• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.15 no.1
• /
• pp.13-21
• /
• 2001

The discharge characteristics of 3 electrcdes AC surface discharge plasma display were analyzed. For an unstable state of the discharge which appeared at the maximum discharge voltage, it is found that a parbal erase of the wall charge by the second discharge is a cause. Based on the second discharge, new operation margin considering the interrelation between the address discharge and the display discharge was defined and the validity of it was verified by the experiments. It is necessary to decrease the acklress pulse width for high-speed addressing. However, the operation margin of the ackIress pulse decreases as the pulse width of it becomes narrower. If the address pulse width is wider than l[ps], the operation margin of the display discharge is not related to the address pulse width. From the experimental result, image or 8bit 253 gray level was displayed on PDP with the cell structure of the HDTV class by using the high-speed address ADS drive methcd with pulse width of $1[{\mu}s]$ and the brightness of $560[cd/m^2]$ was obtained. ained.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.5
• /
• pp.389-396
• /
• 2003

This paper describes a novel ac/dc power converter suitable for frequent output short-circuit faults. The output dc power of the proposed converter can be disconnected from the load within several hundred microseconds at the instant of short-circuit fault. The rising time of the dc load voltage is as small as several hundred microseconds, and there Is no overshoot of the dc voltage because the dc output fillet capacitors stay at a undischarged state. The proposed converter has the characteristics of a simplified structure, reduced cost, weight, and volume compared to the conventional power supplies for frequent output short-circuit. Analysis, simulations, and experiments are carried out to investigate the operation and usefulness of the proposed scheme.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.8
• /
• pp.102-108
• /
• 2005

In this paper, authors propose novel boost AC-DC converter of high power factor and analyze for waveform and harmonics component of input current. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of at input voltage under the constant duty cycle switching. Therefore, input power factor is nearly unity. 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 conventional converter of high power factor. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.4
• /
• pp.161-165
• /
• 2005

Need of a dimmer function becomes more important with increasing interest on a HDTV for home theater applications. In a conventional AC PDP, a possible method to reduce luminance of a whole Panel is to reduce a total number of sustain pulses and then to change the gray level. However, the reduction of the total sustain number causes the step of luminance to be rough. Moreover, it is impossible to control the luminance of the panel for a given gray level. In this paper, a simple and robust method is proposed to control linearly the luminance of whole panel by applying the asymmetric sustain pulses in the display period of the ADS driving scheme. As the range of luminance control by the proposed method is about $50\%$ for a given gray level. Moreover, it is experimentally verified that the proposed method shows similar dynamic margin performances compare with the conventional method.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.51 no.11
• /
• pp.541-545
• /
• 2002

This paper proposes the new narrow erase method to erase wall charges formed in an AC plasma display panel (PDP) cell. In the proposed method, pulse timing of switch at the sustain period is adjusted for inducing, a weak discharge. Then, after the narrow erase, the voltage of the X electrode is set to differ from that of the Y electrode. For the proposed method, the measured maximum address voltage margin was 38.3V at Y_Rest voltage of 100V and sustain voltage of 180${\sim}$185V. However, for the conventional method, in which the X and Y electrodes are set to be of equal voltage after the narrow erase, the measured maximum address voltage margin was 31.3V at Y_Rest voltage of 150V and sustain voltage of 180V. This result shows that the measured maximum voltage margin for the proposed method is about 7V(22%) higher than that for the conventional method.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.4 no.5
• /
• pp.462-473
• /
• 1999

This paper addresses the current measurement issue of all digital field oriented control of ac motors. The p paper focuses on the effect of low-pass filter and also on the sampling of the fundamental component of the m motor current. The low-pass filter, which suppresses the switching noise of the motor current, introduces v variable phase delay according to the current ripple frequency. It is shown that the current sampling error c consists of the fundamental component and high frL'quency ripple components. In this paper, the dependency of t this current sampling e$\pi$or on the reference voltage vector is investigated analytically and a sampling technique i is proposed to minimize the error. The work is based on the three phase symmetry pulse width modulation l inverter driving an induction machine. With this technique, the bandwidth of current regulator can be extended t to the limit given by the switching frequency of the inverter and more precise torque regulation is possible.

• Journal of Welding and Joining
• /
• v.23 no.1
• /
• pp.69-76
• /
• 2005

Recently, application of arc welding to galvanized carbon steel sheet is on the increasing Ould in the fields of automobile and construction industries. In arc welding process, zinc is evaporated in weld pool, even under the appropriate welding condition and produce blowhole and/or pit. Zinc gas cause instability of arc and increase spatter and fume. This research is purposed to minimize the heat-input and the formation of porosities in the welded joint of the galvanized carbon steel sheet using variable polarity AC wave pulse MIG welding system. An appropriate welding condition which showed low spatter and good bead appearance was acquired by applying the AC pulse MIG welding machine to DC duplicated MIG welding with the solid wire. When oxygen gas was added to shield gas of MIG welding for galvanized steel sheet, arc length was increased and arc stability was improved. In the AC duplicated welding, the loss of galvanized layer was decreased as the amount of heat-input was decreased when the EN ratio was increased under the condition that average welding current was evenly set.

• Journal of the Korean Society of Safety
• /
• v.24 no.6
• /
• pp.50-54
• /
• 2009

Ionizer is used for improving manufacturing process and reducing inferior goods in the clean room. As a general rule, neutralization of the electrostatic charge is most important to make TFT-LCD, PDP and OLED. Pulse AC-static eliminator with output voltage of about 10.5kV has been used these days as neutralization device. But this device has a problem with lower performance which was caused by particles-adhesion on the electrode when it has been used for a long time. So we studied to solve the problem with lower performance using high Frequency(72kHz) static eliminator which was produced by Piezo transformer device, and compared Pulse-AC type with Piezo-electronic device such as decay time and ion balance for 10 weeks periods. As a result of this study, we found that Piezo transformer device has been maintained normal condition for 10 weeks. Also, we made the rule by this study, normally Piezo transformer device has to clean the electrode during every 11th weeks.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.44 no.2
• /
• pp.13-18
• /
• 2007

This paper presents the experimental findings on the different degradation mechanism which depends on the gate oxide thickness in lateral DMOS transistors. For thin oxide devices, the generation of interface states in the channel region and the trapped holes in the drift region is found to be the causes of the device degradation. For thick devices, the generation of interface states in the channel region is found to be the causes of the device degradation. We confirmed the different degradation mechanism using device simulation. From the comparison of device degradation under DC and AC stress, it is found that the device degradation is more significant under DC stress than one under AC stress. The device degradation under AC stress is more significant in high frequency. Therefore the hot carrier induced degradation should be more carefully considered in the design of RF LDMOS transistors and circuit design.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.7
• /
• pp.916-922
• /
• 2014

Diode rectifiers have been widely used for an AC to DC converter. But a big problem is that they include large harmonics components in the input currents. A 12-pulse configuration with phase shifting transformer is useful for reducing them. however, it still includes the ($12{\pm}1$)th (m; integer) harmonics in the input currents. In this paper, we propose a single-phase square wave auxiliary voltage supply which is inserted in the middle DC bus. It reduces harmonics especially the 11th and 13th and the harmonic characteristic becomes almost equivalent to a 24-pulse rectifier. Theoretical analysis of the combined 12-pulse diode rectifier with the auxiliary supply is presented and a control method of the auxiliary supply is proposed. The reduction in the input current harmonics is verified by simulation using software PSIM.