PowerbyProxi > Kunal Bhargava

Defining power ranges for charging ecosystems – what does a universal solution look like?

September 3, 2012 / 0 Comments / 180 / Technical

A wireless power standard is essential to achieving true ubiquity of wireless charging of electronic devices. This is something wired charging has struggled to achieve just ask anyone who has owned a couple or more laptops. Lets not even get started about the iPhone 5 wired charger!

One of the key questions is what is the magic power level or range that will create the most user friendly ecosystems. Ecosystem being defined as compatible transmitters and recievers. Is there an ecosystem for cellphones / smartphones, another for laptops and so on? Or is the real need to have compatibility across the board for all “general” household consumer devices.

The downside of having a one size fits all type of solution is that you will need to trade-off performance and cost against ecosystem expansion from 0-3.5W to 0-100W. A transmitter that can charge 2 smartphones @ 3.5W each only, will look very different to one that can charge 2 smartphones @ 3.5W each as well as a laptop at 90W.

Most of the smaller consumer electronics devices would only require an ecosystem operating in the sub 10W range – this includes smartphones, cellphones, tablets and the like. On the face of it then, a logical demarcation point for ecosystems might be <10W for smaller devices, and 11W to 100W per receiver for larger capacity devices like laptops?

What do you think?

Read more about wireless power technology.

Kunal Bhargava is Engineering Manager for PowerbyProxi

What does loose coupling mean??

August 29, 2012 / 0 Comments / 654 / Features, Technical

Coupling is a term widely used in discussing wireless power systems – it refers to a coupling coefficient ‘k’ which defines how well a transmitter and receiver are magnetically “linked” as a percentage. Generally  something like transformers have extremely high coupling coefficients approaching 100%.

Technically, tightly coupled systems are interpreted as having high or transformer like coupling coefficients while loose coupling is interpreted as systems with low coupling coefficients. There is some debate around the cut-off for high and low – 50% is one proposed transition point.

From a usability perspective I would define tightly coupled as a system which requires some form of mechanical alignment to fix orientation and transmission distance. This can be done via a magnet or a mechanical alignment feature on the transmitter and receiver. A loosely coupled system would allow complete flexibility of orientation / misalignment in a 2D target zone. A 2D target zone would be a planar area such as a matt (i.e. Proxi-2D), which can wirelessly charge devices imbedded with a receiver that is a few cm above it.

Systems like the Proxi-3D which enables receivers to work in a  three dimensional target zone with an omni-directional receiver are what a user may call as beyond loosely coupled!

In my opinion the usability definition is more relevant for anyone buying the system as really the technical definition is really just a means to an end – the end being ensuring customers don’t have to carefully align their devices with a wireless charger.

Kunal Bhargava is Engineering Manager for PowerbyProxi

Do EMC radiation standards comprehensively cover wireless charging solutions?

August 1, 2012 / 2 Comments / 242 / Technical

EMC radiation standards are used to qualify electronic devices against interference with other electronic devices. A piece of wire that has a current running through it will generate electric and magnetic fields – “H-field” emissions measure the magnetic component and “E-fields” emissions measure the electric component. EMC radiation standards ensure that these fields do not interact with other electronic devices to impair their operation.

EMC radiation standards were really designed to control and limit the amount of interference in long distance radio communication. The current standards regulating EMC radiation have been great at regulating these devices, however you now have a new type of electronic device that intentionally generates magnetic fields – those that use wireless power. Such electronic devices were never foreseen when these standards were written.

Consequently, there is one potential aspect of wireless power solutions (read more about wireless power here) which is not currently being regulated. This is the amount of electromotive force (EMF) that can be generated in a device which is in very close proximity. EMF is basically a fancy term for voltage! Electronics are sensitive to over-voltage (some more than others) and over-voltage can cause permanent damage to devices.

Sure there is a limit on how much “H-field” you can emit however these fields are typically measured using an antenna at a few meters or feet away from a device under test. The reading from the antenna and compliance to limits will not really tell you whether your shiny new smart-phone placed on your laptop’s wireless power supply is going to fail.

But hey at least your wireless power supply doesn’t mess with your FM radio…

Kunal Bhargava is Engineering Manager for PowerbyProxi

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