The SELV limit is 60VDC or 42.4VAC in IEC 60950 With best regards, Walter -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of tompegbel Sent: Friday, October 22, 2004 4:22 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: 48V power distribution Thanks Steve, I appreciate your insight. I guess I really wanted to focus on the issue of isolation versus non-isolation at the point of entry for the PCB power distribution provided it is within SELV limits. Provided components are available and cost of implemenation is acceptably low, is there any major drawbacks with isolation at the point of load versus isolation at the point of entry? Regards, --Tom --- In si-list@xxxxxxxxxxxxxxx, steve weir <weirsp@xxxx> wrote: > Tom, the biggest issue is that 48V exceeds the 42V low-voltage safety limit > and so requires substantially greater clearances. A 24V system is under > that limit and does not face the same problem. 48V also changes the > dynamics of available semiconductors. 12V systems and to a certain extent, > 24V systems can leverage the super low on resistance and low capacitance > FETs and diodes. The last issue is one of magnetics and practical > form-factors. Given you work for Vicor, you should be pretty familiar with > those and how taller primary to output ratios aggravate same. > > Regards, > > > Steve > At 02:04 PM 10/19/2004 +0000, tompegbel wrote: > > >Is there a good resource/document for addressing the concerns in > >bussing 48V power in a multilayer board? The recently popular 12V or > >lower intermediate bus approach has limitations as voltages get lower > >and current gets higher. There appears to be new approaches of using > >a higher bus voltage (24V or 48V) for distribution since this was > >explored in the 80's with the advent of distributed power and now > >more recently with VoIP type designs. Any assistance appreciated > > > > > > > >------------------------------------------------------------------ > >To unsubscribe from si-list: > >si-list-request@xxxx with 'unsubscribe' in the Subject field > > > >or to administer your membership from a web page, go to: > >//www.freelists.org/webpage/si-list > > > >For help: > >si-list-request@xxxx with 'help' in the Subject field > > > >List FAQ wiki page is located at: > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > >List technical documents are available at: > > http://www.si-list.org > > > >List archives are viewable at: > > //www.freelists.org/archives/si-list > >or at our remote archives: > > http://groups.yahoo.com/group/si-list/messages > >Old (prior to June 6, 2001) list archives are viewable at: > > http://www.qsl.net/wb6tpu > > > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxx with 'help' in the Subject field > > List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > List technical documents are available at: > http://www.si-list.org > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu