• Korean Journal of Metals and Materials
• /
• v.48 no.11
• /
• pp.1014-1020
• /
• 2010

In order to improve the purity on deposit in cobalt electrowining, a fundamental study using Pulse-Reverse Current (PRC) was carried out. Based on a sulfate solution, Cu, Ni, and Fe as impurities were added during cobalt electrowinning. There were four reverse waveforms and frequency conditions from 1 Hz to 10 kHz, and the purity of each condition was compared with the Direct Current (DC) purity. From the results, it was found that the anodic potential induced by reverse current affects selective dissolution of impurities. In this work, the case of the highest reverse peak current density ($I_r$) with a short reverse time ($t_r$) at 100 Hz showed a higher purity than that of the DC. This PRC condition also showed only a 4% low current efficiency comparable to the DC. We concluded that an optimized PRC for cobalt electrowinning could improve the purity with little loss of current efficiency.

• Journal of Power Electronics
• /
• v.17 no.5
• /
• pp.1372-1381
• /
• 2017

This paper presents a high-side switch driver IC capable of improving the current sensing accuracy and providing reverse battery protection. Power semiconductor switches used to replace relay switches are encumbered by two disadvantages: they are prone to current sensing errors and they require additional external protection circuits for reverse battery protection. The proposed IC integrates a gate driver and current sensing blocks, thus compensating for these two disadvantages with a single IC. A p-sub-based 90-V $0.13-{\mu}m$ bipolar-CMOS-DMOS (BCD) process is used for the design and fabrication of the proposed IC. The current sensing accuracy (error ${\leq}{\pm}5%$ in the range of 0.1 A-6.5 A) and the reverse battery protection features of the proposed IC were experimentally tested and verified.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.12 no.3
• /
• pp.353-359
• /
• 2012

A highly efficient charge pump that minimizes the reverse charge sharing current (in short, reverse current) is proposed. The charge pump employs auxiliary capacitors and diode-connected MOSFET along with an early clock to drive the charge transfer switches; this new method provides better isolation between stages. As a result, the amount of reverse current is reduced greatly and the clock driver can be designed with reduced transition slope. As a proof of the concept, a 1.1V-to-9.8 V charge pump was designed in a $0.35{\mu}m$ 18 V CMOS technology. The proposed architecture shows 1.6 V ~ 3.5 V higher output voltage compared with the previously reported architecture.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1998.11a
• /
• pp.135-135
• /
• 1998

• Proceedings of the KIPE Conference
• /
• 2018.07a
• /
• pp.189-191
• /
• 2018

This paper introduces a novel ZVS interleaved totem-pole PFC with the reduced circulating current and the reverse recovery current of the diodes. With the help of a simple auxiliary inductor, both ZVS turn-on of the main switches and soft turn-off of the body diodes can be achieved. In the proposed totem-pole PFC topology since the switching losses and the reverse recovery losses can be significantly reduced, the typical Si MOSFETs can be employed. In addition the circulating current is reduced by adjusting the switching frequency. The proposed PFC topology can be a low cost solution to achieve high efficiency in high power PFC applications. The validity and the feasibility of the proposed topology is verified by the experimental results with a 3.3kW interleaved totem-pole PFC converter.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.14 no.4
• /
• pp.495-502
• /
• 2014

Fast recovery diodes (FRDs) were developed using the $p^{{+}{+}}/n^-/n^{{+}{+}}$ epitaxial layers grown by low temperature epitaxy technology. We investigated the effect of electrostatic discharge (ESD) stresses on their electrical and switching properties using current-voltage (I-V) and reverse recovery time analyses. The FRDs presented a high breakdown voltage, >450 V, and a low reverse leakage current, < $10^{-9}$ A. From the temperature dependence of thermal activation energy, the reverse leakage current was dominated by thermal generation-recombination and diffusion, respectively, at low and high temperature regions. By virtue of the abrupt junction and the Pt drive-in for the controlling of carrier lifetime, the soft reverse recovery behavior could be obtained along with a well-controlled reverse recovery time of 21.12 ns. The FRDs exhibited excellent ESD robustness with negligible degradations in the I-V and the reverse recovery characteristics up to ${\pm}5.5$ kV of HBM and ${\pm}3.5$ kV of IEC61000-4-2 shocks. Likewise, transmission line pulse (TLP) analysis reveals that the FRDs can handle the maximum peak pulse current, $I_{pp,max}$, up to 30 A in the forward mode and down to - 24 A in the reverse mode. The robust ESD property can improve the long term reliability of various power applications such as automobile and switching mode power supply.

