Driving capacitive loads with an H bridge
in [Design]
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From: John Fields on 22 Jul 2010 17:01 On Thu, 22 Jul 2010 18:05:46 +0100, "markp" <map.nospam(a)f2s.com> wrote: > >"John Fields" <jfields(a)austininstruments.com> wrote in message >news:vbtg46ditdftdgl5hg3i06b84oj0irdhoc(a)4ax.com... >> On Thu, 22 Jul 2010 10:02:23 +0100, "markp" <map.nospam(a)f2s.com> >> wrote: >> >> >>>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. >> >> --- >> Here's six circuits: >> >> On the top, an "H" bridge driving a capacitor, a series resonant >> circuit, and a parallel resonant circuit, and on the bottom a bipolar >> half-bridge driving the same circuits. >> >> Does it look like any of them will do what you want? >> >> JF >> > >Did you forget to include the link? --- Nope, the circuit list:-( Version 4 SHEET 1 960 680 WIRE -272 -224 -336 -224 WIRE -144 -224 -208 -224 WIRE 16 -224 0 -224 WIRE 112 -224 96 -224 WIRE 192 -224 176 -224 WIRE 384 -224 384 -320 WIRE 384 -224 336 -224 WIRE 400 -224 384 -224 WIRE 464 -224 464 -320 WIRE 528 -224 464 -224 WIRE -336 -176 -336 -224 WIRE -144 -176 -144 -224 WIRE 0 -176 0 -224 WIRE 192 -176 192 -224 WIRE 336 -176 336 -224 WIRE 528 -176 528 -224 WIRE -336 -48 -336 -96 WIRE -144 -48 -144 -96 WIRE -144 -48 -336 -48 WIRE 0 -48 0 -96 WIRE 0 -48 -144 -48 WIRE 192 -48 192 -96 WIRE 192 -48 0 -48 WIRE 336 -48 336 -96 WIRE 336 -48 192 -48 WIRE 528 -48 528 -96 WIRE 528 -48 336 -48 WIRE -336 16 -336 -48 WIRE -160 96 -336 96 WIRE 80 96 16 96 WIRE 192 96 160 96 WIRE 480 96 352 96 WIRE 544 96 480 96 WIRE -336 144 -336 96 WIRE 16 144 16 96 WIRE 352 144 352 96 WIRE 480 144 480 96 WIRE -160 160 -160 96 WIRE 192 160 192 96 WIRE 544 160 544 96 WIRE -336 272 -336 224 WIRE -160 272 -160 224 WIRE -160 272 -336 272 WIRE 16 272 16 224 WIRE 16 272 -160 272 WIRE 192 272 192 224 WIRE 192 272 16 272 WIRE 352 272 352 224 WIRE 352 272 192 272 WIRE 480 272 480 224 WIRE 480 272 352 272 WIRE 544 272 544 224 WIRE 544 272 480 272 WIRE -336 352 -336 272 FLAG -336 352 0 FLAG -336 16 0 SYMBOL voltage 16 128 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(-35 35 0 .005 .005 0 .01) SYMATTR InstName V1 SYMBOL ind 496 240 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L1 SYMATTR Value .845 SYMBOL ind 64 112 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L2 SYMATTR Value .845 SYMBOL cap 176 160 R0 SYMATTR InstName C2 SYMATTR Value 3e-6 SYMBOL cap 528 160 R0 SYMATTR InstName C1 SYMATTR Value 3e-6 SYMBOL voltage 352 128 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(-35 35 0 .005 .005 0 .01) SYMATTR InstName V2 SYMBOL voltage -336 128 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(-35 35 0 .005 .005 0 .01) SYMATTR InstName V3 SYMBOL cap -176 160 R0 SYMATTR InstName C3 SYMATTR Value 3e-6 SYMBOL cap -208 -240 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C4 SYMATTR Value 3e-6 SYMBOL voltage -336 -192 R0 WINDOW 0 -42 0 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V4 SYMATTR Value PULSE(-35 35 0 .005 .005 0 .01) SYMBOL voltage -144 -80 R180 WINDOW 0 -43 116 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V5 SYMATTR Value PULSE(-35 35 0 .005 .005 0 .01) SYMBOL cap 112 -208 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName C5 SYMATTR Value 3e-6 SYMBOL voltage 0 -192 R0 WINDOW 0 -42 -2 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V6 SYMATTR Value PULSE(-35 35 0 .005 .005 0 .01) SYMBOL voltage 192 -80 R180 WINDOW 0 -44 115 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V7 SYMATTR Value PULSE(-35 35 0 .005 .005 0 .01) SYMBOL cap 464 -240 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C6 SYMATTR Value 3e-6 SYMBOL voltage 336 -192 R0 WINDOW 0 -44 -3 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V8 SYMATTR Value PULSE(-35 35 0 .005 .005 0 .01) SYMBOL voltage 528 -80 R180 WINDOW 0 -38 106 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V9 SYMATTR Value PULSE(-35 35 0 .005 .005 0 .01) SYMBOL ind 368 -304 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L3 SYMATTR Value .845 SYMBOL ind 0 -208 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L4 SYMATTR Value .845 TEXT -320 304 Left 0 !.tran .1 JF
