“Things would be so much easier if I just knew what you wanted!”
A statement that may strike fear into the heart of many a spouse, this simple plea calls for something other than just charging ahead. It suggests a negotiated path as a better way. It suggests the opening of dialog.
Ironically, as hard as this can be for humans to achieve, it has become more and more common amongst our inanimate brethren. All the way back to the negotiation of baud rate between faxes (the original, “Can you hear me now?”), we have imbued machines with the ability to negotiate the terms of their operation.
Often the benefit of this is backwards compatibility, where newer machines may need to co-operate with older ones, and they have to figure out their highest common denominator. Or, when machines need to work together, but where various features are optional, they may need to declare which of the optional features have been implemented.
Many of these scenarios involve start-up conversations that establish a modus operandi, after which they go about their business in the agreed-upon fashion. More complex are systems that continue communicating in real time.
There’s one type of system, however, that’s not complex at all – at least in principle – that people have sought for years to instrument with a communication facility. It’s so simple that – unfortunately – it’s a throw-away item. You probably have a dozen in your house and you never think about them.
It’s the lowly power supply adapter.
The little box that stays plugged in, provides power to your system when needed, and just sort of draws current for no good reason when power is not needed.
The one that, if you don’t keep it near the machine it supports (the “load” – it may be a million-dollar piece of precision electronics, but the power supply isn’t impressed… to it, it’s just another load) when things are unplugged and being swapped around, you may never figure out where it goes again because it’s not marked with a brand name and may just look like another one with different electrical characteristics, and, when you plug it back in, you just hope you don’t hear some kind of popping sound.
As we gradually realize that cheap energy is finite and that wasting it might not be a great idea, it makes more and more sense for a power supply to know a little bit more about what its load mate needs so that it can be a bit smarter about how it manages power.
From an abstract standpoint, it’s not that hard. Anyone can dream up ways to get power mechanisms to communicate. The problem is, they usually add cost, one way or another. And when you’re talking about that annoying extra quarter pound you have to throw into the packing box when shipping out your system, it’s just not worth it. You don’t get paid any more for putting it in the box, so you really want to spend as little on it as possible. Even discussions involving adding a single wire have been rejected as simply too expensive. Or maybe just not worth the necessary brain cycles.
Well, we’ve moved a bit further, and two important notions have been broached: communication between power supplies and loads and standardization of power supplies. The latter can happen without the former, but the former really works a lot better when you have the latter.
One more visible example of the latter was the standardization of power supplies for cell phones. Which not everyone likes. Last time I upgraded my phone, it turned out that the jacks for every accessory had changed, meaning another $150 in replacements for things I’d have to throw away. When grumbling about that to the rent-a-salesguy at the phone store, he leered and said, “Ah, but we like that!” Seriously. He really said that. He should be selling cars instead. But I digress.
Fortunately, I was changing power accessories for the last time. Now we can all use the micro-USB connector, and, in theory, we should never have to swap power accessories again. (Ok, except for Apple users… you will obey your Apple masters…)
But efforts in this area go further than that. There are at least two efforts underway to establish broader standards. One is underway as of this year, called the Universal Power Adapter for Mobile Devices (UPAMD), officially IEEE P1823. The intent is to establish one power supply standard for the range of 10 W – 130 W, along with communications that will provide identification and coordination of power delivery between the adapter and the load. With any luck, this will transcend mobile devices: according to the IEEE Project Authorization Request (PAR), “while intended for portable computing and entertainment devices, this standard may also be used with other mobile devices in use around the office, home or vehicle.”
In addition to UPAMD, and pre-dating it, there is a proprietary effort called Green Plug that defines a protocol that goes further than what UPAMD will do. It’s hard to call this a competing effort, since Green Plug’s Paul Panepinto chairs the UPAMD power subgroup and “… cannot think of any better validation [of] what Green Plug has been advocating for years…”
Green Plug defines a Green Power Processor (GPP) in the power supply, based on Imagination Technologies’ META processor, and a Green Load Processor (GLP) in the load. The GLP manages the Greentalk protocol, which can be embedded in an existing load chip for no extra cost. It’s also available as a macro for integration onto an SoC (for those of you wondering what the heck this all has to do with ICs…). This means that an IC can negotiate its terms with a power supply.
The Greentalk protocol is proprietary and is released only under NDA. The highlights of the architecture are available, however. It’s a typical layered setup consisting of physical, data link, protocol, and application layers. Examples of “applications” given are battery charging, authentication, and power management.
While the details aren’t public, Green Plug describes the capabilities of the protocol as:
- Device identification
- Power supply identification
- Authentication
- Certification class assertion
- Voltage level and maximum current threshold negotiation
- Response to loads that dynamically request different voltages or power ranges
- Requests for power consumption data
- Automatic standby power shutdown and wakeup
- Negotiation of different modes of operation (energy savings, fast charging, deferred charging, normal)
- Response to load request for more power than the UPAMD power adapter is capable of providing
- Support for multiple, simultaneous DC outputs from one UPAMD power adapter
- Low-power radio interface or PLC for connectivity to the Smart Grid.
Green Plug has filed patents on elements of this arrangement, so it remains to be seen what they will donate to the UPAMD effort. They claim that the GLP “is licensed free of charge to strategic partners…” This takes care of the first of the typical requirements of standards bodies, that any IP be licensed in a free and non-discriminatory fashion.
As it is, the Green Plug technology can be used today, albeit with a proprietary result. It’s not clear how many chips are currently being designed with the GLP – it’s easy to get the impression that it hasn’t taken off yet.
One thing that seems a bit scary is the drawing they have of a power supply: it’s big. But – and it’s a big but – they refer to it as a hub. So with one of those beasties, you can use one to connect to multiple loads using simple connectors. That’s certainly handy in the office, where there are an abundance of power-grabbing machines, but a bit much for the one-off use.
They also refer to power adapter designs of varying sizes, ranging from a single “port” and a traveler’s version all the way up to designs for powering green buildings. So it would appear that the technology scales across a very wide range; you just have to talk to them to get the details on how to implement them.
I have to say that I wish all these efforts well. Those annoying little power cubes are something I will be very, very happy to get rid of, whether it’s UPAMD or Green Plug or a combination or something else entirely that gets the job done. And, given intelligent deployment, hopefully costs will ultimately decrease as equipment can ship with less bulk and less weight.
So, now that power adapters and their load mates will be able to have a much more intimate conversation than before, one major relationship hurdle has been crossed: the load can now fully express its needs. That puts the onus on the adapter to meet those needs. File under “B” for “Be careful what you ask for.”
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