In a caser where a first current is supplied to a first heater, a controller gradually increases the first current in a first period, supplies the first current based on a first duty cycle in a second period, and gradually reduces the first current to stop supplying the first current in a third period. In a case where a second current is supplied to a second heater, the controller gradually increases the second current in a fourth period, supply the second current based on a second duty cycle in a fifth period, and gradually reduces the second current to stop supplying the second current in a sixth period. The controller controls the supply of the second current such that part of the fourth period overlaps with the third period.

The invention relates to a method for controlling a lighting system, wherein the lighting system comprises a plurality of light-emitting ceiling tiles and a control unit for controlling the plurality of light-emitting tiles. The method comprises the step of controlling the plurality of light-emitting tiles to provide a predetermined luminance contrast in the ceiling. The method further comprises the step of, for the predetermined luminance contrast, controlling the plurality of light-emitting tiles to provide a substantially uniform light distribution incident on a target surface such as a horizontal work plane. The method enables the lighting conditions in a room to be adjusted for improving visual comfort and illumination without affecting the illumination at a task level.

A driving device provides output power to an illumination device including a plurality of filaments is provided. A first converting module converts input power into direct current (DC) power. The first converting module includes a pair of first input terminals receiving the input power and a pair of first output terminals coupled to a first node and a second node and outputting the DC power. A first capacitor is coupled between the first node and a third node. A second capacitor is coupled between the second and third nodes. The first clamping module is connected to a first specific capacitor in parallel. The first specific capacitor is the first capacitor or the second capacitor. A second converting module converts the DC power to generate the output power.