正态频率调制降低开关变换器电磁干扰的研究

利用正态频率调制技术从噪声产生源头上降低了开关变换器的电磁干扰。简单地分析了具有不变概率密度分布的离散随机信号频率调制降低开关变换器EMI噪声的原理,并试制了一台正态频率调制开关变换器电源样机。给出了开关管电流信号的频谱以及传导干扰测试的结果。实验结果表明该技术能有效降低开关谐波峰值,使开关变换器易于通过EMI测试,具有应用的前景。     

频率调制抑制DC／DC变换器EMI的研究

开关电源是采用高速半导体器件来进行电能转换的,开关切换过程中产生的电压电流尖峰造成了严重的EMI问题。常规的DC／DC变换器工作在频率固定的PWM模式下,频谱是离散的,开关频率和低次谐波的能量尖峰很高。文章研究了频率调制技术抑制DC／DC变换器EMI噪声的效果,通过对一台Boost变换器样机进行周期频率调制,证明了频率调制技术对抑制DC／DC变换器EMI的有效性。     

Reduction of power converter EMI emission using soft-switchingtechnique

Measurements of conducted and radiated electromagnetic interference (EMI) emission from hard-switched and soft-switched buck, boost, and flyback converters of similar power ratings are presented. Results indicate that EMI emission can be substantially reduced by using a soft-switching technique in power converters. Thus, the soft-switching technique provides a practical and useful solution to reduce EMI emission from switched-mode power circuits. A comparison of EMI emission on the three classes of converters is also included. The flyback converter is found to be the least EMC friendly among the converters tested     

随机频率调制降低开关变换器电磁干扰的研究

利用随机频率调制技术从噪声产生源头上降低了开关变换器的电磁干扰。分析了具有不变概率密度分布的随机频率调制降低开关变换器EMI噪声的原理。将嵌入式系统产生的均匀分布离散随机信号加入脉宽调制芯片,开关频率随机变化,试制了一台随机频率调制开关变换器电源样机。给出了开关管电流信号的频谱以及传导干扰测试的结果。实验结果表明该技术能有效降低开关谐波峰值,使开关变换器易于通过EMI测试,具有应用前景。     

手持式导航仪电源EMI设计

由于地面GPS信号非常微弱(EIPR约为-130 dBm),机内电磁干扰(EMI)对手持式GPS导航仪接收性能的影响非常大.在以手持式导航产品为研究对象,分析其电磁干扰产生的原因时,我们发现手持导航仪各电源模块良好的EMI设计至为关键.掌握电源EMI设计的基本原理,合理布局各电源模块,即能有效降低机内EMI干扰,提高整机GPS接收性能.     

Conducted EMI Reduction in Power Converters by Means of Periodic Switching Frequency Modulation

Spread spectrum clock generation techniques were originally developed to reduce electromagnetic interference (EMI) in communications and microprocessor systems working in the range of hundreds of megahertz. Nowadays, the switching frequency of power converters has been increasing up to values that make worthy the application of such switching frequency modulation techniques to reduce EMI emissions in power converters. Although random modulations have been applied before to power converters, periodic patterns can provide some advantages. First, theoretical principles of frequency modulation using three periodic patterns for the modulating function are presented. The influence of some important modulation parameters on the EMI reduction is analyzed and some considerations about the EMI filters design are also presented. The effectiveness of such methods in terms of EMI reduction is demonstrated theoretically and confirmed with experimental results obtained from tests carried out on two converters. The first one is a 2.5 W buck converter that can be switched up to 1 MHz and the second one is a 600 W boost converter switching at 40 kHz. In both cases, attenuations obtained in conducted EMI are evaluated. Finally, special attention has been paid to input current and output voltage ripple in order to evaluate possible undesired side-effects produced by this technique.     

