Driver circuit for powering a plurality of light sources with an overall power supply electric current, wherein the plurality of light sources is arranged in a plurality of lighting branches connected in parallel with each other, where each lighting branch comprises light sources of the plurality of light sources connected in series to each other, comprising: - switching means configured to switch the path of the overall power supply electric current between at least one first path, corresponding to a first circuit configuration of the interconnections between the light sources, and at least one second path, corresponding to a second circuit configuration of the interconnections between the light sources, wherein said first and second circuit configurations have a different number of lighting branches; - at least one lighting switch connected in cascade to at least one respective lighting branch and configured to impose a branch current (ILED) through said at least one respective lighting branch required by the light sources to provide the desired luminosity, the branch current depending on a driver voltage (Vref) applied to said at least one lighting switch; - driver voltage regulation means, configured to regulate the driver voltage value according to the first or second circuit configuration of the plurality of lighting branches so as to maintain the branch current (ILED) unchanged as said circuit configuration varies; and - control means configured to command the switching means and the driver voltage regulation means to pass from the first circuit configuration being a parallel configuration of the light sources of a lighting branch with the light sources of the other lighting branches of the plurality of lighting branches, to the second circuit configuration, being a series configuration of the light sources of a lighting branch with the light sources of the other lighting branches of the plurality of lighting branches, and vice versa, the driver circuit being characterised in that the control means are further configured to: - detect the voltage drop at the terminals of the at least one lighting switch and to command the switching means and the driver voltage regulation means to pass from the second circuit configuration to the first circuit configuration when said voltage drop falls below a predefined threshold value, - compare the voltage drop at the terminals of the at least one lighting switch connected in cascade to the at least one respective lighting branch with the voltage drop at the ends of said at least one respective lighting branch and to command the switching means and the driver voltage regulation means to pass from the first circuit configuration to the second circuit configuration, depending on such comparison. - switching means configured to switch the path of the overall power supply electric current between at least one first path, corresponding to a first circuit configuration of the interconnections between the light sources, and at least one second path, corresponding to a second circuit configuration of the interconnections between the light sources, wherein said first and second circuit configurations have a different number of lighting branches; - at least one lighting switch connected in cascade to at least one respective lighting branch and configured to impose a branch current (ILED) through said at least one respective lighting branch required by the light sources to provide the desired luminosity, the branch current depending on a driver voltage (Vref) applied to said at least one lighting switch; - driver voltage regulation means, configured to regulate the driver voltage value according to the first or second circuit configuration of the plurality of lighting branches so as to maintain the branch current (ILED) unchanged as said circuit configuration varies; and - control means configured to command the switching means and the driver voltage regulation means to pass from the first circuit configuration being a parallel configuration of the light sources of a lighting branch with the light sources of the other lighting branches of the plurality of lighting branches, to the second circuit configuration, being a series configuration of the light sources of a lighting branch with the light sources of the other lighting branches of the plurality of lighting branches, and vice versa, the driver circuit being characterised in that the control means are further configured to: - detect the voltage drop at the terminals of the at least one lighting switch and to command the switching means and the driver voltage regulation means to pass from the second circuit configuration to the first circuit configuration when said voltage drop falls below a predefined threshold value, - compare the voltage drop at the terminals of the at least one lighting switch connected in cascade to the at least one respective lighting branch with the voltage drop at the ends of said at least one respective lighting branch and to command the switching means and the driver voltage regulation means to pass from the first circuit configuration to the second circuit configuration, depending on such comparison.