UCC28630EVM-572: Flyback wont work

Hi Andy,

you may need to change to UCC28631/2/4 for DC input.

Sure. It would be nice to speak to someone regarding this. Anyways,

The Flyback eval board I received from Digi worked for a minute and then won't start. 

I tried to replace the part with the UCC28634/UCC28630 ,,, didn't work either (Both AC(120V/240V) and DC(90V to 330Vdc) ). 

Below are the screen shoots that I see. I am at my wits end to figure this out. I really like the chip but I have no idea what is going on inside as I don't have access to the digital system or the analog counter part (error amp, comp etc). 

Additionally, I see a large Q on the C7, L2 & C5 filter. Any reason for that or is that a design issue that TI missed ?

Also, how do I find for Control to Output Transfer Function Eval board (20 Ohm in series with R7 perhaps) ?

Vdd-pri gnd: Vdd wrt Primary GND

V6-4: Voltage across Lm (Transformer Pin6 wrt Pin4).

Further, I ordered another board.

Please help,

Thank you,

Anirudh

Hi Andy,

I use calculator to double check the parameter with your transformer spec , and you can refer the changing list as below.

maybe you can try to update it then power up again , and you can download the calculator at below link.

https://www.ti.com/lit/zip/sluc537

R7 : 24.9Kohm

R8 : 32Kohm

R16 : 0.8ohm

Thank you for your response. Can you please answer the following and hopefully soon:

Question already asked but not answered

1. I see a large Q on the C7, L2 & C5 filter. Any reason for that or is that a design issue that TI missed ?

2. How do I find for Control to Output Transfer Function Eval board (20 Ohm in series with R7 perhaps) ?

New Questions:

3. I did read the datasheet and I did calculated them and it doesn't work. My plant (Flyback converter) is fine. I connected a signal generator to establish that (while the controller chip was DNP).

4. The reference design for this chip on the webench asks for 2.5 mH for Lpri. datasheet say the range for Lpri is 200uH to 1.5mH. Can you explain the discrepancy ?

5. Since I have a wide input range, my Lm calculated according to the datasheet is greater than 1.5mH. Which based on my experience sounds right. In this case will this chip will not work for me ? 

6. I fixed my startup issue partially (Initial three pulses), the eval board I received had a broken zener diode (Fixed it). Now, I see a PWM trail but doesn't transition into steady state operation. 

7. I tried several different transformer (78 to 9, 100 to 10 and 200 to 10, and with EFD30/15/7 core N97), nothing worked. As the turns go up, the Lpri increases (depending on the airgap and turn ratio goes from 800uH to 13mH) as expected. My sense resistor is 0.2 Ohm. I do not see output voltage. Even if my turns are off by a little bit, I should see a different voltage (the chip would be blind to the secondary voltage). Of course, I tried replacing the chip with UCC28634s.

8. Why won't the UCC28630 work with DC input ? As long as the voltage is on the valid region it should work. Well, at least that is what I gleaned from the datasheet. 

Thank you,

Warm Regards!