Hi everyone,

I’m working on a system where I want to eliminate the conventional mechanical protection/switching components such as MCBs, DC contactors, and similar devices, and replace them with a fully electronic/solid-state solution.

The target electrical system is approximately:

- DC bus: 120 VDC

- Continuous current: up to 120 A

- Power: ~14.4 kW

- High inrush/capacitive loads may be present

- The system should be able to turn the load ON/OFF electronically

- Ideally it should provide bidirectional blocking when OFF

- Low conduction loss is important

My initial idea is a back-to-back N-channel MOSFET architecture, potentially using multiple MOSFETs in parallel to achieve the required current capability.

However, I don't want to simply make a MOSFET switch. The goal is to develop something that can potentially replace the functionality normally provided by MCBs + contactors + additional protection circuitry in one solid-state system.

I'm looking for advice on the overall architecture and, especially, real hardware/reference designs that have actually been built and tested.

Functions I'm trying to achieve

1. 120 VDC / 120 A continuous switching
2. ON/OFF control
3. Bidirectional blocking in the OFF state
4. Overcurrent protection
5. Fast short-circuit protection
6. Controlled turn-on / inrush-current limiting
7. Precharge for capacitive loads
8. Over-temperature protection
9. MOSFET gate protection / UVLO
10. Fault latching and safe shutdown
11. Detection of a MOSFET that has failed short
12. Current monitoring
13. Bus/load voltage monitoring
14. Possibly electronic trip characteristics similar to an MCB
15. Ability to reset/reconnect electronically after a fault, where safe
16. Controlled shutdown of the load
17. Protection against inductive/transient energy

Architecture I'm considering

Something along the lines of:

120 VDC → fuse/current sensing → precharge branch + main B2B MOSFET bank → load

For the main switch, I'm considering multiple high-voltage N-MOSFETs in parallel on each side of the back-to-back arrangement.

For example:

4–8 MOSFETs per direction/blocking stage, depending on the selected MOSFET and thermal requirements.

The gate drive would probably need a floating/isolated supply and dedicated gate driver, with individual gate resistors, gate-source protection, and hardware fault shutdown.

For protection, I'm considering having a fast hardware overcurrent/short-circuit path independent of the MCU, with the MCU handling slower functions such as monitoring, diagnostics, thermal management, precharge sequencing, etc.

What I'm particularly interested in

I'd really appreciate references or practical experience with:

- Solid-state replacement for DC contactors

- Solid-state replacement for DC circuit breakers / MCBs

- 100–150 V / ~100–150 A MOSFET circuit breakers

- Back-to-back MOSFET arrangements

- Parallel MOSFET current sharing

- Fast hardware short-circuit protection

- MOSFET SOA during a hard short circuit

- High-side N-MOSFET gate driving at ~120 V

- Precharge circuits for large capacitive loads

- High-current DC current sensing

- Thermal design for 10–15 kW solid-state switches

- Fault latching and electronic trip systems

- Detecting MOSFET failure/short circuit

- Protection against inductive loads and DC transients

- PCB layout techniques for 120 V / 120 A

Reference designs I've found so far

I've come across some useful designs from TI and Infineon, such as:

- Infineon REF_60100EDPS eDisconnect

- TI 48-V / 50-A bidirectional circuit breaker reference design

- TI TIDA-010208

- TI TPS48110-Q1 EVM

- TI TIDA-020065 Smart Fuse

These are very useful, although most are below my final voltage/current requirements.

I'm particularly interested in actual schematics, evaluation boards, application notes, or products that have implemented this concept, even if they're only 48 V / 50 A or similar. I can scale the power stage if the underlying protection and control architecture is appropriate.

I’m not necessarily looking for a single IC that handles 120 V / 120 A. I'm open to a discrete architecture using MOSFETs, gate drivers, current sensors, comparators, MCU, etc.

The bigger question is:

What would be a robust architecture for replacing the combination of a DC MCB + contactor + protection circuitry with a solid-state system at ~120 V / 120 A?

If you've designed something similar, I'd really appreciate any reference designs, schematics, application notes, papers, products, or lessons learned.

Also interested in hearing about approaches other than MOSFETs if there is a better solid-state technology for this voltage/current range.

Thanks!

 

You can proceed by studying TIDA-01168, REF_60100EDPS, and TIDA-020065 as the primary reference designs.

 

The problem is that you system does not fail safe. Its most common failure would be a MOSFET going short circuit, in which case the load is permanently energised and you cannot switch it off.
For 120V DC, nothing beats a fuse, and make sure that the fuse is rated to break the prospective fault current at DC. Many DC-rated MCBs are only rated at 80V.