Re: SMPS EMC Emissions
I read in !emc-pstc that John Barnes jrbar...@iglou.com wrote (in 3d74d7d8.3...@iglou.com) about 'SMPS EMC Emissions' on Tue, 3 Sep 2002: I've updated the statement to meet the current international standards for information technology equipment (ITE), Specifically, that EN 61000-3-2 **Class D** needs to be met by PCs and monitors, I hope. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: SMPS EMC Emissions
Alex, Are you speaking of radiation directly from a SMPS on a table? If this is the case, why, yes, you may, ASK for margin, but you may find few vendors willing to bid to that requirement. Few ITE makers would warrant their own boards to meet FCC limits outside a cabinet! But a SMPS should never be close to marginally compliant in radiated emission from its power cord and asking for margin is in such cases (I would say) a smart thing to do. How much depends on vendor process variability. My own experience has been that radiated emissions above 30 MHz attributable to SMPS were readily shielded -- once the PS was installed in equipment. It took very little common-mode filtering to attenuate radiation due to conducted noise once in the box, and the box was well enough designed to avoid slots and openings. (Granted, that was earlier days, with switching frequencies of 100 KHz or less.) I did institute a practice of testing SMPS inside chassis they were designed to fit, and the reason is rather amusing. A PS we were testing with resistive load consistently failed conducted emissions. As was our practice at the time, we were testing with PS and load on a table, into LISN's installed in a shielded (not anechoic) chamber, thus ensuring we did not measure ambients. But the vendor was puzzled, as HIS tests showed everything within limits. Engineers flew in from Hong Kong and witnessed the tests. Yes, conducted emissions WERE too high. But efforts to reduce them were not too successful. About then I discovered that if we tested OUTSIDE the chamber, these PS's _passed_. Inside, fail. Outside, pass. The SMPS output wiring was was exciting resonance in the chamber and coupling onto the IEC power cord, whence they showed up as conducted emissions to the LISN's. From that time forward, we built resistor load boards that fit in place of a motherboard, and were able to see a MUCH reduced level of conducted noise. (We also got a good idea how well the fan cooled things.) I do recommend testing subassemblies in a manner as similar to their intended use as possible. For one thing, we saved money on each PS that didn't need design changes. And THAT adds up. You make note of the effect of the SMPS on emissions it does not generate, coming from the EUT it powers. This is a bit of a different bird. I believe in not putting such emissions where a power supply will pass them, but (depending on your design process) you may have little choice. In this case, rather than specifying some margin for emissions to the PS maker (who does not KNOW what you apply to its outputs) why not an attenuation requirement? How much, may be derived by looking at RF current on the PS output, with a current clamp, and comparing this to what's seen on the power cord. This kind of need is not unique to SMPS's, as many peripheral cards, having been tested in a quiet computer, are offered for sale to a world of unquiet ones. Ad Astra per Aspirin! Cortland --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: SMPS EMC Emissions
Alex, When I was developing power supplies at my previous employer, I'd include a statement like this in our Request For Quotation (RFQ): The power supply must meet the following limits with 6dB margin when supplying power to an 10-ohm resistive load: * FCC Class B (USA). * CISPR 22-B (Europe). * VCCI-B (Japan). The power supply must meet the following requirements: * EN 61000-3-2 Class A. * EN 61000-3-3. * EN 61000-4-2 level 4. * EN 61000-4-3 level 2. * EN 61000-4-4 level 3. * EN 61000-4-5 level 3. * EN 61000-4-6 level 2. * EN 61000-4-8 level 1. * EN 61000-4-11. I've updated the statement to meet the current international standards for information technology equipment (ITE), but it is based on an RFQ for a power supply that we used on at least three products. The resistive loads were chosen to set each output to its maximum rated continuous load at its nominal output voltage. My previous employer also specified higher levels for EN 61000-4-2 and EN 61000-4-4 than required for the CE Mark, as a matter of company policy. The southwest United States, for example, tends to be much drier than Europe, so a higher electrostatic discharge immunity requirement reduces field problems there. John Barnes KS4GL dBi Corporation http://www.dbicorporation.com/ --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: SMPS EMC Emissions
CONFLICT OF INTEREST ALERT: My employer makes SMPS. For both conducted emissions, an unit with PFC typically makes life easier. For reduced radiated emissions, avoid the open U chassis units. Please note that as customers demand greater efficiencies and reduced sizes, you will see much higher main converter frequencies. In any case, a supplier that (assuming your test technique is consistent) produces units with a wide variance in emissions characteristics may be indicative of poor design and/or no quality control. Brian -Original Message- From: Jim Conrad [mailto:jc...@shore.net] Sent: Tuesday, September 03, 2002 3:55 AM To: Alex McNeil; emc-p...