Driving apparatus for sensorless fan motor

A driving apparatus for a sensorless fan motor comprising a plurality of coils, the driving apparatus comprising:

• a back electromotive force detection circuit configured to compare a voltage that occurs at one end of at least one from among the plurality of coils of the fan motor with a common voltage that occurs at a common connection node at which the plurality of coils are connected together, and to generate, based on a comparison result, a detection signal which is asserted in a cyclic manner when the fan motor is stably rotating;
• a driving signal synthesizing circuit configured to generate, in synchronization with the detection signal, a driving control signal which instructs conduction states of the plurality of coils;
• a driving circuit configured to apply a driving voltage to each of the plurality of coils according to the driving control signal;
• and
• a lock protection circuit configured to detect a lock state of a rotor of the fan motor,
• wherein the lock protection circuit comprises:
• a period detection unit configured to measure a period of the detection signal;
• a synchronization pulse generating circuit configured to generate a synchronization pulse having a period that is 1/N (N represents an integer of 2 or more) of the period of the detection signal measured in a previous cycle;
• and
• a lock judgment circuit configured to count the synchronization pulse in increments of cycles of the detection signal, and to assert a lock mode judgment signal when the count value exceeds a predetermined threshold value M (M represents an integer of 2 or more) which is greater than the aforementioned number N.