正弦频率调制降低开关电源传导EMI的实验研究

利用正弦频率调制技术从噪声产生源头上降低了开关电源传导电磁干扰,简单地分析了正弦混沌频率调制降低EMI噪声的原理,并试制了一台正弦频率调制反激变换器电源样机,给出了开关管电流信号的频谱以及传导干扰测试的结果。实验结果表明该技术能有效降低开关谐波峰值,具有应用的前景。     

Input filter design for power factor correction circuits

The issues involved in the design of power factor correction circuit input filters are significantly different from those involved in the design of input filters for DC-DC power converters. In many cases, the EMI and power factor requirements are impossible to meet using the existing filtering technology. This paper proposes the use of high-order elliptic filters to achieve the required EMI attenuation and power factor. The new input filter technology provides a significant filter size reduction over the standard filter designs, minimizes the filter-power converter interaction, and maintains a good converter power factor. New active and passive filter damping methods that guarantee optimal filter pole damping, while virtually eliminating damping resistor power dissipation, are proposed. The filter design procedure that makes possible a simple and fast design of filters with an arbitrary number of stages is also presented     

A family of low EMI unity power factor converters

A new family of soft-switching unity power factor converters with high input power factor and isolated output is presented. A feature of the converters is a significant reduction of conducted electromagnetic interference (EMI). Six converter topologies have been identified that share a zero-voltage-switching (ZVS) phase arm on the input boost converter stage. Detailed analysis and experimental results are presented on the double ZVS phase-arm resonant transition converter     

抗电磁干扰设计探讨

本文对变频器、逆变器等电气产品中抗电磁干扰设计进行了深入地讨论,结合实践,提出硬、软件抗干扰措施,实践证明这些措施对其他电子产品同样可以获得很好的电磁兼容效果。     

Research on periodic switching frequency modulation for conducted EMI suppressing in power converter

This paper is devoted to explore modulation techniques with deterministic profiles reducing the peak EMI in a power converter. In this paper, the effect of primary modulation parameters such as modulation profile, modulation index and modulation frequency on peak EMI suppression is numerically simulated and discussed while a fully integrated spread spectrum clock generator (SSCG) with triangular modulation is presented whose major advantages are good robustness, small size and low-power consumption. The proposed SSCG has been applied to a fly-back switching converter and the results of the experiment confirm the proposed circuit.     

消磁电源电磁干扰补偿技术

舰船临时线圈消磁是消除舰艇固定磁场，提高舰艇反磁探反磁性武器能力的重要措施。由于消磁工艺的特殊性，对于挂接于电网输出大功率电流脉冲的消磁电源有可能给电网造成极大的电磁污染，导致电网电压畸变。本文从探讨电网电压畸变的成因出发，着重研究了电压畸变的补偿问题，以期改善消磁电源的电磁兼容性能。     

Analysis of a ripple-free input-current boost converter withdiscontinuous conduction characteristics

Coupled inductor techniques supply a method to reduce the power converter size and weight and achieve ripple-free current. The boost power converter is a very popular topology in industry. However, the input-current ripple hinders efforts to meet electromagnetic interference (EMI) requirements. In particular, the input current becomes discontinuous and pulsating when the conventional boost power converter operates in the discontinuous inductor-current mode. This paper describes a boost power converter which has the same discontinuous properties as the conventional boost power converter. However, the proposed boost topology has continuous or ripple-free input current when it operates with discontinuous inductor-current. The proposed topology is compared with traditional converter topologies, such as the Sepic and Cuk power converters. Simulation results are presented. The prototype is built to demonstrate the theoretical prediction. The proposed boost topology is simple, with straightforward control [the same as pulse-width modulation (PWM)]     

Use of sigma-delta modulation to control EMI from switch-mode powersupplies

Conducted electromagnetic interference (EMI) is a major cause of concern in switch-mode power supplies (SMPSs) which commonly use standard pulsewidth modulation (PWM). In this paper, sigma-delta (ΣΔ) modulation is proposed as an alternative switching technique to reduce conducted EMI from an SMPS. The result of using ΣΔ modulation is a spread in the spectrum of the conducted emissions so that large concentrations of power at discrete frequencies are avoided. Experimental time-domain waveforms and spectra of the switching function of first-order and second-order ΣΔ modulators are presented to prove the viability of the scheme for EMI mitigation. These modulators are then applied to a DC-DC converter in an off-the-shelf computer power supply and experimental results show a reduction of roughly 5-10 dB·μV in EMI emissions over standard PWM modulators     

A Systematic Topology Evaluation Methodology for High-Density Three-Phase PWM AC-AC Converters

