TOP258YN Voltage Drop
Hello everyone,
I would like your help with the TOP258YN circuit that I created with PI Expert. The issue I'm having a problem with; Although I chose the output current as 6A, the SMPS turns itself off around 300mA. I would be glad if you let me know about the reason for this. The datasheet of the Transformer I have used and the output of the PI expert are below.
Thank you.
Comments
Firstly, thank you for your reply. When I check my connections my transformer connections appear as you specified. Is it possible for you to make a design with the included transformer and top258YN? I could not fully fix the problem.
I was able to create an appropriate design for you using your original transformer, but unfortunately, it will require the next size larger TOPSwitch (TOP259), unless you can accept lower output power. I have included a PDF of the PIXLS design for your reference.
PI Expert has a glitch that caused the program to select 160V rated caps for your output filter. This extreme rating is not necessary for your design - 35V rated caps will do. Suggested series are UCC KZE or Panasonic FM, 1000uF, 35V. Three will be needed in order to carry the ripple current.
First off, according to the files presented, the design failed, and exceeds TOPSwitch current limit at max power, low line. This could possibly be fixed by entering a higher value for estimated efficiency. The 75% value used is too conservative. I would advise trying 82-83% instead. It also may be necessary to increase the minimum operating voltage to 90 VAC from 85 VAC. You may also be able to get some extra operating margin by increasing the bulk capacitor size to 470 uF. You also have the option of using the next size larger TOPSwitch..
All the factors above address the problem of delivering maximum power at minimum line voltage. As for your actual problem, I am assuming that the power supply goes into autorestart protection mode ("hiccups") at the 300 mA load you mention. The first thing you need to do is to check all the diodes in the circuit to make sure they are inserted with the proper polarity. Also, it is a good idea to check the transformer connections. According to the transformer spec provided, B+ should be connected to Pin 1. The TOPSwitch drain should be connected to Pin 3. The anode of the bias rectifier (D2) should be connected to Pin 6, and Pin 8 should go to
Primary return (the minus side of bulk capacitor C2). Finally, the anode of output diode D3 should be connected to pins 15 and 16, while pins 9 and 10 should be connected to secondary return.