On Thu, 9 Nov 2023 15:14:53 -0800 (PST), Klaus Kragelund <klaus.kragelund@gmail.com> wrote:>Hi > >I am on the lookout for a cheap 1:1 pulse transformer. Will be using it to drive a MOSFET based Solid State Switch. > >I know Larkin has used the DRQ127 > >https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 > >But, I am looking to see if I can find bottom dollar. > >I probably wont go to LCSC, so would prefer a known brand. > >Anyone got a recommendation? > >Cheers > >KlausAre you driving the gate of a fet? What fet?
Cheap pulse 1:1 transformer
Started by ●November 9, 2023
Reply by ●November 10, 20232023-11-10
Reply by ●November 10, 20232023-11-10
John Larkin <jl@997PotHill.com> wrote:> On Fri, 10 Nov 2023 08:28:15 -0500, legg <legg@nospam.magma.ca> wrote: > >> On Thu, 9 Nov 2023 15:14:53 -0800 (PST), Klaus Kragelund >> <klaus.kragelund@gmail.com> wrote: >> >>> Hi >>> >>> I am on the lookout for a cheap 1:1 pulse transformer. Will be using it >>> to drive a MOSFET based Solid State Switch. >>> >>> I know Larkin has used the DRQ127 >>> >>> https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 >>> >>> But, I am looking to see if I can find bottom dollar. >>> >>> I probably wont go to LCSC, so would prefer a known brand. >>> >>> Anyone got a recommendation? >>> >>> Cheers >>> >>> Klaus >> >> Suggest you nail down your requirements first: >> Lpmin >> Vtmin, >> Rdcmax, >> Isolation class, >> prod test level. >> >> Many techniques avoid the requirement of high Lp and Vt. >> >> Be smart or pay. >> >> RL > > Volt-second saturation will exclude small parts that othewise look > good. Ditto leakage inductance. > > Winding capacitance, too. There are cases where I would love to drive > a fet through a transformer, but nothing reasonable works. > >There’s the common-gate FET trick, where you use a small extra FET, with its source connected to the transformer and its gate and drain to the main FET’s source and gate, respectively, with a small storage cap. (The other end of the transformer goes to the main FET’s source as usual. ) Using NFETs, a positive edge conducts via the body diode, turning the main FET on, and a negative one conducts via transistor action, turning it off. It doesn’t matter much what happens in between. Really stretches out the ol’ voltseconds. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Reply by ●November 10, 20232023-11-10
On Thursday, November 9, 2023 at 6:14:58 PM UTC-5, Klaus Kragelund wrote:> Hi > > I am on the lookout for a cheap 1:1 pulse transformer. Will be using it to drive a MOSFET based Solid State Switch. > > I know Larkin has used the DRQ127 > > https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 > > But, I am looking to see if I can find bottom dollar. > > I probably wont go to LCSC, so would prefer a known brand. > > Anyone got a recommendation?If you're looking for cheap, you can't beat capacitor coupling the gate drive. Phillips has a whole chapter in their MOSFET applications handbook on how to do this reliably-wasn't in the market for the technique at the time and skipped it. see page 36 AC-Coupled Gate-Drive Circuits https://www.ti.com/lit/ml/slua618a/slua618a.pdf Looks like the internet lost the Philips handbook...> > Cheers > > Klaus
Reply by ●November 10, 20232023-11-10
On Fri, 10 Nov 2023 16:24:00 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>John Larkin <jl@997PotHill.com> wrote: >> On Fri, 10 Nov 2023 08:28:15 -0500, legg <legg@nospam.magma.ca> wrote: >> >>> On Thu, 9 Nov 2023 15:14:53 -0800 (PST), Klaus Kragelund >>> <klaus.kragelund@gmail.com> wrote: >>> >>>> Hi >>>> >>>> I am on the lookout for a cheap 1:1 pulse transformer. Will be using it >>>> to drive a MOSFET based Solid State Switch. >>>> >>>> I know Larkin has used the DRQ127 >>>> >>>> https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 >>>> >>>> But, I am looking to see if I can find bottom dollar. >>>> >>>> I probably wont go to LCSC, so would prefer a known brand. >>>> >>>> Anyone got a recommendation? >>>> >>>> Cheers >>>> >>>> Klaus >>> >>> Suggest you nail down your requirements first: >>> Lpmin >>> Vtmin, >>> Rdcmax, >>> Isolation class, >>> prod test level. >>> >>> Many techniques avoid the requirement of high Lp and Vt. >>> >>> Be smart or pay. >>> >>> RL >> >> Volt-second saturation will exclude small parts that othewise look >> good. Ditto leakage inductance. >> >> Winding capacitance, too. There are cases where I would love to drive >> a fet through a transformer, but nothing reasonable works. >> >> > >There�s the common-gate FET trick, where you use a small extra FET, with >its source connected to the transformer and its gate and drain to the main >FET�s source and gate, respectively, with a small storage cap. > >(The other end of the transformer goes to the main FET�s source as usual. ) > >Using NFETs, a positive edge conducts via the body diode, turning the main >FET on, and a negative one conducts via transistor action, turning it off. >It doesn�t matter much what happens in between. > >Really stretches out the ol� voltseconds. > >Cheers > >Phil HobbsClever. Given a floating power supply, a dc/dc converter or equivalent, the small tranny can drive a gate driver chip. The tranny can also conduct tiny spikes at the leading and trailing edge of the pulse, and drive a highside flop or schmitt. In my youth, I invented the dual optocoupler totem pole fet gate driver. That needs a floating power supply, a dc/dc or a PV coupler or a bootstrap supply or something. Slow but nice. Nowadays a fast logic coupler can drive a fast gate driver chip.
