| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply device and a lighting device providing the same, capable of suppressing undesired rise or fluctuation of an output voltage in a case of a high input voltage or a light load condition at a step-up chopper circuit.SOLUTION: A step-up chopper circuit 16 includes a switching element Q1, and a driver 24 for switching the switching element Q1 according to increase or decrease of a current I flowing the switching element Q1. A current detection part 27 detects a current, proportioning to the current I flowing the switching element Q1 of the step-up chopper circuit 16, and provides the detected current to the driver 24. A microcomputer 33 outputs a signal if at least either a voltage, proportioning to an input voltage Vin of the step-up chopper circuit 16, is equal to a predetermined voltage or more, or a light control signal of the light source 12 is equal to a predetermined light control level or less. Superimpose means 31 superimposes an offset current to the current, detected by the current detection part 27 and provided to the driver 24, if the signal is outputted by the microcomputer 33.SELECTED DRAWING: Figure 1 |
