US Patent 7639468 Circuit for load current measurement, limitation and switching

There is described a circuit for measuring, limiting and switching a load current on a load. To achieve a circuit of this type with a high degree of accuracy in the current measurement and with a low dispersion range, it is proposed that a measurement current is generated through a current mirror connected between a first supply line and a load, said measurement current being routed through a measuring resistor and resulting in a measurement voltage which is used for evaluation purposes hereupon. A switching transistor, to which a switching voltage can be applied by way of a resistor, is used to switch the load in a currentless fashion. A limitation of the load current is herewith also achieved by means of the switching transistor and an additional transistor in that when the load current is increased by means of the additional transistor, the voltage at the control electrode of the switching transistor is reduced until a balanced condition is set with a predefinable current value.