Driving capacitive loads with an H bridge
in [Design]
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From: Jim Thompson on 22 Jul 2010 13:16 On Thu, 22 Jul 2010 10:02:23 +0100, "markp" <map.nospam(a)f2s.com> wrote: > >"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in >message news:8s8f469752bbc4sj6v8jhsibovhfmgg49j(a)4ax.com... >> On Wed, 21 Jul 2010 17:13:23 +0100, "markp" <map.nospam(a)f2s.com> >> wrote: >> >> [snip] >>> >>>I'm not looking for a design as such, just a possible architecture. So far >>>the info you've been given is a triangle waveform across the cap, bipolar >>>so >>>no DC component, >40V AC(true RMS), a few hundred Hertz and a question >>>whether an H-bridge architecture could do it. I'm not sure how much more >>>information you want...:) >>> >>>Mark >>> >> >> "...but it has to be efficient, i.e some kind of energy retrieval." >> >> What does that mean? Some particulars could get you some suggestions, >> vagueness will lose our interest. >> >> ...Jim Thompson > >Sorry Jim, what I meant was if you drive a triangle wave across a capacitor >then the capacitor will store energy when it's charged up, but when it is >discharged the energy has to be recovered back (retrieved) so it can be used >again in the next cycle. A parallel resonant LC circuit does just this by >shifting the stored energy from the capacitor to the inductor and back >again, so for ideal components no power is needed to sustain oscillation. An >H brigde would do it by temporarily storing energy in the inductor part and >dumping that energy back to the DC supply reservoir. But "dumping" an inductor into a capacitor gives you a sinusoid, NOT a triangle wave. You'd need some sort of idealized current splitter, or maybe one of John "The Bloviator" Larkin's non-charge conservation to do it. > >I actually thought that by stating it was to be efficient was somewhat >equivalent to that, which is why I put 'i.e. some kind of energy retrieval'. >But you're right, it could have been stated better. > >Mark. > What exactly are you trying to do? Something that can really work, or an "idealism" ?:-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Only as good as the person behind the wheel.
From: markp on 22 Jul 2010 13:42 "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in message news:mvug46p5dvvl5ku22o7uvfgnpi79f2t3v5(a)4ax.com... > On Thu, 22 Jul 2010 10:02:23 +0100, "markp" <map.nospam(a)f2s.com> > wrote: > >> >>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote >>in >>message news:8s8f469752bbc4sj6v8jhsibovhfmgg49j(a)4ax.com... >>> On Wed, 21 Jul 2010 17:13:23 +0100, "markp" <map.nospam(a)f2s.com> >>> wrote: >>> >>> [snip] >>>> >>>>I'm not looking for a design as such, just a possible architecture. So >>>>far >>>>the info you've been given is a triangle waveform across the cap, >>>>bipolar >>>>so >>>>no DC component, >40V AC(true RMS), a few hundred Hertz and a question >>>>whether an H-bridge architecture could do it. I'm not sure how much more >>>>information you want...:) >>>> >>>>Mark >>>> >>> >>> "...but it has to be efficient, i.e some kind of energy retrieval." >>> >>> What does that mean? Some particulars could get you some suggestions, >>> vagueness will lose our interest. >>> >>> ...Jim Thompson >> >>Sorry Jim, what I meant was if you drive a triangle wave across a >>capacitor >>then the capacitor will store energy when it's charged up, but when it is >>discharged the energy has to be recovered back (retrieved) so it can be >>used >>again in the next cycle. A parallel resonant LC circuit does just this by >>shifting the stored energy from the capacitor to the inductor and back >>again, so for ideal components no power is needed to sustain oscillation. >>An >>H brigde would do it by temporarily storing energy in the inductor part >>and >>dumping that energy back to the DC supply reservoir. > > But "dumping" an inductor into a capacitor gives you a sinusoid, NOT a > triangle wave. In my sentence "A parallel resonant LC circuit does just this by shifting the stored energy from the capacitor to the inductor and back again", the 'just this' bit refers to energy transfer, it was not specific to any waveform. The first sentence gave an example of a waveform that charges up a capacitor and then discharges it, as would any, including sinusoids. > > You'd need some sort of idealized current splitter, or maybe one of > John "The Bloviator" Larkin's non-charge conservation to do it. > >> >>I actually thought that by stating it was to be efficient was somewhat >>equivalent to that, which is why I put 'i.e. some kind of energy >>retrieval'. >>But you're right, it could have been stated better. >> >>Mark. >> > > What exactly are you trying to do? Something that can really work, or > an "idealism" ?:-) > > ...Jim Thompson I do have very good reasons indeed for wanting a triangle wave and at some point I'll need to make a real unit to test. However I cannot discuss the actual application, so unfortunately (however much I'd like to) I can't elaborate on it. I wish I could because I'm sure you and others may have ideas. Mark.
