QC & PD Fast Charging Demystified: Adapter Selection Guide

When using mobile phones or charging devices, we often encounter manufacturers stating support for QC or PD fast charging. However, most users have little knowledge about their specific meanings and differences. In today’s heavily reliant landscape on fast charging, understanding these fast charging protocols is crucial. Moreover, we will address some common questions , hoping this post can offer assistance to everyone.

What is the fast charging protocol?

The fast charging protocol can be understood as a form of language communication. When an electronic device is connected to a charging accessory, fast charging can only occur if they speak the same language (i.e., support the same fast charging protocol). In fact, there are over a dozen fast charging protocols, but the most popular two are QC and PD.

What is the QC protocol?

QC stands for Quick Charge, a fast charging technology developed by Qualcomm. Compared to traditional USB transfer methods, QC protocol can deliver more power, significantly increasing charging speed.

The QC protocol undergoes continuous upgrades and iterations to better meet user’s needs, resulting in the following versions:

Version	QC 1.0	QC 2.0	QC 3.0	QC 4.0	QC  4+	QC 3+	QC 5.0
Release Time	2013	2014	2015	2016	2017	2020	2020
DC Voltage	5V	5V/9V/12V	3.6V-12V	3.6V-20V	3.6V-20V	5V/9V/ 12V/20V	5V/9V/12V/ 15V/20V
Max Current	2A	2A	3A	5A	5A	3A	5A
Max Power	10W	24W	36W	100W	100W	60W	100W
Interface Type	Micro USB	Micro USB	Type-C	Type-C	Type-C	Type-C	Type-C
Compatible with Previous Versions	/	Yes	Yes	No	Yes	Yes	Yes

With each upgrade of QC protocol, the most noticeable improvement is the charging power. This is achieved by raising the voltage and current to enhance charging speed, thereby reducing the charging time. The charging technology, charging accessories and safety protection features have also been updated and can charge the phone from 0% to 50% in five minutes. Meanwhile, during the development of QC protocol, PD protocol has also been gradually refined.

What is the PD protocol?

Version	PD 1.0	PD 2.0	PD 3.0	PD 3.1
Release Time	2012	2014	2017	2021
Input	5V 3A/12V 3A/20V 5A	5V 3A/9V 3A/12V 3A/15V 3A/20V 5A	5V 3A/9V 3A/15V 3A/20V 2.25A/20V 3A/20V 5A PPS: 3.3V-5.9V 3A/3.3V-11V 3A/3.3V-16V 3A/3.3V-21V 3A/3.3V-21V 5A	5V 3A/9V 3A/15V 3A/20V 3A/20V 5A PPS: 3.3-5.9V 3A/3.3-11V 3A/3.3-16V 3A/3.3-21V 3A/3.3-21V 5A EPR: 28V 5A/36V 5A/48V 5A AVS: 15-28V 5A/15-36V 5A/15-48V 5A
Max Power	100W	100W	100W	240W
Interface Type	Type-C	Type-C	Type-C	Type-C
Compatible with Previous Versions	/	Yes	Yes	Yes

The PD protocol has been improved many times to continuously incorporate new technologies and functions. For example, the introduction of the Extended Power Range (EPR) includes three additional Adjustable Voltage Steps (AVS) within the expanded power range. The voltage can now reach up to 48V, and the maximum power has been increased from 100W to 240W. This allows the protocol to better adapt to various types of devices, providing a more efficient and safe charging experience. For instance, MacBooks widely use the PD protocol for charging.

What are the differences between the QC and PD protocols?

After understanding the QC and PD protocols, the following three points of differentiation will be of great help to users when choosing charging devices:

Power output: The widely used QC3.0 can deliver up to 36W of power, with the latest version reaching 100W. On the other hand, the widely used PD3.0 can provide power of up to 100W, with the latest version reaching 240W, making it more powerful than the QC protocol and suitable for high-power devices.

Charging speed: Both of them can offer relatively fast charging speeds, but the PD protocol is generally faster than the QC protocol. This is because PD protocol can deliver more power, charging devices more quickly.

Applicable devices: The QC protocol can be more flexibly used for Android devices equipped with Qualcomm chips, and is also suitable for low-power devices such as power banks and Bluetooth headphones. Due to its wider power range, the PD protocol is not only suitable for low-power devices such as mobile phones, but also for high-power devices such as laptops and even small household appliances.

