On Sat, 16 Jan 2016 10:52:14 +0800, pedro <me@privacy.net> wrote:>On Fri, 15 Jan 2016 11:08:55 -0800, John Larkin ><jjlarkin@highlandtechnology.com> wrote: > >>We use one 3-t 7805 drop-in replacement blob that's a switcher, cheap. > >John, can you supply a link to those? We've been using a ROHM >switcher in a TO-220 but cheap they aren't.Doh! Should have delved further and seen George's reply ...
My first switcher
Started by ●January 15, 2016
Reply by ●January 15, 20162016-01-15
Reply by ●January 16, 20162016-01-16
On Sat, 16 Jan 2016 11:13:33 +0800, pedro <me@privacy.net> wrote:>On Sat, 16 Jan 2016 10:52:14 +0800, pedro <me@privacy.net> wrote: > >>On Fri, 15 Jan 2016 11:08:55 -0800, John Larkin >><jjlarkin@highlandtechnology.com> wrote: >> >>>We use one 3-t 7805 drop-in replacement blob that's a switcher, cheap. >> >>John, can you supply a link to those? We've been using a ROHM >>switcher in a TO-220 but cheap they aren't. > >Doh! Should have delved further and seen George's reply ...The CUI and Murata and Recom dc/dc bricks seem to be fine. But don't believe their short-circuit specs unless you verify them yourself, and then still don't believe them if you can help it. The CUI PDS1 parts are really cool. Isolated +- output. I use them even when I don't need the isolation. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●January 16, 20162016-01-16
On Fri, 15 Jan 2016 10:52:19 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Friday, January 15, 2016 at 12:46:41 PM UTC-5, Tim Wescott wrote: >> On Fri, 15 Jan 2016 08:43:30 -0800, George Herold wrote: >> >> > Hi all, Well I get to do a SMPS. There are boat loads of IC's out >> > there and I'm looking for recommendations. (I better go re read AoE3) >> > I need a number of output voltages. +15V, +5V, -5V, -15V. and +24V. >> > maximum current of 0.5A on any one. >> > My current plan is to run the whole thing from a 24V wall wart or brick. >> > Price and size is not too much of an issue, I guess fewer external parts >> > would be nice... Say with the switching transistor inside the IC. >> > >> > TIA George H. >> >> What JL said, plus -- if your volume is low then you may want to stick >> with Linear Technology parts. They've never failed me, they're easier to >> design in than other brands, but they're more expensive than equivalent >> parts from other brands. As a bonus, LT Spice seems to be pretty damned >> accurate when you're trying out switching supply circuits with Linear >> switchers (for some odd reason). >> >> If you're going to be shipping 100000 units, Linear Tech may not be the >> best choice. >> >> -- >> >> Tim Wescott >> Wescott Design Services >> http://www.wescottdesign.com > >Yeah low volume 100's. I like LT stuff too. >The LT8471 looks interesting, >http://cds.linear.com/docs/en/datasheet/8471fd.pdf > >~$8 in onesies... not much stock at DK... > >George H.We use a lot of LTM8023, which is a brick that includes the switcher, inductor, and caps. It's not cheap, but it's convenient and very quiet. It can do step-down buck or pos-to-neg conversion. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●January 16, 20162016-01-16
"John Larkin" wrote in message news:3akj9btrmab68aoavqklct32b9t3m3n789@4ax.com...> The CUI and Murata and Recom dc/dc bricks seem to be fine. But don't > believe their short-circuit specs unless you verify them yourself, and > then still don't believe them if you can help it. > > The CUI PDS1 parts are really cool. Isolated +- output. I use them > even when I don't need the isolation.Yeah, have to be careful with the ones that are basically just choppers, there's no current limiting or protection or anything. Short it for a second or two and poof, out oozes a teensy bit of magic smoke, in condensed form... if you're even that lucky. The bigger ones (3W+?) I think tend to be proper current mode controllers, and say they're fine to short forever. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●January 16, 20162016-01-16
On Sat, 16 Jan 2016 02:42:36 -0600, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>"John Larkin" wrote in message >news:3akj9btrmab68aoavqklct32b9t3m3n789@4ax.com... >> The CUI and Murata and Recom dc/dc bricks seem to be fine. But don't >> believe their short-circuit specs unless you verify them yourself, and >> then still don't believe them if you can help it. >> >> The CUI PDS1 parts are really cool. Isolated +- output. I use them >> even when I don't need the isolation. > >Yeah, have to be careful with the ones that are basically just choppers, >there's no current limiting or protection or anything. Short it for a >second or two and poof, out oozes a teensy bit of magic smoke, in >condensed form... if you're even that lucky. > >The bigger ones (3W+?) I think tend to be proper current mode controllers, >and say they're fine to short forever. > >TimOne part saye infinite short duration somewhere on the data sheet, and 8 hours somewhere else. One CUI part, VASD1, claims 1 second short withstand, but it blows up in under 100 ms. I added an LM317L ahead of it as a current limiter. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●January 16, 20162016-01-16
