Common mode noise and differential mode noise separator for conductive electromagnetic interference noise

Abstract

The invention discloses a common mode noise and differential mode noise separator used for conductive electromagnetic interfere noise, which comprises a radio-frequency transformer (T) with a centretap and with transformation ratio of 2:1, a common mode choke (L), a differential mode filter capacitor (C) and a double-pole double-throw switch; the separator is characterized in that the differential mode filter capacitor (C) is connected with the primary side of the radio-frequency transformer (T) in parallel, a common mode output is connected at the centretap of the primary side of the radio-frequency transformer (T); secondary sides of the radio-frequency transformer (T) are connected with two output ends of the common mode choke (L) respectively; a differential mode signal is output via an output end of the common mode choke (L), meanwhile, the other end of the common mode choke (L) is grounded and forms a circuit; the double-pole double-throw switch controls the opening and closing of a parallel circuit of the radio-frequency transformer (T) and the differential mode filter capacitor (C) and a coupling loop of the radio-frequency transformer (T) and the common mode choke (L); The double-pole double-throw switch puts through S1 and the common mode is output, which is called a common mode separator. The double-pole double-throw switch puts through S2 and the differential mode is output, which is called a differential mode separator.

Description

technical field [0001] The invention relates to a common-mode noise and differential-mode noise separator for conductive electromagnetic interference noise, and belongs to the technical field of electromagnetic compatibility equipment design. Background technique [0002] EMI filter is one of the most effective means to suppress conducted interference and has been widely used in the industry. However, due to the different mechanisms of conducted noise differential mode interference and common mode interference, the corresponding EMI filter design is divided into two parts: common mode CM filter and differential mode DM filter. Therefore, it can provide accurate separation of common-mode noise and differential-mode noise during noise measurement, which will be effective in designing common-mode CM filters and differential-mode DM filters with excellent filtering performance. The conducted electromagnetic interference measurement system according to international standards us...

AI Technical Summary

Problems solved by technology

However, under high frequency conditions, due to the influence of distribution parameters such as transmission lines, the output of the differential mode signal is not 0 at the midpoint, thereby affecting the output of the common mode end; due to the influence of high frequency stray effects, such as between the primary and secondary sides of the transformer Distributed capacitance will cause modal signal suppression to cause obvious performance degradation, generally 10-20dB attenuation, and some are even more serious, so the performance of the separation network needs to be further improved

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