| 摘要 |
<p>PURPOSE:To prevent reduction of a holding current even though the voltage drops by providing both a power supply voltage dividing circuit, which divides a commercial power supply voltage, and a time-constant-circuit having a level limiting means on a time determining means, thereby making the holding current of an electromagnetic brake exciting coil constant. CONSTITUTION:A commercial power supply voltage is divided by resistances R9, R10 and inputted into an inversion terminal of a comparator OP2 via a resistance R11. A Zener diode D7 is provided to a time determining means. The Zener diode D7 places a limit upon a non-inversion-terminal-input-voltage of the comparator OP2, thereby keeping the voltage constant. By making voltage correction like this, both terminal voltages of an exciting coil BRK can be made almost equal to each other. When the voltage drops, since the non- inversion-terminal-input-voltage of the comparator OP2 drops, an 'on'-period of an output transistor Q1 is elongated, and consequently both terminal voltages of the exciting coil BRK are compensated.</p> |
