buck converters boost converters or buck boost converters as ell as to other types of current limited types of dc to dc converters as e g ldo converters a typical application of the present invention is related to non regulated power sources that have strict maximum current limitations i e a current drawn from them must not exceed a specified value fig1 a illustrates a block diagram of the basic functions of the present invention provided are two power sources 1 and 2 e g usb and firewire it should be noted that more than two power sources could also be used with the present invention furthermore fig1 a shows a multiplexing switching unit 3 having two main switches 4 and 5 wherein each main switch is connected to a power source and to an input current sensing unit 6 only one power source 1 or 2 is exclusively connected via multiplexing main switches 4 or 5 and via a corresponding input current sensing unit 6 to a dc to dc converter 7 having an input port 9 and an output port 8 a connection 11 is provided between the current sensing units 6 and the converter 7 to limit the load current an important feature of the invention is that a input current sensing functionality 6 is integrated in the power multiplexing block 3 for different input applications thus providing a smoother current sensing than in the switching pass device of the dc to dc converter 7 which is burdened with a lot of noise in case the current through an active power.