Reply by ●November 10, 20232023-11-10
fredag den 10. november 2023 kl. 19.27.19 UTC+1 skrev john larkin:> On Fri, 10 Nov 2023 16:24:00 -0000 (UTC), Phil Hobbs > <pcdhSpamM...@electrooptical.net> wrote: > > >John Larkin <j...@997PotHill.com> wrote: > >> On Fri, 10 Nov 2023 08:28:15 -0500, legg <le...@nospam.magma.ca> wrote: > >> > >>> On Thu, 9 Nov 2023 15:14:53 -0800 (PST), Klaus Kragelund > >>> <klaus.k...@gmail.com> wrote: > >>> > >>>> Hi > >>>> > >>>> I am on the lookout for a cheap 1:1 pulse transformer. Will be using it > >>>> to drive a MOSFET based Solid State Switch. > >>>> > >>>> I know Larkin has used the DRQ127 > >>>> > >>>> https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 > >>>> > >>>> But, I am looking to see if I can find bottom dollar. > >>>> > >>>> I probably wont go to LCSC, so would prefer a known brand. > >>>> > >>>> Anyone got a recommendation? > >>>> > >>>> Cheers > >>>> > >>>> Klaus > >>> > >>> Suggest you nail down your requirements first: > >>> Lpmin > >>> Vtmin, > >>> Rdcmax, > >>> Isolation class, > >>> prod test level. > >>> > >>> Many techniques avoid the requirement of high Lp and Vt. > >>> > >>> Be smart or pay. > >>> > >>> RL > >> > >> Volt-second saturation will exclude small parts that othewise look > >> good. Ditto leakage inductance. > >> > >> Winding capacitance, too. There are cases where I would love to drive > >> a fet through a transformer, but nothing reasonable works. > >> > >> > > > >There’s the common-gate FET trick, where you use a small extra FET, with > >its source connected to the transformer and its gate and drain to the main > >FET’s source and gate, respectively, with a small storage cap. > > > >(The other end of the transformer goes to the main FET’s source as usual. ) > > > >Using NFETs, a positive edge conducts via the body diode, turning the main > >FET on, and a negative one conducts via transistor action, turning it off. > >It doesn’t matter much what happens in between. > > > >Really stretches out the ol’ voltseconds. > > > >Cheers > > > >Phil Hobbs > Clever. > > Given a floating power supply, a dc/dc converter or equivalent, the > small tranny can drive a gate driver chip. The tranny can also conduct > tiny spikes at the leading and trailing edge of the pulse, and drive a > highside flop or schmitt.so basically an analogdevices iCoupler
Reply by ●November 10, 20232023-11-10
On Friday, November 10, 2023 at 11:24:08 AM UTC-5, Phil Hobbs wrote:> John Larkin <j...@997PotHill.com> wrote: > > On Fri, 10 Nov 2023 08:28:15 -0500, legg <le...@nospam.magma.ca> wrote: > > > >> On Thu, 9 Nov 2023 15:14:53 -0800 (PST), Klaus Kragelund > >> <klaus.k...@gmail.com> wrote: > >> > >>> Hi > >>> > >>> I am on the lookout for a cheap 1:1 pulse transformer. Will be using it > >>> to drive a MOSFET based Solid State Switch. > >>> > >>> I know Larkin has used the DRQ127 > >>> > >>> https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 > >>> > >>> But, I am looking to see if I can find bottom dollar. > >>> > >>> I probably wont go to LCSC, so would prefer a known brand. > >>> > >>> Anyone got a recommendation? > >>> > >>> Cheers > >>> > >>> Klaus > >> > >> Suggest you nail down your requirements first: > >> Lpmin > >> Vtmin, > >> Rdcmax, > >> Isolation class, > >> prod test level. > >> > >> Many techniques avoid the requirement of high Lp and Vt. > >> > >> Be smart or pay. > >> > >> RL > > > > Volt-second saturation will exclude small parts that othewise look > > good. Ditto leakage inductance. > > > > Winding capacitance, too. There are cases where I would love to drive > > a fet