Over Current Protection

Question

So we have "Over Current Protection" part in Motor Control Workbench . but it seems it needs an external circuit on board to sense current , and there is 2 question here :

1- what circuit should I use and where should the output of that circuit be connected ( in "Over Current Protection" dialogue there is no place to choose a pin for over current detection .

2- why we should use an external extra circuit for current sensing when we already have three shunt on our MOSFETs ? Can we add just a simple if where we measure Ia or Ib and check if this value has been passed just stop anything ? ( I've already did it and it seems to work -But I know it should be a trigger to TIM break input to work properly - So is there any easy way to do this protection by just comparing Ia and Ib ? )

cedric H · Accepted Answer

Hello,As written by @rpip.1​ , It is always safer to have an hardware detection of an overcurrent.Depending of your power electronic, you can already have amplified current and overcurrent detection from your driver. In this case you just need to connect the overcurrent pin of your power board to the Timer break input ( configuration used in the IHM07).If you use internal Opamp, then you can also use internal comparator to do the detection by the STM32 itself ( it is faster to do the detection on the non amplified signal). Could you share your configuration ? It will allow me to provide a more accurate answer.RegardsCedric

rpip.1 · Answer

Of course you can compare Ia or Ib with max current in the program to stop anything. But by software, it has a delay to sample current, it's too slow to implement shut-down within a few us. So we often use a comparator to compare voltage on shunt res with a ref voltage to output an edge signal to TIM break input to stop all the output at once.

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