| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply device with a power factor improving circuit capable of detecting a point of time at which input current becomes zero due to an inexpensive and simple circuit configuration.SOLUTION: A power supply device 10 comprises: a first series circuit composed of a first rectifying element D1, a first switching element Q1, and a third rectifying element D3; a second series circuit composed of a second rectifying element D2, a second switching element Q2, and a fourth rectifying element D4; a reactor L1 connected between a connecting point of the first rectifying element D1 and the first switching element Q1 and a connecting point of the second rectifying element D2 and the second switching element Q2; an AC polarity detecting circuit 4 which detects a polarity of an AC power supply Vac; and a current detecting unit 5 which detects a reactor current. The current detecting unit 5 includes a transformer Tr in which the reactor L1 is a primary side, and controls the first switching element Q1 and the second switching element Q2 on the basis of reactor current detection signals Si1 and Si2 output from a secondary side of the transformer Tr to supply a desired DC voltage to a load circuit 2. |
