| 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:
I think I sense that extended communication
is wishful; I agree that would be a nice addition for the future.
However, I still have cost concerns
to this when we absolutely need this communication in order to get some
power from the supply.
Therefore I would vote for a solution
that would not restrain communication in any way, but that we also find
a way for simple and low-cost power adapters to be used, without communication
ability.
Adding smart-grid integration would
make sense, although this, at this time, is more focussed on big power
users like aircons, water heaters and other luxury type of products. When
the device is smart enough and goes to a power down or standby mode whenever
possible, there is no need for smart-grid to intervene, I do not think
that EISA 2007 will go so far that even laptop computers printers and networks
will have to go down when actually being used; I think it will remain at
aircons, heaters, waterheaters, (dish)washing machines and (public)lighting;
most of this type of equipment consumes a lot more than what the adapter
in question can provide.
It is not difficult anymore to get below
100mW in stand-by, it is just a matter of price at this time, in a couple
of years I foresee most adapters to be able to draw less than 50mW in no-load.
This is a great achievement from most
power supply manufacturers and power/PWM IC design houses. Destroying that
by adding another 100mW or more, just to listen or communicate in order
to go down to an overall power down for a period in time does not make
sense to me.
Would the overall energy usage really
bring us below 50mW? If so, is this enough to justify the extra waste that
we add? (controller, manufacturing of that controller, distribution of
that controller, extra wires for the communication needs).
Ecodesign in Europe already announced
to be looking at the total picture, including design, manufacturing, testing
and distribution involved in putting any product to market. (total green
concept or cradle-to-grave)
As I mentioned in one of my earlier
comments, having a power supply that could also perform as a bridge to
Power Line Communication or Smart-grid could be a great addition and would
make sense in the future when the different types of network communication
will get more and more integrated into each other to increase and secure
the total available bandwidth.
Best regards,
Rene Koch
Some additional suggestions regarding "green"
capabilities.
A) Support for Load Shedding / Demand Response / Dynamic Demand
functionality.
The power adapter-to-device communications should support primitives
for demand shaping, incorporating mains-side interface/definitions to
support the applicable protocols and standards. To reduce cost, and
avoid restrictions over the multiple mains standards, the specific
load-shedding support should remain optional.
Use cases:
(1) The utility generates a load-shedding request that gets coupled
into the home network. Compatible UPAMDs (the ones implementing a load-
shedding protocol mains-side) send the request across to the connected
device. The connected device responds by modifying its power
requirements or removing them altogether. (The user could set the
power-saving settings similarly to existing battery-conservation
settings in laptops).
(2) The user requests device charging only during off-peak (e.g., low-
cost) utility periods. A home-based controller instructs compatible
UPAMDs to provide power only during those periods (note that this
might not require intervention from the device side, i.e., forced
power-shedding.)
(3) The user connects an specific UPAMD (to be used with a different
device) to a computer and configures its power-saving capabilities
through a local program or web page. A real-time clock inside the
UPAMD indicates at what times it will provide power to the attached
device.
Possible applicable standards: IEEE P2030, IEEE P1547.8, ISO/IEC
14543-3 (KNX), IEEE 1815, IEEE P1901, IEC 61334, ITU G.9972.
The most relevant standards seem to be the ones from the KNX
association.
Industry standards: HomePlug Command & Control, HomePlug GreenPhy,
http://www.prime-alliance.org/
Related technologies:
load shedding lighting ballasts: http://www.lrc.rpi.edu/researchAreas/pdf/LoadShedBrochureNYS.pdf
,
home control: http://www.Insteonsmartgrid.com/about-us.html )
B) Sleep capability requirements.
To reduce power consumption, the mains-side of the UPAMD should
disconnect itself from mains power for pre-defined periods of time
(e.g., 5 sec, 10 sec or even longer). When not in use, the excess
capacitive power reserve should be able to power the UPAMD electronics
for a considerable period of time. The mains-side switcher can be
turned-off (for several seconds) in those conditions providing near-
zero power consumption. (A slow-blinking LED, for power reasons, can
indicate this condition.) This would make it much easier to satisfy a
<100mW standby mode.
Alternative 1: If trickle power is provided to the powered device, the
UPAMD only powers-up to keep trickle-power regulation.
Alternative 2: The UPAMD only provides trickle-power to the connected
device for a brief period every n seconds.
Alternative 3: The sleep period becomes longer if the device has not
been used for an extended period of time (a reserve super cap can
provide sleep power under such conditions).
Note that EMC issues can arise due to this start/stop condition, and
additional restrictions (e.g., a soft start-up envelope) might be
required to avoid these.
Cost considerations: given that some intelligence is to be required to
provide the communications layer, the additional controls required to
implement this capability would be minimal. Alternative
implementations (e.g., timers, or voltage comparators) can allow for
further cost reductions.
EB
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