Hello everyone,

I have a circuit powered by a 9V adapter. I will use a voltage regulator. How can I adjust the power supply circuit to protect the PCB from overvoltage and overcurrent, such as fuses, diodes, capacitors etc.? Are there any examples?
And which step-down voltage regulator do you recommend?

Circuit ICs work with 5V & 3.3 V, and the maximum current drawn is 500mA.

 

To solidly protect against an over voltage one way is a series string of power diodes shunting the input, selected to the their total forward voltage drop is about ten volts. Then, as the supply increases above that the diodes will conduct and clamp the voltage at about ten volts. You will also need a series fuse for the power connection.

 

A standard LM317 Voltage-Regulator will not only keep the Voltage steady,
at any Voltage You choose,
it will also limit the Input-Current to a maximum of ~1.5-Amps.
With some extra components it will limit the Current to even lower levels.

Some other common Voltage-Regulators have lower Current-Limits built-in.

Your Power-Supply may be inherently Current-Limiting, just because it's a weak design.
.
.
.