Wireless Power Efficiency

The energy consumption of battery chargers has two main contributors: charging efficiency and standby power consumption.

STANDBY POWER CONSUMPTION

Unfortunately, many people leave the chargers and cradles connected to mains power when the charger is not used. The standby power consumption (also called “no-load power consumption”) is significant. A simple calculation shows that power consumed in standby mode is about the same as the energy consumed when loading the battery.

One of our main design goals was, therefore, minimizing standby power. Go low!

We did go low. We have demonstrated a system with only 0.0001 Watt (100 µW) standby power consumption. And that is probably not the bottom.

CHARGING EFFICIENCY

The other contributor is charging efficiency. Our wireless chargers have the same ingredients as a wired charger (an AC-DC adaptor plus charging electronics) and one additional ingredient: the copper wire between adaptor and the mobile phone is replaced with a wireless link. It may look obvious that this link is not as efficient as a copper wire (what can beat a copper wire?), but optimization of the complete power transfer chain (including AC/DC conversion and battery charging electronics) can make the transfer as efficient as a wired charger. 

Kalyan Siddabattula compared the power losses in a wired and wireless charging system and found that wireless chargers can be made as efficient as a wired charger when you integrate the charger functionality into the wireless power receiver electronics.

Read more about this analysis in: Why Not A Wire? The case for wireless power

From the Qi Blog

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