Is there a way of dimensioning the zener diode minimum power needed?

     Mark Jordan


On 12-Dec-13 03:14, David VanHorn wrote:
> There is always a trade off. Fast snubbing of the coils causes
> significantly slower contact opening, which can cause arcing and welding.
> Snubbing with a zener across the transistor improves the turn off time by
> as much as 3x, and with proper selection of the zener the transistors are
> safe.  I use this extensively to protect our relay drivers and we make a
> lot of devices with relays.
>
> If there is enough capacitance in the wiring to the relays, there may be
> fast current spikes during turn on.  I would be surprised if there was
> enough cable involved.
>
> The chips died, something killed them.

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