Power supply circuit and luminaire

摘要

There is provided a power supply circuit (14) including a power converting unit (20) configured to convert a conduction angle controlled alternating-current voltage supplied via a power supply path (25) and supply a direct-current voltage to a load (12), a control unit (21) configured to detect a conduction angle of the alternating-current voltage and control the conversion of the voltage according to the detected conduction angle, and a power supply unit for control (22) including a first branch path (40) electrically connected to the power supply path (25), a semiconductor element (51) configured to adjust an electric current flowing to the first branch path (40), a thermosensor (52, 55) configured to limit, if the temperature of the semiconductor element (51) is equal to or higher than an upper limit temperature, an electric current flowing to the semiconductor element (51). The power supply unit for control (22) converts the alternating-current voltage input via the first branch path (40) and supplies a direct-current voltage to the control unit (21).