谈大功率功放机功放管的功率均衡

在大型扩声系统中，功放机是经常损坏的设备，而且损坏的情况大部分是末级功率放大器件的烧坏。经过对正常工作的功放机仔细观察发现，末级并联使用的同型号大功率三极管（场效应管）工作时，往往有的温度高，有的温度低。其中造成上述情况的主要原因是并联使用的大功率三极管（场效应管）在装机时由于筛选时的疏忽或长期运行造成特性参数差异，引起负荷不均匀。负荷大者，工作电流大，发热也较大，容易先坏。负荷小者，工作电流小，发热也较小。但发热大的损坏后，发热小的也不堪重负，短时间内也会烧毁。因此，延长功放机使用寿命，末级功…     

电源及电源管理

输出300mA的低压差线性稳压器 Maxim公司的MAX8887/MAX888为低压差线性稳压器,输入电压范围:+2.5V至+5.5V,连继输出300mA电流(脉冲电流达500mA),MAX8887的噪声很低,而MAX8888具有开漏输出的“电源正常”指示器。它们在输出电流为200mA时压差为     

高功率因数电源设计

功率因数是开关电源设计的关键指标,提高功率因数是开关电源发展中一直重视的技术问题.这里设计的高功率因数开关电源应用PFC控制方式,引进TI公司新推出的UCC28019芯片,明显提高了功率因数.该电源由AC/DC变换电路、DC/IX;变换电路、PFC控制电路、功率因数检测电路、数字设定及测量显示电路、保护电路等6部分组成.其中,AC/DC变换电路采用桥式不控整流方式,DC/DC变换电路采用Boost拓扑结构,可实现30～36 V可调输出,并利用MSP430F247单片机实现数字设定、测量显示及功率因素检测等功能.该电源的主要优点是:功能直观、稳定性好、功率因数大幅度提高.     

含风力发电的电网无功优化

将改进后的PBIL算法运用到含风力发电机组的IEEE30节点系统的无功优化计算中,并对多次独立计算的结果做了统计和分析,与采用标准的遗传算法（SGA）的计算结果的比较,请明该算法在此类无功优化问题中有效性和可靠性。     

管理/转换IC促数字电源发展

数字电源管理IC是个新概念,它融合了模拟管理与数字转换,提高了电源效率.近日,美国Ziler Labs公司来华介绍了数字电源及Zilker的新产品.     

功率管理实现最优功率设计

为了实现目前的功率管理目标,需要采取一种全面的功率管理方法,下至晶体管,上至全芯片技术,悉数包含在内。     

开关电源待机功率设计的几种思路

通过开关电源待机功耗改进方法的研究来提高产品的节能能力。     

电源应用集成功率半导体器件

ISOPLUS 14IM系列功率半导体器件提供的性能使其非常适合开关模式电源(SMPS)应用:集成度高、工作特性可针对高开关频率优化、集成隔离/绝缘措施可以简化安装,此外对于高电压应用如果需要的话还可提供较大的防放电和漏电间隔。本文详细介绍了这些器件所使用的技术,并特别针对开关电源应用讨论了其特性。     

电源加电期间对多组电源的跟踪

引言现代的许多电路都需要多组电源，它们必须以一定顺序启动，从而避免损坏敏感元器件。在很多情况下，强制各组电源同时提升电压是较受欢迎的方案，但遗憾的是，当电源来自多个不同的来源时，这就变得困难了，因每个都有其自身的上电时间和瞬态响应。不过，有一个简单方案可实现高达5组电源的同步上升。如图1所示，该电路解决这问题的方法是在每组电源输出与负载之间接入一个N沟道MOSFET。当电源首先施加到电路时，各MOSFET被关断，而每组电源可按各自的速率进入上电过程，一旦各组电源完成上电，MOSFET管的公共栅极提升电压，使…     

应用于电源中的集成功率半导体器件

ISOPLUS i4^TM系列功率半导体器件具有非常适合应用于开关模式功率电源（SMPS）的特征：器件的集成度高，在应用于高开关频率时工作性能可进行优化，一个集成的隔离有助于降低装配工作的难度，如果要求应用于高压场合可通过加大爬电距离和穿透深度来完美地实现。本文对这类元件使用的技术进行深入的介绍，并针对SMPS上的应用来论述它们的特性。     

电源与电源管理技术发展趋势

随着节能、再生能源、"绿色"和电子设备必须遵守强制性能效规范,以及便携装置小型化多功能的发展趋势,要求电源与电源管理必须提高电源效率、降低待机功耗、改善功率因数、高功率密度、高可靠性、高集成度、小尺寸、安全和低成本。为了向读者介绍最新的电源与电源管理技术,本刊采访了一些著名公司,包括NS,Maxim,Linear,ON Semiconductor,Microchip,Fairchild,Renesas Technology,Infineon等,他们就电源与电源管理技术的发展趋势、创新技术、新产品及其应用、典型解决方案等发表了独特见解。下面是访谈录。     

低功率高压电源的模块化设计

随着现代雷达技术的飞速发展，以及现代雷达对缩短研制周期、提高可维护性和可靠性的要求，小型化、模块化已经成为现代雷达技术发展的方向。作为雷达发射机关键部分的高压电源必须进行模块化设计，提高效率和可维护性以及可靠性，减小体积和重量，以适应现代雷达的要求，本文重点介绍低功率高压电源的模块化设计。     

