I understand the use of the Zener but what I don't understand is one topology uses two components, but why can't the other topology be used ?
simulate this circuit – Schematic created using CircuitLab
The circuit on the left uses two components (D1 and D2), whereas the circuit on the right only uses one (D3).
I can't really see a difference between the two, other than that the left might decay a bit faster because of of the higher clamp voltage, but aside from that, I would imagine they operate the same.
So why do most schematics I've seen with regards to coil suppression use a series diode zener pair ? There must be something I am not seeing or understanding.
Best Answer
Not a lot of difference if the zener diode is specified as higher voltage by the supply voltage in the second case. The current loops are different so there might be some difference in the EMI but probably not significant in most cases.