Wireless battery charging is being used in many battery powered products like smartphones, smart watches and a host of other small electronic products.
Initially aimed at smaller electronic products, wireless charging technology is also being used for larger items including vehicles and many other items as well.
Wireless charging relies typically utilises inductive coupling between two circuits to transfer the power from one circuit to another. As no direct electrical contact is made it is considerably more convenient and also does not rely on connector contacts that can become worn and unreliable after many charge cycles.
Although the initial take-up for wireless charging was slow, it has now been adopted by many manufacturers, with most of the large smartphone companies providing it as standard on many phones.
Wireless battery charging basics
Wireless battery charging uses an inductive or magnetic field between two objects which are typically coils to transfer the energy from one to another. The energy is transferred from the energy source to the receiver where it is typically used to charge the battery in the device.
This makes wireless charging or inductive charging ideal for use with many portable devices such as mobile phones and other wireless applications. However they have also found widespread use in products such as electric toothbrushes where cordless operation is needed and where connections would be very unwise and short-lived.
The system is essentially a flat form of transformer - flat because this makes it easier to fit into the equipment in which it is to be used. Many wireless battery charging systems are used in consumer items where small form factors are essential.
The primary side of the transformer is connected to the energy supply that will typically be a mains power source, and the secondary side will be within the equipment where the charge is required.
In many applications the wireless battery charging system will consist of two flat coils. The power source is often contained within a pad or mat on which the appliance to be charged is placed.
There are several key concepts associated with the transmission of power wire-lessly. Aspects like efficiency, diameter of the coils, frequencies used and the like all have a bearing on the way the wireless charging works.
A further aspect of wireless charging that needs tob e given careful attention during the design is that of screening and ensuring that the wireless power transfer does not interfere with other electronic circuits in the equipment, especially that receiving he power.
Wireless battery charging advantages / disadvantages
As with any system, there are both advantages and disadvantages to wireless battery charging systems.
|Advantages & Disadvantages of Wireless charging
Wireless charging standards
There are several wireless charging standards that are being developed or already on the market.
- Qi:  : The Qi wireless charging standard came to market first and it has also taken a dominant position. It has been adopted byt he major phone manufacturers and virtually all wireless chargers used for domestic and many other applications use this standard. It is basically what is termed and inductive system using a relatively low frequency (between 110 and 205 kHz for the low power and 80 to 300 kHz for the medium power) for the power transfer.
Read more about . . . . Qi wireless charging.
- A4WP:  : The A4WP wireless power standard was developed a little later than the Qi standard. It uses resonance techniques along with a higher power transfer frequency of 6.78 MHz for the power, and 2.4GHz for the control signals. It also allows simultaneous charging of multiple devices.
Wireless charging has now become a mainstream technology. Initially it was a novelty, but with its applications and advantages becoming recognised, it has now become a mainstream application. It is anticipated that wireless battery charging will become very widespread, if not the most common method.
With standardised interfaces and techniques, only a single wireless battery charger will be required to charge a variety of items. No longer will a whole myriad of chargers be required. Also reliability and convenience will be improved as it is far easier to place the item to be charged on the charging mat, rather than having to use a small connector.
Although the efficiency of wireless battery charging is less than that using direct connections, the added intelligence could reduce the end of charge current, thereby reducing the overall power consumption as many normal chargers are left connected even when they are not charging.