Switching power supplies, as their name suggests, are electronic devices based on energy conversion by means of high-frequency pulses. Therefore, they can be and always are a source of electromagnetic disturbances, which in turn may be harmful to other devices connected to the same local power network—in that case we speak of conducted disturbances. They may also be harmful from the point of view of disturbances propagating by means of electromagnetic waves—in that case we speak of radiated disturbances.
Nowadays, the number of devices capable of generating disturbances or being susceptible to disturbances has become so great that it was necessary to regulate this issue. Otherwise, for example, we would not be able to use mobile telephony or other benefits of modern technology. These regulations are the standards responsible for the so-called Electromagnetic Compatibility, commonly abbreviated as EMC (Electromagnetic Compatibility). In Poland, compliance with these standards is supervised by the Office of Electronic Communications (Urząd Komunikacji Elektronicznej – UKE), which lists among its five principal tasks: “Monitoring compliance with electromagnetic compatibility requirements.” As part of the responsibilities of this authority, teams and laboratories operate. Inspectors also work on behalf of the Office, possessing extensive powers to carry out inspections and impose measures ranging from recommendations to less or more severe penalties for failure to comply with EMC standards.
The Market – Customs – The Language of Jargon
Currently, there are many suppliers of private-label switching power supplies on the Polish market, and more broadly on the European market. Their products are based both on their own manufacturing and on outsourced production, while many simultaneously pursue different business strategies, including the rebranding of products manufactured by other companies. Regardless of the individual strategy adopted by each company, it should be clearly stated that all of them are subject to the same EMC regulations and should comply with them. Competition is extremely strong, which benefits end users by allowing them to enjoy attractive retail prices. However, there is no shortage of power supplies on the market that do not comply with EMC standards. Naturally, these are cheaper devices because they lack a number of components responsible, generally speaking, for filtering and suppressing electromagnetic disturbances. In such situations, inspectors of the Office of Electronic Communications intervene. They act both as a result of their own inspections and investigations, and as a result of reports submitted by customers or even by competing companies.
The use of industry jargon to achieve commercial objectives is also common on the market. As an example, let us consider two definitions:
- Power supply for industrial applications.
- Power supply for domestic applications.
These are two seemingly innocent definitions which, in the Polish language, are generally interpreted in exactly the opposite way to what their permissible electromagnetic disturbance limits actually imply. For most people, the word “industrial” is synonymous with high durability, high reliability and, generally speaking, a higher class in every respect. The word “domestic”, when compared with the word “industrial,” is usually interpreted as meaning something of lower importance. Why do we look at it this way? Probably because anything associated with industry is linked to significant financial responsibility. In the context of power supplies, we naturally think about the cost of production downtime resulting from a failure—for example, the failure of a power supply. For this reason, power supplies intended for industrial applications appear to be the better products. And this is precisely where EMC presents a surprise. The permissible electromagnetic disturbance levels for industrial power supplies are actually higher than those permitted for power supplies intended for domestic applications. Therefore, it should not be surprising that power supplies classified for domestic applications are often more expensive than those intended for industrial use. On the other hand, many of us would probably be pleased to learn that the power supply we intend to install in a domestic installation is described as being “for industrial applications.” From the EMC point of view, however, this would be a mistake. The Office of Electronic Communications is capable of detecting such situations at a relatively early stage—for example, when a company offers complete sets consisting of a power supply together with furniture lighting or other lighting products intended for domestic use.
Import of Power Supplies
It will not reveal any secret if we honestly admit that the majority of switching power supplies available on the European market were manufactured somewhere in the Far East, where their manufacturers do not necessarily strive to meet all the requirements of European standards. Importers receive from manufacturers a number of documents—declarations, test reports, and whatever else we might expect.
Let us not deceive ourselves, however, into believing that such documents are a guarantee of credibility. Quite the opposite. They are insignificant compared with one important fact—namely, that the entity responsible for failure to comply with EMC standards is the one placing the device on the European market. No document originating from the Far East will constitute any valid defence if the power supply fails to meet EMC requirements, nor will it protect against possible sanctions imposed by the Office of Electronic Communications (UKE).
Are There Power Supplies on the Market That Do Not Comply with EMC? Of course there are. There are importers willing to take the risk, competing primarily on price. There are also power supplies purchased individually, yet on a large scale, directly from the Far East through popular Asian online marketplaces.
This material—in fact, this article—is being prepared at Breve, a company whose product portfolio includes a wide range of switching power supplies. Within our company, we carried out a simple experiment. We purchased a low-cost switching power supply delivered directly from the Far East at the remarkably low price of only a few Polish zlotys, including shipping. We then performed EMC testing on this unit. For comparison, we carried out the same tests on a Breve power supply with identical electrical ratings, selected at random from our warehouse.
The Results:
Power Supply Purchased from an Asian Online Marketplace:
Exceeded permissible levels of conducted and radiated emissions – pink and green traces. Permissible limits – red and blue traces.
Equivalent Breve Power Supply:
Breve Laboratory
As a company specializing in switching power supplies, Breve has, through its own experience, established an EMC laboratory equipped with the latest state-of-the-art measurement instruments. At present, we perform EMC testing for our own purposes on every individual batch of power supplies in order to ensure that the requirements of the applicable standards are met. Our laboratory equipment offers significantly broader capabilities. Therefore, it is worth mentioning that we can also provide EMC testing services for electronic equipment entrusted to us by external customers.
We invite you to take advantage of our range of switching power supplies.
M.Sc. Eng. Krzysztof Majewski
