Charge control for zero-voltage-switching multiresonant converter

The operation of zero-voltage-switching multi-resonant power converters (ZVSMRCs) limits the use of peak current-mode control. The charge control technique is found applicable to ZVSMRCs for improving dynamic performance. Charge control compares the total charge of the switch current to the control voltage to modulate the switching frequency. Since the charge of the switch current of the forward ZVSMRCs is proportional to the input voltage, charge control provides a fast inner loop and offers excellent transient response. Charge control also provides the possibility to achieve current sharing for ZVSMRC parallel applications     

Low-voltage, high-efficiency switch-mode high-power inverters forAC link converter applications

A 30 kVA high-frequency link converter, which consists of 6×5 kVA center-tap power block topologies operating in parallel, is considered for battery-fed DC-AC converter applications. Practical solutions for minimizing currents circulating between the different power blocks, avoiding transformer saturation in forced commutated center-tap topologies, and minimizing transistor-on losses are incorporated and illustrated by means of practical measurements and results. A simple single-capacitor snubber network, operating in parallel with a second-stage capacitor snubber, is used for these converter types. Typical applications include mobile and telecommunications uninterruptible power supply systems; high AC-voltage loads fed from photovoltaic or hybrid energy systems; and battery-fed, mobile, variable-speed AC and DC drives     

Inverse dual converter (IDC) for high-power DC-DC applications

A family of DC-DC converters suitable for high-power applications is introduced. The inverse dual converter (IDC) is capable of continuous voltage step-up or step-down control over a wide range of and without the need of a transformer. Experimental verification of the analysis is given for the simple single-phase IDC. Some of the more sophisticated members of the IDC family are described, and their characteristics and possible application, are mentioned     

An improved ZCT-PWM DC-DC converter for high-power and frequency applications

In this paper, an improved active resonant snubber cell that overcomes most of the drawbacks of the normal zero-current transition (ZCT) pulsewidth-modulation (PWM) dc-dc converter is proposed. This snubber cell is especially suitable for an insulated gate bipolar transistor (IGBT) PWM converter at high power and frequency levels. The converter with the proposed snubber cell can operate successfully with soft switching under light-load conditions and at considerably high frequencies. The operation principles, a detailed steady-state analysis, and a snubber design procedure of a ZCT-PWM buck converter implemented with the proposed snubber cell are presented. Theoretical analysis is verified with a prototype of a 5-kW and 50-kHz IGBT-PWM buck converter. Additionally, at 90% output power, the overall efficiency of the proposed soft switching converter increases to about 98% from the value of 91% in the hard-switching case.     

Soft recovery PWM converter with energy recovery and foldingsnubber network suitable for high-power applications

A new soft recovery converter that operates in a more reliable and efficient manner than conventional converters by employing a multiple order folding snubber network (MFSN) and energy recovery network (ERN) is proposed. The new converter is suitable for low-cost, high-voltage and high-power applications operating at output powers of up to several kilowatts     

Analysis of a multiresonant forward converter based on nonidealcoupling of the transformer

There are many transformer applications where tight coupling is difficult to achieve. Therefore, an analysis of a resonant converter with a nonideal coupling is required. In this paper, a forward resonant converter with a coupling ranging from zero to one was analyzed. It was found that the traditional quasi-resonant converter becomes a multiresonant converter when the coupling is less than one. This is because the finite switching time of the rectifying diode reduces the input inductance of the transformer to effectively give a converter that uses two different inductances during any one switching period. It was also found that, in general, the converter has seven topological states. The design equations are derived analytically to provide a fundamental understanding of the converter. The peak voltage and current stress of the power switch as a function of the coupling were investigated. It was found that as the coupling is reduced, the peak voltage reduces and the peak current increases. A 48-5 V 20-W forward converter with a coupling of 0.9 was designed and tested. A coupling of 0.9 was chosen as it gives a duty cycle of 50%, has zero voltage switching for all loads, and has a peak switch voltage of 3.3 times the input voltage. The experiment verified the analysis and the practicality of a reduced coupling transformer, and the measured efficiency of the converter was 80%     

Steady-state operation of a high-voltage multiresonant converter in a high-temperature environment

Often scientific instruments on exploratory satellites are used to collect cosmic particles. These instruments, such as the Faraday cup, require a high-voltage regulated power source. On the proposed solar probe satellite there will be instruments which will collect cosmic particles close to the sun. Naturally temperature effects on the voltage regulator are a concern. Specifically power dissipation within the regulator must stay within stringent guidelines. The high-voltage regulator circuit is a resonant flyback topology with a dissipative series switch whose on resistance controls the output voltage level. The extreme temperatures in space will change the inductance of the flyback transformer which will affect the output voltage. State space analysis techniques are used to determine how the value of the transformer inductance and capacitance in the flyback converter affects the output voltage and consequently the power dissipated by the transformer and the switch. The accuracy of the analysis is verified by comparing results with those obtained from an experimental circuit. The results can then be used to help the designer chose nominal capacitance and inductance values that will work over the temperature range of interest.     

