5 min.

From Qi to EVs.
Meeting the Challenge of Wireless Charging and Cable-Free Power Transfer.

We have been able to transfer data without wires for years, even decades but when it comes to charging many portable devices, we are still mostly shackling them to a wall outlet via a small power adapter. However, things are now changing rapidly as new applications emerge and power capabilities move from just a few watts into the kilowatt arena.

While most people associate wireless charging with smartphones, the application base is increasing rapidly, largely enabled by the ability to transfer more power. Now wearable devices, medical implants, IoT devices and other small battery-powered products can be charged wirelessly. As higher power charging becomes more prevalent this will extend to tablets, laptops, drones, robots and more – even electric vehicles at some point.

At the lower power level, the Wireless Power Consortium (WPC), of which Eggtronic is a member, defines the standards. The primary technology is called ‘Qi’ (pronounced “chee”) and this ensures universal interoperability through standardization for inductive charging of lower power devices.

The original Qi standard was published in 2009 covering power levels up to 5W (Baseline Power Profile) and this was extended to 15W (Extended Power Profile) in 2015. Since then there have been discussions about further increases as market demands evolve. Additionally, the concept of authentication has been introduced so that the device to be charged can verify whether the transmitter is trustworthy.

Eggtronic offers a number of transmitter (Tx) and receiver (Rx) ICs (single and multi-coil) for Qi wireless charging. These meet the latest version (1.3) of the standard, including recognition of NFC/RFID cards, while ensuring backward compatibility with the 1.2 version. The ICs support the EPP protocol (5W to 15W) and offer the ability to transfer data-over-power through the coil.

Increasing Power Levels for Wireless Transfer

Enhancing efficiency will become increasingly important as power levels increase – and they surely will as the WPC is already working on Ki – a standard for delivering up to 2.2kW to cordless appliances. At this power level, wireless power is able to operate the appliance, not simply charge it, so wireless charging becomes wireless power transfer. In some cases, a battery may still be incorporated to address load spikes.

Other future standards include the Light Electric Vehicle (LEV) standard for e-bikes and e-scooters as well as the Industry standard for factory automation, including robots of all types.

Simplicity is one of the keys to enhancing efficiency, the more conversion stages, the lower the efficiency. Boosting efficiency will reduce heat build-up and also enable faster charging times which are critical to user adoption of the technology.

Current Qi chargers usually have five distinct conversion stages and can only deliver optimum efficiency at full load - elsewhere efficiency falls away rapidly.

Conventional charger architecture

Eggtronic’s E²Watt technology, however, reduces the functional blocks for a complete charger to a transmitter stage and a receiver stage that acts both as rectifier and non-dissipative output regulator. The design also includes a proprietary data channel with the capability to deliver super-speed gigabit data-over-power and rapid response for accurate output voltage regulation without additional components.

Eggtronic E²Watt architecture

The circuit takes advantage of the low coupling of wireless applications to exploit the leakage inductance, delivering ZVS operation, increasing overall efficiency in every load condition.

The Future of Wireless Power Transfer

With developments such as E²Watt the foundation is being laid for new wireless power opportunities. These include the charging and powering of laptops and larger computing devices and kitchen appliances such as blenders and food mixers that can be used anywhere on a wireless-enabled kitchen work surface.

In the longer term, the improvements in efficiency and power delivery range will also make the charging of electric vehicles without cables much more practical. This, in turn, unlocks benefits in terms of simplicity, reliability and ease of use, with no need to store, remember and plug/unplug heavy and dirty charging cables. In addition, wireless power provides immunity to dirt and water ingress and means there is no risk of accidental, intentional damage to the wires or charging stations, while adding charging to spaces in parking lots makes EV charging much more accessible.

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