From: Jim Thompson on 22 Jul 2010 14:06 On Thu, 22 Jul 2010 18:42:27 +0100, "markp" <map.nospam(a)f2s.com> wrote: > >"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in >message news:mvug46p5dvvl5ku22o7uvfgnpi79f2t3v5(a)4ax.com... >> On Thu, 22 Jul 2010 10:02:23 +0100, "markp" <map.nospam(a)f2s.com> >> wrote: >> >>> >>>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote >>>in >>>message news:8s8f469752bbc4sj6v8jhsibovhfmgg49j(a)4ax.com... >>>> On Wed, 21 Jul 2010 17:13:23 +0100, "markp" <map.nospam(a)f2s.com> >>>> wrote: >>>> >>>> [snip] >>>>> >>>>>I'm not looking for a design as such, just a possible architecture. So >>>>>far >>>>>the info you've been given is a triangle waveform across the cap, >>>>>bipolar >>>>>so >>>>>no DC component, >40V AC(true RMS), a few hundred Hertz and a question >>>>>whether an H-bridge architecture could do it. I'm not sure how much more >>>>>information you want...:) >>>>> >>>>>Mark >>>>> >>>> >>>> "...but it has to be efficient, i.e some kind of energy retrieval." >>>> >>>> What does that mean? Some particulars could get you some suggestions, >>>> vagueness will lose our interest. >>>> >>>> ...Jim Thompson >>> >>>Sorry Jim, what I meant was if you drive a triangle wave across a >>>capacitor >>>then the capacitor will store energy when it's charged up, but when it is >>>discharged the energy has to be recovered back (retrieved) so it can be >>>used >>>again in the next cycle. A parallel resonant LC circuit does just this by >>>shifting the stored energy from the capacitor to the inductor and back >>>again, so for ideal components no power is needed to sustain oscillation. >>>An >>>H brigde would do it by temporarily storing energy in the inductor part >>>and >>>dumping that energy back to the DC supply reservoir. >> >> But "dumping" an inductor into a capacitor gives you a sinusoid, NOT a >> triangle wave. > >In my sentence "A parallel resonant LC circuit does just this by shifting >the stored energy from the capacitor to the inductor and back again", the >'just this' bit refers to energy transfer, it was not specific to any >waveform. The first sentence gave an example of a waveform that charges up a >capacitor and then discharges it, as would any, including sinusoids. > >> >> You'd need some sort of idealized current splitter, or maybe one of >> John "The Bloviator" Larkin's non-charge conservation to do it. >> > >>> >>>I actually thought that by stating it was to be efficient was somewhat >>>equivalent to that, which is why I put 'i.e. some kind of energy >>>retrieval'. >>>But you're right, it could have been stated better. >>> >>>Mark. >>> >> >> What exactly are you trying to do? Something that can really work, or >> an "idealism" ?:-) > >> >> ...Jim Thompson > >I do have very good reasons indeed for wanting a triangle wave and at some >point I'll need to make a real unit to test. However I cannot discuss the >actual application, so unfortunately (however much I'd like to) I can't >elaborate on it. I wish I could because I'm sure you and others may have >ideas. > >Mark. > Send me an NDA and then some real information. I'm not into guessing. I can do a Larkinesque ideal machine that will run forever, and take no energy to work ;-) (And produce a triangle wave :) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Only as good as the person behind the wheel.
