• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.3
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• pp.112-118
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• 2001

In the near future, the voltage of power system for passenger vehicle will be changed to 42V from existing 14V./ Because of increasing power and voltage ratings used in the vehicle the motor drive system has high switching dv/dt and it generates electromagnetic interference (EMI) To solve these problems multi-level inverter system may be used The feature of multi-level inverter is the output voltage to be synthesized from several levels of voltage Because of this feature high switching dv/dt and EMI can be reduced in the multi-level inverter system But as the number of level is increased manufacturing cost is getting expensive and system size is getting large. Because of these disadvantages the application of multi-level inverter has been restricted only to high power drives. The method to reduce manufacturing cost and system size is to integrate circuit of multi-level inverter into a few chips But isolated power supply and signal isolation circuit using transformer or opto-coupler for drive circuit are obstacles to implement the integrated circuit (IC) In this paper a drive circuit of 4-level inverter suitable for integration to hybrid or one chip is proposed In the proposed drive circuit DC link voltage is used directly as the power source of each gate drive circuit NPN transistors and PNP transistors are used to isolate to transfer the control signals. So the proposed drive circuit needs no transformers and opto-couplers for electrical isolation of drive circuit and is constructed only using components to be implemented on a silicon wafer With th e proposed drive circuit 4- level inverter system will be possible to be implemented through integrated circuit technology Using the proposed drive circuit 4- level inverter system is constructed and the validity and characteristics of the proposed drive circuit are proved through the experiments.

• Journal of IKEEE
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• v.17 no.3
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• pp.324-331
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• 2013

In this paper, we implemented memristor emulator circuit on Printed Circuit Board (PCB) and observed the inherent pinched hysteresis characteristic of memristors by measuring the emulator circuit on PCB. The memristor emulator circuit implemented on PCB is composed of simple discrete devices not using any complicated circuit blocks thus we can integrate the memristor emulator circuits in very small layout area on Silicon substrate. The programmable gain amplifier is designed using the proposed memristor emulator circuit and verified that the amplifier's voltage gain can be controlled by programming memristance of the emulator circuit by circuit simulation. Threshold switching is also realized in the proposed emulator circuit thus memristance can remain unchanged when the input voltage applied to the emulator circuit is lower than VREF. The memristor emulator circuit and the programmable gain amplifier using the proposed circuit can be useful in teaching the device operation, functions, characteristics, and applications of memristors to students when thet cannot access to device and fabrication technologies of real memristors.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.530-536
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• 2000

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.188-190
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• 1995

This paper describes a soft switching using discontinuous inductor current. The soft switching snubber circuit provides ZCS and ZVS for main switch. For high power applications, the input ractifier is fed from a three-phase ac source. The Conventional switching method is hard switching technics, because of the device turn off is ocurred in maximum reactor current. In this time, switching losses are maximised by the hard switching. In generally, soft switching technique has been adjusted with the snubber condenser in order to compensates for this losses. So, it was compared hard switching with soft switching which has proposed in this paper for switching losses, distortion factor by the simulation.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.2
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• pp.63-69
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• 2018

In this paper, the operation principle of a bi-directional switch type resonant AC link snubber circuit was described, together with the practical design procedure, which employs in the proposed power module bridge package type resonant AC link snubber. The novel prototype of power module bridge package type resonant AC link snubber-assisted voltage type sinewave soft switching PWM inverter using IGBT power module was demonstrated herein. It was verified that both the auxiliary power switches in this resonant AC link snubber circuit and the main power switches commutate under the condition of soft switching commutation principle. In addition, the power losses of the new soft switching inverter treated here were analyzed by implementing the experimental data of the IGBT and diode v-i characteristics in addition to switching power loss characteristics into our original computer simulation software developed by the authors. Then, the voltage type sinewave soft switching PWM inverter was high efficiency than that of hard switching PWM inverter, along with performance operation waveforms. In the future, the comparative feasibility study of power module bridge type resonant AC link snubber and its related soft switching inverter in addition to the other types resonant snubber assisted soft switching inverter should be done from a practical point of view.

