在噪声敏感应用中使用PWM伺服放大器

数字PWM伺服放大器相比线性伺服放大器具有体积小、高效、廉价和易于使用等特点。电机驱动伺服放大器的输出电压有一个基频和幅度,它对应于电机的速度、转矩和电机的极数。PWM放大器本身也会产生较高频率的电压成份,主要对应于PWM的上升与下降时间和重复速率。PWM输出的快速边沿会将噪声电流电容性耦合到周围的导体上,     

用于数字D类放大器的双边PWM调制模块

文中介绍了一种双边PWM调制的数字D类放大器调制模块,使用伪自然采样法消除谐波失真。该伪采样算法是将牛顿-拉夫森迭代法和多项式逼近法相结合而形成的。近年来,虽有较多关于前沿PWM调制（LEPWM）和后沿PWM调制（TEPWM）的数字D类放大器的文献,但基于双边PWM（DEPWM）调制的数字 D类放大器方面的文献较少。因此本文利用现有的噪声整形技术,基于牛顿-拉夫森迭代法的伪采样算法等实现了一种用于数字D类放大器的双边PWM调制模块,并使用FPGA搭建了一个24位立体声数字音频D类放大器调制系统。经测试,该调制系统THD＋N@6 kHz性能达到-80.5 dB。     

3-state BTL closed-loop PWM Class D amplifiers

One of the shortcomings of a number of Class D amplifiers (CDAs) designs is their susceptibility to supply noise, quantified by Power Supply Rejection Ratio (PSRR). Reported investigations thereto to-date remain incomplete/over-simplified, particularly the assumption that the AC ground is noise-less and a simplified fully-differential integrator model. In this paper, the effect of supply noise in the AC ground to PSRR is analytically investigated, and the associated analytical expressions derived. Of specific interest, the analysis is applied to the ubiquitous 3-state Bridge-tied-load (BTL) closed-loop PWM CDA, taking into consideration not only the effect of the non-ideal AC ground, but also the effect of the resistor and capacitor mismatch based on a realistic fully-differential integrator model. Further, the PSRR analysis of 3-state BTL closed-loop CDAs has to date been limited to the single-feedback topology and in this paper, extended to the double-feedback topology. These analyses and derived equations herein are useful as they provide valuable insights to CDA designers into the PSRR mechanisms—for example, the counter-intuitive observation that the CDA with 1st-order integrators provides similar or better PSRR than the CDA with 2nd-order integrators if both CDAs are designed to the same carrier attenuation—including the effect of various circuit parameters, and ensuing trade-offs. The derived analytical expressions are verified by means of HSPICE simulations and on the basis of practical measurements on discretely-realized CDAs.     

PWM功率放大器在直流伺服系统中的应用

介绍了PWM功率放大器的基本概念和分类,详细说明了H型双极可逆PWM系统的工作原理及其与单极、受限单极的区别。研制了基于智能功率模块PM75CES060的H型可逆PWM功率放大器,实验结果表明该系统具有高可靠性和较好的实用价值。     

Photonic switching modules designed with laser-diode amplifiers

Photonic switching elements are designed from semiconductor optical amplifiers and passive couplers with fiber-to-fiber unity gain and low crosstalk. Designs for a 2×2 and an asymmetric 2×3 element, and several designs for 4×4 elements, are presented. While most amplifier analyses have stressed the importance of ultralow facet reflectivities for high-gain operation, with protection against external reflections with optical isolators, modest facet reflectivities are satisfactory for these elements. It is also shown that substantial amounts of external reflection can be tolerated. The various architectures are compared according to amplifier count, blocking characteristic, broadcast potential, noise power (amplified spontaneous emission), and fault tolerance     

Parallel operation of power transistors in switching amplifiers

The previous literature has considered the equalization of collector currents of paralleled transistors in switching-mode power amplifiers by adding emitter resistors. This letter presents the possibility of equalizing the collector currents by using base resistors; the advantage is lower power dissipation. Experimental confirmation is given.     

