DC Adapter, Power Supply From China, UK EMC Testing

Does Your DC Power Supply Purchased From China Comply With UK EMC Testing Standards?

Many UK companies are purchasing power adapters from China thinking that they are compliant to the relevant UK EMC testing standards. There is one big problem however and this is that many of these power supplies, laptop adapters etc. are copies / fakes. Granted, not all power supplies purchased from China are fake, however a large percentage are and it is extremely difficult to identify a fake from appearance alone, as even the labels look genuine.

DC power supplyIn order to reduce cost many power supply manufactures miss out critical filter components. In this case the power supply will still function however it is likely that it will not pass EMC regulations.

What Should You Do?

Before committing to purchase a large amount of power supplies / laptop adapters we would strongly recommend that you request samples first and then have them EMC tested. Usually conduced emissions testing will quickly identify a fake power supply. We would also recommend that you request copies of any test data that may be available so this can be verified when the power supply is tested.

Conducted Emissions Testing

Your device creates electromagnetic energy and a certain portion of it will be conducted onto the power supply cord. In order to restrict the amount of interference your device can couple back onto a power supply, it is necessary to measure these emissions (usually from 150 kHz – 30 MHz, and verify that they comply with specified limits. This helps to ensure that the local power supply remains relatively ‘clean’ and nearby devices won’t be affected by your device.

HMS-X Spectrum AnalyzerConclusion

Once you have placed that order for a large quantity of power supplies / adapters it is usually not cost effective to return them due to the shipping cost. So we would strongly recommend that you minimise risks and have your products tested before you place that production order!


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