It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this true? For example, here, the transistor simply turns on and off, providing pulses to the transformer, right? http://www.repairfaq.org/sam/smpsbd.gif Would SMPSes be more efficient if their transformers were fed high-frequency AC instead of high-frequency pulsed DC (for example, by using an H-bridge to provide a negative voltage across the transformer primary for the second half of each cycle)? Thanks, Michael
smps: AC or pulsed DC fed into transformer?
Started by ●March 15, 2016
Reply by ●March 15, 20162016-03-15
On Tue, 15 Mar 2016 12:23:29 -0700 (PDT), mrdarrett@gmail.com wrote:>It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this true? > >For example, here, the transistor simply turns on and off, providing pulses to the transformer, right? > >http://www.repairfaq.org/sam/smpsbd.gif > > >Would SMPSes be more efficient if their transformers were fed high-frequency AC instead of high-frequency pulsed DC (for example, by using an H-bridge to provide a negative voltage across the transformer primary for the second half of each cycle)? > >Thanks, > >MichaelHigh Frequency chopped DC is equal to High Frequency AC. I.T. I.S. A.C. w.
Reply by ●March 15, 20162016-03-15
On Tue, 15 Mar 2016 12:23:29 -0700 (PDT), mrdarrett@gmail.com wrote:>It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this true? > >For example, here, the transistor simply turns on and off, providing pulses to the transformer, right? > >http://www.repairfaq.org/sam/smpsbd.gif > > >Would SMPSes be more efficient if their transformers were fed high-frequency AC instead of high-frequency pulsed DC (for example, by using an H-bridge to provide a negative voltage across the transformer primary for the second half of each cycle)? > >Thanks, > >MichaelYes. But flybacks take fewer external parts. ...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 ●March 15, 20162016-03-15
On Tuesday, March 15, 2016 at 1:06:49 PM UTC-7, Jim Thompson wrote:> On Tue, 15 Mar 2016 12:23:29 -0700 (PDT), mrdarrett@gmail.com wrote: > > >It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this true? > > > >For example, here, the transistor simply turns on and off, providing pulses to the transformer, right? > > > >http://www.repairfaq.org/sam/smpsbd.gif > > > > > >Would SMPSes be more efficient if their transformers were fed high-frequency AC instead of high-frequency pulsed DC (for example, by using an H-bridge to provide a negative voltage across the transformer primary for the second half of each cycle)? > > > >Thanks, > > > >Michael > > Yes. But flybacks take fewer external parts. > > ...Jim ThompsonOh! It's a cost-savings thing, then. Thanks, Michael
Reply by ●March 15, 20162016-03-15
<mrdarrett@gmail.com> wrote in message news:9bcd7f2a-6040-4c60-a214-c875e7a135bb@googlegroups.com...> On Tuesday, March 15, 2016 at 1:06:49 PM UTC-7, Jim Thompson wrote: >> On Tue, 15 Mar 2016 12:23:29 -0700 (PDT), mrdarrett@gmail.com wrote: >> >> >It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this >> >true? >> > >> >For example, here, the transistor simply turns on and off, providing >> >pulses to the transformer, right? >> > >> >http://www.repairfaq.org/sam/smpsbd.gif >> > >> > >> >Would SMPSes be more efficient if their transformers were fed >> >high-frequency AC instead of high-frequency pulsed DC (for example, by >> >using an H-bridge to provide a negative voltage across the transformer >> >primary for the second half of each cycle)? >> > >> >Thanks, >> > >> >Michael >> >> Yes. But flybacks take fewer external parts. >> >> ...Jim Thompson > > > Oh! It's a cost-savings thing, then.One big motivation is higher frequency allows smaller cheaper reactive components. The penalty is running into transistor switching times, ferrite losses and rectifier Trr. Not studied this area - but I think semi-resonant SMPSUs are the answer to that. If I understand it correctly - they're sort of AC transformer drive instead of DC pulses.
