Wireless Charging: Convenience Over Efficiency?

2013年8月14日
投稿者 NXP

From phones and cameras to notebooks and fitness monitors, there’s a whole array of portable electronic tools helping us to work, play or stay informed. Until recently the only way to charge these devices was to plug them into a mains outlet via an adapter.

Now solutions are appearing that enable charging by simply placing the device onto a pad. The device is automatically recognized, for example using NFC (Near Field Communication), and charging commences, wirelessly. Offering more convenience, wireless charging is a rapidly growing market. But does this convenience come at a price?

During the last decade plug-in chargers have become more and more efficient, keeping overall power consumption to a minimum. Advanced systems, such as those based on the GreenChip IC family, means efficiency during charging has risen to 90% or more, with only a few milliwatts of power lost in standby mode.

By comparison wireless chargers only achieve a typical charging efficiency of around 70%¹. So charging wirelessly seems to introduce a significant waste of energy. However this simple comparison does not tell the whole story and there are factors which may redress the balance.

One of these is multi-standard support. Due to the lack of hardware connectivity standards, a different traditional charger is needed for each and every device. Wireless chargers are more versatile. By supporting multiple wireless connectivity standards, the same wireless charger can be used for two or more devices. This reduces the number of chargers needed, devices which are often left plugged into the mains when not in use and therefore reduces the total power consumption in standby mode.

Another factor is the level of technology in use. Wireless charging is a recent innovation and so there is plenty of opportunity for technological advances. Future generations will almost certainly improve charging efficiency, closing the gap between wireless and wired solutions.

To sum up, the relatively poor energy efficiency of charging wirelessly may be compensated by the need for fewer chargers. And as the technology matures, charging efficiency is likely to improve. However, as a final thought, do these comparisons really matter? Will people put convenience before efficiency, regardless of the cost? The rapid uptake of wireless chargers may offer us a clue.

^1. Wireless Power Consortium