Hi Team
Here customer are evaluating BQ24780s in medical power charging base, now debugging encountered some problems, need to consult:
The chip input voltage is 19v, the output voltage is 14.5V, and the maximum current is 6A.
Problem: the upper MOSFET is easy to be broken down, and there is a short circuit between DS.
Analysis: because the MOS temperature is very high, in two or three minutes, it can reach more than 110 degrees, which is caused by overheating MOS breakdown.
Yellow: upper MOS GS waveform, blue: lower MOS GS waveform, green: MOS current
From the waveform, it can be concluded that the upper and lower MOS open cross shoot through, and the upper and lower MOS turn on, resulting in a direct short circuit, so the MOS will heat and breakdown.
Questions:
1. For this chip, help to recommend the use of MOS selection?
2. It can be seen from the picture that no matter how faster turning off the MOS, there will still be crossover. Can this chip increase the dead time to avoid the shoot through?
3. Whether there is a better way to solve it?
Best Regards
Gene
