If the transient negative pressure of VSW is larger, VB will also generate negative pressure transiently, D1 will be turned on, and a large forward current will flow, which will be damaged due to overpower. Similarly, in order to improve the power of ESD protection, if D1 adopts The SCR thyristor structure also has a latch-up effect under a large working current, which causes the system to not work normally, or the output logic is disordered, resulting in a short circuit in the upper and lower tubes.
In order to reduce the negative voltage spikes at the switching node, in addition to minimizing the parasitic inductance of the loop on the PCB layout, the following methods can be used:
Reduce the turn-off speed of the upper tube, reduce the di/dt, and reduce the peak of the negative pressure, thereby reducing the negative pressure current. The turn-off speed of the upper tube is reduced, and the turn-off loss of the upper tube will increase. Therefore, some compromises need to be made between the two.