35. NTC Selection & Design

Question.4

A 230VAC SMPS has an NTC inrush current limiter (R₂₅ = 10Ω) protecting the bridge rectifier.
The system is powered off and turned back on within 5 seconds.
On the second power-on, the bridge rectifier is damaged by inrush current.
The NTC is not defective. What went wrong?

NTC cannot handle two power-on events
NTC was still hot — low resistance, no inrush protection
Bridge rectifier was already weakened from first power-on
NTC acts slow- can't be able to protect sudden surge

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