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How is the Wireless charging technology?


Abstract: Since Apple iPhoneX supports wireless charging, and many fruit powders can't find a suitable Wireless Charger when using iPhone X, we know that iPhonex supports QI standard wireless charging, so the wireless Charger about it is even less. Less. Xiaobian introduced the basic principles of wireless charging, QI's wireless charging communication standard and the introduction of five wireless chargers for iPhonex.

Wireless charging technology introduction

Wireless charging technology (English: Wireless charging technology; Wireless charge technology) is derived from the wireless energy transmission technology, which can be divided into low-power wireless charging and high-power wireless charging. Low-power wireless charging often uses electromagnetic induction, such as the Qi method of charging the mobile phone, but the inductive type of the wireless charging method of the electric vehicle of ZTE. High-power wireless charging often uses resonant (most electric vehicle charging uses this method). The Power Supply device (charger) transfers energy to the powered device, which uses the received energy to charge the battery and simultaneously supply itself. For operational purposes.

Since the magnetic energy is transmitted between the charger and the electric device, the wires are not connected between the two, so that the charger and the electric device can be exposed without conductive contacts.

Basic principle of wireless charging

Electromagnetic induction

The primary coil has a certain frequency of alternating current, and a certain current is generated in the secondary coil by electromagnetic induction, thereby transferring energy from the transmitting end to the receiving end. At present, the most common charging solution uses electromagnetic induction. In fact, the electromagnetic induction solution does not have much mystery in technology implementation. The local Chinese BYD company applied for non-contact inductive charging as early as December 2005. The patent is patented and uses electromagnetic induction technology.

Magnetic field resonance

It consists of an energy transmitting device and an energy receiving device. When the two devices are adjusted to the same frequency or resonate at a specific frequency, they can exchange energy with each other. This is a technology currently under study by Massachusetts. The research team led by Marin Soljacic, a professor of physics at the Institute of Technology (MIT), used the technology to light a 60-watt bulb two meters away and named it WiTricity. The coil used in this experiment has a diameter of 50 cm and cannot be commercialized. If the coil size is to be reduced, the receiving power naturally decreases.

Radio wave

This is a relatively mature technology, similar to the early use of ore radios, mainly composed of microwave transmitting devices and microwave receiving devices, which can capture the radio wave energy rebounded from the wall and maintain stable DC while adjusting with the load. Voltage. This way you only need a transmitter that is mounted on the wall plug and a “mosquito” receiver that can be installed in any low voltage product.

QI standard wireless charging introduction

The QI standard is: the charger that is produced by the manufacturer of QI. The standard clauses mentioned in the QI standard must be strictly written according to the documents, and processed and produced according to the size of the method.

QI wireless charging communication standard

Under the Wireless Charging Alliance (WPC) standard, the power consumption of wireless transmission is only 0 to 5W. Systems that meet this standard range use inductive coupling between two planar coils to transfer power from the power transmitter to the power receiver. The distance between the primary and secondary coils is typically 5 mm, and the output voltage regulation is handled by a global digital control loop where the power receiver communicates with the power transmitter and generates power. This communication is a one-way communication from a power receiver to a power transmitter by backscatter modulation. In backscatter modulation, the power receiver adjusts the load, thereby changing the current consumption of the power transmitter. These current changes are monitored and demodulated into the information needed to work together on two devices. Communication protocols include analog, digital acoustic ping (ping), identification, configuration, and power transmission. The typical startup sequence that occurs when a power receiver is placed on a power transmitter is as follows:

1) The analog ping from the power transmitter detects the presence of the object.

2) The digital ping from the power transmitter is an extended version of the analog ping and gives the power receiver time to reply with a signal strength packet. If the information strength packet is valid, the power transmitter will keep the coil energized and proceed to the next step.

3) During the identification and configuration phase, the power receiver sends some data packets, identifies them, and provides configuration and setup information to the power transmitter.

4) During the power transmission phase, the power receiver sends a control error packet to the power transmitter to increase or decrease the power. During normal operation, control error packets are sent every 250 ms, and every 32 ms during large signal changes. In addition, during normal operation, the power transmitter sends a power packet every 5 s.

5) In order to terminate the power transmission, the power receiver sends a "terminate charging" message or does not communicate within 1.25s, causing the power transmitter to enter a low power state.

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