Drive circuit for brushless DC motor

摘要

To provide a brushless DC motor drive circuit operating with low electric power without a hall element, etc., and to provide a drive circuit for brushless DC motor which may be generally started regardless of an amount of load or size of inertia moment.;The drive circuit comprises a two-stage amplifying circuit comprised of transistors 13 and 14 for switching and amplifying a drive current to drive coils 11; a detecting coil 15 disposed together with the drive coils in a magnetic field of permanent magnets in a rotor, and connected to a base of the transistor 14 at one end; and a diode connected in series with the other end of the detecting coil 15 and provided between the base and an emitter of the transistor 14, wherein the diode controls and adjusts a base current of the transistor 14 such that the transistor 14 is turned on when induced electromotive force generated in the detecting coil 15 is a reverse voltage, and such that the transistor 14 is turned off when the induced electromotive force of the detecting coil 15 is a forward voltage.

主权项

1. A brushless DC motor drive circuit comprising:
a drive coil positioned in a magnetic field of permanent magnets provided in a rotor; a direct current power source supplying drive power to the drive coil; a first transistor that is emitter-grounded, in which a collector is connected to the drive coil; a second transistor that is emitter-grounded, in which a collector is connected to a base of the first transistor; a base current controlling resistor adjusting a base current of the second transistor; a detecting coil positioned in a magnetic field of the permanent magnets and provided between a base and an emitter of the second transistor; and a diode connected between the base and emitter of the second transistor in series with the detecting coil and provided in a forward direction running parallel to a current between the base and emitter of the second transistor, wherein the diode controls and adjusts the base current of the second transistor such that the second transistor is turned on when a reverse voltage is applied by induced electromotive force generated in the detecting coil and such that the second transistor is turned off when a forward voltage is applied by the induced electromotive force of the detecting coil.