esdinductormovprotectiontvs
I've seen power protection that uses:
Application Note: Transient Voltage Suppressors (TVS Diode)
Applications Overview
I didn't see any design guide for the inductor selection, so I choose 1 A inductor 4.7 µH. But doesn't that mean it will carry the surge current that TVS should clamp?
I'm not sure if 4.7 µH the right selection or not.
The app note is pretty clear in it's explanation that the ESD rating and the ESD voltage clamping level are the critical parameters.
If your product is going to be sold, most likely the market expectation will be that it will meet class 4 (8kV / 15kV), as the app note says.
You must choose a TVS that will not activate during 'normal' operation but prevent damage when the simulated ESD pulse is applied.
The only way to know for sure if your ESD solution is robust is to either have the IEC 61000-4-2 test done at a lab, or rent/buy an ESD tester and do the test yourself.
Varistors are variable resistors whose resistance will sharply drop when the applied voltage is higher than the threshold voltage.
In the given circuit the varistor is placed parallel to the mains voltage. I may be rated at 275V, like Littelfuse's V275LA10CP for a 230V supply. The datasheet says that it will draw 1mA at minimum 389V, so during normal operation the current will be negligible. If there's a voltage peak of minimum 710V on the mains however, the resistance will drop and the varistor will draw a considerable current (datasheet says up to 25A), so that the energy of the peak will be absorbed by the varistor, and that there's no damage to the circuit.
The energy a varistor can absorb is limited, mainly by its size, but in general they can only handle short peaks.
Selecting varistors is not easy. The curve isn't very sharp, and you can't expect to have zero leakage current at 300V and full clamping at 310V. There's a trade-off between leakage (1mA in the example) and the height of the clamping voltage (710V in the example).
Best Answer
Inductance value will be depends on the surge rise time and TVS clamping time. Current rating will depend on the MOV breakdown time and the energy of the targeted surge.