Current-limiting thermistors for high-power applications

Applications of positive-temperature-coefficient polymer thermistors as current-limiting elements in high-power systems are complicated by the nonlinear scaling of device parameters. The spatial and temporal evolution of the internal quantities temperature and electric field, and the temporal evolution of the external device property resistance, are described here as calculated according to a one-dimensional electrothermal model. Under a steeply ramping current excitation, a longitudinal heating instability compresses the electric field into the center of the material, thereby inducing dielectric failure. Insight into the design of a useful device is provided by results of calculations under three different conditions     

140 GHz回旋管高转换效率准光模式变换器设计研究（英文）

成功实现高转换效率的140 GHz TE22,6准光模式变换器原型设计。基于周期微扰原理设计Denisov辐射器,实现低边缘绕射的初级出射波束。针对三镜面光路系统,采用全矢物理光学积分作为主要计算手段,围绕主极化场分量进行三级相位修正面迭代优化,实现高出射高斯纯度的模式场转换,其中一级镜的修正有效改善了辐射器出射的不理想性。基于全矢数值仿真确认,相比原二次曲面原型设计,相位修正后的变换器系统的出射高斯纯度从92.7%提高到99.6%,结合98.8%以上的功率传递效率,实现了性能优越的高阶回旋管准光模式变换器原型设计。     

A three-phase multilevel converter for high-power induction motors

A new converter topology for drives is presented in this paper: a three-phase multilevel converter with separately regulated DC power supplies. The DC voltages are provided by medium-frequency DC-DC converters. The applications for the converter are especially high-power traction systems, where the voltage applied to the induction motor is bigger than 1 kV. The motor current is of a very high quality, compared to a classical three-phase converter. This allows keeping the switching frequency low by using phase-shifted pulsewidth modulation (PWM) carriers. Different modulation methods have been developed and simulated. Experimental tests have been made on a 12 kW prototype     

Nondissipative switched networks for high-power applications

The letter seeks to extend the concepts of active-filter theory to high-power applications. Current-fed switched-capacitor networks and voltage-fed switched-inductor networks are efficient topologies suitable for high-power operation. Passive and active switched networks realised include the transformer, gyrator and a negative inductor using a generalised impedance convertor.     

Inductor design for high-power applications with broad-spectrumexcitation

The design of high-power inductors for applications with broad current spectrum excitation is a challenging task. The resonant inductor of a resonant DC-link inverter (RDCLI) is one such example. The inductor current consists of a resonant current component, a DC component, which supplies the active power to the load and a modulation component, which depends on the modulation strategy. In addition, the frequency and amplitude of the dominant current components change with operating point. Conventional inductor designs for single-frequency excitation do not perform well in broad-spectrum applications. In order to improve these designs, the impact of broad current spectrums on winding design, core selection, power density, and thermal-handling capability must be investigated. In this paper, alternate inductor topologies, which better address the above issues, are proposed and investigated     

State-of-the-art, single-phase, active power-factor-correction techniques for high-power applications - an overview

A review of high-performance, state-of-the-art, active power-factor-correction (PFC) techniques for high-power, single-phase applications is presented. The merits and limitations of several PFC techniques that are used in today's network-server and telecom power supplies to maximize their conversion efficiencies are discussed. These techniques include various zero-voltage-switching and zero-current-switching, active-snubber approaches employed to reduce reverse-recovery-related switching losses, as well as techniques for the minimization of the conduction losses. Finally, the effect of recent advancements in semiconductor technology, primarily silicon-carbide technology, on the performance and design considerations of PFC converters is discussed.     

Electronic properties of diamond for high-power device applications

The generation and transport of impact-ionized electrons in diamond are investigated using secondary electron emission spectroscopy. By studying secondary electron emission from diamond surfaces having a negative electron affinity (NEA), the total transmitted intensity and the full energy spectrum of the internal electrons are revealed in the measurements. Electron yield and energy distribution measurements from C(100) and CVD diamond samples are analyzed as a function of incident beam energy and information is obtained on both the internal gain and electron energy distribution following impact ionization as well as the effects of the transport process on the internal electron distribution. High internal gain and efficient electron transport are inferred from an analysis of the very high yields measured from both samples. In fact, by fitting calculated yield curves to the measured yield data, we deduce a lower limit on the electron escape depth of 5 μm and 1.3 μm in the C(100) and CVD diamond samples, respectively. Energy spectra measured from the diamond samples contain an intense, low-energy peak whose energy position and width are independent of incident beam energy. Based on an analysis of the energy distribution data, a model of the impact-ionization process in diamond is presented.     

