Forums

My first switcher

Started by George Herold January 15, 2016
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.   

  
 
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. We have some products where the power supplies occupy half the board. -- John Larkin Highland Technology, Inc lunatic fringe electronics
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
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. I spent some time going over switcher design.. and now I want to apply all those equations I had to derive. I'm not sure the linear are going to cut it... just a tad too much power. (~10V @ 0.5A) I've used those little potted CUI converters as inverters... I was looking at the LM43600 a bit spendy, but easy to invert.
> > We have some products where the power supplies occupy half the board.
Grin.. I was thinking we could sell a box with a bunch of Phihong wall warts inside and one power switch.. we'd just have to keep the box nailed shut so no one could look inside. George H.
> > > -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics
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.
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. I spent some time going over switcher design.. and
>now I want to apply all those equations I had to derive. >I'm not sure the linear are going to cut it... just a tad too much power. >(~10V @ 0.5A) I've used those little potted CUI converters as inverters... > >I was looking at the LM43600 a bit spendy, but easy to invert. >> >> We have some products where the power supplies occupy half the board. > >Grin.. I was thinking we could sell a box with a bunch of Phihong wall >warts inside and one power switch.. we'd just have to keep the box nailed >shut so no one could look inside.
There are some dual, bipolar warts, and a few 3-out, like +-12 and +5. There are not many negative-to-negative switcher chips around. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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.
> > I spent some time going over switcher design.. and > >now I want to apply all those equations I had to derive. > >I'm not sure the linear are going to cut it... just a tad too much power. > >(~10V @ 0.5A) I've used those little potted CUI converters as inverters... > > > >I was looking at the LM43600 a bit spendy, but easy to invert. > >> > >> We have some products where the power supplies occupy half the board. > > > >Grin.. I was thinking we could sell a box with a bunch of Phihong wall > >warts inside and one power switch.. we'd just have to keep the box nailed > >shut so no one could look inside. > > There are some dual, bipolar warts, and a few 3-out, like +-12 and +5. > > There are not many negative-to-negative switcher chips around. > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
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
> > > > I spent some time going over switcher design.. and > > >now I want to apply all those equations I had to derive. > > >I'm not sure the linear are going to cut it... just a tad too much power. > > >(~10V @ 0.5A) I've used those little potted CUI converters as inverters... > > > > > >I was looking at the LM43600 a bit spendy, but easy to invert. > > >> > > >> We have some products where the power supplies occupy half the board. > > > > > >Grin.. I was thinking we could sell a box with a bunch of Phihong wall > > >warts inside and one power switch.. we'd just have to keep the box nailed > > >shut so no one could look inside. > > > > There are some dual, bipolar warts, and a few 3-out, like +-12 and +5. > > > > There are not many negative-to-negative switcher chips around. > > > > -- > > > > John Larkin Highland Technology, Inc > > picosecond timing precision measurement > > > > jlarkin att highlandtechnology dott com > > http://www.highlandtechnology.com
On Fri, 15 Jan 2016 11:31:46 -0800 (PST), George Herold
<gherold@teachspin.com> 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.)
See example on sheet 4. It works.
>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.)
Beer can be fun, too. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com