[Design Application]
Unscramble The European Power Directives
While The New Standards Facilitate Trade Within Europe, They Perplex The Many Foreign Companies Targeting That Market
By implementing harmonized standards that remove the barriers to free movement of electronic products, the European Union (EU) is rapidly realizing its goal of creating a single market. This unified market eliminates the confusion and cost associated with multiple local laws and standards. This move could potentially simplify the technical and commercial task of creating products for Europe, and make it easier to use products from any country in Europe.
The result is a major opportunity, but it does demand that designers be at least familiar with a completely new set of rules. The good news is that these rules have been written as a coherent set, building on national experiences gained over a number of years. However, the sheer volume of material, and the labeling system employed, can be confusing. In the context of power supplies, approximately 116 standards and amendments govern EMC alone. Of all the standards and recommendations, nowhere is the hierarchical structure of European standards clearer, but the application more open to interpretation, than in the CE mark.
The Basic Nomenclature Before we get too deeply into the topic, it may help to clarify a few terms:
Directive: The name given to an official EU document that defines the requirements.
Apparatus: A finished product delivering an intrinsic function, and directly usable by the end user.
CE Marking (93/68/EEC): Products subject to Directives must comply with those Directives, and be marked in a prescribed way with the CE logo to be legally offered for sale in any EU state.
Competent body: A body recognized as fulfilling the criteria of Annex II of the EMC Directive, and responsible for issuing reports or certificates under Article 10.2 of that Directive.
Notified body: A body specially defined to the European Commission by a member state as having responsibility for issuing EC-type examination certificates for radio communications equipment under Article 10.5 of the EMC Directive. The body is also required to match the criteria of Annex II of that Directive.
Compliance: Unlike approval systems like UL, which always require testing, there are several ways to justify a claim of compliance with a Directive.
EMC Directive (89/336/EEC amended 92/31/EEC): The EU specification for EMC emission and susceptibility (see Table 1).
Low-Voltage Directive (LVD) (73/23/EEC): Safety requirements for equipment normally operating at from 50 to1000 V ac or 75 to 1500 V dc (see Table 1, again).
New Approach: A set of Directives intended to harmonize product safety throughout the EU.
Equipment meant for distribution or use in any European Union country must comply with the applicable directives. The directives lay down equipment requirements, and leave it to the standards, primarily European harmonized standards, to define the technical requirements. The manufacturer, or its European representative, must ensure that the product complies with applicable directives and CE mark the product.
Note that the CE mark does not claim conformance with a particular standard. A plastic toy duck and a TV set will both need the CE mark, although they meet totally different standards (toy safety was, in fact, the subject of one of the early directives).
Power-supply designers and users must consider the EMC Directive, LVD, and CE-marking amendment together, remembering that since Jan. 1, 1997, it is mandatory to CE mark under the LVD if the directive is applicable (Table 2).
Even within Europe itself, there has been significant discussion about when a subassembly such as a power supply needs CE marking. Some guidelines have been established by the European Power Supply Manufacturers Association (EPSMA). A web site provides access to these recommendations, but they are summarized below (see Table 3).
All line-powered power-supply units fall within the LVD, and the EMC Directive applies to all standalone units. Thus both types of devices required the CE mark. Provided that their input and output are not within the voltage range of the LVD, dc-to-dc converters do not fall under the LVD regulations, so all that's left is the EMC Directive.
The basic requirement of the EMC Directive is that electrical equipment may not cause a disturbance, or be affected by reasonable disturbance levels in its environment. The directive covers radiated and conducted emissions, RF electromagnetic susceptibility, electrostatic discharge, and fast transients.
The guidelines to the Directive state that components performing no direct function, such as components of electrical or electronic circuits, shall not be CE marked, as the EMC Directive does not apply to them. This matches practical experience because the EMC performance will depend on the details of the components' installation in the final equipment. Although a recent revision of the guidelines modified the list of specified components having no direct function, and omitted the explicit reference to "power supplies intended to be incorporated in apparatus," the EPSMA recommends that the EMC Directive, and therefore the CE marking, is still not relevant to component power supplies such as dc-to-dc modules.
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