| 摘要 |
A switching power supply includes a rectifier circuit (4 or 4a), a transformer (5 and 5a-5e), a rectifying and smoothing circuit (6), a smoothing capacitor (C1), an inductor (L1), a primary switch (Q1), and a soft-switching capacitor (Cq1) connected in parallel with the primary switch. <??>For improvements in power factor and input waveform, a soft-switching circuit (7) is provided which comprises an ancillary switch (Q2) connected in series with a tertiary winding (N3) of the transformer, and current supply means (Ca and Db with or without N4) connected to the transformer tertiary (N3) for supplying thereto a current of sufficient magnitude to cause the transformer primary (N1) to develop a voltage that enables the soft-switching capacitor (Cq1) to discharge. <IMAGE> |
