| 摘要 |
PROBLEM TO BE SOLVED: To prevent flowing of excessive current into an input side circuit by connecting a diode in parallel to a series circuit of an inductor and transformer control coil provided for power-factor improvement, for suppressing differencial voltage which occurs when input voltage rises sharply. SOLUTION: A diode 14 is connected parallel to a series circuit of an inductor 6 and a control coil N3 of a transformer 7 provided for power-factor improvement, in the direction of charge of a smoothing capacitor 8. By this, when the voltage of an ac supply 1 rises sharply, the potential difference which occurs between the voltage after input rectification (A point) and the voltage of the smoothing capacitor 8 (B point) is made smaller rapidly. As a result, excessive current does not flow into a switch element 9, so that, breakage of the switch element 9 and occurrence of fault such as drop of output voltage due to over current detection are prevented. |
