| 摘要 |
PURPOSE:To simplify the circuit,by using the energy of a capacitor, which is charged by division of a DC voltage, until the output of a coil for bias provided in the transformer of a switching power source becomes a value required for the controlling circuit. CONSTITUTION:Resistances 28 and 29 are connected between both terminals of a DC power source 27, and a capacitor 30 is connected between both terminals of the resistance 29 and is charged. The middle point of resistances 28 and 29 is connected to a controlling circuit 32 through a switch circuit 31 so that a bias power source 34 of a conversion transformer 33 becomes the bias of the controlling circuit 32. The voltage of the capacitor 30 rises to make the switch circuit 31 conductive, and the voltage charged in the capacitor 30 is applied as a bias voltage of the controlling circuit 32. The controlling circuit 32 starts the control and drives a switching transistor, which is not shown in figure, and raises the voltage of the bias power source 34; and when this voltage is raised sufficiently, the bias power source 34 replaces the capacitor 30. Thus, a stable operation is performed with a simple circuit. |
