Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[Brian O'Connell]

Mr. Nute,

Per IEV definition 192-10-06, fail-safe is:
"capable of preserving safety in the case of failure
Note 1 to entry: The safe conditions should be defined for the particular 
application."

Per IEC62368-1, fail-safe only applies to stuff in annex K (safety interlocks). 
Where the mitigation is more of an exercise in reducing energy after an 
interlock open, rather than any specific reliable performance level. There is 
no 'fail-safe' in IEC60950-1 (probably because TC108 had a Romulan spy at the 
time of the 1st edition).

As for MTTF, it tends towards a ritualized mathematical ceremony per Mil217 and 
SR322 (hooded robes are required to perform the calculations). Reliability is 
more secular, but is a 'localized' property per the scoped standard's test 
requirements. And have seen some designs that fail-safe the fail safe; that is, 
a decreased reliability, but less likely to fail to an unsafe condition. Choose 
your poison.

Avoiding the HazLoc ('intrinsic' safety) morass, the stuff in UL1310 and 
UL5085-3 resembles something that is reliably long-term fault tolerant (note 
the non-use of 'fail-safe') for limited categories of equipment.

So, it is obvious that my stupidity (and evil thoughts) prevent me from 
answering your questions, because this is another "it depends". That is, fail 
safe depends on integrating properly rated components into clever designs, and 
implementing ingenious test methods. In my little cloistered world, there are 
no fail-safe components and there are no reliable fail-safe systems. But there 
can be extensively tested products that have been subject to incremental design 
improvements, where the probability of a catastrophic life-time failure 
increasingly favors your side.

Brian


From: Richard Nute [mailto:ri...@ieee.org] 
Sent: Thursday, March 08, 2018 1:42 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

In my early days in product safety, safety was prohibited from relying on 
conduction in a vacuum, gas, or semiconductor.  

Today. we rely on semiconductor current limiters and similar devices, e.g., 
GFCI control circuits.  

Are such limiters and control circuits fail-safe devices?   

Or, are they "reliable" devices and circuits where their lifetime is expected 
(proven) to be greater than the host equipment?

Rich

-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
<emc-p...@ieee.org>

All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas <sdoug...@ieee.org>
Mike Cantwell <mcantw...@ieee.org>

For policy questions, send mail to:
Jim Bacher:  <j.bac...@ieee.org>
David Heald: <dhe...@gmail.com>

Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[Nyffenegger, Dave]

Yes new GFCIs are required to have built in automatic testing as most old ones 
installed are not getting the required periodic manual testing.

From: MIKE [mailto:msherma...@comcast.net]
Sent: Thursday, March 08, 2018 5:34 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

I regard North American household GFCIs and industrial shunt trip GFCIs to not 
be fail safe because they can fail silently and therefore require period 
testing to verify continued functionality.  I believe that the UL standard for 
GFCIs has recently been updated to require some periodic self testing to 
address this issue.
Mike Sherman
Graco Inc.

Sent from XFINITY Connect Mobile App

-- Original Message --

From: John Woodgate
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Sent: March 8, 2018 at 3:57 PM
Subject: Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

Probably some fail-safe, some reliable. I think that this is why 'safety' 
involves risk-assessment, not just meeting standards.

John Woodgate OOO-Own Opinions Only

J M Woodgate and Associates www.woodjohn.uk<http://www.woodjohn.uk>

Rayleigh, Essex UK
On 2018-03-08 21:41, Richard Nute wrote:

In my early days in product safety, safety was prohibited from relying on 
conduction in a vacuum, gas, or semiconductor.

Today… we rely on semiconductor current limiters and similar devices, e.g., 
GFCI control circuits.

Are such limiters and control circuits fail-safe devices?

Or, are they “reliable” devices and circuits where their lifetime is expected 
(proven) to be greater than the host equipment?

