Numerical analysis of short-circuit safe operating area forp-channel and n-channel IGBTs

The mechanisms of destructive failure of an insulated gate bipolar transistor (IGBT) at short-circuit state are discussed. Results from two-dimensional numerical simulation of p-channel and n-channel IGBTs are presented. It is found that there are two types of destructive failure mechanisms: a secondary breakdown and a latchup. Which type is dominant in p-channel and n-channel IGBTs depends on an absolute value of forward voltage |V_CE|. At moderately low |V _CE|, the p-channel IGBT is destroyed by secondary breakdown, and the n-channel IGBT, by latchup. This is due to the difference of a type of flowing carrier crossing a base-collector junction of wide base transistor and ionization rates of electrons and holes     

Physiological role of Ca2+-permeable nonselective cation channel in endothelin-1-induced contraction of rabbit aorta

The alpha-amylase of Streptomyces sp. IMD 2679 was subject to catabolite repression. Four different growth rates were achieved when the organism was grown at 40 degrees C and 55 degrees C in the presence and absence of cobalt, with an inverse relationship between alpha-amylase production and growth rate. Highest alpha-amylase yields (520 units/ml) were obtained at the lowest growth rate (0.062 h-1), at 40 degrees C in the absence of cobalt, while at the highest growth rate (0.35 h-1), at 55 degrees C in the presence of cobalt, alpha-amylase production was decreased to 150 units/ml. As growth rate increased, the rate of specific utilisation of the carbon source maltose also increased, from 46 to 123 micrograms maltose (mg biomass)-1 h-1. The pattern and levels of alpha-glucosidase (the enzyme degrading maltose) detected intracellularly in each case, indicate that growth rate effectively controls the rate of feeding of glucose to the cell, and thus catabolite repression.     

Forward biased safe operating area of emitter switched thyristors

The physical mechanisms for current saturation and destructive failure of the dual channel emitter switched thyristor (EST) are described. Forward Biased Safe Operating Areas (FBSOAs) at short-circuit state of the 600 V and 2500 V dual channel ESTs are reported. It is demonstrated by numerical simulation that the EST offers a better FBSOA than the IGBT. Experimental measurements are reported that corroborate these calculated results     

A new vertical IGBT structure with a monolithic over-current,over-voltage, and over-temperature sensing and protecting circuit

A new 600 V vertical Insulated Gate Bipolar Transistor (IGBT) structure with monolithically integrated over-current, over-voltage, and over-temperature sensing and protecting functions has been developed to exploit an extremely excellent trade-off characteristic between an on-state voltage drop and turn-off time for the first time. This device can be easily made by the conventional IGBT fabrication process. An accurate and a real-time device temperature detection, as well as a high withstand capability against over-current and over-voltage conditions (short circuit immunity of 30 μsec, clamped collector voltage of 640 V), have been achieved. Furthermore, an excellent trade-off characteristic of 1.40 V as an on-state voltage drop and of 0.18 μsec as a fall time is also obtained     

Reverse biased safe operating area of emitter switched thyristors

The reverse biased safe operating area (RBSOA) of 600 V and 2500 V EST devices has been analyzed by numerical simulation for the first time and compared with those for the IGBT and MCT. The dependence of the RBSOA upon the P-base resistance in the main thyristor structure of the EST has also been investigated. Two types of destructive failure mechanisms have been identified: one due to the voltage-induced avalanche multiplication, and the other associated with current-induced latch-up of the parasitic thyristor. It is demonstrated that, although the voltage-induced limit is identical for all three devices, the current induced RBSOA for the EST can be improved over the IGBT and MCT with little sacrifice of the on-state characteristics. In addition, a comparison of the RBSOA with the forward biased safe operating area (FBSOA) has been performed     

Effects of brief glucocorticoid exposure on growth of vascular smooth muscle cells in culture

While prolonged exposure of vascular smooth muscle cells (VSMC) to glucocorticoid has been shown to inhibit cell proliferation, the effect of a brief pulse exposure is not known. We studied the short-term effects of pulse exposure to dexamethasone (DEX) on DNA synthesis in cultured VSMC. VSMC were pulsed with DEx for varying time intervals and [3H]thymidine incorporation into cells after 24 h was measured. Exposure to DEX for 24 h decreased [3H]thymidine incorporation, while pulse treatments with DEX from 2 min to 6 h significantly increased [3H]thymidine incorporation. Maximal proliferative effect was observed with a 20-min exposure. The effect of a 20-min pulse was dose-dependent, with the half-maximal dose of DEX being approximately 10(-7) M. A selective glucocorticoid receptor antagonist, RU486, inhibited the proliferative effect of DEx. Concentrated conditioned medium from cells exposed to 10(-6) M DEX increased [3H]thymidine incorporation by other VSMC in a dose-dependent manner. These results suggest that short-term pulse DEX exposure is capable of producing one or more autocrine growth factors in VSMC via a glucocorticoid receptor action. This effect of glucocorticoid pulses may contribute to the pathogenesis of arteriosclerosis and hypertension.     