• Journal of Power Electronics
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• v.7 no.3
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• pp.181-190
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• 2007

This paper presents a novel circuit topology of a DC bus line series switch and parallel snubbing capacitor-assisted soft-switching PWM full-bridge inverter type DC-DC power converter with a high frequency planar transformer link, which is newly developed for high performance arc welding machines in industry. The proposed DC-DC power converter circuit is based upon a voltage source-fed H type full-bridge soft-switching PWM inverter with a high frequency transformer. This DC-DC power converter has a single power semiconductor switching device in series with an input DC low side rail and loss less snubbing capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge arms and DC bus line can achieve ZCS turn-on and ZVS turn-off transition commutation. Consequently, the total switching power losses occurred at turn-off switching transition of these power semiconductor devices; IGBTs can be reduced even in higher switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules can be realized at 60 kHz. It is proved experimentally by power loss analysis that the more the switching frequency increases, the more the proposed DC-DC power converter can achieve a higher control response performance and size miniaturization. The practical and inherent effectiveness of the new DC-DC converter topology proposed here is actually confirmed for low voltage and large current DC-DC power supplies (32V, 300A) for TIG arc welding applications in industry.

• Journal of IKEEE
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• v.18 no.4
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• pp.586-592
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• 2014

In this paper, high efficiency power management IC(PMIC) with DT-CMOS(Dynamic threshold voltage Complementary MOSFET) switching device is presented. PMIC is controlled PWM control method in order to have high power efficiency at high current level. The DT-CMOS switch with low on-resistance is designed to decrease conduction loss. The control parts in Buck converter, that is, PWM control circuit consist of a saw-tooth generator, a band-gap reference(BGR) circuit, an error amplifier, comparator circuit, compensation circuit, and control block. The saw-tooth generator is made to have 1.2MHz oscillation frequency and full range of output swing from supply voltage(3.3V) to ground. 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 current mode PWM control circuits and low on-resistance switching device, achieved the high efficiency nearly 96% at 100mA output current. And Buck converter is designed along LDO in standby mode which fewer than 1mA for high efficiency. Also, this paper proposes two protection circuit in order to ensure the reliability.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1805-1811
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• 2017

Recently, DC systems are considered as efficient electric power systems for renewable energy based clean power generators. This discloses several critical issues that are required to be considered before the installation of the DC systems. First of all, voltage/current switching stress, which is aggravated by large fault current, might damage DC circuit breakers. This problem can be simply solved by applying a superconducting fault current limiter (SFCL) as proposed in this study. It allows a simple use of insulated-gate bipolar transistors (IGBTs) as a DC circuit breaker. To evaluate the proposed resistive type SFCL application to the DC circuit breaker, a DC distribution system is composed of the practical line impedances from the real distribution system in Do-gok area, Korea. Also, to reflect the distributed generation (DG) effects, several DC-to-DC converters are applied. The locations and sizes of the DGs are optimally selected according to the results of previous studies on DG optimization. The performance of the resistive type SFCL applied DC circuit breaker is verified by a time-domain simulation based case study using the power systems computer aided design/electromagnetic transients including DC (PSCAD/ EMTDC(R)).

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.349-352
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• 2003

A personal low-frequency stimulator is a portable device to relax muscle pains of a person. The stimulator generates combined low-frequency pulses to be applied to pads attached to painful muscles. This paper reports a development of such device with its characteristic analyses. The major components of our stimulator are MCU, high-voltage generating circuit part, high-voltage switching circuit part, input switch part and display unit. High-voltage generating circuit is designed by using a boost converter circuit and allows user control of the output voltage. High-voltage switching circuit, controlled by MCU, generates output voltage to be applied to pads. Input switch part is composed of power supply, intensity selection, mode selection and memory. Display unit adopts a text LCD module to display modes, Intensity, output frequency and user set-up time. Our designed safety circuit, to protect human body from possible electric shock, slowly increases the output voltage to the selected output intensity. It continuously checks the output pulse shape and disable the output when dangerous pulses are detected. This paper also shows some experimental results.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.541-543
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• 1997

In this paper, a proposed resonant PWM switching technique makes the boost AC/DC converter to high input power factor and less switching loss. Also, the switching control scheme is used which minimize harmonic components employing novel PWM technique. In addition, an employment of resonant circuit for switching makes zero current switching(ZCS) and zero voltage switching(ZVS) for control switches without switching losses. The result shows that high power factor is still for varying load and switching loss is very low.