STEVAL-ISB68WA - Formula for deriving capacitor and inductance values

[HWong.6]

Hi.

We are students working on a hardware project. We are designing based on the STEVAL-ISB68WA design and would like to know the derivations which could aid in our design(the formula for calculating the capacitor and resistance values).

Is there anywhere that we can find such information available? Thank you.

[Cristiana SCARAMEL]

Hello @HWong.6​ and welcome to the ST Comunity.

since your question is about a wireless charger application, I moved your thread from the topic Motor Control Hardware to the dedicated ones.

[Peter BENSCH · Accepted solution]

Welcome, @HWong.6​, to the community!

there aren't a lot of resistors in the STEVAL-ISB68WA so I'm guessing you confused it with the inductor coil?

The coil is an important and central part of the Qi receiver, so best would be to start reading AN5535 - Coil selection tool guide for STWLC68GUI.

The datasheet of the STWLC68, section 6.2., could also be very helpful, although it indicates right at the beginning that:

The design of the receiving series resonant circuit, namely the receiving coil (Ls), the resonant capacitor (Cs) and the detection capacitor (Cd), is out of the scope of this document. In principle the resonant capacitor and the detection capacitor are easily calculated via simple equations involving standardized or customized resonance frequencies.

...and references e.g. to documents like:

• The Qi Wireless Power Transfer System; Power Class 0 Specification; Version 1.2.2
• PMA Inductive Wireless Power Transfer Receiver Specification - System Release 1

from e.g. the Wireless Power Consortium.

Good luck!

Regards

/Peter