This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC21755-Q1: Gate Driver Desaturation Protection Flow

Part Number: UCC21755-Q1

Nice to meet you. I am writing this because I want to know about the Gate Driver Desaturation Protection Flow.

From what I understand, firstly in the Normal Operating situation, IGBT turns on -> Vce goes low -> DHV turns on -> the internal current source does not get delivered to Cblank but flows through the upper path (resistor and diode), so Cblank does not get charged enough(under Vdesat). 

--> The voltage of the Desat Pin is expected to be Vce + 0.7V.

And in the Short Circuit situation, Vce goes high -> DHV is turned on, so the Desat Pin voltage increases (Vce + 0.7V) -> When the Desat Pin voltage reaches Vdesat, the FLT signal is output.

I would appreciate it if you could let me know if there are any errors or points to be corrected in the Signal Flow I understood.

 

  • Hi DongHun Jeong,

    Thanks for your interest on UCC21755Q1 device.

    Your understanding is mostly right.

    Just a small correction, During SC condition, DHV diode will be turned off as VCE is higher (and hence reverse biased). So the DESAT current source will charge the Cblk capacitor and once it reaches > Desat threshold, it will trigger DESAT FLT.

    It is also explained in the following FAQ as well: FAQ Link