From: whit3rd on 22 Jul 2010 15:26 On Jul 22, 9:07 am, "markp" <map.nos...(a)f2s.com> wrote: > "whit3rd" <whit...(a)gmail.com> wrote in message > >> I need to drive capacitor with a triangle wave...has to > >> be > >> efficient, i.e some kind of energy retrieval. > >Use a generator and flywheel; by shaping the poles of the generator, > Oh dear! Just to be clear, by energy retrieval I meant the stored energy in > the capacitor when charged needs to be recovered back when discharging Yep, that happens. The current waveform and voltage waveform into the capacitor are out-of-phase, the energy flows both ways for a net zero loss (but some stray resistances, of course, suck power).
From: Jim Thompson on 22 Jul 2010 15:38
On Thu, 22 Jul 2010 11:06:03 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >On Thu, 22 Jul 2010 18:42:27 +0100, "markp" <map.nospam(a)f2s.com> >wrote: > >> >>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in >>message news:mvug46p5dvvl5ku22o7uvfgnpi79f2t3v5(a)4ax.com... >>> On Thu, 22 Jul 2010 10:02:23 +0100, "markp" <map.nospam(a)f2s.com> >>> wrote: >>> >>>> >>>>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote >>>>in >>>>message news:8s8f469752bbc4sj6v8jhsibovhfmgg49j(a)4ax.com... >>>>> On Wed, 21 Jul 2010 17:13:23 +0100, "markp" <map.nospam(a)f2s.com> >>>>> wrote: >>>>> >>>>> [snip] >>>>>> >>>>>>I'm not looking for a design as such, just a possible architecture. So >>>>>>far >>>>>>the info you've been given is a triangle waveform across the cap, >>>>>>bipolar >>>>>>so >>>>>>no DC component, >40V AC(true RMS), a few hundred Hertz and a question >>>>>>whether an H-bridge architecture could do it. I'm not sure how much more >>>>>>information you want...:) >>>>>> >>>>>>Mark >>>>>> >>>>> >>>>> "...but it has to be efficient, i.e some kind of energy retrieval." >>>>> >>>>> What does that mean? Some particulars could get you some suggestions, >>>>> vagueness will lose our interest. >>>>> >>>>> ...Jim Thompson >>>> >>>>Sorry Jim, what I meant was if you drive a triangle wave across a >>>>capacitor >>>>then the capacitor will store energy when it's charged up, but when it is >>>>discharged the energy has to be recovered back (retrieved) so it can be >>>>used >>>>again in the next cycle. A parallel resonant LC circuit does just this by >>>>shifting the stored energy from the capacitor to the inductor and back >>>>again, so for ideal components no power is needed to sustain oscillation. >>>>An >>>>H brigde would do it by temporarily storing energy in the inductor part >>>>and >>>>dumping that energy back to the DC supply reservoir. >>> >>> But "dumping" an inductor into a capacitor gives you a sinusoid, NOT a >>> triangle wave. >> >>In my sentence "A parallel resonant LC circuit does just this by shifting >>the stored energy from the capacitor to the inductor and back again", the >>'just this' bit refers to energy transfer, it was not specific to any >>waveform. The first sentence gave an example of a waveform that charges up a >>capacitor and then discharges it, as would any, including sinusoids. >> >>> >>> You'd need some sort of idealized current splitter, or maybe one of >>> John "The Bloviator" Larkin's non-charge conservation to do it. >>> >> >>>> >>>>I actually thought that by stating it was to be efficient was somewhat >>>>equivalent to that, which is why I put 'i.e. some kind of energy >>>>retrieval'. >>>>But you're right, it could have been stated better. >>>> >>>>Mark. >>>> >>> >>> What exactly are you trying to do? Something that can really work, or >>> an "idealism" ?:-) >> >>> >>> ...Jim Thompson >> >>I do have very good reasons indeed for wanting a triangle wave and at some >>point I'll need to make a real unit to test. However I cannot discuss the >>actual application, so unfortunately (however much I'd like to) I can't >>elaborate on it. I wish I could because I'm sure you and others may have >>ideas. >> >>Mark. >> > >Send me an NDA and then some real information. > >I'm not into guessing. > >I can do a Larkinesque ideal machine that will run forever, and take >no energy to work ;-) (And produce a triangle wave :) > > ...Jim Thompson Like this... http://analog-innovations.com/SED/All_You_Need_Is_A_Perfect_Current_Mirror.pdf ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Only as good as the person behind the wheel. |