On Sunday, 12 November 2023 at 00:52:21 UTC+1, Lasse Langwadt Christensen 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 ?Great find ;-)
Cheap pulse 1:1 transformer
Started by ●November 9, 2023
Reply by ●November 12, 20232023-11-12
Reply by ●November 12, 20232023-11-12
On Sunday, 12 November 2023 at 01:02:21 UTC+1, John Larkin wrote:> On Sat, 11 Nov 2023 14:57:11 -0800 (PST), Klaus Kragelund > <klaus.k...@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/W > Since 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.Opto triac was how we started. But that has a nasty turn off and on at the zero crossing due to the holding current and diac trigger voltage, and that pops up as differential noise in the conducted emission measurements. 20dB over the limits. So I made a triac design that turned it on during all the time, that solved the emission problem. But a funny spurious triggering has popped up, we are solving that, but will populate the PCB with the MOSFET solution as a backup solution
Reply by ●November 12, 20232023-11-12
On Sunday, 12 November 2023 at 11:55:48 UTC+1, piglet wrote:> 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 constraints > Why do you need to switch a heater fast? Those are fancy fets just for > heater switching, triacs make better use of silicon? >Due to the switching loss of the FET. I am looking into heavy snubber to avoid that.
Reply by ●November 12, 20232023-11-12
On Sunday, 12 November 2023 at 01:02:21 UTC+1, John Larkin wrote:> On Sat, 11 Nov 2023 14:57:11 -0800 (PST), Klaus Kragelund > <klaus.k...@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/W > Since 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. >Yes, could be an good idea. Will try that> Then use my should-be-famous totem-pole optocoupler, which has zero > static supply current.Will look it up...> > Why two fets? Change the heater and run half-wave. >We need full power, so can't do that.> How about an opto-triac? The whole thing becomes two parts.That was what we did in earlier design
Reply by ●November 12, 20232023-11-12
On Sunday, 12 November 2023 at 01:02:21 UTC+1, John Larkin wrote:> On Sat, 11 Nov 2023 14:57:11 -0800 (PST), Klaus Kragelund > <klaus.k...@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/W > Since 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. >Actually the capacitive couplers are not very good when it comes to surges/transients on the mains line, so need to add impedance to reduce peak currents in the circuit.
Reply by ●November 12, 20232023-11-12
On 12/11/2023 11:19 am, Klaus Kragelund wrote:> On Sunday, 12 November 2023 at 11:55:48 UTC+1, piglet wrote: >> 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 constraints >> Why do you need to switch a heater fast? Those are fancy fets just for >> heater switching, triacs make better use of silicon? >> > Due to the switching loss of the FET. I am looking into heavy snubber to avoid that.Surprised you find it worthwhile, I estimate you'll see 2.2W in the two FETs versus 2.9W in a triac - which costs less and frees up PCB area you could use instead for heatsinking? piglet
Reply by ●November 12, 20232023-11-12
On Sunday, 12 November 2023 at 13:08:31 UTC+1, piglet wrote:> On 12/11/2023 11:19 am, Klaus Kragelund wrote: > > On Sunday, 12 November 2023 at 11:55:48 UTC+1, piglet wrote: > >> 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 constraints > >> Why do you need to switch a heater fast? Those are fancy fets just for > >> heater switching, triacs make better use of silicon? > >> > > Due to the switching loss of the FET. I am looking into heavy snubber to avoid that. > Surprised you find it worthwhile, I estimate you'll see 2.2W in the two > FETs versus 2.9W in a triac - which costs less and frees up PCB area you > could use instead for heatsinking? >Yes, it's only a backup solution if the current solution with the triac misbehaves. Triac costs 1 USD, FETs 5 USD combined. At lower power levels it switches, so FETs are cheaper than triac. Advantage of FETs are also no spurious turn on and other funny 4th quadrant switching problems.
Reply by ●November 12, 20232023-11-12
On Sun, 12 Nov 2023 03:29:02 -0800 (PST), Klaus Kragelund <klaus.kragelund@gmail.com> wrote:>On Sunday, 12 November 2023 at 01:02:21 UTC+1, John Larkin wrote: >> On Sat, 11 Nov 2023 14:57:11 -0800 (PST), Klaus Kragelund >> <klaus.k...@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/W >> Since 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. >> >Actually the capacitive couplers are not very good when it comes to surges/transients on the mains line, so need to add impedance to reduce peak currents in the circuit.Sure, the LED night-light circuits include a series resistor. The totem-pole opto gate driver needs about zero supply current, so the series resistor can be big. Actually, the series resistor would work without a series cap. I can sketch it if it's not all clear. After this coffee diffuses into my brain.
