| 摘要 |
PROBLEM TO BE SOLVED: To implement efficiency improvement, noise reduction and reduction of cost by implementing a soft switching operation regarding an insulated converter circuit.SOLUTION: A switching power supply is formed from a synchronous rectification step-down chopper circuit including a main switching element 14, a commutation element 16, a choke coil 18 and a buffer capacitor 20 as a primary side. As a secondary side, a serial circuit of a rectification element 26 and an output capacitor 24 is connected to a primary coil 22 that is provided in the choke coil 18. The inductance of the choke coil 18 is set at such a predetermined value that, when an output current is equal to or less than a maximum output current, within one cycle of switching, a choke coil current IL that flows in the choke coil 18 flows in both positive and negative directions over zero. A switching control circuit 30 performs soft switching on the main switching element 14 and the commutation element 16 in the switching cycle through complementary ON/OFF control while providing a dead time.SELECTED DRAWING: Figure 1 |
