On Sun, 26 Jul 2020 07:45:29 -0700, jlarkin@highlandsniptechnology.com wrote: <snip>>>>The dual diode thing on the grounded side makes it feed back on the >>>primary peak-to-peak voltage, which tracks the secondary, which also >>>rectifies peak-to-peak. >> >>The transformer, tied to the positive rail, already supplies half >>of the pk-pk being sensed, without the need (or interference of) >>the CD parts in question. > >Not necessarily half. The positive flyback voltage depends on the >load. Sensing p-p for feedback forces the p-p to be constant.By half, I meant the input voltage ( 'forward' ) share of the sensed voltage.> >>> >>>The LTC3803 is a peak current limiter, so the startup current is >>>pretty much always the same, regardless of topology. > > >>The fet current waveform, is a combination of the series Llk/Cout >>(reflected) and the primary mag current. The former portion of >>that peaks early and is resonant. Though the chip may have a >>spike suppressor on it's sense pin (a delay), it can't regulate >>on a waveform with current that varies early in this manner. > >It regulates on the voltage feedback it sees.Chaotically, and not necessarily safely, if at all possible, when a silly nodal waveform appears within the regulation loop.> > >> >>> >>>Interestingly, at current limit in the flyback topology, it is pretty >>>much constant power vs voltage. That can be useful. >> >>It's one of the basic features (and hazards) of a flyback - the output >>current being uncontrolled when shorted. In your case, this current >>will be capacitively limited by the output structure - but may involve >>output (or at least output cap) polarity reversal. >>> >>>> >>>>It's not a forward converter without an energy storage element - >>>>it's just a switched capacitor DC-DC. >>> >>>That's just terminology. I call the non-flyback side a forward >>>converter, because fet turn-on drives the load with no specific energy >>>storage. >> >>When you use 'terminology', you should stick to definitions of the >>terms, which DO exist. We know what you mean, but you should stick >>to simple switch-on and switch-off terms to describe the operating >>periods. > >Yes sir. Please don't punish me much. > >> >>> >>>I think of "switched capacitor" as something else, an actual switched >>>capacitor. >> >>Your 'forward' operation is basic switched capacitor with (ideally) >>a 'DC transformer' separating the elements. > >Which cap is being switched? >Input (cap) and C1.>> >>It is a switch shorting two voltage sources, something usually >>tolerable only at very low power levels, where efficiencies below 50% >>can be ignored. > >Efficiency can be almost 100% once everything gets to steady-state. >It's low during startup.There's a TI chip that regulates a switched cap. You should check out it's efficiency plots. TPS60121. Switched cap light load efficiency usually depends on reduced frequency ie no load / no loss. I stuck an old switched cap clamp sim, late, into the download. This shows the commonly used pfet transposition to common drive gnd, with common gate drive voltage offset. RL
FudFly converter
Started by ●July 25, 2020
Reply by ●July 26, 20202020-07-26
Reply by ●July 26, 20202020-07-26
On Sun, 26 Jul 2020 08:51:49 -0700 (PDT), Klaus Kragelund <klauskvik@hotmail.com> wrote:>On Sunday, July 26, 2020 at 4:45:35 PM UTC+2, jla...@highlandsniptechnology.com wrote: >> On Sun, 26 Jul 2020 10:29:52 -0400, legg <legg@nospam.magma.ca> wrote: >> >> >On Sat, 25 Jul 2020 20:07:47 -0700, jlarkin@highlandsniptechnology.com >> >wrote: >> > >> >>On Sat, 25 Jul 2020 22:49:51 -0400, legg <legg@nospam.magma.ca> wrote: >> >> >> >>>On Sat, 25 Jul 2020 14:18:53 -0700, jlarkin@highlandsniptechnology.com >> >>>wrote: >> >>> >> >>>>On Sat, 25 Jul 2020 12:10:02 -0700 (PDT), klaus.kragelund@gmail.com >> >>>>wrote: >> >>>> >> >>>>>State space is used to calculate the transfer function from converter states >> >>>> >> >>>>But what does it dictate? >> >>>> >> >>>>I'd