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I am trying to figure out the best way to implement an emergency shutoff for the H-bridge of a motor controller:

Image of Hbridge

My requirement is to turn off the 48V to the drain of the FET based off a signal which is either 28V (when the emergency signal is active and thus the MOSFET needs to be shut off) or 0V (When the emergency signal is not active and thus the MOSFET should be in regular operation.)

There will be two full H-bridges per motor and three motors per PBC. I anticipate current of about 10A per H-bridge. I would be happy to provide any other information to paint a picture of what I'm trying to design.

What is best way to design circuitry that will shut off the 48V to all three motors based off an input signal that is either 24V or 0V?

The emergency shutoff must be independent of the MOSFET controller or H-bridge gate, so we cannot turn off one of the MOSFETS or the H-bridge in general.

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    \$\begingroup\$ Why are you concentrating on turning the 48 volts off when you can turn-off just one MOSFET and disable your load. \$\endgroup\$
    – Andy aka
    Commented Nov 13, 2023 at 18:54
  • \$\begingroup\$ Turn your HB controller(s) off. \$\endgroup\$ Commented Nov 13, 2023 at 19:14
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    \$\begingroup\$ Can the emergency shutoff use a high-reliability relay to interrupt the +48V_SYS supply? \$\endgroup\$ Commented Nov 13, 2023 at 19:24
  • \$\begingroup\$ Yes it can use relays. I believe i will take this approach. thank you! \$\endgroup\$ Commented Nov 15, 2023 at 15:29

1 Answer 1

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What is best way to design circuitry that will shut off the 48V to all three motors based off an input signal that is either 24V or 0V?

Depends on what you want to avoid, if you think the h-bridge could fail and short out the VCC either a pmos fet on the high side or a nmos fet on the low side would be sufficent.

I would probably select a low side fet with a very low Rds-on.

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