Qi® 1.3 and Qi 2.0 Wireless Charging Specification

The Wireless Power Consortium (WPC) was established in 2008 and is an open standard continually being developed by more than 400 member companies who collaborate to develop the wireless charging specification. Their main objective is to ensure global compatibility.

A little bit of history first. In 2015, the WPC released version 1.2 of the standard to help wireless charging technology compete against wired solutions. That version of the standard allowed fast charging capability and most of the updates to the 1.2 specification were focused on continuous improvements and bug fixes. By 2020, there were already more than 1 billion phones using the Qi standard version 1.2.4.

In 2021, the WPC learned a lot and released the new Qi 1.3 version of the specification and later released the Qi 2.0 in 2023. There are no major changes in the power management functions besides general improvements like Foreign Object Detection (FOD). The biggest new addition is secure authentication. Secure authentication is not just algorithms, but much more than that, involving a secure manufacturing flow coupled with a specific security process delivering a personalized “Secure Storage Subsystem” (SSS as defined by the standard) which is commonly called a secure key storage device or secure elements in other markets with an associated security rating which we will discuss in this blog. Sounds complicated, but we will explain why it’s not!

What type of applications are affected by the Qi 1.3 and Qi 2.0 specification?

The WPC has nicely organized the applications by power rating. The illustration below shows the different classes. The 15W working group is the first one to push the adoption of the Qi 1.3 and Qi 2.0. This 15W group is where the cellphone companies fit. The other three groups are likely to adopt many of the requirements already defined by the Low Power class.

Why was secure authentication added to the standard?

It’s all about safety, user experience and warranty. In the world of security, hackers or counterfeiters look for how much return on investment they can obtain on any given attack. Does my attack scale, how much does it cost me, what do I get in return?

For example, a cell phone is a high value asset costing more than a thousand dollars from the biggest selling companies producing billions of phones a year. This expensive consumer product driving high volume production is essentially sitting on a “toaster” which the charger is if the power control loop is not well regulated. Various scenarios could include:

• The phone could charge too slowly providing a bad user experience
• The phone could overheat which could negatively alter the expected performances
• The battery could be damaged by a poorly regulated charge from uncertified chargers
• Worst case, the phone could light on fire which would have bad legal and brand reputation consequences, directly impacting revenue

For all these reasons, there is a clear need for a certification body that provides a quality label on wireless chargers to protect consumers physically and financially. That’s where the WPC steps in. Now, let’s imagine a poorly designed charger inside a car; this can create a direct safety concern for the entire vehicle. The need for a certification is even more relevant but the question becomes, how to enforce it. Trust between the phone and the charger must be implemented and that’s where secure authentication comes into play.

The principle of secure authentication in the context of Qi 1.3 and Qi 2.0

The phone is the receiver, which sits on the charger referred to as the transmitter in the specification. Qi 1.3 and Qi 2.0 mandates a one-way authentication, meaning the transmitter must cryptographically prove to the cell phone that it is a trusted, “do-no-harm” member of the WPC ecosystem. If not authenticated, the phone either rejects the charge entirely or more typically limits the charging power accepted to 5W instead of 15W, resulting in a slow charge. Given most cell phones that are running several applications at once, such as navigation and streaming music will consume more power than a 5W charge, it will result in a poor user experience. This can negatively impact the charger manufacturer brand reputation as a whole.

When comparing the Qi 1.2.x and Qi 1.3 and Qi 2.0 versions of the standard, is it important to know which phones and chargers will work together. The short answer is when the phone supports Qi 1.3 and Qi 2.0, the corresponding charge must support that version of the standard too or the phone may either reject the charge or only accept a 5W charge.

In part one, we discussed why the secure authentication was added to the Qi WPC1.3 and 2.0 wireless charging specification. Read part 2 where we explain how secure authentication works including the key ceremony process and present Microchip solutions. Finally, make sure to check out the step-by-step process for triggering the key ceremony.

Resources

Qi 1.3 Reference design :https://www.microchip.com/en-us/tools-resources/reference-designs/15w_multi-coil_wireless_power

Consumer Secure Storage Subsystem: https://www.microchip.com/en-us/product/ecc608-tflxwpc

https://www.microchip.com/en-us/product/ECC204

Automotive Secure Storage Subsystem: https://www.microchip.com/en-us/product/ta010

https://www.microchip.com/en-us/product/TA100

Microcontroller: https://www.microchip.com/en-us/product/dsPIC33CK256MP506

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