through a transformer, but nothing reasonable works. > > > > > There’s the common-gate FET trick, where you use a small extra FET, with > its source connected to the transformer and its gate and drain to the main > FET’s source and gate, respectively, with a small storage cap. > > (The other end of the transformer goes to the main FET’s source as usual. ) > > Using NFETs, a positive edge conducts via the body diode, turning the main > FET on, and a negative one conducts via transistor action, turning it off. > It doesn’t matter much what happens in between. > > Really stretches out the ol’ voltseconds.How does that increase volt-seconds? It's just a single component replacement of the reverse biased gate discharge speed-up transistor technique. PNP used on NFET.> > Cheers > > Phil Hobbs > > -- > Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / > Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Reply by ●November 10, 20232023-11-10
On Friday, November 10, 2023 at 1:27:19 PM UTC-5, john larkin wrote:> On Fri, 10 Nov 2023 16:24:00 -0000 (UTC), Phil Hobbs > <pcdhSpamM...@electrooptical.net> wrote: > > >John Larkin <j...@997PotHill.com> wrote: > >> On Fri, 10 Nov 2023 08:28:15 -0500, legg <le...@nospam.magma.ca> wrote: > >> > >>> On Thu, 9 Nov 2023 15:14:53 -0800 (PST), Klaus Kragelund > >>> <klaus.k...@gmail.com> wrote: > >>> > >>>> Hi > >>>> > >>>> I am on the lookout for a cheap 1:1 pulse transformer. Will be using it > >>>> to drive a MOSFET based Solid State Switch. > >>>> > >>>> I know Larkin has used the DRQ127 > >>>> > >>>> https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 > >>>> > >>>> But, I am looking to see if I can find bottom dollar. > >>>> > >>>> I probably wont go to LCSC, so would prefer a known brand. > >>>> > >>>> Anyone got a recommendation? > >>>> > >>>> Cheers > >>>> > >>>> Klaus > >>> > >>> Suggest you nail down your requirements first: > >>> Lpmin > >>> Vtmin, > >>> Rdcmax, > >>> Isolation class, > >>> prod test level. > >>> > >>> Many techniques avoid the requirement of high Lp and Vt. > >>> > >>> Be smart or pay. > >>> > >>> RL > >> > >> Volt-second saturation will exclude small parts that othewise look > >> good. Ditto leakage inductance. > >> > >> Winding capacitance, too. There are cases where I would love to drive > >> a fet through a transformer, but nothing reasonable works. > >> > >> > > > >There’s the common-gate FET trick, where you use a small extra FET, with > >its source connected to the transformer and its gate and drain to the main > >FET’s source and gate, respectively, with a small storage cap. > > > >(The other end of the transformer goes to the main FET’s source as usual. ) > > > >Using NFETs, a positive edge conducts via the body diode, turning the main > >FET on, and a negative one conducts via transistor action, turning it off. > >It doesn’t matter much what happens in between. > > > >Really stretches out the ol’ voltseconds. > > > >Cheers > > > >Phil Hobbs > Clever. > > Given a floating power supply, a dc/dc converter or equivalent, the > small tranny can drive a gate driver chip. The tranny can also conduct > tiny spikes at the leading and trailing edge of the pulse, and drive a > highside flop or schmitt. > > In my youth, I invented the dual optocoupler totem pole fet gate > driver. That needs a floating power supply, a dc/dc or a PV coupler or > a bootstrap supply or something. Slow but nice. > > Nowadays a fast logic coupler can drive a fast gate driver chip.If the application is for a MOSFET analog switch, switching speed is not of the essence, duty is very low.
