LM5170EVM-BIDIR: LM5170-EVM-BIDIR-DUTY RATIO

Hi Muhammad,

Please do not open another thread with the same question, while the other thread is still open.

There is no testing point on the board from which you can get a signal that points to the duty cycle, it has to be measured from the SW node.

Hope this helps.

BR,

Haroon

Thanks for your reply,

But SW node gives PWM not the duty cycle right?

Hi Muhammad,

Yes it is PWM, but there is no signal named duty cycle, it is the ratio of the on time and off time of a device, and that could be calculated or measured from the SW nodes on time and off time.

Hope this helps.

BR,

Haroon

Thank you, but I think you are not getting my point, I understand I can calculate duty cycle from Ton and Toff of the switch, but I need this as a physical signal and I want to give it to my observer model which will take the values of this duty cycle. So how could be possible with this board?

Hi Muhammad,

I understand what you are trying to say, but that is not possible in this case, as far as I know.

BR,

Haroon

Thanks for the reply,

How we can made it possible? there would be some other way I mean to use another external driver circuot, i do not know how it will work but that's what it came in my mind.

Hi Muhammad,

I am not sure how to get this done to be honest. I have not been part of a project similar to yours so I wish you the very best to find a way to do this.

BR,

Haroon

Thanks for your reply,

Any other expert who worked on this project, maybe they give me some useful advise which would work for me.

Hi Salman,

You can calculate the duty cycle from SW, HO or LO waveform. 

Please describe what kind of signal you want to have? You want to use external gate driver but not LM5170 built-in gate driver?

BR

Feng Ji

Hi Feng Ji

Thanks for your reply, I want to take the duty cycle signal which is input to the PWM comparator and output of the CA gm (current loop compensation). The waveform from the LO and SW are PWM square wave signals and I need the duty cycle (analog) signal. I want to feed this duty cycle signal to my observer model.

So, I checked possibilities how to take that signal because there is no such testpoint or node in the board, or is there any possibility to take it and measure it?

Hi Salman,

COMP is the input to the PWM comparator and output of the CA gm (current loop compensation).

Duty cycle equals to (VCOMP-1V)/VRAMP in buck mode. So, you may take comp1 and comp2 Pin for duty clyle.

Feng Ji

Thanks Feng Ji

I am using as Boost mode, so I also looked for the COMP pin but in board there is no node for the COMP pin too from where I can take the signal.

Thanks Feng Ji

Yes, I have checked this before but the pins are too small and the space is very tight to work, might have a chance of short circuit but I think this is the only option I have now I guess.