From: Jon Elson on 22 Jul 2010 18:35 markp wrote: > Hi All, > > I need to drive capacitor with a triangle wave with no DC across the > capacitor (i.e. a symmetrical bipolar drive but triangular) but it has to be > efficient, i.e some kind of energy retrieval. > > Is it possible to use standard H bridge circuits to do this? Does anyone > have any links or app notes? You must put an inductor in series with the capacitor. otherwise, when the H-bridge switches, the current will be very high. The inductor value should be chosen based on the frequency, capacitor value, etc. if the triangle wave frequency is high, you can just drive the bridge at the desired frequency, and a properly chosen inductor will give a very close approximation to a triangle wave (or sine wave, or what have you). If it is a low frequency, then you need to provide a PWM drive to the bridge to get the waveform you desire at the capacitor, or a very large inductor. Jon
From: markp on 22 Jul 2010 20:26 "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in message news:ig7h46pkocehk7qihosuh2nkon3lbeuk23(a)4ax.com... > 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 Brilliant! Why didn't I think of that? Shouldn't cost much to make. All I need to do is find out where I can get component F1 and a 1 picoohm resistor. The latter part might require a cryogenic chamber and some liquid helium. I think you have far too much time on your hands sir ;)
From: Jim Thompson on 22 Jul 2010 21:05 On Fri, 23 Jul 2010 01:26:37 +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:ig7h46pkocehk7qihosuh2nkon3lbeuk23(a)4ax.com... >> 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 > >Brilliant! Why didn't I think of that? Shouldn't cost much to make. All I >need to do is find out where I can get component F1 and a 1 picoohm >resistor. The latter part might require a cryogenic chamber and some liquid >helium. > >I think you have far too much time on your hands sir ;) > Naaaah! I whip that kind of stuff out in seconds. Definitions: F is a current controlled current source, i.e. an ideal current mirror 1p is a resistor to keep PSpice happy. LTspice builds this into their inductor model... in PSpice it has to be separate (until I decide if I should edit the symbol :-) ...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: legg on 22 Jul 2010 22:56
On Thu, 22 Jul 2010 00:53:47 +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 >>> >> A single ended load would require a single ended source - a >> half-bridge. >> >> A triangle wave is generated by a constant current, reversing, but >> residual DC can only be limited by the accuracy of the modulator. >> >> Driving purely inductive or purely capacitive loads is as efficient as >> driving a short circuit, no matter what the drive method. >> >> RL > >Come again? I can create a pair of constant current sources with transistors >and resistors and alternately charge and discharge the capacitor with them. >But that's not efficient... > >Mark. > Neither is any other method of driving a short circuit. Given a large enough and perfect enough inductor, and ideal switches, a short or a capacitor can be driven efficiently by reversing the inductor's polarity at the waveform peak. That would require 4 switches. Given imperfect and realistically sized components, a half bridge can reverse it's output inductor current in a finite time period while supplying approximately constant current of the correct polarity, with a modest ripple component and reasonable losses. RL |