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Edgar,
I agree that it is detrimental if we have some various adapter classes, but:
I believe it is almost impossible to not have incompatible combinations of adapters and devices due to power requirements. The biggest cost factor for a mains powered adapter is the power rating. It is also a weight and size factor affecting portability and usage. I don't think people will accept cost, size or weight of a 130W UPADM adapter to power a device like a portable radio or charge a micro RC model helicopter. I think this is not a big issue if handled properly.
With a good UPADM standard, it should be the possible to use any UPADM adapter as long as it supplies the minimum power needed for the device. Everybody (Almost) will understand that adapters need to come in different sizes. This is not difficult as long as we keep adapter power rating the only variable the user has to think of. It could be part of the standard that power rating of adapter and consumer is easy to locate, is concise and has a common labeling. And imagine a sales situation where someone walks into a store in need for an adapter: The 130W 'brick' will always work, (un)fortunately (for the store), it is the most expensive one.
To save cost on the consumer side the UPAMD could support a basic analog mode. Imagine having two separate communication wires in the UPAMD cable. When in analog mode they are used for sensing a simple analog network in the consumer. Certain properties (resistance, zener diode voltage etc.) is detected by the adapter to select correct output voltage, current limits etc. Further, as a transition solution, a UPAMD adapter cable with built-in analog network could be built for a very low cost to be used with legacy equipment lacking built-in UPAMD support. This way existing equipment can use the new adapter.
For more advanced consumers the UPAMD would use the two communication wires for duplex communication overlayed (or time multiplexed) on analog voltage feedback (aka 'Kelvin clips') for reduced cable cost, better regulation and other benefits as stated in my previous mail.
This way a full digital communication is present in every UPAMD adapter from the beginning, without requiring a major revision for purely analog devices. And every UPAMD adapter will work with all devices, as long as the power requirements are met as described above.
Per Hassel
Fra: upamd@xxxxxxxx på vegne av Edgar Brown Sendt: to 08.07.2010 17:43 Til: LEI / Rene Koch Kopi: upamd@xxxxxxxx Emne: Re: Potential Goals of the group for discussion Rene,
I see two conflicting goals in removing communications from the requirements: (1) universality (one adapter fits all) and (2) low-cost (a.k.a. analog) simplicity. Although a properly designed analog solution can nearly always be the lowest _manufacturing_ cost one. It would probably be the most complicated in terms of flexibility. As an analog and digital designer, I am always confronted on where each technology fits best. I can clearly remember the cases in which, after a grueling analog design has been put together, I have wished to have gone digital instead. While the converse is rarely true.
These are the issues as I see them:
- A single plug fits all: If a UPAMD plug is present in an adapter and a device, we want the consumer to correctly assume that the two can be plugged together. Having a class of adapters that would not power some subset of devices would be very detrimental to this goal (this also applies to power levels, B.T.W.). This is also one of the strongest arguments against the highly non-standard and irritating family of barrel connectors.
- Providing enough flexibility through analog means, although possible, would _probably_ complicate the circuit enough that a comparable digital solution would end up being cheaper in the short (and long) term. (And clearly cheaper from a design stand point.)
- A properly designed (and adopted) standard would create industry demand for the right low-cost semiconductor solutions. As a sample, take a look at the prevalence of ARM cores in TI's family of PMBus PWM power controllers. An ARM core would be overkill for our intended application, but it is not out of the question in the mid-term. A power supply that has to satisfy multiple requirements, such as power-factor correction, low-power consumption, stand-by modes, etc., presents enough functionality that an all-encompassing integrated digital solution would probably be preferable.
And while writing this I thought of a way to accomplish some of the conflicting analog requirements. A simple feedback mechanism, in which the device requests power from the UPAMD through a simple lower/higher analog signal (essentially a slow remote regulation loop) could satisfy some of these conflicting requirements. An AC signal (e.g., AM-modulated voltage feedback) can close the device-adapter loop. Only requiring simple diode/resistor/capacitor circuitry to extract the return feedback signal. And this would not even require extra wires in the connector. This choice would somewhat complicate any communications between adapter and device, but it still can be done with decades-old modem technology.
Regarding 'greening' technologies. Although it is true that large equipment is the easiest target for conservation efforts, do not underestimate the amount of power being wasted on tens of unused but plugged adapters in each home and thousands in each office building. Also don't underestimate that any progress towards these types of standard would also ease the development of equivalent standards in directly-plugged AC devices. Any progress to be made in removing power through greener adapters I believe to be worthwhile. Especially in a standard that we hope would be still useful a few decades into the future. Edgar Brown
On Jul 7, 2010, at 4:51 AM, LEI / Rene Koch wrote:
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