Power supply circuit and luminaire

摘要

According to one embodiment, there is provided a power supply circuit (134) including a rectifying circuit (22), a power-factor improving circuit (23), a bridge circuit (24), a transformer (25), a rectifying and smoothing circuit (26), first and second drivers (30, 31), a power supply section (81), and a control section (33). The rectifying circuit (22) converts an alternating-current input voltage into a rectified voltage. The power-factor improving circuit (23) improves a power factor of the rectified voltage and converts the rectified voltage into a direct-current voltage. The bridge circuit (24) converts, with a switching element (51, 52), the direct-current voltage into an alternating-current voltage. The transformer (25) includes a primary winding wire (55) and a secondary winding wire (56, 57). The rectifying and smoothing circuit (26) converts the alternating-current voltage output from the secondary winding wire (56, 57) into a direct-current output voltage and supplies the direct-current output voltage to a direct-current load (12). The first driver (31) controls the switching element (51, 52). The second driver (30) controls the power-factor improving circuit (23). The power supply section (81) converts the direct-current voltage into a driving voltage corresponding to the first and second drivers (30, 31). The control section (33) controls supply of the driving voltage to the first and second drivers (30, 31) and a stop of the supply of the driving voltage.