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Do you think for a few nanoseconds, the damping resistor actually sees the full 530 Volts in the "reverse recovery" time of the diode?Have been using US1M in similar circuits with 1R mini-Melf series resistor, Udc = 650V. Mini-Melf Pulse rating is slightly higher than 1206 but almost comparable.
Sorry i dont know, the above is the only info the Boss lets me see.-And He only told me this to put into context the diode reverse recovery test circuit that he's asked me to build.By the way, what's your sequence for initial bootstrap precharge? It might play a role if the resistor already fails during start-up.
...thanks for this observation, i will take it from this that due to the fact that this resistor didnt get hot that it is actually overvoltage that was causing the resistor to fail.I don't know how much transient voltage does the series resistor see. I can just confirm that in my design, we had no noticeable heating of the series resistor (according to IR camera).
treez,
- Have you tested reducing R1 to 1R?
- What is the voltage rating and type of C2?
- What is the gate charge of MOSFET M1?
- What is the pwm frequency?
At first sight, no, but do you agree..if an overly high dv/dt makes the ADuM4223 switch when it shouldn't, then the bootstrap diode may get "reverse dv/dt'd" when it is conducting near its maximum current, which could cause a bad reverse recovery transient...you agree?Isolator transient rating is irrelevant for the bootstrap resistor at first sight.
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