Lighting device, illumination device, illumination apparatus and illumination system

A lighting device for lighting a plurality of light source modules based on a setting signal of a conduction angle inputted from a setting unit, the setting unit outputting the setting signal generated by adjusting the conduction angle of an AC voltage inputted from an AC power source, the lighting device comprising:

• an AC to DC conversion unit configured to receive the setting signal and convert the setting signal into a DC voltage having a predetermined voltage value by rectifying and smoothing the setting signal;
• voltage conversion units configured to convert a voltage level of the DC voltage outputted from the AC to DC conversion unit and drive the light source modules according to drive signals;
• a PWM signal generating unit configured to receive the setting signal and generate a PWM signal having a duty ratio corresponding to a magnitude of the conduction angle of the setting signal;
• and
• a control unit configured to output the drive signals to the voltage conversion units based on a command value determined according to the duty ratio of the PWM signal,
• wherein the light source modules have solid-state light emitting elements different in emission color from each other, and include a first light source module having a relatively low color temperature and a second light source module having a relatively high color temperature, and
• wherein the control unit controls output powers of the voltage conversion units such that an output curve of a current flowing through the first light source module has the maximum or an inflection point, and a current flowing through the second light source module gradually increases as the conduction angle increases, between an upper limit and a lower limit of an adjustment range of the conduction angle.