How does a Wireless charging work? This process allows users to charge their phone anytime, anywhere, without having to plug in a power outlet. This means that wirelessly enabled smartphones and other devices can be charged by simply placing them on, for example, a coffee table, or even more complex machines such as electric vehicles can be simply parked in a garage or wirelessly charged. Enable the road to charge. It eliminates all of the security issues associated with rope-based charging and opens up new freedom for users.
Wireless charging dates back to the late 19th century, when Nikola Tesla developed the Tesla coil, which should help wirelessly transmit power, and the experiment failed to reach its goal, raising interest in the field. And more people are starting to research ideas. You can view this experiment to build a Mini Tesla coil that wirelessly transmits power.
How does wireless power transmission work?
Just like wireless communication systems, wireless charging is achieved through the action of wireless energy transmitters and receivers. A wireless charging transmitter, commonly referred to as a charging station, is connected to the electrical outlet and transmits the energy provided through the outlet to the receiver, which is always connected to the device to be charged and placed near the wireless charging station.
The following is a block diagram depicting the components of the wireless charging system and charging process:
As previously mentioned, wireless charging utilizes the magnetic induction principle used in power transformers, generators, and motors to cause current to pass through the coil causing a change in the magnetic field around the coil, thereby inducing a current in the other coupled coil. This is the principle of transferring electrical energy between the primary and secondary coils in a power transformer, even though they appear to be electrically isolated. In wireless charging, each component (transmitter and receiver) that make up the system has a coil. The transmitter coil can be likened to the primary coil, and the receiver coil can be compared to the secondary coil of the power transformer. When the charging station is plugged into an AC power source, the rectification system rectifies the power supply to DC, and then switches the system to take over. The reason for the switching is the ability to generate the varying magnetic flux required to induce a charge in the receiver coil.
The receiver coil collects the input power and passes it to the receiver circuit, which converts the input power to DC and then applies the received power to charge the battery.
As described above, power transfer occurs when a magnetic flux generated by establishing an alternating magnetic field in a transmitter coil is converted into a current in a receiver coil. The amount of current generated depends on the amount of magnetic flux produced by the transmitter and how much magnetic flux the receiver coil can capture. The magnetic flux captured by the receiver depends on the “coupling coefficient”, which is determined by the size, distance and positioning of the receiver coil relative to the transmitter coil. This means that a higher coupling coefficient will result in higher energy transfer. To increase the likelihood of higher coupling factors, some wireless charging stations are designed with multiple transmitter coils, as shown in the following figure.
Wireless charging standard
So there are different type of designs and development of wireless devices. Currently, different organizations are promoting two different wireless charging industry standards.
- Meet the standard
- QI standard
The standard is promoted by the Wireless Power Alliance (A4WP). On the other hand, the QI standard uses wireless coupling between the coils and the Rezence standard to achieve wireless energy transfer. The transmitter and receiver coils are always designed to operate at slightly different frequencies, as it is believed that this setting provides more power. The QI standard is promoted by the Wireless Power Alliance, including members such as Apple Inc, Qual
You can consider the trade-off between EMI, efficiency, and alignment freedom between the two standards to choose the wireless standard that best suits your application. However, some wireless charging stations are designed to support both standards, which provide high interoperability between devices.
Simple wireless charger design
The following factors should be considered before building a wireless charging system.
- Standard: When equipped with wireless charging function, the first thing to do is to choose the wireless power standard that suits the device and its use case. Some charging systems are based on a variety of standards.
- Coil Selection: The next step is to select the appropriate coil type and coil geometry to suit the use case. The supplier supplies these coils in standard specifications, so the appropriate coil should be selected according to the recommendations of the data sheet of the wireless charging transmitter IC to be used.
As mentioned previously, the wireless charging system includes a transmitter and a receiver. Below is a schematic showing the transmitter design.
The constituent transmitter has three main components; the power supply, the transmitter coil and the switching circuit. The power supply is usually from the DC of the rectified AC. After rectification, the switching circuit is operative to generate an alternating signal for generating a varying magnetic field to induce current transfer from the transmitter to the receiver through the transmitter coil.
The design of the receiver is similar to the design of the transmitter, except that the actions occur in the reverse order.
Product where these are involved
Wireless charging used in these following devices
- Smartphones and wearables
- Notebook and tablet
- Power tools and service robots, such as vacuum cleaners
- Multicopters and electric toys
- Medical equipment
- Car Charging
In addition to fancy reasons, you should use wireless charging, for example, without plugging in the device and without plug compatibility issues, wireless charging provides dangerous safety associated with direct connection to the power supply. In addition, it is reliable in more demanding environments, such as drilling and mining, and enables seamless mobile charging. Finally, wireless charging eliminates the tangles and other clutter caused by the wires. We have just removed the face of wireless charging from several novel applications, each of which is considering the future and should seek to use wireless charging as one of the ways we can charge battery-powered devices in the near future.