There should be at least two pieces
of information that need communicating: (a) voltage level and (b) maximum
current limit. If you are able to use a 100W power adapter with a 15W
load and something goes wrong where the load tries to draw more than 15W, it
would be a very good idea if the power adapter is smart enough to know that the
load is not rated to accept the higher current/power and refuse to provide more
power than the load is rated to accept. Given that at least 2 pieces of
information need to be communicated between load and power adapter (voltage and
maximum output power,) an analog circuit may not be simpler or lower cost than a
digital processor.
Only one controller is all that is
needed (not two), as long as the proper isolation circuitry is in place for
both primary and secondary control.
I agree that we should consider
all good options at this point for analog and digital communications.
Regards,
Paul Panepinto
From: upamd@xxxxxxxx
[mailto:upamd@xxxxxxxx] On Behalf Of LEI / Rene Koch
Sent: Tuesday, August 17, 2010 1:04 AM
To: 'UPAMD'
Subject: Possibility for low cost voltage setting
I would still
like to propose to keep the possibility open for simple low-cost solutions.
Which means for
example a simple analogue level of the communications connection in order to
set the required voltage of the load; any digital signal on that communications
connection would overrule the analogue signal. This will of course not be
possible if we choose to use a communication scheme over the power lines.
General power
adapters have a controller on the primary side, which uses a feedback signal
from the secondary (DC) side to adjust its operation level. Mandating digital
communications on the secondary side would mean an additional controller on
this secondary side, with additional requirements of operating voltage
(supplied by the adapter itself) and control components.
I believe the
impact of this is just too large for general manufacturers to justify; unless
the requirements become mandatory by governments.
(+70% cost for
a 20W adapter; +40% for a 60W and about 25% for a 100W adapter)
Since I do not
believe that standard commodity products will come available with a double
power connection, I believe this has a major impact to the success of the
UPAMD.
This will also
allow for a transition period, where mobile device manufacturers will learn to
appreciate our efforts and where costs of cabling and connectors will be
reduced due to large scale usage.
It does not
have to interfere with or restrain anything that we are trying to achieve; it
can just be an additional requirement.
Best regards,
Rene