Introduction to Wireless Charger and USB

1 Introduction to Wireless Charger

Wireless chargers are devices that use the principle of electromagnetic wave induction to charge, which is similar to the principle of a transformer. There is a coil at the sending and receiving ends. The sending coil is connected to a wired power supply to generate an electromagnetic signal, and the receiving coil senses the electromagnetic signal at the sending end to generate current to charge the battery. There is a lot of radiation during the charging process and the charging efficiency is not high.

A British company has invented a new type of wireless charger that looks like a plastic mouse pad. You can charge your mobile phone or other device by placing it on the pad, and it can charge multiple devices at the same time.

According to the British magazine New Scientist published on the 22nd, this "mouse pad" is equipped with a dense array of small coils that can generate a magnetic field and transmit energy to electronic devices equipped with special receiving coils for charging. The receiving coil is made of magnetic alloy wrapped with wires, and its size and shape are similar to chewing gum, so it can be easily attached to electronic devices.

Wireless charging technology has been around before, but this new invention is more convenient and practical. Mobile phones and other devices can be charged anywhere on the "mouse pad" as long as they are attached with a receiving coil, unlike some previous technologies that require precise positioning. Several devices can be placed on the pad at the same time and charged at the same time. The magnetic field generated by the charger is weak enough to charge the device but will not affect nearby credit cards, video tapes, and other items that use magnetism to record data.

What's next: The technology works by creating an electromagnetic field for parallel micro-charging, a method that has been used in watches and razors in the past but doesn't work effectively for large lithium-ion batteries.

It uses AC induction technology, and both the transmitter and the receiver have corresponding coils to send and receive current signals (of course, it takes some effort to design and add this receiver in the limited space of the receiving device); so there is definitely a radiation problem; and different devices require different receiving ends, which is not convenient to use; and the price is not low.

2 About the Principle of Wireless Charging Technology

2.1 Where does the power of wireless charger come from?

If current passes through the coil, a magnetic field will be generated, and the generated magnetic field will form a voltage, which will generate current, and current can be charged. This is how PowerMat's wireless charger gets rid of the constraints of wires.

2.2 How to control the charging process of the charger on and off

If the current mobile phone chargers can be unplugged after charging, how do wireless chargers solve this problem? This is related to a patent numbered WO09116025A titled INDUCTIVE TRANSMISSION SYSTEM found in the patent database.

According to the database, the applicant of this patent is PowerMat, and the main content is to explain the component structure of the wireless charger and how the charger works. The article mentions that the wireless charger contains a device that starts and shuts down by monitoring the half-rectified wave, which is what we call the switch device of the wireless charger.

2.3 About the structure of wireless charger

PowerMat design diagram

The main body of PowerMat's wireless charger is divided into two parts, one is the charging plate that provides power for wireless charging, and the other is the charging power receiver installed on the mobile phone or other products that need to be charged.

2.4 How PowerMat works

The charging plate and the receiver of the PowerMat wireless charger are inductively connected to each other through a frequency sensing device. When the two are inductively connected to each other, they can start to provide electromagnetic induction charging for the mobile phone. At the same time, the device that PowerMat has applied for a patent and can monitor the half-rectified wave controls the charging switch.

3 Limitations of current wireless chargers

Although this wireless charger looks pretty cool, stylish and convenient, it is a new technology that has not yet been popularized and still has some limitations in some aspects.

At present, wireless chargers cannot achieve the same wide coverage as wireless networks. Although the charging plate and receiver are two parts, they cannot be separated too far from each other, otherwise the charging efficiency will be greatly reduced or even charging will not be possible.

In addition, the conversion rate of wireless chargers is much lower than that of wired chargers. Currently, the maximum conversion rate can only reach 70%, which is also a waste of energy. Of course, this is already a very good effect.

4 USB HUB

USB HUB is a USB interface expander, which is a computer peripheral product that can expand one USB port to 2 or more. The USB interface on the computer is usually on the front panel or the back of the chassis. We know that USB interfaces can be cascaded. A keyboard is connected to the chassis through a USB interface, and several USB interfaces can be made on the side or back of the keyboard. In this way, when using other USB devices, they can be directly connected to the USB interface of the keyboard, which is very convenient. This interface used to connect other USB devices is the USB HUB of the keyboard.

USBHUB is divided into two types: active and passive. Generally, an active USBHUB is required to connect a mobile hard drive.

First of all, this word is divided into two parts: USB and hub.

First, USB is the abbreviation of Universal Serial Bus in English, which means "Universal Serial Bus" in Chinese, also known as Universal Serial Bus.

Second, HUB is what we often call a hub. It is used in a network with a star topology to connect multiple computers or network devices.

Hubs are divided into: 1. Active 2. Passive 3. Hybrid.

1. Kinetic type: It has the function of regenerating and amplifying the signal on the connected network medium, and can make the length of the connected medium reach the maximum effective length. It requires power to work. Currently, most HUBs are of this type.

2. The passive type only acts as a connector and does not require power to work. It is rare in the market.

3. Hybrid: can connect multiple types of cables, such as coaxial and twisted pair.

A hub is an important tool for centralized management of a network. Like the trunk of a tree, it is the gathering point of all branches. A hub is a shared device, which is essentially a repeater. The main function of a repeater is to regenerate and amplify the received signal to expand the transmission distance of the network. In a network, a hub is mainly used for the construction of a shared network. It is the best and most economical solution to directly connect a server to a desktop. In a switched network, the hub is directly connected to a switch to send data from the switch port to the desktop. The use of a hub is flexible in networking. It is located at a star node in the network and centrally manages the workstations connected to the node to prevent problematic workstations from affecting the normal operation of the entire network. Due to the important role of the hub in the network, its selection is also very important.

Four-port USB HUB, can be connected to computer desk lamp, computer fan, MP3, U disk, voice recorder, digital camera, etc.

* One USB port can be expanded into 4 independently working USB ports, each with a power supply of up to 500MA.

Limitations: USB HUB is just an expansion of the USB port. It only diverts the USB voltage when the main board allows it to accept multiple USB devices, but it is very likely to cause voltage instability.