Drive circuit for brushless motor

Claim 2

A drive circuit arrangement for driving a brushless d-c motor, which comprises: first and second Hall generators each of which produces at least one control voltage in accordance with the intensity of a bias current flowing therethrough and the intensity of a magnetic field applied thereto, said first and second Hall generators being placed in the vicinity of the rotor of said motor and spaced from each other through a rectangular electric angle so that each of said Hall generators is subjected to an alternate magnetic field due to the revolution of said rotor; at least one first driver for supplying a field current to at least one first field coil in dependence on the control voltage signal from said first Hall generator; at least one second driver for supplying a field current to at least one second field coil in dependence on the control voltage signal from said second Hall generator; a first field current detector for producing a first feed-back signal representing the magnitude said field current through said first field coil; a second field current detector for producing a second feed-back signal representing the magnitude of said field current through said second field coil; a first bias current regulator for supplying to said second Hall generator a second bias current having a magnitude in dependence on said first feedback signal; a second bias current regulator for supplying to said first Hall generator a first bias current having a magnitude in dependence on said second feed-back signal; and a bias current limiter for limiting the total of said first and second bias currents below a current in dependence on the revolution speed of said rotor.

Claim 3

A drive circuit arrangement for driving a four-phase d-c brushless motor, which comprises: first and second Hall generators each of which produces a pair of control voltages inverse in phase to each other and of magnitudes in dependence on the intensity of a bias current flowing therethRough and the intensity of a magnetic field applied thereto, said first and second Hall generators being placed in the vicinity of the rotor and spaced from each other through a rectangular electric angle so that each of said Hall generators is subjected to an alternate magnetic field due to the revolution of said rotor; a first driver for supplying to the first phase field coil a first field current having a magnitude dependent on one of the control voltage from said first Hall generator; a second driver for supplying to the second phase field coil a second field current having a magnitude dependent on one of the control voltages from said second Hall generator; a third driver for supplying to the third phase field coil a third field current having a magnitude dependent on the other of the control voltages from said first Hall generator; a fourth driver for supplying to the fourth phase field coil a fourth field current having a magnitude dependent on the other of the control voltages from said second Hall generators; a first field current for producing a first feed-back signal representing the magnitudes of said first field and third field currents; a second field current detector for producing a second feed-back signal representing the magnitudes of said second and fourth field currents; a first bias current regulator for supplying to said second Hall generator a second bias current having a magnitude in dependence on said first feedback signal; a second bias current regulator for supplying to said first Hall generator a first bias current having a magnitude in dependence on said second feed-back signal; and a current limiter for limiting the total of said first and second bias current below a current in dependence on the revolution speed of said rotor.

Claim 4

A drive circuit arrangement for driving a four-phase d-c brushless motor, which comprises: first and second Hall generators each of which produces a pair of control voltages inverse in phase to each other and of magnitudes in dependence on the intensity of a bias current flowing therethRough and the intensity of a magnetic field applied thereto, said first and second Hall generators being placed in the vicinity of the rotor and spaced from each other through a rectangular electric angle so that each of said Hall generators is subjected to an alternate magnetic field due to the revolution of said rotor; a first driver for supplying to the first phase field coil a first field current having a magnitude dependent on one of the control voltage from said first Hall generator; a second driver for supplying to the second phase field coil a second field current having a magnitude dependent on one of the control voltages from said second Hall generator; a third driver for supplying to the third phase field coil a third field current having a magnitude dependent on the other of the control voltages from said first Hall generator; a fourth driver for supplying to the fourth phase field coil a fourth field current having a magnitude dependent on the other of the control voltages from said second Hall generators; a first field current for producing a first feed-back signal representing the magnitudes of said first field and third field currents; a second field current detector for producing a second feed-back signal representing the magnitudes of said second and fourth field currents; a first bias current regulator for supplying to said second Hall generator a second bias current having a magnitude in dependence on said first feedback signal; a second bias current regulator for supplying to said first Hall generator a first bias current having a magnitude in dependence on said second feed-back signal; and a current limiter for limiting the total of said first and second bias current below a current in dependence on the revolution speed of said rotor.

Claim 5

A drive circuit arrangement as claimed in claim 2, in which said first, second, third and fourth drivers respectively include first, second, third and fourth transistors the collectors of which are connected to said first, second, third and fourth field coils, respectively; said first field current detector includes a first resistor having one terminal connected to the emitters of said first and third transistors and the other terminal grounded, and a fifth transistor having the base thereof connected to said one terminal of the resistor and the emitter thereof grounded; and said second field current detector includes a second resistor having one terminal connected to the emitters of said second and fourth transistors and the other terminal grounded, and a sixth transistor having the base thereof connected to said one terminal of the second resistor and the emitter thereof grounded.

Claim 6

A drive circuit arrangement as claimed in claim 3, in which said first bias current regulators includes seventh transistor having the collector thereof connected to the bias terminal of said second Hall generator; said second bias current regulator includes a eighth transistor having the collector thereof connected to the bias terminal of said first Hall generator; and said current limiter includes a ninth transistor having the collector thereof connected to the emitters of said seventh and eighth transistors and the emitter thereof connected to a power source.