高功率LLC谐振变换器的设计方法

研究转换器的效率优化问题,基频分量法已广泛应用于高功率LLC谐振变换器设计中.传统方法用正弦波代替谐振电流,忽略了高次谐波的影响.为更有效的改善转换器效率,提出基于时域的LLC谐振转换器的参数设计法.采用时域分析法对谐振变换器的工作过程和状态方程进行分析,绘制直流增益特性和开关损耗优化曲线,对LLC谐振网络进行设计和参数优化.时域分析法不但保证了转换过程中的有用信息不丢失,而且在同一直流增益值下的多组参数组合更利于损耗曲线的绘制,提高转换效率.对1000W LLC谐振转换器仿真结果表明:与基波分量法相比,时域分析法设计的网络参数能更好的满足转换器的工作要求,同时具有更高的转换效率.     

LLC谐振变换器参数改进算法仿真北大核心

采用目前方法对LLC谐振变换器的参数进行优化设计时,没有分析LLC变换器软开关工作条件,无法准确获得LLC谐振变换器的直流增益、谐振电流与等效电阻电流比值、谐振电流以及有功电流,导致优化后的LLC谐振变换器整体性能较差。提出基于改进粒子群的LLC谐振变换器参数优化方法,首先对LLC变换器软开关工作条件进行分析,获得LLC谐振变换器参数优化的约束条件,在此基础上,利用混沌搜索机制改进粒子群算法,利用改进后的粒子群算法完成LLC谐振变换器参数的优化。实验结果表明,所提方法优化后的LLC谐振变换器具有良好的性能。     

基于UCC29950的LLC谐振半桥电源的设计

LLC谐振半桥变换器可以在宽电压范围内全负载条件下实现软开关,在整个工作过程中,实现初级MOSFET的零电压开关(ZVS)和次级整流二极管零电流开关(ZCS)。因此可以达到较高的效率和功率密度,而且在负载和输入电压范围变化较大的情况下,其开关频率变化较小。文中首先分析了LLC谐振半桥变换器的工作原理,并基于TI公司的UCC29950芯片设计了一种300W电源样机,该芯片集成了PFC和LLC控制器。文章重点介绍了LLC谐振半桥变换器的参数设计,实验结果表明该电源性能优良。     

太赫兹固态放大器研究进展

随着半导体技术的发展,晶体管特征频率不断提高,已经进入到太赫兹(THz)频段,使得固态器件可以在THz频段工作。THz放大器可以将微弱的信号进行放大,在THz系统中起着关键作用。介绍了基于氮化镓(Gallium Nitride, GaN)高电子迁移率晶体管(High Electron Mobility Transistor, HEMT)器件、磷化铟(Indium Phosphide, InP) HEMT器件和InP异质结双极晶体管/双异质结双极晶体管(InP Heterojunction Bipolar Transistor/Double Heterojunction Bipolar Transistor, HBT/DHBT)器件的THz单片放大器研究进展。     

LLC谐振变换器线性补偿软启动控制研究

针对LLC谐振变换器启动时的涌流问题,根据LLC谐振变换器原理对频率调节增益和占空比调节增益进行分析,并利用仿真工具和函数拟合工具探究频率调节增益、占空比调节增益与混合调节总增益的关系,提出了一种LLC谐振变换器线性补偿软启动控制策略。此策略根据占空比调节时的增益特点设计占空比变化函数,根据上述分析得到的增益关系,设计频率变化函数,用频率调节增益对占空比调节增益进行线性补偿,使得输出总增益可以趋于线性变化,最大化地抑制启动电流。通过仿真和搭建实验样机,验证了所提出的策略可降低损耗,并有效抑制启动电流,提升了电源系统安全性,降低了设计成本。     

HEMT器件力电耦合传感特性测试

设计了在Si微结构与AlGaN/GaN高电子迁移率晶体管(HEMT)集成的微机电系统(MEMS)。通过微机械加工工艺,完成了力电耦合传感结构的加工。通过实验测试发现HEMT器件具备很强的力电耦合特性,测试结果在-1.5 V栅压下,HEMT器件对应力的灵敏度为123.96 MPa/mA,线性度为6.95%。     

基于Saber器件库的L6599芯片建模及仿真

在中高功率LED灯电源设计中,后级电路常采用LLC拓扑结构。L6599是STMicroelectronics(ST)公司的一款用于LLC谐振变换器的经典控制器,目前很多半桥LLC产品中均采用此IC。因此建立L6599芯片的器件库模型,对于研究以L6599为核心器件的LLC电路具有重要意义。通过Saber软件建立了L6599芯片的器件库模型,实现了其基本功能和各种保护功能。最后用建立的L6599芯片的器件库模型进行半桥LLC谐振变换器的时域仿真,验证了模型的有效性,为缩短产品开发周期,减少研发成本提供了可能。     

Test on electromechanical coupling sensitive property of HEMT device

设计了在Si微结构与AlGaN/GaN高电子迁移率晶体管(HEMT)集成的微机电系统(MEMS).通过微机械加工工艺,完成了力电耦合传感结构的加工.通过实验测试发现HEMT器件具备很强的力电耦合特性,测试结果在-1.5V栅压下,HEMT器件对应力的灵敏度为123.96 MPa/mA,线性度为6.95％.     

