LDMOS开关在不同频率下的热安全工作

研究了LDMOS器件内部的最高温度与开关频率之间的关系.结果表明:在较高频率工作时,器件内部的最高温度与器件的热容、功耗、占空比和连续工作时间有关,而与器件的热阻和信号周期无关,器件会一直处于升温状态;在较低频率工作时,器件内部的最高温度还与器件的热阻和周期有关.所得结果可作为功率器件在各种频率下工作时热安全工作的参考.     

LDMOS在正常开关工作下的瞬态热效应

利用热等效电路对外加连续脉冲产生的热效应中晶格温度的上升及下降作了研究并与实验进行了比较.结果表明,若高频脉冲的延迟时间大于降温驰豫时间,则器件处于热安全工作区.对热阻为3.5K/W,热容为5μs·W/K的LDMOS,如脉冲频率小于7.14kHz且占空比为0.5,或脉冲频率为10kHz且占空比小于0.3,则该器件工作在热安全区.文中还给出了功率器件热安全工作区的判据.     

掺杂KTP的一维光子晶体光开关的理论研究

设计了掺杂KTP的一维光子晶体光开关器件,利用传输矩阵理论对于掺杂KTP的一维光子晶体的传输特性进行了研究.数值计算表明,对于中心波长的光波,随温度升高,器件透射蜂向长波方向移动,结果显示温度变化对于透射率的影响不足以隔断光波.当在KTP两端施加直流电场时,当电压大于特定值时,光器件透射率降到开关阈值之下,形成光开关.当在KTP两端施加交流电场时,输出光波的周期正好是交流电场周期的一半,可以通过调节电场的频率来得到想要的频率的脉冲信号.     

温度对压接型IGBT器件内部接触热阻的影响

温度是功率半导体器件备受关注的问题,不仅直接影响功率半导体器件的电气性能,而且还间接影响功率半导体器件的热学和机械特性.压接型IGBT器件内部是电磁场、温度场和结构场的多物理量耦合场,器件内部各组件间的接触热阻是温度场与结构场双向耦合的重要桥梁,也是器件可靠性的重要影响因素.通过单芯片子模组有限元模型分析了各组件间的接触热阻,重点研究了温度对接触热阻的影响,计算了热阻测量前后的接触热阻值,并进行了对比.鉴于目前接触热阻测量方法的局限性,通过测量单个快恢复二极管(FRD)芯片子模组结到壳热阻值与温度的变化关系间接得到接触热阻与温度的关系,并对有限元计算结果进行了验证.     

关于半导体器件热特性表征和控制技术的研究

根据对器件散热特性的分析,提出用特定脉宽的瞬态热阻抗表征器件的稳态散热特性.测量了特定器件热阻与温度的依赖关系,建议在实际工作中注意器件热阻并不为常数的客观事实.提出应力试验前后测量器件热阻可有效控制器件的某些制造缺陷.     

高性能振荡器加快仿真时间

脉冲宽度调制器(PWM)电路通常使用一个内部锯齿波电路,在大多数时间内专用于产生开关周期。这些周期的宽度取决于误差信号的强度。在大多数PWM控制器的SPICE仿真中,一个简单的PULSE语句通常足以产生一个固定的频率模式。但是,现代的控制器使PULSE关键词在下述情况下难以实现:* 不能停止PULSE发生器:在一些电路中,内部跳越周期或短路时的锁定功能可以阻止控制器产生开关脉冲。从本质上说,振荡器通常不能提供最低电流消耗。有了PULSE关键词,便可以停止提供脉冲(如通过一个与门),但时钟发生器将继续工作,通过减少时间步长大大增加…     

半导体功率发光二极管温升和热阻的测量及研究

通过电学测量方法得到了半导体功率发光二极管温升与热阻的加热响应曲线.曲线出现一个或多个台阶,反映了其内部的热阻构成与器件物理结构.同时采用遮光法对器件温升及热阻进行了修正.还应用瞬态加热响应原理对功率管的封装结构进行了监测.     

半导体功率发光二极管温升和热阻的测量及研究

通过电学测量方法得到了半导体功率发光二极管温升与热阻的加热响应曲线.曲线出现一个或多个台阶,反映了其内部的热阻构成与器件物理结构.同时采用遮光法对器件温升及热阻进行了修正.还应用瞬态加热响应原理对功率管的封装结构进行了监测.     

