I'm still busy with my DMX splitter (soldered everything), however, I made a mistake with my TVS protection diode. I put it in series with 220 V AC, and nothing happens (no current flows).

I expect I have to put this diode between the two AC wires, but before I mess up with 220 V AC I rather hear some feedback.

What I have now is:


simulate this circuit – Schematic created using CircuitLab

(I could not find all symbols, so I misused a few):

V1: 220 V AC (Dutch power socket) F1: Now fast blow, later slow blow 0.25 A F2: Resetable temperature fuse, 73 degrees D1: Bidirectional 440 V TVS resetable diode Load: 5 x 600 mA 5V AC/DC converters

I expect I need to use the following circuit:


simulate this circuit

Can this be confirmed?

Also, does the order of F1, F2 and D1 matter?

  • 1
    \$\begingroup\$ This is the correct way to use a TVS diode, yes. The fuses are probably best put on the live, since that way you can avoid having your ground planes live at mains voltage. \$\endgroup\$
    – Hearth
    Commented Nov 5, 2018 at 22:55
  • 1
    \$\begingroup\$ @Felthry Putting the fuses on the live side is a good practice, but these Schuko plugs are non-polarized. \$\endgroup\$
    – Phil G
    Commented Nov 5, 2018 at 23:02
  • \$\begingroup\$ I'm not using earth, so the two wires are both 'live' (AC). \$\endgroup\$ Commented Nov 5, 2018 at 23:03
  • 1
    \$\begingroup\$ @MichelKeijzers One of them will be neutral, but as Phil pointed out you can't know which, since the plug is non-polarized. (which I wasn't aware of) \$\endgroup\$
    – Hearth
    Commented Nov 5, 2018 at 23:08
  • \$\begingroup\$ @Felthry Ok ... I made the circuit accordingly and it works now (meaning, I have voltage on the +/- on the DC converters). Thanks. \$\endgroup\$ Commented Nov 5, 2018 at 23:55

1 Answer 1


Your second circuit is right. The bidirectional suppressors are really two diodes back to back so that one has to break down and the other forward conducts to pass current during an overvoltage.

The order of the fuses doesn't matter.


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