@majordomo.ieee.org Subject: RE: SMPS EMC Emissions Alex wrote: Do you think it is reasonable to specify in my power supply specification that the manufacturers SMPS should meet EN55022 Class B -6dB Yes. I would ask for 6 dB margin since measurement uncertainty for a typical conducted measurements system is 5.4 dB. You must also allow for unit to unit variations in manufacturing. Sample 5 units and apply the 80/80 rule and see if they still pass. Jim -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Alex McNeil Sent: Tuesday, September 03, 2002 4:57 AM To: 'emc-p...@majordomo.ieee.org' Subject: SMPS EMC Emissions Hi Group, First of all thank you to those who replied to my previous email. I have not had time to reply personally...yet. I have noticed that the broadband noise of some SMPS are already near to the limits of EN55022 Class B (I tested with a max resistive load). This gives my product little scope for emissions at these broadband frequencies, especialy when my product is taking peak load e.g. printing. The power supply manufacturer rightly claims that his product does meet EN55022 Class B. Do you think it is reasonable to specify in my power supply specification that the manufacturers SMPS should meet EN55022 Class B -6dB or? Have any of you come across a similar scenario? As usual , I look forward to your professional opinions. Kind Regards Alex McNeil Principal Engineer Tel: +44 (0)131 479 8375 Fax: +44 (0)131 479 8321 email: alex.mcn...@ingenicofortronic.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
SMPS EMC Emissions
Forum addendum I think I need to make it clearer that my main concern was for radiated emissions ps Hi Jim, Thanks for your reply Kind Regards Alex McNeil Principal Engineer Tel: +44 (0)131 479 8375 Fax: +44 (0)131 479 8321 email: alex.mcn...@ingenicofortronic.com -Original Message- From: Jim Conrad [mailto:jc...@shore.net] Sent: Tuesday, September 03, 2002 11:55 AM To: Alex McNeil; emc-p...@majordomo.ieee.org Subject:RE: SMPS EMC Emissions Alex wrote: Do you think it is reasonable to specify in my power supply specification that the manufacturers SMPS should meet EN55022 Class B -6dB Yes. I would ask for 6 dB margin since measurement uncertainty for a typical conducted measurements system is 5.4 dB. You must also allow for unit to unit variations in manufacturing. Sample 5 units and apply the 80/80 rule and see if they still pass. Jim -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Alex McNeil Sent: Tuesday, September 03, 2002 4:57 AM To: 'emc-p...@majordomo.ieee.org' Subject: SMPS EMC Emissions Hi Group, First of all thank you to those who replied to my previous email. I have not had time to reply personally...yet. I have noticed that the broadband noise of some SMPS are already near to the limits of EN55022 Class B (I tested with a max resistive load). This gives my product little scope for emissions at these broadband frequencies, especialy when my product is taking peak load e.g. printing. The power supply manufacturer rightly claims that his product does meet EN55022 Class B. Do you think it is reasonable to specify in my power supply specification that the manufacturers SMPS should meet EN55022 Class B -6dB or? Have any of you come across a similar scenario? As usual , I look forward to your professional opinions. Kind Regards Alex McNeil Principal Engineer Tel: +44 (0)131 479 8375 Fax: +44 (0)131 479 8321 email: alex.mcn...@ingenicofortronic.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: SMPS EMC Emissions
Alex wrote: Do you think it is reasonable to specify in my power supply specification that the manufacturers SMPS should meet EN55022 Class B -6dB Yes. I would ask for 6 dB margin since measurement uncertainty for a typical conducted measurements system is 5.4 dB. You must also allow for unit to unit variations in manufacturing. Sample 5 units and apply the 80/80 rule and see if they still pass. Jim -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Alex McNeil Sent: Tuesday, September 03, 2002 4:57 AM To: 'emc-p...@majordomo.ieee.org' Subject: SMPS EMC Emissions Hi Group, First of all thank you to those who replied to my previous email. I have not had time to reply personally...yet. I have noticed that the broadband noise of some SMPS are already near to the limits of EN55022 Class B (I tested with a max resistive load). This gives my product little scope for emissions at these broadband frequencies, especialy when my product is taking peak load e.g. printing. The power supply manufacturer rightly claims that his product does meet EN55022 Class B. Do you think it is reasonable to specify in my power supply specification that the manufacturers SMPS should meet EN55022 Class B -6dB or? Have any of you come across a similar scenario? As usual , I look forward to your professional opinions. Kind Regards Alex McNeil Principal Engineer Tel: +44 (0)131 479 8375 Fax: +44 (0)131 479 8321 email: alex.mcn...@ingenicofortronic.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
SMPS EMC Emissions
Hi Group, First of all thank you to those who replied to my previous email. I have not had time to reply personally...yet. I have noticed that the broadband noise of some SMPS are already near to the limits of EN55022 Class B (I tested with a max resistive load). This gives my product little scope for emissions at these broadband frequencies, especialy when my product is taking peak load e.g. printing. The power supply manufacturer rightly claims that his product does meet EN55022 Class B. Do you think it is reasonable to specify in my power supply specification that the manufacturers SMPS should meet EN55022 Class B -6dB or? Have any of you come across a similar scenario? As usual , I look forward to your professional opinions. Kind Regards Alex McNeil Principal Engineer Tel: +44 (0)131 479 8375 Fax: +44 (0)131 479 8321 email: alex.mcn...@ingenicofortronic.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
