根据电感和电容的对偶原理,研究了工作于不连续电容电压模式(discontinuous capacitor voltage mode,DCVM)的单相无桥CukPFC变换器。首先介绍了变换器的稳态分析和DCVM模式实现条件,其次给出了相应参数设计的理论依据,最后采用PSIM仿真...根据电感和电容的对偶原理,研究了工作于不连续电容电压模式(discontinuous capacitor voltage mode,DCVM)的单相无桥CukPFC变换器。首先介绍了变换器的稳态分析和DCVM模式实现条件,其次给出了相应参数设计的理论依据,最后采用PSIM仿真软件验证了电路特性。仿真结果显示工作于DCVM模式的CukPFC变换器具有低开关电流应力,低输入电流总谐波畸变(total harmonic distortion,THD)以及开关管的零电压关断和输出二极管零电压导通的特性。展开更多
Power integrity (PI) has become a limiting factor for the chip's overall performance, and how to place in-package decoupling capacitors to improve a chip's PI performance has become a hot issue. In this paper,...Power integrity (PI) has become a limiting factor for the chip's overall performance, and how to place in-package decoupling capacitors to improve a chip's PI performance has become a hot issue. In this paper, we propose an improved trans- mission matrix method (TMM) for fast decoupling capacitance allocation. An irregular grid partition mechanism is proposed, which helps speed up the impedance computation and complies better with the irregular power/ground (P/G) plane or planes with many vias and decoupling capacitors. Furthermore, we also ameliorate the computation procedure of the impedance matrix whenever decoupling capacitors are inserted or removed at specific ports. With the fast computation of impedance change, in-package decoupling capacitor allocation is done with an efficient change based method in the frequency domain. Experimental results show that our approach can gain about 5× speedup compared with a general TMM, and is efficient in restraining the noise on the P/G plane.展开更多
This paper presents an electric drive system whose motor is connected to a battery by means of a buck DC/DC converter. This motor is further connected to an ultracapacitor by means of a boost DC/DC converter. First, o...This paper presents an electric drive system whose motor is connected to a battery by means of a buck DC/DC converter. This motor is further connected to an ultracapacitor by means of a boost DC/DC converter. First, operation and break processes are studied when the converters are switched off as well as when they are switched on in current limitation mode. Then, a comparative analysis of the results in the two operation modes is done.展开更多
It is well known that a SMPS （switched-mode power supply） is easy to produce strong EMI （electromagnetic interference） and fails in EMC （electromagnetic compatibility） test for its far field radiation exceeds th...It is well known that a SMPS （switched-mode power supply） is easy to produce strong EMI （electromagnetic interference） and fails in EMC （electromagnetic compatibility） test for its far field radiation exceeds the limits between 30-200 MHz. Based on asymmetry line antenna theory, a novel far field CM （common mode） radiation model, including an equivalent driving source, radiation structure and some key influence factors, is identified and built up for a small flyback power supply. Radiation characteristics of this model are predicted by using Ansoft HFSS software and the model effectiveness is verified by experiment. In the end, the radiation role of some key factors, such as the length of output cable, common mode impedance of AC grid, layout of cable and reflected ground, are studied using simulation in detail.展开更多
In the past two decades, the development of certain technologies, in particular Internet and mobile devices （tablet PCs, laptops, mobile telephones, etc.）, has brought about new habits of consuming audiovisual produ...In the past two decades, the development of certain technologies, in particular Internet and mobile devices （tablet PCs, laptops, mobile telephones, etc.）, has brought about new habits of consuming audiovisual products, predominantly among the youngest consumers. A new demand has arisen that has changed the channels of cinematographic exploitation and has allowed the growth of new business initiatives, such as new business models for distributing audiovisual content. The central aim of this paper is to analyse this new business model and to identify the main characteristics of the pioneering company in this sector, Netflix.展开更多
A novel high voltage switching circuit with parallel resonant topology is analyzed.Without adding other resonant components,this circuit makes full use of the transformer leakage inductance and winding capacitance so ...A novel high voltage switching circuit with parallel resonant topology is analyzed.Without adding other resonant components,this circuit makes full use of the transformer leakage inductance and winding capacitance so as to reduce the influence of the transformer parasitic parameter.Using device CD4046 to realize the switching control of MOS,this circuit can realize the constant-current charging to capacitor by operating the above resonance.The operating process of the circuit is analyzed,and the power calculation and some practical waveforms are given.展开更多
