Did anyone notice that his first Post that he linked to was in "Homework Help" ?
It would appear that the Thread-Starter doesn't have a good grasp of the basics,
and is hoping that there is a one paragraph answer to an entire text-book of theory.
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OPA! the One Paragraph Answer. The next internet meme.

 

Doing a passive filter for high current and high voltage is going to run into a number of problems involving component values and properties. I don't know if an active filter will do anything for the TS because he has offered nothing like a specification for such a filter.

Hi Papabravo,

Is that not good idea to use the passive filter for high current and high voltage ?. Actually I don't how much noise/frequency it has at the MOSFET, so that's I can't able to answer your posts. Can we excepts any noise at the MOSFET?. But, I'm assuming that there will be some noise/frequency and I want minimize the noise as much as I can.

How much noise/frequency if you filter then it is called a good filtering?.

Which low pass filter is good idea to choose either RC or LC or RLC low pass filter?. And also please explained why you chosen that?.

 

Look up low-pass filters on the internet. There are many sites with information on this.

 

Hi Papabravo,

Is that not good idea to use the passive filter for high current and high voltage ?. Actually I don't how much noise/frequency it has at the MOSFET, so that's I can't able to answer your posts. Can we excepts any noise at the MOSFET?. But, I'm assuming that there will be some noise/frequency and I want minimize the noise as much as I can.

How much noise/frequency if you filter then it is called a good filtering?.

Which low pass filter is good idea to choose either RC or LC or RLC low pass filter?. And also please explained why you chosen that?.

For a system with high output voltage and/or current a passive filter is IMHO the only way to go. Operational amplifiers, used in active filters, are not known for their ability to deal with high voltages and currents. Maybe you know something that I don't know. I have been retired for 7 years or so. If you want to have a low pass filter, that will greatly attenuate high frequency content, that has a corner frequency of say 30 Hz., you will find that it requires component values that may be pure unobtainium. That means that nobody makes the components that you need and what is worse you cannot buy the materials to fabricate what you need at any price.

That said, time and technology move on and again, maybe you know something that I don't.

 

Wait until you see an interfering signal and then design a filter to remove that.

 

Hi all,

I have a 5V, 12V and 24V supplies in my circuit, but as we know that all are DC voltage, so there is no frequency. In this case, how we can design a filter circuit for example RC and LC filter circuits?.

Normally you would be either trying to remove some ripple on the DC such as at 100Hz or 120Hz or some high frequency such as 20kHz for a switching power supply. In any case, you can get an idea how well the filter will work by doing an AC analysis on the network you intend to use. You then can look at the output with different frequency inputs like 120Hz to see how well the filter attenuates that. If it is a switching power supply then you will want to see how it attenuates the 1st harmonic as well as some odd harmonics. That gives you an idea how well it will work to filter the DC. At the higher switching frequencies like 100kHz usually only a small inductor is needed combined with a small capacitor because the frequency is so high. At 120Hz however it takes a larger inductor if you really want to do it that way.

The filter transfer function is good to know for this. Calculate the AC transfer function and you can then go from there. If you do a time domain analysis you can even plot the output, although in the case of the lne frequency full wave rectifier filter it gets a bit harder to do because you have to solve for both voltage and time together unless you assume some typical output from the rectifiers.
A switcher will either have a squarish wave output or a triangulerish wave output. You can look up the harmonics for both of these and test them with the fitter. Many application calculations are good enough when you go up to the 7th or 11th harmonic because secondary real life factors eat up the higher ones, but you may want to go up higher just to see how it works.

 

UPDATED: Added a time domain plot.

Just to add a little more help, you can find the general equation for a 2nd order filter and vary the damping factor and plot the results. You can also then normalize for the peak gain to see how each filter compares when the peak gain is the same for all damping factors.

The first pic (02) is made from four such damping factors as labeled and that is the response in dB, and the second pic (03) is two of those filters with different damping factors normalized to a peak gain of 1 (0 dB).
The third pic added later (04) is a time domain plot. This shows the time response for several damping factors. Noteworthy is the settling time to some percent within the final value like 1 percent or 5 percent. When the response is underdamped the settling time to some percentage is -ln(p)/d where d is the damping factor and p is the percent expressed as a fraction (1 percent = 0.01). This is important for analog to digital front end anti aliasing filters so you know when it is the soonest time you should take a sample. If you take a sample before that time the results will be somewhat random and so not as useful.
For an overdamped response the settling time could be very long, and for critically damped it would be about 7 seconds. The tradeoff is better DC filtering for overdamped but longer settling time.

Using these kinds of graphs you can get a quick idea how this works.
You can find the general expression for a 2nd order filter on the web. To normalize you have to calculate the general transfer function and solve for the peak w, then use that to normalize the transfer function, then plot.
Just one note, and that is when you normalize for the peak response if there is no peak response you will get a complex number which tells you there is no peak so you cant normalize with that particular damping factor(s).

Lastly, to find out what components vary the damping factor so you would know what to do to change that with the actual circuit, you would compare the transfer function with the general 2nd order transfer function and solve for the damping factor. That gives you an expression with one, two, or all three components in it that can change the damping factor (you will find out which it is once you calculate this).
Once you solve for the damping factor in terms of the component values you can then set the damping factor to whatever you think is best as judged from the plots you do.