This paper presents a systematic evaluation approach of three-phase pulsewidth-modulated (PWM) ac–ac converter topologies for high-density applications. All major components and subsystems in a converter are considered and the interdependence of all the constraints and design parameters is systematically studied. The key design parameters, including switching frequency, modulation scheme, and passive values, are selected by considering their impacts on loss, harmonics, electromagnetic interference (EMI), control dynamics and stability, and protection. The component selection criteria as well as the physical design procedures are developed from the high-density standpoint. The concept of using the same inductor for harmonic suppression and EMI filtering is introduced in the design. With the proposed methodology, four converter topologies, a back-to-back voltage source converter (BTB-VSC), a nonregenerative three-level boost (Vienna-type) rectifier plus voltage source inverter (NTR-VSI), a back-to-back current source converter (BTB-CSC), and a 12-switch matrix converter, are analyzed and compared for high specific power using SiC devices. The evaluation results show that with the conditions specified in this paper, BTB-VSC and NTR-VSI have considerably lower loss, resulting in higher specific power than BTB-CSC and the matrix converter. The proposed methodology can be applied to other topologies with different comparison metrics and can be a useful tool for high-density topology selection.      

SiC power diodes provide breakthrough performance for a wide rangeof applications

The electrical performance of silicon carbide (SiC) power diodes is evaluated and compared to that of commercially available silicon (Si) diodes in the voltage range from 600 V through 5000 V. The comparisons include the on-state characteristics, the reverse recovery characteristics, and power converter efficiency and electromagnetic interference (EMI). It is shown that a newly developed 1500-V SiC merged PiN Schottky (MPS) diode has significant performance advantages over Si diodes optimized for various voltages in the range of 600 V through 1500 V. It is also shown that a newly developed 5000 V SiC PiN diode has significant performance advantages over Si diodes optimized for various voltages in the range of 2000 V through 5000 V. In a test case power converter, replacing the best 600 V Si diodes available with the 1500 V SiC MPS diode results in an increase of power supply efficiency from 82% to 88% for switching at 186 kHz, and a reduction in EMI emissions     

互感滤波器在全桥移相软开关变换器中的应用

开关电源纹波的产生是必然的,因此带来了EM I问题。文中介绍了互感滤波的原理,并把互感应用在全桥移相ZVZCS-PWM变换器中,理论分析了其可行性,最后仿真验证了理论分析结果。     

PFC full bridge rectifiers EMI modeling and analysis-common mode disturbance reduction

Switched mode power supplies must comply with electro-magnetic interference (EMI) regulations. Due to technological improvements, switching frequencies have been increased leading to reduced passive component values but also greater EMI levels, especially conducted common mode disturbances. This paper presents a simple and effective EMI forecast method to study and to analyze the conducted EMI effects before prototype testing. The methodology is validated and applied to the single phase full bridge power factor correction (PFC) rectifier. Several techniques to reduce common mode current (CMC) levels created by the converter are presented. The study is based on high frequency models and understanding of phenomenon. Looking at the control strategies and/or the propagation paths, it is demonstrated that EMI levels may be reduced. It is shown that with symmetrical EMI propagation paths, synchronized control strategies such as bipolar pulse width modulation (PWM) are preferred and lead to reduced CMC levels. On the other hand, with asymmetrical propagation paths, unipolar and half bridge control strategies may be preferred to reduce both differential mode current (DMC) and CMC levels. Results are validated using practical experiments performed under EMI regulation testing conditions.     

一种新型单管软开关Boost变换器及其EMI研究

分析了一种用于传统Boost变换器的软开关方案。电路中只使用了一个开关管以及最少的元件，但却获得了开关器件零电流开通和零电压关断的效果。文中通过仿真描述了这一电路的运行特点，同时还分析了其与传统硬开关Boost电路的EMI状况差异以及门控电路对该变换器EMI状况的改善效果。     

EMI reduction in switched power converters using frequency Modulation techniques

Frequency-modulation techniques have been used to reduce electromagnetic interference (EMI) produced by the clock of digital systems working in the range of hundreds of megahertz. The working principle consists of modulating the original constant clock frequency in order to spread the energy of each single harmonic into a certain frequency band, thus reducing the peak amplitude of EMI at harmonic frequencies. Nowadays, the switching frequency of power converters has increased up to values that make interesting the application of such techniques to reduce EMI emissions due to switching of power circuits. This paper presents the theoretical principles of frequency modulation using deterministic profiles for the modulating function. It shows the effectiveness of such methods in terms of EMI reduction for different modulation profiles and other parameters. The method is compared with other methods using random modulation. Tests carried out on a buck converter are presented for experimental validation of the method. A short discussion on optimal modulation profiles and parameters is also included.