Hi John,

In physical design environment, for overcurrent protection you can use eFuse ( of desired rating) in series of your load. Many make eFuse are available. If you BOM cost and layout permits then you can use them.

Well most of DC-DC converter switches has got overcurrent protection circuitry built inside the package. These sense the load current directly or indirectly and based on that if threshold limit is reached then IC goes in shutdown mode. No need to add any additional circuitry at load side. Wise thing would be to select only that switching IC which has got inbuilt overcurrent protection.

Still if you want to use then below is one very basic regulator circuit with over current protection which you can use after your secondary output voltage i.e. in place of any LDO.

Basically R3 would be your desired load. If it somehow it gets shorted ( overcurrent mode) then more current will flow through R2 hence making Q2 turn ON (Vbe>0.6Volts), which will turn OFF Q1 since most of the the base current will go to collector of Q2.

Hence eventually Q1 will turn OFF and your circuit will gets protected.

Here value of R2 is very crucial and will determine the threshold of your overcurrent circuit. Also consider VBE drop of Q1 and D1 Zener breakdown voltage while setting output voltage at R3. If there are no power budget constraints then you can use this circuit as losses are more in this circuit.

Hope it helps

Very useful for me.. 

penalty kick online
 

Great design. Avatar Game is a game for everyone. Conquer it.

One of the simplest and most common methods is to add a series fuse to the load. The fuse will blow and break the circuit if the current exceeds the rated value, providing four colors protection. Fuses come in many different currents and can be easily replaced once blown.

great issue