use Spice anyhow. Real life is nonlinear. >> >>>> >> >>>>> >> >>>>>Have you ever seen a forward converter without output inductance, a cap and freewheeling diodes? >> >>>> >> >>>>Sure. Sold thousands. Of course there are output caps. >> >>>> >> >>>>Sketch what you are thinking about. >> >>>> >> >>>>> >> >>>>>Without it, it's just a DC transformer like the Royer and converts not according to a duty cycle, but rather a turns ratio >> >>>> >> >>>>The forward direction works like that. The direction that regulates is >> >>>>the flyback side. >> >>> >> >>>You don't need the first CD pair in the regulation loop. >> >>>It will simply increase fet loss at turn-on (which is >> >>>going to be pretty severe anyways). >> >> >> >>The dual diode thing on the grounded side makes it feed back on the >> >>primary peak-to-peak voltage, which tracks the secondary, which also >> >>rectifies peak-to-peak. >> > >> >The transformer, tied to the positive rail, already supplies half >> >of the pk-pk being sensed, without the need (or interference of) >> >the CD parts in question. >> >> Not necessarily half. The positive flyback voltage depends on the >> load. Sensing p-p for feedback forces the p-p to be constant. >> >> >> >> >>The LTC3803 is a peak current limiter, so the startup current is >> >>pretty much always the same, regardless of topology. >> >> >> >The fet current waveform, is a combination of the series Llk/Cout >> >(reflected) and the primary mag current. The former portion of >> >that peaks early and is resonant. Though the chip may have a >> >spike suppressor on it's sense pin (a delay), it can't regulate >> >on a waveform with current that varies early in this manner. >> >> It regulates on the voltage feedback it sees. >> >> >> > >> >> >> >>Interestingly, at current limit in the flyback topology, it is pretty >> >>much constant power vs voltage. That can be useful. >> > >> >It's one of the basic features (and hazards) of a flyback - the output >> >current being uncontrolled when shorted. In your case, this current >> >will be capacitively limited by the output structure - but may involve >> >output (or at least output cap) polarity reversal. >> >> >> >>> >> >>>It's not a forward converter without an energy storage element - >> >>>it's just a switched capacitor DC-DC. >> >> >> >>That's just terminology. I call the non-flyback side a forward >> >>converter, because fet turn-on drives the load with no specific energy >> >>storage. >> > >> >When you use 'terminology', you should stick to definitions of the >> >terms, which DO exist. We know what you mean, but you should stick >> >to simple switch-on and switch-off terms to describe the operating >> >periods. >> >> Yes sir. Please don't punish me much. >> > >Terminology is important, otherwise you cannot communicate in any sensible manor.People who can't draw schematics have to communicate circuit concepts by typing words. Lots of words. Then they can debate about what the words mean.> >> > >> >> >> >>I think of "switched capacitor" as something else, an actual switched >> >>capacitor. >> > >> >Your 'forward' operation is basic switched capacitor with (ideally) >> >a 'DC transformer' separating the elements. >> >> Which cap is being switched? >> > >The FET turns on in forward fashion, with the voltage on the secondary side determined by VDC in times turns ratio. That voltage is imposed directly on the output cap. Thus switch cap, since you have a cap on the VDC input as alwaysNow THAT is some bizarre terminology! The circuit has a switch, and it has some caps somewhere, so it's a switched-capacitor converter! Incidentally, I don't put bypass caps across my power supplies in Spice. Do you?> >> > >> >It is a switch shorting two voltage sources, something usually >> >tolerable only at very low power levels, where efficiencies below 50% >> >can be ignored. >> >> Efficiency can be almost 100% once everything gets to steady-state. >> It's low during startup. >> > >Switch cap converters with non-ideal transfer ratios are not very efficientSwitched cap converters (which this isn't one of) can approach 100% efficiency if not asked to do goofy voltage ratios. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●July 26, 20202020-07-26
