tl431 and optocoupler feedback for sg35252

[babatundeawe]

can someone help me fine tune this circuit for feedback/error correction for sg3525 pushpulll configuration. i need to get the values of the resistor right. i dont want to use a transformer in between just want to sense the voltage directly.

thanks

 

[babatundeawe]

any help from anybody?

 

[picgak]

I can help but I could not open the file you posted
I extracted your file. is it a Tinycad file?

 

[babatundeawe]

thanks picgak,

just downloaded it now and it did open. u can use proteus to open it.

i hav converted it to pdf

thanks

 

[picgak]

I have opened your circuit and made a slight change in it (see fig) so what is your required voltage at the output point which I marked as V

 

[babatundeawe]

thanks

ok i want to use this as a feedback mechanism for sg3525 pwm inverter. so i wish to measure the output voltage directly (230v)

thanks for your help

 

[picgak]

use 56k for R2 and 2.2k variable as Rv1 give 2.5v as ref to pin2 of sg3525

 

[pplus]

i want to use this as a feedback mechanism for sg3525 pwm inverter. so i wish to measure the output voltage directly (230v)

TL431
Vka - 37V (MAX)
In this scheme, it will burn.

 

[babatundeawe]

use 56k for R2 and 2.2k variable as Rv1 give 2.5v as ref to pin2 of sg3525

ok i will give it a try and feed you back

thanks

 

[pplus]

+V1 <= Vka_max(37V)

 

[babatundeawe]

@pplus

can u tell what u mean by Vka? is the cathode voltage of tl431 or that of the optocoupler?

thanks

 

[picgak]

it means maximum voltage the TL431 can withstand is 37v
so +V1 marked in above circuit should not be above 37V

 

[babatundeawe]

ok guys i think ihave to order for another one cos i guess this one i have appears to be damaged due to high voltage.