How to i go about building a solid state Dc circuit breaker

[needs to learn]

I want to use a mosfet as my solid state device, the mosfet purpose is to interrupt the circuit to protect my load from being damaged.
I have somewhat designed it, however it isn't working the way i want it to.

please help, please

 

[Mark R]

Need schematics and basic information such as whether you are going to be using high or low side switching.

We also need to know the voltage range, and whether isolated power supplies are available for the MOSFET driver, or will you be able to use isolated DC-DC converters to power the MOSFETs.

Similarly, do you need to provide snubbing on the gate, and do you need to reinforce the body diode against parasitic/device inductance?

 

[sm625]

Why not just use a TVS diode? Why does it need to be a mosfet? And, most importantly, does it have to be only a mosfet, or can it be a pair of mosfets, resistors, diodes, etc?

Anyway, if you want it to interrupt the circuit you have to decide which of two ways you want to do this:

1. By breaking the circuit in series with the load, ie set the mosfet to be "normally closed" and open it during a fault condition which removes power to the load.

2. By shorting the load in the event of a fault, ie set the mosfet to be "normally open" and close it during a fault condition which places a short in parallel with the load.

Option 2 obviously requires a circuit breaker or resettable fuse further up the circuit since it is creating a short circuit condition. This sounds scarier but it is simpler and faster than option 1.

Once you decide on which route you wanna take, it is pretty simple to trigger the mosfet. You can use a TVS in series with a resistor and place the two components across your input power. When it surges past the limit of the TVS, it will create a voltage drop across the resistor which can be used to turn the mosfet ON. That can be used to short your load. Or, you would take the output in series with a resistor so that when this first mosfet turns ON, it turns the 2nd one off. Your load needs to be in series with the 2nd mosfet.

 

[piasabird]

Cant you just use a UPS System?

Well if you use a dedicated circuit for your power you can limit how the power comes from the mains. I could see a problem if you live an area with a lot of brown outs or if the power fluctuates all the time.

You might post this in Highly Technical.

The idea is main power charges batteries, Inverter converts battery bank to 110/120.