I've seen power protection that uses:

  • MOV (metal-oxide varistor)
  • Inductor
  • TVS diode

Application Note: Transient Voltage Suppressors (TVS Diode)
Applications Overview

Combined MOV Varistor and TVS Diode Protection Scenarios

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?

Input protection circuit in implementation Inductor NR series S type ratings

I'm not sure if 4.7 µH the right selection or not.

  • \$\begingroup\$ I do not see any reason for placing an inductor between the protective elements. If used, it should be placed after the TVS diode so that the diode can do it’s job. \$\endgroup\$ Oct 8, 2018 at 19:30
  • \$\begingroup\$ the first picture is not mine, as much as i understand, the inductor is there to delay surge current from TVS diode so the varistor takes most of the power of that surge. i dont know if its effective or not that what comes in my mind \$\endgroup\$ Oct 9, 2018 at 5:53
  • \$\begingroup\$ Why don’t you simulate it? \$\endgroup\$
    – winny
    Oct 9, 2018 at 6:11
  • \$\begingroup\$ i've never used simulation, only the one altium provide for very simple circuits RC, LC, filters that already have spice model by default. \$\endgroup\$ Oct 9, 2018 at 6:52
  • \$\begingroup\$ i did use LT spice today, it just doesnt give what i should do, good to see that 8kV voltage gets shunted by the varistor and zener diode but it need much more study of spice simulation i guess to simulate the real component and i guess current and voltage should be measured \$\endgroup\$ Oct 9, 2018 at 8:54

1 Answer 1


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.

  • \$\begingroup\$ As well as for nominal load, and the surge waveform: is this for IEC 61000-4-5 and if so then what level; or say, automotive load dump? The latter is likely to fuse a few-ampere inductor! \$\endgroup\$ Jun 9, 2022 at 15:20

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