Power converters are the AC/DC converter and AC adapter. The AC/DC adapter is a type of external power supply, often enclosed in a case similar to an AC plug (a regular home use plug). Other names for power converters include plug pack, plug-in adapter, adapter block, domestic mains adapter, line power adapter, or power adapter. AC power converters are used with electrical devices that require power but do not contain internal components to derive the required voltage and power from mains power. For example in electronics, a voltage converter is a device which converts AC Power to DC Power. It changes the voltage of an electrical power source and is usually combined with other components to create a power supply. The internal circuitry of an external power supply is very similar to the design that would be used for a built-in or internal supply.
Voltage power converters can be used in vehicles with 12 V DC outlets. A simple voltage dropper can be used to reduce the voltage for low-power devices; if more than 12V is required, or for high-powered devices, a switched-mode power supply is used. The output will usually be DC in the range 1.5–24 V.
Switched-mode power supplies (SMPSs) work by taking mains voltage(your cars power) that is rectified to a high direct voltage driving a switching circuit, which contains a transformer operating at a high frequency and outputs direct current at the desired voltage. The high-frequency ripple is more easily filtered out than mains-frequency. The high frequency allows the transformer to be small, which reduces its losses. The result is a much more efficient, smaller, and lighter device. Safety is ensured because there is still a transformer which electrically isolates the output from the mains.