Precision average-sensing AC/DC converters

Various configurations of average-sensing AC/DC converters for precision AC voltage measurements are described. Due to the unique electrical configurations in which the influence of the inaccuracy of ratio resistors is suppressed, these converters have high accuracy (better than 0.01%) and resolution (0.0001%) at medium frequencies. Their frequency range is from 10 Hz to 1 MHz, with a settling time less than 1 s     

Analysis of thyristor DC chopper power converters including nonlinear commutating reactors

Dc chopper power converters are used to control the power supplied to a dc load from a dc source. In a battery-powered vehicle, for example, a dc chopper can control the dc series traction motor. Thyristors are favored for the switching element in high power applications. The particular circuit described here can be used as a voltage step-down converter or a voltage step-up converter and uses two auxiliary thyristors to turn off the main power thyristor. The behavior of the step-up circuit is described by exactly the same equations as the step-down circuit when the input voltage is replaced by the load voltage and the load current is replaced by the input current. The analysis treats the general case where saturating reactors are used to soften the commutation of current in the power semiconductors. The nonlinear characteristics of these reactors are approximated by two linear segments when molybdenum-Permalloy powder cores are used. Linear or square-loop cores are included by the theory as special cases. A design synthesis based on the analytical equations is best performed with the aid of a computer.     

An optimized method for computer-aided DC measurements of power MOStransistors

An intelligent data acquisition system for the characterization of power NMOS transistors has been developed. The system uses a pulsed method with adaptive duty cycle. The temperature is empirically determined by using the transistor under test as a thermometer. An accurate database can be obtained for modeling or parameter-extraction purposes. Rules for the rejection of anomalous data due to thermal or electrical transitions have been included in the software. A criterion based on the first and second derivatives has shown that the acquired database quality is better when these rules are used. This criterion is independent of the model considered and the parameter-extraction algorithm used     

Acceleration of transients in a microcalorimeter for microwave power converters

It is shown that additional heating accelerates the calibration of a microwave power converter in a microcalorimeter. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 55–57, September, 2007.     

EMC of power converters: the self-compatibility approach

Analysis of the internal electromagnetic compatibility of digitally controlled power converters is discussed. In particular, the optimum layout of the circuit configuration is designed on the basis of the actual electromagnetic interference between the power and the control section of a power converter. Besides, further improvements can be achieved by means of an auto- tuning additional board, which scans all the possible converter switching frequencies and analyses the distortion on the control signals corresponding to each frequency. Its main task is to select only the ones which produce low disturbances on the control signals as operating frequencies for the converter.     

Fast and reliable top-level simulation strategy for mixed-signal integrated circuits and its application to DC?DC converters

Top-level, transient, transistor-based simulations are a critical step in the product-development cycle of mixed-signal integrated circuits. These simulations are normally performed just before fabrication and unfortunately impose cumbersome bottlenecks in the design flow. Verification is an iterative process by nature, whereby each problem found requires another simulation to ensure a proper fix is in place, and because of the complexity of a large system, minor errors can cost days, increasing design time and time-to-market. A top-level transistor-based simulation strategy is proposed with minimal time overhead. The strategy is to start with a quick, all macro-model system simulation and gradually substitute one transistor-level sub-block at a time for each additional run. For optimal results, less computationally intensive blocks, which can be determined from a proposed set of screening simulations, are replaced first. The proposed strategy was tested and applied to a buck, current-mode switching regulator, and the results show that simulation overhead is least for linear analogue functions (e.g. op-amps) and worst for high-speed nonlinear circuits (e.g. signal generators). Nonlinear and bi-stable analogue blocks such as bandgap references take more time to simulate than op-amps and less than low frequency digital functions such as power-on-reset, which in turn are less intensive than ramp and pulse generators     

Auxiliary subsystems of a General-Purpose IGBT Stack for high-performance laboratory power converters

