外文出处：Farhadi, A. (2008). Modeling, simulation, and reduction of conducted electromagnetic interference due to a pwm buck type switching power supply. Harmonics and Quality of Power, 2008. ICHQP 2008. 13th International Conference on, 1 - 6.
Modeling, Simulation, and Reduction of Conducted Electromagnetic Interference Due to a PWM Buck Type Switching Power Supply I
A. Farhadi
Abstract:Undesired generation of radiated or conducted energy in electrical systems is called Electromagnetic Interference (EMI). High speed switching frequency in power electronics converters especially in switching power supplies improves efficiency but leads to EMI. Different kind of conducted interference, EMI regulations and conducted EMI measurement are introduced in this paper. Compliancy with national or international regulation is called Electromagnetic Compatibility (EMC). Power electronic systems producers must regard EMC. Modeling and simulation is the first step of EMC evaluation. EMI simulation results due to a PWM Buck type switching power supply are presented in this paper. To improve EMC, some techniques are introduced and their effectiveness proved by simulation. Index Terms:Conducted, EMC, EMI, LISN, Switching Supply I. INTRODUCTION
FAST semiconductors make it possible to have high speed and high frequency switching in power electronics
?1?. High speed switching causes weight and volume reduction of equipment,
?2?but some unwanted effects such as radio frequency interference appeared . Compliance with
electromagnetic compatibility (EMC) regulations is necessary for producers to present their products to the markets. It is important to take EMC aspects already in design phase
?3?.
Modeling and simulation is the most effective tool to analyze EMC consideration before developing the products. A lot of the previous studies concerned the low frequency analysis of power electronics components
?4??5?. Different types of power electronics converters are capable
to be considered as source of EMI. They could propagate the EMI in both radiated and conducted forms. Line Impedance Stabilization Network (LISN) is required for measurement and calculation of conducted interference level the EMC evaluation criterion
?6?. Interference spectrum at the output of LISN is introduced as . National or international regulations are the references for
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?7??8?
the evaluation of equipment in point of view of EMC ?7??8?. II. SOURCE, PATH AND VICTIM OF EMI
Undesired voltage or current is called interference and their cause is called interference source. In this paper a high-speed switching power supply is the source of interference.
Interference propagated by radiation in area around of an interference source or by conduction through common cabling or wiring connections. In this study conducted emission is considered only. Equipment such as computers, receivers, amplifiers, industrial controllers, etc that are exposed to interference corruption are called victims. The common connections of elements, source lines and cabling provide paths for conducted noise or interference. Electromagnetic conducted interference has two components as differential mode and common mode
?9?.
A. Differential mode conducted interference
This mode is related to the noise that is imposed between different lines of a test circuit by a noise source. Related current path is shown in Fig. 1
?9?. The interference source, path
impedances, differential mode current and load impedance are also shown in Fig. 1. B. Common mode conducted interference
Common mode noise or interference could appear and impose between the lines, cables or connections and common ground. Any leakage current between load and common ground could
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be modeled by interference voltage source.
Fig. 2 demonstrates the common mode interference source, common mode currents II
cm1
and
cm2
and the related current paths?9?. The power electronics converters perform as noise source
between lines of the supply network. In this study differential mode of conducted interference is particularly important and discussion will be continued considering this mode only.
III. ELECTROMAGNETIC COMPATIBILITY REGULATIONS
Application of electrical equipment especially static power electronic converters in different equipment is increasing more and more. As mentioned before, power electronics converters are considered as an important source of electromagnetic interference and have corrupting effects on the electric networks
?2?. High level of pollution resulting from various disturbances reduces the
quality of power in electric networks. On the other side some residential, commercial and especially medical consumers are so sensitive to power system disturbances including voltage and frequency variations. The best solution to reduce corruption and improve power quality is complying national or international EMC regulations. CISPR, IEC, FCC and VDE are among the most famous organizations from Europe, USA and Germany who are responsible for determining and publishing the most important EMC regulations. IEC and VDE requirement and limitations on conducted emission are shown in Fig. 3 and Fig. 4
?7??9? .
For different groups of consumers different classes of regulations could be complied. Class A
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for common consumers and class B with more hard limitations for special consumers are separated in Fig. 3 and Fig. 4. Frequency range of limitation is different for IEC and VDE that are 150 kHz up to 30 MHz and 10 kHz up to 30 MHz respectively. Compliance of regulations is evaluated by comparison of measured or calculated conducted interference level in the mentioned frequency range with the stated requirements in regulations. In united European community compliance of regulation is mandatory and products must have certified label to show covering of requirements
?8?.
IV. ELECTROMAGNETIC CONDUCTED INTERFERENCE MEASUREMENT A. Line Impedance Stabilization Network (LISN)
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1-Providing a low impedance path to transfer power from source to power electronics converter and load.
2-Providing a low impedance path from interference source, here power electronics converter, to measurement port.
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