| 摘要 |
PROBLEM TO BE SOLVED: To suppress harmonics and to suppress the inrush current to a smoothing capacitor when a power supply is turned on by providing a circuit, which rectifies and smoothes the voltage appearing across the secondary winding of a flyback transformer, and a control circuit, which performs the switching of a switch element based on the DC voltage obtained is this way. SOLUTION: When an AC power supply 101 is turned on in a state that a switch element 104 is turned off, a timer 114 is started. Then, the current flows through the path comprising an inductor 103→capacitor 106→the primary winding of a flyback transformer 107→resistor 109, and the capacitor 106 is charged. This charging is performed with the time constant of the capacitance of the capacitor 106 and the resistance value of the resistor 109 approximately because the inductances of the inductor 103 and the primary winding of the flyback transformer 0 107 are small. When the timer 114 becomes time-up, the switching of the switch element 104 is started by a control circuit 113. Thus, the inrush current when the power supply is turned on is suppressed.
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