Light modulation controller, lighting system, and equipment instrument

A lighting system comprising:

• a light modulation controller;
• and
• a light source unit,
• wherein the light modulation controller, comprising:
• a switching element configured to be electrically connected between the light source unit and a DC power supply that is configured to output a DC voltage having a voltage value capable of causing a semiconductor light-emitting element included in the light source unit to emit light;
• and
• a control circuit configured to control a switching operation of the switching element,
• the control circuit being configured to convert the DC voltage that is outputted from the DC power supply to a square wave voltage by switching the switching element according to a PWM signal having a duty ratio that corresponds to a light modulation level of the light source unit, and cause the square wave voltage to be outputted to the light source unit,
• the control circuit including a voltage controller configured to control an operating voltage, derived in relation to the PWM signal, for operating the switching element such that at least one of a rising time and a falling time of a current that flows through the switching element is 1 microsecond or more.