# Circuit Protection to the current circuit

I have a basic circuit that uses 555 timer to generate PWM signal and the PWM signal turns the high side switch, SI1865DDL, on and off at certain frequency and duty cycle. The output from the high side switch goes to a camera which then takes photo. Both the high side switch and the 555 timer, are powered by a single power supply that outputs 5V, 1Amp max.

Power Supply:

Here is a block diagram I will use a IN4148 diode for reverse protection. I would also like to mention that I have turned the system on for an hours, and it worked fine. What sort of protection can I use on the output of the power supply to maintain at 5V 1Amp?

So, I was able to find a tvs diode that I believe fits my need: uClamp0871P. Can anyone please verify if this is a good tvs diode for a 5V power supply? I understand that it clamps at 15V which I am fine with it as it has low steady state power rating under 8V.

– user208862
Apr 23, 2021 at 22:46
• @MichalPodmanický Protection on the output of the power supply so that it can remain at 5V and not exceed 1Amp.
– Sam
Apr 23, 2021 at 23:15
• Are you trying to protect your circuit in case the power supply does something bad? If so, have you thought about a transzorb (zener diode on steroids) and a polyswitch (resettable fuse).
– qrk
Apr 24, 2021 at 2:03
• @qrk Yes, I want to protect my circuit in case the power supply goes bad. I have thought of adding a fuse but not sure what capacity of fuse should I buy. Selecting transorb is another monster that I haven't learned to do.
– Sam
Apr 24, 2021 at 2:09
• The 555, from memory, can tolerate > 18 V. The SI1865DDL works at up to 12 V and can tolerate 8 V on the logic input. It's not clear to me what your concern is. "... to maintain at 5 V, 1 amp ..." You can control the voltage or the current. You can't control both. Since your circuit needs 5 V it will determine the current drawn. The power supply is rated at 1000 mA. It will probably supply more but at some point the voltage will start to droop below 5 V. Apr 24, 2021 at 11:30