On Friday, 10 November 2023 at 20:23:02 UTC+1, Fred Bloggs 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.It needs to switch fast, since transient loss might be very large, and exceed transient thermal resistance constraints
Cheap pulse 1:1 transformer
Started by ●November 9, 2023
Reply by ●November 11, 20232023-11-11
Reply by ●November 11, 20232023-11-11
On Saturday, 11 November 2023 at 17:00:41 UTC+1, legg wrote:> On Fri, 10 Nov 2023 07:22:13 -0800, 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. > ISDN tfx for POE are a good example of what will or will not work. > > I had to test a bunch for temperature rise/Lp when passing > POE current levels. The spec isn't often clear. > > For technique: > > - there are a lot of pulse width extension/termination > methods that use the pulse transformer to pass info, not > necessarily power. > > - Small transformers can also pass gate power at higher frequencies > than the PWM fundamental. Pwm is conveyed through a modulation > method. >That was my first try: https://www.electronicsdesign.dk/tmp/ssr_xfm_only.pdf It needed addition of a comparator to speed up the gatedrive and UVLO circuit to avoid brown-outs. The other link I posted is a lot easier to use. Could just grap one of those Digital icouplers with power supply. VERY expensive. https://www.analog.com/media/en/technical-documentation/data-sheets/ADM3251E.pdf
Reply by ●November 11, 20232023-11-11
On Saturday, 11 November 2023 at 16:31:57 UTC+1, John Larkin wrote:> On Sat, 11 Nov 2023 04:00:11 -0800 (PST), Fred Bloggs > <bloggs.fred...@gmail.com> wrote: > >On Friday, November 10, 2023 at 9:46:16?PM UTC-5, John Larkin wrote: > >> On Fri, 10 Nov 2023 16:27:25 -0800 (PST), Fred Bloggs > >> <bloggs.fred...@gmail.com> wrote: > >> >On Friday, November 10, 2023 at 3:10:07?PM UTC-5, john larkin wrote: > >> >> On Fri, 10 Nov 2023 11:22:55 -0800 (PST), Fred Bloggs > >> >> <bloggs.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. > >> > > >> >Sounds like it's not quite the same as a pulsed drive. The switch is turned on and stays on indefinitely etc...you can't do that with an ac pulsed drive. > >> Some of the bidirectional LED-mosfet SSRs have zero offset, a few ohms > >> Ron, and picoamp leakage. 1 mA drive is usually plenty. > >> > >> Switching times are in the ballpark of 1 ms. > > > >Most be using those PV gate drives... Conceptualizing the electronics is relatively simple, the hard part is armor plating it against the real world, the mains are really harsh. Then if the transient protection overreacts in the wrong way, you can trigger a trip on the smart circuit protection technology these days. Things like nuisance tripping, death by transient, smoke or other odd odors, are not good public relations. > > > >https://www.emc-directory.com/community/what-is-a-power-line-transient > The CPC1540GS is claimed to be self-protecting, and it is to maybe 40 > volts. It's about 25 ohms on and leaks picoamps off. It makes a nice > signal switch or mux. > > It was an Ixys part but seems to be made now by someone else, so may > not be a good choice for new designs. The basic idea, a > current-limiting thermal-limiting SSR, is great.Very nice part https://www.mouser.dk/datasheet/2/240/media-3320675.pdf But insane price, I can buy 10 Cortex M microcontrollers for that price, if that reference feels any good ;-)
Reply by ●November 11, 20232023-11-11
Klaus Kragelund <klaus.kragelund@gmail.com> wrote:> On Friday, 10 November 2023 at 17:24:08 UTC+1, 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. >> > Sounds very interesting. Do you have a link to a schematics? >I did it for a customer gig a couple of years ago, but they went away before it got built. (It was a large semiconductor equipment company.) Sometimes folks paint themselves into a corner, and then look around for help. We’re fine with that as long as they stop painting while we get on with the job. ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Reply by ●November 11, 20232023-11-11
On Sat, 11 Nov 2023 23:39:57 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>Klaus Kragelund <klaus.kragelund@gmail.com> wrote: >> On Friday, 10 November 2023 at 17:24:08 UTC+1, 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. >>> >> Sounds very interesting. Do you have a link to a schematics? >> > >I did it for a customer gig a couple of years ago, but they went away >before it got built. >(It was a large semiconductor equipment company.)Knowing the semi business in general, they probably stole the idea and did it themselves.
