Abstract: A light output control device includes a switching device, multiple signal input ports, a signal selection circuit, and a control circuit. The switching device is to be electrically connected between a direct-current power supply and a light source circuit. The light source circuit includes a semiconductor light emitting element. The multiple signal input ports respectively correspond to multiple kinds of light output control signals. The signal selection circuit selects, when receiving two or more light output control signals indicating different light output levels through the multiple signal input ports, a light output control signal indicating a lowest (or highest) light output level, from the two or more light output control signals. The control circuit performs switching control of the switching device with a duty cycle corresponding to the lowest (or highest) light output level indicated by the light output control signal selected by the signal selecting circuit.

Abstract: A light source circuit includes light-emitting diodes and a constant current circuit that controls current flowing through light-emitting diodes to a fixed level. A DC power supply circuit outputs a DC voltage having a voltage value capable of causing light-emitting diodes to emit light. A light modulation control unit includes: a MOSFET electrically connected between DC power supply circuit and light source circuit; and a control circuit configured to control MOSFET. Control circuit is configured to turn MOSFET on and off with a duty ratio corresponding to a light modulation level such that DC voltage that is outputted from DC power supply circuit is converted to a square wave voltage, and the square wave voltage is outputted to light source circuit. The square wave voltage has an amplitude equal to the voltage value of the DC voltage that is outputted from DC power supply circuit.

Abstract: A light output control device includes a switching device, multiple signal input ports, a signal selection circuit, and a control circuit. The switching device is to be electrically connected between a direct-current power supply and a light source circuit. The light source circuit includes a semiconductor light emitting element. The multiple signal input ports respectively correspond to multiple kinds of light output control signals. The signal selection circuit selects, when receiving two or more light output control signals indicating different light output levels through the multiple signal input ports, a light output control signal indicating a lowest (or highest) light output level, from the two or more light output control signals. The control circuit performs switching control of the switching device with a duty cycle corresponding to the lowest (or highest) light output level indicated by the light output control signal selected by the signal selecting circuit.

Abstract: A light source circuit includes light-emitting diodes and a constant current circuit that controls current flowing through light-emitting diodes to a fixed level. A DC power supply circuit outputs a DC voltage having a voltage value capable of causing light-emitting diodes to emit light. A light modulation control unit includes: a MOSFET electrically connected between DC power supply circuit and light source circuit; and a control circuit configured to control MOSFET. Control circuit is configured to turn MOSFET on and off with a duty ratio corresponding to a light modulation level such that DC voltage that is outputted from DC power supply circuit is converted to a square wave voltage, and the square wave voltage is outputted to light source circuit. The square wave voltage has an amplitude equal to the voltage value of the DC voltage that is outputted from DC power supply circuit.