Patent ID: 8860340

Claim:
A driving device for a multi-phase sensorless fan motor having a plurality of coils, comprising: a plurality of comparators, disposed for each of the coils, respectively, and configured to generate a back electromotive force sensing signal denoting a comparison result by comparing a back electromotive force appearing at one end of each corresponding coil with a neutral-point voltage of the coils; a forward/reverse rotation control portion, which receives a direction control signal used to assign a rotation direction of the fan motor in the normal operation to a first direction or a second direction opposite to the first direction, and outputs a signal to switch the rotation direction of the fan motor according to the direction control signal; a driving signal synthesis circuit, configured to generate a driving control signal used to drive the fan motor according to an output signal of the comparators and the output signal of the forward/reverse rotation control portion; and a driving circuit, for driving the fan motor according to the driving control signal, wherein the driving signal synthesis circuit comprises: a first control pattern generation portion, for outputting a first control pattern used to enable the fan motor to rotate toward the first direction; and a second control pattern generation portion, for outputting a second control pattern used to enable the fan motor to rotate toward the second direction; and wherein the driving signal synthesis circuit is structured to perform: (i) generating the driving control signal according to either the first control pattern or the second control pattern for enabling the fan motor to rotate toward a direction opposite to the rotation direction assigned by the direction control signal within a specific reverse rotation period after a driving of the fan motor is started, (ii) generating the driving control signal for applying a brake to the fan motor within a braking period, and (iii) generating the driving control signal according to either the first control pattern or the second control pattern for enabling the fan motor to rotate toward a direction of normal operation in a normal driving period.