半桥LLC谐振变换器的建模及仿真研究

介绍了半桥型LLC谐振变换器拓扑的工作原理,通过基波等效模型分析了电路的直流增益特性,利用Matlab软件绘出了其直流增益曲线,并以此为依据讨论了各参数对LLC谐振变换器的影响,以24 V/192 W电源为例计算出了LLC谐振变换器的变压器匝比、谐振电感、谐振电容和励磁电感等参数。最后用Saber软件进行仿真,通过更改一些参数的方法验证了所述理论的正确性。     

一种LLC谐振变换器设计的新思路

LLC谐振变换器因为工作效率高,且适合工作在高频条件,成为最受关注的直流／直流变换器拓扑之一。然而只有正确合理的设计方法才能得到更高效可靠的产品,分析了LLC各谐振参数对LLC工作状态的影响,表明了各参数之间的相互制约关系,进而提出了LLC设计的一种新思路,最后研制了一台 LLC谐振变换器样机,其较高的变换效率证明了该设计方法的正确性和有效性。     

A new variable-mode control strategy for LLC resonant converters operating in a wide input voltage range

This paper proposes a new variable-mode control strategy that is applicable for LLC resonant converters operating in a wide input voltage range. This control strategy incorporates advantages from full-bridge LLC resonant converters, half-bridge LLC resonant converters, variable-frequency control mode, and phase-shift control mode. Under this control strategy, different input voltages determine the different operating modes of the circuit. When the input voltage is very low, it works in a full-bridge circuit and variable frequency mode (FB_VF mode). When the input voltage rises to a certain level, it shifts to a full-bridge circuit and phase-shifting control mode (FB_PS mode). When the input voltage further increases, it shifts into a half-bridge circuit and variable frequency mode (HB_VF mode). Such shifts are enabled by the digital signal processor (DSP), which means that no auxiliary circuit is needed, just a modification of the software. From light load to heavy load, the primary MOSFET for the LLC resonant converter can realize zero-voltage switching (ZVS), and the secondary rectifier diode can realize zero-current switching (ZCS). With an LLC resonant converter prototype with a 300 W rated power and a 450 V output voltage, as well as a resonant converter with 20–120 V input voltage, the experiments verified the proposed control strategy. Experimental results showed that under this control strategy, the maximum converter efficiency reaches 95.7% and the range of the input voltage expands threefold.     

Enhancement of Johnson figure of merit in III‐V HEMT combined with discrete field plate and AlGaN blocking layer

The performance of AlGaN/GaN HEMT is enhanced by using discrete field plate (DFP) and AlGaN blocking layer. The AlGaN blocking layer provides an excellent confinement of electrons toward the GaN channel, resulting very low subthreshold drain current of 10^?8 A/mm. It reveals very high off state breakdown voltage (BV) of 342 V for 250 nm gate technology HEMT. The breakdown voltage achieved for the proposed HEMT is 23% higher when compared to the breakdown voltage of conventional field plate HEMT device. In addition, the DFP reduces the gate capacitance (C_G) from 12.04 × 10^?13 to 10.48 × 10^?13 F/mm. Furthermore, the drain current and transconductance (g_m) reported for the proposed HEMT device are 0.82 A/mm and 314 mS/mm, respectively. Besides, the cut‐off frequency (f_T) exhibited for the proposed HEMT is 28 GHz. Moreover, the proposed HEMT records the highest Johnson figure of merit (JFOM) of 9.57 THz‐V for 250 nm gate technology without incorporating T‐gate.     

无源无损软开关变换器对比分析

高频化是电力电子装置提高功率密度的有效手段,高频化引起电力电子开关器件的开关损耗增加,无源无损软开关电路可有效降低电力电子开关器件的开关损耗。以最小电压应力（MVS）无源无损软开关电路、非最小电压应力（NMVS）无源无损软开关电路及最小电压电流应力（MVCS）无源无损软开关电路等3种主流的无源无损软开关Buck变换器为对象进行研究,从拓扑结构、占空比、电压电流应力、开关损耗及转换效率等几个方面进行比较研究。搭建了硬件实验环境,经理论分析和实验验证得出MVCS软开关电路具有更加良好的性能,为无源无损软开关电路的应用提供设计依据。     