A series resonant converter for arc-striking applications

Initiation of a plasma conduction state requires a relatively large voltage to ionize the gas. A new version of the series resonant converter is proposed that uses the magnetizing inductance of the transformer for resonance. This converter is not suitable for most power supply applications, but the unique load characteristics associated with plasma loads make this type of converter well suited for arc striking, while allowing safe operation during the plasma state. A feature of the resonant converter is that the controller need not be complex, thus making it suitable for application in competitive industrial systems. Possible transformer configurations are investigated, which include an air core and a number of ferrite cored transformers. The series resonant converter with the best-suited transformer is verified experimentally in a tungsten inert gas welding application     

A comparison of high-power converter topologies for the implementation of FACTS controllers

This paper compares four power converter topologies for the implementation of flexible AC transmission system (FACTS) controllers: three multilevel topologies (multipoint clamped (MPC), chain, and nested cell) and the well-established multipulse topology. In keeping with the need to implement very-high-power inverters, switching frequency is restricted to line frequency. The study addresses device count, DC filter ratings, restrictions on voltage control, active power transfer through the DC link, and balancing of DC-link voltages. Emphasis is placed on capacitor sizing because of its impact on the cost and size of the FACTS controller. A method for the dimensioning the DC capacitor filter is presented. It is found that the chain converter is attractive for the implementation of a static compensator or a static synchronous series compensator. The MPC converter is attractive for the implementation of a unified power flow controller or an interline power flow controller, but a special arrangement is required to overcome the limitations on voltage control.     

High-efficiency and high-power vertical-cavity surface-emittinglaser designed for cryogenic applications

We report the first AlGaAs-GaAs vertical-cavity surface-emitting laser (VCSEL) that has been optimized for cryogenic applications near 77 K, with superior characteristics that include a high-output power (P_out=22 mW at I=25 mA), high power conversion efficiency (ηd=32%), low threshold voltage (V_th=1.75 V) and current (I_th=1.7 mA), and low power dissipation (9 mW at P_out =2.0 mW) for a 20-μm-diameter device     

A low voltage, dynamic, noninverting, synchronous buck-boost converter for portable applications

With the increasing use of low voltage portable devices and growing requirements of functionalities embedded into such devices, efficient power management techniques are needed for longer battery life. Given the highly variable nature of batteries (e.g., 2.7-4.2 V for Li-ion), systems often require supply voltages to be both higher and lower than the battery voltage (e.g., power amplifier for CDMA applications), while supplying significant current, which is most efficiently generated by a noninverting buck-boost switching converter. In this paper, the design and experimental results of a new dynamic, noninverting, synchronous buck-boost converter for low voltage, portable applications is reported. The converter's output voltage is dynamically adjustable (on-the-fly) from 0.4 to 4.0 V, while capable of supplying a maximum load current of 0.65 A from an input supply of 2.4-3.4 V. The worst-case response time of the converter for a 0.4 to 4 V step change in its output voltage (corresponding to a 0.2 to 2 V step at its reference input) is less than 300 /spl mu/sec and to a load-current step of 0 to 0.5 A is within 200 /spl mu/sec, yielding only a transient error of 40 mV in the output voltage. This paper also presents a nonmathematical, intuitive analysis of the time-averaged, small-signal model of a noninverting buck-boost converter.     

A rail-to-rail differential quasi-digital converter for low-power applications

This paper presents an ultra low power differential voltage-to-frequency converter (dVFC) suitable to be used as a part of a multisensory interface in portable applications. The proposed dVFC has been designed in 1.2-V 0.18-μm CMOS technology, and it works properly over the whole differential input range (0.6 ± 0.6 V) providing an output frequency range of 0.0–0.9 MHz. The system has been tested for temperature variations from ?40 to +120 °C and supply voltage variations of up to 30 %, being the maximum linearity error in the worse case of 0.017 %. Simulations against common mode voltage variations show a deviation in the output frequency of 0.4 %. This dVFC has power consumption below 60 μW, and it includes an enable terminal that sets the system in a sleep mode (180 nW) while no conversion is request. The dVFC occupies an active area of 250 μm × 150 μm.     

A generic soft switching converter topology with a parallelnonlinear network for high-power application

A soft switching concept that derives from the resonant link and resonant pole power converters and combines the best features of resonant and hard switching converters is applied to a phase arm. The inductor of the resonant LC is designed to saturate, thus having effectively two inductance values: a very large value during the conduction period and a small value that is only active during switching. The advantage of this technique is that a resonant tank with smaller continuous ratings can be used without giving up the component count advantage of resonant power converters. Another feature, contrary to other resonant topologies, is that semiconductor switches need not be overdimensional for voltage and current rating