" provoked into spontaneous energetic disassembly." -> Will use that phrase on next TRF/report.
The component with least margin tends to the main switch transitor(s). Mostly because of peak voltages at end of each cycle. Resonant-mode converters have less Vpk but more periodic RMS stressors. But as energy is easily controlled for each individual cycle, response to an external disturbance typically results in rapid shutdown of the gate drive. The circuit node that tends to have the most circulating energy is junction of PFC choke/diode/switch; and once the choke saturates, bad things start to happen. Typical PFC controllers run in transition mode or continuous-current mode, but the more recent fixed off-time controllers allows hi-current control, and can handle boost-choke saturation. Power transistors have greatly improved last ten years. Idss leakage spread has decreased an order of magnitude and breakdown V has decreased 50%. So if the power supply is not using recent stuff, you have no significant margin. Legacy stuff - cheap but has some evil failure modes buried in most power supply designs. New stuff - more cost but less boom. Brian -----Original Message----- From: John Woodgate [mailto:[email protected]] Sent: Tuesday, September 22, 2015 11:10 AM To: [email protected] Subject: Re: [PSES] Unexplained High Fallout of Power Supplies In message <64D32EE8B9CBDD44963ACB076A5F6ABB02717445@Mailbox-Tech.lecotech.local>, dated Tue, 22 Sep 2015, "Kunde, Brian" <[email protected]> writes: >I'm guessing that under some conditions, there could be some kind of >interaction between the rf filter and the power supply which maybe >causing our high fallout. Can you propose a test setup where we might >be able to simulate such conditions? I'm guessing the same, just from your report of the damage, but as I said about 50 k posts ago, I failed to understand the stability issues with PFC circuits. I just know that they can be provoked into spontaneous energetic disassembly. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk When I turn my back on the sun, it's to look for a rainbow John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