Look-up table based I-V model for GaN HEMT devices for Microwave Applications

In this work, a newly found innovative interposable lookup table based nonlinear empirical DC I-V model for GaN HEMT device has been formulated. Angelov and Yang's models have been taken as reference models to study the effects of bias (V_gs, V_ds) dependent traps (gate lag and drain lag), self-healing, virtual gate formation, etc. on I-V characteristics functions and their inclusion into I-V equation functions of the proposed model. A new polynomial ratio function of V_ds with its coefficients varying with V_gs has been formulated as a first function of the I-V model equation, to describe the transfer characteristics of the GaN HEMT. The obtained coefficients of the polynomial ratio function have been calculated by the curve fitting tool, are used to form a look-up table so that the I-V model is fast and accurate. Model verification has been done using 8 × 75 µm gate periphery and 0.25 µm gate length GaN HEMT of UMS foundry. The measured and modeled results of I-V characteristics as well as transfer characteristics are compared and found to be matched accurately with each other. Because of this, this model is more accurate and proficient in the representation of GaN HEMT I-V characteristics when compared to the Angelov DC I-V model. The proposed methodology can be used to model all GaN HEMT devices.Using the proposed nonlinear I-V equation, an empirical model has been generated in AWR MWO using an interpolable lookup table of coefficients varying with V_gs for the GaN HEMT of UMS, CREE and WIN foundry, which can be used for Computer-Aided Design (CAD) of RF circuits, etc.     

High‐efficiency transmission‐line inverse Class F power amplifiers for 2‐GHz WCDMA systems

In this article, a novel load‐network solution to implement the transmission‐line inverse Class F power amplifiers for base station WCDMA applications is presented. The theoretical analysis is based on an analytical derivation of the optimum load‐network parameters to control the second and third harmonics at the device output, including the device output parasitic shunt capacitance and series inductance. The transmission‐line inverse Class F LDMOSFET and GaN HEMT power amplifiers using NXP BLF6G22LS‐75 and CREE CGH27060F devices, respectively, were designed and measured. The high‐performance results with the drain efficiency of 70.2% and power gain of 18.0 dB for a 60‐W LDMOSFET power amplifier and with the drain efficiency of 82.3% and power gain of 14.3 dB for a 50‐W GaN HEMT power amplifier were achieved at an operating frequency of 2.14 GHz. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

LLC谐振变换器的扩展描述函数法建模

给出了LLC谐振变换器的等效电路,基于扩展描述函数法建立了该等效电路的小信号模型、得到了LLC变换器的稳态解及其直流电压增益特性。借助PSpice仿真软件得到了该变换器在不同开关频率和不同电路参数下输出变量对控制变量的频率特性曲线。分析了开关频率、输入电压、占空比、品质因数和负载等主要参数对频率特性的影响。所作的工作对变换器参数的优化设计、闭环控制及动态性能设计具有指导意义。     

Analytical and numerical modelling of AlGaN/GaN/AlN heterostructure based cantilevers for mechanical sensing in harsh environments

Some industrial areas as oil, automotive and aerospace industries, require electromechanical systems working in harsh environments. An elegant solution is to use III-V materials alloys having semiconductor, piezoelectric and pyroelectric properties. These materials, particularly nitrides such as GaN or AlN, enable design of advanced devices suitable for harsh environment. A cantilever structure based on AlGaN/GaN/AlN heterostructures coupled with a High Electron Mobility Transistor (HEMT) can act as an electromechanical device suited for sensing applications. In this article, we present the mechanical modelling of such a structure. An analytical and a numerical model have been developed to obtain the electrical charge distribution in the structure in response to mechanical stress. A theoretical electromechanical sensitivity of 3.5 μC m⁻² was achieved for the cantilever free end displacement of several hundreds of nanometres. Both models show good agreement, presenting less than 5% deviation in almost the whole structure. The differences between the two models that are pronounced near the clamped area can be explained by particular boundary conditions of the numerical model. The topological characterization and numerical modelling allowed the estimation of the equivalent intrinsic residual stress in the structure and the stress distribution within each layer. Finally, the dynamic mechanical characterization of fabricated cantilevers using laser interferometry is presented and compared to numerical modal analysis with less than 10% deviation between theoretical and experimental resonant frequencies. The obtained results enable the use of the analytical model for further study of the electromechanical coupling with the HEMT structure.     

On the performance of GaN‐on‐Silicon,Silicon‐Carbide,and Diamond substrates

In this article, threading dislocations and its impact on the electrical and thermal performance of GaN‐on‐Diamond (Dia), ‐SiC, and ‐Si high electron mobility transistor (HEMT) has been investigated. TCAD simulation of GaN‐HEMT is performed with various buffer traps to mimic the lattice mismatch/dislocation density at GaN/Si, GaN/SiC, and GaN/Dia interface. It has been found that, the dislocations not only induce traps, but also degrade the thermal conductivity of the GaN‐buffer. This accordingly could deteriorate the thermal characteristic of GaN‐on‐Dia, which has higher lattice mismatch with respect to GaN‐on‐SiC. This investigation showed that the growth process of GaN‐on‐Dia should be optimized in order to reduce the threading dislocations. This accordingly could dramatically further improve its outstanding thermal characteristics with respect to GaN‐on‐SiC and GaN‐on‐Si devices.