Quick Charge is the name given to an originally proprietary method of transmitting electrical power via a USB interface by controlling the supply voltage by the connected device. It is mainly used for fast charging of mobile devices such as special smartphones or power banks.
The first version of the standard was developed by Qualcomm in 2013, revised in various versions in the following years and is used under various trade names, such as Adaptive Fast Charging by companies such as Samsung, for mobile devices.
The mobile devices that support Quick Charge are based on the Snapdragon, a system-on-a-chip (SoC) from Qualcomm. Quick Charge is a competitor interface to Oppo Electronics’ proprietary USB charging interface VOOC, which works similarly to Huawei SuperCharge.
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Even though Qualcomm QuickCharge is proprietary, how it works has already been fully deciphered through reverse engineering. Communication and voltage control is done via USB 2.0 data lines, unlike the power lines of the MediaTek PumpExpress fast charging standard. The USB-PD (Power Delivery) specification has now standardized power transmission in such a way that version 3.1 (2021) even covers power ranges up to 240 W.
How Quick Charge Technology Works
Since the electrical voltage on conventional USB 2.0 ports is fixed at 5 V and the contacts of the USB plugs used are limited in current carrying capacity to 2 A, the maximum transmittable power is limited to 10 W without risk of overheating.
With Quick Charge, a higher electrical voltage is set by the specially designed USB power adapter on the power supply contact, which is changed in steps according to the requirements of the mobile device, depending on the version of Quick Charge. In addition, temperature sensors are installed in the charge controller of the mobile device and in the USB power adapter to prevent overheating.
The higher voltage bypasses the limitation of the charging power due to the electrical resistance of the USB cable. It allows a higher power to be transmitted at the same amperage and accordingly does not generate additional heat in the cable. For example, the raised voltage allows charging through conventional and longer USB wires.
This increased voltage is converted downwards within the end device to the required voltage. The different voltages and charging capacities depending on the version of Quick Charge. Qualcomm QuickCharge 3.0 is backwards compatible with QuickCharge 2.0.
With the Quick Charge 4.0 and 4.0+ versions released at the end of 2017, Quick Charge is now compatible with the USB-PD (Power Delivery) standard and USB-C (USB Type-C connector).
The so-called fast charging cables are unsuitable for Quick Charge. In these cases, the two data lines of the USB standard are short-circuited so that the connected device is signaled that it can draw an unlimited current from the power supply at the given voltage (usually 5.0 V to 5.5 V). However, Quick Charge requires these data lines for voltage control.
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