Nowadays, mid-to-high-end smart phones have gradually begun to popularize two very practical technologies, NFC and wireless charging. The former can be used for bus or access control, and the latter can get rid of the shackles of cables. Charge other devices.
For a long time in the past, both NFC and wireless charging have been in a harmonious state. But recently the NFC Forum, the official organization of the NFC standard, broke this situation and gave it the function of NFC wireless charging. It’s your job.
What is NFC?
NFC (Near Field Communication) is a short-distance high-frequency wireless communication technology that allows non-contact point-to-point data transmission between electronic devices and exchanges data within a distance of 10cm. When the mobile phone has a built-in NFC hardware module, it will have the opportunity to implement the following three functions:
P2P Mode: We can understand this mode as two-way data sharing, that is, two NFC terminals exchange data with each other. It is mainly used as the initial verification of Bluetooth and wireless connections.
Reader/Writer Mode: The reader mode of the NFC module, that is, like a card reader, it can read the relevant information of the electronic tag, realize the data exchange between NFC mobile phones or read other IC cards Data within.
Card simulation mode: NFC that supports this mode is usually called "full-featured NFC", which can virtual bank cards, bus cards and unencrypted access cards. Almost all new mobile phones now support this mode.
Key coil
The NFC module on a smartphone usually includes a complete CLF (contactless front-end module), radio frequency antenna, and SE (safe area) units, and the most impressive thing is undoubtedly a striking coil.
Its working principle is based on the mutual coupling of inductances, which regularly changes the impedance of the coil to regularly change the load of the primary coil of the inductance, so as to allow the coil in the reader end (which can be a mobile phone or a bus gate, etc.) Read out the required information.
Crossover coil
Many friends who see the coil of NFC should be familiar with it—isn’t it the same as the coil of the wireless charging module?
Yes, the wireless charging technology commonly used in mobile phone loops at this stage is based on electromagnetic induction. Its principle is the Faraday battery induction law, which is to give the primary coil a certain frequency of alternating current and generate a certain current in the secondary coil through electromagnetic induction. , Thereby transferring energy from the transmitting end to the receiving end.
Implemented on the mobile phone is to embed dedicated coils (including conversion and identification, power management and other chips) in the back cover of the mobile phone and in the wireless charging base, respectively. When power is input to the transmitter coil, it will A magnetic field is generated, and the magnetic field induces a current in the coil at the receiving end to realize the charging process.
NFC coils could only be used to transmit communication signals before, but the NFC Forum has brought a new WLC wireless charging specification (Wireless Charging Specification) this time, allowing the coils in the NFC module to also be used for wireless charging.
Prospects of WLC specifications
It should be noted that what the NFC-based WLC specification brings is actually a "reverse wireless charging function", which allows mobile phones to pass through the NFC coil and reversely supply smart watches, smart bracelets, wireless headsets, stylus pens, etc. Charging small IoT devices instead of charging mobile phones with a wireless charging base.
Many mobile phones that support wireless charging are focusing on reverse charging
In addition, due to the small scale of the NFC coil, the WLC specification can only use one antenna of the NFC device to communicate and charge at the same time, so the power is only 1W. However, 1W of power is sufficient for most IoT devices, and it is of great significance to the Internet of Everything.
Unfortunately, according to the information published by the NFC Forum, it is necessary to support the new NFC chip to support the WLC specification, which means that the existing NFC devices still have no chance to enjoy this convenient function.
In the foreseeable future, when the WLC specification is recognized by the market, the integration of wireless charging coils and NFC coils will be gradually completed on smartphones, allowing a set of coils to take into account both wireless charging and NFC functions. Then the spring of IoT devices will come.
