Breakdown voltage

About: Breakdown voltage is a research topic. Over the lifetime, 18395 publications have been published within this topic receiving 213377 citations.

Thermal cautery system

Abstract: A thermal cautery system having an endoscopically deliverable probe connected to a power supply and display unit. The power supply and display unit, when triggered by a footswitch, energizes a voltage regulator having a current limited output that supplies power to the probe. The current limiting function of the voltage regulator is disabled for a predetermined period that power is initially applied to said probe to minimize the heating time of said probe. The current through said probe is sensed and used to increase the voltage at the output of the voltage regulator as the current increases to compensate for the voltage drop in the conductors connecting the probe to the power supply. A manually selected portion of the sensed current through the probe is also integrated and used to terminate the flow of current through the probe when the integral of the current with respect to time has reached a predetermined value. A tone generator provides an audible indication when power is being applied to the probe and for a predetermined period thereafter to allow the probe to cool before the absence of the tone signals the removal of the probe from tissue being coagulated. The probe is heated by current flowing through an internal diode having a predetermined breakdown voltage at a predetermined temperature. The temperature of the probe is self-regulated by applying a voltage to the probe that is substantially equal to said predetermined voltage so that the current through the probe is reduced at said predetermined temperature.

Semiconductor power devices with alternating conductivity type high-voltage breakdown regions

Abstract: A semiconductor power device wherein the reverse voltage across the p + -regions(s) and the n + -regions(s) is sustained by a composite buffer layer, shortly as CB-layer. The CB-layer contains two kinds of semiconductor regions with opposite types of conduction. These two kinds of regions are alternatively arranged, viewed from any cross-section parallel to the interface between the layer itself and the n + (or p + )-region. Whereas the hitherto-used voltage sustaining layer contains only one kind of semiconductor with single type of conduction in the same sectional view. Design guidelines are also provided in this invention. The relation between the on-resistance in unit area Ron and the breakdown voltage V B of the CB-layer invented is Ron ocV B 113 which represents a breakthrough to the conventional voltage sustaining layer, whereas the other performances of the power devices remain almost unchanged.

Recessed-gate structure approach toward normally off high-Voltage AlGaN/GaN HEMT for power electronics applications

Abstract: A recessed-gate structure has been studied with a view to realizing normally off operation of high-voltage AlGaN/GaN high-electron mobility transistors (HEMTs) for power electronics applications. The recessed-gate structure is very attractive for realizing normally off high-voltage AlGaN/GaN HEMTs because the gate threshold voltage can be controlled by the etching depth of the recess without significant increase in on-resistance characteristics. With this structure the threshold voltage can be increased with the reduction of two-dimensional electron gas (2DEG) density only under the gate electrode without reduction of 2DEG density in the other channel regions such as the channel between drain and gate. The threshold-voltage increase was experimentally demonstrated. The threshold voltage of fabricated recessed-gate device increased to -0.14 V while the threshold voltage without the recessed-gate structure was about -4 V. The specific on-resistance of the device was maintained as low as 4 m/spl Omega//spl middot/cm/sup 2/ and the breakdown voltage was 435 V. The on-resistance and the breakdown voltage tradeoff characteristics were the same as those of normally on devices. From the viewpoint of device design, the on-resistance for the normally off device was modeled using the relationship between the AlGaN layer thickness under the gate electrode and the 2DEG density. It is found that the MIS gate structure and the recess etching without the offset region between recess edge and gate electrode will further improve the on-resistance. The simulation results show the possibility of the on-resistance below 1 m/spl Omega//spl middot/cm/sup 2/ for normally off AlGaN/GaN HEMTs operating at several hundred volts with threshold voltage up to +1 V.

Surface flashover of insulators

Abstract: The author reviews surface flashover (i.e. voltage breakdown along the surface of insulators), primarily in vacuum. He discusses theories and models relating to surface flashover and pertinent experimental results. Surface flashover of insulators in vacuum generally is initiated by the emission of electrons from the cathode triple junction (the region where the electrode, insulator, and vacuum meet). These electrons usually then multiply as they traverse the insulator surface, either as a surface secondary-electron-emission avalanche or as an electron cascade in a thin surface layer, causing desorption of gas which had been adsorbed on the insulator surface. This desorbed gas is then ionized, which leads to surface flashover of the insulator. The theory and modeling of this phenomena and experimental studies of surface charging, the applied voltage waveform, prestressing, conditioning, discharge delay and speed, insulator geometry AMD material, surface treatment, surface gases, temperature, and pressure are reviewed. Some suggestions are made regarding how to choose the material geometry and processing when selecting an insulator for a particular application. >

GaN Power Transistors on Si Substrates for Switching Applications

Abstract: In this paper, GaN power transistors on Si substrates for power switching application are reported. GaN heterojunction field-effect transistor (HFET) structure on Si is an important configuration in order to realize a low loss and high power devices as well as one of the cost-effective solutions. Current collapse phenomena are discussed for GaN-HFETs on Si substrate, resulting in suppression of the current collapse due to using the conducting Si substrate. Furthermore, attempts for normally off GaN-FETs were examined. A hybrid metal-oxide-semiconductor HFET structure is a promising candidate for obtaining devices with a lower on-resistance (Ron) and a high breakdown voltage (Vb).