Almost all mobile devices can now be charged via USB Type-C: for example, last year, Apple switched from its proprietary Lightning connector to USB-C on its iPhone 15.
Except for very cheap smartphones that still use micro USB charging and a few entry-level laptop models, most devices have adopted Type-C charging.
The theory behind USB sounds simple, but the reality can be more complex. Not every USB-C power adapter is suitable for every device. Not all Type-C ports support fast charging, and not every Type-C cable ensures the best charging performance.
1. Advantages of Charging via USB-C
Type-C offers many advantages for users and manufacturers:
- With a symmetrical plug design, the cable can be connected quickly and easily.
- The small socket size allows devices to be made thinner and lighter.
- Since Type-C handles data and video transmission as well as charging, ideally, only one cable is needed between a computer and peripherals, helping keep desktops tidy.
Micro USB only provides 10 watts of power, Type A chargers typically provide 15 to 18 watts, but Type-C supports the improved USB Power Delivery (PD) protocol, usually allowing up to 100 watts, and in current versions, up to 240 watts.
2. USB-C and Power Delivery: How Charging Technology Works
The USB Power Delivery (USB PD) standard is the technical foundation for USB-C charging. It defines voltages from 5 to 48 volts and currents of 3 or 5 amps, known as “power curves” or “power rules.” Depending on the charger, power cable, and device, charging power can range from 10 to 240 watts.
For example, a 30-watt smartphone power adapter offers charging profiles of 15, 27, and 30 watts, while a laptop power adapter offers profiles of 45, 60, 65, or 100 watts.
Before starting the transfer, the charger (source) and the powered device negotiate the required voltage and current: the charger first checks if the cable can transfer up to 3 or 5 amps and provides a basic 5-volt voltage.
Then, it tells the powered device what other voltages it can offer. The powered device responds to its needs, allowing both to agree on an appropriate power profile.
Ideally, any USB-C charger should charge the device at optimal performance and as quickly as possible. Even if the charger doesn’t meet the device’s requirements, it should provide at least some charging power, resulting in a slower charging process.
Conversely, using a power adapter with a higher output than the device needs doesn’t speed up the process, as the device can’t draw the excess power.
Since USB PD version 3, external power units and powered devices can dynamically adjust voltage and current. To achieve this, both must support the optional standard extension PPS (Programmable Power Supply).
Devices can request voltages and currents slightly deviating from predefined power profiles: this can speed up the charging process but also ensure less stress on the battery during charging or provide the appropriate charging power in real-time based on the current system load for smartphones or laptops.
3. How to Determine if a Power Adapter is Suitable for a Device
The easiest way is to use the power adapter recommended by the manufacturer. This is common for laptops since new devices usually come with an appropriate power adapter.
Smartphones and tablets typically no longer include power adapters in the sales box: you can purchase a suitable charger from the device manufacturer.
To charge all devices with one charger, it should have enough charging power for the most powerful device and match the power profiles of devices with lower power requirements.
Typically, laptops are the devices that need the highest charging power: ultraportable laptops usually require 45 watts, standard laptops need 60 watts, and particularly powerful laptops need 100 watts.
Devices like smartphones, tablets, portable speakers, or headphones usually suffice with 30 watts.
To ensure a USB-C laptop power adapter can charge other mobile devices, it needs to support the 15-watt and 27-watt power profiles via USB-PD.
Conversely, laptops can also be charged with smartphone power adapters. The power needs to be at least 27 watts and 9 volts. This is sufficient for small, lightweight laptops.
It’s best to turn off the laptop while charging, as the battery may drain if the running power consumption exceeds what the power adapter provides. However, many laptops require 15 or 20 volts of charging voltage. If your smartphone power adapter provides this voltage, it can charge the laptop—though usually more slowly.
4. Choosing a USB-C Cable
A good USB-C cable is crucial for stable charging power from the charger to the device. These cables can standardly transfer up to 3 amps of current.
This is enough for mobile devices like smartphones and tablets. Laptops can also charge at 60 watts with these cables, sufficient for small and lightweight laptops. However, for higher-power laptops, the charging time may increase based on battery size and operating load.
To charge these laptops at optimal speed via USB-C, you’ll need a cable that can transfer 5 amps of current. However, both the power adapter and the USB-C cable must support the PPS standard or higher current transfer (5 amps).
5. Multi-Port Chargers: One Power Source for All Devices
Typically, one charger isn’t enough for many devices: you often want to charge different devices simultaneously via USB-C. This is why chargers with several USB-C and USB-A ports exist, capable of charging a laptop, smartphone, and headphones simultaneously. This is also handy when traveling.
When choosing, it’s important to understand the power distribution across the ports: the maximum charging power specified by the manufacturer is usually the total for all ports combined.
For example, if you choose a 65-watt power source because you also want to charge your laptop, it usually provides 65 watts only when used on a single port. If you charge another device on a second port, the power gets divided between 45 watts on one port and 20 watts on another, slowing down the laptop’s charging speed.
If all ports on a three-port power source are occupied, the power per port may be further reduced.
Therefore, you should check the technical data provided by the power supplier before buying: reputable manufacturers will list the charging power of each port when connected singly or multiply.
The ideal power supply should support USB-C PD and preferably also PPS!
Many manufacturers promote a shorthand “GaN” on more expensive models: this stands for a semiconductor material called gallium nitride. The voltage converters in these chargers are made from this material: they can work efficiently without heating up, allowing even small-sized chargers to have strong charging capabilities.
Related:
- Limit iPhone Charging to 80% for Better Battery Life
- What Is Gallium Nitride (GaN)? Learn Its Uses & Benefits
- USB Copy Speeds: Why Transfers Are Fast and Slow
Disclaimer: This article is created by the original author. The content of the article represents their personal opinions. Our reposting is for sharing and discussion purposes only and does not imply our endorsement or agreement. If you have any objections, please contact us through the provided channels.