Digital linearizer for RF amplifiers

Broadcast technology is at the beginning of a new era. It is characterized by the intensive use of the most advanced digital modulation formats (8VSB, QAM, OFDM) in combination with high power RF amplifiers. To date the linearity required for these digital formats has only been accomplished in cumbersome low efficiency class A amplifier or even more cumbersome feed-forward systems. A potentially more efficient and cost effective approach is the combination of nonlinear power amplifiers and a predistortion technique capable of compensating for the nonlinear amplifiers. Digital predistortion will provide a highly linear output and improved efficiency. Itelco has developed a digital adaptive base band predistorter to provide for improved performance and cost. The technique is independent of the modulation type, the output frequency, or the signal bandwidth. Furthermore the capability of automatic adaptive predistortion to compensate for the environment (temperature, power supply variations, aging, and even operation during replacement of a faulty module) is highly desirable     

PWM zero-voltage switching boost-derived converters with outputisolation

In this paper, the basic operations and steady-state analysis for three modified boost-derived power converter topologies are presented. Unlike the conventional boost topology, these power converters provide electrical isolation and zero-voltage switching, while having identical component stresses as those in the conventional boost power converters. Zero-voltage switching and proper transformer-core resetting are achieved from the resonance that occurs between the parasitic capacitance of the power switch and the transformer magnetizing inductance. By introducing a lossless clamping circuit, the voltage stresses across the switching devices are limited to the reflected output voltage to the primary side     

“Dead-band” PWM switching patterns

Reference/modulating waveform continuity is not a necessary condition for the implementation of switching patterns for three-phase pulse-width modulated (PWM) converters if the load or the source are Y-connected. This is based on the fact that the converter phase-voltages do not need to be sinusoidal and switching pattern discontinuities-“dead-bands”-do not degrade the quality of output/input voltage/current waveforms by introducing low-order harmonics if certain parameters are optimized. This paper discusses general characteristics of various discontinuous switching patterns for PWM converters and shows that they can yield better performance than their continuous counterparts in some operating regions. Performance is defined as harmonic distortion normalized with respect to effective switching frequency and serves as a measure of comparison with continuous PWM techniques, The applications considered include general purpose and application specific solid-state power supplies using voltage source inverters and PWM rectifiers. Theoretical considerations are verified on an experimental unit     

The class-E/F family of ZVS switching amplifiers

A new family of switching amplifiers, each member having some of the features of both class E and inverse F, is introduced. These class-E/F amplifiers have class-E features such as incorporation of the transistor parasitic capacitance into the circuit, exact truly switching time-domain solutions, and allowance for zero-voltage-switching operation. Additionally, some number of harmonics may be tuned in the fashion of inverse class F in order to achieve more desirable voltage and current waveforms for improved performance. Operational waveforms for several implementations are presented, and efficiency estimates are compared to class-E.     

Optical switching between damped bistable soliton states usingperiodic amplifiers

The possibility of cyclic switching between bistable soliton states of the undamped generalized nonlinear Schrodinger equation (GNLSE) has been previously studied by the authors. It is shown that it is possible to maintain bistable solitary wave solutions of the GNLSE in the presence of damping by using localized periodic amplifiers and switch states from low to high and vice versa while maintaining stability. Provided that materials with the appropriate nonlinear mechanisms can be found or fabricated, this simulation points in the direction of two-state optical transmission systems that permit signal processing     

All-optical switching by counterpropagating operation in cascadedsemiconductor optical amplifiers

We propose a simple, compact, integrative, flexible, power-efficient, and all-optical switch. The operation is based on self-induced gain modulation leading to nonlinear transmittance with a threshold level dependent on input powers of the data and control signals counterpropagating in cascaded semiconductor optical amplifiers. We demonstrate numerically the all-optical switch with small-signal modulation, low-power consumption, high-output power, and high-output extinction ratio     

A centroid-based PWM switching technique for full-bridge inverterapplications

A novel centroid-based pulse-width-modulation (PWM) switching strategy is proposed which is suitable for full-bridge inverter applications. This method is evaluated, and its performance is compared with existing PWM switching strategies. The performance evaluation and comparison are based on the total harmonic distortion (THD) and number of pulses per cycle of the inverter output waveform. The objective of the new switching strategy is to minimize both the THD and low-order harmonics. Simulation results show that this technique yields a significant improvement in performance. In addition, a hybrid switching sequence is developed for the proposed scheme, which can lead to further reduction in switching losses     

Novel random PWM schemes with weighted switching decision

A new random pulse-width modulation (RPWM) scheme, which includes a weighted decision switching process, has been developed and tested. The switching strategy can be applied to the entire range of the modulation index. The scheme combines the advantages of the deterministic nature of the standard pulse-width modulation (PWM) schemes, and the nondeterministic spread-spectral characteristic of RPWM schemes. Test results have confirmed the improved spectral performance of the proposed schemes over a standard RPWM scheme at both low- and high-modulation indexes     

