Several techniques to mitigate conducted electromagnetic interference (EMI) in switch-mode power supplies (SMPS) have been reported in literature. Of these, this paper reviews those techniques that are primarily meant for ac-dc and dc-dc power converters. The techniques are broadly classified based on two criteria-1) reduction of the noise after generation and 2) reduction of the noise at the generation stage itself. A detailed classification and review of various noise mitigation techniques currently available in literature are presented. It is believed that the classification and review of the conducted EMI mitigation techniques presented in this paper would be useful to SMPS researchers and designers.

Conducted EMI Mitigation Techniques for Switch-Mode Power Converters: A Survey

This paper presents a novel ZVZCS full-bridge DC/DC converter, which is able to process and deliver power efficiently over very wide load variations. The proposed DC/DC converter is part of a plug-in AC/DC converter used to charge the traction battery (high voltage battery) in an electric vehicle. The key challenge in this application is operation of the full-bridge converter from absolutely no-load to full-load conditions. In order to confirm reliable operation of the full-bridge converter under such wide load variations, the converter should not only operate with soft-switching from full load to no-load condition with satisfactory efficiency for the full range of operation, but also the voltage across the output diode bridge needs to be clamped to avoid any adverse voltage overshoots arising during turn-OFF of the output diodes as commonly found in regular full bridge converters. In order to achieve such stringent requirements and high reliability, the converter employs a symmetric passive near lossless auxiliary circuit to provide the reactive current for the full-bridge semiconductor switches, which guarantees zero voltage switching at turn-ON times for all load conditions. Moreover the proposed topology is based on a current driven rectifier in order to clamp the voltage of the output diode bridge and also satisfy ZVZCS operation of the converter resulting in superior efficiency for all load conditions. In this paper operation of the converter is presented in detail followed by analytical design procedure. Experimental results provided from a 3KW prototype validate the feasibility and superior performance of the proposed converter.

A Novel ZVZCS Full-Bridge DC/DC Converter Used for Electric Vehicles

This paper presents a novel, yet simple zero-voltage switching (ZVS) interleaved boost power factor correction (PFC) ac/dc converter used to charge the traction battery of an electric vehicle from the utility mains. The proposed opology consists of a passive auxiliary circuit, placed between two phases of the interleaved front-end boost PFC converter, which provides enough current to charge and discharge the MOSFETs' output capacitors during turn-ON times. Therefore, the MOSFETs are turned ON at zero voltage. The proposed converter maintains ZVS for the universal input voltage (85 to 265 Vrms), which includes a very wide range of duty ratios (0.07-1). In addition, the control system optimizes the amount of reactive current required to guarantee ZVS during the line cycle for different load conditions. This optimization is crucial in this application since the converter may work at very light loads for a long period of time. Experimental results from a 3 kW ac/dc converter are presented in the paper to evaluate the performance of the proposed converter. The results show a considerable increase in efficiency and superior performance of the proposed converter compared to the conventional hard-switched interleaved boost PFC converter.

A ZVS Interleaved Boost AC/DC Converter Used in Plug-in Electric Vehicles

The attenuation characteristics of electromagnetic interference (EMI) filters in practice often differ from theoretical predictions and minor changes can result in a significant improvement in performance. The performance of the differential-mode (DM) filter stage can usually be well predicted, but the common mode (CM) behavior is more difficult to handle. This is especially true for three-phase pulsewidth modulation (PWM) rectifier systems, which inherently show a large high-frequency CM voltage at the rectifier output. Possible CM noise current paths of a three-phase/level PWM rectifier are analyzed in this paper where parasitic capacitances to the heat sink and to earth are considered. In addition, a concept to significantly reduce CM emissions is discussed in detail. Based on the proposed models, an EMI filter design for a system with 1 MHz switching frequency is shown. Experimental verification of the designed EMI filter is presented by impedance and conducted emission (CE) measurements taken from a 10 kW prototype. Several practical aspects of filter implementation such as component arrangement, shielding layers, magnetic coupling, etc., are discussed and verified by measurements.

EMI Filter Design for a 1 MHz, 10 kW Three-Phase/Level PWM Rectifier

The design of a single-phase boost power-factor-correction (PFC) circuit is associated with a large variety of considerations, such as the following questions. Which operation mode should be selected (e.g., continuous or discontinuous operation)? How many interleaved boost cells are advantageous? Which switching frequency should be selected? What is the optimum number of EMI input filter stages? Which semiconductor technology should be chosen? All these issues have a significant influence on the converter efficiency and power density. In this paper, the aforementioned questions are addressed for exemplary specifications of the PFC (300-W output power, 400-V output voltage, and 230-V mains voltage), whereby the focus in the design is mainly put on very high power density. As a result, different design points are identified and comparatively evaluated. By considering different aspects such as volume, losses, capacitor lifetime, and also cost issues (e.g., by additional current sensors or expensive silicon carbide devices), a dual-interleaved PFC operated in discontinuous conduction mode at 200 kHz is selected. With an experimental prototype, a superior power density of 5.5 kW/L and a system efficiency of 96.4% are achieved, which is close to the values predicted by the design procedure. Furthermore, measurements verify a near-unity power factor (PF = 99.7%) and the compliance with electromagnetic compatibility conducted noise emission standards. Finally, it is investigated to which extent the power density could be further increased by an integration of the input filter in the PCB.

https://www.hpe.ee.ethz.ch/uploads/tx_ethpublications/04814669_01.pdf

Comprehensive Design and Optimization of a High-Power-Density Single-Phase Boost PFC

Two new planar integrated electromagnetic interference (EMI) filter structures that reduce the filter volume and that are based on standard printed circuit board (PCB) process technology are presented in this paper. First, a passive integrated EMI filter is presented, which results in a volume reduction of 24% compared to the discrete solution. However, this filter requires a planar ferrite core for the common-mode inductor. In order to eliminate the ferrite core and reduce the filter volume further (-40% versus discrete filter), a passive integrated structure is combined with an active EMI filtering circuit. The transfer function, the volume, and the losses of the discrete and the two integrated filters, which are designed for a 600 W power-factor-corrected converter, are compared.

Passive and Active Hybrid Integrated EMI Filters

Two new planar integrated EMI filter structures which reduce the filter volume and which are based on standard PCB process technology are presented in this paper. First, a passive integrated EMI filter is presented, which results in a volume reduction of 25% compared to the discrete solution. However, this filter requires a planar ferrite core for the CM inductor. In order to eliminate the ferrite core and reduce the filter volume further (-40% vs. discrete filter) a passive integrated structure is combined with an active EMI filtering circuit. The transfer function, the volume and the losses of the discrete and the two integrated filters, which are designed for a 600W PFC converter, are compared.

https://www.hpe.ee.ethz.ch/uploads/tx_ethpublications/04909406_01.pdf

A. Wirthmueller

Papers

Passive and Active Hybrid Integrated EMI Filters

Passive and active hybrid integrated EMI filters