The Mini 2 requires a steady and clean source of power at 5.1 volts and 3 amps.  The Mini 2 comes with a dedicated power supply which meets these requirements. It’s not recommended to use a phone charger or USB port with cable to power a Raspberry Pi as they typically have poor quality power and will void warranty. Before using anything other than the supplied power supply be sure to research the power source carefully and consider the warranty issues.