Free-position, low-power wireless charging design
Overview:
Aviation headphones are used in airplanes, cars, subways, etc., to facilitate passengers to listen to audio and watch videos to enjoy a pleasant journey.
The aviation earphones are mostly disposable, so the structure is extremely simple, the shape is relatively ordinary, the materials are small, and the annual usage is very large. The number of inquiry can reach several million or even tens of millions, so the cost is very cheap. earphones can cost as little as 10-15 cents. Therefore, they are disposed of as garbage after used, and passengers could take it away for personal use.
Styles can be divided into on ear headphones and in ear earphones.
Functional difference: power, impedance, and sensitivity etc. are also different. Airplane Headphone is mainly customized according to the equipment, place and user used. For example, 1 customer might require 300 ohms impedances , and other customers may need 32 ohms. For adults, the sensitivity may reach 100DB or more.To children, the sensitivity may be around 85-90 DB.
In addition, aviation headphones are not all disposable ones. Some first-class cabins need to be equipped with headphones with good noise reduction, sound quality and functions. So the price will be much more expensive.
Airline Headphones,Airline Earphones,Airplane Headphones,Airline Noise Cancelling Headphones Shenzhen Linx Technology Co., Ltd. , https://www.linxheadphone.com
With the rise and popularity of smartphones, people are becoming more and more dependent on mobile phones. However, limited by the limitations of battery technology, the charging frequency of mobile phones has been drastically reduced with the expansion of functions. From the original two or three days, the charge has dropped to the current day, and even less. The emergence of wireless charging technology makes the charging process more convenient, and also solves the compatibility problem between different mobile phones. At present, the mainstream wireless charging technology mainly includes the following three categories:
1) Electromagnetic induction: a coil with an oscillating circuit characteristic is used to form a set of transmitting and receiving coils in two devices, and an alternating current of several megahertz is added to the coil of the transmitting device, and then the coil of the receiving device is generated. Inductive electromotive force is achieved, thereby achieving wireless transmission of electrical energy. At present, the wireless charging technology based on electromagnetic induction has a transmission power of several watts to several hundred watts and a transmission distance of less than 1 cm.
2) Radio waves: According to the principle of electromagnetics, it is known that the vertical conductor rods pass through the ultra-high frequency alternating current, and electromagnetic waves are formed around them. At a specific frequency, we call this conductor rod to emit radio waves. If a circular coil is used as an antenna and placed in a periodically varying magnetic field of a radio wave, a corresponding current is induced in the coil. The radio wave-based wireless charging technology utilizes the principle that the radio wave energy can be transmitted and received through the antenna, and the AC waveform of the radio wave is directly converted into a direct current in the rectifying circuit and used. The radio wave-based wireless charging technology has a transmission power of less than 100 mW and a transmission distance of up to 10 m.
3) Electromagnetic resonance mode: energy can be effectively transmitted between two objects with the same resonant frequency, and the interaction between objects of different frequencies is weak. Based on this principle, the MIT research team used two copper coils as the electromagnetic resonance device in the bulb test. One of the coils is connected to the power source as a transmitter and the other coil is connected to the bulb as a receiver. After power-on, the transmitter can vibrate at a frequency of 10 MHz, but it does not emit electromagnetic waves outward, but instead forms a strong non-radiative magnetic field around it. This non-radiative magnetic field can be coordinated with the receiving coil for energy transfer. The electromagnetic charging technology based on wireless magnetic resonance technology can reach several kilowatts and the transmission distance can reach several meters.
This article uses TI's BQ500410A chip to form the TX end of the wireless charging system, and the RX end uses TI's BQ51013B. The solution uses three transmit coil arrays to extend position freedom while providing parasitic metal detection (PMOD) and foreign object detection (FOD) to ensure the safety of the charging process.
(Please read the PDF for details)
