Hey Been trying to find the post with the lossless snubber, with AFAIR a capacitor from the drain node to a regenerative point. I am working on a 2 switch flyback and some other schemes, but would like to try that novel idea out.... Anyone knows a pointer to the thread? Regards Klaus
Somebody had an idea for a lossless flyback snubber
Started by ●May 24, 2016
Reply by ●May 24, 20162016-05-24
On Tuesday, May 24, 2016 at 4:41:49 PM UTC-7, klaus.k...@gmail.com wrote:> Hey > > Been trying to find the post with the lossless snubber, with AFAIR a capacitor from the drain node to a regenerative point. > > I am working on a 2 switch flyback and some other schemes, but would like to try that novel idea out.... > > Anyone knows a pointer to the thread? > > Regards > > KlausThat was Tim Wescott's thread, IIRC. HTH, James Arthur
Reply by ●May 24, 20162016-05-24
On 05/25/2016 01:41 AM, klaus.kragelund@gmail.com wrote:> Hey > > Been trying to find the post with the lossless snubber, with AFAIR a capacitor from the drain node to a regenerative point. > > I am working on a 2 switch flyback and some other schemes, but would like to try that novel idea out.... > > Anyone knows a pointer to the thread? > > Regards > > Klaus >there is one in ON semiconductors': SWITCHMODE(tm) Power Supplies Reference Manual and Design Guide SMPSRM/D Rev. 3B, July-2002 © SCILLC, 2007 Previous Edition © 2002 “All Rights Reserved'' (a pdf, page 28) google should be able to find it... I think I got it from a link on wikipedia a few years back...
Reply by ●May 24, 20162016-05-24
On Tue, 24 May 2016 16:41:44 -0700 (PDT), klaus.kragelund@gmail.com wrote:>Hey > >Been trying to find the post with the lossless snubber, with AFAIR a capacitor from the drain node to a regenerative point. > >I am working on a 2 switch flyback and some other schemes, but would like to try that novel idea out.... > >Anyone knows a pointer to the thread? > >Regards > >KlausI vaguely recall somewhat "lossless" snubbers that I implemented at GenRad (1977-87) that were diode-capacitor-resistor-inductor combos that worked so well that I made a fool of myself by grabbing the flag (un-heat-sunk) of a device to check its temperature forgetting that there was 300V P-P there... the technicians went hysterical ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Liberalism: Dictatorship By The People Who Think They Know Best
Reply by ●May 25, 20162016-05-25
On 05/24/2016 07:41 PM, klaus.kragelund@gmail.com wrote:> Hey > > Been trying to find the post with the lossless snubber, with AFAIR a > capacitor from the drain node to a regenerative point. > > I am working on a 2 switch flyback and some other schemes, but would > like to try that novel idea out.... > > Anyone knows a pointer to the thread? > > Regards > > Klaus >Well, there's The Vlad Memorial Antiseptic Converter, e.g. <http://electrooptical.net/www/sed/antiseptic_converter.asc> Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●May 25, 20162016-05-25
On Tue, 24 May 2016 16:41:44 -0700 (PDT), klaus.kragelund@gmail.com wrote:>Hey > >Been trying to find the post with the lossless snubber, with AFAIR a capacitor from the drain node to a regenerative point. > >I am working on a 2 switch flyback and some other schemes, but would like to try that novel idea out.... > >Anyone knows a pointer to the thread? > >Regards > >KlausThe loss-free snubbers depicted in the ON app and other locations, employing L, C, and D in varying quantities and orientation tend all to suffer from the same phenomenon, when using diodes that have a definable reverse recovery. As the reverse recovered charge is directly proportional to peak forward current and inversely proportional to rectifier area (ie size or current rating), the attempt to use rectifiers with sensible average current ratings in the snubber results in charge multiplication. More reverse recovery charge (and peak reverse current) develops in the snubber than is anticipated. If this peak current is passing through the primary winding, then leakage energy in the winding at snap-off will still require somwhere to go - typically to the negative supply through the parasitic body diode of the main fet switch. This diode is usually much slower than parts normally selected for switching. If the peak reverse recovery current in the snubber is preserved to pass into the parasitic diode, it will be returned to the primary for a third time....and so on. The behavior described may tend to defeat the purpose of the snubber, without intentional damping loss, or oversizing of snubber silicon. If the reverse peak current is less than the forward peak current, in each case, then the snubbing will eventually tail off. Effects may look logical on paper. Circuitry may even demonstrate a degree of functionality over a short-term and narrow line/load range - something that has no doubt spawned a host of learned technical articles to be written. I've got a host of them. Only testing over the full line/load and environmental range can reveal whether the components selected can always function practically, as intended. This may sound like bullshit to many, but until you've actually scoped the current and voltage waveforms, I would at least advise caution. The actively switched snubber, that returns energy to the flyback load (and can facilitate ZVS in both main and snubber switches), is promising, but requires a variable frequency and timing control that is not simple. Primary switch turn-on current may be negative, a behavior that causes many control methods to react adversely/ chaotically. This doesn't prevent it's use in some practical circuits, with varying effective advantage. In many cases, it is only required to function over a well-defined range of operating conditions, including the transient or temporary sub-optimal. If energy is collected somewhere, it can always be re-converted by a separate circuit, synchronously or otherwise, if the cost of the aditional complexity is justified. RL