A PWM converter is the prime component in many power electronic applications such as static UPS, electric motor drives, power quality conditioners and renewable-energy-based power generation systems. While there are a number of computer simulation tools available today for studying power electronic systems, the value added by the experience of building a power converter and controlling it to function as desired is unparalleled. A student, in the process, not only understands power electronic concepts better, but also gains insights into other essential engineering aspects of auxiliary subsystems such as start-up, sensing, protection, circuit layout design, mechanical arrangement and system integration. Higher levels of protection features are critical for the converters used in a laboratory environment, as advanced protection schemes could prevent unanticipated failures occurring during the course of research. This paper presents a laboratory-built General-Purpose IGBT Stack (GPIS), which facilitates students to practically realize different power converter topologies. Essential subsystems for a complete power converter system is presented covering details of semiconductor device driving, sensing circuit, protection mechanism, system start-up, relaying and critical PCB layout design, followed by a brief comparison to commercially available IGBT stacks. The results show the high performance that can be obtained by the GPIS converter.     

R410A 直流变频涡旋压缩机的优化设计

鉴于环境问题的日益突出,各国均开展了 R22制冷剂的替代工作,高效、环保的 R410A 冷媒,已成为业内公认的 R22制冷剂的良好替代物,但空调制冷压缩机要想使用 R410A 替代传统的 R2制冷剂,必须对压缩机结构等多方面进行重新优化设计,才能满足 R410A 制冷剂特性的要求,同时达到高效节能目的。结合实际产品对 R410A 压缩机从涡旋齿结构、壳体结构、润滑油的选择与油路设计等多个方面进行了优化设计,该设计能有效提高压缩机能效比与工作可靠性,为高能效直流变频涡旋压缩的设计提供了参考依据。     

DC/DC变换器模块可靠性寿命预计

本文主要介绍了CETRM(恒定电应力温度斜坡法)可靠性试验方法及模型,基于DC/DC开关电源变换器模块的输入电流、输出电流和输出电压等参数的退化曲线,研究了可靠性寿命预计的算法,推导出模块正常工作条件下的寿命约为8.7×10~4h。根据其参数的退化曲线,确定出模块的失效敏感参数为输出电压,并通过失效机理一致性判别模型得出模块在75～160℃的温度范围内其失效机理是一致的。在此温度范围内求出了样品的失效激活能为0.59eV,最终推导出了模块在室温工作时的寿命,证明了恒定电应力温度斜坡法可以用于预测DC/DC开关电源模块的寿命。     

Optimum variant of D-D fusion ignition for thermonuclear power plants

The main approaches to using D-D fusion reactions for electric power production are discussed. It is suggested that an optimum variant consists in initiating microexplosions with compression of deuterium or another fuel either by thermal radiation of one or several D-T microexplosions or by same radiation and one or several drivers. Using this approach, it is possible to restrict the task to developing drivers with moderate parameters that correspond to the ignition of D-T microexplosions with the yields on the order of 1 GJ or below.     

Optimum interpolation functions for boundary element method

In the Boundary Element Method (BEM) the density functions are approximated by interpolation functions which are chosen to satisfy appropriate continuity requirements. The error of approximation inside an element depends upon the location of the collocation points that are used in constructing the interpolation functions. The location of collocation points also affects the nodal values of the density function and, hence, the total error in the analysis if boundary conditions are satisfied in a collocation sense. In this paper, we minimize the error inside the element using the L₁ norm to obtain the optimum location of collocation points. Results show that irrespective of the continuity requirement at the element end, the location of collocation points computed by the algorithm presented in this paper results in an error that is less than the error corresponding to uniformly spaced collocation points. Results for optimum location of collocation points and the average error are presented for Lagrange polynomials up to order fifteen and for Hermite polynomials that ensure continuity up to the seventh order of derivative at the element end. The information of the optimum location of interpolation points for Lagrange and Hermite polynomials should be useful to other researchers in BEM who could incorporate it into their current programs without making significant changes that would be needed for incorporating the algorithm. The algorithm presented is independent of the BEM application in two-dimensions, provided that the density functions are approximated by polynomials and is applicable to direct and indirect formulations. Two numerical examples show the application of the algorithm to an elastostatic problem in which one boundary is represented by integrals of the Direct BEM while the other boundary by the Indirect BEM and a fracture mechanics problem by Direct method in which the crack is represented by displacement discontinuity density function.     

