AN1714 datasheet(5/46 Pages) STMICROELECTRONICS

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AN1714

Powerline communication

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Powerline communication

Although the concepts of power line communication and home automation, as well as the

development of different devices dedicated for power line communication, have been

present for several years, the market segment for this kind of application has only recently

been growing.

The three main factors that have contributed up to now to the field of the powerline

communication are:

The slow development of international norms and standards

Some technical constraints related to the electrical network

General consideration of costs

The first point concerns standards and norms. A general consideration in an open

communication system is to have mandatory rules and guidelines to guarantee that every

node, whatever the manufacturer, does not compromise the characteristics of the entire

network and the performance of the communication system.

For residential products this aspect is quite relevant considering the presence of many

different appliances and manufacturers, and also the concern for a common language (the

protocol) which is mandatory.

In 2002 the CENELEC (European Committee for Electrotechnical Standardizations)

published or updated a series of regulations about communication on low-voltage electrical

installations. We refer in particular to the EN50065-1, concerning general requirements,

frequency bands and electromagnetic disturbances; the EN50065-4-2 about the low-voltage

decoupling filter and safety requirements; and the EN50065-7 about the impedance of the

devices.

A preliminary version (1999) of the EN50065-2-1 about immunity requirements is also

available.

There has been a certain alignment among the appliance manufacturers on the EHS

(European Home System) protocols, even if a lot of customized protocols are present,

mainly in proprietary mains. More information on EHS protocol is available in the EHS

booklet.

The second critical consideration concerns the technical problems regarding the specific

topology of the electrical network.

Figure 2 shows what happens to a signal transmitted on an electrical network. For several

reasons that are listed in the next paragraph (low impedance, different kind of disturbances,

etc.) the received FSK signal has a very low level and it is mixed with a great level of noise.

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