UCC28950: Ucc28950

Dear Sonal,

Please guide how can I use UCC21520 in PMP8740?

my email id is engg5@adordigatron.com

Thanks,

Anjana

Hello Anjana,

If the Shim Inductance value is negative then you won't need an additional shim inductance because there is enough energy available to drive the ZVS transition.  I will recommend leaving the cell with 0.5-1uH which is a negligible value (similar to what is done in the schematic)  this cell should NOT be left zero. 

The 4uH leakage inductance value sounds a reasonable assumption too.

The application of the isolated gate driver is relatively simple and straightforward. Please refer to the application guide and user guides attached below, this will help you to integrate UCC21520 with the design.

I hope this information helps you.

Regards,

Sonal

Hello Anjana,

We can work the Fsw and D values backward given the Rt value using equations: 11 and 8/9

1. Fsw = 100kHz for Rt= 60.4kHz; The switching frequency of the power stage is twice the Fsw of the controller.

2. For Rtmin=13K, Tmin=77nsec, this will give you Dtyp= 0.77

I hope this answers your question.

Regards,

Sonal

Hi Sonal,

Greetings!

Please explain how do you calculate values for L2 and Cin in PMP8740. L2 calculation is not given anywhere and if i calculate Cin as per application notes and datasheet of UCC28950 it gives different value. Please help.

Anjana 

Hello Anjana,

I have written back to the designer of the PMP8740, and I will get back to you as soon as I hear from him.

PS: It can take several days before he replies.

Regards,

Sonal

hello, 

can you share dc-dc main transformer details like no of turns of primary and secondary and wire gauge of both windings, so that i can compare with my design. 

thanks,

anjana

Hello,

In PMP8740

1) why Iout signal used in voltage loop? Iout used in current loop as well as in voltage loop.

2) after going through white paper i have one doubt why series and parallel combination is used between output connector and Vout at output capacitor?

Anjana

Plz reply

8053.2kW parallelable power supply module.pdfHello Anjana,

I have attached a paper that the designer of the product wrote, I would refer you to pages 10 and 11 for this case, the paper talks in depth about the inductor and capacitor calculations. 

Regarding your previous questions: can you please be more specific about the white paper you are referring to.

As far as the transformer information: I will trust the calculator for the turns ratio calculations, we can not provide you with transformer winding details.

Regards,

Sonal

Hello Anjana,

1.  the Iout signal is used in the current loop alongside the voltage loop only to set the current limit, we cannot use the primary current signal for CI regulation because the primary current is a function of the input voltage and there is no fixed relation between primary and secondary current. This is why we need additional current error amplifier to set a demand level (EA+) for the control loop and so regulate the output current
2. For your second question, I do not understand it, can you please refer me to a text or a figure in the paper where you saw this. I might be wrong but I think you are talking about the parallel capacitors connected close to the output connector in figure 14, we use several parallel capacitors in order to better filter the output signal and eliminate the AC ripple.

Regards,

Sonal

thanks for your reply .

I am refering " 2kW parallelable power supply module.pdf "

1)I am clear about  fig 29 . voltage and current feedback to the controller, but please explain, in PMP8740 why this Iout signal used here in this voltage loop?

2) for your second question: sorry it was my mistake, my question was in PMP8740 design what is necessity of  Q12, Q17, Q25-Q31, Q20 Mosfets in Output path? if I am not wrong,  those all mosfets should be ON in healthy condition , also at start u-controller first check for reverse connection of battery to output terminal , if it is OK then turns On those MOSfets.

Thanks,

Anjana