SWITCHING POWER SUPPLY DEVICE AND ILLUMINATING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a switching power supply device which can reduce electromagnetic emission noise.SOLUTION: A switching power supply device comprises a DC power supply 2 and a chopper circuit 3 for converting an output voltage of the DC power supply. The chopper circuit 3 includes: a first inductor 18; a second inductor 19 magnetically coupled with the first inductor 18; a third inductor 20 connected to the first inductor 18; a current control element 13 serially connected with a switching element 12 which flows an increased current from the DC power supply to the first inductor 18 and to the third inductor 20 when turned on; a rectifier element 14 for flowing a decreased current to the first inductor 18 and the third inductor 20 when turned off; and a drive circuit for turning off the switching element by controlling a gate voltage of the switching element when the current control element reaches saturation by the increased current when turned on. The third inductor 20 includes the even number of fourth inductors 21, 22 which have equivalent inductance with each other and are arranged in a manner such that generating magnetic fluxes flow in directions opposite to each other.