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DM filter for multi input converters Disclosure Number: IPCOM000243629D
Publication Date: 2015-Oct-07
Document File: 2 page(s) / 285K

Publishing Venue

The Prior Art Database

Related People

Sauro Macerini: AUTHOR

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In a power converter where multiple independent inputs are presents (i.e. solar inverter) there are usually several switching converters, one for each of the inputs with a common return line.

The switching noise generated by the converters is usually filtered to comply with noise emission standards. It is a normal practice to filter the Differential-Mode current by means of L-C filters as shown in Fig.1, where a filter inductor is connected in series with each individual input line.

DM filter for multi-input converters

Fig. 1

In order to simplify the circuitry, in place of a plurality of inductors - one for each channel - it is possible to use a single inductor connected in series with the Common Return line as shown in Fig. 2

The wire shall be sized in order to carry the overall amount of current, that is the sum af all the input currents. A greater advange comes from the use of interleaved PWM control signals in the power converters, by properly shifting these signals in phase.

By means of this technique, the noise carrier frequency will be higher; in particular:

Fnoise = n x Fsw, where Fsw is the switching frequency and n is the number of interleaved inputs.

This means that two inputs interleaved will generate noise at double of the frequency of each single converter, allowing a reduction of the inductance value which is inversely proportional to the frequency.

© ABB Group October 2015

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Fig. 2

© ABB Group October 2015