On Friday, January 15, 2016 at 4:25:58 PM UTC-5, John Larkin wrote:> On Fri, 15 Jan 2016 12:09:14 -0800 (PST), George Herold > <gherold@teachspin.com> wrote: > > >On Friday, January 15, 2016 at 2:52:48 PM UTC-5, John Larkin wrote: > >> On Fri, 15 Jan 2016 11:36:27 -0800 (PST), George Herold > >> <gherold@teachspin.com> wrote: > >> > >> >On Friday, January 15, 2016 at 2:31:51 PM UTC-5, George Herold wrote: > >> >> On Friday, January 15, 2016 at 2:09:09 PM UTC-5, John Larkin wrote: > >> >> > On Fri, 15 Jan 2016 10:47:41 -0800 (PST), George Herold > >> >> > <gherold@teachspin.com> wrote: > >> >> > > >> >> > >On Friday, January 15, 2016 at 11:55:27 AM UTC-5, John Larkin wrote: > >> >> > >> On Fri, 15 Jan 2016 08:43:30 -0800 (PST), George Herold > >> >> > >> <gherold@teachspin.com> wrote: > >> >> > >> > >> >> > >> >Hi all, Well I get to do a SMPS. There are boat loads of IC's > >> >> > >> >out there and I'm looking for recommendations. (I better go re read AoE3) > >> >> > >> >I need a number of output voltages. +15V, +5V, -5V, -15V. and +24V. > >> >> > >> >maximum current of 0.5A on any one. > >> >> > >> >My current plan is to run the whole thing from a 24V wall wart or brick. > >> >> > >> >Price and size is not too much of an issue, I guess fewer external parts would > >> >> > >> >be nice... Say with the switching transistor inside the IC. > >> >> > >> > > >> >> > >> >TIA > >> >> > >> >George H. > >> >> > >> > > >> >> > >> > > >> >> > >> > > >> >> > >> > >> >> > >> The +24 output is easy! > >> >> > >> > >> >> > >> One way to get multiple outputs is to do a forward or flyback > >> >> > >> converter with a custom transformer with multiple secondaries. The > >> >> > >> transformer is a nuisance to procure and cross-regulation is mediocre. > >> >> > >> That makes sense in high volume, maybe. > >> >> > >> > >> >> > >> So, the usual way is a mess of buck switchers and linear regs. +15 > >> >> > >> might be a linear off +24. For negative outputs, you can > >> >> > >> > >> >> > >> 1. Buy little charge pump inverter chips, for modest currents. Cheap, > >> >> > >> easy, no inductor. > >> >> > >> > >> >> > >> 2. Charge pump yourself off the positive switcher > >> >> > >> > >> >> > >> 3. Build a proper Cuk converter if you need a lot of negative power. > >> >> > >> > >> >> > >> 4. Buy some potted isolated DC/DC converters. For about $4, you can > >> >> > >> get a couple of watts of +24 to +-5 volt converter. Not much design > >> >> > >> challenge. > >> >> > > > >> >> > >Well geesh you're no fun. > >> >> > > >> >> > When a potted thing costs a few bucks, it's not sensible to design > >> >> > your own switcher. The parts cost may exceed the price of the brick. > >> >> > Agree, no fun. > >> >> > > >> >> > We use one 3-t 7805 drop-in replacement blob that's a switcher, cheap. > >> >> > It will also make V+ to -5 of you connect it different. > >> >> > >> >> Huh.. I was just looking at those. > >> >> http://www.cui.com/product/resource/v78-500.pdf > >> >> > >> >> How do I get -V from one of those? > >> >> (I mean there are only three terminal... switching ground and output > >> >> seems like it will screw up the input.) > >> >> I was thinking I could use those for +V and a switcher for -V... > >> >> but if I can just use 4 of those, I'm done. > >> >> (which is boring.. but it's Friday and I could leave early and buy a beer.) > >> >> > >> >> George H. > >> > > >> >Never mind.. I didn't read to the end of my own linked spec sheet. > >> >I'm sorry to say I think I'm done... order to digikey. > >> >(And I don't get to design a switcher... grumble.) > >> > > >> >GH > >> > >> Do something more exotic. A kilovolt switcher. 250 amps polyphase. 50 > >> MHz GaN. > > > >Grin.. well there is always plenty to do. I've got this digital hairball > >circuit I've got to get to... I was going to post a question on SEB, > >maybe this weekend. > > > >George H. > > Did you inherit an async logic hairball or something? Throw it away > and start fresh. > > I did rat's nest logic when I was a kid, but some kind soul took me > aside one day and showed me the True Path of clean synchronous state > machines. > > DEC built zillions of minicomputers, up through early PDP-11s, with > hairball logic. They usually worked, but not always. There were famous > 10-instruction programs that would lock up a PDP-11.No not async.. the first thing I do is sync up the start pulse with the clock. But I hardly do any digital things.... (The last was ~1995 pulse programmer for an NMR.. LS ttl.) Anyway I'll start a thread on SEB. I think most here would suggest throwing a uC at the problem. later, George H.> > > > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
Reply by ●January 16, 20162016-01-16
