EMI reduction by means of switching frequency modulation with variable delay in power supplies

Abstract

In this article, a new model to predict the amplitude reduction of the interference harmonics in power supplies with parallel topology is presented when the switching frequency modulation with variable delay (VDFM) technique is applied. The VDFM method consists of combining the interleaving and switching frequency modulation (SFM) techniques. The new model presented has been evaluated in a multichannel buck converter, operating with different numbers of converters when a triangular modulation profile is used. Theoretical study and experimental results show the influence of the number of converters and the modulation parameters with regard to electromagnetic interference reduction. From the new model presented, it is possible to predict the value of modulation parameters and the numbers of converters in order to satisfy the required attenuation regarding the electromagnetic compatibility directives, when a triangular modulation profile is used.

Efficient reduction of EMI from massage and its improvement

“…In order to quickly find EM disturbance source, on one hand, keeping the power supply and transformer units work, only make one of the units work independent of other units one by one. Finally, after repeatedly online test and analysis, the power supply unit, transformer unit and indicator unit are considered as serious power disturbance sources, the specific explanations are: (1) Voltage drop and variation ( / du dt ) will cause the emission of EM field and lead to EM disturbance of power exceeding the limit line [5]; (2) Once MOS switch circuit of indicator unit works, current changes ( / di dt ) to result in EM disturbance power emission. Solving the problem of excessive power disturbance generally applies to filtering technology.…”

“…E-mail addresses: sxrfreeman@126.com (X. Shi). M a n u s c r i p t space, it's usual to use filter to reduce EM disturbance from massage [3,4,5]. So, how to weaken and reduce the EMI from electronic circuit units is very critical to promote massage design.…”

Design and implementation of a compact frequency synchronisation control circuit using enable input for DC–DC converter

“…From (8), in order to make SYNC high for the synchronisation external clock, signal C and E must be low. Therefore the period T EN of external clock in EN pin must be shorter than T 2 and longer than T 3 according to (5) and (7).…”

“…Frequency synchronisation can be used to operate the DC-DC converter outside a critical signal frequency band of an application [7]. The spread frequency modulation technique [8][9][10] can be taken to reduce EMI by input varying external synchronous clock control signal. In a multi-power system, frequency synchronisation can also be used to synchronise multiple DC-DC switching converters to the same frequency to reduce EMI and simplify filtering design [7].…”

Effects of nonidealities in switching frequency modulation techniques: Application to coupled interleaved multicellular parallel converters

“…Recently, the Variable Delay with switching Frequency Modulation (VDFM) has been presented [1][2][3]. This technique, which combines interleaving with frequency modulation, is specially intended for converters in parallel topology and shows good results in terms of conducted disturbances attenuation [4].…”