Other Parts Discussed in Thread: LM5146, , LM5148-Q1
Tool/software:
Based on LM5146 Cycle-by-Cycle OCP protection, I set the Rlim such way to limit the current at 25A. with step change in load current from 20Ato 30A, it limits the current ant 30A for 1.86ms and then starts dropping the output voltage to zero and load current to zero as well. the whole action time was 4.75 ms!
Then It goes to hiccup mode with frequency of almost 10Hz until overcurrent situation goes away!
Operating points:
Vin=61V, Vout=30V, Iout=20A --> Step change: 20A to 26A &30A (Ilimit= 25A)
fsw=350kHz
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Over Current event: (I_step: 20A to 26A)
Hiccup Mode:
Recovery Mode: (load step goes to 20A), Vout got regulated again at 30V with 61V input voltage.
In datasheet it says that it will take 128 cycle until goes to hiccup mode and after that will take 8192 cycle until goes to OFF mode.
1- What is the cycle frequency? Is this the same with switching frequency or internal cycle is considered for counting?
Because with 350kHz switching frequency, 128 cycle is equal to (1/350khz)*128= 365us but in my case, it took 1.86 ms until load current goes to zero!!!!
2- What does mean many cycles in the bellow graph?
For how many cycles it will limit the duty cycle? is it the same with 8192 cycles mentioned in datasheet?
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3- In case of inrush current in load, this cycle-by-cycle wasn't able to catch the event and limit the load current!
How fast OCP protection can act in case of any inrush current in the load?
The test scenario is to connect 1.2mF load to the output of buck converter and see how current limiting (OCP) can protect the converter from inrush current up to 150A in 51us!
4- rather than having external OCP circuit after buck converter, what are the mitigation solution or possibility with LM5146 to protect circuit from inrush current and limit with Ilim/Rlim limits?
