Patent ID: 8664873

Claim:
An operating circuit for at least one LED, to which is supplied direct current voltage or rectified direct current voltage, and which provides by a coil (L 1 ) and a switch (S 1 ), which is clocked by a control/regulation unit (SR), an operating voltage for the at least one LED, wherein energy is temporarily stored in the coil (L 1 ) when the switch (S 1 ) is switched on, which is discharged through the at least one LED when the switch is turned off, wherein a transformer is connected in series to the LED with a primary winding (T 1 ) and a secondary winding (T 2 ), and a measurement member (RM) is connected in series to the secondary winding (T 2 ), so that a circuit is formed, wherein the secondary winding (T 2 ) supplies a defined current and at least one measurement is performed on a secondary side.