| 摘要 |
PURPOSE:To prevent the overcurrent flowed to the first and second transistors by connecting a unidirectional element reversely to the third and fourth transistors of a normal/reverse rotation drive circuit connected with transistors in a bridge. CONSTITUTION:Power transistors Q1-Q4 are connected in a bridge, a DC servo motor M is connected between the connecting point of the Q1, Q3 and the connecting point of the Q2, Q4 to form normal/reverse rotary drive circuit, the Q1, Q3 are turned ON at the normal rotation time, and the Q2, Q4 are turned ON at the revese rotation time. At this time, diodes D5, D6 of unidirectional elements are respectively connected to the Q3, Q4 reversely as seen from the Q3, Q4, thereby preventing the overcurrent flowed to the Q1 or Q2 due to the kick voltage produced at the coil of a DC servo motor M at the switching time of the rotation in an ultrafine time. Accordingly, the damage of the transistors due to the temperature rise caused by the repetitive use can be prevented, and an erroneous operation can be eliminated. |
