| 摘要 |
PROBLEM TO BE SOLVED: To dispense with the alteration of the design of a power supply circuit and to facilitate ensurance of the lower limit of its regulation range and setting of a high power factor to it, by reducing its ripple voltage components. SOLUTION: An AC voltage is generated in a secondary winding N2 of a converter transformer CVT, by the switching operation of a current-resonance type converter for intermitting the charging current of a smoothing capacitor Ci in order to improve a power factor. This AC voltage is rectified and smoothed to give a DC voltage V3 in the output of a power-factor improving circuit 1. This DC voltage V3 is superimposed on the voltage across both terminals of the smoothing capacitor Ci to feed the obtained voltage to a switching power supply portion 2 as a rectified and smoothed voltage Ei. Thereby, the ripple level of the rectified and smoothed voltage Ei is made equal to the one of a power supply circuit obtained when the power-factor improving circuit 1 is omitted. |
