iPhone 12 and 12 pro max Dual voltage charging

Apple power adapters and virtually just about any others will operate at 100-240 Volts and 50/60 Hz, so you won't need a voltage converter.

But, you will need a wall plug adapter in most other countries.

The phone charges via a 5 volt source. If using an Apple supplied (or other high quality) charge cube, it will convert 100-240 volts AC to that required 5 volts DC.