Negligible leakage comes from a decent xfmr design (typically 100-1500nA), essentially all leakage, for class 1 construction, comes from the y-caps in the filter section of the ac mains input. Also, I have seen some SMPS designs use Y1 caps for pri/sec coupling - which will contribute to leakage for any construction class.
Eliminating the 'last' 15 to 30uA for the patient-contact section is typically dependent on the elimination of the human-contact capacitance that is formed by hi di-electric insulators between two conductors that form parallel-plate capacitors. In my experience, there is no "typical" power supply. The 3d edition of 60601-1 specifically addresses the issue of IT-approved units in ME. Ultimately, the cook-book power design tools from chip mfrs will poorly serve medical device designers. luck, Brian > -----Original Message----- > From: Arthur Michael [mailto:[email protected]] > Sent: Friday, March 23, 2007 7:30 AM > To: Brian O'Connell > Cc: [email protected] > Subject: RE: SMPS test according to IEC 60601-1 > > Hello All, > > Don't lose sight of the fact that low leakage current limits of > electromedical equipment will mandate particular transformer > constructions > which yield these low values of leakage current. In my experience a > typical '950 power supply will not satisfy the requirements. > > Best regards, Art Michael - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