A buried-oxide trench-gate bipolar-mode JFET （BTB-JFET） with an oxide layer buried under the gate region to reduce the gate-drain capacitance Cgd is proposed. Simulations with a resistive load circuit for power loss...A buried-oxide trench-gate bipolar-mode JFET （BTB-JFET） with an oxide layer buried under the gate region to reduce the gate-drain capacitance Cgd is proposed. Simulations with a resistive load circuit for power loss comparison at high frequency application are performed with 20V-rated power switching devices,including a BTB-JFET,a trench MOSFET （T-MOSFET） generally applied in present industry, and a conventional trench-gate bipolar-mode JFET （TB-JFET） without buried oxide,for the first time. The simulation results indicate that the switching power loss of the normally-on BTB-JFET is improved by 37% and 14% at 1MHz compared to the T-MOSFET and the normally-on TB-JFET, respectively. In order to demonstrate the validity of the simulation, the normally-on TB-JFET and BTB-JFET have been fabricated successfully for the first time, where the buried oxide structure is realized by thermal oxidation. The experimental results show that the Cgd of the BTB-JFET is decreased by 45% from that of the TB-JFET at zero source-drain bias. Compared to the TB-JFET,the switching time and switching power loss of the BTB-JFET decrease approximately by 7. 4% and 11% at 1MHz,respectively. Therefore,the normally-on BTB-JFET could be pointing to a new direction for the R＆D of low volt- age and high frequency switching devices.展开更多
To understand the operation principle of the modular multilevel converter(MMC)deeply,it is necessary to study the harmonic characteristics of the MMC theoretically.Besides,the analytical harmonic formulas of the MMC a...To understand the operation principle of the modular multilevel converter(MMC)deeply,it is necessary to study the harmonic characteristics of the MMC theoretically.Besides,the analytical harmonic formulas of the MMC are useful in designing the main circuit,reducing the losses and improving the waveform quality.Based on the average switching function and the Fourier series harmonic analysis,this paper deduces the analytical expressions for such electrical quantities as the arm voltage,the arm current,the capacitor voltage,the capacitor current and the circulating current of the MMC.Finally,a digital model of a 21-level MMC-HVDC system is realized in PSCAD/EMTDC.The results of the analytical expressions coincide with the simulation results,which verify the effectiveness and feasibility of the proposed analytical expressions.展开更多
A single-mask dry-release process for fabrication of high aspect ratio SOI MEMS devices is presented,which takes advantage of the lag effect in silicon DRIE(deep reactive ion etching).The wide trenches and the releasi...A single-mask dry-release process for fabrication of high aspect ratio SOI MEMS devices is presented,which takes advantage of the lag effect in silicon DRIE(deep reactive ion etching).The wide trenches and the releasing holes are etched to the buried oxide in the first-step DRIE whereas the narrow trenches are still connected due to the lag effect.After the buried oxide is removed by wet etching through the opened releasing holes and wide trenches,the narrow trenches are etched through by the second-step DRIE.Not only can the sticking problems be avoided,but also the footing effect during the DRIE can be partially suppressed.The feasibility of the proposed technique was verified by implementing a capacitive accelerometer.The scale factor and the non-linearity of the fabricated accelerometer were measured to be 63.4 mV/g and 0.1% with the measurement range of ±1 g,respectively.展开更多
基金the Ph.D Programs Foundation of Ministry of Education of China (No. 20060335065)the Natural Science Foundation of Zhejiang Province, China (No. Y106513)
文摘Power integrity (PI) has become a limiting factor for the chip's overall performance, and how to place in-package decoupling capacitors to improve a chip's PI performance has become a hot issue. In this paper, we propose an improved trans- mission matrix method (TMM) for fast decoupling capacitance allocation. An irregular grid partition mechanism is proposed, which helps speed up the impedance computation and complies better with the irregular power/ground (P/G) plane or planes with many vias and decoupling capacitors. Furthermore, we also ameliorate the computation procedure of the impedance matrix whenever decoupling capacitors are inserted or removed at specific ports. With the fast computation of impedance change, in-package decoupling capacitor allocation is done with an efficient change based method in the frequency domain. Experimental results show that our approach can gain about 5× speedup compared with a general TMM, and is efficient in restraining the noise on the P/G plane.
文摘This paper presents an electric drive system whose motor is connected to a battery by means of a buck DC/DC converter. This motor is further connected to an ultracapacitor by means of a boost DC/DC converter. First, operation and break processes are studied when the converters are switched off as well as when they are switched on in current limitation mode. Then, a comparative analysis of the results in the two operation modes is done.