Digital calibration for monotonic pipelined A/D converters

The original digital calibration approach for 1 b/stage and 1.5 b/stage pipeline analog-digital converters produces missing or nonmonotonic digital codes with the device and circuit impairments typical of modern deep submicrometer CMOS technologies. Two digital calibration algorithms are introduced to improve pipeline performance when using low-voltage low-gain nonlinear operational amplifiers and high random dc offset voltage comparators. The first technique computes calibration coefficients for each stage at actual transition points of the residue characteristic to assure converter monotonicity in the presence of random comparator offset voltages. The second augments a conventional pipelined architecture with an input-dependent level-shifting stage and additional digital calibration circuitry to achieve high differential and integral linearity with low-gain nonlinear operational amplifiers.     

Optimum optical local-oscillator power levels for coherent detection with photodiodes

The use of an optical local oscillator for coherent detection with a photodiode can significantly reduce the responsivity of the detector because of saturation effects. Consequently, local-oscillator shot-noise-limited operation of the detector may not be possible. This effect is analyzed and formulations are developed for the optimum optical local-oscillator power level and the resultant maximum possible signal-to-noise ratio in terms of parameters derived from the photodiode current versus the optical power response curve. An effective heterodyne responsivity that can be used as a part of the specifications when one is procuring photodiodes for use in coherent detection systems is defined.     

Optimum flow conditions for liquid coolants in superconducting power cables

The cost of the helium refrigerator and coolant will form a substantial part of the overall price of a superconducting power cable. This cost is minimized by having coolant circuits, refrigerator spacings, and duct designs which allow the installation of large plant and the efficient use of the helium. The relationships required to achieve these conditions have been theoretically determined and used to analyse a possible cable design.Also, the theory has been extended to establish the cheapest stand-by-plant arrangement and the cost penalty involved when wayleave difficulties necessitates the non-optimum siting of cooling stations.     

Optimum absorbed heterodyne power for superconducting NbN hot-electron bolometer mixer

Absorbed heterodyne power has been measured in a low-noise broadband hot-electron bolometer (HEB) mixer for the terahertz range, operating on the effect of electron heating in the resistive state of an ultrathin superconducting NbN film. It is established that the optimum absorbed heterodyne power for the HEB mixer operating at 2.5 THz is about 100 nW.     

High power factor operation of resonant converters on the utility line

Operation and characteristics of resonant converters on the utility line are presented. Series-parallel (LCC-type) resonant converter operating with discontinuous current mode and continuous current mode (variable frequency control as well as fixed-frequency) are considered. Design examples are presented. SPICE simulation and experimental results obtained for the designed converters (rated at 150 W) are presented to verify the theory. It is shown that high line power factor (>0.95) and line current total harmonic distortion (THD) of <25% are obtained for the LCC-type converter for a wide load range (from full load to 10% rated load) without any active control, and the switch peak current decreases with the load current. With active line current control, low distortion and zero voltage switching for the entire cycle are realized.     

TR组件测试系统功率参数校准技术

研究工作状态下TR组件测试系统功率参数的校准方法,介绍了在脉冲峰值功率条件下功率参数测量标准的仪器组成,分析其功率参数校准的定标方法,并给出相应实验数据。     

Design and comparative study of discrete and module-based IGBT power converters

This paper discusses concepts of a 20 kVA power converter design and key differences between discrete IGBT and module-based design approaches. Module-based power converters have been typically employed in academic and research institutes for power levels of 10 kVA and more. However, with advancement in IGBT technologies and the growing need to minimize system size and weight, designs based on discrete devices are now an attractive alternative for such power levels. A simple procedure is presented for power converter design that includes power loss evaluation, heat-sink thermal characterization, thermal model of overall system and sizing of DC link capacitor. Using the same, a state-of-the-art discrete device and module-based power converters are designed. A comparison is subsequently made, where it is shown that discrete approach yields a compact and economic design up to a power level of 20 kVA. A key objective of this work is to lay emphasis on laboratory design of power converters. This enables a graduate level student to build a converter from start and in the process gain insights into the underlying engineering design aspects.