Step 3 / 14

How does a laptop adapter work?

Pick a state at the top right to see what changes inside the adapter while the laptop charges, with no load, and with the laptop off. Then use "Find the fault" to track down the 5 faults repairers see most by measuring.

Mains

The 230 V AC from the socket; it peaks at about 325 V. Laptop adapters run on any mains from 100 to 240 V, which is why a plug adapter is all you need abroad. The inlet is usually a two-pin C8 ("figure 8") or a three-pin C6 ("Mickey Mouse") socket.

Oscilloscope

Multimeter≈230 V AC

Tap a block to see what it does and what you'd measure there.

🔧 Inside a laptop adapter: what's where?

This drawing isn't a photo; it follows the typical layout of 65–90 W plastic-brick laptop adapters. The box is usually glued shut; open it and this board comes out from under an aluminium or copper shield. The thin cut through the middle of the board is the isolation slot between the mains side and the safe side. Tap a region.

Energy path:

Tap a region to see what it does and how to spot it on the board.

🔒 This content is in the repair pack

The repair pack unlocks all interactive content in one go: diagrams and current flows, the Repair Workshop, simulations, concepts, IC guides, the Component Library and comparison guides. One sample in every section is free.

Repair pack: 5,000 ₺, members get 10% off → 4,500 ₺. Or 1-week access for 1,000 ₺.

⚠ Safety: Everything in the red area is at mains voltage; in PFC adapters the bulk capacitor rises to 390 V and can stay charged for minutes after unplugging. Discharge it before measuring, do live measurements through an isolation transformer, and do the first power-up after replacing parts through a series bulb.

Next step: Step 4How does an LED bulb work?→

Go further

Repair Workshop: find the fault by measuring Repair guide: an adapter with no output The small version: a phone charger The flyback topology The PFC topology Concept: hiccup protection Concept: first power-up with a series bulb Lesson: power supply faults