Problem with tny280
Hi,
Its my first time working with TNY280(dip7) but I have good experinces with other PI ICs like tny268 and lnk460.(using 1000s of them in our products)
I am using this IC with 220v ac input and around 20W output.
Lp=850uH
N=80/7
Vo=12
CORE EE2218 Ac=40um2
Opto pc817
the problem is that it operates like ON/OFF at very low frequencies depends on input voltage and load.
the ripple is very high like 5V but the average voltage is correct.
I tried different output capacitors ,feedback resistors series with TL431 anode,bypass capacitor, compensation capacitor and so on but the same problem in all cases.
Thanks in advance,
Mehrshad
Comments
Thanks,
as I mentioned I am using tl431 and tried everything related to output capacitor from 330u to 2200uf and tl431 anode resistor from 560 to 12k.
I had no problem with tny268 with different cores and voltages and loads.
maybe it relates to pcb layout, I will check...
Dear All
From 2010 on wards, we were using TNY268 IC, to drive 6W Led. We got only 0.5% complaint. But unfortunately, we got regular complaints from the filed (10%). There is no design change, compared to earlier stage, the components are same. And we tested the same IC by driving 4W, still we don't have any issue. We get the IC from your authorized supplier from Chennai. Why this happened? We just consult with our suppliers also and sent two boards for evaluation. They suggest to add MOV and X2, because of the smaller size we can't add MOV & X2 cap. One of my friend got the same issue, now he change the design and starting to use Texas Instruments. We were also planning shift... We lost many of our OEM customers, because of this issue
My question is
1. What is the issue, while the driving the IC in a 6W led driver?
2. Why there is no problem, when we drive in 4W?
3. Is there is a chance for fake part?
4. we use TN264 for 3W, it has no issue. Is there is a misprinting for TNY268 instead of 264?
It sounds like there is something wrong with regulator design or output filter -- I am assuming you are using TL431. Try using simple zener regulation to see if problem goes away. If it does then you have incorrect compensation around error amp.