There Are AC Power Strips; Why Aren't There DC Power Strips?

Today, I looked under the desk in my den and I saw two AC power strips and one UPS with multiple AC power outlets.  Then, I noticed that only two devices in my office did not have an external AC-DC adapter - my desk lamp and the UPS itself.  But, 11 power bricks and wall-warts - each capable of powering just one device - are plugged into the many AC power outlets supplied by the AC power strips and UPS.

Something is very strange about all this.  I have had the AC power strips for years and years.  But the power bricks and wall-warts come and go so frequently.  How many cell phones, laptop PCs, printers and cordless phones have I had over my 20-year career?  Could it be that my AC power strips have been faithfully serving me for so long?  And, if so, why is DC power so different?

Two things are obvious to me about the role of AC power strips:

1. One device serves multiple products
2. Any device can get power from any AC power outlet.

AC power is interoperable, because (at least on a country-wide basis) it has a fixed voltage.  Our DC-powered products, however, use 5V, 6.5V, 7.5V, 9V, 10.5V, 12V, 14.4V, 16V, 18V, 19V, 21V and other voltages.  They're all different.  Attempts to standard on voltages have failed, because different products optimally work with different voltages. 

One way to deal with the many different voltages that DC-powered products require is to enable power supplies to negotiate the necessary voltage and current levels with the DC-powered products.  Green Plug developed a power communication model that enables any powered device to dynamically negotiate power with the power adapter it is plugged into.

Once the communication link has been made, an unlimited number of power monitoring and control applications are possible.  For example, power adapters can dynamically adjust their output to adapt to changing conditions such as being powered off or having reached full battery charge.  Also, a single AC-DC power adapter can serve power to multiple DC powered devices.

So, instead of throwing away 200+ DC power bricks and wall-warts like I have these past 20 years, I could have used just 2 or 3 multi-port DC power hubs.  Product vendors would not have had to bear the cost of designing, packaging, shipping and giving me the power adapters with the products I purchased.  My wife and I would have had less clutter in our den.  And, the environment would be much better off.

Isn't it time for DC power strips that can dynamically adapt to the power needs of anything that plugs into it?

Comments

[Leslie Weston]

Why Aren't There DC Power Strips?

I think it's largely down to history. When I was young (too meny years ago now!), nearly everything electrical was big and non-portable, and usually ran directly off the mains. Power bricks ("wall warts", I like that name!) were unheard of! So were AC power strips, UPSs, cell phones, PCs (laptops OR desktops), printers, and cordless phones,

It's also down to simple physics. You can convert AC power from one voltage to another very easily: just connect your AC mains into one side of a transformer, and get whatever AC voltage out the other side that the transformer was designed to give you. Then converting that low voltage AC to DC is relatively trivial.

Converting DC to a different voltage always used to be nearly impossible for any practical purpose. In my opinion, Green Plug has a workable answer to that problem. (In case you are wondering, I have no connection with Green Plug.)

My big disappointment is that a Green Plug, as designed, will only work with devices that have been designed to work with it. That means that we will still be living with wall warts for at least another 20 years, until we dispose of the devices that they power.

I don't think anyone could design a power strip "that can dynamically adapt to the power needs of anything that plugs into it" as you ask, simply because the strip would have no way of knowing, or of calculating, the power needs of the devices plugged into it.

-Les.

[Paul Panepinto]

Thank you for your thoughtful comments. Keep them coming!

One thing that may help the migration is that devices themselves don't need to change. Green Plug-enabled power hubs can power legacy products through smart power cables that can negotiate power need on behalf of the product.

[Andy]

Vendors guarantee thier products, so they need a predictable power supply. They also want users to use their product out-of-the box. They want it to be complete. You need USB to download tunes to an iPod, so your power is guaranteed in that case. Maybe the right first step is to get, for example, regular AC adapters for notebooks which also incorporate the standard cell-phone charging function now being proposed. That might proliferate the multi-pupose DC concept to a level of acceptance.