Operating device for lighting means, - the operating device comprises - a switched resonant converter comprising at least two switches (3a, 3b), and - a control unit configured to control the switching operation of the at least two switches (3a, 3b) by modulating a high frequency operation with low frequency PWM pulses with a varying frequency (Fpwm); wherein - the control unit is configured to adjust an electrical power transferred by the switched resonant converter in a power range, the power range comprising at least a first power subrange and a second power subrange adjacent to the first power subrange; wherein - the control unit is configured to decrease the electrical power transferred in the first power subrange by increasing the off-time duration (TOFF) between two PWM pulses, while the on-time duration of the PWM pulses is kept constant; - the control unit is configured to increase the electrical power transferred in the second power subrange by increasing the on-time duration of the PWM pulses, while the off-time duration (TOFF) between two PWM pulses is kept constant; and - the control unit is configured to keep the on-time duration of the PWM pulses constant at a minimum on-time duration (TONMIN) in the first power subrange, and to keep the off-time duration (TOFF) between two PWM pulses constant at a minimum off-time duration (TOFFMIN) in the second power subrange; wherein the minimum on-time duration (TONMIN) equals to the minimum off-time duration (TOFFMIN). - the operating device comprises - a switched resonant converter comprising at least two switches (3a, 3b), and - a control unit configured to control the switching operation of the at least two switches (3a, 3b) by modulating a high frequency operation with low frequency PWM pulses with a varying frequency (Fpwm); wherein - a switched resonant converter comprising at least two switches (3a, 3b), and - a control unit configured to control the switching operation of the at least two switches (3a, 3b) by modulating a high frequency operation with low frequency PWM pulses with a varying frequency (Fpwm); wherein - the control unit is configured to adjust an electrical power transferred by the switched resonant converter in a power range, the power range comprising at least a first power subrange and a second power subrange adjacent to the first power subrange; wherein - the control unit is configured to decrease the electrical power transferred in the first power subrange by increasing the off-time duration (TOFF) between two PWM pulses, while the on-time duration of the PWM pulses is kept constant; - the control unit is configured to increase the electrical power transferred in the second power subrange by increasing the on-time duration of the PWM pulses, while the off-time duration (TOFF) between two PWM pulses is kept constant; and - the control unit is configured to keep the on-time duration of the PWM pulses constant at a minimum on-time duration (TONMIN) in the first power subrange, and to keep the off-time duration (TOFF) between two PWM pulses constant at a minimum off-time duration (TOFFMIN) in the second power subrange; wherein the minimum on-time duration (TONMIN) equals to the minimum off-time duration (TOFFMIN).