| 摘要 |
PURPOSE:To reduce the cost by providing a potential detecting circuit for each phase and activating a conducting circuit, when the potential at a common joint drops below a predetermined level, thereby maintaining a constant potential. CONSTITUTION:A three-phase brushless motor drive circuit comprises an NPN power transistor(Tr) Q5, 6 for a motor drive and controls power supply to a motor coil 1 connected with a motor drive terminal W. When a negative counter-electromotive force is produced at the motor drive terminal W, base current is fed to the Tr Q6 in order to turn it ON, thus bringing the potential at the terminal W forcibly to GND potential. Tr Q11 has the base connected through resistors R3, 4 and a diode D2 with the Tr Q6 and the like. Furthermore, Tr Q12, 13 form a current mirror and disabled upon turning ON of the Tr Q11. By such arrangement, turning ON of parasitic Tr due to counter- electromotive force can be prevented without requiring an external diode. |