On Friday, January 15, 2016 at 5:01:52 PM UTC-5, jeroen Belleman wrote:> On 15/01/16 22:25, John Larkin wrote: > > On Fri, 15 Jan 2016 12:09:14 -0800 (PST), George Herold > > <gherold@teachspin.com> wrote: > > > >> On Friday, January 15, 2016 at 2:52:48 PM UTC-5, John Larkin wrote: > >>> On Fri, 15 Jan 2016 11:36:27 -0800 (PST), George Herold > >>> <gherold@teachspin.com> wrote: > >>> > >>>> On Friday, January 15, 2016 at 2:31:51 PM UTC-5, George Herold wrote: > >>>>> On Friday, January 15, 2016 at 2:09:09 PM UTC-5, John Larkin wrote: > >>>>>> On Fri, 15 Jan 2016 10:47:41 -0800 (PST), George Herold > >>>>>> <gherold@teachspin.com> wrote: > >>>>>> > >>>>>>> On Friday, January 15, 2016 at 11:55:27 AM UTC-5, John Larkin wrote: > >>>>>>>> On Fri, 15 Jan 2016 08:43:30 -0800 (PST), George Herold > >>>>>>>> <gherold@teachspin.com> wrote: > >>>>>>>> > >>>>>>>>> Hi all, Well I get to do a SMPS. There are boat loads of IC's > >>>>>>>>> out there and I'm looking for recommendations. (I better go re read AoE3) > >>>>>>>>> I need a number of output voltages. +15V, +5V, -5V, -15V. and +24V. > >>>>>>>>> maximum current of 0.5A on any one. > >>>>>>>>> My current plan is to run the whole thing from a 24V wall wart or brick. > >>>>>>>>> Price and size is not too much of an issue, I guess fewer external parts would > >>>>>>>>> be nice... Say with the switching transistor inside the IC. > >>>>>>>>> > >>>>>>>>> TIA > >>>>>>>>> George H. > >>>>>>>>> > >>>>>>>>> > >>>>>>>>> > >>>>>>>> > >>>>>>>> The +24 output is easy! > >>>>>>>> > >>>>>>>> One way to get multiple outputs is to do a forward or flyback > >>>>>>>> converter with a custom transformer with multiple secondaries. The > >>>>>>>> transformer is a nuisance to procure and cross-regulation is mediocre. > >>>>>>>> That makes sense in high volume, maybe. > >>>>>>>> > >>>>>>>> So, the usual way is a mess of buck switchers and linear regs. +15 > >>>>>>>> might be a linear off +24. For negative outputs, you can > >>>>>>>> > >>>>>>>> 1. Buy little charge pump inverter chips, for modest currents. Cheap, > >>>>>>>> easy, no inductor. > >>>>>>>> > >>>>>>>> 2. Charge pump yourself off the positive switcher > >>>>>>>> > >>>>>>>> 3. Build a proper Cuk converter if you need a lot of negative power. > >>>>>>>> > >>>>>>>> 4. Buy some potted isolated DC/DC converters. For about $4, you can > >>>>>>>> get a couple of watts of +24 to +-5 volt converter. Not much design > >>>>>>>> challenge. > >>>>>>> > >>>>>>> Well geesh you're no fun. > >>>>>> > >>>>>> When a potted thing costs a few bucks, it's not sensible to design > >>>>>> your own switcher. The parts cost may exceed the price of the brick. > >>>>>> Agree, no fun. > >>>>>> > >>>>>> We use one 3-t 7805 drop-in replacement blob that's a switcher, cheap. > >>>>>> It will also make V+ to -5 of you connect it different. > >>>>> > >>>>> Huh.. I was just looking at those. > >>>>> http://www.cui.com/product/resource/v78-500.pdf > >>>>> > >>>>> How do I get -V from one of those? > >>>>> (I mean there are only three terminal... switching ground and output > >>>>> seems like it will screw up the input.) > >>>>> I was thinking I could use those for +V and a switcher for -V... > >>>>> but if I can just use 4 of those, I'm done. > >>>>> (which is boring.. but it's Friday and I could leave early and buy a beer.) > >>>>> > >>>>> George H. > >>>> > >>>> Never mind.. I didn't read to the end of my own linked spec sheet. > >>>> I'm sorry to say I think I'm done... order to digikey. > >>>> (And I don't get to design a switcher... grumble.) > >>>> > >>>> GH > >>> > >>> Do something more exotic. A kilovolt switcher. 250 amps polyphase. 50 > >>> MHz GaN. > >> > >> Grin.. well there is always plenty to do. I've got this digital hairball > >> circuit I've got to get to... I was going to post a question on SEB, > >> maybe this weekend. > >> > >> George H. > > > > Did you inherit an async logic hairball or something? Throw it away > > and start fresh. > > > > I did rat's nest logic when I was a kid, but some kind soul took me > > aside one day and showed me the True Path of clean synchronous state > > machines. > > [...] > > I *like* to design the odd asynchronous state machine from time > to time. Contrary to what many people think, it's nothing like > random hairballs. To design them, one uses state transition > tables just like for synchronous logic. The principal difference > is that an input transition results in a state transition immediately, > and not at the next clock. A clocked flipflop is just a little canned > asynchronous state machine, in my view. > > Modern logic design strongly discourages the practice, is true. > > Sorry, a bit OT, although not as much as some well-known frequent > posters here. > > Jeroen BellemanRe: OT... Not at all Jeroen, I'll post my hairball and problem over on S.E.Basics, and if you have comments (or just want to laugh at it) then I'd enjoy that. George H.
