multiple SMPS Voltages

[goldsmith]

Muhammad , do you know meaning behind word compensation really ? i didn't tell comparison , i told compensation .

 

[muhammadali_16]

didnt used compensation

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didnt used compensation

 

[goldsmith]

Ha ha ! the problem can be because of it ! a voltage mode converter without compensation ? of course the result should be awful ! did you see the datasheet and suggestions ?

 

[muhammadali_16]

i have checked. before filteration, the voltage fluctuate b/w -10 to 9V. after MUR, the voltage is -1 to 9.8V(before inductor)

 

[goldsmith]

9.8/2=4.9 . it is not enough ! consider that when D.C is around 50 percent , the out put voltage will be around 5 volts ( if feed back loop allow it to increase ) . it is not good . it should be at least 20 volts before your filter .
By the way , how you have calculated the out put capacitor ? and of course the inductor ?

 

[muhammadali_16]

there was a formula of inductor which you told me but i choose capacitor randomly

The logic which you told in above reply, kindly tell me with example of input and output voltage

 

[goldsmith]

Hi Muhammad

but i choose capacitor randomly

It is not good ! i have given you a best formula for that too .

The logic which you told in above reply, kindly tell me with example of input and output voltage

What you are referring to ?

 

[muhammadali_16]

you have not given me the formula to calculate the capacitor. i dont rememeber. may be it would be my mistake to not to pick any of capacitor formula. can you please tell me again

and the logic of voltage before the filteration ( can you tell me complete what is the logic why my desired voltage should be 20V)

 

[goldsmith]

Hi Muhammad
Of course i can give you the formula again :
C=(80*10^-6)*dI/Vr
and L=0.5*vo*T/Ion
And about why i told 20 volts , suppose that your driver can't increase the D.C more than 50 percent ( however it can increase it , a bit higher ) then if your secondary voltage is 20 volts , at maximum D.C the out put voltage can be around 10 volts . and of course if you need 5 volts , it will have 5 volts to compensate the load ! my mean is when your load is heavy voltage will decrease , thus the controller will increase the D.C , ( it has 5 volts to add , to stabilize the out put voltage in your desired range ) . you understand ?
Good luck
Goldsmith