“ We could remove the DC-DC, replace the HV FETs with solid-state relays, and use a Hall Effect current sensor to detect the end of precharge. Everything would be isolated from HV, so we wouldn’t need an isolated 12V rail.
Or we could just add a forward-biased diode in series with the DC-DC input. ”

List:

Remove DC-DC

• It is not needed as we don’t need the isolated 12V rail

• Find out if every single thing for the 12V is removed or just some

  • What will replace ISO_12V and ISO_12V_SW

HV FET with solid-state relays

• Q1 and Q2 system to be entirely replaced with solid-state relays

  • https://www.homemade-circuits.com/solid-state-relay-ssr-circuit-using-mosfets/

  • One end from HV_IN

  • Other end to pre-charge

    • iso_latch_out might be removed?

• Part Search

  • https://www.digikey.ca/en/products/detail/panasonic-electric-works/AQY221R2MY/1964538

  • https://www.digikey.ca/en/products/detail/bright-toward-industrial-co-ltd/AA58F/14302559

  • https://www.digikey.ca/en/products/detail/panasonic-electric-works/AQV101AZ/646033

Hall Effect Current Sensor

• Remove entire middle section with Hall Effect Current Sensor

  • Must connect to IN+ and IN-

    • Unsure if AND gate and MOSFETs need to be changed

• Part search

  • https://www.digikey.ca/en/products/detail/allegro-microsystems/ACS756SCB-050B-PFF-T/5400760

  • https://www.digikey.ca/en/products/detail/lem-usa-inc/HO-8-NP-0000/4331974

Top Sheet Connections Changes:

• ISO_12V_SW

• IN+ (Stay)

• IN- (Stay)

• ISO_LATCH_OUT

• ISO_GND

• ISO_12V

Comments:

First

• With the relay circuit you sent, just make sure you understand it because I see it's for an AC load

• iso latch out as a signal controls Q1 and Q2 so you're right in that we won't need it, but you'll need some control signal for the relays

• For the relay part search, it looks like one of the models you sent has a load voltage rating of 40V, we need at least 150V. Also, I forget how much current will be running through it but check peak load current as well. We finish precharge before the capacitor voltage is at 150V so there will be current.

• Again for hall effect sensors just check your ratings. I think both the ones you listed are fine but double-check.

• One more thing, one of your current sensors takes a 5V supply. If you find you have a few components that need that you should probably find a regulator