Control of the switching transients of IGBT series strings byhigh-performance drive units

In the field of power electronics, the use of series-connected insulated gate devices, such as insulated gate bipolar transistors or power MOSFETs, is interesting in order to obtain fast and efficient power switches in medium-range power converters. In this kind of application, the control of the voltage sharing across the series strings of devices is an important aspect to be considered. The proposed technique allows obtaining safe commutations of the switches by simple and effective control circuits acting on the gate side of the power devices. In particular, the gate drive units are arranged in order to ensure good performance during the switching transients, while preventing overvoltage peaks on the devices. Both the design criteria and analysis of the control circuit are developed. Several experimental tests are reported in order to demonstrate the validity and correctness of the proposed approach     

Snubberless voltage sharing of series-connected insulated-gatedevices by a novel gate control strategy

Insulated gate devices, such as metal oxide semiconductor field effect transistors (MOSFETs) or insulated gate bipolar transistors (IGBTs), are increasingly used in high-voltage power converters where a request for fast power switches is growing. Series connection of devices is a viable approach to manage voltages higher than the blocking voltage of the single device. The main problem in such an application is to guarantee the voltage balance across the devices both in steady-state and during switching transients. In this paper, a novel approach is presented, which is used to equalize the voltage sharing during the switching transients. The main advantages of the proposed method consist in avoiding the traditional use of the snubber capacitors, in the output power side, and in working on the gate side. The application of the proposed gate drive technique is firstly discussed and compared with different solutions, hence, validated by experimental tests applied to the control of series connected devices. Finally, a comparison is performed between the transient behaviors of two different configurations: a single switch with high-voltage blocking capability, and in alternative a series of two devices which together ensure the voltage blocking capability of the single switch. The better performances of the latter configuration, working with the proposed control circuit, over the former have been experimentally demonstrated     

The endoscopic treatment of postoperative stenoses of the upper digestive tract

The authors compare their experience in dilatation of postoperative benign esophageal strictures. A total of 60 patients (37 males, 23 females: mean age 52), all with severe dysphagia, from January 1985 to September 1995, underwent endoscopic dilatation: 32 of these with Savary dilators and 28 with balloon dilators. Dilatation was effective in 93% in both groups. Two severe complications were recorded (1 heart attack and 1 perforation) in the group that underwent endoscopic dilatation with Savary dilators. During endoscopic management, pain recurred in 43% and 87% of cases after balloon or Savary dilatations, respectively. The authors believe balloon dilators are more effective, better tolerated and with less complications than Savary dilators. They reserve the management with Savary dilators to the extremely severe esophageal strictures.     

在标准STripFET中集成肖特基二极管以提高数据通信和计算机应用中同步buck转换器的效率

本文采用了先进的strip工艺并在同一块芯片上集成了肖特基二极管的低压功率MOSFETs的工作特性进行了研究。这种新型的MOSFET——肖特基二极管结构可提高应用于移动通信设备中同步buck转换器的效率和可靠性。文中对相关创新的主要技术问题及其优点进行了探讨。并且，为了显示在MOSFET上耦合肖特基二极管对工作特性的显著改进，还对电压调制模块（VRM）的实际工作状态进行了测试。通过与带标准MOSFET的常用的VRM单片电路器件进行比较，可以更显出DC—DC转换器效率的提高效果。文中同时还作了热特性对比。