RE: Simple analog signaling for an AC adapter
Bob,
Your wife's visible arc problem may very well be due to ESD. I just want to caution you that nothing we are currently doing in this standard will prevent ESD events when a sink is plugged into a source. If the sink has mass and moves relative to the source in a low humidity environment we cannot guarantee no arcing. The output cable itself would be susceptible to ESD discharges even if the source is disconnected from the wires.
I have seen many system problems over the years due to ESD events at the instant of connection between systems and adapters. This event actually occurs prior to actual contact.
Inrush is easily addressed as it is a function of voltage at cable pins and input capacitance of the sink.
I don't agree that potential future Smart Grid forces us to a communication channel right now. What is the AC mains method of communication we are writing into the spec? As long as there is no worldwide Smart Grid universal communication defined a UPAMD spec cannot accommodate it. If accommodating a future Smart Grid is a requirement we should stop development of this standard until this obviously critical requirement can be comprehended by the spec.
Gary Verdun
Technology Strategist
Dell | Office of the CTO
office + 1 512 723 6251, fax + 1 512 723 9929
CTO Office on One Dell Way
-----Original Message-----
From: upamd@xxxxxxxx [mailto:upamd@xxxxxxxx] On Behalf Of Bob Davis
Sent: Wednesday, December 08, 2010 1:51 PM
To: 'Paul Panepinto'; 'arjan strijker'; 'Tomlins, Garry'; 'Piotr Karocki'; 'upamd@xxxxxxxx'
Subject: RE: Simple analog signaling for an AC adapter
All,
A simple resistor could specify a voltage or a power level but not both at the same time. Two resistors on two separate lines can indeed specify independently the voltage and power levels.
Also please consider the requirements for reading that resistor value. The resistor is driven into device that measures its value and makes a logical judgment on usage based on that resistor value. This is most likely done with a processor evaluating a voltage measured with a A/D input to a microprocessor. This still requires an additional one or two signal lines in the cable and a processor.
The only savings is the cost of the processor in the power source that is most likely needed anyway to effectively manage the power source. The smallest processors capable of the job are in the <<$1 and would replace the other power supply control elements with low cost logic.
We still will need to limit the surge current into the adapter, and surge current out of the adapter for safety reasons. We should also be cognizant of the Smart Grid requirements for appliance control. This communications will likely become a requirement within the life of this standard. I am not sure how to deal with the Smart Grid if there is no programmable logic or a microcontroller available to talk on the power-line networking, OSHAN or equivalent. When this is a requirement, I would assume that we will need to convey information to the device digitally or by changing the resistor value is some rapid digital modulation scheme that the device will need to be able to read. The device would then need to change the load or the resistor load in some rapid modulation scheme to get information back to the adapter.
These will need to be specified at the outset of the UPAMD. CAN is of course simpler. IEC 61970 and IEC 61968: Providing a Common Information Model (CIM), necessary for exchanges of data between devices and networks, primarily in the transmission (IEC 61970) and distribution (IEC 61968) domains. See http://www.smartgridnews.com/artman/uploads/1/2010_Smart_Appliance_Report_Zp
ryme_Smart_Grid_Insights.pdf
From this morning's news:
http://www.kron.com/News/ArticleView/tabid/298/smid/1126/ArticleID/7615/reft
ab/536/t/Oakland%20Man%20Critically%20Burned%20in%20East%20Oakland%20Duplex%
20Explosion%20Firefighters%20Say/Default.aspx another house blows up in the Bay Area cause by gas leaks and an ignition source. The actual ignition source has not yet been identified.
I know from experience, that my wife's new MacBook power cube creates enough of a spark when plugged in that she dropped the adapter once thinking it had exploded inside. She was afraid to plug it in again until I had checked it out. It is clearly not surge limited and clearly has sufficient energy in the arc and flash visible outside of the outlet to ignite a combustible natural gas, or in our case propane, fuel/air as in fuel/air bomb. With propane, if the smell agent is not added, it is not easily detected and it pools nicely, being heavier than air, around outlets at normal heights. This of course will not apply to those with all electric facilities.
We will need to deal with the source inrush current issue, which should be worse at 264VAC with a peak voltage of ~380V to charge the input cap with.
This will arc about 1mm depending on altitude and shape. The inputs to power factor corrected supplies will need to be dealt with. The Apple supply is 60W probably avoiding the power factor corrector issue, and is certainly "snappy" with some indication on the blades of metal transfer and black residue. I guess leaving the adapter plugged in one place all the time will avoid this arcing issue being repeated but will certainly reduce the portability. I am not suggesting that the Apple 60W adapter is out of compliance in any way. However consider the news article.
User safety will certainly need to be included in this project. I do not believe we can get away with designs based on history and living on existing certifications based on historical designs.
A transformer, bridge rectifier, capacitor, and identity resistor, are probably not going to be sufficient going forward.
Respectfully;
Bob Davis
Chair UPAMD/P1823
bobd@xxxxxxxx
408.353.5990 desk
408.857.1273 cell
bob.davis.scsi.com Skype
-----Original Message-----
From: upamd@xxxxxxxx [mailto:upamd@xxxxxxxx] On Behalf Of Paul Panepinto
Sent: Wednesday, December 08, 2010 7:52 AM
To: 'arjan strijker'; 'Tomlins, Garry'; 'Piotr Karocki'; 'upamd@xxxxxxxx'
Subject: RE: Simple analog signaling for an AC adapter
Very interesting discussion. In my mind, we want a rich standard, but to "force" the vendors to do something is probably not going to happen. If we try to force vendors into things that they don't want, they will find reasons not to adopt UPAMD and the standard will likely be nothing more than a footnote in history. None of us want that.