Activation of two types of Ca2+-permeable nonselective cation channel by endothelin-1 in A7r5 cells

1. In A7r5 cells loaded with the Ca2+ indicator fura-2, we examined the effect of a Ca2+ channel blocker SK&F 96365 on increases in intracellular free Ca2+ concentrations ([Ca2+]i) and Mn2+ quenching of fura-2 fluorescence by endothelin-1 (ET-1). Whole-cell patch-clamp was also performed. 2. Higher concentrations (> or = 10 nM) of ET-1 (higher [ET-1]) evoked a transient peak and a subsequent sustained elevation in [Ca2+]i: removal of extracellular Ca2+ abolished only the latter. A blocker of L-type voltage-operated Ca2+ channel (VOC) nifedipine at 1 microM reduced the sustained phase to about 50%, which was partially sensitive to SK&F 96365 (30 microM). 3. Lower [ET-1] (< or = 1 nM) evoked only a sustained elevation in [Ca2+]i which depends on extracellular Ca2+. The elevation was partly sensitive to nifedipine but not SK&F 96365. 4. In the presence of 1 microM nifedipine, higher [ET-1] increased the rate of Mn2+ quenching but lower [ET-1] had little effect. 5. In whole-cell recordings, both lower and higher [ET-1] induced inward currents at a holding potential of -60 mV with linear I-V relationships and reversal potentials close to 0 mV. The current at lower [ET-1] was resistant to SK&F 96365 but was abolished by replacement of Ca2+ in the bath solution with Mn2+. The current at higher [ET-1] was abolished by the replacement plus SK&F 96365. 6. In a bath solution containing only Ca2+ as a movable cation, ET-1 evoked currents: the current at lower [ET-1] was sensitive to Mn2+, whereas that at higher [ET-1] was partly sensitive to SK&F 96365. 7. These results indicate that in addition to VOC, ET-1 activates two types of Ca2+-permeable nonselective cation channel depending on its concentrations which differ in terms of sensitivity to SK&F 96365 and permeability to Mn2+.     

1200-V Low-Loss IGBT Module With Low Noise Characteristics and High dIC/dt Controllability

This paper presents the enhanced characteristics of a newly developed low-loss and low-noise 1200-V insulated gate bipolar transistor (IGBT) module. In order to realize low-noise emission, it is necessary not only to improve the reverse recovery characteristics of the free wheeling diode (FWD) but also to reduce the low-current turn-on dI_C/dt of the IGBT. The new IGBTs with high turn-on dI_C /dt controllability and low turn-on power dissipation have been successfully developed by the reduction of Miller capacitance resulting from an optimization of the surface. The 1200-V 450-A IGBT module utilizing the new IGBT and optimized FWD chips has been able to realize 30% reduction of the switching power dissipation when compared to the conventional IGBT module under the operating condition to set the same noise emission level     

ELID precision grinding of large special Schmidt plate for fibre multi-object spectrograph for 8.2 m Subaru telescope

To explore various scientific frontiers from nearby substellar objects to large scale structures of the high redshift universe, a Fibre Multi-Object Spectrograph (FMOS) is being developed as the second generation near-infrared measuring instrument for the prime focus of 8.2 m Subaru telescope in Hawaii, which employs a large special Schmidt plate element. The Schmidt plate consists of a large non-axisymmetric aspherical concave plate and a convex plate. This paper introduces its manufacturing process, focusing on its non-axisymmetric aspherical surface machining by utilizing synthetically ELID grinding and arc-enveloped grinding method. A new grinding system capable of fabricating large optical elements was developed with 10 nm resolution. In this ELID arc-enveloped grinding system, a Cast Iron Fibre Bonded (CIFB) diamond wheel was 3D controlled to scan the workpiece to generate required surface. Grinding characteristics such as attainable form accuracy, surface roughness were investigated. Furthermore, some measures to improve form accuracy were discussed and verified.