共查询到20条相似文献,搜索用时 171 毫秒
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Wonseok Kang 《今日电子》2012,(8):36-37
LED照明应用中的开关电源在输入级越来越多地采用有源功率因数校正(PFC)设计,以期满足国际谐波规范要求。非连续导通模式(DCM)中的升压拓扑是功率额定值小于300W转换器的最适合PFC方法。在这种拓扑中,升压开关的开通功率损耗可以忽略,而主要的功率损耗是关断损耗和导通损耗。在引入了超级结器件之后,超级结器件通常被看作一种针对有源PFC而优化的开关,因为它们具有极低的导通阻抗和 相似文献
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六阶带通非对称扬声器系统研究 总被引:2,自引:2,他引:0
本文给出六阶带通扬声器系统的响应函数,在此基础上详细讨论了系统的特性(包括频率、相位、群延迟和脉冲特性),并与四阶带通扬声器系统的特性作了比较。最后描述了泄漏声阻对系统特性的影响且给出系统有损耗响应函数。 相似文献
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如今很多大尺寸平板电视、高清电视,以及高端PC和入门级服务器的电源功率都超过300W,而以前具有高效率和低成本的BCMFPC转换器的最大功率约为300W。传统的临界导通模式(BCM)PFC控制器采用可变的开关频率,将电磁辐射分散到整个开关频率范围内,从而减小了EMI。MOSFET是零电流导通,不会在整流二极管上产生反向恢复损耗,所需的电感器较小,在检流电阻上的损耗也更少。 相似文献
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运用无桥式整流电路实现高效率的PFC设计 总被引:3,自引:0,他引:3
RonBrownMarcoSoldano 《电子设计应用》2005,(6):124-125
引言 近来,不使用桥式电路的功率因数校正(PFC)电路成为人们注意的焦点。设计人员去掉了转换器输入端的常规桥式整流电路,可以减少开关损耗,进一步提高效率。在这样的电路中,不存在由于导通损耗而降低效率的问题,且设计比较简单,需要的元件数量较少。 相似文献
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Morisette D.T. Cooper J.A. Jr. Melloch M.R. Dolny G.M. Shenoy P.M. Zafrani M. Gladish J. 《Electron Devices, IEEE Transactions on》2001,48(2):349-352
The static and dynamic characteristics of large-area, high-voltage 4H-SiC Schottky barrier diodes are presented. With a breakdown voltage greater than 1200 V and a forward current in excess of 6 A at 2 V forward bias, these devices enable for the first time the evaluation of SiC Schottky diodes in practical switching circuits. These diodes were inserted into standard test circuits and compared to commercially available silicon devices, the results of which are reported here. Substituting SiC Schottky diodes in place of comparably rated silicon PIN diodes reduced the switching losses by a factor of four, and virtually eliminated the reverse recovery transient. These results are even more dramatic at elevated temperatures. While the switching loss in silicon diodes increases dramatically with temperature, the SiC devices remain essentially unchanged. The data presented here clearly demonstrates the distinct advantages offered by SiC Schottky rectifiers, and their emerging potential to replace silicon PIN diodes in power switching applications 相似文献
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We have presented a comparative account of the high frequency prospective as well as noise behaviors of wide-bandgap 4H-SiC and 6H-SiC based on different structures of IMPATT diodes at sub-millimeter-wave frequencies up to 2.18 THz. The computer simulation study establishes the feasibility of the SiC based IMPATT diode as a high power density terahertz source. The most significant feature lies in the noise behavior of the SiC IMPATT diodes. It is noticed that the 6H-SiC DDR diode shows the least noise measure of 26.1 dB as compared to that of other structures. Further, it is noticed that the noise measure of the SiC IMPATT diode is less at a higher operating frequency compared to that at a lower operating frequency. 相似文献
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Trew R.J. Yan J.-B. Mock P.M. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1991,79(5):598-620
The potential of SiC and diamond for producing microwave and millimeter-wave electronic devices is reviewed. It is shown that both of these materials possess characteristics that may permit RF electronic devices with performance similar to or greater than what is available from devices fabricated from the commonly used semiconductors, Si, GaAs, and InP. Theoretical calculations of the RF performance potential of several candidate high-frequency device structures are presented: the metal semiconductor field-effect transistor (MESFET), the impact avalanche transit-time (IMPATT) diode, and the bipolar junction transistor (BJT). Diamond MESFETs are capable of producing over 200 W of X -band power as compared to about 8 W for GaAs MESFETs. Devices fabricated from SiC should perform between these limits. Diamond and SiC IMPATT diodes also are capable of producing improved RF power compared to Si, GaAs, and InP devices at microwave frequencies. RF performance degrades with frequency and only marginal improvements are indicated at millimeter-wave frequencies. Bipolar transistors fabricated from wide bandgap material probably offer improved RF performance only at UHF and low microwave frequencies 相似文献
