A method of operating a lighting device of a light for motor vehicles or similar, wherein the lighting device comprises: - two power supply lines (42,43) in which a primary supplying current flows; - at least two lighting branches, which are connected in parallel to one another and to said power supply lines (42,43) and each comprising one or more light sources in which a secondary supplying current (I2i) flows; said at least two lighting branches are connected to the power supply lines (42,43) by means of first and second common nodes set to first and second predetermined voltages; said lighting device comprises electronic control means provided with main switch means connected between one of said first or second common node and one of said power supply lines; current limiting means, which are connected in parallel to said first switch means and are configured to limit the primary supplying current to said predetermined minimum value (I1M); said method comprising the step of making said light sources simultaneously transit from a pre-lighting state, in which a second predetermined minimum secondary current (I2Mi) flows in the light sources of each lighting branch, to a complete lighting state, in which a nominal secondary current (I2Ni) higher than said predetermined minimum secondary current (I2Mi) flows in the light sources of each said lighting branch; said method being characterized in that it comprises the steps of: - determining the secondary current (I2i) circulating in each said lighting branch; - limiting by said current limiting means said primary supplying current to a predetermined minimum value (I1M) when the secondary current (I2i) flowing in at least one of said lighting branches is lower than a predetermined current threshold (Si); - controlling by said main switch means, the simultaneous transition of said light emitting sources from said pre-lighting state to said lighting state when each of the secondary currents (I2i) flowing in said lighting branches is either higher than or equal to said predetermined current threshold (Si) - two power supply lines (42,43) in which a primary supplying current flows; - at least two lighting branches, which are connected in parallel to one another and to said power supply lines (42,43) and each comprising one or more light sources in which a secondary supplying current (I2i) flows; said at least two lighting branches are connected to the power supply lines (42,43) by means of first and second common nodes set to first and second predetermined voltages; said lighting device comprises electronic control means provided with main switch means connected between one of said first or second common node and one of said power supply lines; current limiting means, which are connected in parallel to said first switch means and are configured to limit the primary supplying current to said predetermined minimum value (I1M); said method comprising the step of making said light sources simultaneously transit from a pre-lighting state, in which a second predetermined minimum secondary current (I2Mi) flows in the light sources of each lighting branch, to a complete lighting state, in which a nominal secondary current (I2Ni) higher than said predetermined minimum secondary current (I2Mi) flows in the light sources of each said lighting branch; said method being characterized in that it comprises the steps of: - determining the secondary current (I2i) circulating in each said lighting branch; - limiting by said current limiting means said primary supplying current to a predetermined minimum value (I1M) when the secondary current (I2i) flowing in at least one of said lighting branches is lower than a predetermined current threshold (Si); - controlling by said main switch means, the simultaneous transition of said light emitting sources from said pre-lighting state to said lighting state when each of the secondary currents (I2i) flowing in said lighting branches is either higher than or equal to said predetermined current threshold (Si)