It seems that the discussion of this has gone away from the initial contribution, and may have generated an unintended
consequence, largely because “PD turn on” is a loosely defined concept.
If I take the concept from
Kousi’s contribution – that is that the PD load is drawing at its full capacity the language that is being proposed now would REQUIRE a PD to activate its load anytime the voltage at the PI is greater than
Voff. (the current language doesn’t have this problem only because it is broken in the first place).
That would put standard compliance in conflict with any power saving mode which put the PD (load) circuitry into a low power quiescent (arguably not turned on) state.
The original suggestion in
Kousi’s contribution didn’t have this issue because it set the recommendation in the negative, and it was not a hard requirement – “the PD should not turn on, …”
I liked this concept because it was a recommendation, and things related to what the PD does behind the PI are out of scope for the standard, so they should be recommendations – not requirements.
However, I don’t see how that will work in this section 33.3.7, which reads:
“The PD shall turn on at a voltage less than or equal
to VOn. After the PD turns on, the PD shall stay on over the entire
VPort_PD
range. The PD shall turn off at a voltage less than
VPort_PD
minimum and greater than or equal to
VOff.”
It may seem a little silly, but maybe to fix this we can use some more precise and descriptive
language than, “the PD shall turn on”? - any thoughts on just what we mean here in terms of behavior AT THE PI?
Surely a PD that is in a standby mode waiting for the user or other sensor to ‘turn it on’ still meets this criterion, and should not fully turn on simply because the power supply is ready.
I’m throwing this out there because I don’t yet have succinct definition of what we mean
– “shall be capable of providing full current to its load’? “shall provide a stable voltage at its output?”
Any thoughts?
George Zimmerman
Principal, CME Consulting
Experts in Advanced
PHYsical Communications Technology
george@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
310-920-3860
(PLEASE NOTE NEW EMAIL ADDRESS.
THE OTHER WILL STILL WORK, BUT PLEASE USE THIS FOR CME BUSINESS)
From:
Dan Dove [mailto:dan.dove@xxxxxxxxxxxxxxxxxx]
Sent: Tuesday, March 17, 2015 9:14 AM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] PD Load turn on
Minor editorial suggestion to bring the language into IEEE parlance.
"The PD shall turn on at a voltage
greater than Voff and less than or equal to Von or VPort_PD(min) whichever is
greater."
Dan Dove
Chief Consultant
Dove Networking Solutions
530-906-3683 - Mobile
On 3/17/15 7:49 AM, Miklós Lukács wrote:
Hi All,
I like the most the last version below:
“"The PD shall turn on at a voltage greater than Voff and less than or equal to Von or VPort_PD(min) whichever is more".”
Thanks,
Miklos
From: Yseboodt, Lennart [mailto:lennart.yseboodt@xxxxxxxxxxx]
Sent: 2015. március 17. 13:52
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] PD Load turn on
Hi all,
While trying to review this text I noticed there is a difference in behaviour for Type 1 & 4 and Type 2 & 3 PDs.
Specifically it is not clear to me what a Type 2/3 PD should do with PI voltages between Von and Vport_PD(min). The only "shall" that applies says "turn off".
We can fix this by replacing (in 33.3.7.1):
"The PD shall turn on at a voltage less than or equal to Von."
by
"The PD shall turn on at a voltage less than or equal to Von or VPort_PD(min) whichever is more."
or, combined with Kousi's suggested fix it becomes
"The PD shall turn on at a voltage greater than Voff and less than or equal to Von or VPort_PD(min) whichever is more".
Alternatively we can also change Von = 42.5V.
Attachment shows my interpretation of all shall statements in 33.3.7.1.
Kind regards,
Lennart
From: Koussalya Balasubramanian (kobalasu) [kobalasu@xxxxxxxxx]
Sent: Tuesday, March 17, 2015 7:10
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] PD Load turn onTeam
I collected the feedback given to me on "PD load turn on maintenance request" and modified the suggested solution little bit. Please see below.
Problem Statement:
Reference - http://www.ieee802.org/3/bt/public/jan15/balasubramanian_02_0115.pdf - PDs in the field turn on their Load during Inrush. This leads to PD cap not charging up fully (even if C<180uf and PSE is following inrush rules from 33.2.7.5). This may lead to operational problems after inrush. There is a Voff requirement in PD table 33-18 to ensure power supply remains turned off for V<30V, but customers seem to read this as applicable only "after power on" not during "power on" - hence they turn on their DC-DC during inrush causing problems.
Suggested Solution
Add the following to section 33.3.7.3
"PDs shall not draw more than the maximum current allowed by a PSE during inrush as outlined in section 33.2.7.5"
Change 2nd paragraph of section 33.3.7.1 as follows (change shown with underline)
"The PD shall turn on at a voltage greater than Voff and less than or equal to Von"
Thanks
Kousi
From: Koussalya Balasubramanian (kobalasu) [mailto:kobalasu@xxxxxxxxx]
Sent: Thursday, February 26, 2015 11:09 AM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: [802.3_4PPOE] PD Load turn on
Team
In Jan interim meeting, Jean and I presented about clarifying PD load turn on behavior that will help in making sure non-compliant behaviors are avoided. The team directed us to submit this as a maintenance request. Here is what we are planning on submitting – given the maintenance request will come back to 4PPoE group, we would appreciate any comment from 4PPoE group before we submit it.
Problem Statement:
- PDs in the field turn on their Load during Inrush. This leads to PD cap not charging up fully (even if C<180uf and PSE is following inrush rules from 33.2.7.5). This may lead to operational problems after inrush. There is a Voff requirement in PD table 33-18 to ensure power supply remains turned off for V<30V, but customers seem to read this as applicable only "after power on" not during "power on" - hence they turn on their DC-DC during inrush causing problems.
Suggested Solution
Add the following to section 33.3.7.3
"PDs shall not draw more than the maximum current allowed by a PSE during inrush as outlined in section 33.2.7.5"
Add the following to section 33.3.7.1 at the end of second paragraph.
"The turn off voltage Voff applies both during power on and after power on"
Thanks
Kousi
