| 摘要 |
PROBLEM TO BE SOLVED: To form a power supply unit having high conversion efficiency by limiting current immediately after its start-up. SOLUTION: A series circuit consisting of a primary exciting winding 4a of a flyback transformer 4, a switching device 5, and current detecting resistor 6 is connected between a positive terminal 1 and a negative terminal 2 of a DC voltage power source. A connection between the primary exciting winding 4a and the switching element 5 is connected to the gate of the switching device 5. A connection between the switching element 5 and the resistor 6 is connected to a comparative input of a comparator 11 by an integrated circuit(IC), and a Zener diode 12 is connected to a reference input. The flyback transformer 4 involves a primary winding 4b formed so as to be the same polarity as that of the primary exciting winding 4a, that is, to become an on/on winding, and the primary winding 4b is connected to the gate of the switching device 5, and to the power source input of the comparator 11 through a rectifying/ smoothing circuit. The output of the comparator 11 is connected to the gate of the switching device 5.
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