| 摘要 |
PROBLEM TO BE SOLVED: To obtain a switching power supply device having a high power factor with a simple circuit construction by a method, wherein the output side of a rectifier is connected to the primary winding of a transformer via an inductive element and a capacitive element, and a switching device is connected between the junction point of the inductance element and the capacitance element and the ground. SOLUTION: The output side of a rectifier 10 which rectifies an AC power supply AC is connected to the primary winding n1 of a transformer 15, via a choke coil 9 and a capacitor 13, which are connected in series to each other. Further, a switching transistor 11 is connected between the junction point of the choke coil 9, the capacitor 13 and the ground. The inductance of the choke coil 9 is selected properly, so as to make a current applied to the choke coil 9 constant, regardless of the turning-on and turning-off of the switching transistor 11 which are repeated at high frequency. With this constitution, a power factor can be improved, harmonic currents can be reduce, and efficiency can be improved. |
