A driver circuit 10 is described for driving loads such as LED, OLED or LASER diode devices L. A switching converter 12 has a switching element M1 and reactive elements L1, C1 to provide an output switching voltage V1 by sequential switching operations of the switching element M1. The load L is connected to the output switching voltage. A linear current driver circuit 14 is connected in series to the load L and comprises an amplification element Q1 and a feedback circuit R1, 22 with a current control input VL, set, IB. In order to enable the circuit to be easily used, a control unit 16, 116, 216 is provided with a sensing input VL, 1, VL, 2 for a current or voltage at the linear current driver 14. A microcontroller 30, 130, 230 executes a control program for processing the sensing input and providing both a current control output VL, set, IB and a switching control output VL, set in accordance with a set current value Iset.