Abstract: Provided is a light source device in which the housing is not full of heat, and the risk of inhaling dust in the housing or the risk of reduction of life of the fan device becomes reduced. In an aspect, a light source device according to the present disclosure includes a light source; a light source control unit for controlling turning on/off and a quantity of light of the light source; a cooling fan for cooling the light source; and a fan control unit for controlling a number of revolutions of the cooling fan, wherein the fan control unit is configured to: control the number of revolutions of the cooling fan to become a first number of revolutions depending on the quantity of light of the light source when the light source is turned on, and control the number of revolutions of the cooling fan to become a second number of revolutions lower than the first number of revolutions by waiting for a predetermined waiting time when the light source is turned off.

Abstract: Provided is a light source device in which the housing is not full of heat, and the risk of inhaling dust in the housing or the risk of reduction of life of the fan device becomes reduced. In an aspect, a light source device according to the present disclosure includes a light source; a light source control unit for controlling turning on/off and a quantity of light of the light source; a cooling fan for cooling the light source; and a fan control unit for controlling a number of revolutions of the cooling fan, wherein the fan control unit is configured to: control the number of revolutions of the cooling fan to become a first number of revolutions depending on the quantity of light of the light source when the light source is turned on, and control the number of revolutions of the cooling fan to become a second number of revolutions lower than the first number of revolutions by waiting for a predetermined waiting time when the light source is turned off.

Abstract: Provided is a switching power supply device having a very small switching loss, which includes a rectifier circuit for rectifying a commercial AC voltage, a full-bridge circuit having first to fourth switching element, a transformer having a single primary coil and an N number of secondary coils, an N number of rectifying and smoothing circuits, an output detecting circuit for detecting at least one of voltage and current output from each rectifying and smoothing circuit, and a control circuit. Each rectifying and smoothing circuit includes a rectifying unit, a secondary switching element for controlling an output of the rectified voltage, and a smoothing unit for smoothing the rectified voltage, and the control circuit turns on each secondary switching element during a predetermined time.

Abstract: Provided is a switching power supply device having a very small switching loss, which includes a rectifier circuit for rectifying a commercial AC voltage, a full-bridge circuit having first to fourth switching element, a transformer having a single primary coil and an N number of secondary coils, an N number of rectifying and smoothing circuits, an output detecting circuit for detecting at least one of voltage and current output from each rectifying and smoothing circuit, and a control circuit. Each rectifying and smoothing circuit includes a rectifying unit, a secondary switching element for controlling an output of the rectified voltage, and a smoothing unit for smoothing the rectified voltage, and the control circuit turns on each secondary switching element during a predetermined time.