8 Key Consideration in Designing SC Protection Circuit

• Reduce peak short circuit current
  • Peak current depends on multiple factors: time to detect the SC event, module type, and the system voltage. As the module type and system voltage are fixed, the only way to optimize is to implement a faster detection circuit to identify the failure event faster.

Some of the key considerations to detect the failure faster:

• Optimum smaller blanking capacitor ~30-100pF (balance between false triggering to right protection)
• Higher blanking cap charge current (0.5mA-2mA)
• Optimum low V_SC detection threshold based on the power module
• Reduce shutdown time and energy
  • Reducing shutdown energy depends on the peak current during the SC event and turn-off di/dt. Reducing peak current was explained in the previous passage and the only other parameter to tweak is turn-off di/dt. Though faster turn-off will help to reduce the shutdown time, it is not recommended due to possible overshoot across the power module due to very high di/dt during the SC event. So it is ideal to balance the turn-off di/dt and overshoot specific to the power module.
    • Faster turn-off (higher overshoot, but less shutdown energy), slower turn-off (lower overshoot, but higher shutdown energy)
    • Need to balance between overshoot vs shutdown energy