why are some smartphone AC adapters bigger than others?

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Smartphones usually come with an AC adapter for charging. It plugs into an electrical outlet, and then plug the phone’s USB cable into the adapter.

The iPhone 4s has a really small AC adapter for USB-A, about the size of a walnut.

The Google Pixel 4a has a really big AC adapter for USB-C, about the size of a deck of cards.

Why is one AC adapter so much bigger? Something special about USB-C?

Thanks!

In: Technology

The type and quality of the parts inside. More expensive parts used to convert the electricity will be smaller while cheaper ones will generally be larger. Also simply the design was intended to be that shape and size.

Modern smartphones have larger batteries and greater needs. That Apple charger is 5 watts. The Pixel’s is 18 watts.

A phone can still be charged with a lower wattage charger, but it will take longer.

Power availability

The old iPhone 4 was being charged off of a 5V 1A charger so it needed to be able to output 5 Watts which isn’t a ton

The larger Pixel 4a charger can output 18W of power so it needs to use larger components that can handle the greater power levels.

More powerful chargers often have no choice but to be bigger for heat reasons too. Chargers aren’t perfectly efficient so a 90% efficient 5W charger is wasting about 0.5W of heat but a 90% efficient 20W charger is wasting 2W of heat which would make a small box very hot so they need to spread things out and give more surface area to shed heat through to keep things a happy temperature

AC is rectified in order to be turned into DC. This is in part done by using a transformer. A transformer isn’t like other electronics like transistors that can be made smaller and smaller. New smartphones charge quickly because they are charged on like 25 watts. This means you need a bigger transformer. This is probably the majority of the bulk.