# Power supply

> The box that turns wall electricity into the steady, low voltage a computer runs on.

- Level: Basic
- Topics: Hardware
- URL: https://tidbit.legios.com.ar/power-supply/
- In Spanish: [Fuente de alimentación](https://tidbit.legios.com.ar/es/power-supply/)

The electricity in a wall socket is alternating current (AC) at roughly 110 or 220 volts, depending on the country. Chips need something very different: direct current (DC), at low and extremely stable voltages like 12, 5 or 3.3 volts, and often even less inside the chip. The **power supply** does that conversion. In a desktop PC it is a metal box with a fan inside the case; in a laptop or phone it lives mostly in the charger, the **power adapter** you plug into the wall.

A power supply is rated in watts: how much power it can deliver at most. A basic office PC needs a few hundred watts; a gaming PC with a big graphics card can need far more. Buying one too small makes the computer shut down or restart under load. Efficiency matters too: part of the energy is lost as heat in the conversion, and better units waste less. In desktop PCs, the 80 Plus labels (Bronze, Gold, Platinum) certify that efficiency.

It is one of the least glamorous parts, and one of the most important. A cheap, poorly made power supply can give unstable voltage that causes random crashes, or fail and take other parts with it. Servers in data centers usually have two, so one can fail without the machine going down.

## An analogy

A water treatment plant for electricity. What comes from the river is strong, uneven and not drinkable; the plant cleans it, lowers the pressure and delivers a steady stream that is safe for every tap in the house.

## Keep in mind

- Converts wall AC into the low, steady DC voltages that chips use.
- Rated in watts; it has to cover the total draw with some margin.
- Efficiency labels like 80 Plus measure how little it wastes as heat.
- A bad power supply can cause random crashes or damage other parts.

## Go deeper

- [Power supply unit (computer) on Wikipedia](https://en.wikipedia.org/wiki/Power_supply_unit_(computer))

## Related terms

- [Chip](https://tidbit.legios.com.ar/semiconductor-chip/): A sliver of silicon carrying billions of tiny switches that compute and remember.
- [Laptop](https://tidbit.legios.com.ar/laptop/): A whole computer folded into one portable case that runs on a battery.
- [Server](https://tidbit.legios.com.ar/server/): A computer whose job is to answer requests from other computers, all day, every day.
- [Data center](https://tidbit.legios.com.ar/data-center/): A building full of servers where the internet, the cloud and AI actually run.