The OPPO VOOC (Voltage Open Loop Multi-step Constant-Current Charging) Flash Charging system is a proprietary rapid-charge technology created by OPPO Electronics, which, at present, is able to charge certain OPPO Flash Charging system. ... This, VOOC operates at 5V and 4A. Charging system With 4x f aster-charging speed than conventional chargers, the VOOC flash charging system will make your phone ready to go when you are on your way out the door. The 5-layer protection when compared with the conventional high current protection gives you protection from the adapter to the port and interior of the phone.It is absolutely safe to use VOOC , has replaced the voltage reducing circuit with an MCU, effectively preventing your mobile phone from overheating while charging.