Two-level switching pattern deadbeat DSP controlled PWM inverter

A two-level switching algorithm of the deadbeat controlled PWM inverter is presented. Two levels, instead of three levels, are used in the pulse pattern. This scheme allows the use of higher switching frequency for a given computation time delay, which results in lower total harmonic distortion (THD) at the output. Control algorithms are derived. The proposed control scheme is implemented using a TI TMS320C14 DSP controlling an inverter to produce a very low THD sinusoidal output voltage. Simulation and experimental results are presented to verify the performance     

Analysis of random PWM switching methods for three-level powerinverters

This paper presents a generalized theory which covers both two-level and three-level random pulsewidth modulation (RPWM) schemes. Various three-level RPWM schemes with low switching frequency are presented and compared with two-level schemes. Three-level RPWM schemes have less discrete harmonics and continuous noise than two-level RPWM schemes. They have desirable spectral characteristics and can be employed in high-voltage inverter-fed motor drives. Measurements have confirmed the theory and the attractive features of three-level RPWM schemes     

第一讲：异步电动机的变压变频调递原理和稳态特性

自20世纪80年代以来，在电气传动领域中用交流电机调速取代直流电机调速一直是不可逆转的趋势。目前，交流调速已成为满足各种生产工艺要求和节约电能的重要措施。在多种交流调速方法中，变频调速的应用发展最快，尽管变频器的生产成本稍高，但其调速性能和装置效率始终处于各种调速方法之首。因此，现在变频调速的应用已成为交流电机调速的主流。据统计，近年来国内变频器市场保持着12％-20%的年增长率，处于一个高速增长的时期，预计2006年的年销售量将超过70亿元。有鉴于此，普及变频调遮原理和应用的知识十分重要，为了适应需要，《电力电子》杂志编委会要我撰写“交流电机变频调速”的连载讲座，谨在拙著《电力拖动自动控制系统——运动控制系统》和《交流调速系统》的基础上，删去深入的理论分析和公式推导，加强应用实例，以飨读者。[编者按]     

CATV干线放大器开关电源设计

1引言目前国产CATV干线放大器电源,大多由电源变压器和三端稳压器组成,其优点是电路简单,纹波电压小,维修简便,缺点是功耗大,效率低,体积大,对电压变化适应能力小。在有线电视系统中,干线放大器通常采用集中供电,在这种情况下,对干线放大器的电压适应范围、功耗和效率提出了更高、更严格的要求。显然,采用开关电源能够较好地满足这些要求。2PWR—TOP204YAIPWR－TOP204YAI是美国PowerIntegration公司的产品,是该公司TOPSWitCh系列开关电源集成电路中的一种。该系列集成电路采用TO－220封装,只有三个引出脚,外形…     

Semiconductor laser diode optical amplifiers/gates in photonicpacket switching

In this paper, we will describe how semiconductor laser diode optical amplifiers/gates can be used in the photonic packet switching systems based on wavelength division multiplexed (WDM) techniques. First, we show that cross-gain modulation (XGM) can be suppressed when the device is used in the transparent condition of the waveguide material even when the input signal power exceeds +18 dBm. We then discuss an appropriate encoding for the optical signal. Experimental results show that high bit rate Manchester-encoding enables the use of semiconductor laser diode optical amplifiers/gates in the gain condition as well as the transparent condition. Finally, a new photonic packet receiver which utilizes a semiconductor laser diode optical amplifier as a packet power equalizer is proposed. This receiver accepts 17 dB power fluctuation at nanosecond speed for 10 Gb/s Manchester-encoded signal     

Efficiency enhancement for power amplifiers using dynamic bias switching technique

A dynamic bias switching technique is presented which discretely switches supply voltages according to the signal envelope level. For the detected envelope signals which ate lower than an appropriate threshold, this technique dynamically switches the transistor's drain bias to a significantly lower voltage. For verification, a dynamic bias switching system, applied to a class-AB power amplifier for the 859 MHz band, was implemented. Using a down-link wideband code division multiple access (WCDMA) signal, improved output power of 0.5 dB from 30.5 to 31 dBm, and improved PAE of 8.1% points from 27.4 to 35.5% wete achieved at a given ACLR level of -30 dBc compared to the conventional single-supplied class-AB amplifier.