Attention " OPTIKON "--Current Limiter Circuit

[chinngap]

Thanks for the help, I understand your point, but I cant quite get the point of connecting the collector of the small transistor to the base of the power transistor. If you have the diagram to explain the thing, it will be the best. Thanks a lot. Really appreciate your effort here. Cheers!

 

[Nigel Goodwin]

Thanks for the help, I understand your point, but I cant quite get the point of connecting the collector of the small transistor to the base of the power transistor. If you have the diagram to explain the thing, it will be the best. Thanks a lot. Really appreciate your effort here. Cheers!

Please post replies in the same thread, it's just confusing starting a second thread on the same subject!.

 

[Optikon]

Thanks for the help, I understand your point, but I cant quite get the point of connecting the collector of the small transistor to the base of the power transistor. If you have the diagram to explain the thing, it will be the best. Thanks a lot. Really appreciate your effort here. Cheers!

This method is crude but easy to implement.
Q1 when turned on by the overload condition, "steals" base current from the power transistor thus turning it off. Take care not to dissipate too much power in Q1 or in Rsense. You will have to use values and components available to you but this can work nicely for a several amp current limit. Also, take care to avoid secondary breakdown of power transistor while in current limit. You may want to provide an opto-coupler output to your controller to remove the power if over-current is detected.
This is crude so watch the fine details.