Reply by ●January 16, 20162016-01-16
On Friday, January 15, 2016 at 6:06:48 PM UTC-5, Tim Williams wrote:> Use an LM2594 or whatever in that series. They're very easy to use, and > list recommended parts values. > > You can get negative voltages from a buck by using a multi-winding > inductor. This makes +/-5V or 12, or +12/-6V (get -5 using an LDO?) very > simple. Preferably use a synchronous converter like TPS54233, or put a > minimum load on the main output, otherwise the negative rail won't start > up. > > The negative winding is phased so that it looks like a flyback supply, but > it's not actually freewheeling, it's just the buck's diode-clamping phase. > This is why you get a ratio to the main output voltage. (The opposite > phase is supply dependent, and has forward converter action, so you'd need > a choke input filter anyway.) > > Afraid I don't have a drawing or appnote handy, but I think I've seen such > examples in LT datasheets. LT parts are fine too, you're just paying more > for them... > > Tim > > Seven Transistor Labs, LLC > Electrical Engineering Consultation and Contract Design > Website: http://seventransistorlabs.com > > "George Herold" wrote in message > news:12463677-e901-47e4-8014-548207c5dcad@googlegroups.com... > > Hi all, Well I get to do a SMPS. There are boat loads of IC's > out there and I'm looking for recommendations. (I better go re read AoE3) > I need a number of output voltages. +15V, +5V, -5V, -15V. and +24V. > maximum current of 0.5A on any one. > My current plan is to run the whole thing from a 24V wall wart or brick. > Price and size is not too much of an issue, I guess fewer external parts > would > be nice... Say with the switching transistor inside the IC. > > TIA > George H.Thanks Tim... I think the LM2594 is the IC Phil H. likes also. I looked at that too. ON semi makes one that looks more versatile than the TI version. http://www.onsemi.com/pub_link/Collateral/LM2594-D.PDF (nice spec sheet too!) I should order some for "play" time. But unless the noise is horrible it hard to beat the potted CUI part that I found. $4-7, two ceramic caps and it goes both ways. I could use those in other things too. (maybe hang a cap multiplier on the output.. three more parts.) George H.
Reply by ●January 17, 20162016-01-17
On Saturday, 16 January 2016 03:55:27 UTC+11, John Larkin wrote:> On Fri, 15 Jan 2016 08:43:30 -0800 (PST), George Herold > <gherold@teachspin.com> wrote: > > >Hi all, Well I get to do a SMPS. There are boat loads of IC's > >out there and I'm looking for recommendations. (I better go re read AoE3) > >I need a number of output voltages. +15V, +5V, -5V, -15V. and +24V. > >maximum current of 0.5A on any one. > >My current plan is to run the whole thing from a 24V wall wart or brick. > >Price and size is not too much of an issue, I guess fewer external parts > >would be nice... Say with the switching transistor inside the IC. > > > >TIA > >George H. > > > > > > > > The +24 output is easy! > > One way to get multiple outputs is to do a forward or flyback > converter with a custom transformer with multiple secondaries. The > transformer is a nuisance to procure and cross-regulation is mediocre. > That makes sense in high volume, maybe.John Larkin is unwilling to use transformers that he can't buy off the shelf from a broad-line distributor. There's always a transformer winding shop nearby, and you can buy a range of ferrite cores and matching formers from broad-line distributors. It's not rocket science, but your friendly local winding shop will know a lot more about the subject than you will. If you can live with that - and John Larkin obviously finds it difficult - getting small batches of special purpose transformers wound is pretty straight-forward. <snip> -- Bill Sloman, Sydney
