AC-DC Power supplies converts power from the mains to a stable DC power for proper operation of loads such as motor or electronic devices. A power supply can be external such as laptops and phone chargers, or internal for larger devices such as in desktop system units. They can be categorized into two types:

Linear AC/DC Power Supply

In this design, AC voltage is step-down by a transformer. The reduced AC voltage is then rectified into a direct voltage and further filtered to a more stable output. Due to transformers at the input and at low frequencies (e.g. 50Hz), miniaturization of these devices is impossible.

Switching AC/DC Power Supply

These switch power supplies employs high-power MOSFET transistors. Their advantage is the lower heat dissipation. Instead of using a transformer at the input, AC power is rectified and filtered at the input. The DC power produced is fed to a chopper which produces high frequency pulse. This high frequency wave goes through a another rectifier and filter to produce a stable DC.  

Due to amount of noise generated in the system from its design, complex control circuitry composing of integrated components is used to filter out the noise.

Check out the table below for various AC-DC power supplies.