Need help with a voltage clamping circuit

I need a circuit to prevent voltages above 24VDC from getting to a component. I am supplying it with 12VDC and simply want to make sure that in the event of a surge or blown fuse, the voltage does not exceed 24VDC.

I did some online searching, and found a circuit on this site that might fit my needs, but it has about 15 components in the circuit. Can this circuit be quite simple? I thought the appropriate Zener in parallel with the load would be sufficient, but it looks like I am wrong.

The 12VDC is coming from an AC-DC power supply, and the load is not supposed to draw any more than ~ 3A.

Thanks in advance for any help provided.

A zener would work or if you're using a fuse a crowbar would work.

SCR Overvoltage Crowbar :: Radio-Electronics.Com
**broken link removed**

Or use an MOV. What current/power/energy levels are you working at?

Thanks for the replies.

For that crowbar circuit, I take it the load would be to the right and in parallel with the SCR, yes? How would I determine what size resistor and capacitor to use?

The power levels are between 11 watts and 17 watts, with currents for the load ranging between 0.5 amps and 1.5 amps.

I have a 12VDC supply powering the unit, but had a couple of times where the voltage likely spiked (I wasn't monitoring it) due to a blown fuse, and when that fuse blew, it cut off the power to the 12VDC supply.

Ankulake said:

Thanks for the replies.

For that crowbar circuit, I take it the load would be to the right and in parallel with the SCR, yes? How would I determine what size resistor and capacitor to use?

The power levels are between 11 watts and 17 watts, with currents for the load ranging between 0.5 amps and 1.5 amps.

I have a 12VDC supply powering the unit, but had a couple of times where the voltage likely spiked (I wasn't monitoring it) due to a blown fuse, and when that fuse blew, it cut off the power to the 12VDC supply.

Click to expand...

To exceed the I-squared-T rating of a fuse, that spike must have had quite a bit of joules in it.

If your supply can sink current, fastening the cathode of a diode to the + terminal will provide you with a hard clamp at ~13v at the anode.
If your supply has current to spare and won't sink current, shunt it with a resistor so it will sink current and then use the diode.