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Hann-Ping Hwang Yung-Shih Cheng Jia-Lin Shieh Jen-Inn Chyi 《Electron Devices, IEEE Transactions on》2001,48(2):185-189
A series of Si-based thin films, including amorphous Si, SiC, as well as the conventional SiOx and SiNx, was investigated in terms of the electrical characteristics of GaAs/Al0.3Ga0.7As heterostructure diodes and heterojunction bipolar transistors (HBTs). All the films were found effective in reducing the leakage current and long term degradation. Less size-dependence of the current gain was found for the HBTs passivated by amorphous Si and SiC. In addition, the devices passivated by amorphous Si and SiC films exhibited better performance during high power operation. This is attributed to the high thermal conductivity of these two materials 相似文献
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Silicon carbide high-power devices 总被引:2,自引:0,他引:2
Weitzel C.E. Palmour J.W. Carter C.H. Jr. Moore K. Nordquist K.K. Allen S. Thero C. Bhatnagar M. 《Electron Devices, IEEE Transactions on》1996,43(10):1732-1741
In recent years, silicon carbide has received increased attention because of its potential for high-power devices. The unique material properties of SiC, high electric breakdown field, high saturated electron drift velocity, and high thermal conductivity are what give this material its tremendous potential in the power device arena. 4H-SiC Schottky barrier diodes (1400 V) with forward current densities over 700 A/cm2 at 2 V have been demonstrated. Packaged SITs have produced 57 W of output power at 500 MHz, SiC UMOSFETs (1200 V) are projected to have 15 times the current density of Si IGBTs (1200 V). Submicron gate length 4H-SiC MESFETs have achieved fmax=32 GHz, fT=14.0 GHz, and power density=2.8 W/mm @ 1.8 GHz. The performances of a wide variety of SiC devices are compared to that of similar Si and GaAs devices and to theoretically expected results 相似文献
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Spiazzi G. Buso S. Citron M. Corradin M. Pierobon R. 《Power Electronics, IEEE Transactions on》2003,18(6):1249-1253
The performance of a 600 V, 4 A silicon carbide (SiC) Schottky diode (Infineon SDP04S60) is experimentally evaluated. A 300 W boost power factor corrector (PFC) with average current mode control is considered as a key application. Measurements of overall efficiency, switch and diode losses, and conducted electromagnetic interference (EMI) are performed both with the SiC diode and with two ultra-fast, soft-recovery, silicon power diodes, namely the RURD460 and the presented STTH5R06D. The paper compares the results to quantify the impact of the recovery current reduction provided by SiC diode on these key aspects of the converter behavior. Based on the experimental results, the paper shows that the use of SiC diodes in PFC designs may only be justified in high switching frequency applications. 相似文献
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《Microwave Theory and Techniques》1978,26(12):1029-1035
The tunnel-injection-transit-time (TUNNETT) diode is operated at a high frequency and has a low-noise level compared to the IMPATT diode. The tunnel injection in a thin carrier generating region of the TUNNETT depends strongly on the electric-field intensity over 1000 kV/cm where the ionization of carriers can be neglected, leading to a higher efficiency performance than that of the IMPATT. GaAs TUNNETT diodes with p+-n and p+-n-n+ structures have been fabricated by a new LPE method (the temperature-difference method under controlled vapor pressure). The fundamental oscillation at frequencies from about 100 up to 248 GHz has been obtained from the pulse-driven p+-n-n+ diodes. This paper describes the details of the oscillation characteristics of GaAs TUNNETT diodes. 相似文献