Driving capacitive loads with an H bridge
in [Design]
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From: markp on 22 Jul 2010 05:02 "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. 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.
From: whit3rd on 22 Jul 2010 11:03 On Jul 21, 4:48 am, "markp" <map.nos...(a)f2s.com> wrote: > 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. Use a generator and flywheel; by shaping the poles of the generator, you can get the output to be triangle-wave-like. The flywheel is your energy-storage item, here. A motor driving the generator/flywheel makes up the energy losses. Because the generator is a simple winding like a transformer, your DC zero is assured.
From: markp on 22 Jul 2010 12:07 "whit3rd" <whit3rd(a)gmail.com> wrote in message news:1a0b2b9d-bae3-485c-96c4-e807ce292df6(a)x24g2000pro.googlegroups.com... On Jul 21, 4:48 am, "markp" <map.nos...(a)f2s.com> wrote: >> 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. >Use a generator and flywheel; by shaping the poles of the generator, >you can get the output to be triangle-wave-like. The flywheel >is your energy-storage item, here. >A motor driving the generator/flywheel makes up the energy >losses. Because the generator is a simple winding like >a transformer, your DC zero is assured. 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 so the cycle can repeat and process is efficient, much like a resonant LC oscillator but with triangle waves instead of sine waves. See my post to Jim. Mark.
From: John Fields on 22 Jul 2010 12:45 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
From: markp on 22 Jul 2010 13:05
"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? |