TOP260Y short circuit trouble
Hello, I've designed a board with TOP260Y - with this design I can produce a power supply 24V 4A and 15V6,5A universal input 88-265Vac
I've put resistor to control Voltage start up and current limit in function of input voltage.
all works well, but I have some trouble during output short circuit. In some input voltage values (e.g 90vac or 265VAc), short circuit causes hiccup transition on Vout.
In some other condition (e.g. 180Vac) the output isn't go in hicupp mode and continue to supply uncontrolled current!!
Pin C during Hicupp goes down till 4-5V - during high uncontrolled current pin C remain stable on 5,5V - 6V....
Seems that this condition is more evident on 15V circuit.
I see an old topic (2014) with the same trouble...
I don't understand how primary controller can reach this hiccup protection, what parameters I need to check?
In attached electrical schematic of primary side - as youcan see it's a simple circuit....
best regards
Marco
Files
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| TOP260.PNG | 86.73 KB |
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I ran the design in PIXLS (useful for smoking out design issues), and the supply won't even deliver the specified output power over the input line range unless the input cap is increased to 680uF. I've attached a .PDF of the PIXLS file for guidance.
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| TOP260_194W_15-24V_Uni_Input_PQ3535.pdf | 804.91 KB |
BTW, a colleague of mine made an excellent suggestion. If you split the design into 2 separate independently regulated supplies (one 24V/4A supply and one 15V/6.5A supply), the overall design becomes much less challenging (two ~100W universal input supplies instead one nearly 200W, universal input supply). I think you'll also find it solves your short circuit issue.
Some questions here, and some comments:
1) What is the function of the second optocoupler feeding the control pin?
2) The value of C30 is too small - it should be 47uF. Not only does this capacitor store energy used during startup, but it also plays a role in loop compensation.
3) Using an electrolytic capacitor (C14) in the primary snubber circuit is a bad idea - they have high ESR, causing high peak drain voltage excursion, and will have a short lifetime as used. A ceramic or film capacitor would be a better choice.
4) Why do you have a jumper for operating frequency? Please choose one operating frequency or the other and stick to it. You also need to design the transformer based on the operating frequency chosen. A transformer designed for 132kHz operation may not function properly at 66kHz, and one designed for 66 kHz may operate too deeply in continuous mode if run at 132 kHz..
5) Using a trim pot on the X pin is not a good idea - if the wiper lifts, you loose a good part of your current limit reduction.
6) Why is the primary bias supply regulated? A simpler approach would work just as well. Check the example circuits in the data sheet.