How AC Adapters Work

Laptops are useless without AC adapters. They are what run your laptop when your battery dies. They are what charge that battery when you want to use it on the go. With that in mind, it’s important to have a basic understanding of how they do what they do, especially if it comes time to replace them.

A laptop AC adapter will consist of essentially three main parts: the cord that carries unusable AC to the box, the box that converts the AC to DC, and the cord that carries the usable DC to the laptop. Your house is powered with AC, or alternating current, because it travels well without losing energy, but alternating current is not usable by laptops. They require direct current, or DC, power.

The box of your adapter technically does more than simply converting current, or rather there is more to the process. As alternating current enters the box from the cord connected to your wall, it is run through a transformer. This drops the current from about 110 volts to around 19 volts, which is what most Sony laptops can work with. Other brands of laptop often use 15 Volts, but most other variations are plus or minus a volt in either direction. The current then runs through a rectifier which essentially forces the current out in one direction only, thus making direct current. Finally, the current runs through a regulator, ensuring a steady stream of voltage despite any changes in power consumption. After running through all these components, the current continues through the second cord, and into your laptop.

Knowing the basics of AC adapters will allow you to make some more educated decisions on replacement or upgrade adapters. First, check your cords. Match your main power, or AC, cord to whatever plug you’ll be using. For example, plugs in Europe are different than in the US, and plugs in your car or on a plane are different than the ones in your home. Also, invest in a surge protector to help ensure the longevity of your AC adapter, essentially protecting it from being overloaded.

Your laptop will also require specific voltage from your adapter, and a minimum wattage as well, typically listed on the underside of your machine, or available from the manufacturer. When it comes to wattage, you can get higher than what is listed on your machine’s specifications, but going lower can cause the box to overheat, and shortening the life of the laptop AC adapter.

As for the DC cord, the main thing to look for is the connector. If it doesn’t fit the DC jack on your machine, it won’t do you any good at all. If you’re not sure, check with your spare parts retailer, chances are they will be able to assist you in finding an adapter that will fit your machine. Also, when looking at replacing an adapter, be sure to confirm that the problem isn’t with the physical DC jack on your machine, as it can become loose or unsoldered. A loose DC jack can cause problems that may simulate issues with your AC adapter and may require the DC jack to be repaired.