Two Transistor Forward converter has been revolutionized. - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: May 14, 2023, 04:42:36 pm
content: Hi,The Two Transistor Forward has been revolutionized as attached.In the attached, LTspice and jpeg, it is shown working well with bootstrap hi side drive. (ayk, “bootstrapping” is the super low component count way for hi side FET drive) The bootstrap cap is always kept charged by the extra FET as shown. Even if going no load for many hours…it can come back on instantly, without having to first refresh the bootstrap cap.Odd the market doesn’t offer chips that do what is shown discretely here?

author: jonpaul
author_rank: Super Contributor
timestamp: May 14, 2023, 09:38:34 pm
content: FTTS, nothing is "revolutionized" as your sketch of an untired and theortical simulation is not new, not novel and has no benefit over decades old state of the art.So, double fwd is very well known and developed. No need and no benefit for your two control IC and added ckts.My 1990s double foward 750W arc lamp was much simpler.ONE (not two) low cost Unitrode CM control IC, one small cheap drive transformer.Thus, a double foward conveeter, duty cycle is <50% , and both transistors conduct simultaneously. Drive is a 3 wdg trifilar gate drive trsf.RE pulsed load: Arc lamp loads go from OC to ~ 10..50V arc at very low Z in microseconds. As the application was surgical/medical, the load was constantly pulsed on off at operators discretion.We had perfect CM control by the IC .If you actually built anything instead of just endless simulation and speculation to irritate us, you might have actual engineering experience.IT WORKS IN PRODUCTION FOR YEARS.Another 10 min down the FTSS toilet bowl of time....Sigh,JonPS: NO I WILL NOT GIVE YOU MY DESIGN !!!!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 15, 2023, 05:08:05 am
content: Great idea. Well then, how's EMI?Tim

author: jonpaul
author_rank: Super Contributor
timestamp: May 15, 2023, 05:48:34 am
content: Tim RE EMI:as double FWD leakage L energy is perfectly clamped by the two diodes to RTN and 360V BUS, the EMI and switching losses are low.Our 1990s design used normal filters on both line and load in a critical medical instrument with CPU.Jon

author: Faringdon
author_rank: Super Contributor
timestamp: May 15, 2023, 06:07:02 am
content: QuoteThanks yes, switching node size reduction, common mode and diff mode filtering as normal. Do you mean you think theres extra EMI problems due to the ON/OFF control?As you know, the one attached acts in burst mode.But as you know, burst mode is nto particularly worse at conducted emissions than a normal frequency compensated converter.The bursts can have an "envelope frequency" of some few kHz, but, ayk, that low frequency isnt included in the EN55032 conducted emissions test.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 15, 2023, 06:44:50 pm
content: Quote from: jonpaul on May 15, 2023, 05:48:34 amMore to the point, look at the common mode on the primary.Tim

author: Faringdon
author_rank: Super Contributor
timestamp: May 15, 2023, 08:17:18 pm
content: QuoteThanks T3sl4co1l,Yes, the dv/dt is bad on pri, though, ayk, that is the same for frequency compensated 2 tran forwards, as it is for Burst mode 2 tran forwards.......which i am sure you agree with anyway. (in case it seems like i am trying to straw man you into looking as if you had said the opposite, which you had not).I know all will agree....Burst mode SMPS, is no worse for EMC than frequency compensated SMPS running continuously at the max power level...ie the max power of the burst level.

author: langwadt
author_rank: Super Contributor
timestamp: May 15, 2023, 08:28:56 pm
content: Quote from: T3sl4co1l on May 15, 2023, 05:08:05 amcoming up next, can it be cheaper than in China using a government proved Altium license and triple insulated litz wire ?

author: jonpaul
author_rank: Super Contributor
timestamp: May 16, 2023, 06:15:33 am
content: more usual FTTS blabber.Can we count the total time wasted with Farrington/Treezez interminable garbae?( just lost another minute...)Jon

author: ejeffrey
author_rank: Super Contributor
timestamp: May 16, 2023, 04:43:43 pm
content: Quote from: jonpaul on May 16, 2023, 06:15:33 amYou can just not read or reply to his threads. At least his posts are mostly technical based, mostly you are complaining about how much of a dumb waste of time his questions are. But if it's a waste of your time you don't need to reply at all. If you are worried about him wasting other peoples time, don't: I can look out for myself and so can everyone else here.

author: Weston
author_rank: Regular Contributor
timestamp: May 16, 2023, 05:26:10 pm
content: Quote from: jonpaul on May 16, 2023, 06:15:33 amLittle bit off topic on this thread, but I enjoy the Treez threads not because of his content but due to the replies.Some of the best power electronics content on the forum is people going off on tangents or explaining concept (or explaining why something will not work) in the replies (special call out to jonpaul and T3sl4co1l !) . If we did not have Treez as a constant noise source none of that would be posted and there would be a lot less power electronics content on the forum.

author: Faringdon
author_rank: Super Contributor
timestamp: May 16, 2023, 05:47:58 pm
content: Though a story is becoming...because its amazing how a massive number of Power electronics company staff think that a burst mode SMPS is worse at EMC , than a standard frequency compensated SMPS.....which if course, is totally not true....neither does it fail flicker.I once worked at a co, where they had a 600W UV lamp, which was on a gantry going back and forth, every time it hit the gantry end, the 600W was suddenly turned off, then suddenly turned back on again some 2 seconds later......the full load transient made the output go up to >60V.....and it eventually blew up the control PCB.......they were asked why they didnt use a Burst mode SMPS....which would have alleviated the problem....they said , because Burst Mode would fail EMC....which of course, is nonsense...they are pretty much just the same at EMC as a standard frequency compensated SMPS.(ayk, a Burst mode smps, which has a hysteretic comparator at output for regulation.....has a certain fixed peak current setting.....if you incrementally increase its load...you will eventually get to a stage where its output drops a little , and it goes into continuous mode..not bursting.............if you use it for a power level which is just a bit lower than dropout, then it is in burst mode, but its peak current level is pretty well the same as what you'd get with a frequency compensated SMPS.)Also, it deffo does not fail flicker.