On Sun, 26 Jul 2020 11:54:10 -0400, legg <legg@nospam.magma.ca> wrote:>On Sun, 26 Jul 2020 07:45:29 -0700, jlarkin@highlandsniptechnology.com >wrote: > ><snip> >>>>The dual diode thing on the grounded side makes it feed back on the >>>>primary peak-to-peak voltage, which tracks the secondary, which also >>>>rectifies peak-to-peak. >>> >>>The transformer, tied to the positive rail, already supplies half >>>of the pk-pk being sensed, without the need (or interference of) >>>the CD parts in question. >> >>Not necessarily half. The positive flyback voltage depends on the >>load. Sensing p-p for feedback forces the p-p to be constant. > >By half, I meant the input voltage ( 'forward' ) share of the >sensed voltage. > >> >>>> >>>>The LTC3803 is a peak current limiter, so the startup current is >>>>pretty much always the same, regardless of topology. >> >> >>>The fet current waveform, is a combination of the series Llk/Cout >>>(reflected) and the primary mag current. The former portion of >>>that peaks early and is resonant. Though the chip may have a >>>spike suppressor on it's sense pin (a delay), it can't regulate >>>on a waveform with current that varies early in this manner. >> >>It regulates on the voltage feedback it sees. > >Chaotically, and not necessarily safely, if at all possible, when >a silly nodal waveform appears within the regulation loop. >Silly nodal waveform? Where? I've Spiced this topology and it can be made perfectly stable. It gives decent regulation on the load side without the usual optocouplers. I'll actually build it if my customer will give me a little more info about his needs.>> >> >>> >>>> >>>>Interestingly, at current limit in the flyback topology, it is pretty >>>>much constant power vs voltage. That can be useful. >>> >>>It's one of the basic features (and hazards) of a flyback - the output >>>current being uncontrolled when shorted. In your case, this current >>>will be capacitively limited by the output structure - but may involve >>>output (or at least output cap) polarity reversal. >>>> >>>>> >>>>>It's not a forward converter without an energy storage element - >>>>>it's just a switched capacitor DC-DC. >>>> >>>>That's just terminology. I call the non-flyback side a forward >>>>converter, because fet turn-on drives the load with no specific energy >>>>storage. >>> >>>When you use 'terminology', you should stick to definitions of the >>>terms, which DO exist. We know what you mean, but you should stick >>>to simple switch-on and switch-off terms to describe the operating >>>periods. >> >>Yes sir. Please don't punish me much. >> >>> >>>> >>>>I think of "switched capacitor" as something else, an actual switched >>>>capacitor. >>> >>>Your 'forward' operation is basic switched capacitor with (ideally) >>>a 'DC transformer' separating the elements. >> >>Which cap is being switched? >> > >Input (cap) and C1.My Spice circuit has no input cap and it works fine. I have never considered power rail bypass caps as "switched". Output filters neither. But use the words that you like. I just build circuits.> >>> >>>It is a switch shorting two voltage sources, something usually >>>tolerable only at very low power levels, where efficiencies below 50% >>>can be ignored. >> >>Efficiency can be almost 100% once everything gets to steady-state. >>It's low during startup. > >There's a TI chip that regulates a switched cap. You should check out >it's efficiency plots. TPS60121. > >Switched cap light load efficiency usually depends on reduced >frequency ie no load / no loss. > >I stuck an old switched cap clamp sim, late, into the download. >This shows the commonly used pfet transposition to common drive gnd, >with common gate drive voltage offset. > >RLOf course if you have two caps at very different voltages, and slap them in parallel, energy is lost. So don't do that. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●July 26, 20202020-07-26