Reply by ●March 15, 20162016-03-15
On Tue, 15 Mar 2016 12:23:29 -0700 (PDT), mrdarrett@gmail.com wrote:>It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this true? > >For example, here, the transistor simply turns on and off, providing pulses to the transformer, right? > >http://www.repairfaq.org/sam/smpsbd.gif > > >Would SMPSes be more efficient if their transformers were fed high-frequency AC instead of high-frequency pulsed DC (for example, by using an H-bridge to provide a negative voltage across the transformer primary for the second half of each cycle)? > >Thanks, > >MichaelReally big (like kilowatt) switching supplies are often forward converters, with symmetric square-wave drive, no DC component, into the transformer. No DC in the transformer core is more efficient. http://www.industrial-electronics.com/image/7_33.jpg http://jugandi.com/ebooks/eXe_Power%20Supplies/Power_Supplies/image150a.png https://dl.dropboxusercontent.com/u/53724080/Circuits/ESM/ESM_power_B.pdf There are also some clever resonant designs that run real AC (sine waves) through the magnetics. Small, cheap supplies work well with the flyback topology. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●March 15, 20162016-03-15
On Tuesday, March 15, 2016 at 1:53:20 PM UTC-7, John Larkin wrote:> On Tue, 15 Mar 2016 12:23:29 -0700 (PDT), mrdarrett@gmail.com wrote: > > >It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this true? > > > >For example, here, the transistor simply turns on and off, providing pulses to the transformer, right? > > > >http://www.repairfaq.org/sam/smpsbd.gif > > > > > >Would SMPSes be more efficient if their transformers were fed high-frequency AC instead of high-frequency pulsed DC (for example, by using an H-bridge to provide a negative voltage across the transformer primary for the second half of each cycle)? > > > >Thanks, > > > >Michael > > Really big (like kilowatt) switching supplies are often forward > converters, with symmetric square-wave drive, no DC component, into > the transformer. No DC in the transformer core is more efficient. > > http://www.industrial-electronics.com/image/7_33.jpg > > http://jugandi.com/ebooks/eXe_Power%20Supplies/Power_Supplies/image150a.png > > https://dl.dropboxusercontent.com/u/53724080/Circuits/ESM/ESM_power_B.pdf > > > There are also some clever resonant designs that run real AC (sine > waves) through the magnetics. > > Small, cheap supplies work well with the flyback topology. > > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.comOk, thanks! Forward Converter... new vocabulary words for today :) Michael
Reply by ●March 15, 20162016-03-15
<mrdarrett@gmail.com> wrote in message news:8ea32720-d16b-4b01-be4a-2158b8466282@googlegroups.com...> On Tuesday, March 15, 2016 at 1:53:20 PM UTC-7, John Larkin wrote: >> On Tue, 15 Mar 2016 12:23:29 -0700 (PDT), mrdarrett@gmail.com wrote: >> >> >It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this >> >true? >> > >> >For example, here, the transistor simply turns on and off, providing >> >pulses to the transformer, right? >> > >> >http://www.repairfaq.org/sam/smpsbd.gif >> > >> > >> >Would SMPSes be more efficient if their transformers were fed >> >high-frequency AC instead of high-frequency pulsed DC (for example, by >> >using an H-bridge to provide a negative voltage across the transformer >> >primary for the second half of each cycle)? >> > >> >Thanks, >> > >> >Michael >> >> Really big (like kilowatt) switching supplies are often forward >> converters, with symmetric square-wave drive, no DC component, into >> the transformer. No DC in the transformer core is more efficient. >> >> http://www.industrial-electronics.com/image/7_33.jpg >> >> http://jugandi.com/ebooks/eXe_Power%20Supplies/Power_Supplies/image150a.png >> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/ESM/ESM_power_B.pdf >> >> >> There are also some clever resonant designs that run real AC (sine >> waves) through the magnetics. >> >> Small, cheap supplies work well with the flyback topology. >> >> >> -- >> >> John Larkin Highland Technology, Inc >> picosecond timing precision measurement >> >> jlarkin att highlandtechnology dott com >> http://www.highlandtechnology.com > > > Ok, thanks! > > Forward Converter... new vocabulary words for today :)Forward converters don't have to be as big as the examples JL mentioned. The early PC/AT psus were often flyback, but forward converters became pretty much the standard once the ratings got to around 200W. There's plenty of off the shelf controller chips to chose from and also plenty of appnotes with example circuits. The SG3524 is just one of many that springs readily to mind. The KA7500 is popular in ATX supplies, so there may be a free development sample gathering dust in the loft. AFAICR: the TL494 is another common choice. Those 3 part numbers will find manufacturers that have other similar parts on offer.
