alignment, but also the lateral and angular alignment as well. Ensuring consistent coil alignment is critical to coil pairing, efficiency
and power delivery. (Fig. 1)
MDT: What are the safety standards governing wireless charging in
medical applications, and what design challenges do they impose?
GG: The same safety standards that govern wired power solu-
tions are also requirements for wireless
systems. You will need to meet medical
safety standards in regards to EMC, EMI,
EMF, etc. There’s a thick alphabet soup of
EMC and safety standards governing these
devices, but the ones you’ll refer to most
• FCC 47CFR part 15B and 18
• EN 61000-6-1, 6-3
• CISPR 11, 14, 16, 22
• IEC/EN/UL 60950-1
• IEC/EN/UL 60601-1
One of the many benefits of wireless
power is that it inherently provides electrical isolation between the patient and the
device. This completely eliminates an issue
which can frequently be a problem for medical device designs.
MDT: Is there a set of standards used to define
wireless charging interfaces?
GG: Yes, there are two main camps today:
• Wireless Power Consortium (Qi
standard), which uses close proximity
inductive coupling as well as magnetic
resonance solutions. You can see more
information at the following link:
• AirFuel Alliance, which is a merger of the Alliance for Wireless Power
(A4WP) and the Power Matters Alliance (PMA), comprised of technologies
from magnetic resonance and inductive
coupling. You can see more information
on AirFuel Alliance at the following
• Other things you should know:
o Inductive coupling has a higher over-
all efficiency and requires a tighter
tolerance for the alignment of Tx and
Rx coils (up to 7mm distance).
o Magnetic resonance has a greater
alignment tolerance/distance, up to
5cm, but also has lower efficiency.
The power transmission frequency used by magnetic resonance solutions is 6.78MHz.
MDT: If there is there more than one set of standards, how does one
choose between them?
GG: It depends on the application and requirements. We at
RRC work with inductive coupling (close proximity) solutions.
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