On Sun, 26 Jul 2020 10:45:09 -0400, legg <legg@nospam.magma.ca> wrote:>On Sat, 25 Jul 2020 20:13:07 -0700, jlarkin@highlandsniptechnology.com >wrote: > >>On Sat, 25 Jul 2020 23:08:08 -0400, legg <legg@nospam.magma.ca> wrote: >> >>>On Sat, 25 Jul 2020 14:18:53 -0700, jlarkin@highlandsniptechnology.com >>>wrote: >>> >>>>On Sat, 25 Jul 2020 12:10:02 -0700 (PDT), klaus.kragelund@gmail.com >>>>wrote: >>>> >>>>>State space is used to calculate the transfer function from converter states >>>> >>>>But what does it dictate? >>>> >>>>I'd use Spice anyhow. Real life is nonlinear. >>>> >>>>> >>>>>Have you ever seen a forward converter without output inductance, a cap and freewheeling diodes? >>>> >>>>Sure. Sold thousands. Of course there are output caps. >>>> >>>>Sketch what you are thinking about. >>>> >>>>> >>>>>Without it, it's just a DC transformer like the Royer and converts not according to a duty cycle, but rather a turns ratio >>>> >>>>The forward direction works like that. The direction that regulates is >>>>the flyback side. >>> >>>Shorting the drain capacitor and using a slow diode on the primary >>>peak clamping/regulation node could allow clamp current to be >>>included in the transformed secondary flyback delivery, through >>>the slow diode's Trr, rather than just being burnt in the clamp's >>>load. >>> >>>Active clamp circuits use a switch in that diode position and >>>the induced reverse/recovery current that it produces allows >>>potentially lower switch turn-on losses as the drain voltage >>>falls naturally - but it won't work in a discontinuos (complete >>>energy transfer) circuit, at fizxed frequency. >>> >>>If a switch is used, it can be translated to a ground-referenced >>>pmos, using the ~ same drive as the main switch (with suitable >>>negative dc offset). >>> >>>RL >> >>Got a circuit? > >http://ve3ute.ca/query/active_clamp_-_switched_snubber.zip > >I've already admitted that, at low power levels, you can get >away with murder. That doesn't mean that you should't admit to >your crime . . .How do you define "low power levels"? Nanowatts? Kilowatts?> >Getting away with it is just part of the fun, and any circuit >that can survive on parasitic components is bound to end up >cheaper ( at thr BOMaterials level, anyways) than one requiring >a purchase order and schematic entry.What are the parasitic components in my circuit? -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●July 26, 20202020-07-26
On Sunday, 26 July 2020 19:43:53 UTC+3, jla...@highlandsniptechnology.com wrote:> On Sun, 26 Jul 2020 08:51:49 -0700 (PDT), Klaus Kragelund > <klauskvik@hotmail.com> wrote: > > >On Sunday, July 26, 2020 at 4:45:35 PM UTC+2, jla...@highlandsniptechnology.com wrote: > >> On Sun, 26 Jul 2020 10:29:52 -0400, legg <legg@nospam.magma.ca> wrote: > >> > >> >On Sat, 25 Jul 2020 20:07:47 -0700, jlarkin@highlandsniptechnology.com > >> >wrote: > >> > > >> >>On Sat, 25 Jul 2020 22:49:51 -0400, legg <legg@nospam.magma.ca> wrote: > >> >> > >> >>>On Sat, 25 Jul 2020 14:18:53 -0700, jlarkin@highlandsniptechnology.com > >> >>>wrote: > >> >>> > >> >>>>On Sat, 25 Jul 2020 12:10:02 -0700 (PDT), klaus.kragelund@gmail.com > >> >>>>wrote: > >> >>>> > >> >>>>>State space is used to calculate the transfer function from converter states > >> >>>> > >> >>>>But what does it dictate? > >> >>>> > >> >>>>I'd use Spice anyhow. Real life is nonlinear. > >> >>>> > >> >>>>> > >> >>>>>Have you ever seen a forward converter without output inductance, a cap and freewheeling diodes? > >> >>>> > >> >>>>Sure. Sold thousands. Of course there are output caps. > >> >>>> > >> >>>>Sketch what you are thinking about. > >> >>>> > >> >>>>> > >> >>>>>Without it, it's just a DC transformer like the Royer and converts