Driver circuit for operating an illuminant, preferably at least one LED, comprising: • an electrically isolated LLC converter which is clocked on the primary side by a control unit (SE") of the driver circuit by means of a controlled half-bridge switch unit with downstream series resonant circuit (C1, L1) and feeds a rectifier (D1, D2) of the driver circuit on a secondary side of the converter from which the illuminant can be supplied, • wherein the converter has a first transformer with two windings (L2-2, L2-3) with central tapping on the secondary side, • wherein the rectifier has two diodes (D1, D2) which are each connected in series to one of the two windings of the first transformer, • a detection circuit (E") of the driver circuit for indirectly detecting the current on the secondary side of the converter, • wherein on the secondary side of the first transformer of the converter in each case one primary winding (L3_1, L3_2) of a second transformer (L3_1, L3_3) of the driver circuit is arranged in series with in each case one of the two diodes (D1, D2), • wherein the detection circuit (E") has a detection rectifier arranged on the primary side of the converter, and a secondary winding (L3_3) of the second transformer (L3_1, L3_3) is part of a first and a second diagonal of the detection rectifier (AG'), • wherein the first and second diagonals each have two rectifier switches (Q3, Q4, Q5, Q6), • wherein a parameter representing the current through the illuminant is fed back to the control unit (SE") from an output of the detection circuit (E"), and the output is connected directly or indirectly to a measurement input of the control unit (SE"), • wherein on the basis of the parameter representing the current through the illuminant, the control unit (SE") activates and deactivates the first diagonal of the rectifier (AG') synchronously with a first inverter switch of the half-bridge switch unit by using the control signal of said first inverter switch and wherein the control unit (SE") activates and deactivates the second diagonal of the rectifier (AG") synchronously with a second inverter switch of the half-bridge switch unit by using the control signal of said second inverter switch, and wherein only the first or the second diagonal is active in each case, and • an integration circuit to which the current is supplied through the respectively activated diagonal of the rectifier (AG') and which integrates this current. • an electrically isolated LLC converter which is clocked on the primary side by a control unit (SE") of the driver circuit by means of a controlled half-bridge switch unit with downstream series resonant circuit (C1, L1) and feeds a rectifier (D1, D2) of the driver circuit on a secondary side of the converter from which the illuminant can be supplied, • wherein the converter has a first transformer with two windings (L2-2, L2-3) with central tapping on the secondary side, • wherein the rectifier has two diodes (D1, D2) which are each connected in series to one of the two windings of the first transformer, • a detection circuit (E") of the driver circuit for indirectly detecting the current on the secondary side of the converter, • wherein on the secondary side of the first transformer of the converter in each case one primary winding (L3_1, L3_2) of a second transformer (L3_1, L3_3) of the driver circuit is arranged in series with in each case one of the two diodes (D1, D2), • wherein the detection circuit (E") has a detection rectifier arranged on the primary side of the converter, and a secondary winding (L3_3) of the second transformer (L3_1, L3_3) is part of a first and a second diagonal of the detection rectifier (AG'), • wherein the first and second diagonals each have two rectifier switches (Q3, Q4, Q5, Q6), • wherein a parameter representing the current through the illuminant is fed back to the control unit (SE") from an output of the detection circuit (E"), and the output is connected directly or indirectly to a measurement input of the control unit (SE"), • wherein on the basis of the parameter representing the current through the illuminant, the control unit (SE") activates and deactivates the first diagonal of the rectifier (AG') synchronously with a first inverter switch of the half-bridge switch unit by using the control signal of said first inverter switch and wherein the control unit (SE") activates and deactivates the second diagonal of the rectifier (AG") synchronously with a second inverter switch of the half-bridge switch unit by using the control signal of said second inverter switch, and wherein only the first or the second diagonal is active in each case, and • an integration circuit to which the current is supplied through the respectively activated diagonal of the rectifier (AG') and which integrates this current.