|
Over-Voltage Protector ( OVP ) for 13.8V supply
One of my clients recently sent me a K2
for repair after it had been hit with over voltage thanks to a defective power supply:
it needed extensive repair. And that got me thinking of how one might avoid such
an event ...
Most modern supplies have over-voltage protection built in. If the voltage goes
above some set limit, say 16V, then an SCR fires and drops a dead short across the
DC line; this short blows an in-line fuse or folds-back the power supply to 0V output.
The circuit is known as a crowbar.
This OVP project provides the over-voltage protection for an 8A or so power supply.
If a huge current is available, from a gel-cell battery for example, DO NOT
use this crowbar circuit without an in-line fuse. The OVP can handle high current
for an instant only. If it crowbars an 8A supply, the SCR can handle the current,
but heat has to go somewhere: if the OVP trips, turn off the power right away.
I set mine to trip around 16V. If something goes wrong, it will foldback my supply.
Parts List
OVP-12 by Power-One (6.4-33VDC, 8A cont, 12A interm). Digi-Key 179-2057-ND
Project Enclosure. Radio Shack 270-1801
Power Jack. Radio Shack 274-1565
Zip cord, 16 gauge
Power Plug. Standard Elecraft part.
|