Rich


-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
<emc-p...@ieee.org<mailto:emc-p...@ieee.org>>

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to 
unsubscribe)<http://www.ieee-pses.org/list.html>
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas <sdoug...@ieee.org<mailto:sdoug...@ieee.org>>
Mike Cantwell <mcantw...@ieee.org<mailto:mcantw...@ieee.org>>

For policy questions, send mail to:
Jim Bacher <j.bac...@ieee.org<mailto:j.bac...@ieee.org>>
David Heald <dhe...@gmail.com<mailto:dhe...@gmail.com>>

-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
emc-p...@ieee.org<mailto:emc-p...@ieee.org>

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to 
unsubscribe)<http://www.ieee-pses.org/list.html>
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas sdoug...@ieee.org<mailto:sdoug...@ieee.org>
Mike Cantwell mcantw...@ieee.org<mailto:mcantw...@ieee.org>

For policy questions, send mail to:
Jim Bacher j.bac...@ieee.org<mailto:j.bac...@ieee.org>
David Heald dhe...@gmail.com<mailto:dhe...@gmail.com>
-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
<emc-p...@ieee.org<mailto:emc-p...@ieee.org>>

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to 
unsubscribe)<http://www.ieee-pses.org/list.html>
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas <sdoug...@ieee.org<mailto:sdoug...@ieee.org>>
Mike Cantwell <mcantw...@ieee.org<mailto:mcantw...@ieee.org>>

For policy questions, send mail to:
Jim Bacher <j.bac...@ieee.org<mailto:j.bac...@ieee.org>>

Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[MIKE]

I regard North American household GFCIs and industrial shunt trip GFCIs to not be fail safe because they can fail silently and therefore require period testing to verify continued functionality.  I believe that the UL standard for GFCIs has recently been updated to require some periodic self testing to address this issue. Mike ShermanGraco Inc. Sent from XFINITY Connect Mobile App-- Original Message --From: John WoodgateTo: EMC-PSTC@LISTSERV.IEEE.ORGSent: March 8, 2018 at 3:57 PMSubject: Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter
  
  
Probably some
fail-safe, some reliable. I think that this is why 'safety'
involves risk-assessment, not just meeting standards.

John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2018-03-08 21:41, Richard Nute
  wrote:


  
  
  
  
 
In my early days in product safety, safety
  was prohibited from relying on conduction in a vacuum, gas, or
  semiconductor.  
 
Today… we rely on semiconductor current
  limiters and similar devices, e.g., GFCI control circuits.  
 
Are such limiters and control circuits
  fail-safe devices?   
 
Or, are they “reliable” devices and
  circuits where their lifetime is expected (proven) to be
  greater than the host equipment?
 
Rich
 
 
  
  -
  
  This message is from the IEEE Product Safety Engineering
Society emc-pstc discussion list. To post a message to the list,
send your e-mail to <emc-p...@ieee.org>
  All emc-pstc postings are archived and searchable on the web
at:
http://www.ieee-pses.org/emc-pstc.html
  Attachments are not permitted but the IEEE PSES Online
Communities site at http://product-compliance.oc.ieee.org/
can be used for graphics (in well-used formats), large files,
etc.
  Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html
  (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html
  
  For help, send mail to the list administrators:
Scott Douglas <sdoug...@ieee.org>
Mike Cantwell <mcantw...@ieee.org>
  
  For policy questions, send mail to:
Jim Bacher <j.bac...@ieee.org>
David Heald <dhe...@gmail.com>
  


  

-

This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org

All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc.


Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas sdoug...@ieee.org
Mike Cantwell mcantw...@ieee.org

For policy questions, send mail to:
Jim Bacher  j.bac...@ieee.org
David Heald dhe...@gmail.com


-

This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org

All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc.


Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas sdoug...@ieee.org
Mike Cantwell mcantw...@ieee.org

For policy questions, send mail to:
Jim Bacher  j.bac...@ieee.org
David Heald dhe...@gmail.com

Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[John Woodgate]

Probably some fail-safe, some reliable. I think that this is why 
'safety' involves risk-assessment, not just meeting standards.


John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2018-03-08 21:41, Richard Nute wrote:


In my early days in product safety, safety was prohibited from relying 
on conduction in a vacuum, gas, or semiconductor.


Today… we rely on semiconductor current limiters and similar devices, 
e.g., GFCI control circuits.


Are such limiters and control circuits fail-safe devices?

Or, are they “reliable” devices and circuits where their lifetime is 
expected (proven) to be greater than the host equipment?


Rich

-


This message is from the IEEE Product Safety Engineering Society 
emc-pstc discussion list. To post a message to the list, send your 
e-mail to >


All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html


Attachments are not permitted but the IEEE PSES Online Communities 
site at http://product-compliance.oc.ieee.org/ can be used for 
graphics (in well-used formats), large files, etc.


Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to 
unsubscribe)

List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas >
Mike Cantwell >

For policy questions, send mail to:
Jim Bacher >
David Heald >




-

This message is from the IEEE Product Safety Engineering Society emc-pstc discussion 
list. To post a message to the list, send your e-mail to 

All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell 

For policy questions, send mail to:
Jim Bacher:  
David Heald: 

Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[Adam Dixon]

This question has been asked on TI's E2E forum for other parts in this family.  
See the 2nd 60950 report link that Eric posted in this discussion thread:
https://e2e.ti.com/support/interface/usb/f/1008/t/563031

It might be worth opening a new thread for this particular part number to see 
if there is another IEC 60950 report that TI would share.  Or maybe this report 
would suffice.


Cheers,
Adam in Atlanta
adam.di...@ieee.org

Sent from my iPad

> On Mar 5, 2018, at 4:42 PM, Ted Eckert 
> <07cf6ebeab9d-dmarc-requ...@ieee.org> wrote:
> 
> I agree with Mr. Woodgate and I can add a little more information. UL 2367 is 
> generally considered equivalent as Test Program 2 of Annex CC. Most NCBs will 
> accept it as such and you should be able to place a statement in your report 
> indicating the equivalency. Not all NCBs will necessarily accept the 
> equivalence, but I have yet to run into an issue with integrated circuits 
> approved under UL 2367.
>  
> Ted Eckert
> Microsoft Corporation
>  
> The opinions expressed are my own and do not necessarily reflect those of my 
> employer.
>  
> From: John Woodgate <j...@woodjohn.uk> 
> Sent: Monday, March 5, 2018 1:07 PM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter
>  
> The standard says '...meets a suitable test program as given in Annex CC' 
> [not Annex C].  It does not say 'shall meet the test program given in Annex 
> CC'. As you know, the manufacturer is permitted  to decide (and document) 
> that a part meeting UL2367 is acceptable, and it would be up to a regulatory 
> authority to challenge that. It seems unlikely that UL 2367 would be 
> deficient, since this is a precaution against fire, which is a major concern 
> of UL, of course.
> 
> John Woodgate OOO-Own Opinions Only
> J M Woodgate and Associates www.woodjohn.uk
> Rayleigh, Essex UK
> On 2018-03-05 20:11, Charlie Blackham wrote:
> All
>  
> Client has designed a USB port with the DC power protected by a TI TPS2052B 
> Current limiter:
> Component details: www.ti.com/product/TPS2052B/description
> Component is UL recognised component under QVGS2.E169910 which is based on UL 
> 2367
>  
>  
> 2.5 Limited power sources
> c) a regulating network, or an integrated circuit (IC) current limiter, 
> limits the output in compliance with Table 2B, both with and without a 
> simulated single fault (see 1.4.14) in the regulating network or the IC 
> current limiter (open circuit or short circuit). A single fault between the 
> input and output is not conducted if the IC current limiter meets a suitable 
> test program as given in Annex CC;
>  
> Annex CC requires appears to require quite extensive testing of the 
> component, and I can’t tell whether a component recognised against UL2367 
> would meet this or not.
>  
> The issue, is that if they s/c the protection component, the output may no 
> longer be LPS – we have provision to fit a suitable fuse on the board, but 
> would prefer not to, so would be grateful for any advice
>  
> Thanks
> Charlie
>  
>  
> Charlie Blackham
> Sulis Consultants Ltd
> Mead House
> Longwater Road
> Eversley
> RG27 0NW
> UK
> Tel: +44 (0)7946 624317
> Email: char...@sulisconsultants.com
> Web: www.sulisconsultants.com
> Registered in England and Wales, number 05466247
>  
> -
> 
> This message is from the IEEE Product Safety Engineering Society emc-pstc 
> discussion list. To post a message to the list, send your e-mail to 
> <emc-p...@ieee.org>
> 
> All emc-pstc postings are archived and searchable on the web at: 
> http://www.ieee-pses.org/emc-pstc.html
> 
> Attachments are not permitted but the IEEE PSES Online Communities site at 
> http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
> formats), large files, etc.
> 
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to 
> unsubscribe)
> List rules: http://www.ieee-pses.org/listrules.html
> 
> For help, send mail to the list administrators:
> Scott Douglas <sdoug...@ieee.org>
> Mike Cantwell <mcantw...@ieee.org>
> 
> For policy questions, send mail to:
> Jim Bacher <j.bac...@ieee.org>
> David Heald <dhe...@gmail.com>
> 
>  
> -
> 
> This message is from the IEEE Product Safety Engineering Society emc-pstc 
> discussion list. To post a message to the list, send your e-mail to 
> <emc-p...@ieee.org>
> 
> All emc-pstc postings are archived and searchable on the web at: 
> http://www

Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[Ted Eckert]

I agree with Mr. Woodgate and I can add a little more information. UL 2367 is 
generally considered equivalent as Test Program 2 of Annex CC. Most NCBs will 
accept it as such and you should be able to place a statement in your report 
indicating the equivalency. Not all NCBs will necessarily accept the 
equivalence, but I have yet to run into an issue with integrated circuits 
approved under UL 2367.

Ted Eckert
Microsoft Corporation

The opinions expressed are my own and do not necessarily reflect those of my 
employer.

From: John Woodgate <j...@woodjohn.uk>
Sent: Monday, March 5, 2018 1:07 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter


The standard says '...meets a suitable test program as given in Annex CC' [not 
Annex C].  It does not say 'shall meet the test program given in Annex CC'. As 
you know, the manufacturer is permitted  to decide (and document) that a part 
meeting UL2367 is acceptable, and it would be up to a regulatory authority to 
challenge that. It seems unlikely that UL 2367 would be deficient, since this 
is a precaution against fire, which is a major concern of UL, of course.

John Woodgate OOO-Own Opinions Only

J M Woodgate and Associates 
www.woodjohn.uk<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.woodjohn.uk=04%7C01%7Cted.eckert%40microsoft.com%7C57ad0c33b883418c42a608d582dd12a3%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C1%7C636558808380524292%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwifQ%3D%3D%7C-2=Ul7TLxZq%2FHEl36YyaO1rCASJ4o%2B26Yn2z67Ld7rJ%2Fbo%3D=0>

Rayleigh, Essex UK
On 2018-03-05 20:11, Charlie Blackham wrote:
All

Client has designed a USB port with the DC power protected by a TI TPS2052B 
Current limiter:

  *   Component details: 
www.ti.com/product/TPS2052B/description<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ti.com%2Fproduct%2FTPS2052B%2Fdescription=04%7C01%7Cted.eckert%40microsoft.com%7C57ad0c33b883418c42a608d582dd12a3%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C1%7C636558808380524292%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwifQ%3D%3D%7C-2=FUSXv3Bp93L9rC1gtGCcocla953sRv6etd8bPi9VVss%3D=0>
  *   Component is UL recognised component under QVGS2.E169910 which is based 
on UL 2367


2.5 Limited power sources
c) a regulating network, or an integrated circuit (IC) current limiter, limits 
the output in compliance with Table 2B, both with and without a simulated 
single fault (see 1.4.14) in the regulating network or the IC current limiter 
(open circuit or short circuit). A single fault between the input and output is 
not conducted if the IC current limiter meets a suitable test program as given 
in Annex CC;

Annex CC requires appears to require quite extensive testing of the component, 
and I can't tell whether a component recognised against UL2367 would meet this 
or not.

The issue, is that if they s/c the protection component, the output may no 
longer be LPS - we have provision to fit a suitable fuse on the board, but 
would prefer not to, so would be grateful for any advice

Thanks
Charlie


Charlie Blackham
Sulis Consultants Ltd
Mead House
Longwater Road
Eversley
RG27 0NW
UK
Tel: +44 (0)7946 624317
Email: char...@sulisconsultants.com<mailto:char...@sulisconsultants.com>
Web: 
www.sulisconsultants.com<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Foutlook.hslive.net%2Fowa%2Fredir.aspx%3FC%3D02be3bf3e3a544d1bdf7b6c99fbd12f5%26URL%3Dhttp%253a%252f%252fwww.sulisconsultants.com%252f=04%7C01%7Cted.eckert%40microsoft.com%7C57ad0c33b883418c42a608d582dd12a3%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C1%7C636558808380524292%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwifQ%3D%3D%7C-2=8uI5K8JwRPvmrDSCwCXAuO017Eb9mMZHyy3RYxODfrM%3D=0>
Registered in England and Wales, number 05466247

-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
<emc-p...@ieee.org<mailto:emc-p...@ieee.org>>

