| 摘要 |
PURPOSE:To provide a switching power supply that offers favorable power factor, has input characteristics with less input current higher harmonic components, and is further highly efficient. CONSTITUTION:The positive output terminal of a full-wave rectifying circuit 3, the primary winding 81 of a transformer 8, a switching element 9, a choke coil 5 and the negative output terminal of the full-wave rectifying circuit 3, are connected in series in this order. A smoothing capacitor 4 is connected in parallel with the series circuit composed of the primary winding 81 and the switching element 9. A first diode 61 and a second diode 62 are placed between the respective input terminals of the full-wave rectifying circuit 3 and the connecting point between the primary winding 81 and the switching element 9. A rectifying and smoothing circuit 20 is connected with the secondary winding 82 of the transformer 8. A control circuit 40 is included which controls the on-off ratio of the switching element 9 so that the d.c. output voltage fed to a load 25 will be stabilized. This obtains a switching power supply that offers favorable power factor and has input characteristics with less input current higher harmonic components. In addition this reduces the number of the components placed in the route of current of the choke coil 5 and thus conduction loss. |
