| 摘要 |
PURPOSE:To suppress a current flowing in the DC motor, by clamping a conduction time of the control rectifying element circuit, to determine the maximum value of the conduction time. CONSTITUTION:A speed feed-back signal, fed to a clamp circuit 12, is applied to a resistor 13. A voltage drop of the resistor 13 operates a transistor 18, to feed a current to a condenser 21 from a synchronous power source, with counter electromotive force changing in a DC motor 4, and as the speed feed-back signal changes, a voltage across both ends of the resistor 13 changes to vary a collector current of the transistor 18, and a current, fed to the condenser 21, also changes. At this time, a current, actually charged to the condenser 21, is determined by a collector current of a transistor 22, consequently, a current, fed from the clamp circuit 12, becomes a maximum level of the current capable to be charged to the condenser 21. And if a level of current, charged to the condenser 21, incrases, a length of the conduction time of a control rectifying element circuit 2 is increased by a firing circuit 10, consequently, a maximum level of the current charged to the condenser 21 becomes for the maximum length of the conduction time of the control rectifying element circuit 2. |
