| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply device that suppresses the width of a pulse when a switching element is turned on and under a light load or a middle load, and suppresses an increase in ripple voltage that is generated due to a variation in load current.SOLUTION: There is provided a power supply device comprising: a transformer 104; an FET 105 for performing a switching operation of turning on or off a current flowing on a primary side of the transformer 104; a photocoupler 109 that feeds back a feedback voltage according to a voltage output from a secondary side of the transformer 104 to the primary side of the transformer 104; and a pulse width limitation part 305 that limits the on-width of a pulse signal turing on the FET 105 on the basis of the feedback voltage fed back by the photocoupler 109, the power supply device including a pulse width limitation inhibition time creation part 305e that, when the power supply device has made a transition from a first state where the on-width is limited by the pulse width limitation part 305 to a second state where the limitation of the on-width is released, controls to maintain the second state for a first time.SELECTED DRAWING: Figure 1 |