Reply by ●November 10, 20232023-11-10
On 10/11/2023 7:20 pm, Fred Bloggs wrote:> On Friday, November 10, 2023 at 11:24:08 AM UTC-5, Phil Hobbs wrote: >> John Larkin <j...@997PotHill.com> wrote: >>> On Fri, 10 Nov 2023 08:28:15 -0500, legg <le...@nospam.magma.ca> wrote: >>> >>>> On Thu, 9 Nov 2023 15:14:53 -0800 (PST), Klaus Kragelund >>>> <klaus.k...@gmail.com> wrote: >>>> >>>>> Hi >>>>> >>>>> I am on the lookout for a cheap 1:1 pulse transformer. Will be using it >>>>> to drive a MOSFET based Solid State Switch. >>>>> >>>>> I know Larkin has used the DRQ127 >>>>> >>>>> https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 >>>>> >>>>> But, I am looking to see if I can find bottom dollar. >>>>> >>>>> I probably wont go to LCSC, so would prefer a known brand. >>>>> >>>>> Anyone got a recommendation? >>>>> >>>>> Cheers >>>>> >>>>> Klaus >>>> >>>> Suggest you nail down your requirements first: >>>> Lpmin >>>> Vtmin, >>>> Rdcmax, >>>> Isolation class, >>>> prod test level. >>>> >>>> Many techniques avoid the requirement of high Lp and Vt. >>>> >>>> Be smart or pay. >>>> >>>> RL >>> >>> Volt-second saturation will exclude small parts that othewise look >>> good. Ditto leakage inductance. >>> >>> Winding capacitance, too. There are cases where I would love to drive >>> a fet through a transformer, but nothing reasonable works. >>> >>> >> There’s the common-gate FET trick, where you use a small extra FET, with >> its source connected to the transformer and its gate and drain to the main >> FET’s source and gate, respectively, with a small storage cap. >> >> (The other end of the transformer goes to the main FET’s source as usual. ) >> >> Using NFETs, a positive edge conducts via the body diode, turning the main >> FET on, and a negative one conducts via transistor action, turning it off. >> It doesn’t matter much what happens in between. >> >> Really stretches out the ol’ voltseconds. > > How does that increase volt-seconds? > > It's just a single component replacement of the reverse biased gate discharge speed-up transistor technique. PNP used on NFET. > >> >> Cheers >> >> Phil Hobbs >> >> -- >> Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / >> Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog ElectronicsI suppose it doesn't really increase volt-seconds asmuch as allow a lower v-s rated transformer to be used. Between the initial turn-on and the turn-off the main transistor gate is held up by its own (or the added) capacitance so it doesn't matter if the transformer induced secondary voltage collapses. piglet
Reply by ●November 10, 20232023-11-10
On Fri, 10 Nov 2023 11:01:55 -0800 (PST), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>fredag den 10. november 2023 kl. 19.27.19 UTC+1 skrev john larkin: >> On Fri, 10 Nov 2023 16:24:00 -0000 (UTC), Phil Hobbs >> <pcdhSpamM...@electrooptical.net> wrote: >> >> >John Larkin <j...@997PotHill.com> wrote: >> >> On Fri, 10 Nov 2023 08:28:15 -0500, legg <le...@nospam.magma.ca> wrote: >> >> >> >>> On Thu, 9 Nov 2023 15:14:53 -0800 (PST), Klaus Kragelund >> >>> <klaus.k...@gmail.com> wrote: >> >>> >> >>>> Hi >> >>>> >> >>>> I am on the lookout for a cheap 1:1 pulse transformer. Will be using it >> >>>> to drive a MOSFET based Solid State Switch. >> >>>> >> >>>> I know Larkin has used the DRQ127 >> >>>> >> >>>> https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 >> >>>> >> >>>> But, I am looking to see if I can find bottom dollar. >> >>>> >> >>>> I probably wont go to LCSC, so would prefer a known brand. >> >>>> >> >>>> Anyone got a recommendation? >> >>>> >> >>>> Cheers >> >>>> >> >>>> Klaus >> >>> >> >>> Suggest you nail down your requirements first: >> >>> Lpmin >> >>> Vtmin, >> >>> Rdcmax, >> >>> Isolation class, >> >>> prod test level. >> >>> >> >>> Many techniques avoid the requirement of high Lp and Vt. >> >>> >> >>> Be smart or pay. >> >>> >> >>> RL >> >> >> >> Volt-second saturation will exclude small parts that othewise look >> >> good. Ditto leakage inductance. >> >> >> >> Winding capacitance, too. There are cases where I would love to drive >> >> a fet through a transformer, but nothing reasonable works. >> >> >> >> >> > >> >There�s the common-gate FET trick, where you use a small extra FET, with >> >its source connected to the transformer and its gate and drain to the main >> >FET�s source and gate, respectively, with a small storage cap. >> > >> >(The other end of the transformer goes to the main FET�s source as usual. ) >> > >> >Using NFETs, a positive edge conducts via the body diode, turning the main >> >FET on, and a negative one conducts via transistor action, turning it off. >> >It doesn�t matter much what happens in between. >> > >> >Really stretches out the ol� voltseconds. >> > >> >Cheers >> > >> >Phil Hobbs >> Clever. >> >> Given a floating power supply, a dc/dc converter or equivalent, the >> small tranny can drive a gate driver chip. The tranny can also conduct >> tiny spikes at the leading and trailing edge of the pulse, and drive a >> highside flop or schmitt. > >so basically an analogdevices iCoupler >Eventually most every clever circuit design gets pre-empted by some cheap nasty little IC. So we need to keep inventing ever-goofier circuits. I can do that.