What fast charging protocols areused in frequently usedadapters?

Brand	Model	Fast Charging Protocol	Max Output Power
Belkin	\	PD3.0	40W
Aukey	\	PD3.0	35W
	\	PD3.0	65W
RavPower	\	PD3.0	65W
iPhone	MHJ83CH/A	PD	20W
	MNWP3CH/A	PD	35W
UGREEN	\	PD3.0	20W
Samsung	EP-T2510	PD3.0/SFC	25W
	EP-T4510	PD3.0/SFC2.0	45W
Anker	A2337	PD3.0/PD2.0/QC3.0/QC2.0/PIQ3.0	30W
	A2667	PD3.0/PD2.0/QC3.0/QC2.0/PIQ3.0	65W
Huawei	P0013	PD/QC/SCP/UFCS	40W
	\	PD3.0/QC2.0/FCP/SCP	90W
Xiaomi	MDY-16-EU	PD3.0/QC3.0/QC2.0/UFCS1.0	140W
ROMITAZ	CA-43T	PD20W/QC18W/FCP	20W

The above are the fast charging protocols supported by frequently used adapters on the market. These adapters are suitable for devices with different power requirements. When purchasing an adapter for your device, this information can serve as a reference. Meanwhile, we can observe that there are various adapter types and fast charging protocols. This diversity may lead some questions, which we will continue to explain in the following sections.

FAQ about adapter, cable, battery charger and fast charging.

1)Adapter compatibility

★Can the PD adapter charge deviceswith QC protocol?

The PD adapter can fast charge devices with QC protocol. Because it has been compatible with the QC protocol since PD3.0, it can automatically adjust the voltage and current, making it compatible with multiple protocols. However, the QC adapter cannot directly provide fast charging function for devices with PD protocol. QC3.0 is currently widely used and QC protocol has compatible with the PD protocol starting from QC4.0 , so you must know which version of the protocol is supported before fast charging .

★Will there be any damage when using a QC or PD adapter to charge a device without fast charging function?

This situation generally does not damage the device. Because the device does not support fast charging, it will only switch to normal charging. Moreover, regular adapters will have a built-in control chip that can identify whether the device supports the required protocol. If it does not support it, the output power will be reduced. Temporary emergency use is possible, but it is better to choose the original version for long-term use.

★When the adapter and device support both QC and PD protocols, which one will be used for charging?

In this case, normal charging of 5V can be achieved first. The chip in the device will then communicate with the adapter, and the specific fast charging protocol used will depend on the chip design. Unless there are special design, PD fast charging will be used first. Because the PD protocol is an industry standard, public protocols are prioritized, followed by private protocols.

2)Improper adapter selection

★What are the effects of the power mismatch between the adapter and the device?

For example, if the power of the adapter is lower than what the battery charger requires, it can result in slower charging speeds or incomplete charging of the battery. Conversely, if the power of the adapter significantly exceeds that of the battery charger, prolonged usage may still lead to battery overheating, potentially causing explosion, despite the charger being equipped with safety features to prevent over-current and over-charging.

★The safety hazards of inferior adapters

It is not recommended that you buy adapters just because they are cheap, as it is easy to acquire inferior ones. Such adapters often exhibit deficiencies in component selection, circuit design, and manufacturing processes, which may lead to the following problems:

①Short-circuit risk: Improper internal insulation or component quality problems may result in short circuits, posing a fire hazard.

②Overheating phenomenon: Low efficiency conversion rates and poor heat dissipation may cause the adapter to reach high temperatures after prolonged operation, potentially damaging both the adapter and the device.

③Electromagnetic interference: Inferior adapters may generate significant electromagnetic interference, affecting the normal operation of devices.

④Poor compatibility: Inferior adapters may fail to correctly identify and adapt to the charging protocols of different devices, thereby failing to achieve optimal charging speed.

3)Matching of adapters, cables and battery chargers

★Why do the three powers need to be consistent?

