A power supply device includes LED driver circuits electrically connected to LED light sources, respectively, and a control circuit. Each of the LED light sources includes light-emitting diodes electrically connected in series. The control circuit is configured, when current is prohibited from flowing through a target light source, to perform control of a target driver circuit so that a voltage lower than a threshold voltage at which current starts to flow through the target light source is applied across the target light source. The target light source is a part of the LED light sources. The target driver circuit includes an LED driver circuit, corresponding to the target light source, of the LED driver circuits.