Sourcing wall chargers and GaN adapters

Isolation and separation. The distance and barriers between the mains-voltage side and the output side are what stand between a user and a fault. Creepage and clearance distances, the transformer's construction and insulation, and the physical layout of the board are the parts of a charger that a price cut attacks first because they are invisible.

Enclosure. Material and flame rating, wall thickness, whether the case is ultrasonically welded or glued, and whether it can be opened without destroying it. A charger that pops apart in a drop test is a mains product with exposed internals.

Protection behaviour. Over-voltage, over-current, short-circuit, over-temperature and what the charger does when it hits each of them — recover, latch off, or continue. Ask what the thresholds are; a factory running its own design answers, an assembler quotes a datasheet.

Component grade where it matters. The input capacitor's voltage rating and temperature class, the fusing arrangement, the optocoupler, the Y-capacitor. These are the parts that separate two chargers with the same output rating and a real price gap, and they are the reason a teardown is worth more than a specification sheet.

Ask what happens at 253 V and at 90 V, and in a market with unstable mains. A charger that is only tested at nominal voltage has been tested in the easy case.

What GaN changes. Gallium nitride transistors switch at higher frequencies than silicon, which allows smaller transformers and less heatsinking for the same output. The result is a physically smaller, cooler-running adapter. That is a real engineering benefit and it is the whole of the claim: GaN says nothing about isolation, component quality, protection or approval, and a badly built GaN charger is a badly built charger.

Specify the USB Power Delivery revision, not just a wattage. The standard has evolved and the profiles a device can negotiate depend on the revision implemented. Write down the revision, the fixed voltage/current profiles you require, and whether PPS is required — and then test with the devices you actually care about rather than trusting a marketing figure.

Per-port and combined output is where products disappoint. A multi-port charger advertising a large total figure usually cannot deliver its headline single-port output while every port is in use, and the sharing rule differs per model. Ask for the full power-allocation table, for every combination, and put it in the specification.

Thermal behaviour under sustained load. Anything can hit its rated output for thirty seconds. Ask what the output is after thirty minutes in a warm room, and test that yourself — thermal throttling is invisible on a specification sheet and obvious to a customer.

And do not let the cable ruin the claim. Above a certain current a USB-C cable needs an e-marker to negotiate at all, so a charger sold with an unrated cable will silently deliver less than the box says. If you bundle a cable, specify it as carefully as the charger.

Every destination has its own plug and its own approval. The pin geometry, the earthing arrangement, the insulated pin sleeves and the fusing expectations differ by market, and a plug that fits is not a plug that is approved.

The interchangeable-plug kit is the trap. A body sold with four swappable heads is four mains products. Approval is granted for a configuration — a body plus a plug — so ask which configurations are covered by the documentation you have been shown, and check that the report names them. Buyers routinely assume one certificate covers the set, and it is the most common compliance gap in this category.

The regimes to establish before you order. The EU and UK expect a technical file and the corresponding marking, and external power supplies are separately covered by ecodesign rules that set minimum efficiency and maximum no-load consumption as a function of rated output. The United States has its own efficiency regime for external power supplies as well as its safety and radio requirements. Japan and Korea require their own national approvals for mains-connected products. The numeric limits move with the rated output and with the revision in force, so establish the applicable version for your market and your model rather than quoting a figure from a guide.

Marking. The output rating, the input range, the manufacturer or brand identification and the required symbols have to be on the product itself, legibly and durably. A printed marking that rubs off is a non-compliance that arrives with the first customer photograph.

And the obligation is yours. Selling under your own brand generally makes you the manufacturer for regulatory purposes, so the technical file and the traceability attach to you rather than to the factory that showed you a certificate.

Business licence and business scope (经营范围) first — a manufacturer's registered scope names production, a reseller's names only sales, wholesale or trade. Then the design question: is this your own design or a solution-house reference design, and who can change the firmware and the protection thresholds?

Ask what is tested on the line. High-voltage (hipot) test per unit is the one to insist on for a mains product, plus insulation resistance, output regulation and a burn-in. A factory that tests every unit for dielectric strength is telling you it treats the product as a mains product.

Buy at least three samples. Test one to the limits — sustained load, thermal, all port combinations, behaviour at the extremes of input voltage. Take one apart and look at the isolation gap, the transformer, the fusing and the component markings. Keep the third sealed and dated as your reference.

Then compare the teardown with the quotation. If the price gap between two suppliers is large, the teardown usually shows exactly where it went — a smaller transformer, a thinner isolation barrier, a cheaper input capacitor, an absent fuse.

Every supplier listed on this site is a manufacturer, and the registered-scope check is one of the things confirmed before a listing goes live.