A mobile phone charger is

A mobile phone charger functions as a step-down transformer. It is designed to convert the high-voltage AC mains (typically 100-240V) into a much lower, stable DC voltage (usually 5V) suitable for charging a mobile phone battery. Internally, these chargers are composed of a power transformer and a rectifier circuit. While modern chargers utilize Switch Mode Power Supply (SMPS) technology for efficiency, the fundamental electrical process involves stepping down the voltage from the high-input mains to a low-output level. This process ensures that the delicate electronic components and the lithium-ion battery of the phone are not damaged by high voltage. Unlike an inverter, which converts DC to AC, or a UPS, which provides backup power, the charger specifically reduces voltage to facilitate safe energy transfer.