Reply by ●November 10, 20232023-11-10
On Fri, 10 Nov 2023 11:22:55 -0800 (PST), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:>On Friday, November 10, 2023 at 1:27:19?PM UTC-5, john larkin wrote: >> On Fri, 10 Nov 2023 16:24:00 -0000 (UTC), Phil Hobbs >> <pcdhSpamM...@electrooptical.net> wrote: >> >> >John Larkin <j...@997PotHill.com> wrote: >> >> On Fri, 10 Nov 2023 08:28:15 -0500, legg <le...@nospam.magma.ca> wrote: >> >> >> >>> On Thu, 9 Nov 2023 15:14:53 -0800 (PST), Klaus Kragelund >> >>> <klaus.k...@gmail.com> wrote: >> >>> >> >>>> Hi >> >>>> >> >>>> I am on the lookout for a cheap 1:1 pulse transformer. Will be using it >> >>>> to drive a MOSFET based Solid State Switch. >> >>>> >> >>>> I know Larkin has used the DRQ127 >> >>>> >> >>>> https://www.digikey.dk/en/products/detail/eaton-electronics-division/DRQ127-1R5-R/667262 >> >>>> >> >>>> But, I am looking to see if I can find bottom dollar. >> >>>> >> >>>> I probably wont go to LCSC, so would prefer a known brand. >> >>>> >> >>>> Anyone got a recommendation? >> >>>> >> >>>> Cheers >> >>>> >> >>>> Klaus >> >>> >> >>> Suggest you nail down your requirements first: >> >>> Lpmin >> >>> Vtmin, >> >>> Rdcmax, >> >>> Isolation class, >> >>> prod test level. >> >>> >> >>> Many techniques avoid the requirement of high Lp and Vt. >> >>> >> >>> Be smart or pay. >> >>> >> >>> RL >> >> >> >> Volt-second saturation will exclude small parts that othewise look >> >> good. Ditto leakage inductance. >> >> >> >> Winding capacitance, too. There are cases where I would love to drive >> >> a fet through a transformer, but nothing reasonable works. >> >> >> >> >> > >> >There�s the common-gate FET trick, where you use a small extra FET, with >> >its source connected to the transformer and its gate and drain to the main >> >FET�s source and gate, respectively, with a small storage cap. >> > >> >(The other end of the transformer goes to the main FET�s source as usual. ) >> > >> >Using NFETs, a positive edge conducts via the body diode, turning the main >> >FET on, and a negative one conducts via transistor action, turning it off. >> >It doesn�t matter much what happens in between. >> > >> >Really stretches out the ol� voltseconds. >> > >> >Cheers >> > >> >Phil Hobbs >> Clever. >> >> Given a floating power supply, a dc/dc converter or equivalent, the >> small tranny can drive a gate driver chip. The tranny can also conduct >> tiny spikes at the leading and trailing edge of the pulse, and drive a >> highside flop or schmitt. >> >> In my youth, I invented the dual optocoupler totem pole fet gate >> driver. That needs a floating power supply, a dc/dc or a PV coupler or >> a bootstrap supply or something. Slow but nice. >> >> Nowadays a fast logic coupler can drive a fast gate driver chip. > >If the application is for a MOSFET analog switch, switching speed is not of the essence, duty is very low.May as well buy an SSR.
