Lighting device, illumination fixture, and illumination system

摘要

[Object] To enable measurement of input power without using a current transformer and obtain input power with sufficient accuracy even if there is a change in the ambient temperature of a light source load. [Means for Settlement] A detection resistor 45 is connected in series to a switching element 42 of a power conversion circuit 4 and detects a current flowing in the switching element 42. By using a power setting value outputted from a power setting part 81 so as to determine a size of power supplied to a discharge lamp 11 and a current detection value corresponding to an output of the detection resistor 45, a power calculation part 83 obtains input power through correction of a fluctuation of a current detection value caused by a change in the ambient temperature of the discharge lamp 11. Here, the power calculation part 83 calculates input power by using a power adjustment value corresponding to a difference between a power setting value and a current detection value, a maximum power value being a power setting value obtained when power is supplied to the discharge lamp 11 at the maximum, and a power setting value.