• Journal of Electrochemical Science and Technology
• /
• v.15 no.3
• /
• pp.405-413
• /
• 2024

Several techniques for determining the reverse peak current from a cyclic voltammogram (CV) for a reversible system are described in the literature: CV itself as a baseline with long switching potential (E_λ) that serves as a baseline for other CVs, Nicholson equation that uses CV parameters to calculation reverse peak current and linear extrapolation of the current obtained at the switching potential. All methods either present experimental difficulties or large errors in the peak current determination. The paper demonstrates, both theoretically and experimentally, that trapezoidal cyclic voltammetry (TCV) can be used as a baseline to determine anodic peak current (i_ap) with high accuracy and with a switching potential shorter than that used by CV, as long as E_λ is at least 130 mV away from the cathodic peak. Beyond this value of switching potential the electroactive specie is completely depleted from the electrode surface. Using TCV with E_λ = 0.34 V and a switching time (t_λ) of 240 s as a baseline, the determination of the reverse peak current presents a deviation from the expected value of less than 1% for most of the CVs studied (except cases when E_λ is close to the direct potential peak). This result presents better accuracy than the Nicholson equation and the linear extrapolation of the current measured at the switching potential, in addition to presenting a smaller error than that obtained in the acquisition of the experimental current. Furthermore, determining the reverse peak current by extrapolating the linear fit of i_ap vs. ${\sqrt[1/]{t_{\lambda}}}$ to infinite time gave a reasonable approximation to the expected value. Experiments with aqueous potassium hexacyanoferrate (II) and ferrocene in acetonitrile confirmed the theoretical predictions.

• Transactions on Electrical and Electronic Materials
• /
• v.15 no.5
• /
• pp.279-283
• /
• 2014

In this paper, we present an economical and practical standard to install a bypass diode in a thin-film PV module. This method helps to reduce heat generation and to prevent module degradation due to excess current from reverse bias. The experimental results confirm that for different numbers of solar cells, there is a relation between the excess reverse current and the degradation of solar cells in a-Si:H modules. The optimal number of solar cells that can be connected per bypass diode could be obtained through an analysis of the results to effectively suppress the degradation and to reduce the heat generated by the module. This technique could be expanded for use in high power crystalline Si PV modules.

• Proceedings of the KIPE Conference
• /
• 2013.07a
• /
• pp.411-412
• /
• 2013

This paper proposes the reverse current control method of synchronous boost converter for fuel cell. In order to implement a high efficiency charger with the synchronous boost converter, using MOSFETs instead of diodes is essential. Using the conventional boosting method, the reverse current is generated during transient state due to the nature of fuel-cell which needs soft starting depending on the amount of hydrogen. By using PWM control method, fuel-cell can be protected from being damaged by reverse current, so synchronous boosting method can be applied to charger applications. The experimental results are shown to verify that the implementation of high-efficiency converter is possible.

• Journal of IKEEE
• /
• v.19 no.1
• /
• pp.94-100
• /
• 2015

In this paper, 50V power U-MOSFET which replace the body(PN) diode with Schottky is proposed. As already known, Schottky diode has the advantage of reduced reverse recovery loss than PN diode. Thus, the power MOSFET with integrated Schottky integrated can minimize the reverse recovery loss. The proposed Schottky body diode U-MOSFET(SU-MOS) shows reduction of reverse recovery loss with the same transfer, output characteristic and breakdown voltage. As a result, 21.09% reduction in peak reverse current, 7.68% reduction in reverse recovery time and 35% improvement in figure of merit(FOM) are observed when the Schottky width is $0.2{\mu}m$ and the Schottky barrier height is 0.8eV compared to conventional U-MOSFET(CU-MOS). The device characteristics are analyzed through the Synopsys Sentaurus TCAD tool.