In the last few years the charger pins of the mobile phones have become standardised to a large extent. Today you have two kinds of chargers which cover almost 60-70% of all phones. The Android ones use USB-C and the iOS ones use Lightning connector. The new technologies bring along with them the enhanced capabilities for fast charging. The chargers are able to sense the current charge levels of the phone and depending upon this they are able to charge the phone very fast initially and then as the charge levels increase, the charger decreases the charging voltage. So effectively, you can go from 0 to 50% in less than 30 mins and then the next 50% takes an hour or so.
Generally, the phones operate at 5 V DC. So historically, the phone charges have delivered 5V to the phones. Depending upon the size of the battery(mAh rating), the current provided by the charger used to vary. So phones with 800 mAh battery would be fine with 300 mA chargers, where as ones with 3000 or 4000 mAh battery would require a 2 Amp charger. In the new charging technologies which have been developed by the chip manufacturers, the charger sends out 9V or 12V initially till the battery reaches 50% and then it decreases the charging voltage to 5V till the battery is fully charged and after wards it sends out pulses of 5V to maintain the charge.
The most widely used technologies are Qualcomm and PD.Project Disha at Omniactive Health Technologies »« Why we procrastinate