Kwang-Hyun Lee

Non-isolated Bidirectional Soft-switching SEPIC / ZETA Converter with Reduced Ripple Currents

A novel non-isolated bidirectional soft-switching SEPIC/ZETA converter with reduced ripple currents is proposed and characterized in this study. Two auxiliary switches and an inductor are added to the original bidirectional SEPIC/ZETA components to form a new direct power delivery path between input and output. The proposed converter can be operated in the forward SEPIC and reverse ZETA modes with reduced ripple currents and increased voltage gains attributed to the optimized selection of duty ratios. All switches in the proposed converter can be operated at zero-current-switching turn-on and/or turn-off through soft current commutation. Therefore, the switching and conduction losses of the proposed converter are considerably reduced compared with those of conventional bidirectional SEPIC/ZETA converters. The operation principles and characteristics of the proposed converter are analyzed in detail and verified by the simulation and experimental results.

Si-based optical I/O for optical memory interface

Optical interconnects may provide solutions to the capacity-bandwidth trade-off of recent memory interface systems. For cost-effective optical memory interfaces, Samsung Electronics has been developing silicon photonics platforms on memory-compatible bulk-Si 300-mm wafers. The waveguide of 0.6 dB/mm propagation loss, vertical grating coupler of 2.7 dB coupling loss, modulator of 10 Gbps speed, and Ge/Si photodiode of 12.5 Gbps bandwidth have been achieved on the bulk-Si platform. 2x6.4 Gbps electrical driver circuits have been also fabricated using a CMOS process.

Recording physics of perpendicular recording with single layered medium and ring head

In this article, the recording physics of a ring head with a single layered perpendicular medium (Ring/SL) is studied and the results are compared with a single pole head with a double layered perpendicular medium (SPT/DL) by using various simulations and experiments. The Ring/SL has much lower effective medium coercivity than the SPT/DL due to the substantial longitudinal field component of ring head and the incoherent rotation mode of medium magnetizations. Furthermore, switching time of the Ring/SL is estimated as only 10%∼30% of the SPT/DL. In the Ring/SL, the head field gradient of 40 Oe/nm is enough for maximizing SNR. The Ring/SL shows very low noise characteristics especially at high linear density. The signal output of the Ring/SL is smaller than the SPT/DL, but it is large enough to be detected. Therefore, it can be concluded that the combination of single layered perpendicular medium and ring head is highly promising for ultrahigh density recording.

48V Power Assist Recuperation System (PARS) with a permanent magnet motor, inverter and DC-DC converter

The present study proposed a novel Power Assist Recuperation System consisted of motor, inverter, DC-DC converter and 48V Li ion battery for fuel saving of conventional Internal Combustion Engine and hybrid vehicles. As a total solution of the next-generation 48V PARS, key components such as Interior Permanent Magnet Synchronous Motor, MOSFET power switching inverter and bi-directional DC-DC converter with cost competitiveness from in-house power ICs and power modules have been optimized based on a 48V Li ion battery. A deep flux weakening control has been evaluated for the IPMSMs high speed operation. The specific value of how much the proposed 48V PARS can reduce CO2 emission and fuel consumption was estimated by so-called Autonomie software using both efficiency maps of motoring and generating modes. It is noticed that the present 48V PARS gives a considerably enhanced performance in reduction of fuel consumption by as high as 17% for a commercial 1.8L engine.

Novel PZT Capacitor Technology for 32Mb and Beyond FRAM Device Using PbTiO 3 Seeding Layer

Effects of the PbTiO 3 (PTO) seeding layer on lowering the PZT crystallization temperature and reducing the capacitor stack height, especially PZT thin film, were systematically investigated. For these purposes, PZT film was modified by using the PTO seeding layer. By using the PTO seeding layer; the crystallization temperature of the PZT film was successfully lowered to 550C. And remanant polarization of PTO-used 100nm thick PZT capacitors measured at 3V was approximately 23 w C/cm 2 , that is 30% higher than that of the PTO-unused PZT capacitors. XRD analysis indicated that the use of the PTO seeding layer remarkably increased the relative intensity of (111) orientation. XRF studies showed that the atomic concentration ratio of Ti-to-Zr was increased by using PTO seeding layers. Necessarily, as the PZT thickness and crystallization temperature are lowered, the thickness of bottom electrode can be reduced as well. Finally, we successfully developed a capacitor stack height of below 400nm, which was composed of Ir/IrO 2 /PZT/Pt/IrO 2 . Furthemore, by lowering the PZT crystallization temperature, small (600 z /contact) and stable contact resistance in a very small size of BC could be obtained.

Novel PZT capacitor technology for high density FRAM device with 0.18 μm D/R

Novel capacitor technologies for high density FRAM device with 0.18 μm D/R (design-rule) have been researched and developed. In order to realize the high-density FRAM device with 0.18 μm D/R, the PZT film was modified by changing Zr/Ti composition and by using PTO seeding layer. Therefore, the crystallization temperature of the PZT film could be successfully lowered to 550°C. The remnant polarization of PTO-used 100 nm thick PZT capacitors measured at 2.7 V was approximately 24 μC/cm 2 , that is 30% higher than that of the PTO-unused PZT capacitors. Necessarily, as the PZT thickness and crystallization temperature are lowered, the thickness of bottom electrode can be reduced as well. Furthermore, by lowering the PZT crystallization temperature and by applying robust TiAlN oxidation barrier, low (300 Ω/contact) and stable contact resistance in a very small size of BC could be obtained. Finally, we successfully developed a capacitor stack height of 270 nm. The capacitor size was 0.26 × 0.44 μm2 and remnant polarization measured at 2.7 V was approximately 11 μC/cm2.

Power Assist Recuperation System (PARS™) for automotive fuel saving and e-boost

A novel Power Assist Recuperation System consisted of motor, inverter, DC-DC converter and 48V Li-ion battery has been presented for fuel saving of conventional Internal Combustion Engine and hybrid vehicles. As a total solution of the next-generation 48V PARS, key components such as Permanent Magnet motor, MOSFET power switching inverter and bi-directional DC-DC converter with cost competitiveness from in-house power ICs and power modules have been optimized based on the 48V battery pack for quick charge and discharge. A deep flux weakening control has been evaluated for the PM motors high speed operation. The specific value of how much the proposed 48V PARS can reduce CO2 emission and fuel consumption was numerically simulated by using both motoring and generating efficiency maps as input data. It is noticed that the present 48V PARS gives a considerably enhanced performance in fuel saving by as high as 17% for a commercial 1.8L gasoline engine during the Urban Dynamometer Driving Schedule mode.