I started few days ago searching for possible alternative for AC/DC two outputs module VTX-214-005-0512. It's price at the beginning of this year was under 6 GBP on
Farnell, and since then it jumped up to 14 GBP! Why is that, I don't know. For crowdfunding campaign I managed to buy it directly from manufacturer for 5 GBP.
So, we need small and cheap flyback and two most problematic components are controller and transformer. I don't like an idea of winding my own transformer that should withstand AC mains and it is small enough. Fortunately I found for me a new source of magnetics and that is Feryster from Poland. They have a plenty of ready-made transformers and various chokes used for switching applications. In addition it seems that they took extra time to support Power Integrations controllers such as TNY266.
Feryster has two outputs transformer TI-EE16-1534, that is available thru TME (
link) and
Remagas. I've contacted Feryster and they offer me even bare PCB for TNY266 evaluation that is published in Power Integrations
EPR-9.
![](https://i.imgur.com/MOYNPyBl.jpg)
As a first step I decide to use component values as specified in schematics from page 4 of EPR-9:
![](https://i.imgur.com/TbpEyvah.png)
As we can see only zener diode is used for regulating output. That is just fine in our case since that 5 V is used for driving relays and LEDs on Arduino Shield, and it's further decreased to 3.3 V with an LDO. TNY266 operates on 132 kHz that is jittered to reduce EMI. It's not audible at all regardless of connected loads that I tried.
Interestingly it starts to work with only 40 Vdc, therefore for first start I've used successfully EEZ H24005 outputs coupled in series for total of 80 V
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
.
You can see below few measurements on primary and secondary side (
all measurements on primary side was conducted with isolated scope!).
First screenshot is TNY266
Drain (pin 5) where Vin=230 Vac and without any load (LED only):
![](https://i.imgur.com/iQjc5wwl.png)
Same pin, but this time with 8R2 power resistors connected to main output (+5V):
![](https://i.imgur.com/YQbdE0vl.png)
As we can see peaks goes up to 540 V, despite the used clamping (200 V TVS + schottky). I don't know how it looks to you, maybe there is some room for improvement here and I'll try to use RCD snubber instead. From the other side the PCB layout is really not representative (despite the fact that is designed by manufacturer not Feryster who sold it to me). Actually it looks like they didn't follow even their own recommendations for good layout.
Next screenshot is output ripple on +5V output without load (LED only):
![](https://i.imgur.com/0AvSQNYl.png)
Again, but this time with 8R2 load connected:
![](https://i.imgur.com/sdAPlcCl.png)
Finally we can see how output ripple looks like on second output (+12V) with 66R load connected, and 8R2 on main output. It's expectedly much higher since it lack LC filter as in case of main output. But even as is it should be fine for powering cooling fan.