Protection circuit

[sass]

Hi.
I need simple protection diagram for 12V car 1A circuit. There are a lot of diagrams on the web, but all are without values. I drew a diagram with one capacitor, one dual TVS, one diode and one single TVS. What do you think of that diagram? Are those parts correct or can those be replaced with better ones? Is there something missing from the diagram or is it possible to make it simpler? Are the voltages correct?
**broken link removed**

 

[Menticol]

It's important to explain what is the condition that you would like to prevent: Undervoltage? Overvoltage? Ripple? Unexpected Shutdown?

 

[KeepItSimpleStupid]

I would add a revered biased diode across he cap. hr faster the better. 200 PIV to 400 PIV as suggested.

The 0.1 uF should be ceramic and it tries to damp the short spikes.

The Bidirectional 30 V TVS is a first line of defense, but one should protect to a lower negative voltage.

The Schottky diode is your basic low voltage drop reverse polarity protection.

The 18V TVS gets the protection about where you want it and it's OK with say an alternator overcharging.

A more complex device is here: https://www.linear.com/product/LTC4364-1

Here https://www.google.com/url?sa=t&rct...=c6MA21WzMSr19lgOom6h-g&bvm=bv.76247554,d.aWw is a good read.

It also depends on how much you value the device your protecting. Those components don't come cheap. You do not have to get the exact ones. Thru-hole versions seem to be disappearing.

The suppression referenced doesn't do an excellent job for negative voltages which can exceed 200 V. 400 PRV components would be slightly better than 200 V PRV.

 

[sass]

I want to protect from dump, reverse battery and spikes. If I put the diode to the beginning then I should add 2A fuse, otherwise with reverse battery I can see smoke. Overcharging is not a problem, cause the diagram has voltage regulators NCV4275 (input voltage up to +45V) and NCV8774 (input voltage up to +40V). Rest of the voltages are not so critical and are solved with resistors/zeners.
Doesn't bidirectional TVS protect from negative spikes? I chose it to protect positive and negative spikes.
I added diode for reverse battery and 18V TVS is for secondary protection.

I can't use more complex devices for protection as they need more space and I have very limited space in my project.
If I had more space I would use triac, it would give nice protection. Even RBO40-40G is too big, cause I can only use 3 mm in height.
The details I chose are all available in Farnell and the SMD parts cost 1,2 EUR and that is only a small portion of the total cost of the project.

 

[KeepItSimpleStupid]

I think your OK with the Schottky diode in there. The bidirectional will protect to -30 V and that should not exceed the 40 V PRV of the Schottky diode. I was thinking more of clamping the negative voltage to -.0.6 or lower, but probably your way is better.

 

[Rocker_BR]

Good information here https://www.vishay.com/docs/49337/49337.pdf