Overvoltage and Voltage Spike Protection

Thread Starter

Mad Professor

Joined Apr 15, 2009
Good Day All.

I would like your help and advice with regardings to designing a overvoltage and voltage spike protection board for the power supply to a CNC control board.

The main parts I have to protect are the two voltage reg's and the stepper motor driver chips.

I have looked at some of the datasheets for the Absolute Maximum Rating.
L7812CV - 35 Volts Absolute Maximum Rating.
L7805CV - 35 Volts Absolute Maximum Rating.
TB6560AHQ - 40 Volts Absolute Maximum Rating.

This board is ment to be able to run upto 36volts, but by looking at the datasheets this is pushing it.

So can you please advice me where I should start?

Thanks for your time.

Best Regards.


Joined Oct 2, 2009
Look up "Transzorb", and "crowbar circuit".

You might think of using a "pre-regulator" ahead of the 5 and 12V regulators (i.e. run the stepper on the highest voltage, but drop the voltage ahead of the regulators).


Joined May 21, 2007
Which supply voltage do you have? 24V?

If this is the case, use 27V tranzil and the size 1500 W or 5000 W

BZW50-27 Farnell.com art no 1689194 could be used.