| 摘要 |
PURPOSE:To reduce power losses by providing additionally the second DC winding, whose number of turns is larger than that of the first DC winding, in a current detecting circuit and controlling a current so that ampere-turns of the first and the second DC windings are preliminarily determined values. CONSTITUTION:A current I1 transmitted from a constant current source 3 is shout into a current I2 flowed to a resistance Rp for sharing a load and a current IL flowed toward a load through the first DC winding WD1. A current I3 flowed aside to the second DC winding WD2 is equal to the current I2 if a voltage Vz between both ends of a Zener diode ZD is lower than a Zener voltage VB; and if the voltage Vz reaches the voltages VB, the current I3 becomes a certain value equal to VB/Rs because the winding resistance of the winding WD2 is very low and is ignored. An output voltage Vd of a current detecting circuit 5 is proportional to the sum of ampere-turns of windings WD1 and WD2, and a control circuit 6 receives this output voltage Vd and sends a control signal of a voltage proportional to the difference between the voltage Vd and a preliminarily determined reference voltage VO to the constant current source 3, thus controlling the transmission current I1. |
