Forums

LTSpice high voltage capacitors

Started by bitrex February 4, 2016
LTSpice seems to have a discouraging lack of "high voltage" (> 100V) 
electrolytic capacitors in its standard library.

Is there a third party library that's good to use?

Does it matter much for simulation purposes? Thanks.
On Thu, 4 Feb 2016 11:16:41 -0500, bitrex
<bitrex@de.lete.earthlink.net> wrote:

>LTSpice seems to have a discouraging lack of "high voltage" (> 100V) >electrolytic capacitors in its standard library. > >Is there a third party library that's good to use? > >Does it matter much for simulation purposes? Thanks.
No. The only time voltage on a cap would matter would be if the model included capacitance variations with applied voltage. For simulation purposes a capacitor is a capacitor is a capacitor... ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On 02/04/2016 11:20 AM, Jim Thompson wrote:
> On Thu, 4 Feb 2016 11:16:41 -0500, bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> LTSpice seems to have a discouraging lack of "high voltage" (> 100V) >> electrolytic capacitors in its standard library. >> >> Is there a third party library that's good to use? >> >> Does it matter much for simulation purposes? Thanks. > > No. The only time voltage on a cap would matter would be if the model > included capacitance variations with applied voltage. > > For simulation purposes a capacitor is a capacitor is a capacitor... > > ...Jim Thompson >
And I would guess that all things being equal, a higher voltage eletro capacitor is going to have higher ESR for the same value, just because the dielectric is going to be physically thicker and more loss is going to be incurred polarizing it. Don't know exactly, not like, a capacitor expert...
On Thu, 4 Feb 2016 11:37:52 -0500, bitrex
<bitrex@de.lete.earthlink.net> wrote:

>On 02/04/2016 11:20 AM, Jim Thompson wrote: >> On Thu, 4 Feb 2016 11:16:41 -0500, bitrex >> <bitrex@de.lete.earthlink.net> wrote: >> >>> LTSpice seems to have a discouraging lack of "high voltage" (> 100V) >>> electrolytic capacitors in its standard library. >>> >>> Is there a third party library that's good to use? >>> >>> Does it matter much for simulation purposes? Thanks. >> >> No. The only time voltage on a cap would matter would be if the model >> included capacitance variations with applied voltage. >> >> For simulation purposes a capacitor is a capacitor is a capacitor... >> >> ...Jim Thompson >> > >And I would guess that all things being equal, a higher voltage eletro >capacitor is going to have higher ESR for the same value, just because >the dielectric is going to be physically thicker and more loss is going >to be incurred polarizing it.
Maybe not. Check some data sheets.
> >Don't know exactly, not like, a capacitor expert...
Capacitors in Spice will happily work at 5 megavolts. So will most diodes. Look up the typical ESR (and ESL if it matters) on a candidate cap and force those values in Spice, internal to the cap or with external parts. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Thu, 4 Feb 2016 11:37:52 -0500, bitrex
<bitrex@de.lete.earthlink.net> wrote:

>On 02/04/2016 11:20 AM, Jim Thompson wrote: >> On Thu, 4 Feb 2016 11:16:41 -0500, bitrex >> <bitrex@de.lete.earthlink.net> wrote: >> >>> LTSpice seems to have a discouraging lack of "high voltage" (> 100V) >>> electrolytic capacitors in its standard library. >>> >>> Is there a third party library that's good to use? >>> >>> Does it matter much for simulation purposes? Thanks. >> >> No. The only time voltage on a cap would matter would be if the model >> included capacitance variations with applied voltage. >> >> For simulation purposes a capacitor is a capacitor is a capacitor... >> >> ...Jim Thompson >> > >And I would guess that all things being equal, a higher voltage eletro >capacitor is going to have higher ESR for the same value, just because >the dielectric is going to be physically thicker and more loss is going >to be incurred polarizing it. > >Don't know exactly, not like, a capacitor expert...
You may have to add series R to model ESR (and L for ESL)... the nominal Spice capacitor is ideal. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
"bitrex" <bitrex@de.lete.earthlink.net> wrote in message 
news:B7Lsy.278309$b8.53334@fx29.iad...
> And I would guess that all things being equal, a higher voltage eletro > capacitor is going to have higher ESR for the same value, just because the > dielectric is going to be physically thicker and more loss is going to be > incurred polarizing it. > > Don't know exactly, not like, a capacitor expert...
Not by much. Certainly the dielectric isn't the problem (the dielectric itself is a darn sight near ideal, compared to the dissipation factor of an ugly old 'lytic!). ESR is entirely due to electrolyte. Which is also why it varies so much at low temperature -- ion mobility. HV caps use thicker foil (with coarser etching and deeper anodization), so the spiral has to be a little thicker for a given C*V rating, and will have slightly fewer turns; so you should expect the ESR to be higher (less electrolyte cross section), but not really by much. Speaking of C*V rating, electrolytics are almost constant in C*V, with respect to the rated values of C and V. Which is not the same as C*V^2, which is energy. So they get quite a bit more energy-dense at high voltage ratings, so if you ever needed to store just a huge wad of energy, on relatively short notice, high voltage (up to 500V) is the way to go! Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
In article <JPKsy.320151$QG6.209541@fx31.iad>, 
bitrex@de.lete.earthlink.net says...
> > LTSpice seems to have a discouraging lack of "high voltage" (> 100V) > electrolytic capacitors in its standard library. > > Is there a third party library that's good to use? > > Does it matter much for simulation purposes? Thanks.
Why would you worry about that? Jamie