| 摘要 |
PURPOSE:To obtain a miniaturized duty controller which has an extremely stable cycle of oscillations with a low cost by connecting a thyristor in parallel to a time constant circuit and at the same time actuating a comparator with voltage. CONSTITUTION:With connection of an AC power supply 1, the ripple voltage superposed by the ripple is producd at a capacitor 31 of a ripple voltage generating circuit 25. At the same time, a capacitor 28 of a time constant circuit is also changed. When this charging voltage is higher than the voltage at a point A by the base-emitter voltage VBE of a transistor (TR)18, the TR18 of a comparator 24 is turned on. Thus the electric charge of the capacitor 28 is discharged to the gate of a thyristor 3 from the TR18 via a resistance 17 as well as to the base of a TR17 via a resistance 22. Both the thyristor 3 and the TR17 are turned on. Then the capacitor 28 is discharged. When this voltage is less than the level equal to the value obtained by adding the VBE to the value obtained by dividing the ripple voltage by the compound resistance of resistances 19-21, the TR18 is turned off. Then both the thyristor 3 and the TR17 are also turned off, and the capacitor 28 is charged again. A series of these actions are repeated to control the duty of the load. |
