conventional digital chips.