Hi


My circuit is getting input supply of 7V and 7A from other board that is a dc-dc converter with 100KHz switching frequency. How can i design a basic filter for my board.

 

I need to filter the input supply of my board. My board is getting input supply of 7V and 7A from other board that is a dc-dc converter with 100KHz switching frequency and ripple voltage of the converter is 40mV max . How can i design a basic filter for my board.
I have a space constraint, I cannot use the bulky inductors.

 

I need to filter the input supply of my board. My board is getting input supply of 7V and 7A from other board that is a dc-dc converter with 100KHz switching frequency and ripple voltage of the converter is 40mV max . How can i design a basic filter for my board.
I have a space constraint, I cannot use the bulky inductors.

The most effective way of doing what you are asking is with a common mode and a differential mode choke and their associated capacitors. It will be most helpful to specify the maximum ripple you wish to have on the input. Would it be possible to tweak the components in the SMPS to get a more favorable ripple behavior? For examples, replace the output capacitor with a part having a lower ESR?

 

40mV peak-to-peak? 14mV rms - it doesn’t sound too bad to me.
What is it being used for?

 

40mV peak-to-peak? 14mV rms - it doesn’t sound too bad to me.
What is it being used for?

Ripple & Noise (max) (typ) is 40mV

 

The most effective way of doing what you are asking is with a common mode and a differential mode choke and their associated capacitors. It will be most helpful to specify the maximum ripple you wish to have on the input. Would it be possible to tweak the components in the SMPS to get a more favorable ripple behavior? For examples, replace the output capacitor with a part having a lower ESR?

ripple voltage of the converter is 40mV max

 

Someone suggested me to use
powerline ferrite bead of 100khz at high impedance, 100ohm approx
10A rating

 

The most effective way of doing what you are asking is with a common mode and a differential mode choke and their associated capacitors. It will be most helpful to specify the maximum ripple you wish to have on the input. Would it be possible to tweak the components in the SMPS to get a more favorable ripple behavior? For examples, replace the output capacitor with a part having a lower ESR?

will u suggest me any example ?

 

At 100 khz, inductors won’t be bulky, don’t handicap yourself by rejecting the most cost-efficient and viable solution.

 

At 100 khz, inductors won’t be bulky, don’t handicap yourself by rejecting the most cost-efficient and viable solution.

Will u suggest me a circuit , this is first time I am making filter

 

Someone suggested me to use
powerline ferrite bead of 100khz at high impedance, 100ohm approx
10A rating

100 ohm reactance at 100 Khz means about 16 microhenries. No ferrite “bead” on its own will give that inductance value.
You require a proper inductor, which can carry the load current, like this. 10 uH should suffice.

 

At 100 khz, inductors won’t be bulky, don’t handicap yourself by rejecting the most cost-efficient and viable solution.

Inductor for 10A is difficult to get and might be big if we get also

 

100 ohm reactance at 100 Khz means about 16 microhenries. No ferrite “bead” on its own will give that inductance value.
You require a proper inductor, which can carry the load current, like this. 10 uH should suffice.
View attachment 306346

So I can make a pi filter by using this coil, with cut-off frequency of 10KHz ?

 

Yes, only need to calculate the required output capacitor

 

Yes, only need to calculate the required output capacitor

Thanks for the input, I will try to design a pi filter using the above inductor.

I was checking ferrite bead solutions also and my some suggested me to try powerline ferrite bead. I dont understand but how I can select the powerline ferrite bead parameters for my circuit.

This is one ferrite bead I have checked
28F0121-0SR-10 Laird-Signal Integrity Products | Filters | DigiKey