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ieee-pses.org%2Femc-pstc.html=04%7C01%7Cted.eckert%40microsoft.com%7C57ad0c33b883418c42a608d582dd12a3%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C1%7C636558808380524292%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwifQ%3D%3D%7C-2=dmDuD9Kjeg%2BiZgwLSLp72ScRxetJpVReEII0NjL3dco%3D=0>

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fproduct-compliance.oc.ieee.org%2F=04%7C01%7Cted.eckert%40microsoft.com%7C57ad0c33b883418c42a608d582dd12a3%7C72f988bf86

Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[John Woodgate]

The standard says '...meets a suitable test program as given in Annex 
CC' [not Annex C].  It does not say 'shall meet the test program given 
in Annex CC'. As you know, the manufacturer is permitted  to decide (and 
document) that a part meeting UL2367 is acceptable, and it would be up 
to a regulatory authority to challenge that. It seems unlikely that UL 
2367 would be deficient, since this is a precaution against fire, which 
is a major concern of UL, of course.


John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2018-03-05 20:11, Charlie Blackham wrote:


All

Client has designed a USB port with the DC power protected by a TI 
TPS2052B Current limiter:


  * Component details: www.ti.com/product/TPS2052B/description

  * Component is UL recognised component under QVGS2.E169910 which is
based on UL 2367

*2.5 Limited power sources*

c) a regulating network, or an integrated circuit (IC) current 
limiter, limits the output in compliance with Table 2B, both with and 
without a simulated single fault (see 1.4.14) in the regulating 
network or the IC current limiter (open circuit or short circuit). A 
single fault between the input and output is not conducted if the IC 
current limiter meets a suitable test program as given in Annex CC;


Annex CC requires appears to require quite extensive testing of the 
component, and I can’t tell whether a component recognised against 
UL2367 would meet this or not.


The issue, is that if they s/c the protection component, the output 
may no longer be LPS – we have provision to fit a suitable fuse on the 
board, but would prefer not to, so would be grateful for any advice


Thanks

Charlie

*Charlie Blackham*

*Sulis Consultants Ltd*

*Mead House*

*Longwater Road*

*Eversley*

*RG27 0NW*

*UK*

*Tel: +44 (0)7946 624317*

*Email: char...@sulisconsultants.com 
*


*Web: **www.sulisconsultants.com* 



Registered in England and Wales, number 05466247

-


This message is from the IEEE Product Safety Engineering Society 
emc-pstc discussion list. To post a message to the list, send your 
e-mail to >


All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html


Attachments are not permitted but the IEEE PSES Online Communities 
site at http://product-compliance.oc.ieee.org/ can be used for 
graphics (in well-used formats), large files, etc.


Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to 
unsubscribe)

List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas >
Mike Cantwell >

For policy questions, send mail to:
Jim Bacher >
David Heald >




-

This message is from the IEEE Product Safety Engineering Society emc-pstc discussion 
list. To post a message to the list, send your e-mail to 

All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell 

For policy questions, send mail to:
Jim Bacher:  
David Heald: 

[PSES] IEC60950-1 Limited Power Source via IC current limiter

[Charlie Blackham]

All

Client has designed a USB port with the DC power protected by a TI TPS2052B 
Current limiter:

  *   Component details: 
www.ti.com/product/TPS2052B/description
  *   Component is UL recognised component under QVGS2.E169910 which is based 
on UL 2367


2.5 Limited power sources
c) a regulating network, or an integrated circuit (IC) current limiter, limits 
the output in compliance with Table 2B, both with and without a simulated 
single fault (see 1.4.14) in the regulating network or the IC current limiter 
(open circuit or short circuit). A single fault between the input and output is 
not conducted if the IC current limiter meets a suitable test program as given 
in Annex CC;

Annex CC requires appears to require quite extensive testing of the component, 
and I can't tell whether a component recognised against UL2367 would meet this 
or not.

The issue, is that if they s/c the protection component, the output may no 
longer be LPS - we have provision to fit a suitable fuse on the board, but 
would prefer not to, so would be grateful for any advice

Thanks
Charlie


Charlie Blackham
Sulis Consultants Ltd
Mead House
Longwater Road
Eversley
RG27 0NW
UK
Tel: +44 (0)7946 624317
Email: char...@sulisconsultants.com
Web: 
www.sulisconsultants.com
Registered in England and Wales, number 05466247


-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 


All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell 

For policy questions, send mail to:
Jim Bacher:  
David Heald: