| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply device which, when supplied power increases or decreases, can prevent the drive cycle of a switching element from exceeding an upper limit value, as well as provide a luminaire and a lighting fixture using the power supply device.SOLUTION: The power supply device comprises a DC power supply section 2 which outputs a DC voltage Vo1, a voltage conversion section 3 which supplies DC power Vo2 to a load section 6 as a switching element Q1 is turned on or off, a resistor R1, a control section 4 which turns the switching element Q1 on or off, and an auxiliary winding L11. The control section 4 includes: an arithmetic unit 90 which calculates a drive cycle T of the switching element Q1; a count unit 8 which compares the result of calculation by the arithmetic unit 90 and an upper limit value Tmax of the drive cycle T; and a flip-flop 91 which, when the result of calculation by the arithmetic unit 90 is shorter than the upper limit value Tmax, sets the drive cycle T to the result of calculation by the arithmetic unit 90 and, when the result of calculation by the arithmetic unit 90 is longer than the upper limit value Tmax, sets the drive cycle T to the upper limit value Tmax. |
