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.> > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
My first switcher
Started by ●January 15, 2016
Reply by ●January 15, 20162016-01-15
Reply by ●January 15, 20162016-01-15
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. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●January 15, 20162016-01-15
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 Belleman
Reply by ●January 15, 20162016-01-15
On Fri, 15 Jan 2016 23:01:44 +0100, 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 BellemanWell, more like an input transition results in a state transition whenever the logic gets around to it -- which may be why people object to such things. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●January 15, 20162016-01-15
On Fri, 15 Jan 2016 23:01:44 +0100, jeroen Belleman <jeroen@nospam.please> 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 Belleman >I do the occasional small async design, and sometimes we do async parts of an FPGA, if we can fool the compiler into letting us do it. But it doesn't scale, and a big async design is likely to be trouble. Async logic for CPUs is a repetitive fad. Wiki calls async design "an active area of research" which it has been for decades. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●January 15, 20162016-01-15
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.
Reply by ●January 15, 20162016-01-15
On Fri, 15 Jan 2016 17:06:16 -0600, "Tim Williams" <tiwill@seventransistorlabs.com> 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.You can even regulate the negative output, see... OldStyleBuckSwitcherWithAddedNegativeOutput.pdf on the S.E.D/Schematics Page of my website. That's what I was doing ~1980, using LM339's as the controller chip ;-)> >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. > > >...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●January 15, 20162016-01-15
"Jim Thompson" wrote in message news:uf1j9bhhuhhd1gntc3es7o0oac6f98tslq@4ax.com...> You can even regulate the negative output, see... > > OldStyleBuckSwitcherWithAddedNegativeOutput.pdf > > on the S.E.D/Schematics Page of my website. > > That's what I was doing ~1980, using LM339's as the controller chip > ;-)Eww-w-w-ww! I'd rather use an MC34063! You did say "old" ;-) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●January 15, 20162016-01-15
On Fri, 15 Jan 2016 18:05:08 -0600, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>"Jim Thompson" wrote in message >news:uf1j9bhhuhhd1gntc3es7o0oac6f98tslq@4ax.com... >> You can even regulate the negative output, see... >> >> OldStyleBuckSwitcherWithAddedNegativeOutput.pdf >> >> on the S.E.D/Schematics Page of my website. >> >> That's what I was doing ~1980, using LM339's as the controller chip >> ;-) > > >Eww-w-w-ww! I'd rather use an MC34063! > >You did say "old" ;-) > >TimMC34063 didn't exist, and some of us knew how to roll our own controller loops >:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●January 15, 20162016-01-15