Reply by ●May 25, 20162016-05-25
On Tue, 24 May 2016 16:41:44 -0700, klaus.kragelund wrote:> Hey > > Been trying to find the post with the lossless snubber, with AFAIR a > capacitor from the drain node to a regenerative point. > > I am working on a 2 switch flyback and some other schemes, but would > like to try that novel idea out.... > > Anyone knows a pointer to the thread? > > Regards > > KlausI'll have to go look at whatever clever idea I had. The circuit ended up not working but not, I think, because of my inadequate snubbing. A circuit that I did not work on directly, but which I know worked well, was a fairly high-power flyback that just had a diode-capacitor snubber, but which then had a switcher from the snubber cap's voltage back to the primary DC rail. I can't remember whether it was called an active snubber or a regenerative snubber, but the circuit worked. (The company went down the tubes -- it was a startup trying to make a super-efficient solar panel inverter that did not use electrolytics anywhere, and would, thus, "last forever". It was run by someone with a PhD in engineering, and I'm pretty sure it died due to lack of a sales and marketing network.) -- Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com
Reply by ●May 25, 20162016-05-25
On Wed, 25 May 2016 11:31:17 -0500, Tim Wescott <tim@seemywebsite.com> wrote:>On Tue, 24 May 2016 16:41:44 -0700, klaus.kragelund wrote: > >> Hey >> >> Been trying to find the post with the lossless snubber, with AFAIR a >> capacitor from the drain node to a regenerative point. >> >> I am working on a 2 switch flyback and some other schemes, but would >> like to try that novel idea out.... >> >> Anyone knows a pointer to the thread? >> >> Regards >> >> Klaus > >I'll have to go look at whatever clever idea I had. The circuit ended up >not working but not, I think, because of my inadequate snubbing. > >A circuit that I did not work on directly, but which I know worked well, >was a fairly high-power flyback that just had a diode-capacitor snubber, >but which then had a switcher from the snubber cap's voltage back to the >primary DC rail. I can't remember whether it was called an active >snubber or a regenerative snubber, but the circuit worked. > >(The company went down the tubes -- it was a startup trying to make a >super-efficient solar panel inverter that did not use electrolytics >anywhere, and would, thus, "last forever". It was run by someone with a >PhD in engineering, and I'm pretty sure it died due to lack of a sales >and marketing network.)"It was run by someone with a _PhD_ in engineering" _is_ probably why it failed >:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Liberalism: Dictatorship By The People Who Think They Know Best
Reply by ●May 25, 20162016-05-25
On 5/25/2016 11:35 AM, Jim Thompson wrote:> On Wed, 25 May 2016 11:31:17 -0500, Tim Wescott <tim@seemywebsite.com> > wrote: > >> On Tue, 24 May 2016 16:41:44 -0700, klaus.kragelund wrote: >> >>> Hey >>> >>> Been trying to find the post with the lossless snubber, with AFAIR a >>> capacitor from the drain node to a regenerative point. >>> >>> I am working on a 2 switch flyback and some other schemes, but would >>> like to try that novel idea out.... >>> >>> Anyone knows a pointer to the thread? >>> >>> Regards >>> >>> Klaus >> >> I'll have to go look at whatever clever idea I had. The circuit ended up >> not working but not, I think, because of my inadequate snubbing. >> >> A circuit that I did not work on directly, but which I know worked well, >> was a fairly high-power flyback that just had a diode-capacitor snubber, >> but which then had a switcher from the snubber cap's voltage back to the >> primary DC rail. I can't remember whether it was called an active >> snubber or a regenerative snubber, but the circuit worked. >> >> (The company went down the tubes -- it was a startup trying to make a >> super-efficient solar panel inverter that did not use electrolytics >> anywhere, and would, thus, "last forever". It was run by someone with a >> PhD in engineering, and I'm pretty sure it died due to lack of a sales >> and marketing network.) > > "It was run by someone with a _PhD_ in engineering" _is_ probably why > it failed >:-} > > ...Jim ThompsonWhy do you have to be so hateful? You're no jewel, yourself.
Reply by ●May 25, 20162016-05-25
On Wed, 25 May 2016 09:35:47 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Wed, 25 May 2016 11:31:17 -0500, Tim Wescott <tim@seemywebsite.com> >wrote: > >>On Tue, 24 May 2016 16:41:44 -0700, klaus.kragelund wrote: >> >>> Hey >>> >>> Been trying to find the post with the lossless snubber, with AFAIR a >>> capacitor from the drain node to a regenerative point. >>> >>> I am working on a 2 switch flyback and some other schemes, but would >>> like to try that novel idea out.... >>> >>> Anyone knows a pointer to the thread? >>> >>> Regards >>> >>> Klaus >> >>I'll have to go look at whatever clever idea I had. The circuit ended up >>not working but not, I think, because of my inadequate snubbing. >> >>A circuit that I did not work on directly, but which I know worked well, >>was a fairly high-power flyback that just had a diode-capacitor snubber, >>but which then had a switcher from the snubber cap's voltage back to the >>primary DC rail. I can't remember whether it was called an active >>snubber or a regenerative snubber, but the circuit worked. >> >>(The company went down the tubes -- it was a startup trying to make a >>super-efficient solar panel inverter that did not use electrolytics >>anywhere, and would, thus, "last forever". It was run by someone with a >>PhD in engineering, and I'm pretty sure it died due to lack of a sales >>and marketing network.) > >"It was run by someone with a _PhD_ in engineering" _is_ probably why >it failed >:-} > > ...Jim ThompsonThey probably had lots of data graphs of diode curves and such, but no actual working product. Cheers
