InnoSwitch3-AQ spreadsheet

Posted by: hamza.rhoudda@… on 12/21/2021

Hi,

I'm working on a DC-DC 30W converter and i'm interested in the INN3977CQ Flyback switcher. The input of the converter i'm working on can go to 900V so i will need to use the stackfet solution.

I have some quetions about the Pixls spreadsheet :

1) Is there a way to make the spreadsheet take into account the stackfet solution ? cause its giving me a warning in the peak drain voltage and i don't know if i can trust the results or no whe there is a warning !?

2) In the worst case electrical parameters part its giving me a duty cycle of 0.20, and its not corresponding to the on time that it giving me below (about 27%) ? Also that duty cycle is it for the maximum input or low input ? what is the worst case for you in your spreadsheet ?

Also, can you share the Pixels spreadsheet that you used for the eval board DER-859Q cause i'm not getting the same values and i need to know what i'am doing wrong ?

Thank you for your help,

Best regards,

Comments

Hi,

Can you share to met the PI XLS that you created so that we can check why these warnings occur on your design? I need to know the specific values in the PI XLS so that I can help you with your concern. Thanks.

Hi,

Thank you for your reply. You will find attached the PIXLS file that I created.

I have a warning at the line 82 VDRAIN, which is normal cause the switch max voltage is 750V and i have 1040V, but i'm gonna use the stackfet solution as I said before.

In the line 91 I have a 0.215 duty cycle but in the line 92 i have an ON time that corresponds to 0.308 !!

At the part SET-POINT ANALYSIS (line 176) when I put a DC voltage of 900V I have a 0.06 duty cycle, what is the parameter to edit to increase that duty cycle cause 6% is very low ?

Can you share the PIXLS that you created for the evaluation board ?

Thanks

Attachment	Size
DCDC InnoSwitch3-AQ Design1.pixls	64.5 KB

Hi,

I got your design.

1. Currently, we are not yet accounting for the stackfet solution that's why we're having a warning. Because of this, you can choose to disregard the warning in line 82, but all the other calculated parameters will remain the same.

2. For the worst case parameters, the duty cycle shown is the maximum duty cycle, while the ON time is the minimum on time that's why they're not corresponding. Worst case maximum duty cycle happens at low input, while minimum ON time happens at high input.

The 0.06 parameter duty corresponds do 1.32 us ON time, which is still above 575 ns to trigger SOA protection.

Are you using any design evaluation board and may I know its design number?

Hi,

Thank you for your help.

I think that we gonna use the DER-859Q evaluation board.

Thanks again !