Reply by ●March 15, 20162016-03-15
On Tue, 15 Mar 2016 14:17:26 -0700 (PDT), mrdarrett@gmail.com wrote:>On Tuesday, March 15, 2016 at 1:53:20 PM UTC-7, John Larkin wrote: >> On Tue, 15 Mar 2016 12:23:29 -0700 (PDT), mrdarrett@gmail.com wrote: >> >> >It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this true? >> > >> >For example, here, the transistor simply turns on and off, providing pulses to the transformer, right? >> > >> >http://www.repairfaq.org/sam/smpsbd.gif >> > >> > >> >Would SMPSes be more efficient if their transformers were fed high-frequency AC instead of high-frequency pulsed DC (for example, by using an H-bridge to provide a negative voltage across the transformer primary for the second half of each cycle)? >> > >> >Thanks, >> > >> >Michael >> >> Really big (like kilowatt) switching supplies are often forward >> converters, with symmetric square-wave drive, no DC component, into >> the transformer. No DC in the transformer core is more efficient. >> >> http://www.industrial-electronics.com/image/7_33.jpg >> >> http://jugandi.com/ebooks/eXe_Power%20Supplies/Power_Supplies/image150a.png >> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/ESM/ESM_power_B.pdf >> >> >> There are also some clever resonant designs that run real AC (sine >> waves) through the magnetics. >> >> Small, cheap supplies work well with the flyback topology. >> >> >> -- >> >> John Larkin Highland Technology, Inc >> picosecond timing precision measurement >> >> jlarkin att highlandtechnology dott com >> http://www.highlandtechnology.com > > >Ok, thanks! > >Forward Converter... new vocabulary words for today :) > >MichaelA few more Forward Flyback Buck Boost Cuk Sepic Resonant Cockroft-Walton Royer Baxandall (there must be more) -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●March 15, 20162016-03-15
On Tue, 15 Mar 2016 15:16:25 -0700, John Larkin wrote:> On Tue, 15 Mar 2016 14:17:26 -0700 (PDT), mrdarrett@gmail.com wrote: > >>On Tuesday, March 15, 2016 at 1:53:20 PM UTC-7, John Larkin wrote: >>> On Tue, 15 Mar 2016 12:23:29 -0700 (PDT), mrdarrett@gmail.com wrote: >>> >>> >It seems to me that flyback SMPSes use pulsed DC instead of AC. Is >>> >this true? >>> > >>> >For example, here, the transistor simply turns on and off, providing >>> >pulses to the transformer, right? >>> > >>> >http://www.repairfaq.org/sam/smpsbd.gif >>> > >>> > >>> >Would SMPSes be more efficient if their transformers were fed >>> >high-frequency AC instead of high-frequency pulsed DC (for example, >>> >by using an H-bridge to provide a negative voltage across the >>> >transformer primary for the second half of each cycle)? >>> > >>> >Thanks, >>> > >>> >Michael >>> >>> Really big (like kilowatt) switching supplies are often forward >>> converters, with symmetric square-wave drive, no DC component, into >>> the transformer. No DC in the transformer core is more efficient. >>> >>> http://www.industrial-electronics.com/image/7_33.jpg >>> >>> http://jugandi.com/ebooks/eXe_Power%20Supplies/Power_Supplies/image150a.png>>> >>> https://dl.dropboxusercontent.com/u/53724080/Circuits/ESM/ESM_power_B.pdf>>> >>> >>> There are also some clever resonant designs that run real AC (sine >>> waves) through the magnetics. >>> >>> Small, cheap supplies work well with the flyback topology. >>> >>> >>> -- >>> >>> John Larkin Highland Technology, Inc picosecond timing >>> precision measurement >>> >>> jlarkin att highlandtechnology dott com >>> http://www.highlandtechnology.com >> >> >>Ok, thanks! >> >>Forward Converter... new vocabulary words for today :) >> >>Michael > > > A few more > > Forward > > Flyback > > Buck > > Boost > > Cuk > > Sepic > > Resonant > > Cockroft-Walton > > Royer > > Baxandall > > (there must be more)There are. Not least many sub-categories of the above!