Reply by ●November 11, 20232023-11-11
søndag den 12. november 2023 kl. 00.40.06 UTC+1 skrev Phil Hobbs:> Klaus Kragelund <klaus.k...@gmail.com> wrote: > > On Friday, 10 November 2023 at 17:24:08 UTC+1, 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. > >> > > Sounds very interesting. Do you have a link to a schematics? > > > I did it for a customer gig a couple of years ago, but they went away > before it got built. > (It was a large semiconductor equipment company.) >this one from the old "Philips Power semiconductor applications" https://imgur.com/a/E3DaFAO ?
Reply by ●November 11, 20232023-11-11
Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:> søndag den 12. november 2023 kl. 00.40.06 UTC+1 skrev Phil Hobbs: >> Klaus Kragelund <klaus.k...@gmail.com> wrote: >>> On Friday, 10 November 2023 at 17:24:08 UTC+1, 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. >>>> >>> Sounds very interesting. Do you have a link to a schematics? >>> >> I did it for a customer gig a couple of years ago, but they went away >> before it got built. >> (It was a large semiconductor equipment company.) >> > > this one from the old "Philips Power semiconductor applications" > > https://imgur.com/a/E3DaFAO ? > > >Pretty much. I was fairly sure that I wasn’t the first one to do it, but it was new to me. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Reply by ●November 11, 20232023-11-11
On Sat, 11 Nov 2023 14:57:11 -0800 (PST), Klaus Kragelund <klaus.kragelund@gmail.com> wrote:>On Friday, 10 November 2023 at 16:28:14 UTC+1, John Larkin 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 >> Are you driving the gate of a fet? What fet? > >STB43N60DM2 > >I did a change to the design, since the 1:10 transformer was bugging me, so used a old fashion CD4093 from 15V supply, to make an isolated supply with a 1:1 transformer. > >Then an opto to contol the MOSFETs. Emitter followers to lower the impedance driving the gate, since the turn on/turn off losses needs to be kept low due to transient thermal resistance. > >Schematics, first draft: > >www.electronicsdesign.dk/tmp/ssr.pdf > >Some comments: > >UVLO is handled by the microcontroller in that the PSU starts when power is applied, but the microcontroller is not allowed to turn the FET on until we are sure the PSU is active (milliseconds). Likewise, during shutdown the microcontroller first disables the opto. > >We need to have UVLO detection on the 15V power supply for the self-running oscillator, in case of a brown-out � lower voltage of the 15V node, the opto needs to be turned off before voltage sags deeper. Normally, if power is lost, then the switch off loss is also zero, but we could have a situation with low mains voltage and we need to take actions accordingly. > >MOSFET selected is STB43N60DM2, 100mohm/D2PAK, about 40K/W with current layout. >At 100mohm/3.7A, loss is 1.3W. 600V device to have 60% derating from peak of 360V. > >275V varistor SIOV1 is placed across drain/drain of MOSFETs. We might be able to use lower voltage rated MOSFETs due to thje varistor. >MOSFETs are avalanche rated for 800mJ. > >K = 0.015 for less than 10us switching time. Estimated for 1us.. >Rth = 40K/W. Transient Rth = 0.6K/WSince you have that 230 VAC source, you could make a gate power supply from that. The little capacitor-limited thing like people use to power LEDs from the AC line. Then use my should-be-famous totem-pole optocoupler, which has zero static supply current. Why two fets? Change the heater and run half-wave. How about an opto-triac? The whole thing becomes two parts.
Reply by ●November 12, 20232023-11-12
On Friday, November 10, 2023 at 12:09:11 PM UTC-8, john larkin wrote:> Eventually most every clever circuit design gets pre-empted by some > cheap nasty little IC.Not really; clever design often means multiple parts, and multipart designs do get integrated... thus when circuits are clever multipart designs, and get integrated, that creates, by definition, an IC. The cheap and nasty characterizations can be painted over anything. Your socks, for instance.> So we need to keep inventing ever-goofier circuits. I can do that.Thus: <https://rockemsocks.com/products/goofy-split-face>
Reply by ●November 12, 20232023-11-12
On 11/11/2023 11:05 pm, Klaus Kragelund wrote:> On Friday, 10 November 2023 at 20:23:02 UTC+1, Fred Bloggs 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. > It needs to switch fast, since transient loss might be very large, and exceed transient thermal resistance constraintsWhy do you need to switch a heater fast? Those are fancy fets just for heater switching, triacs make better use of silicon? piglet
