- #1

Dextrine

- 102

- 7

〖 mod note: moved from technical forum, so template is missing 〗

〖 mod note: click on thumbprint image to see legible image 〗

I was wondering if anyone could provide some more insight as to how to find the current through Rc. The first picture TRANSFER1 I can find the current Ic through Rc by the following method:

Ic = (Vin - Vout)/Rc

Vout = -Vin(1/(R*s*C))

Ic = Vin(1+1/(R*s*C))

However, if I add a voltage divider network before the input, the problem becomes much more difficult for me here is my latest attempt:

Ic = (Vin - Vout - I1*R1)/Rc

Vout = (-Vin+I1*R1)/(Ra*s*C)

Ic = Vin + (Vin-I1*R1)/(Ra*s*C) - I1*R1.

Now the problem is that this current will be multiplied by CTR from an optocoupler then multiplied by a pullup resistor to get a voltage Vfb on the other end.

There's no way I can think of to write this equation as Vfb/Vin.

I'm essentially modelling a TL431 and an optocoupler per the following: http://www.onsemi.com/pub_link/Collateral/TND381-D.PDF on page 18I appreciate any help and if this is not the appropriate place to post this, please let me know where I can. I'll keep trying and if I figure it out I'll update this post.

Thanks in advance.

〖 mod note: click on thumbprint image to see legible image 〗

I was wondering if anyone could provide some more insight as to how to find the current through Rc. The first picture TRANSFER1 I can find the current Ic through Rc by the following method:

Ic = (Vin - Vout)/Rc

Vout = -Vin(1/(R*s*C))

Ic = Vin(1+1/(R*s*C))

However, if I add a voltage divider network before the input, the problem becomes much more difficult for me here is my latest attempt:

Ic = (Vin - Vout - I1*R1)/Rc

Vout = (-Vin+I1*R1)/(Ra*s*C)

Ic = Vin + (Vin-I1*R1)/(Ra*s*C) - I1*R1.

Now the problem is that this current will be multiplied by CTR from an optocoupler then multiplied by a pullup resistor to get a voltage Vfb on the other end.

There's no way I can think of to write this equation as Vfb/Vin.

I'm essentially modelling a TL431 and an optocoupler per the following: http://www.onsemi.com/pub_link/Collateral/TND381-D.PDF on page 18I appreciate any help and if this is not the appropriate place to post this, please let me know where I can. I'll keep trying and if I figure it out I'll update this post.

Thanks in advance.

Last edited by a moderator: