Wireless charging can have real impact in medical devices: Page 3 of 3

April 22, 2015 //By Bill Schweber, EDN
Wireless charging of personal devices such as smartphones, laptops, and tablets is a hot topic. Several standards are competing to make it possible to just place the device on a table's surface or charging pad, and sit back while energy is transferred without the need to connect to a discrete, physical cable.
Assessing the effectiveness is not trivial. I often wonder "how did they measure that?" since acquiring meaningful, trustworthy data in leading-edge research is often as big a challenge as the experimental set-up itself, and it is not necessarily just an issue of needing advanced, expensive test instrumentation. In this situation, the researchers noted that the obvious approach of simply attaching leads to the receiver would affect the system's inductance and associated EM fields.

Instead, they devised a simple and clever instrumentation approach of using the receiver to power a small circuit within the implant which, in turn, flashed a tiny LED at a rate proportional to the received power. An optical fibre then conveyed the LED output to an external photodetector and circuit which sensed and counted the flash rate (once again, the RF-free nature of optical fibres opens up new approaches to many problems)very nicely done, indeed.

What's your view on the desirability or viability of wireless charging for consumer products? Would you ever think that transfer efficiency of less than one-tenth of one percent would be sufficient and welcome in a unique application? What power-transfer efficiency would you accept in your application?

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