文摘It is well known that a SMPS （switched-mode power supply） is easy to produce strong EMI （electromagnetic interference） and fails in EMC （electromagnetic compatibility） test for its far field radiation exceeds the limits between 30-200 MHz. Based on asymmetry line antenna theory, a novel far field CM （common mode） radiation model, including an equivalent driving source, radiation structure and some key influence factors, is identified and built up for a small flyback power supply. Radiation characteristics of this model are predicted by using Ansoft HFSS software and the model effectiveness is verified by experiment. In the end, the radiation role of some key factors, such as the length of output cable, common mode impedance of AC grid, layout of cable and reflected ground, are studied using simulation in detail.
文摘In the past two decades, the development of certain technologies, in particular Internet and mobile devices （tablet PCs, laptops, mobile telephones, etc.）, has brought about new habits of consuming audiovisual products, predominantly among the youngest consumers. A new demand has arisen that has changed the channels of cinematographic exploitation and has allowed the growth of new business initiatives, such as new business models for distributing audiovisual content. The central aim of this paper is to analyse this new business model and to identify the main characteristics of the pioneering company in this sector, Netflix.
文摘A novel high voltage switching circuit with parallel resonant topology is analyzed.Without adding other resonant components,this circuit makes full use of the transformer leakage inductance and winding capacitance so as to reduce the influence of the transformer parasitic parameter.Using device CD4046 to realize the switching control of MOS,this circuit can realize the constant-current charging to capacitor by operating the above resonance.The operating process of the circuit is analyzed,and the power calculation and some practical waveforms are given.
文摘A buried-oxide trench-gate bipolar-mode JFET （BTB-JFET） with an oxide layer buried under the gate region to reduce the gate-drain capacitance Cgd is proposed. Simulations with a resistive load circuit for power loss comparison at high frequency application are performed with 20V-rated power switching devices,including a BTB-JFET,a trench MOSFET （T-MOSFET） generally applied in present industry, and a conventional trench-gate bipolar-mode JFET （TB-JFET） without buried oxide,for the first time. The simulation results indicate that the switching power loss of the normally-on BTB-JFET is improved by 37% and 14% at 1MHz compared to the T-MOSFET and the normally-on TB-JFET, respectively. In order to demonstrate the validity of the simulation, the normally-on TB-JFET and BTB-JFET have been fabricated successfully for the first time, where the buried oxide structure is realized by thermal oxidation. The experimental results show that the Cgd of the BTB-JFET is decreased by 45% from that of the TB-JFET at zero source-drain bias. Compared to the TB-JFET,the switching time and switching power loss of the BTB-JFET decrease approximately by 7. 4% and 11% at 1MHz,respectively. Therefore,the normally-on BTB-JFET could be pointing to a new direction for the R＆D of low volt- age and high frequency switching devices.
基金supported by the National High Technology Research and Development Program of China("863" Project)(Grant No.2012AA050205)
文摘To understand the operation principle of the modular multilevel converter(MMC)deeply,it is necessary to study the harmonic characteristics of the MMC theoretically.Besides,the analytical harmonic formulas of the MMC are useful in designing the main circuit,reducing the losses and improving the waveform quality.Based on the average switching function and the Fourier series harmonic analysis,this paper deduces the analytical expressions for such electrical quantities as the arm voltage,the arm current,the capacitor voltage,the capacitor current and the circulating current of the MMC.Finally,a digital model of a 21-level MMC-HVDC system is realized in PSCAD/EMTDC.The results of the analytical expressions coincide with the simulation results,which verify the effectiveness and feasibility of the proposed analytical expressions.
基金supported by the National Natural Science Foundation of China (Grant No. 90923037)
文摘A single-mask dry-release process for fabrication of high aspect ratio SOI MEMS devices is presented,which takes advantage of the lag effect in silicon DRIE(deep reactive ion etching).The wide trenches and the releasing holes are etched to the buried oxide in the first-step DRIE whereas the narrow trenches are still connected due to the lag effect.After the buried oxide is removed by wet etching through the opened releasing holes and wide trenches,the narrow trenches are etched through by the second-step DRIE.Not only can the sticking problems be avoided,but also the footing effect during the DRIE can be partially suppressed.The feasibility of the proposed technique was verified by implementing a capacitive accelerometer.The scale factor and the non-linearity of the fabricated accelerometer were measured to be 63.4 mV/g and 0.1% with the measurement range of ±1 g,respectively.
