EMC circuit

Abstract

The invention relates to an EMC circuit which comprises a differential mold filtering circuit and a common mold filtering circuit which are connected in sequence. The common mold filtering circuit comprises a common mold capacitance C1 and a common mold capacitance C2 which are connected in series, wherein the contacts of the common mold capacitance C1 and the common mold capacitance C2 are connected with a grounding wire, and an inductance L is arranged on the grounding wire. The EMC circuit can effectively restrain the influence of the triangular wave in the input current on the conducted interference, not only can meet the requirements for the input current harmonic content limit value of the electronic ballast which is larger than 25W by the national standard GBl7625 1998, but also can meet the requirements for the EMC by the national standard GBl7743 1999, and can meet the requirements for the EMC by the national standard GBl7743 1999 in the middle-frequency band and the high-frequency band.

Description

technical field [0001] The invention relates to an electronic ballast, in particular to an EMC circuit used in an active power factor correction circuit in the electronic ballast, and belongs to the technical field of the electronic ballast. Background technique [0002] The input current in the active power factor circuit is a series of triangular waves with varying frequency, and its spectrum is very rich. To suppress the influence of the triangular wave in the input current on the conduction interference, a complex passive filter circuit must be used. The traditional passive filter circuit is attached as figure 1 As shown, the passive filter circuit includes a differential-mode filter circuit and a common-mode filter circuit, the differential-mode filter circuit includes a differential-mode inductor Ld, a differential-mode capacitor Cd1 and a differential-mode capacitor Cd2, and the common-mode filter circuit includes a common-mode inductor LCl, a common-mode Capacitor C...

AI Technical Summary

Problems solved by technology

[0003] In order to illustrate the effect of the differential mode filter circuit and common mode filter circuit in the filter circuit on suppressing conducted interference, the frequency range 9kHZ to 30MKZ for electronic ballast EMC testing is generally divided into three frequency bands: low, medium and high, namely 9-150kHZ Left and right, 150kHZ-2.0MKZ around, 2.0-30MKZ three bands, for the 9kHz-150kHz low frequency band, it is more effective to use a differential mode filter circuit; for the 150kHz-30MKZ medium and high frequency bands, it is more effective to use a common mode filter circuit, sometimes using a The filtering effect of the first-stage common-mode filter circuit is not good enough, and a two-stage common-mode filter circuit is also used, such as figure 2 As shown, it is difficult for the above traditional filter circuit to meet the requirements for EMC testing in the mid-frequency band and high-frequency band at the same time

In the selection of parameters, it often meets the requirements of the mid-frequency band, but cannot meet the requirements of the high-frequency band, or conversely, meets the requirements of the high-frequency band, but cannot meet the requirements of the mid-frequency band, and it is difficult to take into account the requirements of both aspects.

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