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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.

Tim Williams
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Hasan alattar
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  • 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. – Stefan Wyss Oct 08 '18 at 19:30
  • 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 – Hasan alattar Oct 09 '18 at 05:53
  • Why don’t you simulate it? – winny Oct 09 '18 at 06:11
  • i've never used simulation, only the one altium provide for very simple circuits RC, LC, filters that already have spice model by default. – Hasan alattar Oct 09 '18 at 06:52
  • 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 – Hasan alattar Oct 09 '18 at 08:54

1 Answers1

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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.

Raviteja Cherukuri
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  • 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! – Tim Williams Jun 09 '22 at 15:20