• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.2
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• pp.181-184
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• 2017

This study analyzes the turn-on and turn-off transients of a metal-oxide-semiconductor field-effect transistor (MOSFET) with high-switching frequency systems. In these systems, the voltage distortion becomes serious at the output terminal of a Vienna rectifier by the turn-off delay of the MOSFET. The current has low-order harmonics through this voltage distortion. This paper describes the transient of the turn-off that causes the voltage distortion. The algorithm for reducing the sixth harmonic using a proportional-resonance controller is proposed to improve the current distortion without complex calculation for compensation. The reduction of the current distortion by high-switching frequency is verified by experiment with the 2.5-kW prototype Vienna rectifier.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1205-1208
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• 1995

The optically-gated p-i-n diode switches have been fabricated with gold-compensated silicon. The turn-on and turn-off delay times and the rise and fall times were measured as a function of optical power level, bias, and pulse width. The turn-on characteristics shows a strong dependence an optical pulse power and a delay time(${\delta}{\iota}$) between two pulses, but a weak dependence on the width of optical pulse. Actually there is no turn-off delay in gold-doped p-i-n switches and the fall time is negligible.

• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.69-73
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• 2010

We propose a method to enhance the response time of a twisted nematic liquid crystal (TN-LC) cell using an anisotropic polymer. Polymer networks are formed by the phase separation between a LC and a UV-curable polymer. A TN-LC cell is exposed to UV light after the mixture of LC and anisotropic polymer is injected into the TN-LC cell. As a result, turn-off time of a TN-LC cell can be decreased remarkably without any loss of the transmittance. The turn-off time of a TN-LC cell with pure LC was 16 ms, but those of polymer networked TN-LC cells were 12, 11, and 9 ms when the concentration of the polymer was 3, 5, and 10 wt%, respectively. Moreover, by virtue of the polymer network, the backflow effect and the delay time generated during the turn-off process disappeared.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.22-23
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• 2006

Proton irradiation technology was used for improvement of switching characteristics of the PT-IGBT. Proton irradiation was carried out at 5.56 MeV energy with $1{\times}10^{12}/cm^2$ doze from the back side of the wafer. Characterization of the device was performed by I-V, breakdown voltage, threshold voltage, and turn-off delay time measurement. For irradiated device by 5.56 MeV energy, the breakdown voltage and the threshold voltage were 730 V and 6.5~6.6 V, respectively. The turn-off time has been reduced to 170 ns, which was original $6\;{\mu}s$ for the un-irradiated device.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3334-3341
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• 2023

We studied the irradiation effects of fast neutron generated by a 30 MeV cyclotron on the electrical and switching characteristics of NPT-IGBT devices. Fast neutron fluence ranges from 2.7 × 10⁹ to 1.82 × 10¹³ n/cm². Electrical characteristics of the IGBT device such as I-V, forward voltage drop and additionally switching characteristics of turn-on and -off were measured. As the neutron fluence increased, the device's threshold voltage decreased, the forward voltage drop increased significantly, and the turn-on and turn-off time became faster. In particular, the delay time of turn-on switching was improved by about 35% to a maximum of about 39.68 ns, and that of turn-off switching was also reduced by about 40%-84.89 ns, showing a faster switching.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1073-1077
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• 2006

Proton irradiation technology was used for improvement of switching characteristics of the PT-IGBT. Proton irradiation was carried out at 5.56 MeV energy with $1{\times}10^{12}/cm^2$ doze from the back side of the wafer. The I-V, breakdown voltage, and turn-off delay time of the device were analyzed and compared with those of un-irradiated device and e-beam irradiated device which was conventional method for minority carrier lifetime reduction. For proton irradiated device, the breakdown voltage and the on-state voltage were 733 V and 1.85 V which were originally 749 V and 1.25 V, respectively. The turn-off time has been reduced to 170 ns, which was originally $6{\mu}s$ for the un-irradiated device. The proton irradiated device was superior to e-beam irradiated device for the breakdown voltage and the on-state voltage which were 698 V and 1.95 V, respectively, nevertheless turn-off time of proton irradiated device was reduced to about 60 % compared to that of the e-beam irradiated device.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1547-1549
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• 1996

The electrical and optical switching characteristics of gold-doped silicon p-i-n diodes have been investigated. The device shows a dark switching voltage of about 500 V. The switching voltage decreases rapidly when the illumination level is increased. The differential sensitivity of optical gating over linear region is $d(V_{Th}/V_{Tho})/dP_{Ph}$=0.25/uW. The turn-on delay time and the turn-on rise time decrease with increasing optical pulse power. The turn-off delay and the fall time are negligible.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.3
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• pp.222-230
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• 1998

This paper proposes a new gate drive circuit for high power IGBTs which can reduce the harmful effect of reverse recovery current at turn-on and actively suppress the overvoltage across the driven IGBT at turn-off without a snubber circuit. The turn-on scheme decreases the rising rate of the collector current by inereasing the input capacitance at turn-on transient when the gate-emitter voltage goes above threshold voltage. It results in soft transient of the reverse recovery current with no variation in turn-on delay time. The turn-off driving scheme has adaptive feature to the amplitude of collector current, so that the overvoltage can be limited much effectively at the fault collector current. Experimental results under various normal and fault conditions prove the effectiveness of the proposed circuit.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.10
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• pp.713-718
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• 1987

A new method for the modeling of non-ideal dc-dc converters whose switching times are finite is proposed. The effects of finite turn-on, turn-off times, delay time, storage time, reverse recovery process on the system stability, dc transfer function and efficiency are investigated. It is verified how system poles are changed and how dc transfer function and efficiency are decreased by non-ideal switching.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.257-258
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• 2011

This paper describes a new method for the seamless operation mode transfer of a PCS with minimized voltage disturbance. The proposed method provides reduced STS turn off time after line fault and smooth mode change between current and voltage control of the PCS. The usefulness of the method is verified through simulations with the consideration of the time delay in detecting a line fault and SCR turn-off time.