Mohit,
I'm not sure I can add useful information but I felt that those who
would be able to assist would need a bit more info to get interested.
However - I have set up a simplistic simulation in PSpice.
With the values shown and 100mOhm inductor resistance I get about
480mA ripple at 5A of current (10% duty cycle).. This is not the worst
case so you may want to increase the inductance and / or capacitance
somewhat.

The current ripple through C1 is greater than C2 and is about 670mA
pk-pk (350mA for C2) so you may need to check this against the spec.

With respect to your origonal question  - I don't know  - but
paralleling capacitors will increase the total capacitance and
decrease the ripple current and resistive loss,  through each so can
only be a good thing.
I'm not aware of any reccomendations wrt derating MLC caps when
paralleling. In this case I'd make it up and monitor the capacitor
(and inductor) temperatures under various running conditions.

Richard P

On 04/10/06, Mohit M. (Lists) <mohit.lists@gmail.com> wrote:
> Richard,
>
> Thanks for your reply. The circuit looks something like this:
>
>                        ____ Peltier (1.7ohm)
>                   ----|____|----
>                   |            |
>                   |            |
>         L (100uH) |       C1   |   L (100uH)
>              ___  |     ||     |  ___
>       V1 o---UUU--o-----||-----o--UUU---o V2
>                   |     ||     |
>                   |            |
>                   |            |
>               C2 ---          --- C2
>                  ---          ---
>                   |            |
>                  ^^^          ^^^
>                  GND          GND
>
>
> C1,C2 are 10uF. V1 and V2 are outputs from an H-bridge running at
> 10kHz (12Vp-p, 10A). Direction of current into peltier can be changed
> (V1-V2 and V2-V1) to either heat or cool. Aim of this LC filter is to
> filter output of H-Bridge to less than 10% voltage ripple.
>
> > ripple current
> Calculated to about 150mA AC. The datasheet from manufacturer suggests
> up to 200mA is okay.
>
> >load type
> Basically resistive. Peltier module. Manufacturer's specs says
> 1.70ohm.
>
> > other filter components,
> Two Inductors. Differential LC filter.
>
> > capacitor types you are considering,
> Murata: 16V,10uF in SMD1210. Dielectric X7R. Tolerance +/-10% and
> change across -55C to 125C +/-15%.
>
> > Working temperature
> Enormous amounts of forced-air cooling. So working temperature should
> be <<50C.
>
> > consequences of failure
> Ripples in the voltage across peltier, leading to quicker failure of
> module.
>
> > actual application
> Peltier heater/cooler.
>
> Looking forward to your help,
> Mohit.
>
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