全新的电源新品和电源系统设计工具

美国国家半导体公司（NS）新推出全新的SIMPLE SWITCHER系列新品及增强板WEBENCH设计工具。     

基于有源功率因数校正的高功率因数电源设计

构建有源功率因数校正（APFC）的高功率因数直流电源。该系统采用TI公司专用APFC整流控制芯片UCC28019作为控制核心,构成电压外环和电流内环的双环控制。其中内环电流环作用是使网侧交流输入电流跟踪电网电压的波形与相位;外环电压环为输出直流电压控制环。外环电压调节器的输出控制内环电流调节器的增益,使输出直流电压稳定。系统采用ATmega16单片机进行监控,完成输出电压的可调以及输入功率因数、输出电压、输出电流等的实时测量与显示和输出过流保护等功能。实测表明,系统性能指标完全达到或超过设计要求。     

Receiver Power Allocation and Transmitter Power Control Analysis for Multiple-Receiver Wireless Power Transfer Systems

As different power has its own receivers, this paper analyzes and designs a multiple-receiver wireless power transfer (WPT) system systematically. The equivalent circuit model of the system is established to analyze the key parameters including transmitter power, receiver power, transmission efficiency, and each receiver power allocation. A control circuit is proposed to achieve the maximum transmission efficiency and transmitter power control and arbitrary receiver power allocation ratios for different receivers. Through the proposed control circuit, receivers with different loads can allocate appropriate power according to its power demand, the transmitter power and system efficiency do not vary with the change of the number of receivers. Finally, this control circuit is validated using a 130-kHz WPT system with three receivers whose power received is 3:10:12, and the overall system efficiency can reach as high as 55.5%.     

电源及电源管理领域的几个创新

2011年,电源类半导体产品将是一个250亿美元的庞大市场。本文介绍数字电源、功率器件与电源管理的部分发展趋势,及典型企业Intersil、英飞凌与Wolfson的产品动向。     

采用交流能源的低功耗CPL电路

从改变CM O S电路中能量转换模式的观点出发,研究CPL电路在采用交流能源后的低功耗特性。在此基础上提出了一种仅由nM O S构成的低功耗绝热电路——nM O S Com p lem en tary Pass-trans istor A d iabaticLog ic(nCPAL)。该电路利用nM O S管自举原理对负载进行全绝热驱动,从而减小了电路整体功耗和芯片面积。nCPAL能耗几乎与工作频率无关,对负载的敏感程度也较低。采用TSM C的0.25μm CM O S工艺,设计了一个8-b it超前进位加法器和功率时钟产生器。版图后仿真表明,在50~200 MH z频率范围内,nCPAL全加器的功耗仅为PAL-2N电路和2N-2N 2P电路的50%和35%。研究表明nCAPL适合于在VLS I设计中对功率要求较高的应用场合。     

Active Power Factor Correction for Switching Power Supplies

The harmonic-free utility/dc interface provides to the computer industry a means to extract more power from the wall outlet than the normal rectifier, with its heavily distorted input current, will allow. Due in part to the very high switch stresses in this interface, however, the cost appears to be too high to justify its use at this time. An alternate approach is proposed that focuses on power factor correction rather than harmonic reduction. Compared to the harmonic-free interface, the switch stress of this new approach is approximately a factor of two smaller.     

Power Amplifier Protection by Adaptive Output Power Control

Cellular phone power amplifiers (PAs) operate in strongly varying environments and have to withstand extreme conditions. To avoid destructive breakdown a generic protection concept is proposed that is based on adaptive control of the output power. It provides over-voltage, over-temperature, and/or over-current protection by detection of the collector peak voltage, die temperature, and/or collector current to reduce the effective power control voltage once a threshold level is crossed. By applying protections, PAs can be implemented in low-cost silicon technology competitively to GaAs HBT implementations. In addition, requirements on package thermal resistance are relaxed. In this paper a theoretical analysis is given on the behavior of a class-AB amplifier under mismatch conditions. Measurement results on a silicon bipolar power transistor with integrated protection circuits are presented, proving the concept of adaptive protection. For a supply voltage of 5 V and nominal output power of 2 W no breakdown is observed for a VSWR of 10 over all phases when output power is adaptively reduced by 2.7 dB at most.     

Novel Tracking Power Supply for Linear Power Amplifiers

Conventional linear power amplifiers (LPAs) show a high output voltage quality but are characterized by high power losses and/or low power density. Therefore, there is a growing interest in increasing the efficiency of LPAs, e.g., for the realization of high power testing voltage sources. In this paper, a high-frequency isolated boost-type tracking power supply (TPS) system is proposed for the conditioning of the input voltage of an LPA. The output voltage of the TPS is varied according to the voltage to be formed by the LPA so that the voltage drop across the power amplifier output transistors is reduced to low values. This results in a significant increase of the total system efficiency. The operating principle of the proposed system is described. A design method for the output filter using the power supply rejection ratio of the LPA is proposed. This method ensures that the amplifier output voltage has minimal switching frequency components. Furthermore, a control system design method is presented that ensures good performance in the control of the constant inductor current of the switch-mode tracking stage. Finally, the theoretical considerations are verified by measurements on a 1-kW laboratory prototype.