not according to a duty cycle, but rather a turns ratio > >> >>>> > >> >>>>The forward direction works like that. The direction that regulates is > >> >>>>the flyback side. > >> >>> > >> >>>You don't need the first CD pair in the regulation loop. > >> >>>It will simply increase fet loss at turn-on (which is > >> >>>going to be pretty severe anyways). > >> >> > >> >>The dual diode thing on the grounded side makes it feed back on the > >> >>primary peak-to-peak voltage, which tracks the secondary, which also > >> >>rectifies peak-to-peak. > >> > > >> >The transformer, tied to the positive rail, already supplies half > >> >of the pk-pk being sensed, without the need (or interference of) > >> >the CD parts in question. > >> > >> Not necessarily half. The positive flyback voltage depends on the > >> load. Sensing p-p for feedback forces the p-p to be constant. > >> > >> >> > >> >>The LTC3803 is a peak current limiter, so the startup current is > >> >>pretty much always the same, regardless of topology. > >> > >> > >> >The fet current waveform, is a combination of the series Llk/Cout > >> >(reflected) and the primary mag current. The former portion of > >> >that peaks early and is resonant. Though the chip may have a > >> >spike suppressor on it's sense pin (a delay), it can't regulate > >> >on a waveform with current that varies early in this manner. > >> > >> It regulates on the voltage feedback it sees. > >> > >> > >> > > >> >> > >> >>Interestingly, at current limit in the flyback topology, it is pretty > >> >>much constant power vs voltage. That can be useful. > >> > > >> >It's one of the basic features (and hazards) of a flyback - the output > >> >current being uncontrolled when shorted. In your case, this current > >> >will be capacitively limited by the output structure - but may involve > >> >output (or at least output cap) polarity reversal. > >> >> > >> >>> > >> >>>It's not a forward converter without an energy storage element - > >> >>>it's just a switched capacitor DC-DC. > >> >> > >> >>That's just terminology. I call the non-flyback side a forward > >> >>converter, because fet turn-on drives the load with no specific energy > >> >>storage. > >> > > >> >When you use 'terminology', you should stick to definitions of the > >> >terms, which DO exist. We know what you mean, but you should stick > >> >to simple switch-on and switch-off terms to describe the operating > >> >periods. > >> > >> Yes sir. Please don't punish me much. > >> > > > >Terminology is important, otherwise you cannot communicate in any sensible manor. > > People who can't draw schematics have to communicate circuit concepts > by typing words. Lots of words. Then they can debate about what the > words mean.I do not know where you are going with this. You used the wrong terminology> > > >> > > >> >> > >> >>I think of "switched capacitor" as something else, an actual switched > >> >>capacitor. > >> > > >> >Your 'forward' operation is basic switched capacitor with (ideally) > >> >a 'DC transformer' separating the elements. > >> > >> Which cap is being switched? > >> > > > >The FET turns on in forward fashion, with the voltage on the secondary side determined by VDC in times turns ratio. That voltage is imposed directly on the output cap. Thus switch cap, since you have a cap on the VDC input as always > > Now THAT is some bizarre terminology! The circuit has a switch, and it > has some caps somewhere, so it's a switched-capacitor converter! > > Incidentally, I don't put bypass caps across my power supplies in > Spice. Do you? >No, but I am quite confident that you do in real circuits.> > > >> > > >> >It is a switch shorting two voltage sources, something usually > >> >tolerable only at very low power levels, where efficiencies below 50% > >> >can be ignored. > >> > >> Efficiency can be almost 100% once everything gets to steady-state. > >> It's low during startup. > >> > > > >Switch cap converters with non-ideal transfer ratios are not very efficient > > Switched cap converters (which this isn't one of) can approach 100% > efficiency if not asked to do goofy voltage ratios. >That's just a rewrite of my statement above :-) Cheers Klaus
