| 摘要 |
PROBLEM TO BE SOLVED: To achieve highly efficient operation in an entire range from a light load up to a rated load, in a switching power supply. SOLUTION: A DC input switching element (SW3), which is connected in series to the primary winding of a first transformer (T1), is provided at the primary circuit side. At the secondary circuit side are provided a first gate drive circuit (11) inserted on load connection lines between the secondary winding of the first transformer (T1) and a load (16) to control a main switching element (SW1); a first gate drive circuit (12) that controls a sub-switching element (SW2) connected between the load connection lines; a second transformer (T2) between which and one of the load connection lines the primary winding is inserted; a control circuit (14) that generates and outputs control pulses on the basis of an output voltage supplied to the load (16); and a third transformer (T3) that controls the DC input switching element (SW3) on the basis of this control pulses. COPYRIGHT: (C)2006,JPO&NCIPI
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