UCC28910: Non isolated implementation: PMP 4443

Hi Adelson,

Thanks for your interest in TI's product.

Can you share more information of your design specifications and test conditions , Such as input range , your target Brown in/out voltage ?

And thank you captured so many waveforms , can you note the test conditions such as what is the input voltage and load condition.
Take the first waveform for example . : 1). what mean of DC ? DC coupling?
2), Please mark the maximum and minimum of voltage of VS --- add measurement
3). if you capture the switching waveform , mark the frequency .
4) If you have more probe , you can capture more than two channel in same waveform
Such as VDD and Vdrain

You can try to decrease the divider resistors on VS pin , 470Kohm means brown-in voltage is 98.7Vdc.

Thanks.

Hi Jaden,

Thanks for your reply.

So, my brown-in voltage is approximately 100Vdc. i didnt understand very well what is this voltage, in PMP 4443 is not explicity (or i did not understand) what it is.

My brown-out voltage is approximately 40Vdc.

I need an output 5V @ 200mA

about your questions:

1) Yes, DC means DC coupling.

2) 3) 4) i will do it in the next waveforms, thanks for hint!

I did some tests days ago changing the value of R4 and R7 and the system started to work. I found the limit that R4 = R7 give output approximately 8Vdc/150mA and i cant below this voltage (5V for my application).

 when i use R7> R4 the power supply doesnt work, the VDD voltage goes to 10Vdc and the restart in 5Vdc. I think that the output voltage is responsible for VDD supply, isnt?

Is there any way to get 5V?

Regards,

Adelson

Hi Adelson,

Brown-in voltage means until the input voltage exceed this voltage , The controller IC will start to operation ,similar to UVLO.
That is why I asked you what is your input voltage when you testing.


R4 will decide the start-up voltage : V brown-in = Ivsl(run) * R4. Where Ivsl(run)=215uA,
R4 and R7 will decide the output regulation voltage : Vo =Vvsr *(R4+R7)/R7 , where Vvsr = 4.05V

So if you set up R4=R7 , the Vout should be 8.1V , that is make sense.

you can try R4 = 234Kohm , R7= 1M , the Brown-in voltage is 50V , and Vo is 5V.


Thanks.

Hi Adelson,

I Ignored that the VDD were supplied by Vout , you are right .
That is means VDD always hiccup due to Vout was lower than VDD_turn_off . too late in my time .

Tomorrow I will check if other solution for you.
Thanks.

Hi,

Any answer?