Users often complain that when using a battery charger with fast charging function, they find that the charging speed is not as fast as advertised by the manufacturer. However, this happens because the adapter and cable power are ignored. In fact, the maximum charging power is determined by the adapter, cable, and device. When all of them support the same fast charging protocol, the actual charging power is determined by the smallest one. For example:

Adapter 80W + Cable 80W + Device 80W → 80W

Adapter 80W + Cable 60W + Device 80W → 60W

Adapter 80W + Cable 80W + Device 66W → 66W

Adapter 33W + Cable 80W + Device 80W → 33W

★Do different specifications ofcables impact charging speed?

The cable is responsible for connecting the adapter to the battery charger and is mainly responsible for current transmission. Therefore, its specifications and quality also influence charging speed, manifested in the following three aspects:

①Thickness of the cable: Generally, the thicker the internal conductors of the cable, the more current it can carry, resulting in faster charging speeds.

②Length of the cable: If the quality and thickness of the cable are the same, a shorter cable length leads to reduced energy loss during current transmission, thereby enhancing charging speed.

③Compatibility with fast charging protocols: Adapters and cables must be mutually compatible with the fast-charging protocols of the device to achieve rapid charging. It is recommended to use original cables as much as possible.

★How to choose a suitable adapter for a battery charger?

It’s crucial to know what type of fast-charging protocol your battery charger is compatible with and what input power (voltage and current) it supports. Then, choose an adapter with matching specifications to ensure the battery can charge at the appropriate current and voltage. For both fast charging and safety during use, please choose a reputable brand that has obtained certifications such as CE, FCC, etc.

Series	Product	Input	Fast Charging Protocol
PB	PB2SL	5V 2A/9V 2A/12V 1.5A	QC3.0/PD3.0
	PB2S	5V 2A/9V 2A/12V 1.5A	QC3.0/PD3.0
Mini	MC3	5V 3A	QC3.0
Visible Smart	VC8S	15V 3A/9V 2A/5V 2A	QC3.0/PD3.0
	VC4SL	9V 2A	QC3.0
	VC8	5V 3A/9V 2A	QC3.0
	VC4S	5V 3A/9V 2A	QC3.0
Speedy Charging	SC1 PLUS	5V 3A	QC15W/PD15W
	SC2	5V 2A/9V 2A	QC3.0
AA/AAA	L8	9V 2A	QC3.0
Camera Charger	SN4	12V 1.5A 15V 3A/15V 2A	QC3.0/PD3.0

The above are the chargers with fast charging function in XTAR and the supported fast charging protocols. We also have received a lot of inquiries related to fast charging protocols, so we specifically list them here. Additionally, XTAR also provides adapters and cables compatible with QC/PD fast charging for users to choose from, encouraging consumers to use original accessories.

4)The impact of fast charging technology on batteries

★Does fast charging damage batteries?

This is an ever-present question. In fact, whether it’s normal charging or fast charging, both can cause wear on batteries, which is minimal and completely normal. However, there are several points to remember:

①Use certified accessories: Cheap or uncertified chargers and cables cannot provide necessary protection and may shorten the battery lifespan.

②Temperature control: Fast charging generates more heat compared to normal charging. Avoid exposing your device to extreme temperatures while fast charging. Excessive heat or cold can have a negative impact on battery life.

③Battery health management: Smartphones are equipped with features such as “optimized battery charging”. It learns daily charging patterns to slow down the battery aging process and help maintain the long-term health of your battery.

④Avoid charging while in use: Fast charging involves higher voltages, which can increase battery temperature. If you play high-power-consuming games, further temperature increases can accelerate battery degradation.

5)New trends – GaN

★What is GaN technology?

In fact, GaN is a type of semiconductor material known for its outstanding conductivity. Under the same voltage and current, it exhibits lower power losses, thus resulting in higher charging efficiency compared to traditional fast charging methods. Major brands such as Aukey, Samsung, Anker, and others have widely adopted GaN material in their charging devices. Although GaN is not directly related to fast charging protocols, its technology supports various fast charging protocols and interface types, making it can meet the charging needs of various devices. With the continuous development of fast charging technology, it is believed that GaN will become more widely popular and applied in the fast charging field.

Conclusion

The convenience brought by fast charging technology is obvious, providing charging speeds much faster than normal charging methods. Going back to what we said at the beginning, when you see the manufacturer saying it supports QC/PD or other fast charging protocols, please turn your attention to the device in your hand. Try to use adapters and cables with the same fast charging protocol and power as your device, so as to ensure fast charging and safe use.