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Re: [8023-POEP] Solved another problem with DS



Jean,

 

You’re right, the At-midspan will probably take over from the Af-endspan eventually.  It could take minutes, hours, or weeks.  But when it does happen, it will be an interruption of service for that particular PD.  In fact, if the power transient is shorter than T_LIM then the Af-endspan will NOT turn off.  So you may get periodic resets of the PD without ever switching over to the At-midspan.

 

This is why we have to make sure the At-midspan, not the Af-endspan, powers up the PD initially.

 

I agree it would be great if somehow we could solve this problem without adding any components to the midspan, but I don’t see how.

 

Steve

 


From: owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Picard, Jean
Sent: Wednesday, May 31, 2006 10:13 AM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Solved another problem with DS

 

You are right Steve that at initial power up it is not guaranteed that the midspan will take control of PD power.

 

However, this guarantees that the midspan will take control of PD power when it is needed.

 

It is not perfect, but simple.

 

I mean that whatever solution will be adopted, it should be simple and should not  involve adding costly components in the midspan.

 

Jean

 

 

 

 

 


From: owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Steve Robbins
Sent: Wednesday, May 31, 2006 12:50 PM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Solved another problem with DS

 

Jean,

 

I don’t think your idea would work.  A PD that needs 20W may only need that much power occasionally, while drawing much less power most of the time.  So it probably wouldn’t cause an Af-endspan to go into fold-back on initial power-up.

 

Steve

 


From: owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Picard, Jean
Sent: Wednesday, May 31, 2006 9:30 AM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Solved another problem with DS

 

All

 

I think we should try to keep it simple.

 

One simple way would be the following:

 

If the af PSE tries to power the 20W PD, if its current goes higher than Icut, it will go into overload fault and will turn off for at least 750 msec.

 

One way to make sure the midspan will then power the high power PD would be to change the spec so that for a PoE+ PSE Alternative B, the backoff time becomes 500 msec instead of 2 seconds.

 

So, during the fault off time of af PSE, the midspan will take control of the PD.

 

 

Regards

 

Jean

 

Jean Picard

 

Power Interface Systems Engineer

 

Texas Instruments

50 Phillippe Cote Street

Manchester, NH 03101

 

Phone : 603-222-8683

jean_picard@xxxxxx

 

 

 


From: owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Steve Robbins
Sent: Wednesday, May 31, 2006 10:59 AM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Solved another problem with DS

 

Yair,

 

I think you missed the point.

 

The solution is NOT to “…mandate separate signatures for each 2P…” because we also want “medium power” on 2P.  The Task Force already agreed to this.

 

So there will be some PDs in the 15W to 30W(?) range that have an input structure like an Af-PD (SS with diode bridges).

 

The obvious upgrade path for a user would be to add a medium-power At-midspan in-line with his existing Af-endspan.  These two PSEs can’t share the load since the PD is SS.  So the At-midspan has to supplant (take the place of) the Af-endspan.

 

I showed a method to assure the midspan will power the MP PD every time.  I think this will be essential to the 802.3at standard.

 

Steve

 


From: Yair Darshan [mailto:YairD@xxxxxxxxxxxxxx]
Sent: Wednesday, May 31, 2006 4:11 AM
To: Steve Robbins; STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: RE: [8023-POEP] Solved another problem with DS

 

Steve and all,

 

The problem shown in this presentation can be easily solved by mandating detection and classification signature for every 2P in the PD.

Specifically separate signatures for each 2P and not a common one as measured at the RJ45.

See attached presentation in page 13 for the proposed scope of work.

This is the idea of how standard can be simplified.

Doing the above is not requiring any special specifications from the PSE.

The Endspan PSE will detect and classify pair A.

The Midspan PSE will detect and classify pair B.

Both channels will turned on within the current 802.3af timings or similar to it.

Since each channel A and B are not tied together at the diode bridge output, the PD can be operated easily by using the PD circuitry which is TBD (implementation independent).

 

Yair

 

 

 


From: owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Steve Robbins
Sent: Wednesday, May 31, 2006 12:14 AM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: [8023-POEP] Solved another problem with DS

 

Guys,

 

I think I’ve solved another problem that’s inherent with DS.  See the attached pdf.  (Only about 10 more tough problems to go!) 

 

I’d sure appreciate some comments.

 

Steve