I’m working on a small wireless charging project and exploring different coil options. I’ve mostly seen traditional hand-wound or PCB coils used in DIY builds, but I recently came across some ready-made wireless charging coils from AK Stamping that are designed for Qi applications.
I’m curious if anyone here has experience using these types of pre-manufactured coils instead of winding your own or using basic PCB coils.
A few specific questions:
Have you noticed any differences in efficiency, coupling, or EMI performance compared to standard wound coils?
For a low-power Qi system (around 5W–10W), what type of coil would you recommend?
Any tips for selecting the right coil specs to match a controller/driver IC?
I’m still in the early design phase and trying to understand what direction makes the most sense before ordering parts.
Would really appreciate any advice or real-world experience. Thanks!
It is typically wiser to use pre-made coils for a 5–10w **qi** setup. Less tuning discomfort results from their greater consistency in shielding, DCR, and inductance. Efficiency is largely determined by low DCR, adequate alignment, appropriate ferrite backing, and L value at working frequency, not merely by the coil’s manufacturer.
Correctly tune the resonant caps and align the coil’s inductance and Q range with your qi controller datasheet. Using a qi-rated stamped coil will save you time troubleshooting if this is more than a hobby project.
COTS qi coils use litz wire and ferrite back plate. Without the back plate it’s hard to comply with EMC regulations, and the litz wire reduce ac losses. AFAIR there is also defined sizes of the coils in the qi standard. It’s been a while, but I think there’s application notes from Wurth on this topic
I’ve experimented with both hand-wound coils and pre-manufactured Qi coils in a few small prototypes. In my experience, the ready-made coils can actually save a lot of time during development because their inductance and resistance values are usually more consistent than DIY wound coils.
For a 5W–10W Qi system, I’ve seen many people use pre-tuned coils that already match the typical inductance range expected by most Qi transmitter/receiver controller ICs. Efficiency differences are usually small if the coil specs (inductance, Q factor, and resistance) are within the recommended range of the controller chip.
One thing that helped in my case was checking:
• Inductance (µH) and tolerance
• DC resistance (lower is usually better for efficiency)
• Coil diameter vs. alignment requirements
• Shielding layer or ferrite backing for EMI control
Some pre-manufactured coils from suppliers like AK Stamping already include ferrite backing and are designed specifically for Qi alignment, which can make integration easier compared to basic PCB coils.
If you’re still in the early stage, I’d recommend checking the reference design of the controller IC you plan to use and selecting a coil with similar specs to the recommended one. That usually avoids a lot of tuning later.