Questions:
* Without active communication with the sink (assuming resistor-based signaling), how can you do standby power shutoff? While you can do no-load power shutoff, standby power shutoff will be difficult without requiring a button push to tell the power supply it needs to turn back on.
* Would you need 2 resistors - one for specifying voltage and one for specifying maximum power allowable for the specific connected device?
Regards,
Paul Panepinto
UPAMD Power Subgroup Chair
(970) 461-3077
-----Original Message-----
From: upamd@xxxxxxxx [mailto:upamd@xxxxxxxx] On Behalf Of arjan strijker
Sent: Wednesday, December 08, 2010 7:47 AM
To: Tomlins, Garry; Piotr Karocki; upamd@xxxxxxxx
Subject: RE: Simple analog signaling for an AC adapter
If a power supply has provisions to do the full communication, I do not think that it will be much more expensive to also make it suitable for simple devices.
If the power supply has a complete digital interface on the secondary side to communicate with a sophisticated device, it should hardly cost anything more to detect that a simple resistor is in the device that is being powered.
It can be done with the same pin in the IC in the adapter.
On the other hand, if you have a simple device that does not have any fancy stuff inside and just needs a certain voltage, you need to add a lot of costs (an extra IC) to make it communicate with an adapter that can only work with full communications.
The idea is that a customer has one adapter for several devices. So do we want to make one adapter a little more expensive, or do we want to make several devices much more expensive?
Arjan
-----Original Message-----
From: upamd@xxxxxxxx [mailto:upamd@xxxxxxxx] On Behalf Of Tomlins, Garry
Sent: Wednesday, December 08, 2010 1:20 PM
To: Piotr Karocki; upamd@xxxxxxxx
Subject: RE: Simple analog signaling for an AC adapter
I agree with Lee and Arjan:
This is heading down a path of unnecessary and complex functionality that leads in turn to a complex and expensive implementation. I beleive it will not be attractive to the major equipment ODM's who will need to adopt this if it is to be a success.
We should have a simple analog low cost option.
In my experience in servicing the adapter market for high volume electronics adding a pin, a wire, a resistor a pin to an IC is a big deal - let alone a separate communications system!
My vote is for a simple analog option as described. I believe this will have a good chance of adoption and would be a success for the project.
Garry
Texas Instruments (Cork) Limited, Registered in Ireland under Registration
Number: 294554, Registered Office: Riverside One, Sir John Rogerson's Quay, Dublin 2
-----Original Message-----
From: upamd@xxxxxxxx [mailto:upamd@xxxxxxxx] On Behalf Of Piotr Karocki
Sent: 08 December 2010 11:50
To: upamd@xxxxxxxx
Subject: Re: Simple analog signaling for an AC adapter
I don't agree with Arjan.
We could either "describe current situation" or "shape the future".
Our standard could allow resistor-based "communication", something, something, and full communication (required voltage etc.).
But as one of goals is to allow to connect every device to every supply (and, in near future, connections in form of grid; power hubs, power storage etc.), every supply has to have full communication option. Making provision to understand simpler communication (as resistor based) makes supply more costly.
Say, we have hundred million devices. Half of them - resistor based communication, and tenth of them - full model of communication (4/10 of them some 'in-between' form).
Or, we could force whole 100 000 000 devices to have full model of communication.
But it is the only way to make this full communication cheaper - as it would be "more mass" production. It would be ONE standard...
And the only way to make possible to connect device from 2010 to power supply from 2050 or vice versa. This scenario is not impossible - when standard becomes "grid version"... How often you change wiring in your house?
________________________________
From: upamd@xxxxxxxx [upamd@xxxxxxxx] On Behalf Of arjan strijker [arjan.strijker@xxxxxxx]
Sent: Wednesday, December 08, 2010 12:26 PM
To: Atkinson, Lee; Bob Davis; upamd@xxxxxxxx
Subject: RE: Simple analog signaling for an AC adapter
I agree with Lee that UPAMD should also support low cost devices.
A simple resistor to ground inside the device could tell the adapter what voltage it requires.
More sophisticated device can still do power negotiation etc.
With regards,
Arjan Strijker
From: upamd@xxxxxxxx [mailto:upamd@xxxxxxxx] On Behalf Of Atkinson, Lee
Sent: Wednesday, December 08, 2010 12:08 AM
To: Bob Davis; upamd@xxxxxxxx
Subject: Simple analog signaling for an AC adapter
Bob, here is a quick presentation on the method that HP uses for signaling from the adapter to the notebook. We've had this system in place since 2005 or 2006, and have shipped maybe close to 150million systems that use the common "HP Smart" system (including notebooks, all in one desktops, and small form-factor desktops).
My suggestion is that we at least baseline a system that will allow some scalability of the communication method; at least, allow very low cost devices to connect to a UPAMD power source and work reliably even if their functionality is limited. I'm not sure that a lot of simple devices that would use UPAMD have a need for all the messages that the adapter could provide, or would be able to negotiate variable power consumption. I think we all agree, there is very little precedence for using sophisticated signaling in the common DC powered devices now in the market. Though I agree the simple methods are limited, if we can deliver a scalable solution there will be fewer reasons for the industry to not adopt UPAMD.
Thanks again--Lee