Reply by ●November 12, 20232023-11-12
On Sun, 12 Nov 2023 07:44:41 -0800, John Larkin <jl@997PotHill.com> wrote:>On Sun, 12 Nov 2023 03:29:02 -0800 (PST), Klaus Kragelund ><klaus.kragelund@gmail.com> wrote: > >>On Sunday, 12 November 2023 at 01:02:21 UTC+1, John Larkin wrote: >>> On Sat, 11 Nov 2023 14:57:11 -0800 (PST), Klaus Kragelund >>> <klaus.k...@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/W >>> Since 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. >>> >>Actually the capacitive couplers are not very good when it comes to surges/transients on the mains line, so need to add impedance to reduce peak currents in the circuit. > >Sure, the LED night-light circuits include a series resistor. > >The totem-pole opto gate driver needs about zero supply current, so >the series resistor can be big. Actually, the series resistor would >work without a series cap. I can sketch it if it's not all clear. >After this coffee diffuses into my brain. > >You could do your entire isolated gate driver for about 17 cents.
Reply by ●November 12, 20232023-11-12
søndag den 12. november 2023 kl. 18.15.35 UTC+1 skrev John Larkin:> On Sun, 12 Nov 2023 07:44:41 -0800, John Larkin <j...@997PotHill.com> > wrote: > >On Sun, 12 Nov 2023 03:29:02 -0800 (PST), Klaus Kragelund > ><klaus.k...@gmail.com> wrote: > > > >>On Sunday, 12 November 2023 at 01:02:21 UTC+1, John Larkin wrote: > >>> On Sat, 11 Nov 2023 14:57:11 -0800 (PST), Klaus Kragelund > >>> <klaus.k...@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/W > >>> Since 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. > >>> > >>Actually the capacitive couplers are not very good when it comes to surges/transients on the mains line, so need to add impedance to reduce peak currents in the circuit. > > > >Sure, the LED night-light circuits include a series resistor. > > > >The totem-pole opto gate driver needs about zero supply current, so > >the series resistor can be big. Actually, the series resistor would > >work without a series cap. I can sketch it if it's not all clear. > >After this coffee diffuses into my brain. > > > > > You could do your entire isolated gate driver for about 17 cents.something like this? Version 4 SHEET 1 960 800 WIRE 64 -112 -64 -112 WIRE 272 -112 144 -112 WIRE 688 -112 272 -112 WIRE 272 -64 272 -112 WIRE -64 0 -64 -112 WIRE 688 64 688 -112 WIRE 272 96 272 16 WIRE -64 112 -64 64 WIRE -64 112 -160 112 WIRE 80 112 -64 112 WIRE -160 144 -160 112 WIRE -64 144 -64 112 WIRE 224 176 144 176 WIRE -64 208 -160 208 WIRE 176 208 -64 208 WIRE 272 208 272 192 WIRE 272 208 176 208 WIRE 272 224 272 208 WIRE 224 240 224 176 WIRE 272 384 272 320 WIRE 688 384 688 144 WIRE 688 384 272 384 WIRE -144 432 -560 432 WIRE 80 432 80 112 WIRE 80 432 48 432 WIRE 80 496 48 496 WIRE -304 528 -336 528 WIRE -144 528 -224 528 WIRE 80 576 80 496 WIRE 144 576 144 176 WIRE 144 576 80 576 WIRE -336 624 -336 528 WIRE -336 624 -416 624 WIRE -304 624 -336 624 WIRE -144 624 -224 624 WIRE 80 624 80 576 WIRE 80 624 48 624 WIRE -560 640 -560 432 WIRE -416 640 -416 624 WIRE 176 688 176 208 WIRE 176 688 48 688 WIRE -416 720 -560 720 WIRE -144 720 -416 720 FLAG -560 720 0 FLAG -64 208 0 SYMBOL nmos 224 96 R0 SYMATTR InstName M1 SYMATTR Value R6020PNJ SYMBOL nmos 224 320 M180 SYMATTR InstName M2 SYMATTR Value R6020PNJ SYMBOL res 256 -80 R0 SYMATTR InstName R1 SYMATTR Value 70 SYMBOL voltage 688 48 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value SINE(0 325 50 0 0 0) SYMBOL diode -80 0 R0 SYMATTR InstName D1 SYMATTR Value MUR460 SYMBOL zener -144 208 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D2 SYMATTR Value BZX84C10L SYMATTR Description Diode SYMATTR Type diode SYMBOL res 160 -128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 500k SYMBOL cap -80 144 R0 SYMATTR InstName C1 SYMATTR Value 100n SYMBOL Optos\\4N25 -48 496 R0 SYMATTR InstName U1 SYMBOL Optos\\4N25 -48 688 R0 SYMATTR InstName U2 SYMBOL voltage -560 624 R0 WINDOW 3 -65 60 Left 2 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value 2 SYMBOL voltage -416 624 R0 WINDOW 3 -74 146 Left 2 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value PULSE(2 0 .1 1u 1u .1205 .3457) SYMBOL res -208 512 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 100 SYMBOL res -208 608 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 100 TEXT -326 -184 Left 2 !.tran 2
