Power Delivery (PD) and Quick Charge (QC) are fast-charging standards that allow a device to request the required voltage and a charger to adjust its output parameters. As a result, a single USB port can provide multiple voltage levels and, of course, current for charging.
Early versions of USB provided 5 V at 0.5 A. In later versions, the current was increased to 1 A and 2 A; however, to provide higher power at 5 V, a higher current was required, which in turn required an increase in the conductor cross-section and the size of the charging cables—and, of course, no one wanted to use cables as thick as a finger.
Fast charging solves this problem by increasing the voltage instead of the current. For 18 W at 5 V, 3.6 A is required, whereas at 12 V, only 1.5 A is needed. This reduces the need to increase the conductor cross-section. While phones typically use 5 volts, laptops typically use 20–48 V for charging and power adapters rated at 65 W or more.
Fast charging standards
Power Delivery (PD) and Quick Charge (QC) differ mainly in their communication protocols. Power Delivery is an open standard developed by the USB Implementers Forum, while Quick Charge is a proprietary technology created by Qualcomm. Starting with Quick Charge 4, support for Power Delivery was introduced, which significantly improved compatibility between the two standards.
In the early 2010s, many manufacturers introduced their own fast-charging technologies. Among them were MediaTek Pump Express, Samsung Adaptive Fast Charging, Oppo Super VOOC, Huawei SuperCharge, Anker PowerIQ, Google Fast Charging, and Motorola TurboPower. However, most of these solutions did not achieve widespread adoption.
Over time, Power Delivery became the most widely supported fast-charging standard, compatible with a broad range of devices, including products from Apple. Quick Charge, in turn, gained popularity in devices based on Qualcomm processors and in chargers from various manufacturers. With the addition of Power Delivery support, its versatility has increased significantly.
How charging works
Both Power Delivery and Quick Charge rely on communication between the device and the power source.
When a device is connected, before voltage is supplied for charging, a control signal is transmitted through the signal wires—in simple terms, a specific voltage level is requested. The charger or power bank, having received information about the required parameters, delivers the appropriate voltage through the power wires.
USB Type-C connectors are typically used for this process. Full-featured cables have a complex internal structure that supports data exchange and power negotiation. However, not all USB Type-C cables are identical. To reduce cost, many cables are simplified, which can limit charging speed.
Supported voltages for Power Delivery and Quick Charge
Fast charging increases the output power by raising the voltage while maintaining the same level of direct current. The voltage values supported by the standards are listed below.
| Voltage (V) | Current (A) | Power (W) | Cable Type |
|---|---|---|---|
| 5V | 3.0A | 15W | Standard Power Range (SPR) |
| 9V | 3.0A | 27W | Standard Power Range (SPR) |
| 15V | 3.0A | 45W | Standard Power Range (SPR) |
| 20V | 5.0A | 100W | Standard Power Range (SPR) |
| 28V | 5.0A | 140W | Extended Power Range (EPR) |
| 36V | 5.0A | 180W | Extended Power Range (EPR) |
| 48V | 5.0A | 240W | Extended Power Range (EPR) |
Chinese manufacturers have expanded the range of supported voltages by adding support for 12-volt or 24-volt outputs, which are primarily used for purposes other than charging. For example, a portable charger can be used to power a router or surveillance cameras. For instance, some Baseus portable chargers support 12-volt outputs. Such devices often use special cables, such as USB-C–DC cables, equipped with built-in chips to determine the required output voltage.
Data transfer standards between the charger and the device.
There are two standards for data communication between devices: SRP and ERP.
SRP (Standard Power Range)
This is the basic mode. Communication between the device and the charger takes place via the CC line. The device specifies the voltage it requires, and the charger supplies it as a fixed value. The parameters do not change during charging.
EPR (Extended Power Range)
This is a more advanced mode. It uses an additional VCONN line, which allows the device and the charger to continuously exchange data. Thanks to this, the voltage can be adjusted directly during charging with high precision and in small increments. This is primarily designed to extend battery life: up to 70% charge, the device consumes maximum power, reducing it as it approaches full charge.
Cables rated for 100 W and especially up to 240 W must support the EPR standard. They usually have the corresponding marking, although in practice this is not always the case.
