| 摘要 |
PROBLEM TO BE SOLVED: To realize soft switching operation of an insulation type converter circuit to be capable of being high performance, low noise, and low cost.SOLUTION: A switching power supply device constitutes as a primary side circuit a synchronous rectification step-up chopper circuit 10 by connecting a series circuit of a choke coil 18 and a main switching element 14 with an input power supply 12 in parallel and connecting a series circuit of a commutation element 16 and a buffer capacitor 20 with the switching element 14 in parallel, and connects as a secondary side circuit a series circuit of a rectifier 26 and an output capacitor 24 by installing a secondary coil 22 to the choke coil 18. Inductance of the choke coil 18 is set as a value in which current IL flowing in the choke coil 18 changes across the value zero to flow in both of a positive direction and a negative direction when it is peak output current or less in one cycle of switching. The switching control circuit 30 performs a soft switching by complementarily executing on-off control of the main switching element 14 and the commutation element 16 with a dead time in the switching cycle.SELECTED DRAWING: Figure 1 |
