Most buyers treat certification as paperwork that arrives with the shipment. In practice it is a project with its own critical path, and if it starts late it is the only thing standing between a finished production run and a container that cannot legally be sold. Here is what actually happens, in order.
Week 0-1: scope and pre-scan
The first step is deciding which standards apply. For an external power supply sold into the EU that means the safety standard for the product class plus EMC for the switching supply, RoHS for restricted substances, and a technical file that has to exist if a market surveillance authority asks. In the US it means FCC Part 15 Subpart B for EMC and a safety report to the applicable standard, usually requested by retailers even where it is not a legal condition of sale.
A pre-scan runs the unit on the bench before the lab sees it. It is cheap, it takes a day, and it catches the two things that fail most often: conducted emissions at the switching frequency and its harmonics, and a temperature rise above the limit inside a small GaN enclosure.
Week 2-3: sample selection and worst-case build
The lab does not test a sample from the office shelf; it tests a unit from the production configuration, and usually the worst case rather than the average. For a multi-port charger that means the highest-power port combination and the highest ambient temperature the product is rated for. If the programme has several plug variants, the plug mechanism is part of the tested configuration, so the variant list is fixed before the lab booking rather than after.
Week 3-6: the test itself
EMC testing typically takes two to four days including the re-test that follows any failed line. Safety testing runs longer because it includes abnormal-condition tests — short circuit, overload, component failure simulation — and those need a unit to be pushed until it protects itself. Temperature rise is measured under sustained load, which is why a charger that looks fine on a bench for ten minutes can still fail at hour two.
Week 6-8: reports, marking and the technical file
Reports come back with the measured data and a statement of conformity. The CE marking, the responsible party for FCC, and the declaration of conformity are prepared from those reports. The technical file — schematics, bill of materials, layout, test data, marking drawings — is assembled and kept available; it is not submitted anywhere, but it is what a regulator would ask for.
What changes when you put your own brand on it
This is where programmes get stuck. A logo, a colour or a finish does not touch the safety-critical parts, so the existing reports for the platform remain valid and the branded version is a documentation update. A new enclosure, a different port layout or a different plug mechanism does touch them, and the affected tests are repeated. Knowing which of the two you are doing before the order is placed is the difference between a two-week paperwork step and a two-month project.
The calendar a buyer should ask for
Ask for five dates in writing: pre-scan complete, sample released to the lab, EMC complete, safety complete, reports issued. Add the certification lead time to the production lead time before you promise anything to your own customer — and if the platform is already certified for your market, ask for the existing reports first, because that single question can remove six weeks from the plan. Our team lists the certificates on file per market on request, before any order is placed.