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hii
I am testing 230VAC to 12VDC smps but top271 ic is continuously switching 1.6 sec time . over voltage ,over current and under voltage is disable
pleas help me what is problem in design
Attachments
TSA AstroPED 230V SMPS V2.0 28082018 Schematic PDF file.pdf
Your posts suggest you hear audible noise from your flyback converter. There is a type of faulty behavior that creates On-Off buzzing, as the circuit operates okay for a few cycles, then is idle for a few cycles. It is known as 'hiccup' mode.
Or, since you state a time of 1.6 seconds, is it the IC going into shutdown, then starting up again? Often such a safeguard is built into IC's to protect against overvoltage, overcurrent, etc. However your post says it's disabled. On the other hand do you attach a load at all times? Many smps require some amount of load for proper operation. With no load the output can be unpredictable.
What is your pri:sec turns ratio?.
Have you properly interleaved primary and secondary?
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your RT2 may need lowering a bit in value.
Do you have a smooth 12vout when the load is no_load?
Do you have a smooth 12vout when the load is 2A?
You may need an RC across the RT2
The CTR of the PC817 appears to be anything from 50% to 600%...this could be your problem, because if ctr is very low, then your RT2 could be too high ohmic value.
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by the way, you do know that power.com do offer a free program which calculates all the circuit values for you?
I think its called "PI-EXPERT" or something.
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