器件热阻随测试结温变化规律研究

为探究半导体分立器件电学法热阻测试时器件结温与热阻的变化规律,开展了基于热阻测试实验分析。详细介绍了热阻测试程序和典型热阻测试电路,并对4款典型VDMOS器件开展热阻测试,结合器件结构特性、热响应曲线和微观导热理论中声子导热系数与温度关系,研究获得器件热阻与结温的变化规律。通过热阻与结温的正相关性规律,有效提升器件在老炼和实际工况下结温计算的准确性。     

时钟频率达1GHz的高速直接数字合成器

近年来直接数字合成器(DDS)在高速化和多功能化方面又有了长足的进步。出现了时钟频率达GHz的DDS器件。本文介绍的美国模拟器件公司生产的AD9858的时钟频率最高可达1GHz，可直接形成0～400MHz的正弦波。可工作于单频模式和扫频模式，频率切换速度仅为83ns。若预先将有关数据存储在存储器中，可以将切换时间缩短至8ns,DDS通常作为产生正弦波的信号源使用。     

A family of closed-form duty cycle control laws for three-phaseboost AC/DC converter

In this paper, a basic closed-form duty cycle control law is first derived for the proposed AC/DC converter to achieve clean sinusoidal input current, adjustable DC voltage, controllable power factor and bidirectional power flow capability, and fixed switching frequency, without using any current sensor. Then, a second dead-band scheme is derived from the previous basic form to achieve the same function and to reduce switching loss and thermal stress. Similarly, a four-switch scheme is also derived to provide a new operation mode to enhance the reliability of the converter. Modified control laws of the above family are also considered to handle the effect of unbalanced input voltage. It is very interesting to see that a unified theory can be used to give the above family of duty cycle control laws under both balanced and unbalanced input voltage. Some simulation and experimental results are presented for verification     

Improved small-signal analysis for the phase-shifted PWM power converter

A closed form cycle by cycle analysis forms the basis for a new zero-voltage switching (ZVS) phase-shifted PWM (PSPWM) full bridge power converter small-signal model. The paper derives the small-signal response equations. The PSPWM converter has an implicit "slew interval," making the converter dynamics difficult to analyze using traditional averaging techniques. The converter control to output transfer function under continuous conduction mode operation and using voltage-mode control does not exhibit a second order pole associated with the output L-C filter, making it different from a conventional PWM converter. This new PSPWM converter model shows that the output L-C filter is separated into two real poles, with one pole held at constant frequency independent of operating conditions. A characteristic pole depends only upon the converter switching frequency and inductor values. This characteristic pole is fundamental to understanding the PSPWM converter natural and forced responses. The new small-signal model is shown to be in excellent agreement with experimental results.     

Strategy for enhancing reliability and lifetime of DC-AC inverters used for wind turbines

Lifetime of wind turbine inverters is below expectations therefore, novel design and drive strategies are timely required to achieve optimum life span.In this work, a novel driving strategy to mitigate stresses on inverters is proposed. First, an electro thermal analysis was carried out using finite element modelling methods. Subsequently, the outcomes of the models were validated using DC/AC IGBT based power inverter module interfaced to 1.1 kW electrical outputs of a horizontal wind turbine operated under different wind speeds. Real time data was collected using both dSPACE system and high speed thermal imaging camera. The proposed driving method is based on adjusting the switching frequency according to wind speed. Edge detection scheme was embedded in Simulink to determine temperature fluctuations caused by variations in wind speed profile. Effects of these fluctuations are mitigated by regulating the switching frequency and power losses based on a look up table and interpolation method. The proposed strategy of operation reduces cyclic temperature depended lifetime span (total lifetime consumption) to 1.45 × 10⁻⁵ cycles compared to 1.88 × 10⁻⁵ when operated under conventional fixed frequency. Wire-bond thermal stress was also reduced from 54.5 MPa, for the fixed switching frequency, to 45.5 MPa. This represents about 21% reduction in total lifetime consumption of inverter's wire-bond which, brings huge benefits to wind energy industry.     

Avalanche behavior of power MOSFETs under different temperature conditions

The ability of high-voltage power MOSFETs to withstand avalanche events under different temperature conditions are studied by experiment and two-dimensional device simulation.The experiment is performed to investigate dynamic avalanche failure behavior of the domestic power MOSFETs which can occur at the rated maximum operation temperature range(-55 to 150℃).An advanced ISE TCAD two-dimensional mixed mode simulator with thermodynamic non-isothermal model is used to analyze the avalanche failure mechanism.The unclamped inductive switching measurement and simulation results show that the parasitic components and thermal effect inside the device will lead to the deterioration of the avalanche reliability of power MOSFETs with increasing temperature.The main failure mechanism is related to the parasitic bipolar transistor activity during the occurrence of the avalanche behavior.     

Fundamental limitations in RF switching and phase shifting using semiconductor diodes

When semiconductor diodes are used as variable impedance switching elements in RF transmission networks, the maximum power and minimum attenuation depend upon the characteristics of the diodes and the function being performed. Equations and theorems are derived which define these limits for quantized RF control networks used in on-off switches, selection switches, and phase-shift devices. The relationships are quite general and the limits are shown to apply to a wide variety of network configurations. It is shown that the maximum power of a switch is proportional to the maximum RF current of the forward-biased diode and also to the maximum RF voltage when reverse-biased. The maximum power in phase shifters is a sinusoidal function of the phase change required. Minimum attenuation depends upon the switching function performed, the frequency of operation, and a newly defined cutoff frequency which includes diode resistance in both forward-bias and reverse-bias states.     

CFAVC scheme for high frequency series resonant inverter-fed domestic induction heating system

This article presents the investigations on the constant frequency asymmetric voltage cancellation control in the AC–AC resonant converter-fed domestic induction heating system. Conventional fixed frequency control techniques used in the high frequency converters lead to non-zero voltage switching operation and reduced output power. The proposed control technique produces higher output power than the conventional fixed-frequency control strategies. In this control technique, zero-voltage-switching operation is maintained during different duty cycle operation for reduction in the switching losses. Complete analysis of the induction heating power supply system with asymmetric voltage cancellation control is discussed in this article. Simulation and experimental study on constant frequency asymmetric voltage cancellation (CFAVC)-controlled full bridge series resonant inverter is performed. Time domain simulation results for the open and closed loop of the system are obtained using MATLAB simulation tool. The simulation results prove the control of voltage and power in a wide range. PID controller-based closed loop control system achieves the voltage regulation of the proposed system for the step change in load. Hardware implementation of the system under CFAVC control is done using the embedded controller. The simulation and experimental results validate the performance of the CFAVC control technique for series resonant-based induction cooking system.     

Contributions to the analysis of deterministic noise on ADPLL jitter performance

In this paper an analytical method is presented for estimating the cycle jitter of ADPLL due to power supply noise with deterministic frequency. It leads to the conclusion that jitter heavily depends on the noise frequency and the smallest cycle jitter appears at only integer multiples of oscillation frequency. It also reveals that the relationship between the bandwidth of ADPLL and the DCOs noise-suppression varies depending on the noise frequency. Our method is utilized to study a CMOS ADPLL designed and simulated in SMIC 0.13 μm standard CMOS process. A comparison between the results obtained by our method and those obtained by Hsim simulation proves the accuracy of the predicted model. The measured RMS jitters caused by the switching noise arising from other digital blocks sharing the same power/ground rails on the testing PCB shows that different switching frequency has totally different effect on ADPLL jitter. It sheds some light on the design of power supply network for ADPLL in the practical application.     

不同脉冲工作条件对GaN HEMT器件结温的影响

研究了不同脉冲工作条件对GaN高电子迁移率晶体管(HEMT)结温的影响,通过改变脉冲信号发生器的输出频率和占空比来改变器件的工作条件,利用具备高空间分辨率的显微红外热像仪进行瞬态结温测试。结果表明:器件工作在给定的平均功率下,可以通过提高脉冲信号占空比和频率来改善器件的寿命和性能可靠性;工作在给定的峰值功率下,可以通过降低脉冲占空比和提高脉冲频率来改善器件的寿命和性能可靠性。沟道温度影响着半导体器件的寿命,因此,可以在器件能够承受的范围内通过改变脉冲占空比和脉冲频率来改善器件的寿命和性能可靠性。     

Steady-state analysis and design of a buck zero-current-switchingresonant DC/DC converter

An analytic basis is provided for a buck high-efficiency high-frequency zero-current-switching resonant DC/DC power converter. The current and voltage waveforms are derived for the steady-state operation. Design equations are then introduced for the switch duty cycle, maximum switching frequency, DC transfer function, peak currents and voltages, output power, and power conversion capability. Finally, the design procedure is presented along with the advantages and disadvantages of the converter, which are discussed in detail     

The effect of electro-thermal parameters on IGBT junction temperature with the aging of module

This paper presents the effect of the change of electro-thermal parameters on IGBT junction temperature with module aging. Five IGBT modules are subjected to advance power thermal cycling, and IGBT I–V characterization, switching loss, and transient thermal impedance curve are measured every 1000 power thermal cycles. Then, electro-thermal models of IGBT module under power thermal cycles were built by change electro-thermal parameters, and the influence of various parameters of the electro-thermal model on the junction temperature was researched respectively. Experimental results demonstrate that IGBT collector-emitter voltage, switching loss and thermal resistance increase more quickly with the aging process of module. Simulation results indicate that the variations of electro-thermal parameters have crucial influences on the IGBT junction temperature. After 6000 power thermal cycles, the IGBT steady state junction temperature mean and variation are increased 1.97 K and 0.1656 K over its initial value, respectively. The relative temperature rise is 38.10% and relative temperature variation is 15.08% after 6000 power thermal cycles. The rise in switching loss increases both the steady state junction temperature mean and variation. The change of thermal impedance has great influence on the steady state junction temperature mean, but has little effect on steady state junction temperature variation.