FAQ

What is the maximum distance between transmitter and receiver?

Currently the Qi standard allows a maximum distance of about 8mm There are plans in standardisation to increase the distance to about 50mm with the resonance upgrade. Proprietary inductive solutions can reach about 50 to 60mm with a reduced efficiency. Resonant systems can cover wider distances. But be aware of EMI/safety/approval challenges which come with larger distances.

Which power can be transmitted with WPC coils?

If they are used in a QI standard application it is up to 15W. The power management IC will manage the power transfer. The coils in general are capable of much more. WE offers standard wireless power coils up to 300W and customer specific solution up to 11kW.

What is the operational frequency for Qi transmission?

The transmitter/receiver operates in a range of 100 – 205 kHz.

Any problems (heating) with foreign objects?

Qi standard has a foreign object detection (FOD) integrated in the standard. In case the FOD feature between transmitter and receiver detects a foreign metal object, the power transfer will be terminated due to safety reasons.

Are transmitter and receiver standardized?

Qi standard specifies quite detailed the transmitters. This makes sense as the transmitter has to work with any Qi certified receiver. On the receiver side the device manufacturer has more freedom in creating a receiver coil. What they only have to ensure is that their receiver works with all Qi transmitters in the market.

Is the data communication of WPC the same as Near Field Communication ?

Data transmission in Qi Standard is not related to NFC. NFC is working in 13MHz Band and WPC operates 100kHz- 205 kHz. Therefore there is no interference possible. WE offers combined receiver coils which consists of a wireless power coil surrounded by a NFC coil.

Why should the Q value of the coils be high?

The better the Q value is, the larger the distance can be between the transmitter and receiver coils and the better the efficiency of the wireless power transfer.

Are application notes available for WPC coils from Würth Elektronik?

What is the purpose of the ferrite?

Main purpose is to concentrate the magnetic field between Tx and Rx and to shield e.g. a possible PCB underneath. For the transmitter coils the Qi standard specifies the thickness and material of the ferrite. The ferrite on Rx and Tx coil helps as well in terms of EMI/EMC/safety.

Are ICs available which support more than the 15W in Qi Standard?

Currently there is no standard for >15W availabe. The WPC has working groups to define standards for up to 100W and up to 2,4kW. Yes, our standard coils can support higher power (up to 300W).

Can you offer a wireless power evaluation kit?

Yes, 760308MP available via sales or online for € 149.-

Can the same coil act as transmitter and receiver?

In general, all our wireless power coils can act as transmitter or receiver. We have currently our products developed following the Qi standard of WPC which differentiates between transmitter and receiver coils. In a proprieaty solution it is possible to use the same coils as receiver and transmitter. It is only depending how the power management logic (circuitry) is done.

Is WE offering customer specific wireless power coils?

Does wireless power work in rotating systems?

Yes, you can put e.g. a transmitter on the static part of a system and the receiver on the rotating part. WE can do customer specific coils with central holes for rotating systems.

FAQs

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