Reply by ●July 26, 20202020-07-26
On Sunday, 26 July 2020 06:07:54 UTC+3, jla...@highlandsniptechnology.com wrote:> On Sat, 25 Jul 2020 22:49:51 -0400, legg <legg@nospam.magma.ca> wrote: > > >On Sat, 25 Jul 2020 14:18:53 -0700, jlarkin@highlandsniptechnology.com > >wrote: > > > >>On Sat, 25 Jul 2020 12:10:02 -0700 (PDT), klaus.kragelund@gmail.com > >>wrote: > >> > >>>State space is used to calculate the transfer function from converter states > >> > >>But what does it dictate? > >> > >>I'd use Spice anyhow. Real life is nonlinear. > >> > >>> > >>>Have you ever seen a forward converter without output inductance, a cap and freewheeling diodes? > >> > >>Sure. Sold thousands. Of course there are output caps. > >> > >>Sketch what you are thinking about. > >> > >>> > >>>Without it, it's just a DC transformer like the Royer and converts not according to a duty cycle, but rather a turns ratio > >> > >>The forward direction works like that. The direction that regulates is > >>the flyback side. > > > >You don't need the first CD pair in the regulation loop. > >It will simply increase fet loss at turn-on (which is > >going to be pretty severe anyways). > > The dual diode thing on the grounded side makes it feed back on the > primary peak-to-peak voltage, which tracks the secondary, which also > rectifies peak-to-peak. > > The LTC3803 is a peak current limiter, so the startup current is > pretty much always the same, regardless of topology. > > Interestingly, at current limit in the flyback topology, it is pretty > much constant power vs voltage. That can be useful. > > > > >It's not a forward converter without an energy storage element - > >it's just a switched capacitor DC-DC. > > That's just terminology. I call the non-flyback side a forward > converter, because fet turn-on drives the load with no specific energy > storage. > > I think of "switched capacitor" as something else, an actual switched > capacitor. > > > > > -- > > John Larkin Highland Technology, Inc > > Science teaches us to doubt. > > Claude Bernard
Reply by ●July 26, 20202020-07-26
On Sun, 26 Jul 2020 10:11:38 -0700 (PDT), klaus.kragelund@gmail.com wrote:>On Sunday, 26 July 2020 19:43:53 UTC+3, jla...@highlandsniptechnology.com wrote: >> On Sun, 26 Jul 2020 08:51:49 -0700 (PDT), Klaus Kragelund >> <klauskvik@hotmail.com> wrote: >> >> >On Sunday, July 26, 2020 at 4:45:35 PM UTC+2, jla...@highlandsniptechnology.com wrote: >> >> On Sun, 26 Jul 2020 10:29:52 -0400, legg <legg@nospam.magma.ca> wrote: >> >> >> >> >On Sat, 25 Jul 2020 20:07:47 -0700, jlarkin@highlandsniptechnology.com >> >> >wrote: >> >> > >> >> >>On Sat, 25 Jul 2020 22:49:51 -0400, legg <legg@nospam.magma.ca> wrote: >> >> >> >> >> >>>On Sat, 25 Jul 2020 14:18:53 -0700, jlarkin@highlandsniptechnology.com >> >> >>>wrote: >> >> >>> >> >> >>>>On Sat, 25 Jul 2020 12:10:02 -0700 (PDT), klaus.kragelund@gmail.com >> >> >>>>wrote: >> >> >>>> >> >> >>>>>State space is used to calculate the transfer function from converter states >> >> >>>> >> >> >>>>But what does it dictate? >> >> >>>> >> >> >>>>I'd use Spice anyhow. Real life is nonlinear. >> >> >>>> >> >> >>>>> >> >> >>>>>Have you ever seen a forward converter without output inductance, a cap and freewheeling diodes? >> >> >>>> >> >> >>>>Sure. Sold thousands. Of course there are output caps. >> >> >>>> >> >> >>>>Sketch what you are thinking about. >> >> >>>> >> >> >>>>> >> >> >>>>>Without it, it's just a DC transformer like the Royer and converts not according to a duty cycle, but rather a turns ratio >> >> >>>> >> >> >>>>The forward direction works like that. The direction that regulates is >> >> >>>>the flyback side. >> >> >>> >> >> >>>You don't need the first CD pair in the regulation loop. >> >> >>>It will simply increase fet loss at turn-on (which is >> >> >>>going to be pretty severe anyways). >> >> >> >> >> >>The dual diode thing on the grounded side makes it feed back on the >> >> >>primary peak-to-peak voltage, which tracks the secondary, which also >> >> >>rectifies peak-to-peak. >> >> > >> >> >The transformer, tied to the positive rail, already supplies half >> >> >of the pk-pk being sensed, without the need (or interference of) >> >> >the CD parts in question. >> >> >> >> Not necessarily half. The positive flyback voltage depends on the >> >> load. Sensing p-p for feedback forces the p-p to be constant. >> >> >> >> >> >> >> >>The LTC3803 is a peak current limiter, so the startup current is >> >> >>pretty much always the same, regardless of topology. >> >> >> >> >> >> >The fet current waveform, is a combination of the series Llk/Cout >> >> >(reflected) and the primary mag current. The former portion of >> >> >that peaks early and is resonant. Though the chip may have a >> >> >spike suppressor on it's sense pin (a delay), it can't regulate >> >> >on a waveform with current that varies early in this manner. >> >> >> >> It regulates on the voltage feedback it sees. >> >> >> >> >> >> > >> >> >> >> >> >>Interestingly, at current limit in the flyback topology, it is pretty >> >> >>much constant power vs voltage. That can be useful. >> >> > >> >> >It's one of the basic features (and hazards) of a flyback - the output >> >> >current being uncontrolled when shorted. In your case, this current >> >> >will be capacitively limited by the output structure - but may involve >> >> >output (or at least output cap) polarity reversal. >> >> >> >> >> >>> >> >> >>>It's not a forward converter without an energy storage element - >> >> >>>it's just a switched capacitor DC-DC. >> >> >> >> >> >>That's just terminology. I call the non-flyback side a forward >> >> >>converter, because fet turn-on drives the load with no specific energy >> >> >>storage. >> >> > >> >> >When you use 'terminology', you should stick to definitions of the >> >> >terms, which DO exist. We know what you mean, but you should stick >> >> >to simple switch-on and switch-off terms to describe the operating >> >> >periods. >> >> >> >> Yes sir. Please don't punish me much. >> >> >> > >> >Terminology is important, otherwise you cannot communicate in any sensible manor. >> >> People who can't draw schematics have to communicate circuit concepts >> by typing words. Lots of words. Then they can debate about what the >> words mean. >I do not know where you are going with this. You used the wrong terminologySez you. I drew a schematic that was unambiguous. And a bunch of people here want to argue about words. My circuits don't give a damn what you call them. Can't people draw any more? -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●July 26, 20202020-07-26
On Sun, 26 Jul 2020 09:57:25 -0700, jlarkin@highlandsniptechnology.com wrote:>On Sun, 26 Jul 2020 10:45:09 -0400, legg <legg@nospam.magma.ca> wrote: > >>On Sat, 25 Jul 2020 20:13:07 -0700, jlarkin@highlandsniptechnology.com >>wrote: >> >>>On Sat, 25 Jul 2020 23:08:08 -0400, legg <legg@nospam.magma.ca> wrote: >>> >>>>On Sat, 25 Jul 2020 14:18:53 -0700, jlarkin@highlandsniptechnology.com >>>>wrote: >>>> >>>>>On Sat, 25 Jul 2020 12:10:02 -0700 (PDT), klaus.kragelund@gmail.com >>>>>wrote: >>>>> >>>>>>State space is used to calculate the transfer function from converter states >>>>> >>>>>But what does it dictate? >>>>> >>>>>I'd use Spice anyhow. Real life is nonlinear. >>>>> >>>>>> >>>>>>Have you ever seen a forward converter without output inductance, a cap and freewheeling diodes? >>>>> >>>>>Sure. Sold thousands. Of course there are output caps. >>>>> >>>>>Sketch what you are thinking about. >>>>> >>>>>> >>>>>>Without it, it's just a DC transformer like the Royer and converts not according to a duty cycle, but rather a turns ratio >>>>> >>>>>The forward direction works like that. The direction that regulates is >>>>>the flyback side. >>>> >>>>Shorting the drain capacitor and using a slow diode on the primary >>>>peak clamping/regulation node could allow clamp current to be >>>>included in the transformed secondary flyback delivery, through >>>>the slow diode's Trr, rather than just being burnt in the clamp's >>>>load. >>>> >>>>Active clamp circuits use a switch in that diode position and >>>>the induced reverse/recovery current that it produces allows >>>>potentially lower switch turn-on losses as the drain voltage >>>>falls naturally - but it won't work in a discontinuos (complete >>>>energy transfer) circuit, at fizxed frequency. >>>> >>>>If a switch is used, it can be translated to a ground-referenced >>>>pmos, using the ~ same drive as the main switch (with suitable >>>>negative dc offset). >>>> >>>>RL >>> >>>Got a circuit? >> >>http://ve3ute.ca/query/active_clamp_-_switched_snubber.zip >> >>I've already admitted that, at low power levels, you can get >>away with murder. That doesn't mean that you should't admit to >>your crime . . . > >How do you define "low power levels"? Nanowatts? Kilowatts? > >> >>Getting away with it is just part of the fun, and any circuit >>that can survive on parasitic components is bound to end up >>cheaper ( at thr BOMaterials level, anyways) than one requiring >>a purchase order and schematic entry. > >What are the parasitic components in my circuit?Zin, Llk are the main ones, but it's hard to tell without an actual model or measured waveforms from which they can be enumerated or derived. Doodling on a pad isn't building circuits, so there's a limit to how they can be evaluated. I doubt very much, for a start, that the chip can be induced to produce the illustrated pulse-widths, except under very specific external conditions - something that nature is very lax in ensuring. I'm not going to flog topology or applications on newsnet - I learned some years ago that there was little profit or satisfaction in doing so. Have fun. RL
Reply by ●July 26, 20202020-07-26
"Piotr Wyderski" <peter.pan@neverland.mil> wrote in message news:rfj9v9$1hauu$1@portraits.wsisiz.edu.pl...> The lack of the inductor is a regular implementation at low power, e.g. > see the SN6501. For lower ripple level is commonly being implemented as > two interleaved forwards, i.e. the push-pull. :-)Yes, at low power you don't care about crap efficiency and the current can be limited by relatively high Rds(on) or hFE-limited transistors. Here's another example of that: https://www.seventransistorlabs.com/Images/Deadbug_Sch.png I know the PP drivers as MAX253, same thing more or less. I recall a bunch of ADuM isolator parts having PP drivers in them, though I think they're actually current mode and suggest^H^Hrequire output filter inductors?> Just to note: there *is* a topology called flyback-forward.Hmm, I get very few search results. One patent that's some sort of quasi-resonant C-clamped-flyback hybrid. It seems obscure enough that I wouldn't feel bad creating yet another definition for it... Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
Reply by ●July 26, 20202020-07-26
On Sun, 26 Jul 2020 13:45:14 -0500, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>"Piotr Wyderski" <peter.pan@neverland.mil> wrote in message >news:rfj9v9$1hauu$1@portraits.wsisiz.edu.pl... >> The lack of the inductor is a regular implementation at low power, e.g. >> see the SN6501. For lower ripple level is commonly being implemented as >> two interleaved forwards, i.e. the push-pull. :-) > >Yes, at low power you don't care about crap efficiency and the current can >be limited by relatively high Rds(on) or hFE-limited transistors. >Here's another example of that: >https://www.seventransistorlabs.com/Images/Deadbug_Sch.png >I call that an autotransformer flyback. I usually use the DRQ127-type dual inductors and as much voltage multiplier as needed. It's not inherently inefficient. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
