Patent ID: 8189312

Claim:
A circuit arrangement ( 10 ) for detecting undervoltage in an energy source ( 12 ), comprising: a transistor switch ( 48 ); and at least one further switch means ( 30 ), wherein the transistor switch ( 48 ) and the further switch means are of low impedance in an operating state of the circuit arrangement ( 10 ), and the transistor switch ( 48 ) blocks the further switch means ( 30 ) for interrupting the voltage supply if a supply voltage (U) of the energy source ( 12 ) is below a defined voltage value (U s ), wherein the defined voltage value (U s ) is proportional to the sum of a Zener voltage (U z ) of a Zener diode ( 44 ) and a threshold voltage (U BE ) of the transistor switch ( 48 ), wherein said transistor switch ( 48 ) and said Zener diode ( 44 ) are connected downstream from said further switch means ( 30 ) with respect to said energy source ( 12 ).