I used TNY267 IC in my SMPS without connecting load the output is coming. but when i connect a load it's not working (it comes like ON and OFF). when i check PWM of the IC it shows fluctuating not constant signal. but i change the IC then also the same thing is coming so problem is not with a IC. only the signal is not coming properly. here i attached the circuit also tell me some tips.
Attachments
Hi, maybe incorrect secondary winding polarity?
This design is flyback topology, and output power comes from transformer at pause moment when there's no current in primary winding, and is stored in output capacitor (1000uf specified in your picture). Capacity depends on output power. If this capacitor is bad, you may have symptoms like this, low output power ,but proper voltage when no load. At first , try to replace that capacitor. Output diode needs to be fast, for 15v output, it needs to be 100v + reverse voltage. As example , UF540x series . Schottky is better, but they are mostly for voltages less than 100V. Maybe try UF4007, if your design is low current. Unstable pulses can be because of improperly designed compensation of 431 ic or main ic is limiting power ( overload? ).
This design is flyback topology, and output power comes from transformer at pause moment when there's no current in primary winding, and is stored in output capacitor (1000uf specified in your picture). Capacity depends on output power. If this capacitor is bad, you may have symptoms like this, low output power ,but proper voltage when no load. At first , try to replace that capacitor. Output diode needs to be fast, for 15v output, it needs to be 100v + reverse voltage. As example , UF540x series . Schottky is better, but they are mostly for voltages less than 100V. Maybe try UF4007, if your design is low current. Unstable pulses can be because of improperly designed compensation of 431 ic or main ic is limiting power ( overload? ).
Hi, No remedie for your problem but...
Have a look at this power supply:
https://nl.aliexpress.com/item/32827739851.html?gatewayAdapt=glo2nld
I use a double PSU from 0-60V, current limited, since ages...
Instead of connecting the SMPSU direct to the AC outlet, I find it a lot safer to use my PSU.
The secondaries can also get tested when the transformer of the SMPSU is removed.
Then you now that each part of the circuit is working or not.
It works for me, so it wil help you and all other readers who are strugling the way you do.
Good luck.
Have a look at this power supply:
https://nl.aliexpress.com/item/32827739851.html?gatewayAdapt=glo2nld
I use a double PSU from 0-60V, current limited, since ages...
Instead of connecting the SMPSU direct to the AC outlet, I find it a lot safer to use my PSU.
The secondaries can also get tested when the transformer of the SMPSU is removed.
Then you now that each part of the circuit is working or not.
It works for me, so it wil help you and all other readers who are strugling the way you do.
Good luck.
Ok @Ravi6545 had a look at your schematics, but because you didn't bother to draw the internal component symbol, especially your TL431 it's not clear which package you have used and how the pins are connected (the pin numbers differs depending on WHICH package you have used), if that is meant to be a SOT23 package, then you have connected it wrong with regards to the pin numbers, back to the drawing board debugging.
EL817
TinySwitch II (TNY263-268)
ps. I have designed SMPS with Tiny Switchers and they work very well.
EL817
TinySwitch II (TNY263-268)
ps. I have designed SMPS with Tiny Switchers and they work very well.
About 431 pinout - very good catch. If use sot-23 original TL431 , they have reversed pinout in comparison to unknown chinese, found in cheep smps. Orginal TL432 have pinout identical to chinese ones. If TO-92 package is used , then they all are same i think. But if output voltage is correct without load, then i think not pinout is a issue.