在传统对称式电阻、电容、二极管RCD(resistance capacitance diode)箝位正激变换器基础上,通过引入中间电容和用开关管代替副边的一个二极管,提出了一种具有正反激功能的新型变换器。该变换器在继承传统对称式RCD箝位正-反激变换器的...在传统对称式电阻、电容、二极管RCD(resistance capacitance diode)箝位正激变换器基础上,通过引入中间电容和用开关管代替副边的一个二极管,提出了一种具有正反激功能的新型变换器。该变换器在继承传统对称式RCD箝位正-反激变换器的高效率、占空比可大于0.5和低开关管电压应力优点的同时,进一步拓宽输入电压变化范围和提高输出电压增益。首先分析了变换器工作于激磁电流连续导电模式MCCM(magnetizing current continuous mode)的工作过程,详细分析了MCCM和激磁电流断续导电模式MDCM(magnetizing current discontinuous mode)2种模式下的宽范围和增益特性以及原/副边开关管实现零电压转换ZVS(zero voltage switch)的条件;然后确立了在一定漏电感功率下箝位电阻值与箝位电容电压之间的函数关系曲线,并以此作为选取箝位电阻参考。最后,通过一台实验样机验证了理论分析的正确性。展开更多
The electromigration induced microstructure evolution and damage in asymmetric Cu/Sn-58Bi/Cu solder interconnects were investigated by in-situ SEM observation, focused ion beam （FIB） microanalysis and finite element...The electromigration induced microstructure evolution and damage in asymmetric Cu/Sn-58Bi/Cu solder interconnects were investigated by in-situ SEM observation, focused ion beam （FIB） microanalysis and finite element （FE） simulation. The SEM results show that the electromigration-induced local degradation of microstructures, i.e., segregation of Bi-rich phase and formation of microcracks, in the asymmetric solder interconnects is much severer than that in the symmetrical ones. FIB-SEM microanalysis reveals that the microregional heterogeneity in electrical resistance along different electron flowing paths is the key factor leading to non-uniform current distribution and the resultant electromigration damage. Theoretical analysis and FE simulation results manifest that the current crowding easily occurs at the local part with smaller resistance in an asymmetric solder interconnect. All results indicate that the asymmetric shape of the solder interconnect brings about the difference of the electrical resistance between the different microregions and further results in the severe electromigration damage.展开更多
Two charge qubits being coupled to a damped cavity with different couplings are considered. The dynamical evolution of the entanglement between the two qubits is demonstrated analytically or numerically. It is found t...Two charge qubits being coupled to a damped cavity with different couplings are considered. The dynamical evolution of the entanglement between the two qubits is demonstrated analytically or numerically. It is found that with the cavity dissipation, the steady entanglement between the two qubits can be achieved. The two qubits being initially in the separable and most mixed state can be easily induced to a steady entangled state, and the relative difference of the couplings can be used to enhance the steady entanglement between the two charge qubits.展开更多
文摘在传统对称式电阻、电容、二极管RCD(resistance capacitance diode)箝位正激变换器基础上,通过引入中间电容和用开关管代替副边的一个二极管,提出了一种具有正反激功能的新型变换器。该变换器在继承传统对称式RCD箝位正-反激变换器的高效率、占空比可大于0.5和低开关管电压应力优点的同时,进一步拓宽输入电压变化范围和提高输出电压增益。首先分析了变换器工作于激磁电流连续导电模式MCCM(magnetizing current continuous mode)的工作过程,详细分析了MCCM和激磁电流断续导电模式MDCM(magnetizing current discontinuous mode)2种模式下的宽范围和增益特性以及原/副边开关管实现零电压转换ZVS(zero voltage switch)的条件;然后确立了在一定漏电感功率下箝位电阻值与箝位电容电压之间的函数关系曲线,并以此作为选取箝位电阻参考。最后,通过一台实验样机验证了理论分析的正确性。
基金Project(51275178)supported by the National Natural Science Foundation of ChinaProject(20110172110003)supported by ResearchFund for the Program of Higher Education of China
文摘The electromigration induced microstructure evolution and damage in asymmetric Cu/Sn-58Bi/Cu solder interconnects were investigated by in-situ SEM observation, focused ion beam （FIB） microanalysis and finite element （FE） simulation. The SEM results show that the electromigration-induced local degradation of microstructures, i.e., segregation of Bi-rich phase and formation of microcracks, in the asymmetric solder interconnects is much severer than that in the symmetrical ones. FIB-SEM microanalysis reveals that the microregional heterogeneity in electrical resistance along different electron flowing paths is the key factor leading to non-uniform current distribution and the resultant electromigration damage. Theoretical analysis and FE simulation results manifest that the current crowding easily occurs at the local part with smaller resistance in an asymmetric solder interconnect. All results indicate that the asymmetric shape of the solder interconnect brings about the difference of the electrical resistance between the different microregions and further results in the severe electromigration damage.
基金The project supported by National Natural Science Foundation of China under Grant No. 10374007
文摘Two charge qubits being coupled to a damped cavity with different couplings are considered. The dynamical evolution of the entanglement between the two qubits is demonstrated analytically or numerically. It is found that with the cavity dissipation, the steady entanglement between the two qubits can be achieved. The two qubits being initially in the separable and most mixed state can be easily induced to a steady entangled state, and the relative difference of the couplings can be used to enhance the steady entanglement between the two charge qubits.
