How about NFC Wireless Charging

[Schuyler]

I understand that I have exited the NFC WLC function and I currently have X-NUCLEO-NFC07A1. How do I charge the WLC-Listener using the battery charging function shown in the legend?

[VGros.3]

I was about to ask the same question.

In ST pdf "NFC charging: The tiniest solution for wireless charging", I read that we have to use "negociated mode" in order to receive up to 1W, depending on the power class.

However, in the ST25DV-I2C datasheet, nothing is mentioned about it. Does anyone have information ?

[Schuyler]

Yes,I also obtained from PDF that ST25DV-I2C can be used as a listener, but I didn't find out how battery charging was implemented, nor did I give specific instructions. I don't know how NFC WLC can power MCU with up to 1W.

[RhSilicon]

I don't know if it's feasible to use NFC to charge the battery. Perhaps a super capacitor can be better used with NFC than a lithium-ion battery. When I think of NFC, I think of a credit card that the user brings to the stationary device for charging credits, and this is done in a short time, a few seconds.

Charging a battery takes many seconds, sometimes several hours.

When I think Wireless Battery Charger, I think Qi Battery Charger.

See: Wireless Battery Charging

 

Qi is focused on wireless charging above 5 W, while NFC wireless charging currently targets 250- to 1,000-mW charging, with the potential to increase support to at least 3 W. Qi and NFC already complement each other as an in-console solution. Qi chargers typically also implement NFC card protection.

 

STMicroelectronics and NXP are among the NFC wireless charging pioneers. Products in ST’s ST25 family of NFC and RFID tag and reader ICs feature NFC wireless charging for a variety of NFC-enabled solutions.

“NFC wireless charging provides easy integration into small applications through tiny antenna footprints, with targeted antenna dimensions ranging down to below 0.15 in.2 [1 cm2],” said Peter Neger-Loibner, NFC product marketing manager at STMicroelectronics. “Using PCB or flex-PCB antennas, these products can be an ideal fit for complex form factors. It is this convenience and versatility that make NFC wireless charging so useful for consumers and easy to integrate for developers.”

Panthronics AG also added wireless charging functionality to its product line. Its next-generation system solutions include PTX130W, an NFC wireless charging poller IC, and PTX30W, a fully integrated listener IC.

“Our goal is to simplify NFC wireless charging technology, making things easier for our customers and accelerating its adoption into new applications,” said Alessandro Goitre, director of product management at Panthronics. “This does not mean we compromise on performance; we continue to push the boundaries on what is achievable. The appetite for leveraging the benefit of NFC wireless charging continues to grow. I think we’re seeing the beginning of what will prove to be an amazing era for NFC-based technology in digital styluses, wearables, smart glasses and [smart] rings, hearables and medical sensors. All these devices will improve the customer experience through NFC wireless charging.”

Infineon Technologies is developing a new NFC wireless charging turnkey solution with an emphasis on the power density (received power/PCB size) and the integration of system functions, such as thermal control and battery charging.

“Our goal is to help customers achieve a very cost-effective implementation of NFC functions,” said Qi Zhu, director of product marketing and business development at Infineon. “Reducing the total ownership cost is one aspect. The PCB size limitation of compact devices is another reason customers are asking for a higher level of integration.”

https://www.eetimes.eu/2023-the-year-of-nfc-wireless-charging/

[RhSilicon]

Another issue is energy waste. It's really annoying to have to spend time looking for the right position to get energy transfer efficiency.

• The efficiency drops dramatically at larger distance (z/D > 1) or at a large size difference of the coil (D2/D < 0.3)
• A high efficiency (>90%) can be achieved at close distance (z/D < 0.1) and for coils of similar size (D2/D = 0.5..1)

https://www.wirelesspowerconsortium.com/knowledge-base/magnetic-induction-technology/effficiency/transfer-efficiency.html

[VGros.3]

@RhSilicon Thanks for your answer, the power efficency graph is interesting

[Schuyler]

Hi @RhSilicon 

Thank you for your reply, then I need to use NFC to realize signal acquisition without power supply, and I need to use NFC WLC technology. The products of ST Company only have PDF but have not been ordered. On the contrary, I have learned about PTX130W, an NFC wireless charging poller IC, and PTX30W, a fully integrated listener IC.

 

[Rene Lenerve]

Hi @Schuyler,

WLC NFC Charging is a standard defined by the NFC Forum, and is aimed to charge small batteries. There is a communication protocol between the Poller and Listener to negotiate power. It is not intended to use in another application, you need at minima an NDEF message to start a charging phase. WLC NFC Charging is composed of multiple Wireless Power Transfer phases and is not always providing full power at any time, this is negotiated between Poller and Listener during exchange phases.

Regarding ST25DV-I2C it is not designed to work for WLC alone, you'll need an MCU that must communicate with the Poller through NDEF messages (and manage the WLC protocol), and you'll need the Rectifier and Protection stage that is not framed in your first post.

I hope this will help you.

Kind Regards.

 

[VGros.3]

@Rene Lenerve  Thank, you. You are saying that ST25DV-I2C should be suitable for WLC with an MCU. But we have to "communicate with the Poller through NDEF messages (and manage the WLC protocol)". Is there a guide / application note in order to do this ? I do not find anything concerning WLC in ST25DVxxKC datasheet.

[Schuyler]

Hi @Rene Lenerve 

 ST25DV-I2C it is not designed to work for WLC alone, I'll need an MCU that must communicate with the Poller through NDEF messages，but according to the instruction manual, the listener only needs three modules: L, ST25DV and battery charging. Is there any specific description of the NDEF protocol of MCU you mentioned?

Kind Regards.

[Rene Lenerve]

Hi @Schuyler ,

NFC WLC is a specification defined by the NFC Forum, they have defined a communication protocol via NDEF messages in order to negotiate between Poller and Listener the power to charge a battery and is not intended for other applications. Refer to the NFC Forum web site for more information on that topic.

As explain earlier, ST25DV (as other tags) risks overheating if the Poller increases its power. So for WLC you need Hardware components that protect the tag and recover excess energy for the charger (first stage in your screenshot "Rectifier and Protection").

Hope this can help you.

Kind Regards.

 

[Schuyler]

Hi @Rene Lenerve 

So if I want to use NFC to achieve energy and information transmission, but the current use of EH pin output is not enough to provide large energy, can not drive the MCU to complete other tasks, then what should I do? I hope you can give me some specific suggestions so that I can complete this task.

[RhSilicon]

Coin type lithium battery (CR2032(3V), A23(12V)) is generally used for general purpose remote control such as garage door. If your project needs more uptime from the MCU, you might be able to use a user replaceable battery if it can't recharge the battery via NFC.

[Schuyler]

Hi @RhSilicon 

As you know, I need to use the energy collected by NFC to run the MCU to complete other tasks, but I can't run the MCU properly only with less than 10mw energy of EH, so do I have any other way to complete this project?

Thanks

[VGros.3]

What I understand with all your replies, is that NFC WLC (wireless charging) is not a mature technology. There isn't any application note and ST25 datasheet does not give any information about this.

For the wireless charging part of my project, I think I will use Qi technology.

Thanks

[Schuyler]

Hi @VGros.3 

Yes, I also think so, because ST company does not have any relevant information, I can not find information from it. But I need to use NFC to complete the transmission of information and energy, not only to complete the task of power supply, but also to transmit signals.