> I have not read the article

Total text was pasted at end of message.

> they are using a relatively high frequency (100s of KHz?) and that
> making an efficient rectifier for those frequencies is difficult. A
> passive diode would have voltage drop, on resistance, capacitance, and
> possibly reverse-recovery to deal with. An active device could be much
> better, but there would still be some power needed to run the control
> circuit and to charge the FET gates each cycle.

They said:

'Sony Corporation ... highly efficient wireless power transfer system
... up to 60 Watts of electrical energy can be transferred over a
distance of 50cm (at an efficiency of approximately 80%, approximately
60% including rectifier).
...  Sony has also drawn on its years of experience developing high
radio frequency (RF) technologies ... to create a new rectifier that
realizes both high speed and high efficiency. The new wireless power
transfer system combines these technologies to realize transfer
efficiency of 60%, even when a rectifier is included. ...

... and enables products such as television sets and mobile PCs to be
efficiently powered, wirelessly.
'

>From this we can conclude:

- Independent of the freuqency used the rectifier is fast ("high speed").

- 60% is highly efficint.

- it takes years of RF development experience to produce a rectifier
that is 75% efficint (60/80)

- 40% energy loss is going to be acceptable to the regulatory
authorities for dec=vices such as TVs and mobile PCs.


No mention was made of any possible health concerns that may be voiced
if such a system was proposed for widespread domestic use.
[Note what that sentence says and not what it could easily be
translated to say.]



    R


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