Wikipedia
VOOC
The OPPO VOOC (Voltage Open Loop Multi-step Constant-Current Charging) Flash Charging system is a rapid-charge technology created by OPPO Electronics, which, at present, is able to charge certain OPPO devices from 0 to 75% in just 30 minutes. At present, the OPPO Find 7(a), the OPPO R7, the OPPO R5(s), the OPPO N3, OPPO F1 plus, the OPPO R9 (Currently only available in Singapore), and the OPPO HA-2 are the only models that support VOOC capability.
The VOOC Flash Charge circuit technology reportedly lowers the temperature of the charging adapter, and creates an interface from the adapter to the phone, which improves the speed and safety of the charge.