TOP258YN - Power supply output varies with load over entire range
I use PI Expert to design a power supply with Vout=27,6V - Ioutmax=2,40A.
The problem is that output voltage varies with load.
I just attached an image with circuit schematic.
Optocoupler is 4N35 instead of LTV817A; can this affect output?.
A question: why can´t attach a file with your own extension (.uds)?
Thank you for your response.
Comments
Can I use optocoupler with darlington instead of transistor output for improve performance in DC feedback (CTRmin = 500)?.
This is the identical problem I am having with the design posted on the forum under "Top254Y-UI-28Vo-1.1A Does not Regulate," which has the identical feedback loop circuit.
The problem is not the use of a different optocoupler since I am using the identical PI8 recommended part.
There is no recorded resolution to the posted entry from pablomkz. Please respond with the solution that was proposed or a solution for the "Top254Y-UI-28Vo-1.1A Does not Regulate" post.
Since the forum does not allow .uds file attachments, the attached .pdf file is the designed-to .uds file renamed to .pdf. Please rename it to .uds and review it to tell me what the design flaw is.
Thank you.
Stewarth
stewart@driven-technologies.com
559-645-1034
This is the identical problem I am having with the design posted on the forum under "Top254Y-UI-28Vo-1.1A Does not Regulate," which has the identical feedback loop circuit.
The problem is not the use of a different optocoupler since I am using the identical PI8 recommended part.
There is no recorded resolution to the posted entry from pablomkz. Please respond with the solution that was proposed or a solution for the "Top254Y-UI-28Vo-1.1A Does not Regulate" post.
Since the forum does not allow .uds file attachments, the attached .pdf file is the designed-to .uds file renamed to .pdf. Please rename it to .uds and review it to tell me what the design flaw is.
Thank you.
Stewarth
stewart@driven-technologies.com
559-645-1034
After a lot of changes in design, I encountered that the problem is the proximity of capacitor between Control pin and GND; it MUST be as close as possible to this pin (I just put it OVER it), and this resolve this problem. I hope that I can help you with this comment.
Thank you for the reply. I believe you are talking about the 0.1 uf cap C4 between pin C and the bias rtn. My C4 is mounted on the bottom side 3 mm from the C and F pins. I will move it closer.
I see you have a 7.xxk ohm resistor from the Top x pin to the bias return. I cannot make out the value of the ".xx" I connected the X pin directly to the bias return. I will try your approach.
I would gladly pay for any additional consultation as I am facing a hard schedule stop and have not been able to get any response from anyone else.
Thank you,
Stewart Hough
stewart@driven-technologies.com
559-645-1034
If DC feedback gain is too low, the load regulation will be poor.
The CTR of an opto coupler has direct impact on the DC feedback gain, and it is recommended to use an opto coupler with higher than 100 CTR.